Protective Role Of Mitsugumin 53 In Lung Ischemic/reperfusion Injury After Limb Remote Ischemic Preconditioning In Rats

BackgroundLung ischemia reperfusion injury(LIRI) is the tissue and cell structure damage,metabolism disorder and dysfunction caused when the pulmonary blood supply returns to the pulmonary tissue after a period of ischemia.The LIRI is the common pathophysiologic phenomenon in a variety of clinical settings,such as shock,lung transplantation,cardiopulmonary resuscitation,pulmonary embolism,cardiac surgery and so on.LIRI is the major cause for the acute respiratory distress syndrome(ARDS) and acute respiratory failure(ARF) which influences the recovery and survivability of patients.Hence the high morbidity and mortality,to find a new therapeutic method with efficiency,feasibility and less complications becomes a hot research spot.Existing researches have discovered that ischemic preconditioning could be some protective from ischemic reperfusion injury.While during IPC it may also produce some inevitable organ damage.Therefor,a better protocol with protection but without organ damage has been desired for decades.The remote ischemic preconditioning was not described until investigators carried out experiments on a renal IPC to prevent cardiomyocytes from ischemic reperfusion injury.The discovery of RIP--completed the IPC--avoided the unnecessary damage to the target organ and reserved the powerful endogenous protection.The protection exists pervasively in organs.Lower limb RIPC protects the lung tissue from IRI,as reaching broad consensus,which improves the survival time variously by attenuating the pulmonary edema,reducing the release of inflammatory factors,decreasing apoptosis and so on.The research mainly focused on the neural mechanism,the humoral mechanism or the both at present.But the critical mechanism remains to be elaborated.As a major component organ of lower limb RIPC,the role of skeletal muscle has aroused enough attention.Skeletal muscle isa motor organ as well as an endocrine organ which excretes many peptides called myokines,and cytokines.Current studies imply that some substances from skeletal muscles participate in lower libm RIP,but the substances are not skeletal muscle-specific,which could not elucidate the mechanism of lower limb RIP clearly.As a kind of skeletal muscle-specific myokines,MG53 has been described as an essential component of the cell membrane repair machinery which has been proved in the heart,kidney and lung tissues.And early studies reminiscent that expression of MG53 increased after skeletal muscle stumulation.Based on the rationale above,we hypothesized:lower limb RIPC functions through the repeated brief occlusion and reperfusion of femoral artery;the lower limb RIPC induces the hypoxia condition of skeletal myocytes,which may result a great deal of MG53 proteins releasing from skeletal myocytes to the blood.Thereby,the MG53 released into blood transports to the injured pulmonary tissues and aggregates at the injured membrane to repair it when the lung tissues injured.Thereby MG53 may be a novel mechanism for the protection of lower limb RIPC.PurposeTo identify the role of MG53 in the protection of lower limb RIPC from the lung ischemia reperfusion injury in rats and to elucidate the mechanism of lower limb RIPC further.Content1. Establish different Sprague-dawley rat surgery models to identify the protection of RIP for the lung injury.2. Observe the expression of MG53 protein in lung tissue,skeletal muscle and serum in different groups and identify the influence of lower limb RIP in the expression of MG53 protein.3. Establish lung ischemic reperfusion model on wild type and MG53 knock-out mice to identify the important role of MG53 protein in the protection of lower limb RIP.Method1. Sprague-dawley rats were divided into the following experimental groups:sham control,LIRI,and RIP+LIRI.Identified the protection of RIP in LIRI via arterial PaO2,lung wet/dry ratio(W/D),survival time,post-operative lung tissue slice HE staining.2. Extracted post-operative lung tissue,skeletal muscle and serum total protein of three models and Western Blotting was used to detect the alteration of MG53 expression.3. Established lung IR group and RIP+lung IR group models in MG53 knock out mice and observe whether RIP was capable to exert the protection of lung from ischemic reperfusion injury via indexes such as arterial PaO2,lung wet/dry ratio(W/D).Results1. In SD rats,lowe limb RIP significantly ameliorated the arterial PaO2 of the ischemic reperfusion injured lung,attenuated the lung tissue edema and extended the survival time of rats to a certain extent.2. In the lower limb RIP group MG53 in lung expressed significantly higher than that in the IR group.And the serum MG53 expression was also increased.3. To identify the role of MG53 protein in lower limb RIP,we established the LIRI model on wild type and mg53 knock-out mice and the results implied that;in the wild-type mice,RIP attenuated the LIRI.While in the MG53 knock out mice lower limb RIPC did not ameliorate the injury.The arterial PaO2,lung Wet/Dry ratio(W/D) did not improved.And after MG53 gene knocked out the sensibility to LIRI increased in mice.Conclusion(1)Lower limb RIP could ameliorate the LIRI;(2)Lower limb RIP could increase the MG53 expression in lung tissue and serum.(3)The sekeletal muscle-specific MG53 protein released by the induction of lower limb RIP from skeletal muscles has an protective effect for LIRI.