PO-137 Epigenetic regulation of exercise-improved LTCC and BKCa channels function in hypertension mesenteric arteries

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Abstract

Objective To investigate the epigenetic mechanism of the voltage-gated L-type Ca²⁺ channel (LTCC) and the large-conductance Ca²⁺-activated K⁺ channel (BK_Ca) function in mesenteric arterial myocytes improved by regular aerobic exercise in hypertension.

Methods 12-week-old male SHR and WKY rats were randomly assigned to sedentary and exercise training groups, respectively. Exercise groups were performed a moderate-intensity treadmill running. After 8 weeks, patch clamp study, Ca²⁺ image, Western blot, qPCR, bisulfite sequencing PCR were used to detect the LTCC and BK_Ca channel currents, BK_Ca single channel gating properties, Ca²⁺ spark, mRNA and protein expression of LTCC α_1c together with BK_Ca α and β1 subunits, DNA methylation level of α_1c and β1 gene promoter region, miR-328 expression. In vitro experiment，miR-328 mimic and miR-328 inhibitor were transfected into cultured arterial myocytes to make miR-328 overexpressing or silencing, the mRNA and protein expression of α_1c subunits were determined after 48 h transfection.

Results 1) After 8 weeks of exercise, SBP in both exercise groups of WKY and SHR were significantly lower than that of their sedentary counterparts. 2) Exercise normalized the increased LTCC and BK_Ca current density of mesenteric arterial myocytes in SHR. 3) Exercise attenuated the increased single BK_Ca channel open Probability (Po) and the amplitude of Ca²⁺ spark in hypertension. 4) Exercise inhibited the upregulated mRNA and protein expression of BK_Ca β1 subunit in mesenteric arteries from SHR; β1 gene promoter was demethylation in hypertension, exercise increased the methylation level at β1 gene promoter of SHR. 5) The protein expression of LTCC α_1c subunit was significantly increased in SHR, while decreased by exercise; the expression of miR-328 in mesenteric arteries was highly negative correlation with α_1c subunit. 6) The miR-328 overexpression by transfecting miR-328 mimic decreased α_1c subunit protein level significantly, while miR-328 inhibitor made α_1c subunit a slight increase.

Conclusions Regular aerobic exercise efficiently reduces blood pressure of SHR, enhances β1 gene promoter methylation, mediates miR-328 inhibiting the α_1c expression at post-transcriptional level, which might be the epigenetic mechanism underlying exercise-improved LTCC and BK_Ca channels function in mesenteric arteries of hypertension.