| Objective:The incidence rate and mortality of sepsis in China are higher than those in western developed countries.The mortality rate is high,which leads to millions of deaths each year.Sepsis 3.0 defines sepsis as a life-threatening organ dysfunction caused by host's maladjustment to infection.The gut is the largest reservoir of bacteria in the human body.Under various stimulation,the intestinal immune function is inhibited,the integrity of intestinal mucosa is destroyed,and the intestinal barrier function is damaged.It is not only the main reason for the intestinal flora shift in sepsis,but also can aggravate the systemic inflammatory response.The systemic inflammatory response damages the gut again.The two are causal and promote each other,and may eventually cause septic shock and multiple organ dysfunction syndrome(MODS).Therefore,the gut is considered as the "central organ" and"motor" of sepsis.How to prevent and treat sepsis induced intestinal mucosal barrier injury is still a major problem in the clinical treatment of sepsis,which is worthy of further exploration and research.Butyric acid is a short chain fatty acid with four carbon atoms,which is the metabolite of intestinal bacteria.It is a kind of short chain fatty acid with the strongest anti-inflammatory effect.It has been proved that butyric acid can play an anti-inflammatory effect in vivo and in vitro,reduce the inflammatory reaction of intestinal epithelial cells,and play a protective role in the pathological damage caused by inflammatory diseases.A variety of treatments for critically ill patients,such as enteral nutrition,proton pump inhibitors,catecholamines and antibiotics,can significantly change the intestinal flora and reduce the production of butyric acid.So,during sepsis,supplement of this endogenous substance to the body can improve the intestinal inflammatory damage and protect the intestinal barrier?In this study,we used septic rat model to study the regulatory mechanism of sodium butyrate on intestinal inflammatory response and intestinal barrier function by supplementing exogenous sodium butyrate.Methods:Part I:200-220 g male SD rats were used to establish sepsis model by cecal puncture and ligation(CLP).The rats were killed at 6 h,12 h and 24 h after the establishment of the model,and the intestinal samples were collected to observe the intestinal inflammatory reaction by HE staining.The rats in the sodium butyrate treatment group were given different doses of sodium butyrate(200 mg/kg,400 mg/kg and 600 mg/kg)at 0 h and 8 h after the establishment of sepsis model.The mortality of rats in each group was compared by mortality analysis.The intestinal inflammation was evaluated by HE staining and inflammatory pathological score.The changes of TNF-? in intestinal tissue of rats in each group were detected by ELISA.Part II:Sepsis rat model was established by CLP.After CLP,the rats were injected with sodium butyrate(200 mg/kg)or normal saline(control),and then killed 12 hours after CLP.The expression of IL-6,TNF-?,IL-1?,IL-18 and iNOS was detected by RT-PCR,and the expression of IL-6 and TNF-? was detected by ELISA.The intestinal permeability was evaluated by the intestinal permeability to fluorescein isothiocyanate dextran(FD-4).The expression of tight junction protein was detected by Western blot.The differences of NF-?B p65 and I?-B? in nucleus and cytoplasm were analyzed by western blot and immunohistochemistry.Part ?:CLP method was used to establish sepsis rat model.200 mg/kg,400 mg/kg,600 mg/kg sodium butyrate was injected into caudal vein respectively,once every 8 hours.After 24 hours,the small intestine tissue samples were collected,and the expressions of inflammatory factors IL-6,IL-1?,IL-18 were detected by Western blot;the expressions of Caspase-1,P20 and NLRP3 were detected by Western blot;the apoptosis of intestinal parietal cells was detected by TUNEL staining,and the expressions of intestinal tight junction proteins ZO-1 and claudin-1 were detected by Western blot.Results:Part I:In this part,we successfully constructed sepsis model by SD rats.In this model,we observed that the rats' gut had inflammatory damage changes after 6 hours of modeling,which gradually increased from 12h to 24 h,which showed that the intestinal folds decreased,villi was short and blunt,atrophy,intestinal wall edema,accompanied by increased inflammatory index,and increased intestinal permeability.In addition,butyric acid showed the effect of improving the intestinal pathological injury in rats.The mortality analysis showed that the mortality of rats in the tail vein injection 200 mg/kg sodium butyrate group was significantly lower than that of the control group,and lower than that of 400 mg/kg and 600 mg/kg treatment group.The tail vein injection of 200 mg/kg sodium butyrate significantly reduced the intestinal inflammation in rats,and the decrease of TNF-? level in intestinal tissue was the most significant.Part ?:Compared with the control group,the pathological damage of intestinal mucosa of rats with sepsis was decreased after sodium butyrate treatment,the expression of Pro-inflammatory cytokines mRNA was significantly decreased,the intestinal passage of FD-4 was significantly reduced,and the expression level of Claudin-1 and ZO-1 increased.The NF-?B in the intestinal nucleus of rats was significantly decreased after sodium butyrate treatment,and the expression of I?-B?was significantly increased.Part III:Compared with the sham operation group,IL-6,IL-1? and IL-18 were increased after CLP operation.After 200 mg/kg sodium butyrate treatment,the content of inflammatory factors in the intestine of rats decreased significantly,but 400 mg/kg and 600 mg/kg groups were not obvious,even increased;the Caspase-1 was activated in the high-dose butyric acid treatment group,which showed that Caspase-1 and the level of P20 and NLRP3 increased;high dose of sodium butyrate increased the apoptosis of the cells in the gut propria,leading to the decrease of the expression of tight junction proteins ZO-1 and Claudin-1.Conclusion:1.This study suggests that sepsis can lead to intestinal tissue damage and increase intestinal permeability.Sodium butyrate can reduce the intestinal pathological damage caused by sepsis.Relatively low dose of sodium butyrate intravenous injection shows the effect of improving intestinal inflammatory response,which can be used as an intervention dose for further study.2.Sodium butyrate treatment significantly reduced the inflammatory response and improved the intestinal barrier function of septic rats.Sodium butyrate can increase the expression of I?-B?,then anchor NF-kB p65 more in the cytoplasm,reduce the entry of p65 into the nucleus,and then reduce the gene transcription and expression of proinflammatory mediators,so as to play a protective role in the intestinal tract.3.High dose butyric acid can activate Caspase-1 signaling pathway,which is opposite to reducing inflammation and improving intestinal barrier function. |
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