RESUMEN
Objective:To investigate the effect of macrophage polarization in the pathogenesis of necrotizing enterocolitis(NEC).Methods:C57BL/6 mice were chose to construct the NEC model.The preterm pups were randomly assigned into the control group( n=10) and the NEC group( n=19). The pups in the control group were breastfed by mothers while the NEC group were treated with hypoxia, hypothermia, hypertonic feeding and lipopolysaccharide treatment.The intestinal tissues from the lower part of duodenum to the colon were collected after the pups were born after 96 hours.HE staining was used to observe the intestinal histological structure.Intestinal mucosal permeability was detected by the measurement of concentration of FD70 in plasma after gastric gavage.The expression of Pan-keratin of intestinal epithelium was detected by immunofluorescence histochemistry.Enterocyte apoptosis was detected by TUNEL staining.The expression of CD86 and CD206 protein were determined by western blotting and the percentage of M1 and M2 macrophages was calculated by flow cytometry.RT-PCR was used to detect the expression of mRNA levels of granulocyte-macrophage colony stimulating factor, interleukin(IL)-6, IL-10 and IL-12. Results:Compared with the control group, the pups in the NEC group had low survival rate(100.0% vs.36.8%), different level of intestinal injury, incomplete integrity of intestinal epithelium, increased mucosal permeability(1.53±0.80 vs.14.32±1.27, P<0.05)and enterocyte apoptosis(1.9%±1.1% vs.7.6%±2.6%, P<0.05). Western blotting showed that the expression of CD86 protein(1.00±0.01 vs.1.50±0.10, P<0.05) increased while CD206 protein decreased(1.00±0.01 vs.0.60±0.05, P<0.05) in the NEC group.Flow cytometry showed that the percentage of CD68 + CD86 + M1 macrophages increased(1.90%±0.19% vs.10.20%±0.38%, P<0.05) while the CD68 + CD206 + M2 macrophages decreased(5.8%±0.33% vs.3.7%±0.56%, P<0.05) in the NEC group.The expression of the mRNA levels of pro-inflammatory cytokines, granulocyte-macrophage colony stimulating factor(1.00±0.05 vs.1.83±0.17, P<0.05), IL-6 (1.00±0.13 vs.2.00±0.58, P<0.05) and IL-12(1.00±0.05 vs.1.49±0.22, P<0.05) increased and the anti-inflammatory cytokine IL-10(1.00±0.22 vs.0.09±0.01, P<0.05) decreased. Conclusion:Polarization of macrophages towards the pro-inflammatory M1 subtype plays an important role in the pathogenesis of NEC.