Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide
Authors: Montiel V , Bella R , Michel L , Robinson E , Jonas J.C , Michel T , Beauloye C.H , Bertrand L , Ghigo A , Geninatti-Crich S , Yool A , Zimmermann W , Roderick L , Devuyst O , Balligand J.L 
Published: November 2020

Abstract

Background
Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown.

Purpose
We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy.

Methods
We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis.

Results
RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis.

Conclusion
We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure.

Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio