Biology subjects

Ouimet, M.

Publications and source records attributed to Ouimet, M..

5 recordsLinked to original sources

bioRxiv2025

Postoperative Stress Accelerates Atherosclerosis through Inflammatory Remodeling of the HDL Proteome and Impaired Reverse Cholesterol Transport

BACKGROUNDOver 10 million patients undergoing non-cardiac surgery annually experience major cardiovascular complications within 30 days, many due to destabilized atherosclerotic plaques. Reverse cholesterol transport (RCT), a key pathway for cholesterol removal by HDL and apoA-I, is critical in preventing plaque progression. While surgery-induced inflammation is known to impair HDL function, its effects on RCT and plaque stability remain unclear. METHODSTo isolate the impact of surgical inflammation, independent of blood loss, we developed an abdominal laparotomy model in apoE-/- mice on a Western diet, minimizing blood loss and avoiding perioperative blood sampling. We assessed plasma cholesterol efflux capacity, performed proteomic analysis of HDL, and analyzed atherosclerotic plaques for lipid content, perilipin-2 (PLIN2), cleaved-caspase-3 (c-Casp-3), and necrotic core expansion. A novel dual-label, dual-cell-type in vivo RCT model was developed to compare RCT from macrophage-derived (BMDMs) and vascular smooth muscle cells (VSMCs)-derived foam cells. Recombinant apoA-I (rApoA-I) was tested for therapeutic rescue of impaired RCT. RESULTSSurgery significantly reduced RCT for at least 48 hours, paralleled by a drop in cholesterol efflux capacity and inflammatory remodeling of HDL, marked by elevated serum amyloid A (SAA1/2) and reduced apoA-I. Plaques showed a 1.6-fold increase in intracellular lipids and PLIN2 expression at 24 hours post-surgery, with elevated c-Casp-3 indicating lipid-driven apoptosis. Foam cell analysis revealed increased PLIN2 in both CD45+ (leukocyte) and CD45- (non-leukocyte) subtypes, with leukocyte foam cells expressing higher PLIN2. c-Casp-3+ apoptotic cells were predominantly PLIN2high and of both leukocytic and non-leukocytic origin. By day 15, the necrotic core area increased by 1.5-fold with sustained loss of plaque cellularity. Using our dual-cell-type RCT model, we found that surgery significantly impaired BMDM RCT in vivo, while VSMC RCT remained largely unaffected, highlighting foam cell subtype-specific vulnerability to surgical inflammation. These findings were mirrored in general surgery patients, whose postoperative plasma exhibited markedly reduced cholesterol efflux capacity. In mice, rApoA-I treatment partially restored RCT and reduced plaque lipid accumulation. CONCLUSIONSSurgical inflammation acutely impairs HDL function and RCT, triggering lipid accumulation, foam cell apoptosis, and accelerated plaque destabilization independent of blood loss. Immediate restoration of apoA-I at the time of surgery, aiming to counteract the acute phase response, may offer a targeted strategy to reduce postoperative cardiovascular risk.

biochemistry↗

bioRxiv2025

A Rosella-PLIN2 Knock-in Mouse Reveals Lipophagy and Immunometabolic Interplay in Atherosclerosis

Cytosolic lipid droplets (LDs) regulate lipid homeostasis, with abnormal LD dynamics linked to metabolic diseases like atherosclerosis. In macrophage foam cells, LDs undergo autophagic degradation via lipophagy, but the extent of this process in vascular smooth muscle cell (VSMC) foam cells remains unclear. To track lipophagy in real time, we developed a Rosella-PLIN2 biosensor by tagging perilipin 2 (PLIN2) with the fluorescent pH-biosensor Rosella. We show that proatherogenic lipoproteins and autophagy activators stimulate lipophagy in human macrophages. Targeting LDs with an LC3 fusion protein or LD-autophagy tethering compounds (LD-ATTECs) selectively enhanced lipophagy, promoting foam cell LD clearance. In an atherosclerosis model, Rosella-PLIN2 accurately tracked lipophagy in arterial foam cells, revealing distinct PLIN2 expression patterns in macrophage and non-leukocyte foam cells. We identified a lipophagy deficiency in VSMC foam cells and demonstrate that enhancing lipophagy promotes LD catabolism in primary VSMC foam cells. TREM2+ macrophages exhibited high lipid content and low lipophagy flux, whereas TREM2- macrophages had low lipid content and high lipophagy flux. Our findings highlight a cell-specific interplay between lipophagy and immunometabolism in arterial foam cells, unveiling novel therapeutic avenues for atherosclerosis. Additionally, the Rosella-PLIN2 model provides a powerful tool for studying LD metabolism, offering new insights into lipid homeostasis and disease mechanisms.

cell biology↗

bioRxiv2020

Foam cell induction activates AMPK but uncouples its regulation of autophagy and lysosomal homeostasis

The dysregulation of macrophage lipid metabolism drives atherosclerosis. AMP-activated protein kinase (AMPK) is a master regulator of cellular energetics and plays essential roles regulating macrophage lipid dynamics. Here, we investigated the consequences of atherogenic lipoprotein-induced foam cell formation on downstream immunometabolic signaling in primary mouse macrophages. A variety of atherogenic low-density lipoproteins (acetylated, oxidized and aggregated forms) activated AMPK signaling in a manner that was in part, due to CD36 and calcium-related signaling. In quiescent macrophages, basal AMPK signaling was crucial for maintaining markers of lysosomal homeostasis, as well as levels of key components in the lysosomal expression and regulation network. Moreover, AMPK activation resulted in targeted up-regulation of members of this network via transcription factor EB. However, in lipid-induced macrophage foam cells, neither basal AMPK signaling nor its activation affected lysosomal-associated programs. These results suggest that while the sum of AMPK signaling in cultured macrophages may be anti-atherogenic, atherosclerotic input dampens the regulatory capacity of AMPK signaling.

cell biology↗

bioRxiv2019

Fatty acid oxidation impairs macrophage effector functions that control Mycobacterium tuberculosis

Macrophage activation involves metabolic reprogramming to support antimicrobial cellular functions. How these metabolic shifts influence the outcome of infection by intracellular pathogens remains incompletely understood. M. tuberculosis (Mtb) modulates host metabolic pathways and utilizes host nutrients, including cholesterol and fatty acids, to survive within macrophages. We found that intracellular growth of Mtb depends on host fatty acid catabolism: when host fatty acid {beta}-oxidation (FAO) was blocked chemically with trimetazidine, a compound in clinical use, or genetically by deletion of the mitochondrial fatty acid transporter carnitine palmitoyltransferase 2 (CPT2), Mtb failed to grow in macrophages and its growth was attenuated in mice. Global metabolic profiling and mechanistic studies support a model in which inhibition of FAO generates mitochondrial reactive oxygen species, which enhance macrophage NADPH oxidase and xenophagy activity to better control Mtb infection. Thus, FAO inhibition promotes key antimicrobial functions of macrophages and overcomes immune evasion mechanisms of Mtb.

microbiology↗

bioRxiv2019

Loss of MLKL Decreases Necrotic Core but Increases Macrophage Lipid Accumulation In Atherosclerosis

ObjectivesDuring the advancement of atherosclerosis, the cellularity of the plaque is governed by the influx of monocyte-derived macrophages and their turnover via apoptotic and non-apoptotic forms of cell death. Previous reports have demonstrated that programmed necrosis, or necroptosis, of macrophages within the plaque contribute to necrotic core formation. Knockdown or inhibition of the necrosome components RIPK1 and RIPK3 slow the progression of atherosclerosis, and activation of the terminal step of necroptosis, MLKL, has been demonstrated in advanced human atherosclerotic plaques. However, whether MLKL directly contributes to lesion development and necrotic core formation has not been investigated.\n\nApproaches and ResultsMLKL expression was knocked down in atherogenic Apoe- knockout mice via subcutaneous administration of antisense oligonucleotides (ASO). During advanced atherogenesis, Mlkl knockdown potently reduced cell death in the plaque, with a significant reduction in the necrotic core. However, total lesion area in the aortic sinus remained unchanged. Furthermore, treatment with the MLKL ASO unexpectedly reduced circulating cholesterol levels compared to control ASO, while staining for lipids within the plaque was significantly increased. Peritoneal macrophages transfected with the MLKL ASO showed increased lipid loading upon incubation with modified cholesterol-rich lipoproteins. In lipid-loaded macrophages, MLKL co-localized with Rab7, a marker of the late endosome.\n\nConclusionsThese studies confirm the requirement for MLKL as the executioner of necroptosis, and as such a significant contributor to the necrotic core during atherogenesis. We also identified a previously unknown role for MLKL in interacting with endosomal trafficking components to regulate lipid uptake in macrophages during atherogenesis.

pathology↗