Heat shock protects WEHI‐164 target cells from the cytolysis by tumor necrosis factors α and β

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Abstract
Elevated temperatures and a number of other types of stress induce synthesis of a small number of highly conserved proteins, the heat shock proteins, in a wide variety of cells. The structure and regulation of these proteins have been intensively studied but the question of the function of this universal response has remained unanswered. We studied the effect of heat shock on tumor necrosis factor-α (TNF-α)- and -β (TNF-β)-mediated cytolysis of WEHI-164 clone 13 target cells. One hour pretreatment of target cells at 42°C decreased rTNF-α-mediated lysis by 65.3%, 50.5% and 44.8% and TNF-β-mediated lysis by 61.9%, 43.2% and 38.9% at cytokine concentrations of 0.5 ng/ml, 5 ng/ml and 50 ng/ml, respectively, in an 18-h Cr-release assay. The effect was maximal when TNF-α was added 1 h after the heat shock and then gradually declined, being almost undetectable after 2 days. This pattern was found to roughly coincide with the kinetics of hsp68, the major heat-induced protein in murine cells. Heat shock treatment had no protective effect when given 1 h after addition of recombinant TNF-α. The heat-induced target cell resistance was not associated with decreased binding of recombinant TNF-α to its receptor. Inhibition of protein synthesis by cycloheximide diminished this effect by 76% and inhibition of transcription by actinomycin D abolished it completely, suggesting that de novo synthesized, heat-induced proteins protect target cells from TNF-mediated lysis in heat shock-treated WEHI cells.