Effects of Toll-like Receptor Ligands on the Expression of Proinflammatory Cytokines and Avian <i>β</i>-defensins in Cultured Chick Intestine

Abstract

Few studies have focused on the regulation of cytokine and avian β-defensin (AvBDs) expression for promoting immune defense in the avian intestine. The aim of this study was to investigate the effects of different Toll-like receptor (TLR) ligands (bacterial patterns) on the expression of proinflammatory cytokines (IL-1β and IL-6) and AvBDs (AvBD1, AvBD4, and AvBD7) in the chick intestine. The ileum and cecum of 3-day-old chicks were collected and examined histologically to identity the cells present in the intestinal mucosa. Other tissues were cultured with or without the TLR2, TLR4, and TLR21 ligands-Pam3CSK4, LPS, and CpG-ODN-for 1 or 3 h. The gene expression profiles of proinflammatory cytokines and AvBDs were determined in these tissues using real-time polymerase chain reaction (PCR). The mucosa of the ileum and cecum contained leukocytes, luminal and crypt epithelial cells, and other enterocytes. Pam3CSK4 tended to downregulate the expression of IL-1β, AvBD1, and AvBD7 in the ileum but upregulated their expression in the cecum. LPS downregulated the expression of IL-1β and IL-6 in both the ileum and the cecum, whereas it upregulated the expression of AvBD1, AvBD4, and AvBD7 in the cecum. CpG-ODN upregulated the expression of IL-6 and AvBD7 in the ileum and IL-1β in the cecum, and downregulated the expression of IL-1β and AvBDs in the ileum. We suggested that the expression levels of proinflammatory cytokines and AvBDs in the chick intestine are affected by TLR2, TLR4, and TLR21 ligands. Thus, these innate immune factors may be modulated by the luminal microbe complex in the intestine.

Effects of Newcastle Disease/Infectious Bronchitis Vaccine and Feeding Yeast Products on the Innate Immune System in the Proventriculus and Ileum of Broiler Chicks

“…The current study revealed that five AvBDs and Cath1 were expressed in the proventriculus and ileum ( Figs. 4 and S1), supporting previous reports ( Mohammed et al, 2015 ; Terada et al, 2018 , 2020c ). We previously reported that ND/IB vaccination did not affect the gene expression of these antimicrobial peptides in the proventriculus, although the levels of some AvBD peptides increased following vaccination ( Yoshimura et al, 2022 ).…”

“…Previous studies in different organisms, including invertebrates (Kurtz, 2005) and mammals (de Bree et al, 2018;Netea et al, 2011Netea et al, , 2020van der Meer et al, 2015), suggested that vaccinations may induce trained innate immunity. The Bacillus Calmette-Guérin vaccine was reported to induce innate immune training by increasing histone modification and cytokine production in immune cells in response to agents unrelated to the vaccine antigen (Kleinnijenhuis et al, 2012(Kleinnijenhuis et al, , 2014.…”

Modulation of the innate immune system by lipopolysaccharide in the proventriculus of chicks inoculated with or without Newcastle disease and infectious bronchitis vaccine

“…Fourteen AvBDs (AvBD1–14) and 4 cathelicidins (CATH1–3 and CATH-B1) with broad-spectrum antimicrobial activity have been identified ( Hong et al, 2012 ; Wang et al, 2020 ). Regulation of the expression of proinflammatory cytokines and antimicrobial peptides by TLR ligands and pathogenic microbes is reported in the chicken oviduct and other organs ( Cuperus et al, 2013 ; Abdel-Mageed et al, 2014 ; Kamimura et al, 2017 ; Terada et al, 2020b ). Mohammed et al, who examined the effects of LPS and probiotics on the gene expression of antimicrobial peptides in the chick gastrointestinal tract, reported that the expression of AvBD6 and 12 under LPS stimulation was enhanced by probiotics in the proventriculus ( Mohammed and Radey, 2021 ), whereas CATHs expression was not affected ( Mohammed et al, 2016 ).…”

Effects of Probiotics <i>Lactobacillus reuteri</i> and <i>Clostridium butyricum</i> on the Expression of Toll-like Receptors, Pro- and Anti-inflammatory Cytokines, and Antimicrobial Peptides in Broiler Chick Intestine

“…TLR21 recognizes unmethylated CpG-oligodeoxynucleotides (ODN) of bacteria and viruses ( Keestra et al , 2010 ). The expression of TLR 1–5, 7, 15, and 21 in the different intestinal segments has been revealed in chicks ( Mackinnon et al , 2009 ), and the stimulation of TLR ligands modulated the expression of innate immune factors, namely antimicrobial peptides and cytokines in the chick intestine ( Terada et al , 2020 ).…”