The Study Of Mechanism Of The IPo To The Small Intestinal Ischemia-Reperfusion Injury In Rats

Background and objective Ischemia-reperfusion injury (IRI) of the intestine is an important factor associated with a high morbidity and mortality in both surgical and trauma patients. It is of importance in situations such as the interruption of blood flow to the gut as in abdominal aortic aneurysm surgery, cardiopulmonary bypass, strangulated hernias, necrotizing enterocolitis, and intestinal transplantation. IRI of the intestine also occurs in septic and hypovolemic shock. Interruptionof blood supply results in ischemic injury which rapidly damages metabolically active tissues. Paradoxically, restoration of blood flow to the ischemic tissue initiates a cascade of events that may lead to additional cell injury known as reperfusion injury. This reperfusion damage frequently exceeds the original ischemic insult. On restoration of the blood supply, the molecular and biochemical changes that occur during ischemia predispose to free radical-mediated damage. The reduction of blood supply results in damage to the intestinal mucosa.Among the internal organs, the intestine is probably the most sensitive to IRI. The intestine is composed of labile cells that are easily injured by episodes of ischemia. Subsequent reperfusion of the intestine results in further damage to the mucosa. It has been shown that the enterocytes that are located at the tips of the villi are more sensitive to the effect of ischemia. Earlier studies attributed this increased sensitivity of the enterocyte at the tips of the villi to the location which is at the end of the distribution of a central arteriole which can lead to lower oxygen tension compared to other cells. There is substantial evidence that the mucosa of the intestine becomes the site for the production of various acute-phase proteins and cytokines. These not only influence the intestine but also may affect the function and integrity of distant organs. The initial site of abnormality in ischemia has been emphasized on the cellular mitochondria, which is particularly important in producing adenosine triphosphate (ATP) for organ recovery (16). The damage, however, is dramatically magnified by a large number of events, such as oxygen free radical formation, release of iron storage, damage of the microvasculature of IR organs, inflammatory cytokines, complement activation, and neutrophil infiltration at the site of injury. So the I/RI was regarded as one of the "motor of MODS" in the systemic inflammatory response syndrome (SIRS) and multi-organ dysfunction syndrome(MODS).The Ischemic Preconditioning (IPC) refers to a phenomenon whereby exposure of a tissue to brief periods of ischemia protects them from the deleterious effects of prolonged IRI. Its beneficial effects have been demonstrated in the liver, skeletal muscle, brain, heart, lung, intestine, and kidney in various animal models. Although the patients always have ischemic injury before in-hospital, they can not be dealed with the IPr. So the IPr has its limited in clinical practice. For this reason the ischemic postconditioning (IPo) was induced and several experiments demonstred that the IPo can relieve the injury of the IRI and it seemed good perspective of clinical application. However, the mechanism of the IPo is unknown.This study was to establish the model of ischemia-reperfusion of intestine. The aim is to study the protective effect of the ischemic postconditioning on bacteria translocation, intestinal pathology, and morphology and function of mitochondria. We hope find a good kind of approach and experimental proof to treat the intestinal ischemia-reperfusion injury.Methods The Sprague-Dawley rats were randomly divided into different groups to compare" study. All the animals divided into sham group (S), ischemia-reperfusion group (IR), ischemic preconditioning group (IPr) and ischemic postconditioning group (IPo). The S group as for sham-operated. The IR group for the rats submitted to45-minute of intestinal ischemia and2-hour or4-hour reperfusion. The IPr group was given three alternative cycles of2-min ischemia and2-min reperfusion before the intestinal ischemia. The other operation just like as the IR. group. The IPo group was given three alternative cycles of2-min reperfusion and2-min ischemia before the reperfusion. The other operation like as the IR group. The second chapter to study the protective effect of the IPo on the IRI in rats. The exam of this part include bacterial translocation, histopathologic grades, inflammatory cytokines and cells apoptosis and so on. The third chapter was to study the effect of the IPo on the mitochondria. The mitochondrion is the most sensitive cell organelle to the IRI and is the center priming place of cell apoptosis and cell necorosis. This experiment was showed that the IPo can effectively prevent the function of the mitochondria from IRI in small intestine. All of the experiment data were compared by statistics method.Result The second chapter showed that the Ecoli DH5a at lymphonodi mesenterici. liver, lung, spleen and portal vein translocation in the IPo group was lower than in the IR group at2-hour and4-hour(.P<0.05). And the intestinal pathologic injury by Chiu"s classification in the IPo group were2.30±0.96at2-hour,3.1±0.66at4-hour, which were lower than the IR group3.50±0.85at2-hour,4.62±1.14at4-hour. They have conspicuous statistic difference when compared respectively at the same time(.P<0.05). The third chapter showed that the IPo can lessen pathologic injury of mitochondria and suppress release of inflammatory factor, protect the mitochondrial function and prevent MtDNA disassociation. The contents of study in this chapter include follow aspect.1.The IPo can relieve the injury degree of mitochondria ultrastructure in cells of mucous membrane of small intestine in model of the intestinal IRI.2. The IPo can lessen oxidative damage of mitochondria membrane and elevate the compound activities of mitochondrial respiratory chain.3. The IPo can increase the synthetical abilities of adenosine triphosphate after intestinal IRI.4. The IPo can protect the activities of respiratory compound I-IV and improve mitochondrial respiratory function.5. The IPo can maintain the stability of mitochondrial membrane potential(Δ Ψm) through lighten the mitochondrial lipid peroxidation and safeguard integrality of mitochondrial inner membrane.6. The IPo can reduce generation of mitochondrial endogenous reactive oxygen species(ROS) so relieve reaction of oxidative stress.7. The IPo can maintain mitochondrial protein expression and keep mitochondrial quality while intestinal IRI.8. The IPo can relieve oxidative damage of mitochondrial DNA(mtDNA), reduce injury rate of mtDNA and increase mtDNA's copy number. The upper aspects have significant difference in IPo and IR group (P<0.05). The IPo and IPr groups have not significant difference(P>0.05).Conclusion1. The IPo can effectively relieve the bacterial translocation and intestinal mucous membrane pathological injury, and can restrain release of pro-inflammatory factors in IRI.2. The IPo can maintain the mitochondrial form and function in IRI through restrain generation of reactive oxygen species and prevent cellular apoptosis and necrosis in IRI.