Objective: The alpha 1-adrenoreceptor blocker doxazosin, which in the ALLHAT trial was associated with a greater risk of heart failure than the diuretic chlorthalidone, induces the apoptosis of human and murine cardiomyocytes regardless of alpha 1-adrenoreceptor blockade. We aimed to throw light on the mechanism of this process.
Methods: Murine cardiomyocytes (HL-1) and primary cultures of human and neonatal rat cardiomyocytes were treated with 25 micromol/L doxazosin for between 0.5 and 48 h. cDNA microarray analysis, real-time RT-PCR, and Western blotting were performed to detect possible changes in gene expression and/or activation of proteins that could be involved in doxazosin-induced apoptosis.
Results: Microarray analysis revealed changes in the expression of genes directly involved in the apoptotic end-stage of the cellular response to endoplasmic reticulum (ER) stress. Doxazosin considerably increased transcription and translation of gadd153, C/epb beta, and DOC-1 in cardiomyocytes as well as translocation of GADD153 to the nucleus, phosphorylation of p38 MAPK (a GADD153 activator), and the initial phosphorylation and subsequent cleavage of focal adhesion kinase (FAK). Experiments repeated following blockade of alpha(1)-adrenoreceptors showed no alteration of the above effects of doxazosin.
Conclusion: Doxazosin induces the apoptosis of cardiomyocytes via the ER pathway, with increased production of C/EBP beta, GADD153 and DOC-1. Likewise it increases phosphorylation of the GADD153 activator p38 MAPK and induces first the phosphorylation, and then the cleavage, of FAK. These effects are not mediated by alpha 1-adrenoreceptors.