CBX7 suppression prevents ischemia-reperfusion injury-induced endoplasmic reticulum stress through the Nrf-2/HO-1 pathway

Renal ischemia-reperfusion injury (I/R) usually occurs in renal transplantation and partial nephrectomy, which could lead to acute kidney injury. However, the effective treatment for renal I/R still remains limited. In the present study, we investigated whether inhibition of chromobox 7 (CBX7) could attenuate renal I/R injury in vivo and in vitro as well as the potential mechanisms. Adult male mice were subjected to right renal ischemia and reperfusion for different periods, both with and without the CBX7 inhibitor UNC3866. In addition, human kidney cells (HK-2) were subjected to a hypoxia/reoxygenation (H/R) process for different periods, both with or without the CBX7 inhibitor or siRNA for CBX7. The results showed that expression of CBX7, glucose regulator protein-78 (GRP78), phosphorylated eukaryotic translation initiation factor-2 alpha (p-eIF2 alpha), and C/EBP homologous protein (CHOP) were increased after extension of I/R and H/R periods. Moreover, overexpression of CBX7 could elevate the expression of CBX7, GRP78, p-eIF2 alpha, and CHOP. However, CBX7 inhibition with either UNC3866 or genetic knockdown led to reduced expression of GRP78, p-eIF2 alpha, and CHOP through nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 activation in I/R and H/R injury. Furthermore, ML385, the Nrf2 inhibitor, could elevate endoplasmic reticulum stress levels, abrogating the protective effects of UNC3866 against renal I/R injury. In conclusion, our results demonstrated that CBX7 inhibition alleviated acute kidney injury by preventing endoplasmic reticulum stress via the Nrf2/HO-1 pathway, indicating that CBX7 inhibitor could be a potential therapeutic target for renal I/R injury.