The Study On The Mechanism Of Rat Liver Injury Related To Different Frequencies Intermittent Hypoxia And The Effect Of Antioxidant Tempol

Background and objectiveObstructive sleep apnea syndrome (OSAS) is characterized by repeatedly apnea and blood oxygen desaturation during night sleep, also is chronic intermittent hypoxia(CIH). CIH is the pathophysiology basis of the damage in patients with OSAS. OSAS is a kind of oxidative stress disease, also a inflammatory disease. The CIH mode may lead to liver cells to the oxidative stress, and then induce a series of changes with inflammatory mediators that NF-κB mediated,eventually lead to liver damage, nonalcoholic fatty liver disease(NAFLD), even nonalcoholic steatohepatitis(NASH). Therefore, we established a CIH model of rats, observed the effects of the different frequencies intermittent hypoxia on rat liver, investigated its possible internal mechanism and the effect of antioxidant Tempol.Content1. The study on oxidative stress and inflammation of rat liver exposed to different frequencies intermittent hypoxia of sleep apnea mode.2. The study on the effect of antioxidant Tempol on rat liver injury exposed to chronic intermittent hypoxia.MethodTo determinate required gas flow rate and oxygen concentration of chamber in the process of establishment of model.72Wistar rats were randomly divided into4different frequencies intermittent hypoxia groups (IH1group、IH2group、IH3group、 IH4group, and the frequencies were10、20、30、40times per hour), Tempol intervention groups(30T1group、30T2group), normal saline control groups(30N1group、30N2group) and normoxia group(NC group).After the experiment, we examined the levels of oxidative stress indicators(MDA、SOD、GSH-PX、T-AOC) and inflammatory mediators(NF-KB、ICAM-1) in liver, and observed the changes of liver histology.Result:The first part1. Liver histology:There was no evident liver damage in NC group. IH groups showed nuclear dark. And as the hypoxia frequency increased, liver cells showed swelling with rarefaction of the cytoplasm, even a few inflammatory cells infiltration. This indicated that CIH could cause rat liver injury.2. The level of MDA in4different IH frequencies groups was higher than in NC group (P all<0.05), the activity of SOD、GSH-PX、T-AOC were lower than in NC group (P all<0.05).And there was a trend as the IH frequency increased, the level of MDA was gradually increased, the activity of SOD、GSH-PX and T-AOC were gradually decreased. The differences of MDA、SOD、GSH-PX、 T-AOC levels were statistical significant between each two different IH frequencies groups (P all<0.05), except the differences between IH3group and IH4group (P all>0.05)3. The levels of NF-κB1CAM-1in IH1group were not significant with in NC group(P all>0.05), but the levels of NF-κB、ICAM-1in other IH groups were higher than in NC group (P all<0.05).Except the differences of NF-κB level between IH3group and IH4group,and the ICAM-1levels between IH1group and IH2group、IH3group and IH4group were not significant (P all>0.05); The differences of NF-κB、ICAM-1levels in other IH groups were significant with each others.Ana there was a trend as the IH frequency increased, the levels of NF-κB、ICAM-1were gradually increased.4. The level of MDA in4different IH frequencies groups was negative correlation with the activity of SOD、GSH-PX、T-AOC respectively (r were-0.721,-0.713,-0.653respectively, P all=0.000).The level of NF-κB was positive/negative correlation with the level of MDA(r=0.789, P=0.000)/GSH-PX(r=-0.766, P=0.000). The levels of NF-κB and ICAM-lwere positive with each other (r=0.667, P=0.000).The second part1. Liver histology:There was no evident liver damage in NC group and30T1group. There exhibited rarefaction of the cytoplasm in30T2group. The rats in IH3group、30N1group、30N2group showed boundaries destruction, hepatocellular swelling with rarefaction of the cytoplasm and nuclear dark. This indicates that Tempol could prevent the liver injury of CIH. 2. Compared with IH3group,30N1group、30N2group, the levels of MDA in30T1group、30T2group were decreased (P all<0.05),and the activity of SOD、 GSH-PX、T-AOC were increased (Pall<0.05).And the levels of MDA、SOD、 GSH-PX、T-AOC were not significant with in NC group(P were0.209,0.117,0.222,0.413respectively), but the differences of MDA、SOD、GSH-PX、T-AOC in30T1group and30T2group、30T2group and NC group were significant(P all<0.05). And there’s no statistically differences among IH3group、30N1group and30N2group (P all>0.05)3. The levels of NF-κB、ICAM-1in30T1group、30T2group were lower than in IH3group、30N1group、30N2group (P all<0.05).The differences of NF-κB、 ICAM-1levels in30T1group、30T2group and NC group were all statistically significant with each others(P all<0.05). And there’s no statistically differences among IH3group、30N1group and30N2group (P all>0.05)Conclusion1. Different IH frequencies had different degrees of injury of oxidative stress and inflammation on rat liver, but the relationship between the degree of injury on liver and the IH frequencies was not entirely a linear.2. Oxidative stress that caused by the accumulation of ROS in tne process of CIH may as the tumor-initiating factor activate NF-κB and the inflammation pathway of NF-κB mediated, then influence the inflammatory mediators;Oxidative stress and inflammation caused rat liver injury together.3. Tempol could prevent the injury on the rat liver of oxidative stress of CIH, then inhibit the activation of NF-κB, to prevent and mitigate liver injury. But Tempol could not completely revese the preexisting liver injury.