The Liver Function Injury And Possible Mechanism In Rats With High-Altitude Deacclimatization

High altitude deacclimatization(HADA)refers to a series of clinical syndromes that occur when people who migrate to high altitude and stay at high altitude for a period of time cannot tolerate the plain environment after returning to the plain.HADA mainly include: drowsiness,insomnia,slow response,memory loss,irritability,headache,sore throat or discomfort,cough,expectoration,chest tightness,palpitation,increased appetite,loss of appetite,diarrhea,abdominal distension,abdominal pain,low back pain and joint pain.The symptoms of HADA will gradually disappear with the extension of staying in the plain,but some people have to return to the plateau because they can not tolerate the symptoms.At present,there is no special means to treat altitude deacclimatization,mainly to return to the plain by descending steps,the use of traditional Chinese medicine or hyperbaric oxygen to prevent or alleviate the symptoms of high altitude deacclimatization.Autophagy is a cellular activity characterized by bilayer or multilayer membrane structure to degrade or recover intracellular substances.According to its formation mechanism,autophagy can be divided into small autophagy,molecular chaperonemediated autophagy and macrophage.When cells are exposed to hypoxia,radiation,stress or lack of nutrients,they will produce autophagy,the main function is to remove damaged macromolecules or organelles.Iron death is an iron-dependent programmed cell death mode caused by the accumulation of lipid peroxides,which is characterized by cell atrophy,mitochondrial shrinkage and aggregation in morphology.the main mechanism is the consumption of antioxidants and the accumulation of oxygen free radicals leading to the damage of biofilm and finally inducing cell death.The role of oxidative stress in the process of HADA is not very clear.Based on this,this study intends to observe the changes of rat liver function and related oxidative stress indexes in the process of hypoxia exposure and deadaptation,in order to explore its corresponding possible mechanism,and try to provide scientific and theoretical basis for the study of the pathogenesis of HADA.Part Ⅰ: Study on the changes of liver function and related possible mechanisms in rats during continuous hypoxia exposure.Objective: To explore the changes of liver function and its corresponding possible mechanism in rats under long-term hypoxia exposure.Methods: Forty-eight adult male SD rats were randomly divided into plain group,plateau1 month group,plateau 2 month group and plateau 4 month group.Each group was placed in an environmental simulation chamber and exposed to simulated altitude of 5000 m.After reaching the time point of modeling,the animals in each group were killed under isoflurane anesthesia,and the serum and liver tissues of rats in each group were collected.The pathological changes of rat liver were observed by HE staining,and the levels of serum ALT,AST and TBIL were determined by automatic biochemical analyzer;The levels of serum superoxide dismutase(SOD)and reduced glutathione(GSH)were measured by ELISA method;The subcellular structure of liver was observed by transmission electron microscope,and the expression of autophagyrelated proteins p62,LC3 II and Beclin-1 in liver tissue was detected by immunoblotting.Results: The liver function indexes ALT,AST and TBIL in the plateau 1 month and plateau2 month groups were significantly higher than those in the plain group(P<0.05),and the liver function indexes in the plateau 4 month group recovered to those in the plain group.The levels of SOD and GSH in the liver tissue of rats in the plateau 1 month and 2 month groups were significantly lower than those in the plain group(P<0.05),and a large number of autophagosomes appeared under transmission electron microscope,and the expression of autophagy-related proteins increased significantly(P<0.05).In the plateau 4 month group,the antioxidant index of liver tissue increased(P < 0.05),and the autophagosome decreased significantly under transmission electron microscope.Conclusion: the liver function index increased at first and then decreased during continuous hypoxia exposure,and fell back to the plain level at the 4th month.The forth month of hypoxia exposure can be used as the starting point of the next deacclimatization reaction.At the same time,it is suggested that the adaptation of rat liver function to hypoxia exposure may be related to antioxidant indexes and autophagy.Part Ⅱ: Changes of liver function and related mechanisms in rats during deacclimatization at high altitude.Objective: To explore the changes of liver function and its corresponding mechanism in rats during the period of deacclimatization at high altitude.Methods: 36 adult SD rats were randomly divided into plain group,altitude group and deacclimatization group.Both the plateau group and the deacclimatization group were exposed to the simulated altitude of 5000 m for 4 months,and the deacclimatization group will be exposed to the plain environment(about 500m)for 3 days after the 4 months.The rats in each group were killed after modeling,and the serum and liver tissue were collected.The pathological changes of liver were observed by HE staining;The levels of serum ALT,AST and TBIL were measured by automatic biochemical analyzer;The levels of serum superoxide dismutase(SOD)and reduced glutathione(GSH)were measured by ELISA;The subcellular structure of liver was observed by transmission electron microscope,and the expression of iron death related protein HO-1 and NRF2 in liver tissue was detected by immunoblotting.Results: The liver function of the deacclimatization group was significantly higher than that of the plateau group(P<0.05),and the antioxidant indexes SOD and GSH of the deacclimatization group were significantly lower than those of the plateau group(P<0.05).The characteristic changes of iron death such as atrophy of hepatocyte mitochondria,deepening of staining,increase of mitochondria number,disappearance of cristae and increase of membrane density were observed under transmission electron microscope in the deacclimatization group.At the same time,the expression levels of iron death related proteins HO-1 and NRF2 were significantly increased in the deacclimatization group(P<0.05).Conclusion: The changes in liver function of rats during deacclimatization may be related to the decrease of antioxidants SOD,GSH and the death of iron in hepatocytes.