Expression Of Aquaporin 1 In Small Intestinal Tissues Of Rats In The Early Stage After Severe Burn And Its Relationship With Tissues Edema

Research backgroundIn normal state, Intestinal tract have mechanical, biological, immune barrier function; they have formed a multifaceted, multilevel safety net; Intestinal mucosal barrier of defense depends on its function, can protect the host from bacterial and endotoxic invasion of the intestine. After severe burns, the body occurs acute intestinal mucosal ischemia and a series of damage; Then it reduces the intestinal barrier function. These results produce a series of intestinal function disorders. It is an important reason to cause systemic inflammatory response syndrome(SIRS) and multiple organ dysfunction syndrome(MODS). In recent years, more and more studies clearly showed that ischemia and excitable intestinal tract can promote inflammatory response. After the visceral ischemia-reperfusion period, the release of intestinal media not only activates macrophages, neutrophils and other proinflammatory cells, but also causes acute dysfunction of distant organs and cells. Based on intestine plays an important role in preventing systemic infection and MODS, therefore, some scholars propose the concept of "shock intestine" that conduce to in-depth study and research. After years of research, we find that the damage of intestine after burn related primarily to the following:1, Ischemia and hypoxia; 2, Ischemia-reperfusion; 3, Inflammatory mediators, bacteria and endotoxin; 4, Energy metabolism obstacle; 5, Long-term abrosia or parenteral nutrition and abuse of antibiotics.By a large number of animal experiments and clinical studies have confirmed that intestine occur in varying degrees of histologiacal and ultrastructural changes after sever burn, including intestinal mucosa and submucosal edema, villus became shorted, and even intestinal cells necrosis, apoptosis. The intestinal mucosa and submucosal edema is an early pathological manifestations of intestinal damage, it not only affects the life activities of cells, but also hinders the spread of blood and tissue oxygen utilization, increases tissue cells ischemia and hypoxia. If given intervention at this stage, can improve the ischemic and hypoxic intestinal tissue, prevent aggravated damage of intestine and avoid the occurrence of MODS, improve the treatment rate of severe burns.Now widely recognized that the major cellular mechanism of tissue and organ edema after severe burn is that microvascular endothelial barrier structure is destroyed; After severe burns, the systemic inflammatory response starts, inflammatory cells are activated and aggregated, the release of a large number of inflammatory mediators and vasoactive substances, such as the histamine, bradykinin, oxygen free radicals, vascular permeability factor, hydrogen peroxide, and many other humoral factors, acted by complex ways, such as activating myosin light chain kinase (MLCK) that causes myosin light chain phosphorylation, then it activates the head of the ATP enzyme of myosin heavy chain, the energy is generated to cause the cell cytoskeleton actin filaments sliding, resulting in endothelial cell contraction, forming cell gap; In addition, the capillary endothelial cell membrane potential difference decreased, the Na+-K+-ATP enzymatic activity on the membrane is reduced, sodium and water molecules enter cells, potassium escape cells, the cells become spherical edema cells, that causes endothelial cell gap increased, so vascular permeability increases. The pathophysiological process is particularly evident after resuscitation by giving a large number of liquids. However, after severe burn, besides tissue edema has great related with the destruction of the microvascular endothelial cell barrier structure, Whether it has related with abnormal function of membrane water transport; As yet we have not found any reports.Transmembrane transport of water has two basic modes:1, Simple diffusion; 2, membrane protein mediated transport; The latter is the main form of transmembrane transport of water. Aquaporins(AQPs) is the membrane channel protein which has a specific transport function of water, at present there are 13 kinds of aquaporins in mammals(AQP0-12); In recent years, domestic and foreign scholars have more in-depth understanding on the molecular structure, physiological functions of aquaporins according to the research of molecular biology and physiology of animal models, and confirmed that aquaporins has played an important role in the formation of brain edema and pulmonary edema, the development of diabetes insipidus. AQP1 was found as the first aquaporin, widely distributed in many organ tissues, has great related with physiological and pathological state of organism. Such as towne and other people used respiratory adenovirus to cause adenovirus pneumonia in mice, found that AQP1 expression lower in mouse lung, suggested the reduction of AQP1 may be the important reason for water molecules gathering in interstitial lung, shew the related to AQP1 and pulmonary edema; Such as AQP1 exists in non-pigmented ciliary epithelium and trabecular meshwork endothelium of eyes, intraocular pressure will significantly reduce after AQP1 knockout; and so on. By immunohistochemistry, immunofluorescence scanning, in situ hybridization, PT-PCR and other methods, now it has been confirmed that AQP1 expresses widely in the capillaries, small blood vessels and the central lacteal endothelial cells of the digestive system, AQP1 is the important material which can mediate transmembrane transport of water molecules.Based on the understanding of AQP1, we propose:Is AQP1 involved in the formation of intestinal edema after severe burn?Through the establishment of rat model of severe burn, we observe water content of the small intestine and the expression of AQP1 at different stage after burn, and to clarify the association of AQP1 with the intestinal tissue edema after severe burns; and giving early enteral feeding, to understand improvement of the intestinal edema, whether which is associated with expression changes of AQP1; the research not only to provide a new idea to prevent intestinal edema after severe burn in clinic, but also to provide a useful reference to the mechanism of intestinal edema after severe burn.Objective1.To observe the water content and AQP1 dynamic expression of the small intestinal tissue of rats after severe burn, and the effect of giving early enteral feeding;2.Investigating the association of AQP1 with the small intestinal tissue edema after severe burns.Methods1.90 healthy adult Wistar rats were randomly divided into normal control group (group N) (n=6), simple burn group (group S) (n=42) and the early feeding group (group EF) (n=42). Group N, Group S were divided into seven time points(the 2th, 4th,8th,12th,24th,48th,72th hour),6 rats each time point. With 30% TBSAⅢ°burn rat model, using dry weight method, ELSIA and immunohistochemistry to observe and detect the water content and expression of AQP1 of the intestinal tissue at different time points after burn.2. Using SPSS 13.0 statistical analysis software for data analysis. The experiment is 3x7*6 factorial design, complete stochastic region design of two factors was applied and to understand the main effect and interaction of AQP1 expression in intestinal tissue and the time factor. Each time group, treatment group apply single factor variance analysis to analyze; In group EF and group S, the correlation analysis between AQP1 expression and water content in small intestinal tissue used Pearson connection, when P<0.05, the difference has statistical significance.Results1.After rats were severely burned, the water content of small intestinal tissue increased, through early enteral feeding, the water content of tissue can reduced. At time points after 4h, the water content of small intestinal tissues of group S are significantly higher than group N(P<0.05), The water content is peaked in 48h after burns (77.61±0.40%); In group EF, At 4,8,24,48,72h the water content of small intestinal tissues of group EF are significantly lower than group S(P<0.05).2.After rats were severely burned, the expression of AQP1 of small intestinal tissue reduced, through early enteral feeding, the expression of AQP1 can increased. In group N, AQP1 expresses in the capillaries, small blood vessels and the central lacteal endothelial cells of small intestinal tissue; At time points after 8h, the expression of AQP1 of group S are significantly lower than group N(P<0.05), the expression of AQP1 is valley in 48h after burns (9.48±0.73ng/ml); In group EF, At 24,48,72h the expression of AQP1 of group EF are significantly higher than group S(P<0.05).3.The water content of small intestinal tissue was negatively correlated with the expression of AQP1 in group S and group EF, coefficient correlation is-0.938 and -0.907(P<0.01), the correlation is closely.Conclusion1.AQP1 expresses in the capillaries, small blood vessels and the central lacteal endothelial cells of small intestinal tissue of normal rats.2. In early stage after rats were severely burned, the expression of AQP1 of small intestinal tissue reduced obviously, through early enteral feeding, the expression of AQP1 increased.3. In early stage after rats were severely burned, the water content of small intestinal tissue was negatively correlated with the expression levels of AQP1, the expression of AQP1 increased through early enteral feeding, It could increase the expression of AQP1 to reduce the degree of edema.