Li Cui1, Liang Feng1, Zhen Hai Zhang1, Xiao Bin Jia1. 1. Key Laboratory of New Drug Delivery Systems of Chinese Materia Medica, Jiangsu Provincial Academy of Chinese Medicine, Jiangsu, Nanjing 210028, PR China.
Abstract
BACKGROUND: Baicalin holds a protective effect on inflammatory responses in several diseases. However, its molecular mechanism of anti-inflammatory activity on ulcerative colitis (UC) remains unknown. The present study was conducted to verify whether the anti-inflammation effect of baicalin on experimental colitis is via inhibiting TLR4/NF-κB pathway activation. METHODS: The inflammatory response in RAW264.7 cells was induced by LPS and in rats by intrarectal administration of TNBS. Western blot analysis was carried out to examine toll-like receptor 4 (TLR4), NF-κB, p-NF-κB p65, IκB and p-IκB protein expressions in cells. Furthermore, intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), cyclo-oxygenase-2 (Cox-2), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 levels in cell supernatant and rat serum were detected by appropriate kits. An immunohistochemical assay was applied to examine TNF-α and IL-1β protein expression in colon tissues and TLR4 and p-NF-κB p65 protein expressions in RAW264.7 cells. RESULTS: Baicalin ameliorates the considered inflammatory symptoms of induced colitis. It could also down-regulate pro-inflammatory mediators in the colon mucosa. The decline in the production of pro-inflammatory cytokines was correlated with the decrease in mucosal TLR4 protein expression. The expression of p-NF-κB p65 protein was significantly decreased, which correlated with a similar decrease in p-IκB protein. Consistent with the in vivo results, baicalin blocked LPS-stimulated nuclear translocation of p-NF-κB p65 in mouse macrophage RAW264.7 cells. CONCLUSIONS: The present study indicates for the first time that the mechanism for baicalin on abrogating experimental colitis was targeted inhibition of the TLR4/NF-κB pathway activation.
BACKGROUND: Baicalin holds a protective effect on inflammatory responses in several diseases. However, its molecular mechanism of anti-inflammatory activity on ulcerative colitis (UC) remains unknown. The present study was conducted to verify whether the anti-inflammation effect of baicalin on experimental colitis is via inhibiting TLR4/NF-κB pathway activation. METHODS: The inflammatory response in RAW264.7 cells was induced by LPS and in rats by intrarectal administration of TNBS. Western blot analysis was carried out to examine toll-like receptor 4 (TLR4), NF-κB, p-NF-κB p65, IκB and p-IκB protein expressions in cells. Furthermore, intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), cyclo-oxygenase-2 (Cox-2), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 levels in cell supernatant and rat serum were detected by appropriate kits. An immunohistochemical assay was applied to examine TNF-α and IL-1β protein expression in colon tissues and TLR4 and p-NF-κB p65 protein expressions in RAW264.7 cells. RESULTS: Baicalin ameliorates the considered inflammatory symptoms of induced colitis. It could also down-regulate pro-inflammatory mediators in the colon mucosa. The decline in the production of pro-inflammatory cytokines was correlated with the decrease in mucosal TLR4 protein expression. The expression of p-NF-κB p65 protein was significantly decreased, which correlated with a similar decrease in p-IκB protein. Consistent with the in vivo results, baicalin blocked LPS-stimulated nuclear translocation of p-NF-κB p65 in mouse macrophage RAW264.7 cells. CONCLUSIONS: The present study indicates for the first time that the mechanism for baicalin on abrogating experimental colitis was targeted inhibition of the TLR4/NF-κB pathway activation.