Figure 6.

GPR4 is involved in modulating the ER stress response induced by hypercapnic acidosis in HUVEC. HUVECs transduced with the control vector (Vector), GPR4 expression construct (GPR4), or GPR4 R115A mutant expression vector (GPR4 R115A) were treated for 5 h with EGM-2 media buffered with 5% CO₂ or 20% CO₂. Total RNA was isolated and cDNA was synthesized. Real-time qRT-PCR was performed to quantify the mRNA level of (A) ATF3 and (B) CHOP. C_t values were normalized to the housekeeping gene β-actin (ACTB). The expression level of the target genes in HUVEC/Vector cells treated with 5% CO₂-buffered EGM-2 medium was set as 1. Error bars indicate the mean ± SEM. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ns, not significant (p > 0.05); compared with corresponding “5% CO₂” groups. #, p < 0.05; ##, p < 0.01; ###, p < 0.001; comparing the indicated pairs of data. The results shown are the average of at least two biological repeats.