Cardiotrophin-1 reduces stress-induced heat shock protein production in cardiac myocytes.

Cardiotrophin-1 (CT-1) can induce expression of the protective heat shock proteins (hsps) in cardiac cells. We show here that, unlike the stress induced accumulation of hsps, the effect of CT-1 is not accompanied by increased hsp mRNA levels and is insensitive to the RNA synthesis inhibitor actinomycin D, suggesting that it occurs at the post-transcriptional level. Pre-treatment with CT-1 reduces the ability of heat shock to induce hsp expression and this effect occurs at the transcriptional level. Hence, CT-1 and stress induce the hsps via different pathways which can antagonise one another. The mechanisms of these effects and their potential impact on the use of CT-1 as a cardioprotective agent are discussed.