Polycystin 2-dependent cardio-protective mechanisms revealed by cardiac stress

Although autosomal dominant polycystic kidney disease (ADPKD) is characterized by the development of multiple kidney cysts, the most frequent cause of death in ADPKD patients is cardiovascular disease. ADPKD is linked to mutations in PKD1 or pkd2, the genes that encode for the proteins polycystin 1 and polycystin 2 (PC1 and PC2, respectively). The cardiovascular complications have been assumed to be a consequence of renal hypertension and activation of renin/angiotensin/aldosterone (RAAS) pathway. However, the expression of PC1 and PC2 in cardiac tissue suggests additional direct effects of these proteins on cardiac function. We previously reported that zebrafish lacking PC2 develop heart failure, and that heterozygous Pkd2(+/-) mice are hypersensitive to acute beta-adrenergic receptor (beta AR) stimulation. Here, we investigate the effect of cardiac stress (prolonged continuous beta AR stimulus) on Pkd2(+/-) mice. After beta AR stimulation for 7 days, wild-type (WT) mice had increased left ventricular mass and natriuretic peptide (ANP and BNP) mRNA levels. The WT mice also had upregulated levels of PC2 and chromogranin B (CGB, an upstream regulator of BNP). Conversely, Pkd2(+/-) mice had increased left ventricular mass, but natriuretic peptide and CGB expression levels remained constant. Reversal of the increased cardiac mass was observed in WT mice 3 days after cessation of the beta AR stimulation, but not in Pkd2(+/-) mice. We suggest that cardiac stress leads to upregulation of the PC2-CGB-BNP signaling axis, and this pathway regulates the production of cardio-protective natriuretic peptides. The lack of a PC2-dependent cardio-protective function may contribute to the severity of cardiac dysfunction in Pkd2(+/-) mice and in ADPKD patients.