Protective effect of hypoxia-inducible factor-1α on brain injury in mice with necrotizing enterocolitis

Abstract

Objective To investigate the effects of hypoxia inducible factor-1α (HIF-1α) on the brain injury of necrotizing enterocolitis (NEC) mice. Methods Eighty-one C57BL/6 mice aged 5 d were randomly divided into 4 groups: Control group (CON, n=15, breastfed, in cages with their mothers), NEC group (n=24, fed in an incubator, with formula milk+hypoxia+oral lipopolysaccharide to induce NEC mouse model), DMOG group (n=19, given HIF-1α stabilizer DMOG on the base of NEC model), and 2ME2 group (n=23, given HIF-1α inhibitor 2ME2 on the base of NEC model). The mortality of mice was recorded during modeling. All mice were sacrificed in 4 d after modeling, and the intestinal pathological features of mice were observed by HE staining. Western blotting and immunohistochemical assay were performed respectively to detect the expression of HIF-1α protein in brain tissue and the numbers of activated microglia, astrocytes and oligodendrocytes in the hippocampus. The mRNA levels of inflammatory cytokines IL-1β and TNF-α were determined by RT-qPCR in brain tissue. Results As compared with the CON group, the mice of the NEC group showed intestinal tract damage, increased activated microglia (0.80±0.75 vs 4.00±0.63, P < 0.05) and astrocytes (P < 0.05) in the hippocampus, decreased number of oligodendrocytes (64.40±7.26 vs 45.60±2.80, P < 0.05), and higher levels of TNF-α, IL-1β and HIF-1α (P < 0.05). After intraperitoneal injection of HIF-1α stabilizer DMOG, the survival rate of mice in the DMOG group was increased (66.67% vs 84.21%, P < 0.05), and the intestinal injury was reduced. The activation of microglia (4.00±0.63 vs 1.60±0.49, P < 0.05) and astrocytes (P < 0.05) was inhibited, while the number of oligodendrocytes was elevated (45.60±2.80 vs 56.00±5.22, P < 0.05), and the expression of TNF-α and IL-1β was down-regulated (P < 0.05). However, intraperitoneal injection of HIF-1α inhibitor 2ME2 resulted in opposite outcomes. Conclusion HIF-1α is protectively up-regulated in the brain of NEC mice, and its stable and high expression reduces the neuroinflammation in the brain of NEC mice, exerting a protective effect on the brain.

Keywords

• necrotizing enterocolitis
• brain injury
• hypoxia-inducible factor
• neuroinflammation
• premature infants