title: Toll-like receptor 4 and MYD88-dependent signaling mechanisms of the innate immune system are essential for the response to lipopolysaccharide by epithelial and stromal cells of the bovine endometrium.
abstract: Infection of the bovine endometrium with Gram-negative bacteria commonly causes uterine disease. Toll-like receptor 4 (TLR4) on cells of the immune system bind Gram-negative bacterial lipopolysaccharide (LPS), stimulating the secretion of the proinflammatory cytokines interleukin 1B (IL1B) and IL6, and the chemokine IL8. Because the endometrium is the first barrier to infection of the uterus, the signaling cascade triggered by LPS and the subsequent expression of inflammatory mediators were investigated in endometrial epithelial and stromal cells, and the key pathways identified using short interfering RNA (siRNA) and biochemical inhibitors. Treatment of endometrial cells with ultrapure LPS stimulated an inflammatory response characterized by increased IL1B, IL6, and IL8 mRNA expression, and IL6 protein accumulation in epithelial cells, and by increased IL1B and IL8 mRNA expression, and IL6 and IL8 protein accumulation in stromal cells. Treatment of endometrial cells with LPS also induced the degradation of IKB and the nuclear translocation of NFKB, as well as rapid phosphorylation of mitogen-activated protein kinase 3/1 (MAPK3/1) and MAPK14. Knockdown of TLR4 or its signaling adaptor molecule, myeloid differentiation factor 88 (MYD88), using siRNA reduced the inflammatory response to LPS in epithelial and stromal cells. Biochemical inhibition of MAPK3/1, but not JNK or MAPK14, reduced LPS-induced IL1B, IL6, and IL8 expression in endometrial cells. In conclusion, epithelial and stromal cells have an intrinsic role in innate immune surveillance in the endometrium, and in the case of LPS this recognition occurs via TLR4- and MYD88-dependent cell signaling pathways.
authors: Institute of Life Science, School of Medicine, Swansea University, United Kingdom. j.cronin@swansea.ac.uk
authors: James G
authors: JG
authors: Cronin
authors: Matthew L
authors: ML
authors: Turner
authors: Leopold
authors: L
authors: Goetze
authors: Clare E
authors: CE
authors: Bryant
authors: I Martin
authors: IM
authors: Sheldon
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004717:Endometrium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D055785:Gene Knockdown Techniques; D007113:Immunity, Innate / Q000502:physiology*; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048308:Mitogen-Activated Protein Kinase 14 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D017154:Stromal Cells / Q000187:drug effects* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
chemical_list: D053583:Interleukin-1beta; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D034741:RNA, Small Interfering; D051197:Toll-Like Receptor 4; D019950:Mitogen-Activated Protein Kinase 1; D048308:Mitogen-Activated Protein Kinase 14; D048052:Mitogen-Activated Protein Kinase 3