DR1 activation promotes vascular smooth muscle cell apoptosis via up-regulation of CSE/H S pathway in diabetic mice.

The important role of hydrogen sulfide (H S) as a novel gasotransmitter in inhibiting proliferation and promoting apoptosis of vascular smooth muscle cells (VSMCs) has been widely recognized. The dopamine D1 receptor (DR1), a G protein coupled receptor, inhibits atherosclerosis by suppressing VSMC proliferation. However, whether DR1 contributes to VSMC apoptosis via the induction of endogenous H S in diabetic mice is unclear. Here, we found that hyperglycemia decreased the expressions of DR1 and cystathionine-γ-lyase (CSE, a key enzyme for endogenous H S production) and reduced endogenous H S generation in mouse arteries and cultured VSMCs. DR1 agonist SKF38393 increased DR1 and CSE expressions and stimulated endogenous H S generation. Sodium hydrosulfide (NaHS, a H S donor) increased CSE expressions and H S generation but had no effect on DR1 expression. In addition, high glucose (HG) increased VSMC apoptosis, up-regulated IGF-1-IGF-1R and HB-EGF-EGFR, and stimulated ERK1/2 and PI3K-Akt pathways. Overexpression of DR1, the addition of SKF38393 or supply of NaHS further promoted VSMC apoptosis and down-regulated the above pathways. Knock out of CSE or the addition of the CSE inhibitor poly propylene glycol diminished the effect of SKF38393. Moreover, calmodulin (CaM) interacted with CSE in VSMCs; HG increased intracellular Ca concentration and induced CaM expression, further strengthened the interaction of CaM with CSE in VSMCs, which were further enhanced by SKF38393. CaM inhibitor W-7, inositol 1,4,5-trisphosphate (IP ) inhibitor 2-APB, or ryanodine receptor inhibitor tetracaine abolished the stimulatory effect of SKF38393 on CaM expression and intracellular Ca concentration. Taken together, these results suggest that DR1 up-regulates CSE/H S signaling by inducing the Ca -CaM pathway followed by down-regulations of IGF-1-IGF-1R and HB-EGF-EGFR and their downstream ERK1/2 and PI3K-Akt, finally promoting the apoptosis of VSMCs in diabetic mice.