Effects Of Simulated Microgravity And Intravenous Moxifloxacin On Intestinal Mucosal Barrier Of Rat With Abdominal Infection

Background and objective : With the rapid development of China’s manned space program, the space medical security and research should be strengthened. During the space flight and also in the environment of ground weightlessness trainning, astronauts are usually affected by a series of negative factors, and one of the main challenges is how to prevent and control the infections and inflammations. The gut is a vital organ and also is the biggest storehouse of bacteria and pool of endotoxin of the body. The intestinal mucosal barrier plays a crucial role in host defense against intestinal infection.The research on the effects of simulated microgravity and antibiotcs on intestinal mucosal barrier in the condition of abdominal infection has not been reported yet to our knowledge. This study was designed to investigte the effects of simulated microgravity and intravenous Moxifloxacin on intestinal mucosal barrier of rat with abdominal infection, and so as to provide a reference for the management of the infectious diseases in the weightlessness environment of spaceflight.Methods:Sixty healthy male adult Wistar rats were divided randomly into 6 groups(n=10), including groups of microgravity + abdominal-infection(MAI), microgravity +abdominal-infection + moxifloxacin(MAIM), microgravity + sham-operation(MSO),normal-gravity + abdominal-infection(NGAI), normal-gravity + abdominal-infection +moxifloxacin(NGAIM) and normal-gravity + sham-operation(NGSO).Tail-suspension was used to simulate the weightlessness animal model, and cecal ligation and puncture(CLP) model was used to mimic the abdominal infection.According to the experimental design, the CLP procedure was performed in the rats under simulated weightlessness for 48 hours. The injections of moxifloxacin hydrochloride were given via tail vein to the animals in group MAIM and group GAIM at 0 hour, 24 hours and 48 hours post-CLP respectively(30 mg/kg). At 60 hours post-CLP, blood and ileum samples were obtained for analysis of serum diamine oxidase(DAO) and D-lactate(D-LA) by radioimmunoassay, portal endotoxin by kinetic turbidimetric limulus test, Occludin and ZO-1 expression in mucous membrane of ileum by immunohistochemistry assay and western-blot, and Fas m RNA, Fasl m RNA and Bax m RNA by Real-time PCR respectively. The pathological changes of the mucous membrane of ileum were observed under light microscope and transmission electron microscope.Results:(1) The DAO activity, D-LA level in serum and endotoxin in portal vein of rats were significantly increased in group MAI and group NGAI, and significantly decreased in Moxifloxacin treatment groups, with lowest level in sham-operation groups(P<0.05). And they were significantly higher in animals under simulated microgravity than in animals under normal gravity(P<0.05).(2)Immunohistochemistry showed that Occludin and ZO-1 proteins stained as brown particles were mainly located in the cells membrane and cytoplasms with a continuous distribution in normal intestinal mucosa. Their staining was sparse in group MAI and group NGAI, recovered in Moxifloxacin treatment groups, and further deepened in group MSO and NGSO.(3) Western Blot showed that Occludin and ZO-1 proteins were at a lower level in group MAI and group NGAI, up-regulated after Moxifloxacin treatmen, and highest in group MSO and NGSO, with significant difference(P<0.05).(4) Real-Time PCR showed that Fas m RNA, Fasl m RNA and Bax m RNA wereexpressed abundantly in mucous membrane of ileum in group MAI and NGAI,down-regulated in group MAIM and NGAIM, and at a lowest level in group MSO and NGSO, with significant difference(P<0.05).(5) The light microscope showed that the interstitial edema and vascular congestion in ileum mucosa and submucosa with focal necrosis and inflammatory cell infiltration in animals with abdominal infection upon simulated microgravity. The pathological alterations in group MAIM and group NGAIM were alleviated than that of in group MAI and group NGAI. Under the transmission electron microscope, the intestinal mucosa ultrastructure revealed that there were irregular microvilli, microvilli missing, intercellular broadening, loose connection between glandular epithelial cells, cristae vague, dilatation of the endoplasmic reticulum, condensation of chromatin around the perinuclear membrane and obvious mitochondrial swelling, vacuolar degeneration and apoptosis bodies in the cytoplasm in groups of MAI and NGAI, and the alterations were severer in group MAI than in group NGAI. The pathological changes in group MAIM and group NGAIM were obviously improved compared with the group MAI and group NGAIM.Conclusion:The simulated microgravity aggravated the damage to intestinal mucosal barrier of rat with CLP-induced abdominal infection, and intravenous moxifloxacin could exert a unambiguous therapeutic effect on the pathological changes of intestinal mucosal barrier.