Inhibition of Immune-Mediated Concanavalin A-Induced Liver Damage by Free-Radical Scavengers

Abstract

The aims of the present study were to elucidate whether oxidative stress has a role in Con A-induced hepatitis and to examine if antioxidants may protect against liver damage in this model. Hepatitis was induced in Balb/c mice by administration of Con A (18 mg/kg) to the tail vein. Liver enzymes and histology were determined 24 h after Con A injection. Tumor necrosis factor alpha (TNFalpha) and interleukin-10 (IL-10) levels were assayed 2 h after Con A injection. Hepatic malondialdehyde levels were measured at 1, 3, 8, 12, 18, and 24 h after Con A injection in order to examine the timing of free-radicals formation. Nuclear factor kappa B (NF-kappabeta) activation was determined by electrophoresis mobility shift assay (EMSA) 1 and 2 h after Con A injection. In separate experiments, mice were pretreated with either dimethylsulfoxide or dimethylthiourea before Con A inoculation. The antioxidant and NF-kappabeta inhibitor pyrrolidine dithiocarbamate (PDTC) was used as positive control. Hepatic malondialdehyde levels increased 12, 18, and 24 h after Con A inoculation but not earlier. Serum levels of liver enzymes and TNFalpha, hepatic malondialdehyde, and protein carbonyls and the histologic necroinflammatory score were significantly reduced in the antioxidants-treated mice, while IL-10 levels were increased. Dimethylsulfoxide, dimethylthiourea, and PDTC inhibited oxidative stress, but only PDTC inhibited Con A-induced NF-kappaB activation. Reactive oxygen species play a role in immune-mediated Con A-induced hepatitis probably secondary to immune-mediated liver damage. Scavenging of reactive oxygen species by antioxidants prevents hepatitis independently of NF-kappaB inhibition and may be a new therapeutic target in this experimental model.