Role of cyclooxygenase enzymes in a murine model of experimental cholera

Effects of exercise training on the glutathione antioxidant system

Purpose

The glutathione (GSH) antioxidant system has been shown to play an important role in the maintenance of good health and disease prevention. Various approaches have been used to enhance GSH availability including diet, nutritional supplementation, and drug administration, with minor to moderate success. Exercise training has evolved as a new approach. The purpose of this study was to investigate the effects of aerobic exercise training (AET), circuit weight training (CWT), and combined training (AET + CWT) on general adaptations, and resistance to acutely induced oxidative stress, as assessed by changes in the GSH antioxidant system.

Methods

Eighty healthy sedentary volunteers participated in the study who were randomly assigned to four groups: control (no exercise); AET, CWT, and AET + CWT. Exercise training programs were designed to simulate outpatient cardiac rehabilitation (40 min × 3 days × 6 weeks). Venous blood sampling was taken at rest and post maximal graded exercise test (GXT). A new improved spectrophotometric venous assay analysis technique was used. A mixed model repeated measures analysis of variance design was used with t-tests for preplanned comparisons evaluated at Bonferroni-adjusted α levels.

Results

Effectiveness of the exercise training programs was demonstrated by significant between-group (exercise group versus control) comparisons. AET, CWT, and AET + CWT showed significant pretraining-posttraining increases in resting GSH and glutathione-glutathione disulfide ratio (GSH:GSSG), and significant decreases in GSSG levels ( P <0.005). AET + CWT showed the most pronounced effect compared with AET or CWT alone ( P <0.025).

Conclusion

This study represents the first longitudinal investigation involving the effects of multiple modes of exercise training on the GSH antioxidant system with evidence, suggesting the GHS:GSSG ratio as the most sensitive change marker. The significant findings of this study have potential clinical implications to individuals involved in cardiac and pulmonary rehabilitation. Eur J Cardiovasc Prev Rehabil 14:630-637 © 2007 The European Society of Cardiology

Induction of cyclooxygenase-2 signaling by Stomatococcus mucilaginosus highlights the pathogenic potential of an oral commensal

Stomatococcus mucilaginosus is an oral commensal that has been occasionally reported to cause severe infections in immunocompromised patients. There is no information about the pathogenic role of S. mucilaginosus in airway infections. In a cohort of 182 subjects with bronchiectasis, we found that 9% were colonized with S. mucilaginosus in their lower airways by culture growth from bronchoalveolar lavage. To address the pathogenic potential of S.mucilaginosus, we developed a murine model of S. mucilaginosus lung infection. Intratracheal injection of S. mucilaginosus in C57BL/6 mice resulted in a neutrophilic influx with production of proinflammatory cytokines, chemokines, and lipid mediators, mainly PGE₂ with induction of cyclooxygenase-2 (COX-2) in the lungs. Presence of TLR2 was necessary for induction of COX-2 and production of PGE₂ by S. mucilaginosus. TLR2-deficient mice showed an enhanced clearance of S. mucilaginosus compared with wild-type mice. Administration of PGE₂ to TLR2(-/-) mice resulted in impaired clearance of S. mucilaginosus, suggesting a key role for COX-2-induced PGE₂ production in immune response to S. mucilaginosus. Mechanistically, induction of COX-2 in macrophages was dependent on the p38-ERK/MAPK signaling pathway. Furthermore, mice treated with S. mucilaginosus and Pseudomonas aeruginosa showed an increased mortality compared with mice treated with PA103 or S. mucilaginosus alone. Inhibition of COX-2 significantly improved survival in mice infected with PA103 and S. mucilaginosus. These data provide novel insights into the bacteriology and personalized microbiome in patients with bronchiectasis and suggest a pathogenic role for S. mucilaginosus in patients with bronchiectasis.

Toxin mediated diarrhea in the 21 century: the pathophysiology of intestinal ion transport in the course of ETEC, V. cholerae and rotavirus infection

An estimated 4 billion episodes of diarrhea occur each year. As a result, 2–3 million children and 0.5–1 million adults succumb to the consequences of this major healthcare concern. The majority of these deaths can be attributed to toxin mediated diarrhea by infectious agents, such as E. coli, V. cholerae or Rotavirus. Our understanding of the pathophysiological processes underlying these infectious diseases has notably improved over the last years. This review will focus on the cellular mechanism of action of the most common enterotoxins and the latest specific therapeutic approaches that have been developed to contain their lethal effects.

Bacterial clearance ofPseudomonas aeruginosa is enhanced by the inhibition of COX-2

Prostanoids generated by COX-2 are involved in the regulation of inflammation but their exact role in the innate immune response has not been defined. We investigated whether COX-2 is involved in host defense against Pseudomonas aeruginosa pneumonia. In vitro studies, in a macrophage cell line, showed that cytotoxic strain of P aeruginosa (PA103) induced significant COX-2 protein expression and enzymatic function. In vivo data showed that infection with PA103 increased COX-2 protein production in whole lung tissue compared to mice that were infected with mutant bacteria that lack ExoU (DeltaU) or ExoU and ExoT (DeltaUT). COX-2(-/-) mice had accentuated clearance of cytotoxic P. aeruginosa from the lungs. We further tested the effects of COX-2 products such as prostaglandin E(2) on the function of phagocytic cells. Our studies indicate that prostaglandin E(2) may be involved through interacting with the EP2 receptors in modulating the host response because treatment of macrophages with prostaglandin E(2) suppressed production of reactive oxygen species. Furthermore there was enhanced bacterial clearance in EP2 receptor(-/-) mice compared to the wild-type controls. Thus it is possible that inhibition of COX-2 or EP2 receptors could be an effective adjunctive treatment for severe or resistant P. aeruginosa pneumonia.

Insulin-like growth factor I improves intestinal barrier function in cirrhotic rats

BACKGROUND AND AIMS

In liver cirrhosis, disruption of the intestinal barrier facilitates bacterial translocation and spontaneous bacterial peritonitis. Insulin-like growth factor I (IGF-I) is an anabolic hormone synthesised by hepatocytes that displays hepatoprotective activities and trophic effects on the intestine. The aim of this study was to investigate the effect of IGF-I on intestinal barrier function in cirrhotic rats.

METHODS

In rats with carbon tetrachloride induced cirrhosis, we investigated the effect of IGF-I therapy on: (a) portal pressure; (b) intestinal histology and permeability to endotoxin and bacteria; (c) intestinal expression of cyclooxygenase 2 (COX-2) and tumour necrosis factor alpha (TNF-alpha), two factors that influence in a positive and negative manner, respectively, the integrity of the intestinal barrier; (d) intestinal permeability to 3H-mannitol in rats with bile duct ligation (BDL); and (e) transepithelial electrical resistance (TER) of polarised monolayers of rat small intestine epithelial cells.

RESULTS

IGF-I therapy reduced liver collagen expression and portal pressure in cirrhotic rats, induced improvement in intestinal histology, and caused a reduction in bacterial translocation and endotoxaemia. These changes were associated with diminished TNF-alpha expression and elevated COX-2 levels in the intestine. IGF-I reduced intestinal permeability in BDL rats and enhanced barrier function of the monolayers of epithelial intestinal cells where lipopolysaccharide (LPS) caused a decrease in TER that was reversed by IGF-I. This effect of IGF-I was associated with upregulation of COX-2 in LPS treated enterocytes.

CONCLUSIONS

IGF-I enhances intestinal barrier function and reduces endotoxaemia and bacterial translocation in cirrhotic rats. IGF-I therapy might be useful in the prevention of spontaneous bacterial peritonitis in liver cirrhosis.