Manuel Sandoval

Role of inducible nitric oxide synthase expression and peroxynitrite formation in guinea pig ileitis

BACKGROUND & AIMS Inflammatory bowel disease is characterized by increased synthesis of nitric oxide. The aim of this study was to determine if inducible NO synthase (iNOS) was responsible for tissue injury, potentially via peroxynitrite formation, in the guinea pig model of gut inflammation. METHODS Inflammation was induced in guinea pig ileum by intraluminal administration of the hapten trinitrobenzene sulfonic acid in 50% ethanol. iNOS gene expression was assessed by reverse-transcriptase polymerase chain reaction and Western blotting, immunohistochemistry was determined by its localization, and activity was inhibited with the specific inhibitor aminoguanidine administered via the drinking water for 7 days. Nitration of tyrosines was assessed by immunohistochemistry. RESULTS In control animals, iNOS gene expression was minimal to absent, whereas, in hapten, inflammation-marked iNOS gene expression was evident from day 1 to 7. Nitrotyrosine and iNOS immunohistochemistry were colocalized, and positive staining was most intense in epithelia and neurons. Inhibition of NO formation prevented nitrotyrosine formation. Aminoguanidine inhibited the inflammatory response and restored morphology. CONCLUSIONS The colocalization of tyrosine nitration with iNOS immunoreactivity suggests that iNOS may be responsible for tissue injury and the formation of NO-dependent nitrating species, potentially peroxynitrite. Inhibition of iNOS may afford a new therapeutic approach to the treatment of inflammatory bowel disease.

Role of Metallothionein and Cysteine-Rich Intestinal Protein in the Regulation of Zinc Absorption by Diabetic Rats

ABSTRACT: Hyperzincuria and low Zn absorption in diabetic animals and humans have prompted speculation that diabetics are more susceptible to Zn deficiency. There is little information, however, describing the effects of diabetes on the biochemical mechanisms of intestinal Zn transport. We evaluated Zn absorption in streptozotocin-induced diabetic rats based on a model of Zn transport in which cysteine-rich intestinal protein serves as an intracellular carrier that is inhibited by metallothionein (MT). Apparent absorption and retention of Zn and Cu in rats fed a purified diet were measured in a balance study 15–17 d after induction of diabetes. The rate of 65Zn absorption from isolated intestinal segments, molecular distribution of 65Zn in mucosal cytosol, and tissue MT levels were measured on d 20–22. Food consumption, and thus Zn and Cu intake, by diabetic rats was twice that of controls. Although fractional absorption (percent) of Zn and Cu was lower in the diabetic rats, net absorption (µg/100 g body weight/d) was higher. The higher net absorption in the diabetic group was offset, however, by higher urinary excretion, so that Zn and Cu retention was similar in both groups of animals. Low fractional absorption is attributable to the down-regulation of intestinal Zn transport, as indicated by the lower rate of 65Zn absorption from isolated intestinal segments in the diabetic rats. Down-regulation of intestinal transport is in turn attributable to higher concentrations of intestinal MT, which resulted in more 65Zn in the mucosal cytosol bound to MT, an inhibitor of Zn transport, and less to cysteine-rich intestinal protein. These observations are similar to those previously described in rats consuming normal amounts of a diet containing excess Zn and are consistent with an antagonistic relationship between cysteinerich intestinal protein and MT in Zn transport. The results suggest that decreased Zn absorption in diabetic rats is not a disease-related defect in Zn transport but instead is a homeostatic response to high Zn intake caused by overconsumption of a diet with a moderate Zn content.

The Anti-Inflammatory Actions of the Herbal Medicine, Cat's Claw, Are Due to a Suppression of NF-κB Activation and Inhibition of Gene Expression

The Anti-Inflammatory Actions of the Herbal Medicine, Cats Claw, Are Due to a Suppression of NF-κB Activation and Inhibition of Gene Expression

Healing of Gastric Ulcers in Rats by the Herbal Medicine, Sangre de Grado: Implications for the Developing World

Healing of Gastric Ulcers in Rats by the Herbal Medicine, Sangre de Grado: Implications for the Developing World

PEROXYNITRITE-INDUCED APOPTOSIS IN HUMAN EPITHELIAL CELLS (T84) IS ATTENUATED BY ASCORBIC ACID OR 5-AMINOSALICYLIC ACID. • 496

PEROXYNITRITE-INDUCED APOPTOSIS IN HUMAN EPITHELIAL CELLS (T84) IS ATTENUATED BY ASCORBIC ACID OR 5-AMINOSALICYLIC ACID. • 496

DIABETIC SERUM INDUCES APOPTOSIS AND THE EXPRESSION OF INDUCIBLE NITRIC OXIDE SYNTHASE IN PC-12 CELLS. 563

DIABETIC SERUM INDUCES APOPTOSIS AND THE EXPRESSION OF INDUCIBLE NITRIC OXIDE SYNTHASE IN PC-12 CELLS. 563

Decreased zinc absorption in guinea pig models of acute and chronic ileitis

Abstract The biochemical defects underlying decreased Zn absorption in inflammatory bowel disease have not been identified. In vitro studies have suggested that reactive oxygen species (e.g., hypochlorous acid and superoxide), produced by phagocytic cells during the inflammatory response, mobilize Zn from metallothionein (MT) and other proteins that bind Zn via sulfhydryl groups. We avaluated the in vivo effects of intestinal inflammation on Zn absorption and Zn binding to intestinal MT and cysteine-rich intestinal protein (CRIP), possible components of a carrier-mediated intestinal Zn transport system. Guinea pig models of acute (NaOCl luminal perfusion) and chronic (2,4,6-trinitrobenzene sulfonic acid [TNBS] injection) ileitis were used. The rate of 65 Zn absorption from the isolated ileum and the molecular distribution of 65 Zn in mucosal cytosol determined by size-exclusion HPLC were measured after 1 hr of perfusion in the acute model and after 7 days in the chronic model. Zinc absorption was significantly lower in guinea pigs with either chronic or acute inflammation. In both models, decreased binding of 65 Zn to MT and CRIP was also observed. The results indicate that decreased Zn absorption during intestinal inflammation may be mediated by the effects of oxidants on the transport activity of intestinal proteins that bind Zn via sulfhydryl groups.