Figure 4.

Knockdown of GPR4 reduces acidosis-induced GPR4 and CHOP expression, and suppresses cell apoptosis and cAMP levels in HUVECs. Cells were transfected with control siRNA or siGPR4 for 36 h, prior to being cultured in normal culture medium (pH 7.4) or acidic medium (pH 6.4) for 12 h. (A) Protein expression levels of GPR4, CHOP and cleaved caspase-3 were determined by western blot assay. (B) Quantitative analyses of the relative expression levels of GPR4, CHOP and cleaved caspase-3. (C) Intracellular cAMP levels. *P<0.05 vs. control group under normal conditions. ^#P<0.05 vs. control group under acidic conditions. GPR4, G protein-coupled receptor 4; CHOP, CCAAT/enhancer-binding protein homologous protein; cAMP, cyclic adenosine monophosphate; HUVECs, human umbilical vein endothelial cells; HCl, hydrochloric acid; siRNA/si, small interfering RNA.