Capsaicin ameliorates intermittent high glucose-mediated endothelial senescence via the TRPV1/SIRT1 pathway

Abstract

Background: Patients with diabetes have accelerated vascular aging when compared with healthy individuals. Hyperglycemia, especially intermittent high glucose (IHG), is the main cause of vascular endothelial senescence. Capsaicin, a major component of chili pepper is thought to contribute to cardiovascular protection by spicy food.

Objective: To investigate the pathway related with the effects of capsaicin on endothelial cell senescence induced by IHG.

Methods: HUVECs were exposed to IHG (5 mM or 33 mM glucose, alternating every 12 hours for 3 days) and treated with capsaicin at 0.3, 1 and 3 μM. To determine endothelial cell senescence, we examined the senescence-related β-galactosidase staining, cell cycle arrest, cell viability, as well as production of reactive oxygen species (ROS). To evaluate the involvement of TRPV1/[Ca²⁺]i/CaMKII/AMPK/SIRT1 pathway in anti- senescence effects of capsaicin, HUVECs were treated with CAPZ (a TRPV1 antagonist), BAPTA-AM (an intracellular calcium chelator), KN62 (a CaMKII antagonist), compound C (an AMPK inhibitor), or EX527 (a SIRT1 inhibitor). To knockdown TRPV1, HUVECs were transfected with shRNA lentivirus targeting TRPV1. The levels of SIRT1, p21, TRPV1, AMPK and phospho-AMPK were evaluated by western blotting.

Results: IHG suppressed the levels of SIRT1 and enhanced endothelial senescence. Capsaicin upregulated SIRT1 expression and downregulated the senescence marker, p21, thereby protecting endothelial cells from IHG-induced senescence as indicated by relieved G0/G1 phase arrest, improved cell viabilities, and reduced counts of senescent cells and ROS production. Pre-treatment with CAPZ, BAPTA-AM, KN62 or compound C abrogated the anti-senescence effects of capsaicin. Capsaicin restored AMPK phosphorylation and IHG-inhibited TRPV1 expression. Moreover, TRPV1 silencing suppressed SIRT1 expression and abolished the anti-senescence effects of capsaicin.

Conclusion: Capsaicin elevates SIRT1 levels through TRPV1/[Ca²⁺]i/CaMKII/AMPK pathway and suppresses IHG-mediated endothelial cell senescence. This study provides initial evidence that capsaicin is a potential candidate for the prevention of vascular aging in diabetes.

Keywords: Capsaicin; Endothelial senescence; Intermittent high glucose; SIRT1; TRPV1.