Nitrosative Stress and Nitrated Proteins in Trichloroethene-Mediated Autoimmunity

Abstract

Exposure to trichloroethene (TCE), a ubiquitous environmental contaminant, has been linked to a variety of autoimmune diseases (ADs) including SLE, scleroderma and hepatitis. Mechanisms involved in the pathogenesis of ADs are largely unknown. Earlier studies from our laboratory in MRL+/+ mice suggested the contribution of oxidative/nitrosative stress in TCE-induced autoimmunity, and N-acetylcysteine (NAC) supplementation provided protection by attenuating oxidative stress. This study was undertaken to further evaluate the contribution of nitrosative stress in TCE-mediated autoimmunity and to identify proteins susceptible to nitrosative stress. Groups of female MRL +/+ mice were given TCE, NAC or TCE + NAC for 6 weeks (TCE, 10 mmol/kg, i.p., every 4th day; NAC, ∼250 mg/kg/day via drinking water). TCE exposure led to significant increases in serum anti-nuclear and anti-histone antibodies together with significant induction of iNOS and increased formation of nitrotyrosine (NT) in sera and livers. Proteomic analysis identified 14 additional nitrated proteins in the livers of TCE-treated mice. Furthermore, TCE exposure led to decreased GSH levels and increased activation of NF-κB. Remarkably, NAC supplementation not only ameliorated TCE-induced nitrosative stress as evident from decreased iNOS, NT, nitrated proteins, NF-κB p65 activation and increased GSH levels, but also the markers of autoimmunity, as evident from decreased levels of autoantibodies in the sera. These findings provide support to the role of nitrosative stress in TCE-mediated autoimmune response and identify specific nitrated proteins which could have autoimmune potential. Attenuation of TCE-induced autoimmunity in mice by NAC provides an approach for designing therapeutic strategies.

iNOS null MRL+/+ mice show attenuation of trichloroethene-mediated autoimmunity: contribution of reactive nitrogen species and lipid-derived reactive aldehydes

“…iNOS-null mice were backcrossed to MRL +/+ mice for 10 generations and then homozygous mutants (iNOS-null MRL+/+ mice) were obtained from N10 heterozygous intercrosses. Female MRL+/+ and iNOS-null MRL+/+ mice, in groups of six each, were treated with TCE (10 mmol/kg, i.p., every 4 th day) [15,16,30,31,39] for 6 weeks, their respective controls received corn oil only. After 6 weeks of treatment, the animals were euthanized under nembutal (sodium pentobarbital) anesthesia, and blood was withdrawn from the inferior vena cava.…”

“…Real-time RT-PCR was performed essentially as described earlier [15,16]. Briefly, total RNA was isolated from livers using a RiboPure kit (Ambion, Austin, TX) following the manufacturer's instructions.…”

“…In addition, ONOO − -modified endogenous proteins and DNA may become immunogenic, leading to a break in immune tolerance [3,10–12]. Accumulating evidence in murine lupus suggests an association between increasing iNOS activity and development and progression of ADs [6,8,9,13–16]. Studies using competitive inhibitors provide additional support that iNOS could play a pathogenic role in murine ADs [6,8,9,15].…”

The role of aldehyde dehygrogenase 2 in liver injury caused by vinyl chloride and high-fat diet.

“…Lipid accumulation and glycogen storage are associated with energy metabolism in liver, disruption of carbohydrate/lipid homeostasis can potentially impact hepatic regeneration and induce hepatotoxicity (70). Liver sections were stained for ORO and PAS to evaluate hepatic metabolism.…”

“…Other related organochlorine contaminants such as TCE and PCE, that have also been demonstrated to cause liver injury, could also be following a similar pathway (e.g. oxidative stress) (70).…”