Inhibition of Acyl‐CoenzymeA: Cholesterol Acyltransferase 1 promotes shedding of soluble triggering receptor on myeloid cells 2 (TREM2) and low‐density lipoprotein receptor 1 (LRP1)‐dependent phagocytosis of amyloid beta protein in microglia

ACAT1 inhibition reduces Aβ pathology in AD models.

“Inhibiting ACAT1 has been shown to reduce amyloid beta (Aβ) pathology, though the mechanism is unclear.”

• Also stated in: § BACKGROUND · boosted

  “Previous in vivo work from our lab showed that ACAT1 inhibition reduced Aβ production and deposition in AD mouse models. 12 Other studies showed that ACAT1 inhibition reduced AD pathology by promoting microglia‐mediated clearance of Aβ. 13 , 14 , 15”

• cites [12] Hutter‐Paier B, Huttunen HJ, Puglielli L, et al. The ACAT inhibitor CP‐113,818 markedly reduces amyloid pathology in a Mouse Model of Alzheimer's disease. Neuron. 2010; 68: 1014. doi: 10.1016/j.neuron.2010.11.028 15473963 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

• cites [13] Shibuya Y, Chang CCY, Huang LH, Bryleva EY, Chang TY. Inhibiting ACAT1/SOAT1 in microglia stimulates autophagy‐mediated lysosomal proteolysis and increases Aβ1‐42 clearance. J Neurosci. 2014; 34: 14484– 14501. doi: 10.1523/JNEUROSCI.2567‐14.2014 25339759 PMC4205563 sourceSupported
• cites [14] van der Kant R, Langness VF, Herrera CM, et al. Cholesterol metabolism is a druggable axis that independently regulates tau and amyloid‐β in iPSC‐derived Alzheimer's disease neurons. Cell Stem Cell. 2019; 24: 363– 375. e9. doi: 10.1016/j.stem.2018.12.013 30686764 PMC6414424 sourcePartly supported

  The Introduction reports that cholesterol esters enhance Aβ production and cites ACAT-inhibitor studies; the References list a mouse study in which an ACAT inhibitor reduced amyloid pathology. However, the paper does not leave the mechanism wholly unclear: its Results identify an APP cholesterol-binding domain that mediates the effect of lowering cholesterol esters on Aβ secretion in iPSC-derived neurons. No page numbers are available in our copy. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

TREM2-enriched microglia are found surrounding amyloid plaques.

“with TREM2‐enriched microglia found surrounding amyloid plaques. 16 , 17”

• cites [16] Zhao Y, Wu X, Li X, et al. TREM2 is a receptor for β‐amyloid that mediates microglial function. Neuron. 2018; 97: 1023– 1031. doi: 10.1016/j.neuron.2018.01.031 29518356 PMC5889092 sourcePartly supported

  The Results section reports that microglia clustered at Aβ-enriched regions after Aβ injection in mice, and that clustering was reduced by TREM2 deletion. This supports TREM2-dependent clustering near Aβ, but the paper does not establish that the clustered microglia are TREM2-enriched or show them surrounding amyloid plaques specifically. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites [17] Wang Y, Cella M, Mallinson K, et al. TREM2 lipid sensing sustains the microglial response in an Alzheimer's disease model. Cell. 2015; 160: 1061– 1071. doi: 10.1016/j.cell.2015.01.049 25728668 PMC4477963 sourcePartly supported

  The Results section on microglial colocalization reports clusters of microglia around amyloid plaques in 5XFAD mice, with fewer clusters when TREM2 is deficient. The section on reactive microgliosis reports increased Trem2 expression in microglia isolated during amyloid deposition, but does not establish that the microglia surrounding plaques are specifically TREM2-enriched. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

ACAT1 inhibitors reduce Aβ-induced neurotoxicity.

“ACAT1 inhibitors reduce Aβ‐induced neurotoxicity (reviewed in Shibuya et al. 10 and Chang et al. 11 ).”

• cites [10] Shibuya Y, Chang CCY, Chang T. ACAT1/SOAT1 as a therapeutic target for Alzheimer's disease. Future Med Chem. 2015; 7: 2451– 2467. doi: 10.2307/j.ctvnwc0d0.18 26669800 PMC4976859 sourceNot checked — no full text of the source
• cites [11] Chang TY, Chang CCY, Harned TC, et al. Blocking cholesterol storage to treat Alzheimer's disease. Explor Neuroprotective Ther. 2021; 1: 173– 184. doi: 10.37349/ent.2021.00014 35199105 PMC8863366 sourcePartly supported

  The ‘ACAT1 blockade and AD’ section reports that ACAT1 blockade increases clearance of Aβ oligomers in preclinical models. The ‘Cholesterol loading, CE content, and the A1B hypothesis’ section proposes that blockade helps repair membranes damaged by oligomeric Aβ. These passages support a protective rationale, but they do not report a direct reduction in Aβ-induced neurotoxicity by ACAT1 inhibitors. (LLM, conf=0.83)

  Experimental — accuracy not yet measured

TREM2 regulates cholesterol transport and metabolism through transcriptional regulation and endocytosis of cholesterol-rich substances such as myelin and cell debris.

“Furthermore, TREM2 regulates cholesterol transport and metabolism through transcriptional regulation and endocytosis of cholesterol‐rich substances such as myelin and cell debris. 15”

• cites [15] Nugent AA, Lin K, van Lengerich B, et al. TREM2 regulates microglial cholesterol metabolism upon chronic phagocytic challenge. Neuron. 2020; 105: 837– 854. e9. doi: 10.1016/j.neuron.2019.12.007 31902528 sourcePartly supported

  The Summary and Introduction identify TREM2 as a transcriptional regulator of microglial cholesterol transport and metabolism during chronic myelin phagocytosis. But the Summary says TREM2-deficient microglia still phagocytose myelin debris and fail to clear its cholesterol; the paper does not establish endocytosis of myelin or other cell debris as the mechanism of cholesterol regulation. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Multiple AD mouse models show 3- to 11-fold higher CE levels in the brain compared to controls.

“Additionally, multiple AD mouse models have shown 3‐ to 11‐fold higher CE levels in the brain compared to controls. 7 , 8”

• cites [7] Chan RB, Oliveira TG, Cortes EP, et al. Comparative lipidomic analysis of mouse and human brain with Alzheimer disease. J Biol Chem. 2012; 287: 2678– 2688. doi: 10.1074/jbc.M111.274142 22134919 PMC3268426 sourcePartly supported

  The Results (page unavailable) report approximately 4.3-fold higher total CE in PS1-APP mouse forebrain, with an approximately 11-fold increase in a specific CE species, CE-22:6. They describe only a trend toward higher total CE in APP mice and do not establish a 3- to 11-fold increase in total CE across multiple mouse models. (LLM, conf=0.88)

  Experimental — accuracy not yet measured
• cites [8] Tajima Y, Ishikawa M, Maekawa K, et al. Lipidomic analysis of brain tissues and plasma in a mouse model expressing mutated human amyloid precursor protein/tau for Alzheimer's disease. Lipids Health Dis. 2013; 12: 1– 14. doi: 10.1186/1476‐511X‐12‐68 23659495 PMC3668217 sourceSupported

LRP1 is a widely expressed receptor that enhances Aβ uptake, clearance, and degradation.

“LRP1 is a widely expressed receptor that was previously shown to enhance Aβ uptake, clearance, and degradation. 21”

• cites [21] Liu CC, Hu J, Zhao N, Wang J, Wang N, Cirrito JR, et al. Astrocytic LRP1 mediates brain Aβ clearance and impacts amyloid deposition. J Neurosci. 2017; 37: 4023– 4031. doi: 10.1523/JNEUROSCI.3442‐16.2017 28275161 PMC5391682 sourceSupported

Brain samples from late-onset AD (LOAD) patients exhibit a 1.8-fold increase in CE levels versus controls in vulnerable brain regions.

“Brain samples from late‐onset AD (LOAD) patients exhibit a 1.8‐fold increase in CE levels versus controls in vulnerable brain regions. 7”

• cites [7] Chan RB, Oliveira TG, Cortes EP, et al. Comparative lipidomic analysis of mouse and human brain with Alzheimer disease. J Biol Chem. 2012; 287: 2678– 2688. doi: 10.1074/jbc.M111.274142 22134919 PMC3268426 sourcePartly supported

  The Results report significantly higher cholesterol ester (CE) levels in the entorhinal cortex of LOAD patients, a vulnerable region, but give the increase as approximately 1.7-fold, not 1.8-fold. The 1.8-fold increase reported elsewhere in the Results refers to a different lipid, so the claimed magnitude for CE is not supported. (LLM, conf=0.89)

  Experimental — accuracy not yet measured

Aβ42 uptake significantly increased by 195.8% and 237.9% following treatment with 10 and 15 μM AV, respectively, in WT BV2 microglial cells.

“Aβ42 uptake significantly increased by 195.8% and 237.9% following treatment with 10 and 15 µM AV, respectively (Figure 1B).”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

When comparing WT versus TREM2 KO iMGLs both treated with AV, there was a 130.5% increase in Aβ42 uptake in WT iMGLs versus TREM2 KO iMGLs.

“When comparing WT versus TREM2 KO iMGLs, both treated with AV, we observed a 130.5% increase in Aβ42 uptake in WT iMGLs versus TREM2 KO iMGLs.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

Treatment of WT BV2 cells with AV decreased full-length TREM2 protein levels by 47.2%.

“treatment of WT BV2 cells with AV decreased full‐length TREM2 protein levels (47.2%) (Figure 3A,B).”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

No significant change in Aβ42 uptake was observed in TREM2 KO iMGLs treated with AV compared to control treated TREM2 KO iMGLs.

“However, no significant change in Aβ42 uptake was observed in TREM2 KO iMGLs treated with AV compared to control treated TREM2 KO iMGLs.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

AV CM from WT BV2 cells did not increase Aβ42 uptake in LRP1 KO BV2 cells.

“We also found that AV CM from WT BV2 cells did not increase Aβ42 uptake in LRP1 KO BV2 cells (Figure 4D).”

AV-mediated enhancement of Aβ42 uptake was abrogated in the presence of RAP as compared to control-treated cells.

“Figure 4F shows AV‐mediated enhancement of Aβ42 uptake was abrogated in the presence of RAP as compared to control‐treated cells.”

TREM2 knockout significantly reduced Aβ42 uptake in iMGLs by 40.5% compared to WT iMGLs.

“Figure 2A shows that KO of TREM2 significantly reduced Aβ42 uptake in iMGLs (by 40.5%) compared to WT iMGLs.”

• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

In WT BV2 cells treated with AV overnight, replacing medium with CNT-CM left Aβ42 uptake unchanged.

“In WT BV2 cells treated with AV overnight, in which the medium was then removed and replaced with CNT‐CM, Aβ42 uptake was unchanged (Figure 3E).”

Absence of TREM2 in iMGLs significantly impaired augmented Aβ uptake following ACAT1 inhibition.

“Furthermore, we showed that the absence of TREM2 in iMGLs significantly impaired augmented Aβ uptake following ACAT1 inhibition.”

ACAT1 inhibition increases LRP1 protein levels.

“ACAT1 inhibition increased LRP1 levels and soluble TREM2 (sTREM2) release via enhanced TREM2 cleavage by ADAM metallopeptidase domain 10/17 (ADAM10/17).”

• Also stated in: § BACKGROUND · boosted

  “We also show that ACAT1 inhibition increases protein levels of LRP1.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

LRP1 was essential for enhanced Aβ uptake mediated by sTREM2 following ACAT1 inhibition.

“Here, we showed that LRP1 was essential for enhanced Aβ uptake mediated by sTREM2 following ACAT1 inhibition.”

Inhibition of ADAM10/17 with GW280264X alone does not significantly change Aβ42 uptake compared to control treated cells in WT BV2 microglia.

“Figure 3G shows that the inhibition of ADAM10/17 with GW280264X alone does not significantly change Aβ42 uptake compared to control treated cells”

ACAT1 inhibition was unable to increase Aβ42 uptake in LRP1 KO BV2 microglial cells compared to control cells.

“ACAT1 inhibition was unable to increase Aβ42 uptake in LRP1 KO BV2 microglial cells compared to control cells (Figure 4C).”

Recombinant sTREM2 rescues Aβ uptake in TREM2 KO BV2 cells.

“Treatment of microglial cells with sTREM2 rescues Aβ uptake in TREM2 KO BV2 cells.”

• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.
• AssumptionRests on an assumption: Recombinant sTREM2 added to culture medium functions equivalently to endogenously shed sTREM2.

Treatment with recombinant 40 nM sTREM2 led to no change in Aβ42 uptake in LRP1 KO cells treated with both GW280264X and AV, in contrast to WT BV2 cells.

“Finally, treatment with recombinant 40 nM sTREM2 led to no change in Aβ42 uptake in LRP1 KO cells treated with both GW280264X and AV, in contrast to the results from WT BV2 cells.”

ACAT1 inhibition increased Aβ uptake in both human iMGL and mouse BV2 microglial cells.

“Here, we demonstrated that ACAT1 inhibition increased Aβ uptake in both human iMGL and mouse BV2 microglial cells.”

LRP1 is required for microglial sTREM2-mediated Aβ uptake.

“We show that LRP1 is required for microglial sTREM2‐mediated Aβ uptake”

• AssumptionRests on an assumption: Recombinant sTREM2 added to culture medium functions equivalently to endogenously shed sTREM2.

WT iMGLs treated with AV exhibited a 122.6% increase in Aβ42 uptake compared to control treated TREM2 KO iMGLs.

“and a 122.6% increase compared to control treated TREM2 KO iMGLs.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

Addition of sTREM2 increased Aβ42 uptake in a concentration-dependent manner, with 40 nM, but not 20 nM sTREM2 significantly increasing Aβ42 uptake compared to control treated cells.

“The addition of sTREM2 increased Aβ42 uptake in a concentration‐dependent manner, with 40 nM, but not 20 nM sTREM2 significantly increasing Aβ42 uptake compared to control treated cells (Figure S1).”

ACAT1 inhibition enhanced ADAM10/17-mediated cleavage of TREM2, leading to increased shedding of sTREM2 into the media of AV treated microglial cells.

“Here, we observed that ACAT1 inhibition enhanced ADAM10/17‐mediated cleavage of TREM2, leading to increased shedding of sTREM2 into the media of AV treated microglial cells (Figure 3A).”

LRP1 KO BV2 cells treated with ADAM10/17 inhibitor GW280264X alone or combined with AV treatment revealed no change in Aβ42 uptake.

“Next, as observed in the WT BV2 cells, LRP1 KO BV2 cells treated with ADAM10/17 inhibitor, GW280264X, alone or combined with AV treatment, revealed no change in Aβ42 uptake.”

ACAT1 inhibition increases sTREM2 release via enhanced TREM2 cleavage by ADAM10/17.

“ACAT1 inhibition increased LRP1 levels and soluble TREM2 (sTREM2) release via enhanced TREM2 cleavage by ADAM metallopeptidase domain 10/17 (ADAM10/17).”

• Also stated in: § Highlights · plain

  “Inhibition of ACAT1 increases cleavage of TREM2 via ADAM10/17 to release sTREM2.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The ADAM10/17 inhibitor GW280264X specifically blocks TREM2 shedding without other effects.

In human iMGLs, 10 μM AV treatment for 24 h increased Aβ uptake by 95.5%.

“and increased Aβ uptake by 95.5% (Figure 1D).”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

sTREM2 levels were significantly increased by 17.3% in cell culture medium following AV treatment compared to control-treated cells.

“sTREM2 levels were significantly increased (17.3%) compared to control‐treated cells (Figure 3C).”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

AV-CM significantly increased Aβ42 uptake in CNT treated cells (82.9%) and AV treated cells (83.1%) compared to WT BV2 cells not treated with AV-CM (CNT CNT-CM).

“Analysis of Aβ42 uptake revealed AV‐CM significantly increased Aβ42 uptake in CNT treated cells (82.9%) and AV treated cells (83.1%) compared to WT BV2 cells, which were not treated with AV‐CM (CNT CNT‐CM) (Figure 3E).”

Blockade of sTREM2 release prevents AV-enhanced Aβ uptake.

“KO of TREM2 or blockade of sTREM2 release prevented AV‐enhanced Aβ uptake.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The ADAM10/17 inhibitor GW280264X specifically blocks TREM2 shedding without other effects.

ACAT1 inhibition increased LRP1 protein levels.

“Additionally, ACAT1 inhibition increased LRP1 protein levels (Figure 4B)”

LRP1 KO BV2 cells continued to exhibit no change in Aβ42 uptake when treated with 10 μM AV for 24 h.

“LRP1 KO BV2 cells continued to exhibit no change in Aβ42 uptake when treated with 10 µM AV for 24 h.”

Recombinant sTREM2 rescue of Aβ uptake requires LRP1.

“This effect was rescued by recombinant sTREM2, but only when LRP1 was present.”

• AssumptionRests on an assumption: Recombinant sTREM2 added to culture medium functions equivalently to endogenously shed sTREM2.

WT iMGLs treated with AV exhibited a 95.5% increase in Aβ42 uptake compared to control treated WT iMGLs.

“WT iMGLs treated with AV exhibited a 95.5% increase in Aβ42 uptake compared to control treated WT iMGLs”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

Decreased full-length TREM2 protein levels were observed in AV treated microglial cells undergoing impaired cholesterol storage.

“We provide further support for the role of TREM2 in enhanced microglial Aβ uptake following ACAT1 inhibition by showing decreased full‐length TREM2 protein levels in AV treated microglial cells undergoing impaired cholesterol storage (Figure 3).”

WT BV2 cells treated with 10 μM AV for 24 h exhibited significantly increased protein levels of LRP1 (102.7%) compared to DMSO CNT treated cells.

“First, we observed that WT BV2 cells treated with 10 µM AV for 24 h exhibited significantly increased protein levels of LRP1 (102.7%) compared to DMSO CNT treated cells (Figure 4A and B).”

A 24-h treatment with avasimibe (AV) decreases cholesteryl ester (CE) levels in WT BV2 microglial cells in a dose-dependent manner, with 2.5 μM and 5 μM AV decreasing CE by roughly 20% and 10 μM and 15 μM leading to an approximately 30% decrease compared to control.

“A 24‐h treatment with AV decreased CE levels at nearly all concentrations (Figure 1A) in a dose‐dependent manner, with 2.5 µM and 5 µM AV decreasing CE by roughly 20% and 10 µM and 15 µM leading to an ∼30% decrease in CE levels compared to control treated cells.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

TREM2 protein levels in LRP1 KO BV2 cells were significantly lower than in WT BV2 cells.

“we measured TREM2 protein levels in LRP1 KO BV2 cells and observed significantly lower levels of total TREM2 compared to WT BV2 cells (Figure S2A and B).”

No change in Aβ42 uptake in LRP1 KO BV2 cells following treatment with 40 nM recombinant sTREM2.

“Additionally, we observed no change in Aβ42 uptake in LRP1 KO BV2 cells following treatment with 40 nM recombinant sTREM2.”

In WT BV2 cells treated with 250 nM RAP 30 min prior to addition of Aβ42, Aβ42 uptake was significantly decreased.

“In WT BV2 cells treated with 250 nM RAP 30 min prior to the addition of Aβ42, we observed a significant decrease in Aβ42 uptake (Figure S3).”

When control WT BV2 cells were treated with WT AV CM together with RAP, AV-enhanced Aβ42 uptake was abrogated compared to control WT BV2 cells.

“Additionally, when control WT BV2 cells were treated with WT AV CM together with RAP, AV‐enhanced Aβ42 uptake was abrogated compared to control WT BV2 cells (Figure 4F).”

WT AV-CM significantly increased (43.9%) Aβ42 uptake in TREM2 KO BV2 cells compared to TREM2 KO cells treated with WT CNT-CM.

“WT AV‐CM significantly increased (43.9%) Aβ42 uptake in TREM2 KO BV2 cells compared to TREM2 KO cells treated with WT CNT‐CM (Figure 3F).”

Aβ42 uptake in LRP1 KO BV2 cells was significantly decreased (64.16%) compared to WT BV2.

“In Figure 4C, we show that Aβ42 uptake in LRP1 KO BV2 cells was significantly decreased (64.16%) compared to WT BV2.”

In human iMGLs, 10 μM AV treatment for 24 h decreased CE levels by 43.1%.

“In iMGLs, 10 µM AV treatment for 24 h decreased CE levels by 43.1% (Figure 1C)”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

TREM2 knockout abrogates the ability of AV to augment microglial Aβ42 uptake in iMGLs.

“TREM2 KO abrogated the ability of AV to augment microglial Aβ42 uptake as compared to WT cells (Figure 2B).”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

TREM2 KO clones B6 and E3 contained a +1 insertion at the Cas9 cleavage site, creating frameshift mutations that disrupted the TREM2 coding sequence.

“Both selected clones contained a +1 insertion at the Cas9 cleavage site, creating frameshift mutations that disrupted the TREM2 coding sequence.”

ACAT1 inhibition promotes microglial Aβ uptake in a sTREM2- and LRP1-dependent manner.

“ACAT1 inhibition promotes microglial Aβ uptake in a sTREM2‐ and LRP1‐dependent manner, offering insights into novel therapeutic strategies for AD.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: Recombinant sTREM2 added to culture medium functions equivalently to endogenously shed sTREM2.

Decreasing TREM2 protein levels is a suitable physiological response to protect cells with impaired cholesterol storage from further internalizing cholesterol-rich substances.

“While initially surprising, decreasing TREM2 protein levels is a suitable physiological response to protect cells with impaired cholesterol storage from further internalizing cholesterol‐rich substances.”

Following ACAT1 inhibition, LRP1 most likely serves as a major receptor for microglial uptake of Aβ42, via internalization of a sTREM2-Aβ complex.

“Taken together, these data suggest that following ACAT1 inhibition, LRP1 most likely serves as a major receptor for microglial uptake of Aβ42, via internalization of a sTREM2‐Aβ complex.”

At the concentration and treatment time used, processing of proteins involved in Aβ uptake (e.g., RP1) is not impacted in WT BV2 microglia by GW280264X.

“suggesting that, at this concentration and treatment time, processing of proteins involved in Aβ uptake, for example, RP1, are not impacted in WT BV2 microglia.”

When lipid-loaded microglia are treated with ACAT1 inhibitors, their ability to phagocytose Aβ improves.

“Furthermore, when lipid‐loaded microglia are treated with ACAT1 inhibitors, their ability to phagocytose Aβ improves. 15”

• cites [15] Nugent AA, Lin K, van Lengerich B, et al. TREM2 regulates microglial cholesterol metabolism upon chronic phagocytic challenge. Neuron. 2020; 105: 837– 854. e9. doi: 10.1016/j.neuron.2019.12.007 31902528 sourceNot checked yet

LRP1 is a receptor for the internalization of the sTREM2-Aβ complex.

“strongly suggesting LRP1 is a receptor for the internalization of the sTREM2–Aβ complex.”

ACAT1 inhibition promotes cleavage of membrane TREM2 and shedding of sTREM2 into the culture medium.

“Thus, ACAT1 inhibition promotes cleavage of membrane TREM2 and shedding of sTREM2 into the culture medium”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.

CM from AV treated cells is sufficient for augmenting Aβ42 uptake in microglia.

“These findings indicate that CM from AV treated cells is sufficient for augmenting Aβ42 uptake in microglia.”

• Also stated in: § DISCUSSION · plain

  “In support of this hypothesis, we showed that medium conditioned by WT BV2 microglial cells treated with an ACAT1 inhibitor was sufficient to increase Aβ uptake in WT BV2 cells, which had not been treated with an ACAT1 inhibitor (Figure 3E).”

Components in the medium following AV treatment are necessary for inducing increased uptake of Aβ42 in microglia.

“These data indicate that components in the medium following AV treatment are necessary for inducing increased uptake of Aβ42 in microglia.”

• Also stated in: § DISCUSSION · plain

  “Importantly, when we replaced the medium of ACAT1 inhibitor treated WT BV2 microglial cells with CM from control treated WT BV2 cells, Aβ uptake was no longer increased (Figure 3E).”

LRP1 is required/necessary for ACAT1 inhibition-enhanced microglial Aβ42 uptake.

“Taken together, these data indicate that LRP1 is required for AV‐mediated enhancement of microglial Aβ42 uptake.”

• Also stated in: § LRP1 is required for enhanced sTREM2‐mediated Aβ42 uptake following ACAT1 inhibition in microglia · hedged

  “Collectively, these data suggest that LRP1 is a crucial receptor for augmented microglial uptake of Aβ42 following ACAT1 inhibition.”

• Also stated in: § LRP1 is required for enhanced sTREM2‐mediated Aβ42 uptake following ACAT1 inhibition in microglia · boosted

  “Collectively, these findings show that LRP1 is necessary for AV‐induced enhancement of Aβ uptake in microglia and that the observed effects of decreased Aβ uptake in LRP1 KO BV2 cells are not due to decreased TREM2 levels.”

Microglia isolated from vulnerable brain regions in various neurodegenerative diseases, including LOAD, contain elevated ACAT1 (SOAT1) mRNA.

“In AD, microglia show elevated sterol O‐acyltransferase 1/Acyl‐coenzymeA: Choleseterol Acyltransferase 1 (SOAT1) expression, encoding Acyl‐coenzymeA: Cholesterol Acyltransferase 1 (ACAT1), which produces cholesteryl esters (CEs) in lipid droplets.”

• Also stated in: § BACKGROUND · plain

  “Finally, microglia isolated from vulnerable brain regions in various neurogenerative diseases, including LOAD, contain elevated levels of ACAT1 (sterol O‐acyltransferase 1 [SOAT1)]) mRNA. 9”

• cites [9] Li H, Huynh TN, Duong MT, Gow JG, Chang CCY, Chang TY. ACAT1/SOAT1 blockade suppresses LPS‐mediated neuroinflammation by modulating the fate of toll‐like receptor 4 in microglia. Int J Mol Sci. 2023; 24(6): 5616. doi: 10.3390/ijms24065616 36982689 PMC10053317 sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

The data presented are the first to reveal LRP1 as the receptor for the sTREM2-Aβ complex.

“To our knowledge, the data presented are the first to reveal LRP1 as the receptor for the sTREM2‐Aβ complex.”

Augmented uptake of Aβ42 by human iMGLs treated with ACAT1 inhibitors is dependent on the presence of TREM2.

“Collectively, these data demonstrate that augmented uptake of Aβ42 by human iMGLs treated with ACAT1 inhibitors is dependent on the presence of TREM2.”

• AssumptionRests on an assumption: Avasimibe's effects on Aβ uptake and TREM2 shedding are mediated specifically through ACAT1 inhibition, not through off-target effects.
• AssumptionRests on an assumption: The TREM2 KO iMGL and BV2 cells lack functional TREM2 protein.

Release of sTREM2 via ADAM10/17-mediated cleavage of membrane TREM2 is the major driver of increased Aβ uptake following ACAT1 inhibition in microglia.

“Taken together, these data strongly suggest that the release of sTREM2 via ADAM10/17‐mediated cleavage of membrane TREM2 is the major driver of increased Aβ uptake following ACAT1 inhibition in microglia.”

• Also stated in: § DISCUSSION · boosted

  “Collectively, these data establish that the shedding of TREM2 is the major driver of enhanced microglial uptake of Aβ following inhibition of ACAT1.”

Depletion of intracellular CE levels following ACAT1 inhibition with AV is responsible for the elevation in soluble factors that are released by microglia and enhance Aβ42 uptake.

“Furthermore, these data suggest that depletion of intracellular CE levels following ACAT1 inhibition with AV is responsible for the elevation in soluble factors that are released by microglia and enhance Aβ42 uptake.”

Inhibition of CE formation alters intracellular cholesterol homeostasis, resulting in increased ADAM10/17 activity.

“These findings suggest that inhibition of CE formation alters intracellular cholesterol homeostasis, resulting in increased ADAM10/17 activity.”