title: Retinoic acid attenuates lipopolysaccharide-induced inflammatory responses by suppressing TLR4/NF-kappaB expression in rat mammary tissue.
abstract: The retinoids, a group of natural or synthetic derivatives of vitamin A, exert various anti-neoplastic and immunomodulatory actions. Recent studies have demonstrated that retinoic acid protects rats against lipopolysaccharide (LPS)-induced mastitis, but the mechanism of action is unclear. In the present study, an LPS-induced rat mastitis model and primary cultures of rat mammary epithelial cells were used to investigate the effect of retinoic acid on the TLR4/NF-kappaB signaling pathway. The data indicated that toll-like receptor 4 (TLR4) gene expression reached its peak value earlier in retinoic acid-treated rats than in the control group, and that retinoic acid significantly decreased NF-kappaB DNA binding activity and the level of IL-1beta in the mammary gland. The animal study result was confirmed by an in vitro cell culture system trial. TLR4 protein expression and NF-kappaB DNA binding activity were significantly decreased in primary rat mammary epithelial cells pretreated with 1mumol/l retinoic acid at 1h post-LPS stimulation. IL-1beta gene expression was also significantly decreased at 2, 4 and 8h post-LPS stimulation. These findings demonstrate that direct action by retinoic acid leads to attenuation of the LPS-induced inflammatory response by suppression of the TLR4/NF-kappaB signalling system, thereby providing a novel explanation for the underlying effect proposed for retinoic acid in the protection of mammary tissue during LPS-induced acute mastitis.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China.
authors.forename: Beibei
authors.initials: B
authors.lastname: Gu
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Miao
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Fa
authors.forename: Jingye
authors.initials: J
authors.lastname: Lu
authors.forename: Sixiang
authors.initials: S
authors.lastname: Zou
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D007165:Immunosuppression Therapy; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000473:pathology; D008413:Mastitis / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014212:Tretinoin / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D016328:NF-kappa B; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014212:Tretinoin