Gene Expression Profiles of Peripheral Blood Mononuclear Cells Reveal Transcriptional Signatures as Novel Biomarkers of Cardiac Remodeling in Rats With Aldosteronism and Hypertensive Heart Disease

Abstract

In searching for a noninvasive surrogate tissue having mimicry with the prooxidant/-proinflammatory hypertensive heart disease (HHD) phenotype, we turned to peripheral blood mononuclear cells (PBMC). We tested whether iterations in [Ca2+]i, [Zn2+]i and oxidative stress in cardiomyocytes and PBMC would complement each other eliciting similar shifts in gene expression profiles in these tissues demonstrable during preclinical (wk 1) and pathologic (wk 4) stages of aldosterone/salt treatment (ALDOST). Inappropriate neurohormonal activation contributes to pathologic remodeling of myocardium in HHD associated with aldosteronism. In rats receiving chronic ALDOST, evidence of reparative fibrosis replacing necrotic cardiomyocytes and coronary vasculopathy appears at wk 4 associated with the induction of oxidative stress by mitochondria that overwhelms endogenous, largely Zn2+-based, antioxidant defenses. Biomarker-guided prediction of risk prior to the appearance of cardiac pathology would prove invaluable. In PBMC and cardiomyocytes, quantitation of cytoplasmic free Ca2+ and Zn2+, H2O2 and 8-iosprostane levels, as well as isolation of RNA and gene expression, together with statistical and clustering analyses, and confirmation of genes by in situ hybridization and RT-PCR, were performed. Compared to controls, at wk 1 and 4 ALDOST, we found comparable: increments in [Ca2+]i, [Zn2+]i and 8-isoprotane coupled to increased H2O2 production in cardiac mitochondria and PBMC, together with the common networks of expression profiles dominated by genes involved in oxidative stress, inflammation and repair. These included three central Ingenuity pathway-linked genes: p38MAPK, a stress-responsive protein; NFκB, a redox-sensitive transcription factor and a proinflammatory cascade it regulates; and TGF-β1, a fibrogenic cytokine involved in tissue repair. Significant overlapping demonstrated in the molecular mimicry of PBMC and cardiomyocytes during preclinical and pathologic stages of ALDOST implicates that transcriptional signatures of PBMC may serve as early noninvasive and novel sentinels predictive of impending pathologic remodeling in HHD.