“…First, weaning stress disrupts the intestinal mucosal mechanical barrier by reducing the expression of tight junction proteins ( 28 , 30 , 83 – 85 ), which makes it easier for bacteria and toxins to break through the intestinal mucosal barrier, and cause the release of a variety of cellular inflammatory factors, thereby leading to the occurrence of intestinal inflammation ( 156 ). Second, weaning stress disrupts the intestinal chemical barrier by inhibiting goblet cell differentiation and mucins secretion ( 41 , 97 ), and decreased mucins secretion further disrupts the intestinal mechanical barrier ( 99 ), immune barrier ( 100 ), and microbial barrier ( 98 ). Third, weaning stress disrupts the intestinal chemical barrier by promoting the secretion of inflammatory factors ( 13 , 14 , 28 , 30 , 117 – 120 ), while pro-inflammatory cytokines including IL-1β, TNF-α, and IFN-γ, have important intestinal TJ barrier-modulating actions ( 157 , 158 ).…”