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

It has been shown that destruction of tight junction (TJ) proteins, such as claudin 1/3 and occludin, caused an increase of the permeability of porcine gut epithelial cells . Interestingly, however, HS induced increase of the gut permeability without changing the expression of the TJ proteins while there was up-regulation of GLUT-2 (Pearce et al., 2013) . It is to note that activation of SGLT 1, NA + and glucose co-transporter causes an increase in the permeability (Turner et al., 1997) . Thus, the expression change of glucose transporter on epithelial cells in porcine by HS is directly associated with the permeability. Although, HS increased the permeability and the concentration of endotoxins in blood was increased over three times, inflammatory cytokines, such as interleukin (IL)-1β, IL-8 and tumor necrosis factor (TNF)-α, were not up-regulated (Pearce et al., 2013) . Since it is well established that endotoxin (lipopolysaccharide, LPS) is strong inducer of the inflammatory cytokines this study left scope for discovering how this occurs. It is probable that either HS caused immune suppression in the animal (Meng et al., 2013) or LPS was not as high as it appeared due to i) a technical error, ii) structural differences (Trent et al., 2006) , iii) differential composition (Im et al., 2015; Lam et al., 2011) or iv) binding proteins of LPS (Lam et al., 2011; Im et al., 2015) . It could well be that HS together with LPS does not induce all pro-inflammatory cytokines and perhaps are linked with specific cytokines such as IL-17 and/or transforming growth factor-β (TGF-β) which are in relation with regulatory T (Treg) and Th17 T cells. For example, the colonization of probiotics, such as Lactobacillus rhamnosus strain GG and Bifidobacterium lactis Bb12, in gnotobiotic pigs impacted to stable the balance of TGF-β and IL-17 after rotavirus challenge (Chattha et al., 2013) . It has been also suggested that heat shock protein 70 (Pearce et al., 2014) and myeloperoxidase activity as the activation marker of neutrophils (Pearce et al., 2013) were increased under HS in porcine gut. This indirectly suggests that unlike the previous report by the same group, HS induces the inflammatory responses in intestine of pigs.