The heat shock response inhibits RANTES gene expression in cultured human lung epithelium

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-alpha induced RANTES gene expression in a concentration-dependent manner. Induction of the heat shock response inhibited subsequent TNF-alpha-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-alpha-mediated activation of the RANTES promoter. Inhibition of NF-kappaB nuclear translocation with isohelenin inhibited TNF-alpha-mediated RANTES mRNA expression, indicating that RANTES gene expression is NF-kappaB dependent in A549 cells. Induction of the heat shock response inhibited degradation of the NF-kappaB inhibitory protein, I-kappaBalpha but did not significantly inhibit phosphorylation of I-kappaBalpha. We conclude that the heat shock response inhibits RANTES gene expression by a mechanism involving inhibition of NF-kappaB nuclear translocation and subsequent inhibition of RANTES promoter activation. The mechanism by which the heat shock response inhibits NF-kappaB nuclear translocation involves stabilization of I-kappaBalpha, without significantly affecting phosphorylation of I-kappaBalpha.