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 r egarding signals that induce RANTES gene expression, relatively few da ta exist regarding signals that inhibit RANTES gene expression. The he at shock response, a highly conserved cellular defense mechanism, has been demonstrated to inhibit a variety of lung proinflammatory respons es. We tested the hypothesis that induction of the heat shock response inhibits RANTES gene expression. Treatment of A549 cells with TNF-alp ha induced RANTES gene expression in a concentration-dependent manner. Induction of the heat shock response inhibited subsequent TNF-cy-medi ated RANTES mRNA expression and secretion of immunoreactive RANTES, Tr ansient transfection assays involving a RANTES promoter-luciferase rep orter plasmid demonstrated that the heat shock response inhibited TNF- alpha-mediated activation of the RANTES promoter. Inhibition of NF-kap pa B nuclear translocation with isohelenin inhibited TNF-alpha-mediate d RANTES mRNA expression, indicating that RANTES gene expression is NF -kappa B dependent in A549 cells. Induction of the heat shock response inhibited degradation of the NF-kappa B inhibitory protein, I-kappa B alpha but did not significantly inhibit phosphorylation of I-kappa B alpha, We conclude that the heat shock response inhibits RANTES gene e xpression by a mechanism involving inhibition of NF-kappa B nuclear tr anslocation and subsequent inhibition of RANTES promoter activation. T he mechanism by which the heat shock response inhibits NF-kappa B nucl ear translocation involves stabilization of I-kappa B alpha, without s ignificantly affecting phosphorylation of I-kappa B alpha.