Gp91 phox-homologs in cardiomyocytes: a putative novel source of reactive oxygen species. Molecular and functional characterization in rat and human cardiomyocytes
10 / 2002 - 10 / 2005
In non-cardiomyocytes it has been hypothesized that reactive oxygen species (ROS) can be produced by putative NADPH oxidase(s). Interestingly, several cell-specific homologs of the enzymatic component of the phagocyte NADPH oxidasae, gp91phox (renamed as Nox2), have recently been detected, i.e. Nox1 (colon, prostate, uterus, vascular smooth muscle cells), Nox4 (kidney) and Duox-1 and 2 (thyroid gland). These cell-specific gp91phox homologs have been related to cell-specific functions. However, until now, no 91phox homolog has been detected in cardiomyocytes. We have recently found in rat embryonic cardiomyoblast H9c2 cells adult cardiomyocytes from the rat and in human cardiomyocytes, gp91phox homologs by cDNA and Western blot analysis, while in patients who had died subsequently to myocardial infarction, gp91phox was found not only within ischemic damaged cardiomyocytes, but especially at perinuclear sites of viable cardiomyocytes surrounding the infarcted area. Therefore we hypothesize that also in cardiomyocytes gp91phox homologs play a role in ROS synthesis. We will test this hypothesis by: 1) isolation of full-length cDNA and their possible splice variants in rat and human cardiomyocytes; 2) establishing their tissue distribution in rat and humans; 3) transfection in fibroblasts with the rat and human homologs and establishing ROS production by these cells; 4) transfection of H9c2 cells by homolog antisense oligonucleotides in non-ischemic and ischemia/reperfusion conditions and subsequently establishing their effect; 5) testing the functional role of the homologs in an in vivo myocardial infarction and heart hypertrophy model of the rat; 6) analysing the role of the homologs within human heart disease by studying their expression in patients with myocardial infarction and cardiomyopathy. This project thus will result in the identification of (a) new oxidase(s) within cardiomyocytes, which could lead to the recognition of a new intracellular mediator and thus to a potential new therapeutical tool within human heart disease.