Effects of garlicin on apoptosis in rat model of colitis

Natural Products: Experimental Efficient Agents for Inflammatory Bowel Disease Therapy

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Inflammatory bowel disease (IBD) is a chronic, elusive disorder resulting in relapsing inflammation of intestine with incompletely elucidated etiology, whose two representative forms are ulcerative colitis (UC) and Crohn’s disease (CD). Accumulating researches have revealed that the individual genetic susceptibility, environmental risk elements, intestinal microbial flora, as well as innate and adaptive immune system are implicated in the pathogenesis and development of IBD. Despite remarkable progression of IBD therapy has been achieved by chemical drugs and biological therapies such as aminosalicylates, corticosteroids, antibiotics, anti-tumor necrosis factor (TNF)-α, anti-integrin agents, etc., healing outcome still cannot be obtained, along with inevitable side effects. Consequently, a variety of researches have focused on exploring new therapies, and found that natural products (NPs) isolated from herbs or plants may serve as promising therapeutic agents for IBD through antiinflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic effects, which implicates the modulation on nucleotide- binding domain (NOD) like receptor protein (NLRP) 3 inflammasome, gut microbiota, intestinal microvascular endothelial cells, intestinal epithelia, immune system, etc. In the present review, we will summarize the research development of IBD pathogenesis and current mainstream therapy, as well as the therapeutic potential and intrinsic mechanisms of NPs in IBD.

Phytochemicals and their potential usefulness in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract with unclear etiology, namely ulcerative colitis and Crohn's disease. Various drug therapies including aminosalicylates and immunomodulators have been approved for use; they have shown to produce diverse side effects. To overcome these limitations of the current therapeutics for IBD, extensive research is underway to identify drugs that are effective and free of undesirable side effects. Recently, various naturally occurring phytochemicals that cover a wide range of chemical entities such as polyphenols, terpeniods, flavonoids, and alkaloids have received attention as alternative candidates for IBD therapy. These phytochemicals act by modulating the immune response, various transcription factors, or reduce cytokine secretion. This review summarizes the findings of recent studies on phytochemicals as therapeutic agents in the management of IBD.

Hydrogen sulfide: an endogenous mediator of resolution of inflammation and injury

SIGNIFICANCE

Hydrogen sulfide is emerging as an important mediator of many aspects of inflammation, and perhaps most importantly as a factor promoting the resolution of inflammation and repair of injury.

RECENT ADVANCES

In the gastrointestinal tract, H(2)S has been shown to promote healing of ulcers and the resolution of mucosal inflammation. On the other hand, suppression of endogenous H(2)S synthesis impairs mucosal defense and leads to increased granulocyte infiltration. H(2)S has been exploited in the design of more effective and safe anti-inflammatory drugs.

CRITICAL ISSUES

Enteric bacteria can be a significant source of H(2)S, which could affect mucosal integrity; indeed, luminal H(2)S can serve as an alternative to oxygen as a metabolic substrate for mitochondrial respiration in epithelial cells. Enterocytes and colonocytes thereby represent a "metabolic barrier" to the diffusion of bacteria-derived H(2)S into the subepithelial space. A compromise of this barrier could result in modulation of mucosal function and integrity by bacterial H(2)S.

FUTURE DIRECTIONS

Improvements in methods for measurement of H(2)S and development of more selective inhibitors are crucial for gaining a better understanding of the pathophysiological importance of this mediator. Results from animal studies suggest that H(2)S-releasing agents are promising therapeutic agents for many indications, but these compounds need to be assessed in a clinical setting.

Mitochondria-dependent apoptosis of activated T lymphocytes induced by astin C, a plant cyclopeptide, for preventing murine experimental colitis

Facilitating T-cell apoptosis is implicated as an effective therapeutic strategy for treatment of T cell-mediated disease, including inflammatory bowel disease. Here, we report that astin C, a plant cyclopeptide isolated from the roots of Aster tataricus (Compositae), induced apoptosis of activated T cells in a mitochondria-dependent but Fas-independent manner in that such activity was still observed in T cells from Fas-mutated MRLlpr/lpr mice. Although caspase 8 was not activated, astin C treatment led to the cleavage of caspase 9 and caspase 3, the upregulation of Bad protein expression as well as release of cytochrome c in activated T cells. Astin C did not induce the expression of GRP78 and GADD153, excluding involvement of endoplasmic reticulum stress-mediated pathway. Moreover, oral administration of astin C protected mice against TNBS-induced colonic inflammation, as assessed by a reduced colonic weight/length ratio and histological scoring. Administering astin C significantly decreased serum levels of TNF-α, IL-4 and IL-17, accompanied with the induction of apoptosis in activated T cells in vivo. The results demonstrate, for the first time, the ability of astin C to induce apoptosis in activated T cells and its potential use in the treatment of colonic inflammation.

Endogenous and exogenous hydrogen sulfide promotes resolution of colitis in rats

BACKGROUND & AIMS

Hydrogen sulfide (H(2)S) is an endogenous gaseous mediator of mucosal defense with antiinflammatory effects that promote ulcer healing. The effects of H(2)S during the pathogenesis of colitis have not been established. We analyzed the contribution of H(2)S to inflammation and ulceration of the colon in a rat model of colitis.

METHODS

Colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid. The ability of the colon to synthesize H(2)S was studied over the course of the resolution of the colitis. Expression of 2 enzymes involved in the synthesis of H(2)S and the effects of inhibitors of these enzymes were examined. We also examined the effects of H(2)S donors on the resolution of colitis.

RESULTS

The capacity for the colon to produce H(2)S increased markedly over the first days after induction of colitis and then declined toward control levels as the colitis was resolved. Inhibition of colonic H(2)S synthesis markedly exacerbated the colitis, resulting in significant mortality. Inhibition of H(2)S synthesis in healthy rats resulted in inflammation and mucosal injury in the small intestine and colon along with down-regulation of cyclooxygenase-2 messenger RNA expression and prostaglandin synthesis. Intracolonic administration of H(2)S donors significantly reduced the severity of colitis and reduced colonic expression of messenger RNA for the proinflammatory cytokine tumor necrosis factor alpha.

CONCLUSIONS

In rats, H(2)S modulates physiological inflammation and contributes to the resolution of colitis.

Nitric oxide as a target of complementary and alternative medicines to prevent and treat inflammation and cancer

Nitric oxide (NO) and associated reactive nitrogen species (RNS) are involved in many physiological functions. There has been an ongoing debate to whether RNS can inhibit or perpetuate chronic inflammation and associated carcinogenesis. Although the final outcome depends on the genetic make-up of its target, the surrounding microenvironment, the activity and localization of nitric oxide synthase (NOS) isoforms, and overall levels of NO/RNS, evidence is accumulating that in general, RNS drive inflammation and cancers associated with inflammation. To this end, many complementary and alternative medicines (CAMs) that work in chemoprevention associated with chronic inflammation, are inhibitors of excessive NO observed in inflammatory conditions. Here, we review recent literature outlining a role of NO/RNS in chronic inflammation and cancer, and point toward NO as one of several targets for the success of CAMs in treating chronic inflammation and cancer associated with this inflammation.