Roles Of FoxO3a In Acute And Chronic Oxygen Toxicity Induced By Hyperbaric Oxygen Exposure

We call the pressure which is more than one atmospheric pressure as high pressure.Hyperbaric oxygen(HBO)therapy is defined as placing the body in a high-pressure environment and breathing pure oxygen to treat a disease.Hyperbaric oxygen(HBO)is now widely applied in many ways,such as submarine escape,diving operations and clinical work.After depth diving,breathing hyperbaric oxygen can replace the inert gas between diving quickly to effectively prevent the occurrence of decompression sickness.The recent investigations on the escape of crews from the disabled submarine have pointed out that pre-breathing hyperbaric oxygen(HBO)before buoyant fast ascent can remarkably relieve the condition and sequelae of decompression sickness.Clinically,HBO can improve tissue hypoxia,promote repairment and regeneration of damaged tissue.It is effective to the diseases such as hypertensive intracerebral hemorrhage,diabetic foot,spinal cord injury and so on.Toxic reaction will occur in organism following the inhalation of the gas with exorbitant partial pressure of oxygen.If the partial pressure is over 200 kPa,the toxic reaction would have taken place very fast.The main clinical manifestation of acute oxygen toxicity is the functional disorder of central nervous system(CNS),which is called CNS acute oxygen toxicity(CNS-OT).One of the most intensive and representative appearance is convulsion grand mal,named “oxygen convulsion”.While oxygen convulsion occurs,the body will also appear pulmonary hemorrhage symptoms as the main acute lung injury.Once the partial pressure is between 60~200 kPa,the main clinical manifestation of oxygen toxicity is the functional disorder of lung tissue,which is called chronic oxygen toxicity.Thus,the occurrence of oxygen toxicity severely limits the application of hyperbaric oxygen.Therefore,depth study of the development process and the pathogenesis of oxygen poisoning occurs,especially to determine the key factors directly resisting to its onset,has a very important practical significance for effective prevention and treatment of oxygen toxicity.Recent studies have shown that transcription factors FoxO3 a plays a very important role in the terms of oxidative stress.FoxO3 a both induces apoptosis,but also protects the cell survival under conditions of oxidative stress.It plays a variety of different mechanisms under different cells and different tissue oxidative stress.And PI3K-Akt-FoxO3 a signaling pathway,which is considered as a major signaling pathwaysof oxidative stress,plays an important role in the process of oxidative stress.Once the phosphorylation sites on FoxO3 a such as threonine residues 32(Thr32)?serine residue253(Ser253)and serine residues 315(Ser315)are phosphorylated,which mediate FoxO3 a transferred from the nucleus to the cytoplasm,Can mediate FoxO3 a transferred from the nucleus to the cytoplasm,transcriptional activity is inhibited.But when the PI3K/Akt/FoxO3 a pathway was inhibited,the dephosphorylation of FoxO3 a will gathere mostly in the nucleus to activate the expression of downstream target genes.Firstly,this paper aims to explore the reactions of mice and pathological changes of their central nervous system and lung tissue after exposure to hyperbaric oxygen.We explore whether FoxO3 a plays role in the development of acute and chronic toxicity.What's more,we also explore how FoxO3 a actin and its possible mechanism.For this,we carried out the following work:Part 1: Studies on the effects of FoxO3 a on the acute oxygen toxicity induced by hyperbaric oxygenMice were placed in a hyperbaric chamber at the pressure of 6 ATA for 30 min to constructe acute oxygen toxicity models.We observed the convulsion latency and the number of episodes between 30 min of FoxO3 a knockout mice to assess the damages of their brain tissue.And we conducted pathology slices and lavage fluid protein quantification in the BALF to assess the damage of lung tissue.What's more,antioxidant enzyme activity and index production were detected by commercial kits to explore the role of FoxO3 a.After the normal mice were exposed to hyperbaric oxygen,western blot was used to assay FoxO3 a protein expression of the cerebral cortex and lung tissue and immunohistochemistry was used to locate the place of FoxO3 a.So as to explore the signaling pathways and mechanisms of how FoxO3 a acted in the process of oxidative stress.Mice were given PI3K/AKT inhibitor: LY294002 to block down PI3K/Akt/FoxO3 a path in the brain tissue and lung tissue.Methods similar to the above were conducted to assess the damages of the brain tissue and lung tissue of mice after exposure to hyperbaric oxygen.It is found that,the convulsion latency of FoxO3 a knockout mice is shorter than the non-knockout mice,but the number of seizures within 30 min increased significantly.The overall lung damage of FoxO3 a knockout mice is more serious than non-knockoutmice;After the end of HBO exposure 8h,FoxO3 a protein reaches the peak and protein moves into the nucleus obviously;PI3K/AKT inhibitor: LY294002 blocked down PI3K/Akt/FoxO3 a path of the mice,the foxO3 a moved to the nucleus.Brain damages and lung injury were relieved.Part 2: Studies on the effects of FoxO3 a on the chronic oxygen toxicity induced by hyperbaric oxygenMice were placed in a hyperbaric chamber at the pressure of 2.5 ATA for 6 h to constructe chronic oxygen toxicity models.After the normal mice were exposed to hyperbaric oxygen,western blot was used to assay FoxO3 a protein expression of the brain tissue and lung tissue and immunohistochemistry was used to locate the place of FoxO3 a.So as to explore the signaling pathways and mechanisms of how FoxO3 a acted in the process of oxidative stress.Mice were given PI3K/AKT inhibitor: LY294002 to block down PI3K/Akt/FoxO3 a path in the brain tissue and lung tissue.Methods similar to the above were conducted to assess the damages of the lung tissue of mice after exposure to hyperbaric oxygen.It is found that,after the end of HBO exposure 8h,FoxO3 a protein reaches the peak and protein moves into the nucleus obviously;PI3K/AKT inhibitor: LY294002 blocked down PI3K/Akt/FoxO3 a path of the mice,the FoxO3 a moved to the nucleus and lung injury were relieved.These results suggest that: FoxO3 a can significantly reduce acute and chronic poisoning,hyperbaric oxygen due to oxygen;inhibition of PI3K/AKT signaling pathway can push FoxO3 a into the nucleus,which plays an important role in protection against oxidative stress injury in the process.