The Effects Of Different Time And Concentrations Of Normobaric Oxygen On Cerebral Ischemic Penumbra Apoptosis

Objectives To study the effects of normobaric oxygen(NBO) of different concentrations and time on acute cerebral ischemia and reperfusion of early ischemic penumbra of apoptosis in rats’ brain, in order to provide valuable basis for the clinical effective of oxygen in patients with acute ischemic stroke.Methods Grouping: The 150 healthy male SD rats at SPF level were randomly divided into five groups, which were sham groups, high, medium and low concentrations of NBO treatment groups and air groups. Then every group was randomly divided into six subgroups that were ischemia-reperfusion for 3h, 6h, 12 h, 24 h, 48 h and 72h(n = 5). Making models: Rats were given intraperitoneal anesthesia with 10% chloral hydrate(0.35ml/100g). Referring to Zea Longa suture method of middle cerebral artery embolism and five-level four-point standard neurological deficits scale, embolus were inserted into the rats’ brain for 20-25 mm. Observations in rats’ behavior were after 2 hours’ embolization, and samples were randomly supplementafter excluding rats of 0 point to ensure the sample size. 2 hours later, after scoring and ether anesthesia, we extracted the sutures to restore arterial blood flow in the rats’ brain to implement reperfusion. Interventions: we placed successful ischemic models into a homemade enclosed oxygen chamber(50cm × 30 cm × 30 cm, there were two 1cm × 1cm holes on two sides respectively connected to oxygen and nitrogen bottles and oxygen analyzer). Adjusted the flow of oxygen and nitrogen and monitored oxygen concentration in the oxygen chamber by oxygen analyzer. The high, medium and low concentrations of NBO were 61%, 45%, 33%, and air groups inhaled air. Neurological functions were valuated in rats before and after oxygen treatments, and the brain tissues were collected at the corresponding points after oxygen inhalation. Examinations: The fluorescence quantitative Polymerase Chain Reaction(PCR) were used to detect expressions of Caspase-3 and Caspase-9 m RNA, and immunohistochemical method to detect expressions of Caspase-9, Caspase-3, Bax and Bcl-2 in brain tissues, GENMED superoxide dismutase(SOD) activity assay kit to detect activities of SOD.Results 1 Neurological deficit scores of rats after reperfusion and NBO treatments were lower to some degree. Compared with the air groups, the scores of high concentration of 3 and 6h, 12 and 24 h of high and medium groups, 48 and 72 h of high, medium and low concentration groups had statistically significant differences(P<0.05). Among other groups there were no statistically significant differences(P> 0.05). 2 At every time point of low, medium and high concentrations of NBO groups and air groups, compared with the sham groups, the expressions of Caspase-9, Caspase-3, Bax, Bcl-2-positive cells had statistically significant differences(P<0.01). At all the time point compared with air groups, the differences of expressions of Caspase-9, Caspase-3, Bax, Bcl-2 positive cells in low, medium and high concentrations of NBO groups were statistically significant(P<0.01). At each time point except time point of 72 h, the differences of expressions of Caspase-9,Caspase-3, Bax, Bcl-2-positive cells between low and high concentration of NBO groups were statistically significant(P <0.05). 3 At each time point, the differences of SOD activities were statistically significant(P<0.01) in the low, medium and high concentration of NBO groups and air groups compared with sham groups. At each time point, SOD activities were increasing in varying degrees in low, medium and high concentrations of NBO groups compared with air groups, and the differences were statistically significant(P <0.01). At each time point except time point of 72 h, the differences of activities of SOD between low and high concentration of NBO groups were statistically significant( P<0.05).Conclusions 1 Different concentrations of NBO could improve neurological function of cerebral ischemia and reperfusion in rats, and the improvement in high concentration of NBO was more obvious; 2 Different concentrations of NBO could significantly reduce the expression of early pro-apoptotic factor Caspase-9, Caspase-3 and bax in acute cerebral ischemia and reperfusion, and increase the expression of anti-apoptotic factor bcl-2; 3 Different concentrations of NBO might suitably promote the expression of antioxidant enzymes SOD, without significant increasement in the oxygen toxicity. 4 The 45% to 61% concentrations NBO in 3h ~ 72 h have better effects for AIS rat, it provided a valuable scientific basis for the clinical effective of oxygen in patients with acute ischemic stroke.