Figure 3.

GPR4-knockdown reduces acidosis-induced GPR4 and CHOP protein expression levels, and suppresses apoptosis and cAMP levels of HK-2 cells. HK-2 cells were transfected with control siRNA or siGPR4. After 36 h, cells were cultured in normal culture medium (pH 7.4) or acidic medium (pH 6.4) for 12 h. (A) Protein expression of GPR4, CHOP and cleaved caspase-3 was determined by western blotting. (B) Quantitative analyses of the relative expression levels of proteins. (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; siRNA/si, small interfering RNA; HCl, hydrochloric acid; HR, hypoxia/reoxygenation.