Ganoderic Acids Alleviate Renal Ischemia Reperfusion Injury By Inhibiting Inflammation And Apoptosis

Ischemia reperfusion injury refers to the pathophysiological process that blood flowing to the particular organ recovers after a period of ischemia and hypoxia but reoxygenation causes greater damage.Kidney is more sensitive to ischemia reperfusion injury due to its structural and functional specificity,which has a higher demand for oxygen and energy.Clinically,Renal ischemia reperfusion injury(RIRI)often occurs in hemorrhagic shock,kidney transplantation and cardiovascular surgery.As one of the main causes of acute kidney injury,RIRI has high morbidity and mortality.According to the existing research,RIRI is so complicated that it involves many factors,including but not limited to ion channel imbalance caused by excessive calcium overload and free radical generation,inflammation,and endoplasmic reticulum stress,mitochondrial dysfunction and apoptosis,so there is still a lack of effective drugs and therapies to prevent or treat RIRI.Ganoderic acids(GAs)are the main pharmacological components of Ganoderma lucidum,and it has been reported that GAs have anti-inflammation,anti-tumor,anti-apoptosis and other pharmacological effects.The aim of this study is to investigate the protective effect of GAs on RIRI and underlying mechanism.In this study,an in vivo model of RIRI injury was induced by clamping the renal artery in mice,and an in vitro model of hypoxia and reoxygenation was constructed by the anoxic incubator.Potentially related signaling pathways were predicted based on database enrichment.Molecular biological and histological techniques,such as Western blot and hematoxylin and eosin(H&E)staining,were used to evaluate the preventive effect and pharmacological mechanism of GAs on RIRI.In the in vivo model of acute kidney injury induced by ischemia reperfusion,GAs preadministration could significantly reduce the levels of blood urea nitrogen and serum creatinine in model mice and improve the lesions such as renal tubule brush border loss,lumen dilation and lumen cell debris,suggesting that GAs can improve the structural damage and dysfunction of the kidney.After reperfusion for 24 hours,the oxidative stress level of the model group reached the peak,while GAs preadministration did not change the oxidative stress indexes significantly.After reperfusion for 48 hours,the model group reached the peak of inflammatory response,and GAs preadministration significantly reduced the production of pro-inflammatory factors in the renal tissues,such as IL-6,COX-2 and iNOS.Above results suggested that the alleviating effect of GAs on RIRI may be more through inhibiting inflammatory response than inhibiting oxidative stress pathway.Further mechanism exploration revealed that GAs could significantly reduce the expression levels of TLR4 and MyD88 and the phosphorylation level of NF-κB,and significantly reduce the renal tubular cell apoptosis and caspase-8 and caspase-3 activities.In the cell model induced by hypoxia and reoxygenation,the levels of pro-inflammatory factors and apoptosis-related proteins of NRK-52E cells increased,which were consistent with the results of in vivo experiments.GAs also reversed these changes with a dose effect.In addition,GAs also showed beneficial effect on renal injury and renal fibrosis induced by long-term RIRI.These results suggest that GAs can inhibit inflammation and alleviate cell apoptosis by down-regulating the TLR4-MyD88-NF-κB signaling pathway and reducing the expression of apoptosis-related proteases,thus alleviating RIRI and progression to chronic kidney disease.This study firstly explores the preventive effect of GAs on RIRI,and GAs do not show significant renal toxicity,suggesting that GAs has the potential to be developed as an effective drug for RIRI.