Neutrophil Gelatinase-Associated Lipocalin Is a Novel Mineralocorticoid Target in the Cardiovascular System

Abstract

Abstract-Mineralocorticoid receptor (MR) activation may be deleterious to the cardiovascular system, and MR antagonists improve morbidity and mortality of patients with heart failure. However, mineralocorticoid signaling in the heart remains largely unknown. Using a pan-genomic transcriptomic analysis, we identified neutrophil gelatinase-associated lipocalin (NGAL or lipocalin 2) as a strongly induced gene in the heart of mice with conditional and targeted MR overexpression in cardiomyocytes (whereas induction was low in glucocorticoid receptor-overexpressing mice). NGAL mRNA levels were enhanced after hormonal stimulation by the MR ligand aldosterone in cultured cardiac cells and in the heart of wild-type mice. Mineralocorticoid pathological challenge induced by nephrectomy/aldosterone/salt treatment upregulated NGAL expression in the heart and aorta and its plasma levels. We show evidence for MR binding to an NGAL promoter, providing a mechanism for NGAL regulation. We propose that NGAL may be a marker of mineralocorticoiddependent injury in the cardiovascular system in mice. (Aldo) is a main regulator of renal sodium reabsorption, with an overall effect on volemia and blood pressure. Aldo binds to the mineralocorticoid receptor (MR), a transcription factor of the nuclear receptor family present in the kidney.1 Extrarenal pathophysiological effects of this hormone have been characterized, extending its actions to the CV system, the brain, the adipose tissue, the skin, and the eye.2-5 Inappropriate MR activation has been shown to promote cardiac fibrosis in experimental models 6,7 The Randomized Aldactone Evaluation Study, 8 Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study, 9 and Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure 10 clinical trials have demonstrated that the addition of the MR antagonists spironolactone or eplerenone to standard care markedly reduced the overall and CV mortality in patients with left ventricular systolic dysfunction and mild or severe symptoms of chronic heart failure (HF) or with HF signs after acute myocardial infarction.The molecular mechanisms of Aldo and MR activation in the CV system are not yet fully established. A better understanding of these mechanisms may unveil novel biotargets for pharmacological modulation of the signaling cascades induced by mineralocorticoids in CV diseases.In this study we identified neutrophil gelatinase-associated lipocalin (NGAL) in a pan-genomic transcriptomic analysis performed on hearts of transgenic mice that overexpress the MR in cardiomyocytes. NGAL (lipocalin 2 or 24p3) is a 25-kDa glycoprotein belonging to the lipocalin superfamily.11,12 The cell-specific roles of NGAL remain elusive, but enhanced NGAL in tissues, plasma, or urine has been reported in several pathological states, such as kidney failure 13 and obesity, 14,15 and many other situations. Increased systemic and myocardial expressions of NGAL have been observed in clinical and experimental HF. 16,17 Hormona...

Neutrophil Gelatinase–Associated Lipocalin, a Novel Mineralocorticoid Biotarget, Mediates Vascular Profibrotic Effects of Mineralocorticoids

“…We identified lipocalin 2 (Lcn2), also known as neutrophil gelatinase-associated lipocalin (NGAL) or 24p3, as a novel MR target in the cardiovascular system in mice, using a pangenomic analysis with dedicated transgenic animal models with targeted MR alteration in cardiomyocytes. 5 We showed that MR, as transcription factor, can bind directly the promoter of Lcn2 and controls its transcription.…”

“…We identified lipocalin 2 (Lcn2), also known as neutrophil gelatinase-associated lipocalin (NGAL) or 24p3, as a novel MR target in the cardiovascular system in mice, using a pangenomic analysis with dedicated transgenic animal models with targeted MR alteration in cardiomyocytes. 5 We showed that MR, as transcription factor, can bind directly the promoter of Lcn2 and controls its transcription.5 Lcn2 is a 25-kDa secreted glycoprotein belonging to the lipocalin superfamily, which binds small lipophilic substances. 6 Increased systemic levels and myocardial expression of Lcn2/NGAL have been reported in several experimental models and CVDs, such as HF and atherosclerosis; it is also is considered as a biomarker of renal dysfunction because its plasma and urinary concentrations increase in kidney diseases.…”

“…29,30 We and others, have previously showed that Lcn2/NGAL is a direct target gene of the aldosterone/MR signaling pathway in the cardiovascular system. 5,31,32 The aim of this study was to analyze whether Lcn2/NGAL is a key actor of mineralocorticoid action in the cardiovascular system. We analyzed 2 conditions associated with increased aldosterone/MR activation (AO in human subjects and NAS challenge in a mouse model with Lcn2 gene deletion) and provide mechanistic insights in the profibrotic effects of Lcn2/NGAL.…”

Aldosterone-Specific Activation of Cardiomyocyte Mineralocorticoid Receptor In Vivo

“…19 To test whether our approach allows the identification of aldosterone-regulated genes in cardiomyocytes, we first studied how aldosterone administration affects cardiac Ngal expression in Ctrl and MR-Cardio mice. As we previously described, 19 Ngal expression (mRNA and protein) was upregulated in MR-Cardio mice when compared with Ctrl mice. Aldosterone further enhanced cardiac Ngal expression in MR-cardio mice ( Figure 1).…”

“…In Ctrl mice, as previously published, Ngal was not regulated by aldosterone at the low dose used. 19 Thus, our strategy seems valuable to highlight genes dependent on MR activation by aldosterone in cardiomyocytes.…”