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While the tdTomato SP + sp cells were exclusively macrophages at 16 weeks old, we next asked whether SMCs-derived macrophages are terminally differentiated or being in an intermittent state in which they could further adopt other cell fate(s) in the advanced atherosclerotic plaques at 32 weeks old. Our findings suggested that while a subset of SMC-derived macrophage-like cells continued to be macrophage-like cells in the advanced plaques, the majority of them did not continue to express macrophage markers at late stage. Our study provided direct genetic evidence of conversion of the SMC-derived macrophage-like cells to cells expressing other cell lineage markers in plaques. [Extracted from the article]

Background and Purpose: Atherosclerosis is a chronic inflammatory disease, and retinoid X receptor-α (RXRα) is an intriguing anti-atherosclerosis target. This study investigated whether and how an RXRα modulator, K-80003, derived from a non-steroidal anti-inflammatory drug attenuates atherosclerotic plaque progression and destabilization.Experimental Approach: Our previously established ApoE-/- mouse model of carotid vulnerable plaque progression was treated with K-80003 or vehicle for 4 or 8 weeks. Samples of carotid arteries and serum were collected to determine atherosclerotic lesion size, histological features, expression of related proteins, and lipid profiles. In vitro studies were carried out in 7-ketocholesterol (7-KC)-stimulated macrophages treated with or without K-80003.Key Results: K-80003 significantly reduced lesion size, plaque rupture, macrophage infiltration, and inflammatory cytokine levels. Plaque macrophages positive for nuclear p65 (RelA) NF-κB subunit were markedly reduced after K-80003 treatment. Also, K-80003 treatment inhibited 7-KC-induced p65 nuclear translocation, IκBα degradation, and transcription of NF-κB target genes. In addition, K-80003 inhibited NF-κB pathway mainly through the reduction of p62/sequestosome 1 (SQSTM1), probably due to promotion of autophagic flux by K-80003. Mechanistically, cytoplasmic localization of RXRα was associated with decreased autophagic flux. Increasing cytoplasmic RXRα expression by overexpression of RXRα/385 mutant decreased autophagic flux in RAW264.7 cells. Finally, K-80003 strongly inhibited 7-KC-induced RXRα cytoplasmic translocation.Conclusions and Implications: K-80003 suppressed atherosclerotic plaque progression and destabilization by promoting macrophage autophagic flux and consequently inhibited the p62/SQSTM1-mediated NF-κB proinflammatory pathway. Thus, targeting RXRα-mediated autophagy-inflammation axis by its noncanonical modulator may represent a promising strategy to treat atherosclerosis. [ABSTRACT FROM AUTHOR]

It is well documented that statins protect atherosclerotic patients from inflammatory changes and plaque instability in coronary arteries. However, the underlying mechanisms are not fully understood. Using a previously established mouse model for vulnerable atherosclerotic plaque, we investigated the effect of atorvastatin (10 mg/kg/day) on plaque morphology. Atorvastatin did not lower plasma total cholesterol levels or affect plaque progression at this dosage; however, vulnerable plaque numbers were significantly reduced in the atorvastatin-treated group compared to control. Detailed examinations revealed that atorvastatin significantly decreased macrophage infiltration and subendothelial lipid deposition, reduced intimal collagen content, and elevated collagenase activity and expression of matrix metalloproteinases (MMPs). Because vascular inflammation is largely driven by changes in monocyte/macrophage numbers in the vessel wall, we speculated that the anti-inflammatory effect of atorvastatin may partially result from decreased monocyte recruitment to the endothelium. Further experiments showed that atorvastatin downregulated expression of the chemokines monocyte chemoattractant protein (MCP)-1, chemokine (C-X3-C motif) ligand 1 (CX3CL1) and their receptors CCR2 and, CX3CR1, which are mainly responsible for monocyte recruitment. In addition, levels of the plasma inflammatory markers C-reactive protein (CRP) and tumor necrosis factor (TNF)-α were also significantly decrease in atorvastatin-treated mice. Collectively, our results demonstrate that atorvastatin can improve plaque stability in mice independent of plasma cholesterol levels. Given the profound inhibition of macrophage infiltration into atherosclerotic plaques, we propose that statins may partly exert protective effects by modulating levels of chemokines and their receptors. These findings elucidate yet another atheroprotective mechanism of statins. [ABSTRACT FROM AUTHOR]

Aims: Endothelial inflammation is crucial in the initiation and progression of atherosclerosis, whereas cholesterol crystals (CCs) play a key role in atherogenesis. However, the effects and origination of CCs on endothelial inflammation are not well understood. Results: In the present study, we found that CCs appeared in the subendothelial space of the partially ligated carotid artery only 1 week after Western diet feeding, which was before immune cell infiltration. In vitro, CCs were generated by human aortic endothelial cells (HAECs) upon low-density lipoprotein treatment. These endothelial cell (EC)-derived CCs increased the expression of intercellular cell adhesion molecule-1 (ICAM1) and vascular cell adhesion molecule-1 (VCAM1). Mechanistic studies demonstrated that CC-induced pyroptosis was critical for endothelial inflammation. Knockdown of gasdermin D (GSDMD) inhibited CC-induced endothelial inflammation, attenuated plaque progression, and decreased macrophage content. Accordingly, the inhibition of GSDMD reduced the CC-induced increase of VCAM1 and ICAM1 in HAECs. Furthermore, CC-mediated pyroptosis was found to be caspase-1 (CASP1)-dependent. Inhibition of CASP1 also reduced endothelial inflammation and attenuated plaque progression. The expression of GSDMD was increased in human atherosclerotic plaques. These findings identify that EC-derived CCs may be an important driving force in the pathogenesis of atherosclerosis. Innovation: This study uncovered a new understanding that CC-induced pyroptosis contributes to endothelial inflammation in early atherogenesis. Conclusion: Targeting endothelial GSDMD or CASP1 contributes to the repression of vascular inflammation and atherogenesis. Antioxid. Redox Signal. 41, 201–215. [ABSTRACT FROM AUTHOR]

Purpose: Autophagy inhibition is a novel therapeutic strategy suggested for patients with advanced cancer, especially those who have undergone radiation therapy. In the present study, we investigated whether autophagy inhibitors accelerate the progression of radiation-associated atherosclerosis (RAA).Methods and Materials: Eight-week-old apolipoprotein (ApoE-/-) mice were fed a Western diet, and their left common carotid arteries were partially ligated to induce atherogenesis. Four weeks later, local ionizing radiation (IR) at a dose of 5 or 10 Gy was used to induce RAA in the left common carotid artery. After another 4 weeks, severe plaque burden associated with increased macrophage infiltration and lipid deposition, reduced smooth muscle cells, and decreased collagen expression was observed. In addition, these changes occurred in a dose-dependent manner. Improved autophagic flux caused by IR was observed in both macrophages of the atherosclerotic plaque and peritoneal macrophages in vitro. The inhibition of autophagic flux by chloroquine (50 mg/kg/d) further accelerated the progression of RAA in the left common carotid arteries of ApoE-/- mice. Furthermore, chloroquine treatment exacerbated IR-induced p65 nuclear translocation, IκBα degradation, and transcription of nuclear factor-κB (NF-κB) target genes in peritoneal macrophages.Conclusions: IR promotes atherogenesis and increases autophagic flux. In addition, autophagy inhibition by chloroquine accelerates the progression of RAA lesions by stimulating NF-κB-mediated inflammatory responses in macrophages. [ABSTRACT FROM AUTHOR]