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Simplified diagram of mucosal glutathione synthesis in the ileum

Subsequent analyses showed no defect in expression of glutathione synthesis genes.

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The above colitis improved by 1 week of glutathione ..

The majority of H2S production in mammalian tissue is enzymatically regulated, with the pyridoxal-5′-phosphate (P5P)-dependent enzymes cystathionine-beta-synthase (CBS) and cystathionine-gamma-lyase (CSE) being the most extensively studied . During a bout of hapten-induced colitis in rats, the capacity of colonic tissue to produce H2S is substantially increased, in parallel with the degree of mucosal inflammation . The H2S produced in this setting exerts significant beneficial effects in terms of reducing inflammation and enhancing healing of the ulcerated tissue . Based on pharmacological studies (i.e., using inhibitors of CBS and CSE), CBS appeared to account for the majority of the observed increase in colonic H2S synthesis during colitis . However, administration of inhibitors of both CBS and CSE did not completely abolish colonic H2S production, raising the possibility that there may be other sources of H2S synthesis in the colon . We previously reported that enteric bacteria did not account for a significant portion of what we have measured as colonic tissue H2S synthesis .

Comparative efficacies of 2 cysteine prodrugs and a glutathione delivery agent in a colitis ..

H2S is produced throughout the GI tract , and contributes to many digestive functions , including epithelial secretion –, smooth muscle contraction , and mucosal defense , –, . H2S also promotes resolution of inflammation and repair of injury in the gastrointestinal tract and elsewhere , , , , . In the present study we have demonstrated that colonic H2S synthesis does not occur solely through P5P-dependent pathways (CSE and CBS). Rather, a P5P-independent, α-KG-dependent pathway via the enzymes CAT and 3MST is the major source of H2S synthesis in both the healthy and inflamed colon. We also demonstrated that in colitis the ulcerated mucosa is the major site of both P5P-dependent and α-KG-dependent H2S synthesis and that this synthesis is not influenced by the extent of granulocyte infiltration into the tissue. Furthermore, inactivation of H2S occurs rapidly in colonic tissue (in the mucosa much more quickly than in muscle), but at a significantly lower rate in ulcerated colonic tissue than in tissue immediately adjacent to ulcers or in healthy colonic tissue. Moreover, increased expression of H2S-producing enzymes and decreased expression of the key H2S inactivating enzyme (SQR) were observed specifically at sites of mucosal ulceration, but not in mucosa immediately adjacent to ulcers or in the healthy mucosa. One explanation for the decrease in expression of SQR at sites of ulceration is that it is just a consequence of the tissue destruction at those sites. However, at these same sites we observed significant up-regulation of 3MST, which like SQR, is primarily localized to mitochondria.

that catalyzes the first reaction in the synthesis of glutathione

Keywords:Crohn's disease; ulcerative colitis; glutathione; amino acids; γ-glutamylcysteine synthetase; mucosa

Colitis was induced in conventionally housed rats using dinitrobenzene sulfonic acid (DNBS) , a modified version of the original trinitrobenzene sulfonic acid model of colitis . Rats were given 30 mg DNBS intracolonically in 0.5 mL of 50% ethanol. Groups of rats (n≥4) were euthanized 6 h to 28 days after DNBS administration for determination of H2S synthesis. Colonic inflammation was assessed by the measurement of myeloperoxidase (MPO) activity, using a method modified from that described by Bradley et al. . MPO is an enzyme found primarily in the azurophilic granules of neutrophils, and has been used extensively as a quantitative index of granulocyte infiltration.

A pilot time-course study demonstrated that the greatest granulocyte infiltration of the colon occurred at 3 days after DNBS administration (MPO activity in DNBS-treated rats averaged 22.2±4.3 U/mg, versus 4.6±0.5 U/mg in healthy controls; p2S synthesis was significantly elevated in samples from rats with colitis, both through the P5P-dependent pathways and the CAT/3MST pathway (). As in the case for colonic tissue from healthy rats, there was substantially greater H2S synthesis from the CAT/3MST pathway in tissue from rats with colitis than there was from the P5P-dependent pathways. The two inhibitors of CAT (CHH and L-aspartate) each substantially reduced α-KG-dependent H2S synthesis by inflamed colonic tissue ().

for the intestinal synthesis of glutathione

Glutamine is one of the three amino acids involved in glutathione synthesis

In summary, the CAT-3MST enzymes represent the primary pathway for H2S synthesis in the healthy and inflamed colon. Marked increases in colonic H2S synthesis, via both P5P-dependent and α-KG-dependent pathways, occur specifically at sites of ulceration. The signals responsible to triggering this up-regulation of H2S synthesis are not yet clear. A marked reduction in tissue inactivation of H2S also occurs selectively at sites of ulceration. The resulting higher local levels of H2S in the microenvironment of the ulcer would act to promote rapid restoration of epithelial barrier integrity. These findings may have important implications with respect to improving treatments for chronic ulcerative conditions of the gastrointestinal tract, including Crohn's disease and ulcerative colitis.

Our observation that most of the H2S produced by colonic tissue is derived via a α-KG-dependent pathway was surprising. Previous studies have focused on the enzymes CSE and CBS as significant sources of H2S synthesis both in healthy and inflamed colonic tissue , , . We previously reported that CBS was the major enzymatic source of colonic H2S, but this was based largely on our observation that CHH, an inhibitor of CBS, caused a dramatic exacerbation of colitis in rats, that was more profound than was seen with inhibitors of CSE . However, in the present study, using CSE−/− and CBS+/− mice, we found that CSE was the major source of P5P-dependent H2S synthesis in the healthy colon. Moreover, while CHH has been widely used as an inhibitor of CBS and has been shown to suppress P5P-dependent H2S synthesis , , , it also inhibits aminotransferases , , and therefore can block the synthesis of H2S that occurs via the CAT-3MST pathway. This was confirmed in the present study. A recent study by Asimakopoulou et al. tested the selectivity of several commonly used putative inhibitors of H2S-producing enzymes and concluded that no selective inhibitors of CBS are currently available.

the synthesis of glutathione, ..
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GSH, glutathione; GSSG, glutathione disulphide; Gly ..

Hydrogen sulfide (H2S) is produced throughout the gastrointestinal tract, and it contributes to maintenance of mucosal integrity, resolution of inflammation, and repair of damaged tissue. H2S synthesis is elevated in inflamed and damaged colonic tissue, but the enzymatic sources of that synthesis are not completely understood. In the present study, the contributions of three enzymatic pathways to colonic H2S synthesis were determined, with tissues taken from healthy rats and rats with colitis. The ability of the colonic tissue to inactivate H2S was also determined. Colonic tissue from rats with hapten-induced colitis produced significantly more H2S than tissue from healthy controls. The largest source of the H2S synthesis was the pathway involving cysteine amino transferase and 3-mercaptopyruvate sulfurtransferase (an α-ketoglutarate-dependent pathway). Elevated H2S synthesis occurred specifically at sites of mucosal ulceration, and was not related to the extent of granulocyte infiltration into the tissue. Inactivation of H2S by colonic tissue occurred rapidly, and was significantly reduced at sites of mucosal ulceration. This correlated with a marked decrease in the expression of sulfide quinone reductase in these regions. Together, the increased production and decreased inactivation of H2S at sites of mucosal ulceration would result in higher H2S levels at these sites, which promotes of resolution of inflammation and repair of damaged tissue.

Glutathione synthesis and its role in redox signaling.

H2S synthesis via CAT-3MST from the mucosa and muscularis layers of the colonic tissue from healthy rats was comparable (), as was the case for H2S synthesis via P5P-dependent pathways (). However, the mucosa from sites of ulceration produced significantly more H2S via the CAT-3MST pathway () and the P5P-dependent pathways (). H2S synthesis from samples of the muscularis layer were relatively low, though a significant increase in synthesis via the P5P-dependent pathways was observed when the tissue was from a region underling a site of ulceration (). H2S synthesis from mucosal or muscularis samples from rats with colitis, but taken from sites that were not ulcerated, was similar to that from samples taken from healthy controls. However, the elevated synthesis of H2S from tissues taken from sites of ulceration did not appear to be related to inflammation (e.g., granulocyte infiltration) at those sites. MPO activity, a marker of granulocyte infiltration, was comparable in samples of mucosa from sites of ulceration versus non-ulcerated sites (21.5±0.5 U/mg versus 17.8±2.0 U/mg, respectively; ns), but significantly elevated versus healthy controls (5.1±0.5 U/mg; p

Glutathione Side Effects: Precautions To Keep In Mind …

Steinbach Online, November 2017
Due to recent research, curcumin has been nicknamed the "master off-switch for inflammation." It has been shown to help relieve pain and inflammation by modulating the inflammatory pathways that affect heart, joints, liver, gastrointestinal tract, brain, cellular health and the immune system! This makes curcumin useful for relieving the pain in osteoarthritis, rheumatoid arthritis and bursitis as well as in digestive conditions such as ulcerative colitis, Crohn's disease, celiac disease, gastritis and gastric ulcers. Curcumin has the ability to block more than 30 different inflammation pathways! Curcumin also protects against inflammatory calcium loss from our bones and has been shown to slow prostate cell proliferation in addition to supporting healthy cholesterol and blood pressure levels. Curcumin has liver-protective effects and is a powerful liver detoxifier. It helps to prevent the build-up of toxins, enhance glutathione levels, supports bile production and solubility as well as improve digestive function. Curcumin may help reverse certain forms of liver cirrhosis to some degree, and is thought to be especially helpful for people who regularly drink alcohol or use common painkillers, both of which damage cause liver damage. Studies suggest that curcumin can also reduce the severity of liver injury induced by iron overdose, cholestasis and carbon tetrachloride intoxication. In addition to supporting the liver processes, managing inflammation is also vital in aiding detoxification. Inflammation control is needed because the detoxification process involves the release of toxic metabolites from our cells and tissues in order to expel them from the body. On the way to being eliminated, these toxins can trigger inflammatory reactions and cause tissue damage. Curcumin, was originally researched for Alzheimer's disease because studies found there is a much lower incidence and prevalence of Alzheimer's in India than in North America. The association between curry consumption and cognitive level in certain populations were researched and it was found that those who ate curry foods performed better on a standard test than those who never or rarely ate curry! Alzheimer's disease degrades the nerve cells in the brain through inflammation in glial cells, the formation of beta-amyloid plaques, metal toxicity, and oxidative damage. Curcumin acts as a powerful anti-inflammatory and antioxidant in the brain. It can also break down plaques and has the potential to guard against their development, plus it supports healthy neurotransmitter function, improving memory and helping to prevent cognitive decline.

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