Effects Of Irisin And Cardamonin On Sepsis-induced Myocardial Injury And Its Mechanisms

BackgroundMyocardial injury is a commonly clinical complication during sepsis,and cardiac dysfunction caused by sepsis could greatly increase the mortality of patients with sepsis.Mitochondrial damage,inflammation and oxidative stress play crucial roles in the pathogenesis of sepsis-induced myocardial injury.Recent studies have confirmed that Irisin and Cardamonin(CAR)play protective roles in various cardiovascular diseases by regulating mitochondrial mass,inhibiting oxidative stress and inflammation,respectively.However,their roles in sepsis-induced myocardial injury and the specific mechanisms have not been reported.Therefore,according to using various experimental techniques,We intend to explore the effects of Irisin and CAR on sepsis-induced myocardial injury and its specific mechanisms by constructing animal and cell models of sepsis-induced myocardial injury,which will provide new strategy for the treatment of sepsis-induced myocardial injury in clinical.MethodsIn the first chapter,an animal model of sepsis-induced myocardial injury was constructed by intraperitoneal injection of LPS.Wild type(WT)mice with C57BL/6 background were divided into control group,LPS group and LPS-Irisin group according to different interventions.We utilized echocardiography,HE staining,electron microscope,TUNEL staining,MitoSOXTM red mitochondrial superoxide indicator,JC-1 fluorescent probe,ELISA,Western Blot,RT-PCR and other technologies to clarify the effects of Irisin on cardiac structure and function,myocardial apoptosis,inflammation,oxidative stress,mitochondrial fission and mitochondrial function.In vitro,cardiomyocyte contractile properties,proteins expression of JNK-Drpl pathway and et al were measured through respectively using mitochondrial fission agonist FCCP and JNK agonist Anisomycin(AnI)to further explore the molecular mechanism of Irisin affecting sepsis-induced myocardial injury.In the second chapter,Wild type(WT)mice with C57BL/6 background were treated with LPS injection to induce septic cardiomyopathy.These mice were divided into control group,LPS group,Control-CAR group and LPS-CAR group according to different interventions.Echocardiography,HE staining,TUNEL staining,ROS fluorescent probe,Western Blot,RT-PCR and et al were used to explore the effects of CAR on cardiac morphology and function,myocardial apoptosis,inflammation,and oxidative stress.In vitro,we also used Nrf2 inhibitor ML-385 and NF-?B agonist prostratin in order to further verify that CAR mainly prevents sepsis-induced myocardial dysfunction by regulating Nrf2 and NF-?B signaling pathways.ResultsChapter 1 research showed:(1)Irisin maintained cardiac function by ameliorating LPS-induced myocardial ultrastructural damage and cardiomyocyte apoptosis.(2)Irisin ameliorated LPS-induced mitochondrial oxidative stress and inflammation by reducing the release of mtROS,upregulating the transcription levels of antioxidant enzymes SOD1,Gpx1 and Catalase,and inhibiting the secretion of pro-inflammatory factors TNF-?,IL-1? and IL-6.(3)At the molecular mechanism level,Irisin alleviated the accumulation of myocardial mtROS by inhibiting JNK-Drp1-dependent excessive mitochondrial fission,upregulating the expression of mitochondrial respiratory complexes,restoring mitochondrial membrane potential and ATP production.(4)Irisin nullified LPS-induced cardiomyocyte apoptosis by inhibiting mitochondrial apoptosis pathway initiated by the leakage of mitochondrial apoptosis factor Cyt-c to the cytoplasm which was induced by mtROS accumulation.(5)Irisin maintained mitochondrial and cardiac function by inhibiting JNK-Drpl-dependent excessive mitochondrial fission.Chapter 2 research showed:(1)CAR maintained cardiac function in LPS-treated hearts by inhibiting LPS-induced oxidative stress,inflammatory response and myocardial apoptosis.(2)CAR mitigated LPS-induced oxidative stress through activating Nrf2 signaling pathway by promoting the translocation of Nrf2 to the nucleus,increasing the expression of Nrf2 downstream genes SOD1,Gpx1,Catalase and reducing the release of ROS from cardiomyocytes.(3)CAR mitigated LPS-induced inflammatory response by restraining the expression of cardiac proinflammatory factors TNF-?,IL-1?,and IL-6 through downregulating the protein expression of pI?B?/p-NF?B and inactivating the NF-?B signaling pathway.(4)The role of CAR in protecting cardiac function during sepsis depends on its regulation of Nrf2 and NF-?B signaling pathways.ConclusionThe salient findings from our current study revealed that the protective roles of Irisin and CAR in sepsis-induced myocardial injury for the first time.Chapter 1 research revealed that Irisin effectively maintains the normal ultrastructure and function of myocardium by inhibiting JNK-Drpl dependent excessive mitochondrial fission,reducing mitochondrial oxidative stress and inflammatory response,restoring mitochondrial function and reducing myocardial apoptosis.Chapter 2 research revealed that CAR effectively maintains cardiac function by inhibiting LPS-induced oxidative stress and inflammatory response via activating Nrf2 signaling pathway and inhibiting NF-?B signaling pathway,and reducing myocardial apoptosis.