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Cited by 1,042Barrier Structure and Function StudiesTryptophan and brain disordersStress Responses and Cortisol

Social stress induces neurovascular pathology promoting depression

Open access
Menard, Caroline, Pfau, Madeline L., Hodes, Georgia E., Kana, Veronika, Wang, Victoria X., Bouchard, Sylvain, Takahashi, Aki, Flanigan, Meghan E. +15 more·2017·Nature Neuroscience
DOI 10.1038/s41593-017-0010-3PMC PMC5726568
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Abstract

Studies suggest that heightened peripheral inflammation contributes to the pathogenesis of major depressive disorder. We investigated the effect of chronic social defeat stress, a mouse model of depression, on blood–brain barrier (BBB) permeability and infiltration of peripheral immune signals. We found reduced expression of the endothelial cell tight junction protein claudin-5 (Cldn5) and abnormal blood vessel morphology in nucleus accumbens (NAc) of stress-susceptible but not resilient mice. CLDN5 expression was also decreased in NAc of depressed patients. Cldn5 downregulation was sufficient to induce depression-like behaviors following subthreshold social stress whereas chronic antidepressant treatment rescued Cldn5 loss and promoted resilience. Reduced BBB integrity in NAc of stress-susceptible or mice injected with adeno-associated virus expressing shRNA against Cldn5 caused infiltration of the peripheral cytokine interleukin-6 (IL-6) into brain parenchyma and subsequent expression of depression-like behaviors. These findings suggest that chronic social stress alters BBB integrity through loss of tight junction protein Cldn5, promoting peripheral IL-6 passage across the BBB and depression. Chronic social defeat stress induces loss of protein claudin-5, leading to abnormalities in blood vessel morphology, increased blood brain barrier permeability, infiltration of immune signals and depression-like behaviors.

AI snapshot

Written from the paper’s full text.

TL;DR

Chronic social defeat in mice reduces the endothelial tight-junction protein cldn5 in nucleus accumbens, compromises blood-brain barrier integrity, and allows circulating IL-6 to enter brain tissue, promoting depression-like behavior. Postmortem nucleus accumbens tissue from depressed patients also shows lower CLDN5 expression, linking stress-related neurovascular pathology to inflammation and depression.

Key findings

  • In nucleus accumbens of stress-susceptible but not resilient mice after 10-day chronic social defeat, cldn5 mRNA and protein were reduced; normalization to endothelial marker pecam1 indicated about 40% loss (*p = 0.0009), and cldn5 levels correlated with social avoidance (p = 0.0014). Electron microscopy showed discontinuous tight junctions in susceptible mice (*p < 0.0001).
  • Human postmortem nucleus accumbens CLDN5 mRNA was lower in major depressive disorder: Montreal non-medicated cases (*p = 0.0117) and Texas cases (*p = 0.0435); no significant changes were seen in hippocampus or prefrontal cortex, and cocaine users showed no change.
  • Viral cldn5 knockdown in nucleus accumbens combined with subthreshold microdefeat produced depression-like behaviors: less grooming (*p = 0.0356), lower sucrose preference (p = 0.0063), more forced-swim immobility (p = 0.0015), and lower social interaction ratio (*p = 0.0386); restoring cldn5 reversed anhedonia and promoted resilience.
  • Blood-brain barrier permeability increased in susceptible mice by Gd-DTPA MRI (nucleus accumbens *p = 0.0237; hippocampus p = 0.0085) and Evans blue in nucleus accumbens (p = 0.0014); IL-6 was elevated in nucleus accumbens (*p = 0.0321), biotinylated IL-6 entered nucleus accumbens parenchyma only in susceptible or cldn5-knockdown mice, and intra-nucleus accumbens IL-6 before subthreshold defeat caused social avoidance (*p = 0.0405).

Methods

  • Male C57BL/6J mice underwent 10-day chronic social defeat by CD-1 aggressors and were classified as stress-susceptible or resilient by social interaction ratio (<1 vs >1); additional experiments used microdefeat, chronic variable stress, imipramine, AAV-shRNA-cldn5, tracers, MRI, transmission electron microscopy, flow cytometry, and ELISA.
  • Molecular and histological work included qPCR for blood-brain barrier and cytokine genes, immunohistochemistry for cldn5/CD31, Western blot, capillary extraction, and human postmortem nucleus accumbens, hippocampus, and prefrontal cortex samples from McGill and University of Texas Southwestern cohorts.
  • Analyses used t-tests, one-way and two-way ANOVA with Bonferroni post hoc tests, and Pearson correlations, with significance set at p < 0.05; quantitative assays were performed in duplicate across two cohorts.

Limitations

  • The paper states that no compound currently exists to enhance Cldn5 expression, that peripheral ccr2+ monocytes were not detected infiltrating brain parenchyma unlike some prior reports, that local IL-6 production in nucleus accumbens could not be ruled out, and that human medication effects were partial or absent while most MDD subjects died by suicide.
  • Evident from the text: rodent experiments used male mice only, leaving sex differences untested; human evidence is postmortem mRNA and correlational, not direct measurement of blood-brain barrier permeability or IL-6 passage in patients; the causal chain is established mainly in mouse models.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41593-017-0010-3

Cites

53 of 53 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

36 of 43 cited sources checked · 19 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    Individual differences in the peripheral immune system and modulation of cytokine release, notably IL-6, are associated with susceptibility versus resilience to chronic social stress.

    “Individual differences in the peripheral immune system and modulation of cytokine release, notably interleukin-6 (IL-6), are associated with susceptibility versus resilience to chronic social stress11.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [11] Hodes, G. E. et al. Individual differences in the peripheral immune system promote resilience versus susceptibility to social stress. Proc. Natl. Acad. Sci. USA 111, 16136–16141 (2014). source
  • Premisecitation

    Six days of subchronic variable stress is insufficient to induce depression-like behaviors in male mice.

    “a protocol that is insufficient to induce depression-like behaviors in male mice31”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [31] Hodes, G. E. et al. Sex differences in nucleus accumbens transcriptome profiles associated with susceptibility versus resilience to subchronic variable stress. J. Neurosci. 35, 16362–16376 (2015). source
  • Premisecitation

    Heightened peripheral inflammation contributes to the pathogenesis of major depressive disorder.

    “Studies suggest that heightened peripheral inflammation contributes to the pathogenesis of major depressive disorder.”
    • Also stated in: § Introduction · plain
      “clinical studies report higher levels of circulating pro-inflammatory cytokines in MDD patients, a pattern that has been replicated in preclinical animal models of depression1, 7–10.”
    Quote in the paperSubstantial claim5 of 5 sources checked
    • cites [1] Ménard, C., Pfau, M. L., Hodes, G. E. & Russo, S. J. Immune and neuroendocrine mechanisms of stress vulnerability and resilience. Neuropsychopharmacology 42, 62–80 (2017). source
    • cites [7] Hodes, G. E., Kana, V., Menard, C., Merad, M. & Russo, S. J. Neuroimmune mechanisms of depression. Nat. Neurosci. 18, 1386–1393 (2015). source
    • cites [8] Barnes, J., Mondelli, V. & Pariante, C. M. Genetic contributions of inflammation to depression. Neuropsychopharmacology 42, 81–98 (2017). source
    • cites [9] Dantzer, R. Cytokine, sickness behavior, and depression. Immunol. Allergy Clin. North Am. 29, 247–264 (2009). source
    • cites [10] Miller, A. H. & Raison, C. L. The role of inflammation in depression: from evolutionary imperative to modern treatment target. Nat. Rev. Immunol. 16, 22–34 (2016). source
  • Premisecitation

    Chronic antidepressant treatment can reverse CSDS-induced depression-like behaviors, including social avoidance.

    “Chronic antidepressant treatment can reverse CSDS-induced depression-like behaviors, including social avoidance25, 32.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [25] Berton, O. & Nestler, E. J. New approaches to antidepressant drug discovery: beyond monoamines. Nat. Rev. Neurosci. 7, 137–151 (2006). source
    • cites [32] Golden, S. A. et al. Epigenetic regulation of RAC1 induces synaptic remodeling in stress disorders and depression. Nat. Med. 19, 337–344 (2013). source

      The Results section on stress-induced Rac1 regulation reports that 35 days of imipramine treatment partially reversed social avoidance in mice after chronic social defeat. It does not establish reversal of other depression-like behaviors by that treatment, and the claim omits the qualification that the observed reversal was partial. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
  • Premisecitation

    A 27-fold increase in circulating IL-6 level occurs 20-min after defeat in SS mice.

    “We previously reported a 27-fold increase in circulating IL-6 level 20-min after defeat in SS mice11.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [11] Hodes, G. E. et al. Individual differences in the peripheral immune system promote resilience versus susceptibility to social stress. Proc. Natl. Acad. Sci. USA 111, 16136–16141 (2014). source
  • May combine two claims. 28
  • Classified as probably not a substantial claim. 27
  • The quote only partly states this claim. 1

  • May combine two claims.

    Premisecitation

    Chronic stress mobilizes the innate immune system and stimulates enhanced proliferation and release of inflammatory monocytes and neutrophils into the bloodstream.

    “Chronic stress mobilizes the innate immune system and stimulates enhanced proliferation and release of inflammatory monocytes and neutrophils into the bloodstream12, 13.”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [12] Powell, N. D. et al. Social stress up-regulates inflammatory gene expression in the leukocyte transcriptome via β-adrenergic induction of myelopoiesis. Proc. Natl. Acad. Sci. USA 110, 16574–16579 (2013). source

      The Mouse Monocyte Subset Differentiation section (page not available) reports increased proinflammatory monocytes and granulocytes in the blood and bone marrow after repeated social defeat; the mouse myeloid-lineage analysis also reports increased progenitors of both types. The paper does not identify the granulocytes specifically as neutrophils or directly measure their release into the bloodstream, and its human analysis concerns monocytes rather than neutrophils. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
    • cites [13] Heidt, T. et al. Chronic variable stress activates hematopoietic stem cells. Nat. Med. 20, 754–758 (2014). source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Loss of Cldn5 promotes loosening of the BBB and increased permeability.

    “loss of Cldn5 has been shown to promote loosening of the BBB and increased permeability23.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [23] Nitta, T. et al. Size-selective loosening of the blood-brain barrier in claudin-5-deficient mice. J. Cell Biol. 161, 653–660 (2003). source

  • May combine two claims.

    Premisecitation

    Clinical studies report higher levels of circulating pro-inflammatory cytokines in MDD patients, a pattern replicated in preclinical animal models of depression.

    “clinical studies report higher levels of circulating pro-inflammatory cytokines in MDD patients, a pattern that has been replicated in preclinical animal models of depression1, 7–10.”
    Quote in the paperNot a substantial claim5 of 5 sources checked
    • cites [1] Ménard, C., Pfau, M. L., Hodes, G. E. & Russo, S. J. Immune and neuroendocrine mechanisms of stress vulnerability and resilience. Neuropsychopharmacology 42, 62–80 (2017). source
    • cites [7] Hodes, G. E., Kana, V., Menard, C., Merad, M. & Russo, S. J. Neuroimmune mechanisms of depression. Nat. Neurosci. 18, 1386–1393 (2015). source
    • cites [8] Barnes, J., Mondelli, V. & Pariante, C. M. Genetic contributions of inflammation to depression. Neuropsychopharmacology 42, 81–98 (2017). source

      The Introduction (page not provided) reports increased inflammatory cytokines in the peripheral blood of some patients with major depression, supporting the clinical portion. The Materials and methods section (page not provided) says papers concerning animal models were excluded, so this source does not support the claimed replication in preclinical animal models. (LLM, conf=0.90)

      Experimental — accuracy not yet measured
    • cites [9] Dantzer, R. Cytokine, sickness behavior, and depression. Immunol. Allergy Clin. North Am. 29, 247–264 (2009). source

      The Pathophysiologic implications section reports elevated circulating proinflammatory cytokines, particularly IL-6, in major depression. It also describes depressive-like behavior in mice subjected to inflammation, but does not say that elevated circulating cytokine levels in depressed patients were replicated in animal models. Page numbers were not available in our copy. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [10] Miller, A. H. & Raison, C. L. The role of inflammation in depression: from evolutionary imperative to modern treatment target. Nat. Rev. Immunol. 16, 22–34 (2016). source

      The “Inflammation and depression” section reports increased pro-inflammatory cytokine expression in patients with major depressive disorder and identifies peripheral-blood IL-1β, IL-6 and TNF as reliable inflammatory biomarkers. The “Risk and resilience” section describes mice whose blood leukocytes produced more IL-6 ex vivo and were more susceptible to stress-induced depressive-like behaviour, but it does not report that the mice had higher circulating cytokine levels. Thus, the claimed replication of the circulating-cytokine pattern in animal models is not established by this copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Cldn5 is an endothelial cell-specific tight junction protein and is enriched in blood vessels.

    “Cldn5 is an endothelial cell-specific tight junction protein (Supplementary Fig. 2D)29, 30, which we confirmed to be enriched in blood vessels using a brain capillary extraction method”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [29] Zhang, Y. et al. An RNA-sequencing transcriptome and splicing database of glia, neurons, and vascular cells of the cerebral cortex. J. Neurosci. 34, 11929–11947 (2014). source

      The section “RNA-Seq analysis identifies novel cell type-enriched genes” identifies Cldn5 as an endothelial-cell-specific marker, supporting that part of the cited description. The passages do not identify it as a tight junction protein. Enrichment in extracted blood vessels is presented in the citing sentence as the citing authors’ own confirmation, not a finding attributed to this source. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [30] Zhang, Y. et al. Purification and characterization of progenitor and mature human astrocytes reveals transcriptional and functional differences with mouse. Neuron 89, 37–53 (2016). source

      The Results section on purified human cell transcriptomes identifies CLDN5 as an endothelial cell-specific marker and reports selective expression in endothelial cells. Our copy does not identify CLDN5 as a tight junction protein. The blood-vessel enrichment is presented in the citing sentence as the citing authors’ own confirmation, not a finding attributed to this source. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    The NAc plays a crucial role in stress responses and mood disorders including MDD.

    “The NAc plays a crucial role in stress responses and mood disorders including MDD28.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [28] Russo, S. J. & Nestler, E. J. The brain reward circuitry in mood disorders. Nat. Rev. Neurosci. 14, 609–625 (2013). source

  • May combine two claims.

    Premisecitation

    The subthreshold micro-defeat protocol is insufficient to induce depression-like behaviors without pro-depressive manipulations and can be used to identify pro-susceptibility factors.

    “Without the introduction of pro-depressive manipulations, this protocol is insufficient to induce depression-like behaviors and thus can be used to identify pro-susceptibility factors32.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [32] Golden, S. A. et al. Epigenetic regulation of RAC1 induces synaptic remodeling in stress disorders and depression. Nat. Med. 19, 337–344 (2013). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    Sample size for CSDS mouse cohorts was calculated based on previous studies of CSDS and depression-like behaviors.

    “Sample size for CSDS mouse cohorts was calculated based on previous studies of CSDS and depression-like behaviors11, 32”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [11] Hodes, G. E. et al. Individual differences in the peripheral immune system promote resilience versus susceptibility to social stress. Proc. Natl. Acad. Sci. USA 111, 16136–16141 (2014). source
    • cites [32] Golden, S. A. et al. Epigenetic regulation of RAC1 induces synaptic remodeling in stress disorders and depression. Nat. Med. 19, 337–344 (2013). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Previous studies report conflicting findings with regard to infiltration of peripheral immune cells into the brain following social stress.

    “Previous studies report conflicting findings with regard to infiltration of peripheral immune cells into the brain following social stress14, 34.”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [14] Wohleb, E. S., Powell, N. D., Godbout, J. P. & Sheridan, J. F. Stress-induced recruitment of bone marrow-derived monocytes to the brain promotes anxiety-like behavior. J. Neurosci. 33, 13820–13833 (2013). source

      The Results report that repeated social defeat caused peripheral macrophages to infiltrate specific brain regions, supporting one side of the cited comparison. The Discussion also contrasts this finding with earlier work focused on resident microglia, but the passages do not establish that previous studies reported conflicting findings about whether peripheral cells infiltrate the brain. No page number was available in our copy. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
    • cites [34] McKim, D.B. et al. Microglial recruitment of IL-1β-producing monocytes to brain endothelium causes stress-induced anxiety. Mol. Psychiatry https://doi.org/10.1038/mp.2017.64 (2017). source

      The Results section reports that repeated social defeat increased monocyte adhesion to brain endothelial cells, supporting one finding about peripheral immune-cell recruitment after social stress. The paper does not report conflicting findings across studies, and endothelial adhesion does not by itself establish infiltration into brain tissue. No page number is available in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    In ccr2RFP∷cx3cr1GFP double heterozygous mice, adult resident microglia exhibit a ccr2RFP−/cx3cr1GFP+ pattern, whereas peripheral monocytes recruited in response to inflammation are characterized by a ccr2RFP+/cx3cr1GFP− pattern.

    “We took advantage of ccr2RFP∷ cx3cr1GFP double heterozygous mice 35 in which adult resident microglia exhibit a ccr2RFP−/cx3cr1GFP+ pattern35, 36, whereas peripheral monocytes, which are recruited in response to inflammation, are characterized by a ccr2RFP+/cx3cr1GFP− pattern35–37.”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [35] Saederup, N. et al. Selective chemokine receptor usage by central nervous system myeloid cells in CCR2-red fluorescent protein knock-in mice. PLoS One 5, e13693 (2010). source

      The Discussion identifies resident microglia as GFP-only and infiltrating monocyte-derived cells as RFP-positive. It does not characterize the recruited monocytes as uniformly GFP-negative: the Discussion says they have varying degrees of GFP expression, and the Results report RFP/GFP double-positive monocytes entering inflamed brain tissue. (LLM, conf=0.90)

      Experimental — accuracy not yet measured
    • cites [36] Mizutani, M. et al. The fractalkine receptor but not CCR2 is present on microglia from embryonic development throughout adulthood. J. Immunol. 188, 29–36 (2012). source

      The Results section reports that resident microglia are CX3CR1-GFP positive and CCR2-RFP negative in the double-heterozygous mice, including during inflammation. It describes classical infiltrating monocytes as CCR2 positive but CX3CR1 low or negative—not uniformly negative. The Introduction also describes a CX3CR1-high, CCR2-low infiltrating monocyte population, so the claimed pattern is too categorical for recruited peripheral monocytes. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
    • cites [37] Ginhoux, F. & Jung, S. Monocytes and macrophages: developmental pathways and tissue homeostasis. Nat. Rev. Immunol. 14, 392–404 (2014). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Size-selective loosening of the BBB to small molecules (<800 Da) was previously described in cldn5-deficient mice.

    “While size-selective loosening of the BBB to small molecules (< 800 Da) was previously described in cldn5-deficient mice23”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [23] Nitta, T. et al. Size-selective loosening of the blood-brain barrier in claudin-5-deficient mice. J. Cell Biol. 161, 653–660 (2003). source

  • May combine two claims.

    Premisecitation

    No difference in basal IL-6 is observed before stress and IL-6 remains elevated in SS mice 48h after the last defeat.

    “No difference in basal IL-6 was observed before stress and IL-6 remained elevated in SS mice 48h after the last defeat11.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [11] Hodes, G. E. et al. Individual differences in the peripheral immune system promote resilience versus susceptibility to social stress. Proc. Natl. Acad. Sci. USA 111, 16136–16141 (2014). source

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Cohorts were matched as closely as possible for gender, age, race, pH, postmortem interval and RNA integrity number.

    “Cohorts were matched as closely as possible for gender, age, race, pH, postmortem interval and RNA integrity number32.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [32] Golden, S. A. et al. Epigenetic regulation of RAC1 induces synaptic remodeling in stress disorders and depression. Nat. Med. 19, 337–344 (2013). source

      The Results section on MDD subjects describes two postmortem cohorts and refers to supplemental demographic tables, but the passages in our copy do not say the cohorts were matched on the listed characteristics. Searches for matching, postmortem interval, RNA integrity number, and the other specified characteristics did not locate that assertion. (LLM, conf=0.72)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    In the Texas cohort, CLDN5 mRNA level is significantly reduced between MDD patients and healthy controls with no effect of medication.

    “In the Texas cohort, CLDN5 mRNA level was significantly reduced between MDD patients and healthy controls (*p = 0.0435) with no effect of medication”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Ultrastructural abnormalities are present in both large vessels and capillaries of the NAc.

    “Ultrastructural abnormalities were present in both large vessels and capillaries of the NAc”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Acute imipramine injection is not sufficient to alter cldn5 mRNA or social avoidance.

    “acute imipramine injection was not sufficient to alter cldn5 mRNA (Supplementary Fig. 5E) or social avoidance32”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Evans blue accumulates in the perivascular space of NAc blood vessels but not within the brain parenchyma.

    “The dye seemed to accumulate in the perivascular space of NAc blood vessels but not within the brain parenchyma”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Evans blue cannot readily cross the BBB in the absence of neurovascular damage.

  • May combine two claims.

    Findingown data

    Injection of AAV-shRNA-cldn5 in the HIPP has no effect on grooming in the splash test or sucrose preference.

    “Injection of AAV-sRNA-cldn5 and AAV-shRNA viruses in the HIPP (Supplementary Fig. 7A–B) had no effect on grooming in the splash test or sucrose preference”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The NAc is largely impermeable to circulating IL-6 under normal conditions, as biotinylated-IL6 is undetectable in the NAc of unstressed CTRL mice and i.p. injections of recombinant IL-6 do not increase levels of IL-6 in NAc of naive mice despite a large increase in blood.

    “our studies also revealed that the NAc is largely impermeable to circulating IL-6 under normal conditions as we were unable to detect biotinalyted-IL6 in the NAc of unstressed CTRL mice (Fig. 4G) and i.p. injections of recombinant IL-6 did not increase levels of IL-6 in NAc of naive mice (Fig. 4E) despite there being a large increase in the blood of these mice”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The biotinylated IL-6 signal detected in the NAc parenchyma reflects passage of peripheral IL-6 rather than local production or altered trafficking due to tagging.

  • May combine two claims.

    Findingown data

    Stressed AAV-shRNA-cldn5 mice remaining on doxycycline display anhedonia, social avoidance, and lower cldn5 mRNA and protein levels.

    “stressed AAV-shRNA-cldn5 mice in the second cohort remaining on doxycycline (Supplementary Fig. 7G) displayed anhedonia, social avoidance (Supplementary Fig. 7K) and lower cldn5 mRNA and protein levels”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Peripheral monocytes accumulate within ventricular space and NAc blood vessels, but do not infiltrate the brain parenchyma.

    “further analysis by IHC revealed that peripheral monocytes accumulate within ventricular space and NAc blood vessels, but do not infiltrate the brain parenchyma”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    No change is observed for other claudins or markers of endothelial cells, pericytes, astrocytes, and microglia, or protein level of endothelial cell marker CD31, after AAV-shRNA-cldn5.

    “No change was observed for other claudins or markers of endothelial cells, pericytes, astrocytes and microglia (Supplementary Fig. 6A, qPCR primers are listed in Supplementary Information Table 4) or protein level of endothelial cell marker CD31”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Recovery of normal cldn5 expression reverses anhedonia and promotes resilience in the social interaction test in stressed AAV-shRNA-cldn5 mice.

    “Recovery of normal cldn5 expression reversed anhedonia and promoted resilience in the social interaction test in stressed AAV-shRNA-cldn5 mice”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Biotinylated-IL6 is only detectable in the NAc of SS mice and labeling with CD31 reveals passage outside of blood vessels into the parenchyma.

    “biotinylated-IL6 was only detectable in the NAc of SS mice and labeling with the perivascular marker CD31 revealed passage outside of blood vessels into the parenchyma”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The biotinylated IL-6 signal detected in the NAc parenchyma reflects passage of peripheral IL-6 rather than local production or altered trafficking due to tagging.

  • May combine two claims.

    Findingown data

    Stressed AAV-shRNA-cldn5 mice display greater social avoidance compared to unstressed controls and stressed AAV-shRNA mice.

    “They also displayed greater social avoidance when compared to unstressed controls and stressed AAV-shRNA mice as measured by lower social interaction ratio (*p = 0.0386)”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Lack of significant medication effects may be related to suicide as cause of death for the majority of MDD patients in the cohorts.

    “Lack of significant medication effects may be related to suicide as cause of death for the majority of MDD patients in our cohorts.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Loss of CLDN5 may be at least partly specific to mood disorders as no change is observed in postmortem NAc tissue from cocaine users compared to healthy controls.

    “loss of CLDN5 may be at least partly specific to mood disorders as no change was observed in postmortem NAc tissue from cocaine users when compared to healthy controls”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    cldn5 downregulation by stress does not occur ubiquitously throughout the brain and therefore likely plays a specialized role in depression-like symptomatology.

    “cldn5 downregulation by stress does not occur ubiquitously throughout the brain and therefore likely plays a specialized role in depression-like symptomatology”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In rodents, CSDS induces a depression-like phenotype (social avoidance, anhedonia) in a subset of mice termed stress-susceptible that can be reversed only by chronic, but not acute, antidepressant treatment.

    “Similarly, in rodents, CSDS induces a depression-like phenotype (social avoidance, anhedonia) in a subset of mice termed stress-susceptible (SS) that can be reversed only by chronic, but not acute, antidepressant treatment25, 26.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [25] Berton, O. & Nestler, E. J. New approaches to antidepressant drug discovery: beyond monoamines. Nat. Rev. Neurosci. 7, 137–151 (2006). source
    • cites [26] Ménard, C., Hodes, G. E. & Russo, S. J. Pathogenesis of depression: Insights from human and rodent studies. Neuroscience 321, 138–162 (2016). source

  • Classified as probably not a substantial claim.

    Premisecitation

    Cldn5 is a major cell adhesion molecule of endothelial cells.

    “Cldn5 is a major cell adhesion molecule of endothelial cells22”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [22] Günzel, D. & Yu, A. S. Claudins and the modulation of tight junction permeability. Physiol. Rev. 93, 525–569 (2013). source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Chronic social stress is a prominent contributor to mood disorder prevalence and suicide attempts in victims of bullying.

    “Chronic social stress is a prominent contributor to mood disorder prevalence and suicide attempts in victims of bullying24.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [24] Meltzer, H., Vostanis, P., Ford, T., Bebbington, P. & Dennis, M. S. Victims of bullying in childhood and suicide attempts in adulthood. Eur. Psychiatry 26, 498–503 (2011). source

  • May combine two claims.

    Interpretationown data

    Chronic social stress alters BBB integrity through downregulation of cldn5 in the NAc which, combined with stress-induced recruitment of peripheral immune signals, results in increased BBB permeability and passage of blood circulating proteins such as IL-6 and the development of depression-like behaviors.

    “Overall, our findings suggest that chronic social stress alters BBB integrity through downregulation of the tight junction protein cldn5 in the NAc which, combined with stress-induced recruitment of peripheral immune signals, results in increased BBB permeability and passage of blood circulating proteins such as IL-6 and the development of depression-like behaviors”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Evans blue cannot readily cross the BBB in the absence of neurovascular damage.
    • Rests on an assumption: The biotinylated IL-6 signal detected in the NAc parenchyma reflects passage of peripheral IL-6 rather than local production or altered trafficking due to tagging.

  • May combine two claims.

    Interpretationown data

    BBB integrity is impaired in SS, but not RES mice, in line with a loss of Cldn5 and abnormal blood vessel ultrastructure.

    “Together, these observations indicate that BBB integrity is impaired in SS, but not RES mice, in line with a loss of Cldn5 and abnormal blood vessel ultrastructure.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Evans blue cannot readily cross the BBB in the absence of neurovascular damage.

  • May combine two claims.

    Interpretationown data

    cldn5 expression plays a protective role in behavioral response to social stress, possibly by maintaining BBB impermeability to stress-induced passage of peripheral immune signals.

    “These findings suggest that cldn5 expression plays a protective role in behavioral response to social stress, possibly by maintaining BBB impermeability to stress-induced passage of peripheral immune signals.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    All mouse procedures were performed in accordance with the National Institutes of Health Guide for Care and Use of Laboratory Animals and the ISMMS Animal Care and Use Committee.

    “All mouse procedures were performed in accordance with the National Institutes of Health Guide for Care and Use of Laboratory Animals and the ISMMS Animal Care and Use Committee.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Social stress causes direct passage of the pro-inflammatory cytokine IL-6, which then acts directly within the NAc to induce depression-like behaviors.

    “These observations indicate that social stress causes direct passage of the pro-inflammatory cytokine IL-6, which then acts directly within the NAc to induce depression-like behaviors.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The biotinylated IL-6 signal detected in the NAc parenchyma reflects passage of peripheral IL-6 rather than local production or altered trafficking due to tagging.

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Subjects with known history of neurological disorders or head injury were excluded.

    “Subjects with knock history of neurological disorders or head injury were also excluded.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Placement of virus injections was validated with visualization of blood vessels with EB, green fluorescent protein (gfp) and cldn5 IHC.

    “Placement was validated with visualization of blood vessels with EB, green fluorescent protein (gfp) and cldn5 IHC.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    A kidney lysate was used as a positive control in the Evans blue quantification assay.

    “A kidney lysate was used as a positive control.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All blood vessels on the sample were imaged at a low and high magnification, with a total minimum of 100 images per animal (grid) sampled.

    “All blood vessels on the sample were imaged at a low and high magnification, with a total minimum of 100 images per animal (grid) sampled.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Outliers for social interaction (SI) test screening were identified as being greater than two standard deviations from the mean and excluded.

    “Outliers for social interaction (SI) test screening were identified as being greater than two standard deviations from the mean and excluded.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Dead cells and doublets were excluded from all flow cytometry analysis.

    “Dead cells and doublets were excluded from all analysis.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    Clinical records and interviews were obtained for each case and reviewed by three to four mental health professionals to establish independent diagnoses followed by a consensus diagnosis in line with the Diagnostic and Statistical Manual of Mental Disorders (DSM) IV criteria.

    “Clinical records and interviews were obtained for each case and reviewed by three to four mental health professionals to establish independent diagnoses followed by a consensus diagnosis in line with the Diagnostic and Statistical Manual of Mental Disorders (DSM) IV criteria.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    Blood toxicology was performed to exclude subjects using illicit drugs or psychotropic medications.

    “Blood toxicology was performed to exclude subjects using illicit drugs or psychotropic medications.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    One unstressed AAV-shRNA-cldn5 mouse was excluded after verification of virus injection placement.

    “One unstressed AAV-shRNA-cldn5 mouse was excluded after verification of virus injection placement.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    All mice were assigned to stress-susceptible (SS) or resilient (RES) groups based on their behavioral profile when compared to unstressed controls (CTRL).

    “All mice were assigned to stress-susceptible (SS) or resilient (RES) groups based on their behavioral profile when compared to unstressed controls (CTRL).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    If automated tracking was not possible, scoring was done by experimenters blinded to experimental conditions for splash test, sucrose preference test and forced swim test.

    “If not, scoring was done by experimenters blinded to experimental conditions (for splash test, sucrose preference test and forced swim test).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All quantitative PCR, immunohistochemistry and BBB-related tracer quantification were performed in duplicate in two different cohorts of mice.

    “All quantitative PCR, immunohistochemistry and BBB-related tracer quantification were performed in duplicate in two different cohorts of mice.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    SI screening and behavioral tests were performed with automated tracking systems when possible.

    “SI screening and behavioral tests were performed with automated tracking systems when possible.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Outliers for behavioral testing, for example characterized by impaired locomotion, were identified as being greater than two standard deviations from the mean and excluded from statistical analysis.

    “Outliers for behavioral testing, for example characterized by impaired locomotion, were identified as being greater than two standard deviations from the mean and excluded from statistical analysis.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    CTRL and SS mice were randomly assigned to vehicle or imipramine treatment groups.

    “CTRL and SS mice were randomly assigned to vehicle or imipramine treatment groups using Excel spreadsheet random function.”
    • Also stated in: § Imipramine treatment · plain
      “Following SI test, unstressed CTRL and SS mice were randomly divided into either vehicle or imipramine treatment groups.”
    Quote in the paperSubstantial claim
50 of 50

  • The paper relies on this without support.

    Evans blue cannot readily cross the BBB in the absence of neurovascular damage.

    “which cannot readily cross the BBB in the absence of neurovascular damage”

  • The paper relies on this without support.

    The biotinylated IL-6 signal detected in the NAc parenchyma reflects passage of peripheral IL-6 rather than local production or altered trafficking due to tagging.

    “we tagged mouse recombinant IL-6 with biotin (~0.45 kDa) and injected it retro-orbitally into the blood of CTRL, SS or RES mice”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Anxiety and major depressive disorder, as stress-linked psychiatric conditions, are accompanied by systemic inflammation.

    “Stress-linked psychiatric disorders, including anxiety and major depressive disorder, are associated with systemic inflammation.”

    From Central regulation of stress-evoked peripheral immune responses (2023) · cites this paper as [7]

    The Introduction reports higher circulating pro-inflammatory cytokines in patients with major depressive disorder and describes immune activation under chronic stress. It does not establish an association between systemic inflammation and anxiety; the Results discuss anxiety-related behavior, but not that association. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Social defeat stress increases inflammatory TNF and/or NF-κB signaling in endothelial cells and reduces claudin-5 expression.

    “Mechanistically, social defeat stress upregulates inflammatory TNF and/or nuclear factor-κB (NFКB) signaling pathways in endothelial cells and diminishes expression of the tight junction protein claudin-5 (CLDN5)7,74.”

    From Central regulation of stress-evoked peripheral immune responses (2023) · cites this paper as [7]

    The Results section on stress vulnerability reports reduced cldn5 mRNA and protein in nucleus accumbens blood vessels of stress-susceptible mice, but not resilient mice. Our copy does not report upregulation of TNF or NF-κB signaling in endothelial cells; searches for those terms did not identify supporting passages. Page numbers are unavailable in the copy. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Reduced claudin-5 permits pro-inflammatory leukocytes or their secreted factors to enter brain parenchyma and affect neuronal excitability.

    “This allows pro-inflammatory leukocytes, or their secreted factors (such as IL6 or matrix metalloproteinase-8), to enter the brain parenchyma where they impact neuronal excitability7,75,76 (Fig. 3).”

    From Central regulation of stress-evoked peripheral immune responses (2023) · cites this paper as [7]

    The Results (page unavailable) show that claudin-5 downregulation permits circulating IL-6 to enter the nucleus accumbens parenchyma, and the Discussion says monocytes at blood vessels can release cytokines that act locally on neurons and glia. But the Results say those monocytes did not enter the parenchyma, and the cited passages do not establish an effect on neuronal excitability or passage of matrix metalloproteinase-8. (LLM, conf=0.90)

    Experimental — accuracy not yet measured

  • The severity of depression is associated with the secretion level of circulating cytokines and chemokines, which compromise the BBB and then activate central immune responses.

    “Our previous findings and those of others indicate that the severity of depression is associated with the secretion level of circulating cytokines and chemokines, which compromise the blood–brain barrier (BBB) and then activate central immune responses [10–13].”

    From Chronic stress-induced depression requires the recruitment of peripheral Th17 cells into the brain (2022) · cites this paper as [11]

    The Introduction reports higher circulating pro-inflammatory cytokines in patients with depression, and the Discussion links stress-induced BBB leakiness to IL-6 entering the brain and acting on neurons and glia (pages not provided). The paper does not establish that depression severity tracks circulating cytokine and chemokine secretion, or that those molecules themselves compromise the BBB and then activate central immune responses. It instead attributes BBB impairment primarily to stress-related loss of claudin-5. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

  • Proinflammatory cytokine mediated disruption of the blood-brain barrier is the primary link connecting peripheral and neuroinflammation.

    “Proinflammatory cytokine mediated disruption of the BBB is the primary link connecting peripheral and neuroinflammation (81).”

    From Chronic stress, neuroinflammation, and depression: an overview of pathophysiological mechanisms and emerging anti-inflammatories (2023) · cites this paper as [81]

    The Discussion (page not provided) links BBB leakiness to the passage of peripheral IL-6 into the brain. But it says chronic social stress disrupts BBB integrity through claudin-5 loss, allowing cytokines to enter—not that cytokines mediate the disruption. It also does not identify this pathway as the primary link between peripheral and neuroinflammation. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Medicated MDD subjects versus medication-based exclusion

    Minor

    The results state that about half of the MDD subjects in each cohort were taking medication at death, but the human tissue methods say subjects using psychotropic medications were excluded. The methods do not state an exception for MDD subjects.

1 of 1

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Authors
Menard, C., Pfau, M. L., Hodes, G. E., Kana, V., Wang, V. X., Bouchard, S., Takahashi, A., Flanigan, M. E., Aleyasin, H., LeClair, K. B., Janssen, W. G., Labonté, B., Parise, E. M., Lorsch, Z. S., Golden, S. A., Heshmati, M., Tamminga, C., Turecki, G., Campbell, M., Fayad, Z. A., Tang, C. Y., Merad, M., & Russo, S. J.
Affiliations
  • Icahn School of Medicine at Mount Sinai (US)
  • Tisch Cancer Institute (US)
  • University of Tsukuba (JP)
  • The University of Texas Southwestern Medical Center (US)
  • Douglas Mental Health University Institute (CA)
  • Trinity College Dublin (IE)
Corresponding author
Russo, Scott J.
ORCID
Venue
Nature Neuroscience
Publisher
Springer Science and Business Media LLC
Published
2017-11-13
Volume
20
Issue
12
Pages
1752-1760
ISSN
  • 1097-6256 (ISSN-L)
  • 1546-1726
DOI
10.1038/s41593-017-0010-3
PMC
PMC5726568
OpenAlex
W2767440265
Semantic Scholar
66079f02fd3a498f89804c77717db403860e60a8
Cited by
1,028
References
53
Citations by year
2026: 132 · 2025: 152 · 2024: 147 · 2023: 122 · 2022: 137 · 2021: 110 · 2020: 90 · 2019: 80 · 2018: 50 · 2017: 5
FWCI
30.52
Type
journal article
Language
en
Open access
Licence
www.springer.com/tdm (unspecified)
Locations
  • Nature Neuroscience (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
  • Sunderland Repository (University of Sunderland) (submittedVersion)
Funders
  • Health Research Board (HRA-POR-2015-1077)
  • Japan Society for the Promotion of Science (17H04766, 15K12773)
  • National Institute of Mental Health (F31MH105217, F30MH100835, R01MH090264, F30MH110073, P50MH096890, T32MH096678, R01MH114882, F31MH111108, R01MH104559, T32MH087004)
  • National Center for Complementary and Integrative Health (P50AT008661)
Topics
  • Life Sciences › Neuroscience › Neurology › Barrier Structure and Function Studies
  • Life Sciences › Neuroscience › Biological Psychiatry › Tryptophan and brain disorders
  • Life Sciences › Neuroscience › Behavioral Neuroscience › Stress Responses and Cortisol
Keywords
chronic social defeat stress, major depressive disorder, blood-brain barrier permeability, claudin-5, tight junctions, nucleus accumbens, peripheral inflammation, interleukin-6, antidepressant treatment, stress resilience, neurovascular pathology
MeSH terms
Animals, Anxiety, Behavior, Animal, Blood-Brain Barrier, Depression, Feeding Behavior, Food Preferences, Imipramine, Male, Mice, Inbred C57BL, Nucleus Accumbens, Social Environment, Stress, Psychological, Swimming, Interleukin-6, Adrenergic Uptake Inhibitors, Mice, Claudin-5, Tight Junction Proteins

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-25.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-25.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

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