The Heat Shock Response Inhibits RANTES Gene Expression in Cultured Human Lung Epithelium

Abstract

The chemokine RANTES is thought to be involved in the pathophysiology of inflammation-associated acute lung injury. Although much is known regarding signals that induce RANTES gene expression, relatively few data exist regarding signals that inhibit RANTES gene expression. The heat shock response, a highly conserved cellular defense mechanism, has been demonstrated to inhibit a variety of lung proinflammatory responses. We tested the hypothesis that induction of the heat shock response inhibits RANTES gene expression. Treatment of A549 cells with TNF-α induced RANTES gene expression in a concentration-dependent manner. Induction of the heat shock response inhibited subsequent TNF-α-mediated RANTES mRNA expression and secretion of immunoreactive RANTES. Transient transfection assays involving a RANTES promoter-luciferase reporter plasmid demonstrated that the heat shock response inhibited TNF-α-mediated activation of the RANTES promoter. Inhibition of NF-κB nuclear translocation with isohelenin inhibited TNF-α-mediated RANTES mRNA expression, indicating that RANTES gene expression is NF-κB dependent in A549 cells. Induction of the heat shock response inhibited degradation of the NF-κB inhibitory protein, I-κBα but did not significantly inhibit phosphorylation of I-κBα. We conclude that the heat shock response inhibits RANTES gene expression by a mechanism involving inhibition of NF-κB nuclear translocation and subsequent inhibition of RANTES promoter activation. The mechanism by which the heat shock response inhibits NF-κB nuclear translocation involves stabilization of I-κBα, without significantly affecting phosphorylation of I-κBα.