Involvement of nitric oxide with activation of Toll-like receptor 4 signaling in mice with dextran sodium sulfate-induced colitis.

Ulcerative colitis is an inflammatory bowel disease characterized by acute inflammation, ulceration, and bleeding of the colonic mucosa. Its cause remains unknown. Increases in adhesion molecules in vascular endothelium, and activated neutrophils releasing injurious molecules such as reactive oxygen species, are reportedly associated with the pathogenesis of dextran sodium sulfate (DSS)-induced colitis. Nitric oxide (NO) production derived from inducible NO synthase (iNOS) via activation of nuclear factor κB (NF-κB) has been reported. It is also reported that stimulation of Toll-like receptor 4 (TLR4) by lipopolysaccharide can activate NF-κB. In this study, we investigated the involvement of NO production in activation of the TLR4/NF-κB signaling pathway in mice with DSS-induced colitis. The addition of 5% DSS to the drinking water of male ICR mice resulted in increases in TLR4 protein in colon tissue and NF-κB p65 subunit in the nuclear fraction on day 3, increases in colonic tumor necrosis factor-α on day 4, and increases in P-selectin, intercellular adhesion molecule-1, NO2(-)/NO3(-), and nitrotyrosine in colonic mucosa on day 5. These activated inflammatory mediators and pathology of colitis were completely suppressed by treatment with a NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, as well as an iNOS inhibitor, aminoguanidine. Conversely, a NO-releasing compound, NOC-18, increased TLR4 levels and nuclear translocation of NF-κB p65 and exacerbated mucosal damage induced by DSS challenge. These data suggest that increases in TLR4 expression induced by drinking DSS-treated water might be directly or indirectly associated with NO overproduction.

Tun X ，Yasukawa K ，Yamada K 《-》

The detrimental effect of nitric oxide on tissue is associated with inflammatory events in the vascular endothelium and neutrophils in mice with dextran sodium sulfate-induced colitis.

Yasukawa K ，Tokuda H ，Tun X ，Utsumi H ，Yamada K ... -  《-》

Zhikang Capsule ameliorates dextran sodium sulfate-induced colitis by inhibition of inflammation, apoptosis, oxidative stress and MyD88-dependent TLR4 signaling pathway.

Zhikang Capsule (ZKC) is a traditional Chinese medicine (TCM) modified from classic formulas Qi-Li-San (an ancient formula dating to Qing Dynasty) and Fu-Jin-Sheng-Ji-San (written into The Golden Mirror of Medicine). ZKC contains 14 kinds of materials and has been widely used for the clinical therapy of inflammatory bowel diseases (IBD) for a long time. However, the therapeutic mechanisms of ZKC are still unclear. To determine the protective effect of ZKC on dextran sodium sulfate (DSS)-induced colitis and explore the underlying mechanisms. C57BL/6 mice were fed with 3% DSS in drinking water for one week to induce experimental colitis. They were randomly assigned to six groups according to the treatment conditions. The histological changes of colon tissues were observed by hematoxylin and eosin (H&E) staining. The serum concentration of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-12) and anti-inflammatory mediators (IL-4 and IL-10) was detected by enzyme-linked immune sorbent assays (ELISAs). The production of MPO, SOD, MDA, NO, and caspase-3 was assessed by biochemical assay kits. The expression of iNOS, ICAM-1, and NF-ΚB was evaluated by immunohistochemistry staining. The levels of TLR4, MyD88, and TRAF6 were determined by western blot. Histologic analysis exhibited that ZKC alleviated the inflammation, loss of goblet cells, and submucosal edema induced by DSS. ZKC significantly suppressed the pro-inflammatory cytokines and promoted the anti-inflammatory mediators. The antioxidation of ZKC was indicated by increased activity of SOD and reduced production of MDA, NO, and iNOS in ZKC-treated mice. Furthermore, ZKC repressed the colonic expression of caspase-3 and the activity of the MyD88-dependent TLR4 signaling pathway. This research demonstrated the protective effect of ZKC on DSS-induced colitis. For the first time, we identified four therapeutic mechanisms of ZKC, including effective inhibition of the inflammatory responses, significant alleviation of intestinal epithelium apoptosis, considerable prevention of oxidative stress, and selective down-regulation of the MyD88-dependent TLR4 signaling pathway. With high therapeutic effects and low toxic effects, ZKC exhibits great superiority over western medicines in IBD treatment.

Fei L ，Xu K 《-》

Nitric Oxide Is Involved in Activation of Toll-Like Receptor 4 Signaling through Tyrosine Nitration of Src Homology Protein Tyrosine Phosphatase 2 in Murine Dextran Sulfate-Induced Colitis.

Tun X ，Yasukawa K ，Yamada KI 《-》

alpha-Phenyl-N-tert-butylnitrone provides protection from dextran sulfate sodium-induced colitis in mice.

Naito Y ，Takagi T ，Ishikawa T ，Handa O ，Matsumoto N ，Yagi N ，Matsuyama K ，Yoshida N ，Yoshikawa T ，Kotake Y ... -  《ANTIOXIDANTS & REDOX SIGNALING》