Shikonin Inhibits Endoplasmic Reticulum Stress-Induced Apoptosis to Attenuate Renal Ischemia/Reperfusion Injury by Activating the Sirt1/Nrf2/HO-1 Pathway

Introduction: Shikonin is the major bioactive compound abundant in Lithospermum erythrorhizon and possesses diverse pharmacological properties. This study aimed to examine shikonin roles in experimental renal ischemia/reperfusion (I/R) injury. Methods: Renal tissues and blood were collected from experimental renal I/R injury models. Kidney functions, structural injuries, and cellular death were assessed. Markers of endoplasmic reticulum (ER) stress were evaluated by RT-qPCR and Western blotting. The effect of shikonin on Sirt1/Nrf2/HO-1 signaling was detected by Western blotting and immunofluorescence staining. HK-2 cells that underwent hypoxia/reoxygenation (H/R) process were used to perform CCK-8 and flow cytometry. Results: For in vivo analysis, renal dysfunctions and tissue structural damage induced by I/R were relieved by shikonin. Additionally, shikonin alleviated ER stress-induced apoptosis in I/R mice. For in vitro analysis, shikonin inhibited ER stress-stimulated apoptosis of H/R cells. Mechanistically, shikonin activated Sirt1/Nrf2/HO-1 signaling post-I/R, and inhibition of Sirt1 limited shikonin-mediated protection against ER stress-stimulated apoptosis in both animal and cellular models. Conclusion: By activating Sirt1/Nrf2/HO-1 signaling, shikonin inhibits apoptosis caused by ER stress and relieves renal I/R injury.