Nucleoside Nicotinate Attenuates Doxorubicin-Induced Myocardial Injury By Regulating The Nrf-2/P62 Pathway

Objective Doxorubicin(Dox)is an effective drug in the clinical treatment of many kinds of cancer.However,the increase in drug accumulation can cause heart injury,so the clinical application is limited.Dexrazoxane(Dex)is the only drug approved by the Food and Drug Administration(FDA)to prevent cardiotoxicity caused by Dox.One of its protective mechanisms is to reduce the production of reactive oxygen species(ROS)by chelating free iron,but this drug has been proved to induce secondary malignant tumors.Therefore,it is urgent to explore more protection strategies to alleviate the myocardial injury caused by the Dox.NAD~+maintains normal cardiac function,and its precursor can become a new therapeutic strategy to reduce myocardial injury induced by Dox.Nucleoside nicotinate(NAR)is the precursor of NAD~+biosynthesis.This study aims to determine the protective effect of NAR on Dox-induced cardiac injury and its related protective mechanism.Methods In the animal experiment,8-week-old healthy adult female C57BL/6J mice were divided into four groups with eight mice in each group.The Dox group was used as the experimental model group for myocardial injury,and the 0.85%saline group was used as the blank control group.The levels of serum cardiac troponin(c Tn I),ultrasonic electrocardiogram,ejection fraction(EF),short axis shortening(FS),histological staining,and electron microscope were measured to study the protective effect of NAR on Dox-induced myocardial injury in mice.In the H9c2 cell model,the concentration of NAR was screened.5μM Dox was used as the concentration of in vitro model.After H9c2 cells were treated with NAR for 24 h,the optimum concentration was 100μM.The effect of NAR on the proliferation of MCF-7 cells was detected to ensure that the NAR treatment dose chosen by H9c2 cells did not stimulate the proliferation of MCF-7 cells.The related mechanism was studied in the H9c2 cell model.The protective mechanism of NAR on heart injury induced by Dox was studied by measuring the indexes and protein contents related to oxidative stress,apoptosis,and autophagy.Results The results of EF,FS,and serum c Tn I levels showed that NAR significantly improved the cardiac function of mice injected with Dox.We found that NAR not only decreased the levels of malondialdehyde(MDA),lactate dehydrogenase(LDH),reactive oxygen species(ROS),and NADH oxidase(NOX)but also increased the activities of superoxide dismutase(SOD)and glutathione(GSH)in Dox-treated H9c2 cardiomyocytes.After co-treatment with NAR,the survival rate of H9c2 cells exposed to 5μM Dox increased,and the number of apoptotic cells decreased.In addition,some proteins related to apoptosis,oxidative stress,and autophagy,such as caspase-3,Bcl-2,Bax,Nrf-2,ROCK-1,Rho A,Keap1,Beclin1,P62 and LC3B proteins,all changed in varying degrees.The results showed that NAR treatment could reduce apoptosis induced by Dox,reduce the level of oxidative stress and balance excessive autophagy.Conclusion In this study,rat cardiomyocyte H9c2 cells and female C57BL/6J mice were used as experimental models of Dox-induced myocardial injury,and the mechanism of NAR in alleviating Dox-induced myocardial injury was studied by detecting the related indexes of apoptosis,oxidative stress and autophagy.It has been found that NAR has the potential to protect cardiomyocytes against Nrf-2/P62-induced cardiomyocyte injury by regulating Dox-related oxidative stress and autophagy,which can promote the survival of viable cardiomyocytes and reduce Dox-induced myocardial injury,which provides a potential protective mechanism for tumor chemotherapy protective agents.The specific conclusions are as follows:1.NAR has a protective effect on myocardial injury induced by Dox.2.NAR has a good recovery effect on mice’s cardiac function and structure treated with Dox.3.NAR significantly inhibited cardiomyocyte injury induced by Dox by reducing apoptosis rate and oxidative stress,increasing mitochondrial membrane potential,and balancing excessive autophagy.4.The protective mechanism of NAR against Dox-induced myocardial injury involves the Nrf-2-mediated Nrf-2/Keap-1/p62 pathway.These findings may provide new insights into new strategies to reduce Dox-induced cardiomyocyte injury.