Involvement of lipid peroxidation-derived aldehyde-protein adducts in autoimmunity mediated by trichloroethene

The frequency of 1,4-benzoquinone-lysine adducts in cytochrome c correlate with defects in apoptosome activation

Electrophile-mediated post-translational modifications (PTMs) are known to cause tissue toxicities and disease progression. These effects are mediated via site-specific modifications and structural disruptions associated with such modifications. 1,4-Benzoquinone (BQ) and its quinone-thioether metabolites are electrophiles that elicit their toxicity via protein arylation and the generation of reactive oxygen species. Site-specific BQ-lysine adducts are found on residues in cytochrome c that are necessary for protein-protein interactions, and these adducts contribute to interferences in its ability to facilitate apoptosome formation. To further characterize the structural and functional impact of these BQ-mediated PTMs, the original mixture of BQ-adducted cytochrome c was fractionated by liquid isoelectric focusing to provide various fractions of BQ-adducted cytochrome c species devoid of the native protein. The fractionation process separates samples based on their isoelectric point (pI), and because BQ adducts form predominantly on lysine residues, increased numbers of BQ adducts on cytochrome c correlate with a lower protein pI. Each fraction was analyzed for structural changes, and each was also assayed for the ability to support apoptosome-mediated activation of caspase-3. Circular dichroism revealed that several of the BQ-adducted cytochrome c species maintained a slightly more rigid structure in comparison to native cytochrome c. BQ-adducted cytochrome c also failed to activate caspase-3, with increasing numbers of BQ-lysine adducts corresponding to a greater inability to activate the apoptosome. In summary, the specific site of the BQ-lysine adducts, and the nature of the adduct, are important determinants of the subsequent structural changes to cytochrome c. In particular, adducts at sites necessary for protein-protein interactions interfere with the proapoptotic function of cytochrome c.

Markers of oxidative and nitrosative stress in systemic lupus erythematosus: correlation with disease activity

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 > or = 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.

Effects of Kombucha on oxidative stress induced nephrotoxicity in rats

BACKGROUND

Trichloroethylene (TCE) may induce oxidative stress which generates free radicals and alters antioxidants or oxygen-free radical scavenging enzymes.

METHODS

Twenty male albino rats were divided into four groups: (1) the control group treated with vehicle, (2) Kombucha (KT)-treated group, (3) TCE-treated group and (4) KT/TCE-treated group. Kidney lipid peroxidation, glutathione content, nitric oxide (NO) and total blood free radical concentrations were evaluated. Serum urea, creatinine level, gamma-glutamyl transferase (GGT) and lactate dehydrogenase (LDH) activities were also measured.

RESULTS

TCE administration increased the malondiahyde (MDA) and NO contents in kidney, urea and creatinine concentrations in serum, total free radical level in blood and GGT and LDH activities in serum, whereas it decreased the glutathione (GSH) level in kidney homogenate. KT administration significantly improved lipid peroxidation and oxidative stress induced by TCE.

CONCLUSION

The present study indicates that Kombucha may repair damage caused by environmental pollutants such as TCE and may be beneficial to patient suffering from renal impairment.

Evidence of autoimmune-related effects of trichloroethylene exposure from studies in mice and humans

OBJECTIVE

Our objective was to examine experimental and epidemiologic studies pertaining to immune-related, and specifically autoimmune-related, effects of trichloroethylene (TCE).

DATA SOURCES AND EXTRACTION

We performed a literature search of PubMed and reviewed bibliographies in identified articles. We then systematically reviewed immune-related data, focusing on clinical and immunologic features and mechanistic studies.

DATA SYNTHESIS

Studies conducted in MRL+/+ lupus mice report an accelerated autoimmune response in relation to exposure to TCE or some metabolites. Effects have been reported after 4 weeks of exposure to TCE at doses as low as 0.1 mg/kg/day in drinking water and have included increased antinuclear antibodies and interferon-gamma (IFN-gamma) and decreased secretion of interleukin-4 (IL-4), consistent with an inflammatory response. Autoimmune hepatitis, inflammatory skin lesions, and alopecia have been found after exposures of 32-48 weeks. Recent mechanistic experiments in mice examined oxidative stress and, specifically, effects on lipid-peroxidation-derived aldehydes in TCE-induced autoimmune disease. Two studies in humans reported an increase in IL-2 or IFN-gamma and a decrease in IL-4 in relation to occupational or environmental TCE exposure. Occupational exposure to TCE has also been associated with a severe, generalized hypersensitivity skin disorder accompanied by systemic effects, including hepatitis. In three case-control studies of scleroderma with a measure of occupational TCE exposure, the combined odds ratio was 2.5 [95% confidence interval (CI), 1.1-5.4] in men and 1.2 (95% CI, 0.58-2.6) in women.

CONCLUSION

The consistency among the studies and the concordance between the studies in mice and humans support an etiologic role of TCE in autoimmune disease. Multisite collaborations and studies of preclinical immune markers are needed to further develop this field of research.

Increased nitration and carbonylation of proteins in MRL+/+ mice exposed to trichloroethene: potential role of protein oxidation in autoimmunity

Even though reactive oxygen and nitrogen species (RONS) are implicated as mediators of autoimmune diseases (ADs), little is known about contribution of protein oxidation (carbonylation and nitration) in the pathogenesis of such diseases. The focus of this study was, therefore, to establish a link between protein oxidation and induction and/or exacerbation of autoimmunity. To achieve this, female MRL +/+ mice were treated with trichloroethene (TCE), an environmental contaminant known to induce autoimmune response, for 6 or 12 weeks (10 mmol/kg, i.p., every 4(th) day). TCE treatment resulted in significantly increased formation of nitrotyrosine (NT) and induction of iNOS in the serum at both 6 and 12 weeks of treatment, but the response was greater at 12 weeks. Likewise, TCE treatment led to greater NT formation, and iNOS protein and mRNA expression in the livers and kidneys. Moreover, TCE treatment also caused significant increases ( approximately 3 fold) in serum protein carbonyls (a marker of protein oxidation) at both 6 and 12 weeks. Significantly increased protein carbonyls were also observed in the livers and kidneys (2.1 and 1.3 fold, respectively) at 6 weeks, and to a greater extent at 12 weeks (3.5 and 2.1 fold, respectively) following TCE treatment. The increases in TCE-induced protein oxidation (carbonylation and nitration) were associated with significant increases in Th1 specific cytokine (IL-2, IFN-gamma) release into splenocyte cultures. These results suggest an association between protein oxidation and induction/exacerbation of autoimmune response. The results present a potential mechanism by which oxidatively modified proteins could contribute to TCE-induced autoimmune response and necessitates further investigations for clearly establishing the role of protein oxidation in the pathogenesis of ADs.

Lipid peroxidation-derived aldehyde-protein adducts contribute to trichloroethene-mediated autoimmunity via activation of CD4+ T cells

Lipid peroxidation is implicated in the pathogenesis of various autoimmune diseases. Lipid peroxidation-derived aldehydes such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) are highly reactive and bind to proteins, but their role in eliciting an autoimmune response and their contribution to disease pathogenesis remain unclear. To investigate the role of lipid peroxidation in the induction and/or exacerbation of autoimmune response, 6-week-old autoimmune-prone female MRL+/+ mice were treated for 4 weeks with trichloroethene (TCE; 10 mmol/kg, ip, once a week), an environmental contaminant known to induce lipid peroxidation. Sera from TCE-treated mice showed significant levels of antibodies against MDA-and HNE-adducted proteins along with antinuclear antibodies. This suggested that TCE exposure not only caused increased lipid peroxidation, but also accelerated autoimmune responses. Furthermore, stimulation of cultured splenic lymphocytes from both control and TCE-treated mice with MDA-adducted mouse serum albumin (MDA-MSA) or HNE-MSA for 72 h showed significant proliferation of CD4+ T cells in TCE-treated mice as analyzed by flow cytometry. Also, splenic lymphocytes from TCE-treated mice released more IL-2 and IFN-gamma into cultures when stimulated with MDA-MSA or HNE-MSA, suggesting a Th1 cell activation. Thus, our data suggest a role for lipid peroxidation-derived aldehydes in TCE-mediated autoimmune responses and involvement of Th1 cell activation.