Capsaicin Inhibits Angiotensin II Induced Vasoconstriction in Mice

Objective To study the long-term effect of administration(6 months) with transient receptor potential vanilloid 1(TRPV1) agonist capsaicin on contractile reactivity of thoracic aorta in C57BL/6J mice.Methods Tow-month-old male C57BL/6J mice were received normal diet group(n=12) or capsaicin group(normal diet plus capsaicin,n=12).Tail-cuff systolic blood pressure(SBP) was examined at the baseline and at the end of the intervention.After 6-month treatment period,carotid artery blood pressure and heart rate were determined by catheterization,and the aortic contractile response was examined using isometric myograph(Danish Myotech Technology,Denmark).Plasma levels of renin,angiotensin Ⅱ(Ang Ⅱ) and aldosterone were determined.Vascular smooth muscle cells(VSMC) were obtained from thoracic aorta of mice and cultured.Angiotensin Ⅱ type 1 receptor(AT1R) protein expression was detected by western blot.Calcium imaging was detected in cultured VSMC using the fluorescent dye technique.Results Systolic blood pressure,invasive carotid artery blood pressure and heart rate have no difference between two groups.No differences was found in PE-induced contraction response in thoracic aorta;while Ang Ⅱ induced contractility of aortic ring was lower in mice with capsaicin than control group [capsaicin:(37.5±1.6)% vs(59.8±1.4)%,P0.05].Capsaicin significantly reduced AT1R protein expression to only(62.4 ±16.6)% level of control and decreased Ang Ⅱ-induced calcium entry in cultured VSMC [capsaicin:(0.91±0.12) vs(1.37±0.35),P0.05] with no differences in plasma renin Ang Ⅱ and aldosterone between the two groups.Conclusion Long-term dietary capsaicin significantly bluntes Ang Ⅱ induced contraction response in aortic segments,which may attribute to the down-regulation of AT1R expression and reduction of Ang Ⅱ-induced calcium entry in VSMC.