Zinc deficiency enhances interleukin-1α-induced metallothionein-1 expression in rats

Abstract

This study investigated whether interleukin-1α-induced metallothionein gene expression is affected by zinc deficiency. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) or a zinc-supplemented diet [50.8 mg zinc/kg; controls for the diet included pair-fed (PF) and ad libitum consumption groups (AL)] for 4 wk. All rats except those that served as controls for interleukin-1α administration, (injected with vehicle and killed at 0 h) were then injected subcutaneously with interleukin-1α (2 x 107 units/kg body wt) and killed at 3, 6, 12, 24 and 72 h after the injection. Compared with AL and/or PF rats, zinc depletion significantly reduced zinc concentrations in plasma and liver but not in kidney or intestine, and significantly reduced hepatic, renal, and intestinal metallothionein-1 mRNA levels analyzed by competitive reverse transcription- polymerase chain reaction (RT-PCR). Interleukin-1α injection reduced plasma zinc concentration and enhanced liver zinc concentration, but did not affect zinc levels in kidney or intestine. Metallothionein-1 mRNA was significantly elevated by interleukin-1α in liver, kidney and intestine of all groups; the levels in liver and kidney of ZD rats 6 h after the injection were significantly higher than those of AL or PF rats. Liver metallothionein protein levels were enhanced after interleukin-1α injection in both AL and ZD rats. Semiquantitative RT-PCR revealed significantly higher hepatic levels of interleukin-1 receptor type-I mRNA in ZD rats than in AL and PF rats but no differences in renal or intestinal tissues among groups before interleukin-1α challenge. In conclusion, zinc deficiency induces upregulation of metallothionein-1 gene expression in response to interleukin- 1α challenge in rats.