Human β-defensin-3 reduces excessive autophagy in intestinal epithelial cells and in experimental necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm newborns. Intestinal barrier dysfunction is one key event in NEC pathogenesis. Human β-defensin-3 (hBD3), one member of cationic host defence peptides, was reported to reduce the development of necrotizing enterocolitis in a neonatal rat model. And autophagy was induced in the intestine of human and animals with NEC. We hypothesized that regulation of autophagy might play a critical role in hBD3-mediated protection against NEC injury. Autophagy activity was evaluated both in intestinal epithelial cells and in NEC models. Newborn Sprague-Dawley rats were divided randomly into four groups: Control + NS, Control + rapamycin, NEC + NS, and NEC + hBD3. Body weight, histological score, survival time, enterocyte migration and mucosal barrier were recorded. Our results showed that hBD3 pretreatment could effectively inhibit autophagy activity in cultured IEC-6 and Caco2 enterocytes, and CXCR4 might be involved in hBD3-mediated autophagy suppression. Moreover, hBD3-induced inhibition of autophagy significantly promoted the intestinal epithelial cell migration by wound healing assay and transwell migration assay. In the rat model of NEC, hBD3 could noticeably reduce the expression of autophagy-activated proteins, down-regulate the expression of inflammatory mediators, and promote the mucosal integrity. Our data suggest an additional role of hBD3-mediated protection against intestinal mucosal injury: inhibition of over-activated autophagy in enterocytes.