Thiol redox status critically influences mitochondrial response to thyroid hormone-induced hepatic oxidative injury: A temporal analysis

Abstract

Liver is a major target organ for thyroid hormone. The objective of the present study was to investigate temporal regulation of mitochondrial glutathione and protein-bound thiol redox status in hyperthyroid liver. Mitochondria were isolated from control and hyperthyroid rat liver tissues at different time intervals, i.e., 24, 72, and 120 h following treatment, and sub-fractionated into sub-mitochondrial particles (SMPs) and matrix fractions. Increased prooxidant levels were indicative of oxidative stress in hyperthyroid mitochondria. Sensitivity to membrane lipid peroxidation (LPx) was maximal after 24 h, which subsided with time. Oxidative damage to proteins was evident as high carbonylation after 72 h; thiol residue damage was an early phenomenon. Reduced and oxidized glutathione (GSH and GSSG) pools of mitochondria were progressively depleted, thereby, impairing matrix antioxidant capacity. However, adaptations to withstand oxidative challenge were elicited in both SMPs and matrix fractions over the long term. It is concluded that maintenance of appropriate intra-mitochondrial glutathione and protein-bound thiol redox status could be instrumental in attenuating thyroid hormone-induced oxidative stress.