A comparison of glutathione reductase and glutathione peroxidase activities in patients with rheumatoid arthritis and healthy adults

The interrelation of glutathione reductase, catalase, glutathione peroxidase, superoxide dismutase, and glucose-6-phosphate in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common form of inflammatory arthritis, a systemic autoimmune disease characterized by chronic inflammation of the synovial joints, ultimately leading to joint destruction and permanent disability, affecting 1% of the world population. Oxidative stress in rheumatoid inflammation, due to the fact that antioxidant systems are impaired in RA and caused by fee radicals, might have an essential role in etiology of RA. This review includes the interrelation of antioxidants against free radicals in RA patients. There is much evidence that antioxidant team that covers glutathione reductase, catalase, glutathione peroxidase, superoxide dismutase, and glucose-6-phopshate destroy reactive oxygen species and other free radicals through enzymatic as well as nonenzymatic means. The change in relative levels of antioxidants vis-à-vis free radical formation and level could be used as indicators for effective and earlier diagnosis of RA.

Lipid peroxidation and antioxidant status in blood of rheumatoid arthritis patients

The main objective of the study was to assess the oxidative stress in plasma and erythrocytes of rheumatoid arthritis patients by measuring the levels of thiobarbituric acid reactive substances (TBARS), non-enzymatic antioxidants (vitamin E, C and reduced glutathione) and enzymatic antioxidants [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx)]. This study has been conducted on twenty-two adult female rheumatoid arthritis patients and an equal number of healthy subjects. Elevated lipid peroxidation and multidirectional changes in the antioxidant defence system were noticed in patients with rheumatoid arthritis. The enhanced lipid peroxidation accompanied by disturbance in antioxidant status indicates that rheumatoid arthritis patients are more prone to free radical mediated oxidative damage.

Glutathione reductase activity, riboflavin status, and disease activity in rheumatoid arthritis

OBJECTIVE

To measure erythrocyte glutathione reductase (EGR) activity and riboflavin status, and their relations to disease activity, in rheumatoid arthritis patients compared to healthy controls.

METHODS

Patients with rheumatoid arthritis were classified as active if there were features of articular inflammation which required initiation or change of disease modifying therapy, and as inactive if they had little evidence of articular inflammation. EGR was measured in patients and healthy controls by a functional assay with or without the addition of flavin adenine dinucleotide (FAD). The ratio of stimulated EGR (with FAD added) to basal EGR (no added FAD), which measures riboflavin status, is known as the EGR activation coefficient (EGRAC). An EGRAC > or = 1.3 represents biochemical riboflavin deficiency.

RESULTS

91 patients with rheumatoid arthritis, including 57 with active disease, and 220 healthy controls were studied. Both basal and stimulated EGR were significantly higher in patients with rheumatoid arthritis (P = 0.0001) than in controls. Biochemical riboflavin deficiency was identified in 41% controls and 33% patients with active rheumatoid arthritis but was significantly less frequent (9%) in patients with inactive compared to active disease (P = 0.02) or healthy controls (P = 0.0006). Pain score, articular index, C reactive protein, and erythrocyte sedimentation rate were increased in patients with riboflavin deficiency (all P < 0.02).

CONCLUSIONS

Higher basal and stimulated EGR might be expected in patients with rheumatoid arthritis in response to chronic oxidative stress due to synovial inflammation. The association of riboflavin deficiency with increased disease activity suggests that impaired EGR activity could facilitate continuing inflammation in these patients.

Glutathione redox cycle enzymes and selenium in severe rheumatoid arthritis: lack of antioxidative response to selenium supplementation in polymorphonuclear leucocytes

The antioxidant capacity of the glutathione redox cycle and the concentrations of selenium in serum, red blood cells or whole blood, and polymorphonuclear leucocytes was evaluated in nine patients with severe rheumatoid arthritis (RA) and eight healthy controls receiving daily supplementation with 250 micrograms selenomethionine for six months. Serum and whole blood concentrations of selenium and the activity of the selenium dependent enzyme glutathione peroxidase (GSH-Px) were low in the serum, red blood cells, and polymorphonuclear leucocytes of patients with RA before selenium supplementation. During supplementation serum and whole blood concentrations of selenium and the activity of GSH-Px in serum and red blood cells of patients with RA and serum GSH-Px in controls increased. Selenium and GSH-Px in polymorphonuclear leucocytes were unaffected in patients with RA in contrast with the controls where both were augmented. Glutathione reductase activity in the red blood cells and polymorphonuclear leucocytes of patients with RA was low but increased during selenium supplementation. Whole blood concentrations of glutathione were slightly lower in patients with RA than controls and no difference in the content in polymorphonuclear leucocytes was found between the groups. The activity in red blood cells of glucose-6-phosphate dehydrogenase was high in patients with RA, indicating sufficient function of the hexose monophosphate pathway. The reduced antioxidant activity of the glutathione redox cycle in patients with severe RA was mainly due to the low availability of selenium. This was further supported by the response to selenium supplementation in serum and red blood cells. In the polymorphonuclear leucocytes, however, no biochemical effects of selenium supplementation were seen. This lack of antioxidative response could play a pathogenetic part in inflammation in patients with RA.

Role of Glutathione Peroxidase in Rheumatoid Arthritis: Analysis of Enzyme Activity and DNA Polymorphism

Aberrant expression of the antioxidant enzyme glutathione peroxidase (GPx) could contribute to the etiology of rheumatoid arthritis (RA). However, previous enzyme activity studies examining this relationship were inconclusive. Indirect evidence for this relationship derives from the known efficacy of gold therapy in RA, since gold compounds specifically inhibit GPx. The hypothesis that variants of GPx are associated with RA was examined by two approaches: enzyme activity analysis and restriction fragment length polymorphism (RFLP) association analysis. No significant difference was found in whole blood GPx activity between 28 RA patients and 36 controls. GPx activity appeared to be independent of sex, race, or type of drug treatment. However, a statistically significant difference was found with respect to treatment responsiveness. RA patients classified as good responders to gold therapy, but who were no longer taking gold, had a significantly higher GPx activity compared to both the controls and good responders currently on gold therapy. Aberrantly high GPx activity could contribute to RA by generating excess oxidized glutathione, a potent collagenase activator. Gold therapy would reduce GPx activity to normal levels. The restriction enzyme Pvu II in conjunction with a GPx gene probe identified a useful RFLP (Al, 22 kbp; A2, 15 kbp) with allelic frequencies of A1 and A2 equal to 0.11 and 0.89, respectively, in the control population. No statistically significant association, however, could be demonstrated between this allelic variant of the GPx gene and RA.

Selenium in rheumatic diseases

Selenium is involved in several important biochemical pathways relevant to rheumatic diseases. Experimental and clinical studies suggest that selenium modulates the inflammatory and immune responses. Patients suffering from inflammatory rheumatic diseases often have low selenium levels, but this finding does not correlate with disease severity. Selenium supplementation needs stricter selection criteria and better ascertainment of dose to obtain a stimulatory or inhibitory effect relevant to the disease state. Prevention of marginal selenium deficiency by moderate supplementation might enhance host defense mechanisms.