capsazepine and Atherosclerosis

The transient receptor potential vanilloid type 1 (TRPV1) is crucial in the pathogenesis of atherosclerosis; yet its role and underlying mechanism in the formation of macrophage foam cells remain unclear. Here, we show increased TRPV1 expression in the area of foamy macrophages in atherosclerotic aortas of apolipoprotein E-deficient mice. Exposure of mouse bone-marrow-derived macrophages to oxidized low-density lipoprotein (oxLDL) upregulated the expression of TRPV1. In addition, oxLDL activated TRPV1 and elicited calcium (Ca(2+)) influx, which were abrogated by the pharmacological TRPV1 antagonist capsazepine. Furthermore, oxLDL-induced lipid accumulation in macrophages was ameliorated by TRPV1 agonists but exacerbated by TRPV1 antagonist. Treatment with TRPV1 agonists did not affect the internalization of oxLDL but promoted cholesterol efflux by upregulating the efflux ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Moreover, the upregulation of ABC transporters was mainly through liver X receptor α-(LXRα-) dependent regulation of transcription. Moreover, the TNF-α-induced inflammatory response was alleviated by TRPV1 agonists but aggravated by the TRPV1 antagonist and LXR α siRNA in macrophages. Our data suggest that LXR α plays a pivotal role in TRPV1-activation-conferred protection against oxLDL-induced lipid accumulation and TNF-α-induced inflammation in macrophages.

Topics: Animals; Atherosclerosis; Blotting, Western; Calcium; Capsaicin; Cells, Cultured; Chromatin Immunoprecipitation; Inflammation; Lipoproteins, LDL; Liver X Receptors; Macrophages; Mice; Orphan Nuclear Receptors; RNA, Small Interfering; TRPV Cation Channels; Tumor Necrosis Factor-alpha

We investigated the molecular mechanism underlying the role of transient receptor potential vanilloid type 1 (TRPV1), a Ca(2+)-permeable non-selective cation channel, in the activation of endothelial nitric oxide (NO) synthase (eNOS) in endothelial cells (ECs) and mice.. In ECs, TRPV1 ligands (evodiamine or capsaicin) promoted NO production, eNOS phosphorylation, and the formation of a TRPV1-eNOS complex, which were all abrogated by the TRPV1 antagonist capsazepine. TRPV1 ligands promoted the phosphorylation of Akt, calmodulin-dependent protein kinase II (CaMKII) and TRPV1, and increased the formation of a TRPV1-Akt-CaMKII complex. Removal of extracellular Ca(2+) abolished the ligand-induced increase in the phosphorylation of Akt and CaMKII, formation of a TRPV1-eNOS complex, and eNOS activation. Inhibition of PI3K and CaMKII suppressed the ligand-induced increase in TRPV1 phosphorylation, formation of a TRPV1-eNOS complex, and eNOS activation. TRPV1 activation increased the phosphorylation of Akt, CaMKII, and eNOS in the aortas of wild-type mice but failed to activate eNOS in TRPV1-deficient aortas. Additionally, TRPV1 ligand-induced angiogenesis was diminished in eNOS- or TRPV1-deficient mice. When compared with apolipoprotein E (ApoE)-deficient mice, ApoE/TRPV1-double-knockout mice displayed reduced phosphorylation of eNOS, Akt, and CaMKII in aortas but worsened atherosclerotic lesions.. TRPV1 activation in ECs may trigger Ca(2+)-dependent PI3K/Akt/CaMKII signalling, which leads to enhanced phosphorylation of TRPV1, increased TRPV1-eNOS complex formation, eNOS activation and, ultimately, NO production.

Topics: Animals; Apolipoproteins E; Atherosclerosis; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Capsaicin; Cattle; Cells, Cultured; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelial Cells; Enzyme Activation; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphatidylinositol 3-Kinase; Phosphorylation; Proto-Oncogene Proteins c-akt; Quinazolines; RNA Interference; Signal Transduction; Time Factors; Transfection; TRPV Cation Channels