Stress, Nutrition, and Intestinal Immune Responses in Pigs — A Review

Lee, In Kyu; Kye, Yoon Chul; Kim, Girak; Kim, Han Wool; Gu, Min Jeong; Umboh, Johnny; Maaruf, Kartini; Kim, Sung Woo; Yun, Cheol-Heui

Mycotoxin is one of the major factors to contaminate animal feed causing nutritional stress (Weaver et al., 2014a) . Deoxynivalenol (DON) disrupted the expression of the TJ proteins such as ZO-1, occludin and claudin-3, and permeability of porcine gut epithelial cells within 48 hrs 2016) . DON stimulated pro-inflammatory cytokines like TNF-α, IL-6, and IL-1β expression in jejunum and ileum (Bracarense et al., 2012) and increased the number of lymphocytes (Wu et al., 2015) . It is apparent that TLR2 ligand can prevent the damage of porcine gut epithelial cells treated with DON (Gu et al., 2016) . Fumonisin B1 (FB1) increased the permeability in porcine jejunum at over 10 days post stimulation (Bouhet et al., 2004) whilst DON took only 2 days to reach the similar level of the permeability . FB1 appeared to down-regulate the expression of IL-8 without changing other inflammatory cytokines, IL-6, IL-1β, IL-12p40, and TNF-α (Bouhet et al., 2006) . It is likely that FB1 has relatively weak immunological effects on porcine gut epithelial cells when compared to those of DON. Chronic feeding with the combination of aflatoxin and DON for 33 to 42 days increased the number of monocytes and white blood cells coincident with high concentration of TNF-α in blood while a single treatment did not show such an impact (Chaytor et al., 2011; Weaver et al., 2013) . It was noted that a combination of DON and zearalenone feeding for a long time increased twice the level of 8-hydroxydeoxyguanosine indicating oxidative stress, together with DNA oxidative damage (Weaver et al., 2014b) . For inflammatory cytokines including IL-12/IL-23p40 and IL-1β, and vasoactive intestinal peptides were increased in ileum Peyer's patches after 42 days feeding of zearalenone (0.1 mg/kg) to pigs (Obremski et al., 2015a) . While feeding of zearalenone (0.1 mg/kg) to pigs for 28 days induced a reduction of CD21 + B cells while increasing interferon (IFN)-γ concentration in ileocecal lymph nodes (Obremski et al., 2015b) suggesting that it may alter B cell responses. In addition, T-2 toxin reduced viability of intestinal epithelial cells in pigs infected with Salmonella Typhimurium. Although T-2 toxin did not alter the integrity of porcine gut epithelial cells, it increased translocation of bacteria (Verbrugghe et al., 2012) . Chronic exposure of T-2 toxin at low dose by feeding for 21 days decreased the proportion of CD21 + B cells gradually from ileal Peyer's patches. Besides, gene expression profiles of cytokines in T cells, such as IL-2, IL-4, and IFN-γ were not changed under the same condition (Obremski et al., 2013) .