Abstract
BACKGROUND: Trichinella spiralis is an intestine- and tissue-dwelled parasitic nematode, the adult worms (AW) and muscle larvae parasitize in intracellular niche of intestinal epithelium and skeletal muscles of the same host, respectively. Intestinal infective larvae (IIL) and AW are two important enteral stages in T. spiralis infection. Their excretory-secretory proteins (ESP) disrupted host's intestinal epithelial barrier and mediated worm invasion. Meanwhile, T. spiralis could induce autophagy of murine intestinal epithelial cells. Autophagy usually plays a role in maintaining the structural and functional integrity of intestinal epithelial barrier. However, the function of autophagy in T. spiralis invasion and colonization in host remains unclear. The aim of this study was to investigate whether T. spiralis ESP induce enterocyte autophagy and whether ESP-induced autophagy protects intestinal epithelial barrier from ESP-induced destruction. METHODOLOGY/PRINCIPAL FINDINGS: The results of qPCR, Western blot and intracellular Ca2+ concentration assay showed that IIL and AW ESP induced autophagy of Caco-2 and RAW264.7 cells via increasing RACK1 expression and intracellular Ca2+ concentration, and activating AMPK/mTOR pathway. The results of qPCR, Western blot, indirect immunofluorescence test (IIFT), trans-epithelial electrical resistance (TEER) and paracellular permeability, and ELISA indicated that although IIL and AW ESP disrupted the cell monolayer integrity, autophagy induced by IIL and AW ESP also abolished and alleviated the ESP decreased-tight junctions expressions in Caco-2 monolayer, reduced the ESP-induced secretion of pro-inflammatory (TNF-α and IL-1β), and enhanced ESP-up-regulated production of anti-inflammatory cytokines (TGF-β). CONCLUSIONS: T. spiralis ESP-induced autophagy ultimately relieved and limited the damage of T. spiralis ESP to gut epithelial barrier, and ensured the T. spiralis survival and development in host gut mucosal epithelium.