4‐HNE modified TRPV1 dysfunction leads to loss of capsaicin‐mediated eNOS activity and microvascular dysfunction

Abstract

Our lab has previously demonstrated enhanced 4‐hydroxynonenal (4‐HNE) post‐translational modification (PTM) of TRPV1 decreases TRPV1 functional expression and contributes to microvascular dysfunction in diabetes. Furthermore, recent studies have shown TRPV1 activation elicits eNOS activation and NO production. Accordingly, we hypothesize that the enhanced 4‐HNE‐mediated PTM of TRPV1 contributes to diabetic microvascular dysfunction in db/db mice via decreased eNOS activation and resultant signaling. Contrast echocardiography demonstrated that 4‐HNE decreased capsaicin mediated increases in myocardial blood flow and decreased capsaicin‐mediated relaxation in isolated coronary microvessels. TRPV1 functional analysis using calcium imaging revealed blunted capsaicin‐mediated calcium influx in the presence of 4‐HNE in isolated mouse coronary endothelial cells (MCECs). Finally, 4‐HNE treatment of MCECs decreased eNOS phosphorylation at Ser1197 leading to decreased measure in capsaicin‐mediated nitrate production. Single point mutation, of a pore region cysteine residue 621, rescued channel activity and preserved capsaicin‐mediated eNOS phosphorylation and NO production. These data suggest that TRPV1 is targeted by redox‐active substances that directly modulate channel activity at numerous sites in diabetes to decrease TRPV1 functional expression and contribute to microvascular dysfunction. The results obtained demonstrate a signaling pattern aberrant in TRPV1 regulation of vascular control in diabetes.