Effect Of Murine Norovirus On The Intestinal Injury In Neonatal Mouse With Necrotizing Enterocolitis

Objective:To determine the effects of murine norovirus on the intestinal injury in neonatal mouse with necrotizing enterocolitis（NEC）,and to discuss the mechanism of murine norovirus on NEC.Methods:Seventy-five 1-day-old C57BL/6J mice were randomly divided into 3 groups,a control group,a necrotizing enterocolitis group with phosphate buffer saline（PBS+NEC group）,and a murine norovirus intervention group（MNV+NEC group）.The neonatal mice in the control group were living with their mothers without submitting to stress.All the mice in NEC group were stressed with hypoxia,cold stress and gavage feeding to induce the model of NEC,and intervened with phosphate buffer saline,murine norovirus,respectively.All the mice in NEC group were handled with ampicillin（25mg/kg）,metronidazole（50mg/kg）,vancomycin（10mg/kg）,Piperacillin and tazobactam（100mg/kg）in ten consecutive days at the same time before building the model of NEC.The weights of mice were measured in four consecutive days at the same time.All mice were killed on the 14^th day via decapitation and 2 cm sections of the proximal intestines of ileocecal junction were harvested for histopathologic evaluation.The mRNA expression of TLR-3,MDA-5,IL-6,IL-10,IL-1βand IL-22were tested by quantitative real-time PCR.The counts of type 3 innate lymphoid cells（ILC3）were detected by Flow cytometry.The levels of IL-10in intestine tissues were evaluated by ELISA.Results:Compared with the control group,the weight of the two groups（MNV+NEC group and PBS+NEC group）decreased and the intestinal injury were obviously aggravated.However,the weight of MNV+NEC group decreased less fast than the PBS+NEC group,and the intestinal lesions of MNV+NEC group were less severe than the PBS+NEC group.The MNV+NEC group exhibited higher gene expression of IL-10and IL-22（P<0.05）,higher expression of IL-10 proteins（P<0.05）in intestine tissues and lower gene expression of IL-6,IL-1β（P<0.05）in intestine tissues compared with the PBS+NEC group.No statistically significant difference for the gene expression of TLR-3,MDA-5 and the counts of ILC3 were found between the MNV+NEC group and PBS+NEC group.Conclusion:This experiment successfully established the animal models of necrotizing enterocolitis（NEC）in newborn mice.The murine norovirus plays a protective role in intestinal injury in neonatal mouse with necrotizing enterocolitis（NEC）.the mechanism may be related with down-regulating IL-6 and IL-1β,up-regulating IL-10 the role of the function of ILC3 with secreting IL-22 cytokines.