Effects of Acute γ-Hexachlorocyclohexane Intoxication in Relation to the Redox Regulation of Nuclear Factor-κB,Cytokine Gene Expression,and Liver Injury in the Rat

Abstract

γ-Hexachlorocyclohexane-induced hepatotoxicity is associated with oxidative stress. We tested the hypothesis that γ-hexachlorocyclohexane triggers the redox activation of nuclear factor-κB(NF-κB), leading to proinflammatory cytokine expression. Liver NF-κB activation (electrophoretic mobility shift assay), tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α) mRNA expression (reverse transcription-polymerase chain reaction), and their serum levels (enzyme-linked immunosorbent assay) were measured at different times after γ-hexachlorocyclohexane treatment(50 mg/kg). The relationship between these and hepatic O₂ uptake, glutathione and protein carbonyl levels, and sinusoidal lactate dehydrogenase (LDH) efflux in liver perfusion studies was determined.γ-Hexachlorocyclohexane increased liver NF-κB DNA binding at 14-22 h after treatment, concomitantly with significant glutathione depletion and an increase in the rate of O₂ consumption, the content of protein carbonyls, and the sinusoidal LDH efflux. In these conditions, the expression of TNF-α and IL-1α is enhanced, with maximal increases in their respective mRNA content and serum levels of the cytokines being elicited at 18 h after γ-hexachlorocyclohexane treatment. All these changes are suppressed by the administration of α-tocopherol (100 mg/kg) or the Kupffer cell inactivator gadolinium chloride (10 mg/kg) prior to γ-hexachlorocyclohexane. γ-Hexachlorocyclohexane-induced TNF-α levels in serum are suppressed by pretreatment with an antisense oligonucleotide (ASO TJU-2755; daily doses of 10 mg/kg for 2 days) targeting the primary transcript for the cytokine, whereas those of IL-1α are not modified. It is concluded that γ-hexachlorocyclohexane-induced liver oxidative stress triggers the DNA binding activity of NF-κB, with the consequent increase in the expression of NF-κB-dependent genes for TNF-α and for IL-1α, factors that may mediate the hepatotoxicity of the insecticide.