Objective. Free radical-mediated reactions have been implicated as contributors in a number of autoimmune diseases, including systemic lupus erythematosus (SLE). However, the potential for oxidative/ nitrosative stress to elicit an autoimmune response or to contribute to disease pathogenesis, and thus be useful when determining a prognosis, remains largely unexplored in humans. This study was undertaken to investigate the status and contribution of oxidative/ nitrosative stress in patients with SLE.Methods. Sera from 72 SLE patients with varying levels of disease activity according to the SLE Disease Activity Index (SLEDAI) and 36 age-and sex-matched healthy controls were evaluated for serum levels of oxidative/nitrosative stress markers, including antibodies to malondialdehyde (anti-MDA) protein adducts and to 4-hydroxynonenal (anti-HNE) protein adducts, MDA/HNE protein adducts, superoxide dismutase (SOD), nitrotyrosine (NT), and inducible nitric oxide synthase (iNOS).Results. Serum analysis showed significantly higher levels of both anti-MDA/anti-HNE protein adduct antibodies and MDA/HNE protein adducts in SLE patients compared with healthy controls. Interestingly, not only was there an increased number of subjects positive for anti-MDA or anti-HNE antibodies, but also the levels of both of these antibodies were statistically significantly higher among SLE patients whose SLEDAI scores were >6 as compared with SLE patients with lower SLEDAI scores (SLEDAI score <6). In addition, a significant correlation was observed between the levels of anti-MDA or anti-HNE antibodies and the SLEDAI score (r ‫؍‬ 0.734 and r ‫؍‬ 0.647, respectively), suggesting a possible causal relationship between these antibodies and SLE. Furthermore, sera from SLE patients had lower levels of SOD and higher levels of iNOS and NT compared with healthy control sera.Conclusion. These findings support an association between oxidative/nitrosative stress and SLE. The stronger response observed in serum samples from patients with higher SLEDAI scores suggests that markers of oxidative/nitrosative stress may be useful in evaluating the progression of SLE and in elucidating the mechanisms of disease pathogenesis.

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Reactive oxygen and nitrogen species (RONS) are implicated in the pathogenesis of several autoimmune diseases. Also, increased lipid peroxidation and protein nitration are reported in systemic autoimmune diseases. Lipid peroxidation-derived aldehydes (LPDAs) such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) are highly reactive and bind proteins covalently, but their potential to elicit an autoimmune response and contribution to disease pathogenesis remain unclear. Similarly, nitration of protein could also contribute to disease pathogenesis. To assess the status of lipid peroxidation and/or RONS, autoimmune-prone female MRL +/+ mice (5-week old) were treated with trichloroethene (TCE), an environmental contaminant known to induce autoimmune response, for 48 weeks (0.5 mg/ml via drinking water), and formation of antibodies to LPDA-protein adducts was followed in the sera of control and TCE-treated mice. TCE treatment led to greater formation of both anti-MDA-and and-HNE-protein adduct antibodies and higher serum iNOS and nitrotyrosine levels. The increase in TCE-induced oxidative stress was associated with increases in anti-nuclear-, anti-ssDNA-and anti-dsDNA-antibodies. These findings suggest that TCE exposure not only leads to oxidative/nitrosative stress, but is also associated with induction/exacerbation of autoimmune response in MRL +/+ mice. Further interventional studies are needed to establish a causal role of RONS in TCE-mediated autoimmunity.

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