Glucocorticoids Suppress the Inflammation-Mediated Tolerance to Acute Toxicity of Cadmium in Mice

Abstract

Several compounds have been shown to cause acute toxicity to cadmium (Cd). The mechanism of tolerance to Cd toxicity induced by glucocorticoids or by inflammation involves induction of metallothionein (MT) synthesis via glucocorticoid response elements or by inflammatory cytokines. We have demonstrated previously that the synthetic glucocorticoid dexamethasone suppresses inflammation-mediated induction of hepatic MT synthesis. Here we investigated the effect of glucocorticoid on tolerance to Cd induced by inflammation in mice. The LD50 of Cd for mice with induced inflammation by injection with turpentine oil (Tur-mice) was higher than the LD50 in control mice. Pretreatment of Tur-mice with dexamethasone to the Tur-mice (Dex+Tur-mice) resulted in a decrease in LD50 after Cd treatment. A significant increase in plasma alanine aminotransferase and aspartate aminotransferase levels in the Dex+Tur-mice was observed at lower doses of Cd than in the Tur-mice and at higher doses of Cd than in control mice. Dexamethasone did not suppress tolerance to cadmium toxicity in the testes of the Tur-mice. Pretreatment of Tur-mice with dexamethasone resulted in suppression of both plasma interleukin (IL)-6 elevation and in suppression of hepatic MT levels when induced by inflammation but not when induced by Cd. These data suggest that suppression of tolerance to Cd toxicity induced by glucocorticoid may involve hepatic MT synthesis mediated by inflammatory cytokines, such as IL-6. We suggest that the inflammatory response can modulate Cd toxicity by induction of MT by inflammatory cytokines.