Synoviolin promotes IRE1 ubiquitination and degradation in synovial fibroblasts from mice with collagen-induced arthritis.

The E3 ubiquitin ligase synoviolin (SYVN1) functions as an anti-apoptotic factor that is responsible for the outgrowth of synovial cells during the development of rheumatoid arthritis. The molecular mechanisms underlying SYVN1 regulation of cell death are largely unknown. Here, we report that elevated SYVN1 expression correlates with decreased levels of the protein inositol-requiring enzyme 1 (IRE1)-a pro-apoptotic factor in the endoplasmic reticulum (ER)-stress-induced apoptosis pathway-in synovial fibroblasts from mice with collagen-induced arthritis (CIA). SYVN1 interacts with and catalyses IRE1 ubiquitination and consequently promotes IRE1 degradation. Suppression of SYVN1 expression in synovial fibroblasts from CIA mice restores IRE1 protein expression and reverses the resistance of ER-stress-induced apoptosis of CIA synovial fibroblasts. These results show that SYVN1 causes the overgrowth of synovial cells by degrading IRE1, and therefore antagonizes ER-stress-induced cell death.

Effect of vitamin B6 on oxygen radicals, mitochondrial membrane potential, and lipid peroxidation in H2O2-treated U937 monocytes.

Vitamin B6 (Vit.B6) supplementation has been shown to be beneficial in reducing diabetic complications, cognitive aging, and in the prevention of coronary heart disease. It was hypothesized that Vit.B6 compounds may function as antioxidants and thus offer protection against oxidative stress under various pathophysiological and or experimental conditions. To test this hypothesis, U937 monocytes were cultured with pyridoxine (P), pyridoxal phosphate (PP) and pyridoxamine (PM) and H2O2, either alone or together for 2 h. Oxidative stress was determined by measuring superoxide radical production, lipid peroxidation, and mitochondrial transmembrane potential. Results demonstrate that Vit.B6 compounds can prevent the oxygen radical generation and lipid peroxidation caused by hydrogen peroxide in U937 monocytes, and that some of the protective effect of Vit.B6 may occur via modification of mitochondrial function.

Oxygen radical generation and endosulfan toxicity in Jurkat T-cells.

The mechanism by which endosulfan exposure causes cellular dysfunction in experimental animals and humans is not clear. In the present study, we provide experimental evidence in support of the role of oxidative stress in endosulfan toxicity. Using both cell free system and Jurkat cells as in vitro models, we demonstrate that endosulfan can generate oxygen radicals that is inhibitable by superoxide dismutase (SOD) and glutathione (GSH). In the cell culture model, oxygen radical generation in response to endosulfan was dose- (0-100 microM) and time-dependent (0-12 h). Two-color flowcytometric analysis showed that endosulfan mediated changes in delta psi(m) and generation of superoxide radicals do occur simultaneously in the affected cell population. It was hypothesized that endosulfan exerts a severe oxidative stress in Jurkat cells and this could be prevented or minimized by an antioxidant. To test this hypothesis, GSH was added exogenously and endosulfan toxicity was evaluated by alamarblue assay. In conclusion, our results demonstrate a role for reactive oxygen species (ROS) in endosulfan toxicity and that supplementation of antioxidants such as GSH may be useful in individuals who are at risk to endosulfan toxicity.