Rivaroxaban, a Direct Oral Factor Xa Inhibitor, Attenuates Atherosclerosis by Alleviating Factor Xa-PAR2-Mediated Autophagy Suppression

The authors showed a mechanism for attenuating atherosclerosis by directly administering an oral factor Xa inhibitor (ie, rivaroxaban [RIV]). The autophagy activity of macrophages was significantly suppressed by factor Xa and was alleviated by the administration of RIV. However, factor Xa failed to inhibit 7-ketocholesterol-induced autophagy and inflammasome activation in protease-activated receptor 2 (PAR2) knockout macrophages. The atherosclerotic area of apolipoprotein E knockout mice was significantly reduced by the genetic ablation of PAR2, which was partially reversed by chloroquine. Thus, the authors found that RIV attenuates atherogenesis by inhibiting the factor Xa-PAR2-mediated suppression of macrophage autophagy and abrogating inflammasome activity.

Adaptive responses induced by 24S-hydroxycholesterol through liver X receptor pathway reduce 7-ketocholesterol-caused neuronal cell death

Lipid peroxidation products have been known to induce cellular adaptive responses and enhance tolerance against subsequent oxidative stress through up-regulation of antioxidant compounds and enzymes. 24S-hydroxycholesterol (24SOHC) which is endogenously produced oxysterol in the brain plays an important role in maintaining brain cholesterol homeostasis. In this study, we evaluated adaptive responses induced by brain-specific oxysterol 24SOHC in human neuroblastoma SH-SY5Y cells. Cells treated with 24SOHC at sub-lethal concentrations showed significant reduction in cell death induced by subsequent treatment with 7-ketocholesterol (7KC) in both undifferentiated and retinoic acid-differentiated SH-SY5Y cells. These adaptive responses were also induced by other oxysterols such as 25-hydroxycholesterol and 27-hydroxycholesterol which are known to be ligands of liver X receptor (LXR). Co-treatment of 24SOHC with 9-cis retinoic acid, a retinoid X receptor ligand, enhanced the adaptive responses. Knockdown of LXRβ by siRNA diminished the adaptive responses induced by 24SOHC almost completely. The treatment with 24SOHC induced the expression of LXR target genes, such as ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1). The 24SOHC-induced adaptive responses were significantly attenuated by siRNA for ABCG1 but not by siRNA for ABCA1. Taken together, these results strongly suggest that 24SOHC at sub-lethal concentrations induces adaptive responses via transcriptional activation of LXR signaling pathway, thereby protecting neuronal cells from subsequent 7KC-induced cytotoxicity.

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24SOHC induces adaptive responses against 7KC-induced cell death in neuronal cells.

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Co-treatment of 24SOHC with 9cRA, an RXR ligand enhances adaptive responses.

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Knockdown of LXRβ suppresses 24SOHC-induced adaptive responses.

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ABCG1 is involved in LXR-mediated adaptive responses by 24SOHC.