Research About The Effect Of Preconditioning With High Carbon Acid Ventilatory Strategy On Lung Ischemia Reperfusion Injury In Rats

BackgroundGood blood circulation is the basis for maintaining physiological metabolism of tissues and organs.But during the clinical work,it's very common to encounter tissue organs ischemia.Some of the adverse effects caused by ischemia were fatal.Many researches found that it is not ischemia that damages the tissue organs but ischemia reperfusion injury.When the blood circulation became normal,the antioxidant enzymes which could eliminate free radicals was hindered to synthetize itself so that the amount of oxygen free radicals rocketed.They attacked the tissue organs even destructed them.In order to reduce the damage of IR,the best way was to deal with the organs by the method of preconditioning and postconditioning which could trigger the self-protection system of organs.This kind of pretreatment and post processing mode has become the focus of research,and made great progress.We inmagined that if IR is unavoidable,preconditioning with acidic preconditioning before lung ischemia will not attenuate the injury and protect the lungs?Medical workers continuously devoted themselves to the study of lung ischemia reperfusion injury.Through their endeavor,they not only found a lot of medicine and methods to recover that kind of injury but also came up with many precious approaches to protect LIRI,surviving countless lives.Some researches found that LIRI was caused by combined effects including acidosis,the overload of intracellular calcium and the increase of oxygen free radical,etc.The initial factor may be acidosis.Since Darioli and other scientists proposed that applying low ventilation mode to the patients with severe asthma can significantly reduce the mortality rate,clinic gradually reached a consensus which allowed patients to maintain a certain degree of hypercapnia,a new ventilation mode,in order to achieve reduction in mortality,reduce the lung injury.At the beginning,some people hold the view that the relief of lung injury is linked to hypotension.There was a study showed the machinery air itself could cause lung injury,it also claimed that after the use of alkaline drugs which aimed at neutralizing the acid poisoning caused by low tidal volume ventilation,this protective effect disappeared.It demonstrated that acidification was the key factor of releving lung ischemia-reperfusion injury.Studies showed that direct inhalation of carbon dioxide can reduce acute lung injury,increase oxygenation,lung compliance and permeability.This study was to observe the protective effect of pulmonary ischemia and reperfusion injury by adjusting the parameters of respiration in order to pretreat the lung with high carbonic acid.Meanwhile,it would reveal its mechanism with the method of molecular biology,immunology and cytology to find a simple,safe and effective pretreatment mode which could protect the lung tissue from ischemia reperfusion through adjusting the respiratory parameters that caused respiratory acidosis for the clinical operationObjectiveTo study the protective effect of the strategy on lung ischemia-reperfusion in rats by using different methods of high carbonic acid ventilation,and explore its mechanism.MethodsRandomly divided 40 rats into 5 groups,?n=8?sham operation group?s?,ischemia reperfusion group?I/R?,hypercapnic acidosis preconditioning group?A?,hypercapnic acidosis preconditioning group?B?,and hypercapnic acidosis preconditioning group?C?.When the ventilation is normal,end-tidal crbon dioxide tension pressure,P_ETCO₂ was maintained at 35-45mmHg,the respiratory frequency is 70 BPM,tidal volume is 12-14ml/kg,inspiratory-to-expiratory ratio is 1:2.Blocking the left pulmonary hilum and just ventilate single lung,the respiratory frequency is 35bpm,tidal volume is 6-7ml/kg,inspiratory-to-expiratory ratio is 1:2.The sham operation group?s group?:Free the left pulmonary hilum without ventilation for 180 minutes.Ischemia reperfusion group?I/R?:After stabilizing free the left pulmonary hilum,continue to ventilate for 15 minutes,then block the lung for 45 minutes,and open for 120 minutes.Hypercapnic acidosis preconditioning group?A?.Free the left pulmonary hilum and make it stable,then adjust the respiratory frequency to make P_ETCO₂ reach 55-65mmHg and maintain it for 5 min.Then ventilate normally to make P_ETCO₂ become normal,and circulate this process for 3 times.Block the left lung for 45 minutes,then open it for 120 minutes.High carbonation pretreatment group?B?:Free the left pulmonary hilum and make it stable,then adjust the respiratory frequency to make P_ETCO₂ reach 65-75mmHg and maintain it for 5 minutes.Then ventilate normally to make P_ETCO₂ become normal and circulate this process for 3 times,block the left lung for 45 minutes,then open it for 120 minutes.High carbonation pretreatment group?C?:Free the left pulmonary hilum and make it stable,then adjust the respiratory frequency to make P_ETCO₂ reach 75-85mmHg and maintain it for 5 minutes,then ventilate normally to make P_ETCO₂ become normal.Circulate this process for 3 times,block the left lung for 45 minutes,then open it for 120 minutes.lock the left lung for 45 minutes,open for 120 minutes.After finishing the experiment,kill the rat by emptying the blood of its left atrium,To extract the total protein content in the bronchoalveolar lavage fluid?BALF?of the left bronchus.Test the ratio of Wet/dry?W/D?weight and the content of MDA and SOD.Rats' lung tissue specimens were observed by naked eye morphology and HE staining.The expression of TNF-? was detected by immunohistochemistry,and the expression of TNF-? mRNA was detected by RT-PCR.Results:1.The value of W/D,MDA,TP,IL-8,the protein expression in immunohistochemical and mRNA expression in RT-PCR of TNF-? in group A,B and C were higher than group sham?group s?,lower than the group ischemia-reperfusion?group I/R?,which have statistical significance?p<0.05?.The index above of high carbonate preconditioning group,A B,C decrease gradually,there are statistical differences between A and C?p<0.05?.The value of IL-10 in group A,B and C were higher than group sham,lower than the group ischemia-reperfusion.There are statistical significance between group I/R and S?p<0.05?,and no statistically significant difference among the other groups.The SOD of A,B,C was lower than sham operation group?Group s?,higher than the group ischemia-reperfusion?group I/R?,which have statistical significance?p<0.05?.The SOD of high carbonate preconditioning group,A B,C increase gradually,which have statistical significance between group A and group C?p<0.05?2.Pathological results of lung tissue showed that:In A,B,C pulmonary interstitial edema,inflammatory cells,hemorrhage and alveolar structural changes were lighter than those in group I/R,but were higher than those in group S.The lung structure destruction of A,B,C reduced Gradually.Conclusions1.The strategy of high carbonate pretreatment ventilation can protect the rat's lung from ischemia reperfusion injury.2.In the range of 55-85 mmHg,the protective effect of the high-carbonate strategy on rat's lung enhanced with the increase of P_ETCO₂.3.The protective mechanism of high carbonic acid ventilation strategy may be related to reducing the level of oxygen free radical and the expression of IL-8 and down regulating the expression of TNF-?.