Elabela Research Articles

Sustained ELABELA Gene Therapy in High-salt Diet-induced Hypertensive Rats.

Elabela (ELA) is a recently identified apelin receptor agonist essential for cardiac development, but its biology and therapeutic potential are unclear. In humans, ELA transcripts are detected in embryonic stem cells, induced pluripotent stem cells, kidney, heart and blood vessels. ELA through the apelin (APJ) receptor promotes angiogenesis in vitro, relaxes murine aortic blood vessels and attenuates high blood pressure in vivo. The APJ receptor when bound to its original ligand, apelin, exerts peripheral vasodilatory and positive inotropic effects, conferring cardioprotection in vivo. This study initially assessed endogenous ELA expression in normal and diseased rats and then characterized the effects of long-term ELA gene delivery by adeno-associated virus serotype 9 (AAV9) vectors on cardiorenal function in Dahl salt-sensitive rats (DS) on a high-salt diet over 3 months. Endogenous ELA was predominantly expressed in the kidneys, especially in the renal collecting duct cells and was not affected by disease. Rat ELA was overexpressed in the heart via AAV9 vector by a single intravenous injection. ELA-treated animals showed delayed onset of blood pressure elevation. Prior to high-salt diet, a reduction in the fractional sodium and chloride excretion was observed in rats given the AAV9-ELA vector. After three months on a high-salt diet, ELA preserved glomerular architecture, decreased renal fibrosis and suppressed expression of fibrosis-associated genes in the kidneys. ELA is constitutively expressed in renal collecting ducts in rats. Sustained AAV-ELA expression may offer a potential long-term therapy for hypertension and renal remodeling.

297. The Influence of ELABELA AAV Gene Therapy on Cardiorenal Function in Rat Models of Salt-Induced Hypertension and Myocardial Infarction

Elabela (ELA) is a recently identified apelin receptor agonist essential for cardiac development, but its biology and therapeutic potential are unclear. The apelin receptor when bound to its original ligand, apelin, exerts peripheral vasodilatory and positive inotropic effects. We initially assessed endogenous ELA expression in normal and diseased rats. ELA was predominantly expressed in kidneys, especially in renal collecting duct cells and was not affected by disease. We then characterized the effects of long-term, adeno-associated virus (AAV)-ELA gene delivery on cardiorenal function in Dahl salt-sensitive rats (DS) on a high-salt diet. We overexpressed codon optimized rat ELA in the heart via AAV9 vector by a single intravenous injection. This led to a delayed onset of blood pressure (BP) elevation, and ELA-treated rats had lower BP than controls starting at 5 weeks post-injection (p.i.). As well, ELA significantly reduced fractional sodium and chloride excretion in treated (4 days p.i.), normotensive DS rats on low-salt diet, suggesting ELA's role in sodium and chloride readsorption. Glomerular architecture was better preserved in rats treated with the AAV9-ELA vector. A decrease in renal fibrosis and the significantly suppressed expression of fibrosis associated genes, including transforming growth factor beta (TGF-β), collagen, type 1, alpha 1 (COL1A1) and fibronectin 1 (FN1), was also seen in the treated group. Since ELA is essential for cardiac development, we additionally assessed the impact of the AAV9-ELA vector on cardiac repair in a rat myocardial infarction (MI) model. When compared with control MI rats, ELA treatment did not significantly improve cardiac function or structure. Thus, long-term ELA gene delivery may offer a potential therapy for hypertension and renal remodeling, but its application for MI may be limited.

Discovery and Structure-Activity Relationship of a Bioactive Fragment of ELABELA that Modulates Vascular and Cardiac Functions.

ELABELA (ELA) was recently discovered as a novel endogenous ligand of the apelin receptor (APJ), a G protein-coupled receptor. ELA signaling was demonstrated to be crucial for normal heart and vasculature development during embryogenesis. We delineate here ELA's structure-activity relationships and report the identification of analogue 3 (ELA(19-32)), a fragment of ELA that binds to APJ, activates the Gαi1 and β-arrestin-2 signaling pathways, and induces receptor internalization similarly to its parent endogenous peptide. An alanine scan performed on 3 revealed that the C-terminal residues are critical for binding to APJ and signaling. Finally, using isolated-perfused hearts and in vivo hemodynamic and echocardiographic measurements, we demonstrate that ELA and 3 both reduce arterial pressure and exert positive inotropic effects on the heart. Altogether, these results present ELA and 3 as potential therapeutic options in managing cardiovascular diseases.

Central action of ELABELA reduces food intake and activates arginine vasopressin and corticotropin-releasing hormone neurons in the hypothalamic paraventricular nucleus.

ELABELA (ELA) is a novel hormone consisting of 32 amino acid peptides found in humans as well as other vertebrates and is considered to play an important role in the circulatory system through the apelin receptor (APJ). However, whether ELA also acts in the central nervous system remains unknown. Here, we show that ELA functions as an anorexigenic hormone in adult mouse brain. An intracerebroventricular injection of ELA reduces food intake and activates arginine vasopressin (AVP) and corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVN), a hypothalamic region that regulates food intake. Cytosolic calcium ([Ca]i) measurement shows that ELA dose dependently increases [Ca]i in single AVP and CRH-immunoreactive neurons isolated from the PVN. Our data suggest that ELA functions as an anorexigenic hormone through activation of AVP and CRH neurons in the PVN.

ELABELA Is an Endogenous Growth Factor that Sustains hESC Self-Renewal via the PI3K/AKT Pathway

ELABELA (ELA) is a peptide hormone required for heart development that signals via the Apelin Receptor (APLNR, APJ). ELA is also abundantly secreted by human embryonic stem cells (hESCs), which do not express APLNR. Here we show that ELA signals in a paracrine fashion in hESCs to maintain self-renewal. ELA inhibition by CRISPR/Cas9-mediated deletion, shRNA, or neutralizing antibodies causes reduced hESC growth, cell death, and loss of pluripotency. Global phosphoproteomic and transcriptomic analyses of ELA-pulsed hESCs show that it activates PI3K/AKT/mTORC1 signaling required for cell survival. ELA promotes hESC cell-cycle progression and protein translation and blocks stress-induced apoptosis. INSULIN and ELA have partially overlapping functions in hESC medium, but only ELA can potentiate the TGFβ pathway to prime hESCs toward the endoderm lineage. We propose that ELA, acting through an alternate cell-surface receptor, is an endogenous secreted growth factor in human embryos and hESCs that promotes growth and pluripotency.

ELABELA: a novel hormone in cardiac development acting as a new endogenous ligand for the APJ receptor.

Human ELA consists of three exons on chromosome 4, which generates a transcript (AK092578) that is annotated as a non-coding RNA. However, Chng et al. [1] has found that this gene contains a conserved open reading frame predicted to express a conserved vertebrate protein of 54 amino acids (aa) consisting of a secretory signal and a mature 32-aa peptide, which was called as ELABELA (ELA). The sequence of human mature ELA is Gln-Arg-Pro-Val-AsnLeu-Thr-Met-Arg-Arg-Lys-Leu-Arg-Lys-His-Asn-Cys-LeuGln-Arg-Arg-Cys-Met-Pro-Leu-His-Ser-Arg-Val-Pro-Phe-Pro. Phylogenetic analysis revealed that the 32-aa mature peptide is evolutionarily highly conserved, with the last 13 residues being nearly invariant in all vertebrate species. ELA has also been previously reported to be highly expressed in undifferentiated human embryonic stem cells (hESCs) and be sharply down-regulated during differentiation [2]. Chng et al. [1] used an allelic series of zebrafish ELA mutants to show that ELA deficiency leads to severe defects in cardiac morphogenesis and often results in the complete absence of a heart. ELA mutant displayed specific defects in the mesendodermal lineage during gastrulation, as observed by the reduction of gata5 and sox17 expression. Taking together, these results suggested that ELA plays a role in the regulation of heart development. Whereas till now, no hormonal peptides has been reported to be involved in early development, particularly in the formation of the three embryonic germ layers. Chng et al. [1] first discovered an endogenous peptide hormone with potent embryonic signaling activity, which has great prospects in therapeutic applications such as heart repair and gene therapy in development. During embryogenesis, six key signaling pathways (Wnt [3], Bmp/Nodal [4], FGF/IGF [5], Notch [6], Hedgehog [7], and Hippo [8]) have been reported to be crucial for embryonic patterning. Chng et al. [1] tried to explain ELA’s functions in cardiac development by activating APJ receptor. Their reasons are as follows: i) ELA is concomitantly expressed with APJ (APLNR) before the onset of gastrulation. ii) The phenotypes of zebrafish ELA mutants stingingly resemble those of the APJ (APLNR) mutants specifically in cardiogenesis. iii) Extracellular ELA binds to APJ in a native cellular context. To our knowledge, APJ is a G protein-coupled receptor and its endogenous ligand is apelin. Apelin activates APJ receptor, and plays an important role in the physiological activities [9–11], especially in cardiovascular system [12]. However, a recent report has shown that APJ has some functions independent of apelin. Moreover, except apelin, APJ has also been activated by stretch in cardiac hypertrophy [13]. Researchers have tried to explore a second ligand for APJ. Chng et al. [1] stated that ELA, not apelin, is hence the long-sought-after alternative and earlier ligand for APJ, functioning in early cardiovascular development [1]. They demonstrated that the expression of ELA happens earlier than apelin and is concomitantly with APJ before the onset of gastrulation. Then, APJ depletion has different effects on cardiac morphogenesis compared with the depletion of apelin in zebrafish [14,15], frog embryos [15], and mice [16,17]. Whereas loss of ELA phenocopies the loss of APLNR (APJ gene). Based on these, they declared that ELA may be the second ligand for APJ in mediating endoderm differentiation and subsequent cardiogenesis. They first confirmed that a second ligand of APJ really exists in vivo, which forms another essential signaling axis in heart development. A further study supported this claim by reporting that a secreted peptide Toddler activates APJ signaling to promote the subsequent zebrafish gastrulation movements [18]. As we all know, apelin activated APJ signals through Gai by increasing the content of phosphorylated extracellular signal-regulated kinase (p-ERK). It was also reported that stretch may activate APJ receptor by recruiting b-arrestin. However, how ELA activates APJ in vivo is still unclear. ELA acts as an endogenous secreted peptide like apelin. It may have the same pathway as apelin in the activation of APJ. But more studies are needed. No matter what the signal will be, ELA’s function in cardiac development suggested that the ELA/APJ axis appears to be exclusive for endoderm development. Therefore, it opens a new field for future research. Acta Biochim Biophys Sin 2014, 46: 620–622 |a The Author 2014. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. DOI: 10.1093/abbs/gmu032. Advance Access Publication 14 May 2014

ELABELA: A Hormone Essential for Heart Development Signals via the Apelin Receptor

We report here the discovery and characterization ofa gene, ELABELA (ELA), encoding a conserved hormone of 32 amino acids. Present in human embryonic stem cells, ELA is expressed at the onset of zebrafish zygotic transcription and is ubiquitous in the naive ectodermal cells of the embryo. Using zinc-finger-nuclease-mediated gene inactivation in zebrafish, we created an allelic series of ela mutants. ela null embryos have impaired endoderm differentiation potential marked by reduced gata5 and sox17 expression. Loss of Ela causes embryos to develop with a rudimentary heart or no heart at all, surprisingly phenocopying the loss of the apelin receptor (aplnr), which we show serves as Ela's cognate G protein-coupled receptor. Our results reveal the existence of apeptide hormone, ELA, which, together with APLNR, forms an essential signaling axis for early cardiovascular development.