Mitochondrial Dysfunction Induces Senescence with a Distinct Secretory Phenotype

In the paper

“Notably, NAD+ declines with age in several tissues”

What the sources say

• Supported

  The Abstract reports a significant age-related decline in intracellular NAD+ in the heart, lung, liver, and kidney of female Wistar rats. The Discussion likewise reports declining NAD+ levels with aging in those organs. (LLM, conf=0.93)

  cites Braidy et al., 2011 source
• Partly supported

  In Results, under “Nuclear NAD+ Levels Regulate Mitochondrially Encoded Genes” (page unavailable), the paper reports less total NAD+ in the skeletal muscle of elderly mice and describes an overall age-related decline. It does not establish the citing sentence’s more specific claim that NAD+ declines in several tissues. (LLM, conf=0.86)

  cites Gomes et al., 2013 sourceExperimental — accuracy not yet measured
• Supported

  The Introduction states that NAD+ levels decline with age in multiple peripheral tissues. The Results also report an age-related decline in mouse hippocampal NAD+ levels. No page numbers are provided in our copy. (LLM, conf=0.94)

  cites Stein and Imai, 2014 source

In the paper

“sustained activation of 5′AMP-activated protein kinase (AMPK), a major bioenergetic sensor, is a hallmark of senescence (Moiseeva et al., 2009) and can induce a senescence arrest”

What the sources say

• Partly supported

  The Results (page not provided) show that AMPK was highly active in Ras-senescent cells compared with control cells, and that RISP knockdown both activated AMPK and produced senescent features. This supports an association in the studied models, but does not establish sustained AMPK activation as a hallmark of senescence generally. The citation is attached to the hallmark clause, not the subsequent claim that AMPK activation can induce arrest. (LLM, conf=0.84)

  cites Moiseeva et al., 2009 sourceExperimental — accuracy not yet measured
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Jiang et al., 2013b
• ?Not checked — no full text of the sourcecites Jones et al., 2005 source

In the paper

“Dysfunctional mitochondria accumulate with age, best documented in tissues comprised largely of post-mitotic cells”

What the sources say

• ?Not checked — no full text of the sourcecites Herbst et al., 2007 source
• Partly supported

  The Results (page unavailable) report age-associated reductions in muscle mitochondrial function in old mice, supporting the claim's general point about aging and dysfunction. They do not establish that dysfunctional mitochondria accumulate or that the pattern is best documented in largely post-mitotic tissues; the reported mitochondrial density in soleus muscle decreased with age. (LLM, conf=0.84)

  cites Lee et al., 2010 sourceExperimental — accuracy not yet measured
• Partly supported

  The Introduction reports that older adults’ skeletal muscle shows an accumulation of mitochondrial abnormalities, and the Discussion reports accumulated mtDNA mutations and deletions in older muscle. Neither passage says that accumulation is best documented in tissues composed largely of post-mitotic cells; the paper also notes that age-related changes in mitochondrial function in human muscle remain equivocal. (LLM, conf=0.84)

  cites Safdar et al., 2010 sourceExperimental — accuracy not yet measured

In the paper

“it induced cell death after SIRT1-depletion (not shown), as reported”

What the sources say

• Supported

  The Results section reports ionizing-radiation-induced apoptosis in SIRT1-deficient mouse thymocytes, with greater radiation sensitivity than in control thymocytes. The finding concerns thymocytes; the paper does not report the same increased sensitivity in embryonic fibroblasts. (LLM, conf=0.88)

  cites Cheng et al., 2003 source
• Supported

  Figure 4E (captioned under Cell viability assay; page unavailable) describes A549 cells treated with ionizing radiation and their apoptotic population measured 48 hours later. The section “DBC1 phosphorylation is important for cellular stress response” identifies the Figure 4E cells as depleted of SIRT1 and discusses their DNA damage-induced apoptosis. (LLM, conf=0.85)

  cites Yuan et al., 2012 source

In the paper

“Dysfunctional mitochondria can induce cellular senescence in culture (Moiseeva et al., 2009; Wang et al., 2003) and in vivo (Dai et al., 2010; Kang et al., 2013).”

What the sources say

• Supported

  Moiseeva et al. is cited for the culture portion of the sentence, not the in vivo portion. The Results report that interfering with mitochondrial function induced senescence markers, and the Discussion states that disrupting electron transport or oxidative phosphorylation was sufficient to trigger senescent cell-cycle arrest in human cells. (LLM, conf=0.92)

  cites Moiseeva et al., 2009 source
• ?Not checked — no full text of the sourcecites Wang et al., 2003 source
• Supported

  Dai et al. is cited for the in vivo portion of the sentence, not the culture portion. In the Results section, older mitochondrial mutator mouse hearts had approximately threefold higher expression of the senescence marker p16INK4a than wild-type hearts, and mitochondrial-targeted catalase partially reduced it. (LLM, conf=0.88)

  cites Dai et al., 2010 source

In the paper

“This senescence-associated secretory phenotype (SASP) comprises pro-inflammatory cytokines, proteases, and growth and angiogenesis factors”

What the sources say

• Partly supported

  The Discussion describes inflammatory cytokines and growth factors as SASP components and says chronic SASP secretion may disrupt normal tissue structure and function. The passages retrieved from our copy do not establish proteases or angiogenesis factors as SASP components, so the composition stated in the citing sentence is only partly supported. (LLM, conf=0.82)

  cites Coppé et al., 2008 sourceExperimental — accuracy not yet measured

In the paper

“Increased ADP:ATP or AMP:ATP ratios activate AMPK (Hardie et al., 2012)”

What the sources say

• Supported

  The Introduction states that AMPK senses increases in both AMP:ATP and ADP:ATP ratios. The ‘AMPK – subunits and regulation’ section explains that AMP activates AMPK allosterically, while both AMP and ADP can promote its activation through effects on phosphorylation. (LLM, conf=0.94)

  cites Hardie et al., 2012 source

In the paper

“Since p53 inhibits RELA by competing for CBP binding (Webster and Perkins, 1999), p53 likely limits the IL1 arm of the SASP by reducing NF-κB activity.”

What the sources say

• Supported

  The Results report that p53 inhibits RelA-mediated transcription and that adding CBP reverses this inhibition. The Discussion states that p53 and RelA bind p300 and CBP competitively, while noting that this mechanism may only partially explain their transcriptional cross talk. The cited claim concerns RelA activity; the sentence’s subsequent inference about the SASP is not attributed to this source. (LLM, conf=0.91)

  cites Webster and Perkins, 1999 source

In the paper

“Notably, many SASP factors that were not expressed by SIRT3-depleted cells are pro-inflammatory, although the cells uniquely secreted CCL27”

• Also stated in: § Mitochondrial SIRTs Suppress Senescent Phenotypes · plain

  “a pro-inflammatory cytokine that comprises the SASP of mouse, but not human, fibroblasts induced to senesce by IR”

What the sources say

• Partly supported

  The Introduction and Discussion describe inflammatory cytokines as SASP factors, supporting the general characterization of many SASP factors as pro-inflammatory. The Results discuss CCL-family factors in irradiated mouse and human fibroblasts, but the passages found do not identify CCL27 as present in the mouse SASP and absent from the human SASP. The paper does not address SIRT3-depleted cells; their secretion profile is the citing authors’ own finding. (LLM, conf=0.78)

  cites Coppé et al., 2010 sourceExperimental — accuracy not yet measured

In the paper

“IR robustly activates p53, which subsides to a low chronic level in 7–10 days as the SASP develops (Coppé et al., 2008; Rodier et al., 2009).”

What the sources say

• Partly supported

  The Results passage discussing Figure 1D and Figure S3 reports p53 stabilization and phosphorylation after irradiation, and says a robust SASP developed 4–7 days later. The passage discussing Figure 6G also gives 4–7 days for cells with wild-type p53. Neither passage says p53 subsided to a low chronic level in 7–10 days. (LLM, conf=0.86)

  cites Coppé et al., 2008 sourceExperimental — accuracy not yet measured
• Partly supported

  The passage labeled Abstract (page unavailable; Fig. 1a–c) reports rapid p53 activation after irradiation, and another passage reports that inflammatory cytokine secretion develops after a delay following a senescence-inducing dose. It does not establish that p53 subsides to a low chronic level at 7–10 days: the reported return toward baseline within 10 hours concerns a low dose from which cells recovered, while cytokine secretion reached senescent levels within 3–5 days. (LLM, conf=0.87)

  cites Rodier et al., 2009 sourceExperimental — accuracy not yet measured

In the paper

“or stabilizing p16INK4a mRNA (Chang et al., 2010)”

What the sources say

• Partly supported

  The Results and Discussion (page not provided) link increased p16 mRNA stability with replicative senescence and describe HuR-mediated p16 mRNA decay. They do not show that AMPK activation stabilizes p16 mRNA or induces senescence through that mechanism. (LLM, conf=0.85)

  cites Chang et al., 2010 sourceExperimental — accuracy not yet measured

In the paper

“We reported that elevated oxygen dampens the SASP in humans and mouse cells (Coppé et al., 2010; Parrinello et al., 2003).”

What the sources say

• Partly supported

  The Results section on mouse fibroblast SASPs reports that 20% oxygen suppresses the SASP in mouse cells compared with 3% oxygen. It also says oxygen had only minor effects on senescent human cells, which developed robust SASPs at both concentrations. The claim is supported for mouse cells but not for human cells. (LLM, conf=0.91)

  cites Coppé et al., 2010 sourceExperimental — accuracy not yet measured
• ?Could not verify

  The paper’s Abstract (page unavailable) compares how 3% and 20% oxygen affect senescence, proliferation, and DNA damage in mouse and human fibroblasts. Searches for SASP, secretory phenotype, secretion, and cytokines found no passage addressing whether elevated oxygen dampens the SASP. (LLM, conf=0.75)

  cites Parrinello et al., 2003 sourceExperimental — accuracy not yet measured

In the paper

“Mitochondrial ROS can damage nuclear DNA, thus activating a DNA damage response that induces senescence (Moiseeva et al., 2009; Passos et al., 2010).”

What the sources say

• Supported

  The Results report oxidative DNA damage in the nuclei of Ras-expressing cells alongside mitochondrial ROS production. The Discussion says ROS-related damage to nuclear DNA could activate p53 and Rb, sustaining pathways involved in senescence. This supports the claim as a possible mechanism, rather than one the paper establishes as the sole cause of senescence. (LLM, conf=0.88)

  cites Moiseeva et al., 2009 source
• Supported

  The Introduction (page unavailable) says ROS can directly damage DNA, inducing a DNA damage response and senescence. The Results and Discussion (pages unavailable) connect mitochondrial dysfunction and ROS production to renewed DNA damage foci and the maintenance of senescent growth arrest. (LLM, conf=0.90)

  cites Passos et al., 2010 source

In the paper

“Our finding that loss of SIRT3 loss drives senescence appears to contradict a report in which cells from SIRT3 knockout mice were highly susceptible to oncogenic transformation; however, this susceptibility depended on the elevated ROS characteristic of sirt3−/− cells (Kim et al., 2010).”

What the sources say

• Partly supported

  The Results sections on transformation and SOD report that SIRT3−/− mouse embryonic fibroblasts were transformed by a single oncogene and that MnSOD prevented their immortalization by Myc or Ras alone. The claim overgeneralizes the ROS dependence: MnSOD did not prevent immortalization when the cells expressed both Myc and Ras. The paper also reports normal superoxide levels in unstressed knockout cells, rather than uniformly elevated levels. (LLM, conf=0.87)

  cites Kim et al., 2010 sourceExperimental — accuracy not yet measured

In the paper

“Mitochondrial dysfunction has been linked to aging (Khrapko and Vijg, 2009), but it is not clear how it drives aging, particularly in mitotic tissues.”

What the sources say

• Supported

  The section “Mitochondria: molecular clocks of aging?” describes a proposed central role for mitochondria in aging. “Dividing tissues: mtDNA mutations in stem cells” calls mutation accumulation an attractive candidate aging mechanism while noting that its causal role remains unproven. These passages support the cited link without claiming that the mechanism is settled; page numbers were not provided. (LLM, conf=0.92)

  cites Khrapko and Vijg, 2009 source

In the paper

“In addition, they secreted HMGB1, a pro-inflammatory alarmin that is a feature of senescent cells (Davalos et al., 2013).”

What the sources say

• Supported

  The Introduction states that HMGB1 is an alarmin that provokes an innate immune response and that senescent cells secrete it early after a senescence-inducing stimulus. The Discussion likewise identifies HMGB1 as an alarmin and reports its active secretion by senescent cells, linking it to their inflammatory activity. (LLM, conf=0.94)

  cites Davalos et al., 2013 source

In the paper

“These data support the findings that epidermal-specific SOD2-deficient mice rapidly accumulate senescent keratinocytes, which show enhanced differentiation (Velarde et al., 2015) and that POLGD257A mice have a thicker stratum corneum and lipodystrophy compared to age-matched WT mice (Trifunovic et al., 2004).”

What the sources say

• Partly supported

  The Results report increased senescence markers in epidermal keratinocytes after Sod2 deletion and enhanced keratinocyte differentiation at wound sites in young mice. However, senescence was assessed four months after deletion, so the paper does not establish that senescent keratinocytes accumulated rapidly; it also does not show that the senescent cells specifically were the ones with enhanced differentiation. (LLM, conf=0.83)

  cites Velarde et al., 2015 sourceExperimental — accuracy not yet measured

In the paper

“SIRT3 depletion induced three senescence markers: reduced lamin B1 (LMNB1) levels”

• Also stated in: § Mitochondrial SIRTs Suppress Senescent Phenotypes · plain

  “decreased nuclear localization of high mobility group protein B1 (HMGB1)”

• Also stated in: § Mitochondrial SIRTs Suppress Senescent Phenotypes · plain

  “increased levels of the cell-cycle inhibitor p21WAF1”

In the paper

“we identified the mitochondrial SIRTs SIRT3 and to a lesser extent SIRT5, as suppressors of senescence and modulators of the SASP.”

In the paper

“We show here that several manipulations that compromise mitochondrial function in proliferating human cells induce a senescence growth arrest with a modified SASP that lacks the IL-1-dependent inflammatory arm.”

In the paper

“These phenotypes occurred in cultured human cells and a murine model of premature aging through mitochondrial dysfunction”

In the paper

“Despite lacking IL-1-dependent SASP factors, the MiDAS SASP suppressed adipocyte differentiation and promoted keratinocyte differentiation.”

In the paper

“Despite the induction of other senescence markers, neither SIRT depletion increased IL-6 secretion”

In the paper

“SIRT3-depleted cells failed to express significant levels of the SASP mRNAs encoding IL1B, CXCL1, CXCL2, IL-6, IL-8 and VEGF, but expressed high levels of mRNAs encoding the SASP factors AREG and IL-10, regardless of IR exposure”

In the paper

“IR increased NF-κB activity in WT cells, as reported (Freund et al., 2011), but failed to do so in rho0 cells without pyruvate and reduced NF-κB activity to below that of unirradiated rho0 cells cultured with pyruvate (Figure 5F).”

In the paper

“SIRT3 depletion strongly suppressed IL-6 secretion by cells induced to senesce by IR, NaBu, or Bleo (Figure 1H) and moderately suppressed IL-6 secretion in response to MKK6EE or RAS”

In the paper

“while the NAD+/NADH ratio declined with MiDAS, total NAD+ actually increased”

• Also stated in: § Decreased NAD+/NADH Ratios Mediate MiDAS · plain

  “along with a rise in nicotinamide phosphoribosyltransferase (NAMPT) mRNA”

In the paper

“An NF-κB reporter showed that NF-κB activity was high in rho0 cells cultured with pyruvate but much lower in rho0 cells without pyruvate (Figure 5F).”

In the paper

“Notably, some secreted factors were unaffected by MiDAS and were insensitive to pyruvate.”

In the paper

“pyruvate lowered cytosolic NADH to a much larger degree than in WT cells; it also lowered mitochondrial NADH in rho0 cells, but to a lesser extent than in the cytosol.”

In the paper

“In rho0 cells, lactate elicited only a small cytosolic response, suggesting that NADH was already reduced in this compartment.”

In the paper

“when we depleted NAD+ by preventing NAD salvage using the NAMPT inhibitor FK866, cell proliferation ceased after ~7 day”

• Also stated in: § Decreased NAD+/NADH Ratios Mediate MiDAS · plain

  “and cells became senescent after ~21 days”

In the paper

“Upon pyruvate withdrawal, rho0, but not WT, cells rapidly senesced, as measured by low EdU labeling and high SA-Bgal”

In the paper

“the antioxidant EUK-134 reduced mitochondrial, but not cytoplasmic, ROS in SIRT3- and HSPA9-depleted cells”

• Also stated in: § Mitochondrial Dysfunction and Senescent Phenotypes · plain

  “but did not prevent the growth arrest of these or Rot-treated cells”

In the paper

“FK866 suppressed IR-induced IL-6 secretion (Figure 3I) and lowered total NAD levels (Figure 3J).”

In the paper

“MiDAS also increased p21WAF1 and p16INK4a and decreased LMNB1 and intracellular HMGB1 protein levels, which were prevented by pyruvate.”

In the paper

“Although IR induced a SASP in WT cells with or without pyruvate, rho0 cells plus pyruvate expressed an enhanced SASP that was suppressed by IR (Figures 5E and S5C).”

In the paper

“MiDAS also increased p21WAF1 and p16INK4a and decreased LMNB1 and intracellular HMGB1 protein levels, which were prevented by pyruvate.”

In the paper

“AOA-treated WT cells underwent senescence (high SA-Bgal, low EdU labeling, loss of nuclear HMGB1; Figures 3D, 3E, S3G, and S3H) but failed to secrete IL-6 following IR, despite slightly higher secretion by unirradiated AOA-treated cells”

In the paper

“All treatments induced senescence as determined by reduced EdU incorporation, increased SA-Bgal activity”

• Also stated in: § Mitochondrial Dysfunction and Senescent Phenotypes · plain

  “and loss of nuclear HMGB1 (for rho0 and Rot”

In the paper

“rho0 and SIRT3-depleted cells showed no increase in 53BP1 foci”

• Also stated in: § Mitochondrial Dysfunction and Senescent Phenotypes · plain

  “and EUK-134 had no effect on these foci in any senescent cell”

In the paper

“pyruvate lowered NADH in the cytosol, while increasing NADH in mitochondria”

In the paper

“However, only MiDAS cells showed marked activation of both AMPKα (thr-172 phosphorylation) and p53 (ser-15 phosphorylation), both of which were blunted by pyruvate (Figure 4C).”

In the paper

“NMN delayed senescence by ~2 day relative to untreated cells (Figure S3I), but both groups senesced within 7 days”

In the paper

“All these manipulations elevated the ADP:ATP ratio (Figure 4A), which was lowered by pyruvate”

In the paper

“Although shSIRT3 and rho0 cells cultured without pyruvate had elevated Mitosox fluorescence”

• Also stated in: § Mitochondrial Dysfunction and Senescent Phenotypes · plain

  “normalization to Mito-tracker showed roughly equivalent ROS levels between control and SIRT3-depleted cells”

In the paper

“while SIRT3 shRNA induced senescence in wild-type (WT) mouse embryonic fibroblasts (MEFs), MEFs from SIRT3 knockout mice did not senesce”

In the paper

“Upon pyruvate withdrawal, expression of these factors declined to near WT levels”

• Also stated in: § Mitochondrial Dysfunction and Senescent Phenotypes · plain

  “and the cells arrested growth”

In the paper

“Further, compared to WT, POLGD257A epidermis had more senescent cells in the stratum corneum as judged by SA-Bgal positivity (Figures S6C and S6D) and loss of HMGB1 in suprabasal epidermal nuclei (Figures S6E and S6F).”

In the paper

“In MiDAS, pyruvate, but not an antioxidant, prevented MiDAS, which showed no evidence of DNA damage.”

In the paper

“Examples include the pro-inflammatory cytokines CCL27 (Figure 1G) and TNF-α (Figure 5I) and the anti-inflammatory cytokine IL-10 (Figure 5I).”

In the paper

“Inguinal adipose tissue (IAT) from 8-month-old POLGD257A mice had more cells with SA-Bgal (Figures 6A, 6C, S6A, and S6B) and loss of nuclear HMGB1 (Figures 6B and 6D) than age-matched WT IAT, primarily in cells between mature adipocytes.”

In the paper

“MiDAS cells secreted the anti-inflammatory cytokine IL-10, but also high levels of the pro-inflammatory cytokines CCL27 and TNF-α.”

In the paper

“SIRT3 showed a stronger response, likely because it was more efficiently depleted”

In the paper

“there is mounting evidence that senescent cells can accumulate with age and cause or contribute to aging phenotypes and pathologies.”

In the paper

“Inhibition of the latter by depletion of malate dehydrogenase lowers the NAD+/NADH ratio and induces a senescence arrest”

What the sources say

• ?Not checked — no full text of the sourcecites Lee et al., 2012 source

In the paper

“Our data identify a distinct senescence response and provide a mechanism by which mitochondrial dysfunction can drive aging phenotypes.”

In the paper

“We show that MiDAS results from a decreased NAD+/NADH ratio, activation of AMPK and subsequently the tumor suppressor p53, which then limits the IL-1 mediated arm of the SASP.”

In the paper

“Because mitochondria oxidize NADH to NAD+ (Lehninger et al., 2013), mitochondrial dysfunction can decrease the NAD+/NADH ratio.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Lehninger et al., 2013

In the paper

“Because p53 initiates the senescence arrest and is an AMPK target (Jiang et al., 2013b; Jones et al., 2005), we assessed the p53 dependence of MiDAS.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Jiang et al., 2013b
• ?Not checked — no full text of the sourcecites Jones et al., 2005 source

In the paper

“which can induce senescence by phosphorylating p53 (Jones et al., 2005)”

What the sources say

• ?Not checked — no full text of the sourcecites Jones et al., 2005 source

In the paper

“Thus, SIRT3 depletion induced senescence but with a SASP that differed from that induced by IR, suggesting a mitochondrial function is required for expression of a subset of SASP factors.”

In the paper

“IL-1α and IL-1β initiate a positive feedback loop that drives expression of SASP factors such as IL-6 and IL-8 (Orjalo et al., 2009).”

What the sources say

• ?Not checked — no full text of the sourcecites Orjalo et al., 2009 source

In the paper

“We conclude that low NAD+/ NADH ratios mediate MiDAS phenotypes, which are prevented by NADH oxidation.”

In the paper

“IMR-90 human fibroblasts were mycoplasma-free, cultured in 3% O2 as described (Coppé et al., 2008; Rodier et al., 2009), and used between 25 and 40 population doublings.”

In the paper

“MiDAS results from an NADH-AMPK-p53-dependent pathway and elicits a SASP that lacks IL-1-dependent factors but includes others.”

In the paper

“Data are presented either as representative examples or means of 3+ experiments.”

In the paper

“Protocols were approved by the Institutional Animal Care and Use Committee.”

In the paper

“We show that (1) mitochondrial dysfunction induces a senescence response (MiDAS), including arrested growth and a SASP that is distinct from that caused by genotoxic stress;”

In the paper

“These data support the findings that epidermal-specific SOD2-deficient mice rapidly accumulate senescent keratinocytes, which show enhanced differentiation (Velarde et al., 2015) and that POLGD257A mice have a thicker stratum corneum and lipodystrophy compared to age-matched WT mice (Trifunovic et al., 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Trifunovic et al., 2004 source

In the paper

“To determine whether MiDAS occurs in vivo, we analyzed POLGD257A mice, which have a mutation in the proofreading domain of the mtDNA polymerase (PolG) and rapidly accumulate mtDNA mutations and aging phenotypes (Kujoth et al., 2005; Trifunovic et al., 2004).”

What the sources say

• ?Not checked — no full text of the sourcecites Kujoth et al., 2005 source
• ?Not checked — no full text of the sourcecites Trifunovic et al., 2004 source

In the paper

“Because p53 depletion was sufficient to prevent MiDAS, AMPK most likely mediates MiDAS through p53 activation, and subsequent NF-κB inhibition.”