A Trichinella spiralis Trypsin Drives Macrophage M1 Polarization and Strengthens Cytotoxicity Killing Larvae via...

Trichinella spiralis, a food-borne zoonotic parasitic nematode with global distribution, poses a significant hazard to both public health and the safety of animal-derived meat products. Previous studies have identified a trypsin from T. spiralis, designated as TsTryp, within the excretory-secretory antigens (ESA) of intestinal infective larvae (IIL). Notably, the recombinant TsTryp (rTsTryp) was found to facilitate the T. spiralis larva invasion of gut epithelia, whereas anti-rTsTryp antibodies exerted a clear inhibitory effect on this larval invasion process. However, whether TsTryp regulates macrophage polarization in experimental T. spiralis infection and its molecular mechanisms are not clear. This present research intends to explore the functional significance of rTsTryp in macrophage polarization and cytotoxicity killing newborn larvae (NBL). The indirect immunofluorescence test verified specific binding between rTsTryp and RAW264.7 cells. qPCR, Western blot, and flow cytometry exhibited that rTsTryp induced the marked upregulation of iNOS expression, increased expression levels of p-NF-κB p65 and p-IκB-α, and elevated the proportion of CD86⁺ cells and drove the macrophage M1 polarization. qPCR and ELISA results further demonstrated pronounced elevation in proinflammatory cytokine (IL-6 and TNF-α) expression levels of macrophages following rTsTryp stimulation. Pretreating macrophages by the NF-κB inhibitor pyrrolidinecarbodithioic acid (PDTC) significantly abolished and reduced rTsTryp-increased expression levels of iNOS, p-NF-κB p65, and p-IκB-α and proinflammatory cytokine production. rTsTryp treatment also prominently strengthened macrophages' antibody-dependent cellular cytotoxicity (ADCC) killing NBL, whereas PDTC pretreatment significantly decreased this cytotoxicity. The findings indicated that rTsTryp specifically bound to macrophages and activated the NF-κB signal pathway, drove M1 polarization and increased proinflammatory cytokine expression, and enhanced the ADCC activity killing larvae.