Effects And Mechanism Of L-Theanine On Intestinal Mucosal Innate Immunomodulatory Based On NLRs Receptors Signaling Pathways

The intestine is not only an important place to absorb nutrients, but also an important immune organ which against various bacteria and toxins infecting. Enterotoxigenic Escherichia Coli. (ETEC) can cause diarrhea and severely reducing the capabilities of digestion, absorption and defense. L-theanine is characteristic amino acid of tea, L-theanine can promote growth, antioxidant enzyme activities and the immune system, but there is no report about the effect of L-theanine on bacterial induced-intesine injury.In this study, SPF grade Balb/c female mice as experimental animals, after adaptive feeding 3ds, the mice were pre-treated orally with different dosages of L-theanine once daily for 30ds before ETEC E44813 intraperitoneal injection, sampling after 5hs,on the one hand analyzed the the weight change in mice breeding process, measured activities of ileum homogenate Catalase (CAT), Glutathione peroxidase (GSH-Px), Malondialdehyde (MDA) and Inducible nitric oxide synthase (INOS), studied the pathological changes of intestinal and expression of serum Tumor necrosis factor-? (TNF-?), Interleukin-1? (IL-1?) and Intercellular cell adhesion molecule-1(ICAM-1), aimed to explore the protective effects of L-theanine on intestinal of ETEC immune stress model in mice; On the other hand analyzed the effects of L-theanine on expression of genes and proteins of NODI and NOD2 signaling pathyways in Ileum, aimed to explore the protection mechanisms of L-theanine of ETEC immune stress model in mice, find out the ways and mechanisms of L-theanine in intestinal mucosal innate immunity. Results show that:1. Pretreatment with L-theanine at different dosages significantly increased mouse body weight; lowered the levels of ileum homogenate MDA and iNOS, improved the activity of ileum homogenate CAT, GSH-Px, decreased the expression of serum TNF-?? IL-1? and ICAM-1, and improved pathological structure of jejunum tissue. These data demonstrated that pre-treatment with L-theanine prevented ETEC-induced intestinal injury through inhibiting TNF-?? IL-1? and ICAM-1, and inflammatory reaction and enhancing intestinal antioxidant abilities.2. L-theanine effect on the expression of gene mRNA in intestinal NLRs signaling pathway. L-theanine increase the expression of NOD1 mRNA by down Psma7 mRNA level, enhancing the reation between NOD1 and bacterial peptidoglycan, L-theanine doen the overexpression of NOD2, RIP2 and TAK1 mRNA; Decreased and improved NOD1/NOD2-mediated NF-?B and MAPK signaling pathways,respectively; Induced overexpression of IL-1? and TNFa mRNA and aggravated inflammatory reaction, aimed to protect intestinal tract by strengthen intestinal immune response.3. L-theanine effect on the expression of protein in intestinal NLRs signaling pathway. L-theanine inhibit the overexpression of both NODI and NOD2 proteins, thereby inhibiting expression of its common downstream RIP2 protein. L-theanine inhibit excessive activation of NOD-NF-?B signaling pathway by inhibiting the overexpression of NOD1/NOD2 proteins and nuclear protein NF-?B p65; Improved the phosphorylation of p38 and JNK1+JNK2, mediated the activation of NOD1-/NOD2-MAPK-p38/-JNK signaling pathway, And inhibit overexpression of IL-1? and TNFa protein, so that L-theanine have effects of anti-inflammatory.Conclusion:Pretreatment with L-theanine improve illness severity and pathological injury of ileum tissue from ETEC infection, and protect intestinal by inhibiting the level of the inflammatory cytokine and lipid peroxidation, improving antioxidant capacity. Its mechanism:In the level of genetic, decreased and improved NOD1-/NOD2-mediated NF-?B and MAPK signaling pathways, respectively; Induced overexpression of IL-1? and TNFa mRNA and aggravated inflammatory reaction, aimed to protect intestinal tract by strengthen intestinal immune response; In the level of protein, L-theanine inhibit activation of NOD-NF-?B pathway, mediated the activation of NOD1/NOD2-MAPK p38/JNK signaling pathway. And inhibit overexpression of IL-1? and TNFa protein, so that L-theanine have effects of anti-inflammatory.