Biology subjects

Rotllan, N.

Publications and source records attributed to Rotllan, N..

4 recordsLinked to original sources

bioRxiv2025

Restoring Cholesterol Efflux in Vascular Smooth Muscle Cells Transitioning into Foam Cells Through Liver X Receptor Activation

ObjectiveMacrophage foam cells derived from vascular smooth muscle cells (VSMCs) account for 30-70% of foam cells in atherosclerotic lesions. Liver X receptor (LXR) agonists promote high-density lipoprotein (HDL)-mediated cholesterol efflux from macrophages. This study aimed to investigate the effects of LXR activation on the reverse cholesterol transport (RCT) rate from VSMCs to feces in vivo. Approach and ResultsCholesterol efflux induced by serum and HDL was evaluated in human and mouse VSMCs treated with the LXR agonist T090137 before and after methyl-{beta}-cyclodextrin (MBD)-cholesterol loading. Additional experiments included treatment with an acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor. Cholesterol-radiolabeled VSMCs were injected into the peritoneal cavity of mice, and RCT was assessed by measuring radiolabeled cholesterol in serum, liver, and feces over 48 hours. Serum and HDL induced cholesterol efflux at similar levels in both human and mouse VSMCs. Cholesterol efflux was significantly reduced following MBD-cholesterol loading; however, treatment with the LXR agonist significantly enhanced efflux. Radiolabeled foam-like VSMCs injected into mice exhibited impaired cholesterol transfer to serum, HDL, and feces compared to non-lipid-laden VSMCs. Pre-treatment with the LXR agonist increased radiolabeled cholesterol levels in serum and HDL and doubled its fecal excretion. Additionally, LXR activation restored RCT from MBD-cholesterol-loaded VSMCs to feces, reaching levels comparable to those of non-lipid-laden cells. Treatment with an ACAT inhibitor fully restored RCT rates in foam-like VSMCs, and the combination of the ACAT inhibitor and the LXR agonist further enhanced RCT. ConclusionsHDL-mediated cholesterol efflux is significantly impaired in VSMCs during their transition into foam cells. Pharmacological activation of LXR enhances RCT from VSMCs to feces in vivo and restores the impaired RCT from transitioning VSMCs. The combination of LXR agonists and ACAT inhibitors holds promise as a synergistic therapeutic approach to restoring cholesterol homeostasis in lipid-laden VSMCs, offering potential strategies to mitigate atherosclerosis. HighlightsO_LILXR activation enhances cholesterol efflux in VSMCs in vitro, even after their transition into foam cells. C_LIO_LIVSMCs transitioning into foam cells exhibit reduced cholesterol transfer to HDL and feces in mice. C_LIO_LILXR agonist treatment enhances reverse cholesterol transport (RCT) from VSMCs to feces in vivo. C_LIO_LISelective ACAT inhibition restores RCT in foam-like VSMCs, with further enhancement observed upon LXR activation. C_LI

biochemistry↗

bioRxiv2022

The immunodominant protein P116 is a passive transporter of cholesterol and other essential lipids

Many human pathogens need to extract lipids from their environment for survival and proliferation. How this is accomplished on a molecular level is largely unknown1. Here, we report a comprehensive structural and functional analysis of the previously uncharacterized protein P116 (MPN_213) from Mycoplasma pneumoniae, a human pathogen responsible for approximately 30% of community-acquired human pneumonia2. Single-particle cryo-electron microscopy of P116 at 3.3 [A] resolution reveals a homodimer with a core domain presenting a previously unseen fold. This fold creates a large cavity of [~]18,000 [A]3 with a hydrophobic internal surface that is accessible to solvent. Within the cavity ligands with a length of 10-19 [A] and a width of 4 [A] could be observed. These ligands were identified as the essential lipids phosphatidylcholine, sphingomyelin and cholesterol using mass spectrometry. When the cavity is emptied, the protein undergoes an extensive conformational change that can no longer accommodate lipids. When emptied P116 is incubated with high-density lipoproteins (HDLs) a net transfer of cholesterol is demonstrated by a radioactivity experiment and cryo-electron microscopy resolves a complex between P116 and HDL. Taken together, our results reveal the mechanism by which P116 extracts essential lipids from the host environment and possibly then delivers them into the membrane by a wringing movement. This mechanism may be precedential for other cholesterol-auxotrophic bacteria.

microbiology↗

bioRxiv2022

Bone marrow age dictates clonality of smooth muscle-derived cells in the atherosclerotic plaque

Aging is the predominant risk factor for atherosclerosis, the leading cause of death. Rare smooth muscle cell (SMC) progenitors clonally expand giving rise to up to [~]70% of atherosclerotic plaque cells; however, the effect of age on SMC clonality is not known. Our results indicate that aged bone marrow (BM)-derived cells non-cell autonomously induce SMC polyclonality and worsen atherosclerosis. Indeed, in myeloid cells from aged mice and humans, TET2 levels are reduced which epigenetically silences integrin {beta}3 resulting in increased tumor necrosis factor [TNF]- signaling. In turn, TNF signals through TNF receptor 1 on SMCs to promote proliferation and induces recruitment and expansion of multiple SMC progenitors into the atherosclerotic plaque. Notably, integrin {beta}3 overexpression in aged BM preserves dominance of the lineage of a single SMC progenitor and attenuates plaque burden. Our results demonstrate a molecular mechanism of aged macrophage-induced SMC polyclonality and atherogenesis and suggest novel therapeutic strategies. Graphical abstractAge of BM-derived monocytes/macrophages determines clonality of SMC lineage in the atherosclerotic plaque. Atherogenesis is depicted in a young (a) or aged (b) host. Aged monocytes/macrophages have decreased levels of the epigenetic regulator TET2, leading to reduction of the 5-hydroxymethylcytosine (5hmC) mark on the Itgb3 promoter. The resulting low integrin {beta}3 levels in aged monocytes/macrophages induces high TNF- levels, facilitating recruitment and expansion of multiple SMC progenitors (polyclonality) in the atherosclerotic plaque and worse disease burden. In contrast, the young control is characterized by mono/oligoclonal SMC expansion in a smaller plaque. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/476756v2_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@12f7090org.highwire.dtl.DTLVardef@186ff92org.highwire.dtl.DTLVardef@1f4da69org.highwire.dtl.DTLVardef@2f509c_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2020

Liver-specific suppression of ANGPTL4 improves obesity-associated diabetes and mitigates atherosclerosis in mice

ABSTRACTAngiopoietin-like 4 (ANGPTL4) is a major regulator of lipoprotein lipase (LPL) activity, which is responsible for maintaining optimal levels of circulating triacylglycerol (TAG) for distribution to different tissues including the adipose tissues (ATs), heart, muscle and liver. Dysregulation of trafficking and portioning of fatty acids (FA) can promote ectopic lipid accumulation in metabolic tissues such as the liver, ultimately leading to systemic metabolic dysfunction. To investigate how ANGPTL4 regulates hepatic lipid and glucose metabolism, we generated liver-specific ANGPTL4 knockout mice (LKO). Using metabolic turnover studies, we demonstrate that hepatic ANGPTL4 deficiency facilitates catabolism of TAG-rich lipoprotein (TRL) remnants in the liver via increased hepatic lipase (HL) activity, which results in a significant reduction in circulating TAG and cholesterol levels. Deletion of hepatocyte ANGPTL4 protects against diet-induce obesity, glucose intolerance, liver steatosis, and atherogenesis. Mechanistically, we demonstrate that absence of ANGPTL4 in hepatocytes promotes FA uptake which results in increased FA oxidation, ROS production, and AMPK activation. Finally, we demonstrate the utility of a targeted pharmacologic therapy that specifically inhibits ANGPTL4 in the liver and protects against diet-induced obesity, dyslipidemia, glucose intolerance, and liver damage without causing any of the deleterious effects previously observed with neutralizing antibodies.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗