Novel Role Of NR1H3 In Sepsis-induced Myocardial Injury

Sepsis refers to a life-threatening organ dysfunction caused by the host’s maladjustment to infection.Sepsis causes multiple organ dysfunction with extremely high mortality rate,which seriously threatens human health.heart is one of the most injured organs during sepsis.The mortality rate of myocardial injury induced by sepsis is as high as 50%,which is the main reason for the poor prognosis of sepsis patients.Sepsis-induced myocardial injury is characterized by a storm of cytokines,in which interleukin 1β(IL-1β),IL-6,and tumor necrosis factor α(TNF-α)increase significantly.Previous studies have confirmed that multiple molecular-related signaling pathways play an important role in sepsis-induced myocardial injury.However,the molecular mechanism of sepsis-induced myocardial injury has not been fully elucidated,which makes it impossible to develop more effective therapeutic drugs or methods for it,so in-depth research is urgently needed.Liver X receptors α,also known as NR1H3,is an isoform of DNA-binding transcription factor nuclear receptor superfamily member LXRs.NR1H3 not only plays an important protective role in myocardial hypertrophy and myocardial ischemia-reperfusion injury,but also plays an active role in lipopolysaccharide(LPS)-induced inflammation.It is worth noting that NR1H3 activation can reduce sepsis-induced lung injury,However,whether NR1H3 has a protective effect on sepsis-induced myocardial injury and its downstream mechanism is still unclear.Inflammasome is a member of the pattern recognition receptor family as an important part of the natural immune system.NLRP3 is a well-studied inflammasome.Notably,NR1H3 plays an important role in myocardial fibrosis and peritonitis by regulating NLRP3-related pathways.However,it has not been reported whether NR1H3 plays a role in regulating NLRP3 inflammasome in sepsis-induced myocardial injury.In summary,we will use model animals and a series of experimental methods to explore the role of the NR1H3 / NLRP3 signaling pathway in sepsis myocardial injury.MethodsC57BL/6 wild type(wild type,WT)and C57BL/6 mice NR1H3 knockout(NR1H3 knock out,NR1H3-KO)mice were used to establish the cecum ligation perforation(cecal ligation and puncture,CLP)model.Blood routine detector,lactate dehydrogenase kit,small animal ultrasound instrument,HE staining,DHE staining,Western blot,q RT-PCR,immunohistochemistry,transcriptomic sequencing and other instruments and techniques were used to detect and compare the relevant indicators in each group.in order to clarify the role of NR1H3 in sepsis-induced myocardial injury and its downstream mechanism.Results1.Compared with Sham group,blood routine related indicators in the CLP group: the number of white blood cells(WBC),red blood cell(RBC),monocytes(MON),and lymphocytes(LYM)were significantly increased(p<0.05);The contents of lactate dehydrogenase(LDH),creatine kinase(CK),aspartate transaminase(AST)and blood urea nitrogen(BUN)were significantly increased(p<0.05);Cardiac function related indicators: stroke volume(SV)and cardiac output(CO)were decreased significantly(p<0.05);left ventricular end systolic volume and left ventricular end diastolic volume(volume;d)were significantly reduced(p<0.05);left ventricular systolic posterior wall thickness(LVPW;s)and left ventricular diastolic posterior wall thickness(LVPW;d)were decreased significantly(p<0.05);ejection fraction(EF),fractional shortening(FS),heart rate(HR),left ventricular end systolic posterior wall thickness(LVPW;s),left ventricular end diastolic posterior wall thickness(LVPW;d)were increased significantly(p<0.05);The above data indicate that the model of sepsis-induced myocardial injury was successfully constructed.2.Compared with Sham group,the levels of NR1H3 was decreased significantly,while the levels of NLRP3 was increased significantly(p<0.05),The results suggest that both NR1H3 and NLRP3 may be involved in the process of sepsis-induced myocardial injury.3.NR1H3-KO mice were successfully constructed and identified.In the WT sample,when NR1H3 was regarded as the target protein(IP),NLRP3(IB)expression could be detected;when NLRP3 was used as the target protein(IP),NR1H3(IB)could be also detected.Conversely,when NR1H3 was deleted,the expression level of NLRP3 was also decreased significantly.The above data suggest that NR1H3 and NLRP3 exist interaction in myocardium.4.Compared with WT+CLP group,the survival rate of NR1H3-KO+CLP group mice was reduced significantly at 72 h;blood routine related indicators: the number of WBC、PLT、MON and LYM were significantly increased(p<0.05);blood biochemistry related indicators:lactate dehydrogenase(LDH)was decreased markedly(p<0.05);Cardiac function related indicators: SV,CO significantly decreased(p<0.05),left ventricular end systolic volume(volume;s)and left ventricular end-diastolic volume(volume;d)were significantly reduced(p<0.05),left ventricular diastolic anterior wall thickness(LVAW;d)and left ventricular systolic posterior wall thickness were increased significantly(p<0.05);myocardial fiber disorder and cell integrity were significantly increased(HE staining);oxidative stress levels were significantly increased(DHE staining,p<0.05);IL-1 β,myeloperoxidase(MPO)monocyte marker Ly6 c and macrophage marker F4/80 were significantly increased(immunohistochemical staining,p<0.05).The above data indicated that NR1H3 deletion can aggravate sepsis-induced myocardial injury.5.Compared with the WT group,the protein levels of NLRP3、Caspase-1,IL-1β,HMGB1,IL-6,NRF1,TFAM,ATF6,CHOP and Bax in the myocardium of the NR1H3-KO group were significantly increased(p<0.05);the protein levels of Bcl2,GRP78 and PERK were decreased significantly(p<0.05);While the protein levels of SIRT1,p-PERK,PGC-1α and UCP2 were no significant change.It shows that even under undamaged conditions,NR1H3 deletion not only can lead to the activation of NLRP3-related pathways,but also cause changes in inflammation,apoptosis and endoplasmic reticulum stress oxidative stress,and the molecules are mostly negative,but had no significant effect on mitochondrial function-related molecules and oxidative stress.6.Compared with the WT+CLP group,the protein levels of NLRP3,HMGB1,Bax,IL-1β,CHOP,p-PERK,PERK,ATF6,Caspase-1 and TFAM in myocardium of NR1H3-KO+CLP group were significantly increased(p<0.05);the protein level of SIRT1,Bcl2,PGC-1α,NRF1 and GRP78 were no significant change,The above data indicates that the NR1H3 deletion during sepsis-induced myocardial injury can lead to the activation of NLRP3-related signaling pathways,and affect inflammation,apoptosis and endoplasmic reticulum stress signaling pathways.7.In order to fully understand the downstream molecular mechanism of NR1H3 deletion aggravating sepsis-induced myocardial injury,this study further used transcriptome sequencing to detect related samples.Results show that compared with the WT group,one gene in the myocardium of the NR1H3-KO group was up-regulated,Acta1;five genes,except NR1H3,were down-regulated,namely Cd59 a,Cenpf,Ighg2 c,Osbpl6,and Gm28438;Compared with the + CLP group,5 genes in the myocardium of mice in the NR1H3-KO +CLP group were up-regulated,Clec5 a,Marcksl1,Gm10727,Acta2,2210407c18Rik;in addition to NR1H3,12 genes were down-regulated,namely Cd59 a,Pde11a,Osbpl6,Ighg2 c,Cyp4f15,Cdh4,Ppara,AC165273.4,Cnga3,Cngb3,Ccbe1,Rasd2,Clec5 a.indicating the changes of the above genes were related to NR1H3 during the pathological process of sepsis myocardial injury.Using KEGG pathway analysis,it was found that NR1H3 may be related to c AMP signaling pathway,PPAR signaling pathway and vascular smooth muscle contraction and other signaling pathways.In the future,literature review and specific experimental studies will clarify which of these molecules play a key role in NR1H3anti-sepsis-induced myocardial injury and the specific mechanism.conclusionIn conclusion,NR1H3 plays an important protective role in sepsis-induced myocardial injury,and its mechanism involves the regulation of multiple molecular pathways.This study mainly confirmed that NR1H3 can further reduce the damage of inflammation,oxidative stress damage and maintain mitochondrial function by inhibiting the NLRP3-related pathway,eventually playing the role of anti-sepsis-indued myocardial injury.