Renalase deficiency aggravates ischemic myocardial damage

Abstract

Chronic kidney disease (CKD) leads to an 18-fold increase in cardiovascular complications not fully explained by traditional risk factors. Levels of renalase, a recently discovered oxidase that metabolizes catecholamines, are decreased in CKD. Here we show that renalase deficiency in a mouse knockout model causes increased plasma catecholamine levels and hypertension. Plasma blood urea nitrogen, creatinine, and aldosterone were unaffected. However, knockout mice had normal systolic function and mild ventricular hypertrophy but tolerated cardiac ischemia poorly and developed myocardial necrosis threefold more severe than that found in wild-type mice. Treatment with recombinant renalase completely rescued the cardiac phenotype. To gain insight into the mechanisms mediating this cardioprotective effect, we tested if gene deletion affected nitrate and glutathione metabolism, but found no differences between hearts of knockout and wild-type mice. The ratio of oxidized (NAD) to reduced (NADH) nicotinamide adenine dinucleotide in cardiac tissue, however, was significantly decreased in the hearts of renalase knockout mice, as was plasma NADH oxidase activity. In vitro studies confirmed that renalase metabolizes NADH and catecholamines. Thus, renalase plays an important role in cardiovascular pathology and its replacement may reduce cardiac complications in renalase-deficient states such as CKD.

Is Renalase a Novel Player in Catecholaminergic Signaling? The Mystery of the Catalytic Activity of an Intriguing New Flavoenzyme

“…At variance with previous reports, we found that our protein, although eliciting the expected effects on blood pressure when injected into rats, was completely devoid of any amine oxidase activity [40]. At the same time, Desir and coauthors reasoned that, since the renalase sequence contains the dinucleotide binding motif GXGXXG, which is the hallmark of the Rossmann fold, it could bind either NAD or NADP [17,33,42]. Indeed, they found that in vitro refolded recombinant human renalase possesses NADH-oxidase activity, with a K m NADH of 15 ± 1 M, and a V max of 15 ± 0.1 nmol/min/mg, corresponding to a k cat of 0.40 min -1 [17].…”

“…The main isoform (renalase 1, NP_001026879) is composed of 342 residues, with a theoretical molecular mass of 37,847 Da [7,8,15]. The orthologous mouse gene is annotated on chromosome 19C1 [16] and, as detailed in Chapter 7.1, it has been recently inactivated by homologous recombination, providing important experimental clues about its role in the modulation of the cardiovascular system [8,17].…”

“…Desir's group reported the production of two recombinant forms of human renalase in Escherichia coli. Initially, the protein was expressed as an N-terminal fusion with glutathione S-transferase (GST) and purified in soluble form by affinity chromatography on a Glutathione Sepharose column [1,17]. GSTrenalase was used to raise anti-renalase polyclonal antibodies and to study its catalytic activity in vitro.…”

“…GSTrenalase was used to raise anti-renalase polyclonal antibodies and to study its catalytic activity in vitro. Later, two recombinant allelic isoforms of human renalase were synthesized with no tag or fusion partners, extracted from E. coli inclusion bodies by chaotropic agents and refolded in vitro in the presence of FAD [17,33]. Wang and coworkers produced human renalase in E. coli as a fusion protein containing at the N-terminus the pelB leader sequence for localization in the cell periplasm, and a C-terminal His-tag.…”

“…At the same time, Desir and coauthors reasoned that, since the renalase sequence contains the dinucleotide binding motif GXGXXG, which is the hallmark of the Rossmann fold, it could bind either NAD or NADP [17,33,42]. Indeed, they found that in vitro refolded recombinant human renalase possesses NADH-oxidase activity, with a K m NADH of 15 ± 1 M, and a V max of 15 ± 0.1 nmol/min/mg, corresponding to a k cat of 0.40 min -1 [17]. The enzyme was inactive towards NADPH.…”