Preliminary Study About Antenatal Dexamethasone Impacting The Expression Of Toll-like Receptor4in Newborn Rats With Necrotizing Enterocolitis

Objective To explore the intestinal development and intestinal TLR4expression of neonatal rats whose mothers accepted antenatal dexamethasone injection.Methods12pregnant Sprague-Dawley (SD)rats were randomly divided into normal control group, prenatal dexamethasone group (DEX group), prenatal normal saline group (NS group), n=4. On the gestational day16,17and18, DEX (0.5mg/(kg·d)) were injected intramuscularly to the rats of the DEX group whereas normal saline (0.3ml/d) were to those of NS group respectively. Normal control group was without any treatment. All rats of three groups were delivered spontaneously (term=22d). The newborn rats of each group were sacrificed respectively on the1-day-postnatal,3-day-postnatal and5-day-postnatal, and proximal intestines of ileocecal junction were undertaken pathological sectioning. Intestinal villus height was measured by Microscope after hematoxylin and eosin (HE) dyeing and the expression of TLR4protein was detected by immunohistochemical method. Total RNA was extracted from the rest of intestinal tissue and the expression of TLR4mRNA was detected by Quantitative real-time PCR.Results The small intestine length and weight and intestinal villus height increased gradually with age after birth. However, both the TLR4protein and mRNA expression in small intestine reduced gradually (P <0.05). Small intestine length was significantly longer and weight was also higher in DEX group than those of in the normal control group and NS group on the1,3days-old (P<0.05). Both TLR4protein and mRNA expression of small intestine in DEX group was significantly lower than those of in the other two groups (P<0.05). On the1,3,5days-old, the intestinal villus height in DEX group was significantly higher than that of in the other two groups (P<0.05). At each time point, the length and weight of small intestine, intestinal villus height, TLR4protein and mRNA expression of small intestine in NS group showed no significant differences Compared with the normal control group at each time point (P>0.05). Conclusion Antenatal dexamethasone could increase the small intestine length and weight of early days of newborn rat, increase intestinal villi height, and promote the maturation of small intestinal morphology; Antenatal dexamethasone could reduce the intestinal TLR4expression of early days of newborn rat. Objective To observe the influence of antenatal dexamethasone (DEX) treatment on the expression of toll-like receptor4(TLR4) in the intestines of neonatal rats with necrotizing enterocolitis (NEC) in order to explore its protective effects and potential mechanisms on neonatal rats with NEC.Methods Twelve pregnant SD rats were randomly divided into three groups with4in each, normal control group, DEX group, as well as normal saline group (NS group). On the gestational day16,17and18, DEX (0.5mg/(kg· d)) were injected intramuscularly to the rats of the DEX group whereas normal saline (0.3ml/d) were to those of NS group respectively. All rats of three groups were delivered spontaneously (term=22d). NEC model of DEX group and NS group was established by artificial feeding, cold exposure after hypoxic-reoxygenation treatment as well as LPS intragastric administration. General conditions were observed in each group. All the subjects were sacrificed on the5th day after birth and proximal intestines of ileocecal junction were undertaken pathological sectioning. Tissue damage was scored by HE dyeing which based on histological changes. The expression of TLR4protein was detected by immunohistochemical method. Total RNA was extracted from the rest of intestinal tissue and the expression of TLR4mRNA was detected by Quantitative real-time PCR.Results The incidence of NEC in DEX group was lower than NS group. The rats of NS group appeared typical NEC symptoms, which were later and milder in the rats of DEX group. There were not NEC symptoms in rats of normal control group. The histopathological scores of DEX and NS groups were significantly higher (P<0.05) than those of normal control group, whereas which in DEX group were significantly lower (P<0.05) than those of NS group. The expression of TLR4protein in the rats of DEX and NS groups significantly increased (P<0.05) compared with normal control groups, and which in the rats of DEX group was significantly higher (P<0.05) than those of NS group. The changes of mRNA expression of TLR4were basically consistent with the changes on protein expression.Conclusion Antenatal DEX has a protective effect on the animal model of NEC probably by decreasing the expression of TLR4so as to play an anti-inflammatory effect.