Intermedin protects against renal ischemia-reperfusion injury by inhibiting endoplasmic reticulum stress

Background: Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide family. Endoplasmic reticulum stress (ERS) has been implicated in the pathology of renal ischemia/reperfusion (IRI). In the present study, we investigated whether IMD could reduce ERS damage after renal ischemia. Methods: The kidneys of SD rats were subjected to 45 min of warm ischemia followed by 24 h of reperfusion. The hypoxia/reoxygenation(H/R) model in NRK-52E cells consisted of hypoxia for 1 h and reoxygenation for 2 h. IMD was over-expressed in vivo and in vitro using the vector pcDNA3.1-IMD. The serum creatinine concentration and lactate dehydrogenase (LDH) activity in the plasma were determined. Histologic examinations of renal tissues were performed with PAS staining. Real-time PCR and Western blotting were used to determine the mRNA and protein levels, respectively. Additionally, ER staining was used to detect the ERS response. Results: In the rat renal IRI model, we found that IMD gene transfer markedly improved renal function and pathology and decreased LDH activity and cell apoptosis compared with the kidneys that were transfected with the control plasmid. IMD significantly attenuated the ERS stress parameters compared with IRI group. Indeed, IMD down-regulated glucose-regulated protein 78 (GRP78), C/EBP homologous protein(CHOP), and caspase 12 protein and mRNA levels. Moreover, in the NRK-52E cell H/R model, IMD overexpression prevented the apoptosis induced by H/R. Furthermore, IMD ameliorated the ER structural changes and concomitantly decreased the levels of GRP78, CHOP and caspase-12. Conclusion: This study revealed that IMD protects against renal IRI by suppressing ERS and ERS-related apoptosis.