[Pyr1]-Apelin-13

[Pyr(1)]Apelin-13(1-12) Is a Biologically Active ACE2 Metabolite of the Endogenous Cardiovascular Peptide [Pyr(1)]Apelin-13.[Pubmed:28293165]

Front Neurosci. 2017 Feb 28;11:92.

Aims: Apelin is a predicted substrate for ACE2, a novel therapeutic target. Our aim was to demonstrate the endogenous presence of the putative ACE2 product [Pyr(1)]apelin-13(1-12) in human cardiovascular tissues and to confirm it retains significant biological activity for the apelin receptor in vitro and in vivo. The minimum active apelin fragment was also investigated. Methods and Results: [Pyr(1)]apelin-13 incubated with recombinant human ACE2 resulted in de novo generation of [Pyr(1)]apelin-13(1-12) identified by mass spectrometry. Endogenous [Pyr(1)]apelin-13(1-12) was detected by immunostaining in human heart and lung localized to the endothelium. Expression was undetectable in lung from patients with pulmonary arterial hypertension. In human heart [Pyr(1)]apelin-13(1-12) (pKi = 8.04 +/- 0.06) and apelin-13(F13A) (pKi = 8.07 +/- 0.24) competed with [(125)I]apelin-13 binding with nanomolar affinity, 4-fold lower than for [Pyr(1)]apelin-13 (pKi = 8.83 +/- 0.06) whereas apelin-17 exhibited highest affinity (pKi = 9.63 +/- 0.17). The rank order of potency of peptides to inhibit forskolin-stimulated cAMP was apelin-17 (pD2 = 10.31 +/- 0.28) > [Pyr(1)]apelin-13 (pD2 = 9.67 +/- 0.04) >/= apelin-13(F13A) (pD2 = 9.54 +/- 0.05) > [Pyr(1)]apelin-13(1-12) (pD2 = 9.30 +/- 0.06). The truncated peptide apelin-13(R10M) retained nanomolar potency (pD2 = 8.70 +/- 0.04) but shorter fragments exhibited low micromolar potency. In a beta-arrestin recruitment assay the rank order of potency was apelin-17 (pD2 = 10.26 +/- 0.09) >> [Pyr(1)]apelin-13 (pD2 = 8.43 +/- 0.08) > apelin-13(R10M) (pD2 = 8.26 +/- 0.17) > apelin-13(F13A) (pD2 = 7.98 +/- 0.04) >/= [Pyr(1)]apelin-13(1-12) (pD2 = 7.84 +/- 0.06) >> shorter fragments (pD2 < 6). [Pyr(1)]apelin-13(1-12) and apelin-13(F13A) contracted human saphenous vein with similar sub-nanomolar potencies and [Pyr(1)]apelin-13(1-12) was a potent inotrope in paced mouse right ventricle and human atria. [Pyr(1)]apelin-13(1-12) elicited a dose-dependent decrease in blood pressure in anesthetized rat and dose-dependent increase in forearm blood flow in human volunteers. Conclusions: We provide evidence that ACE2 cleaves [Pyr(1)]apelin-13 to [Pyr(1)]apelin-13(1-12) and this cleavage product is expressed in human cardiovascular tissues. We have demonstrated biological activity of [Pyr(1)]apelin-13(1-12) at the human and rodent apelin receptor in vitro and in vivo. Our data show that reported enhanced ACE2 activity in cardiovascular disease should not significantly compromise the beneficial effects of apelin based therapies for example in PAH.

[Effects of (Pyr(1))apelin-13 on the proliferation and activation of Jarkat T lymphocyte].[Pubmed:27916097]

Xi Bao Yu Fen Zi Mian Yi Xue Za Zhi. 2016 Dec;32(12):1641-1645.

Objective To investigate the effect of (Pyr(1))apelin-13 on the proliferation and activation of Jurkat T lymphocytes. Methods Jurkat T cells were treated by 0, 10, 50 nmol/L (Pyr(1))apelin-13 for 24 hours and cell proliferation ability was detected by CCK-8 assay. The effect of (Pyr(1))apelin-13 on the activation of Jurkat T lymphocytes with anti-CD3 and anti-CD28 antibodies was observed and the molecular mechanism was investigated. Quantitative real-time PCR was applied to detect the expressions of CD69, CD25, cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed death-1 (PD-1) mRNAs. Results The proliferation of Jurkat T cells was not affected by (Pyr(1)) apelin-13. However, (Pyr(1))apelin-13 increased the expressions of CD69 and CD25 and then activated Jurkat T lymphocytes. Furthermore, the expressions of CTLA-4 and PD-1 had no difference between activation group and (Pyr(1))apelin-13 group. Conclusion (Pyr(1))apelin-13 promotes Jurkat T lymphocyte activation by increasing the expressions of CD69 and CD25.

Vasopressin V1a receptors mediate the hypertensive effects of [Pyr(1) ]apelin-13 in the rat rostral ventrolateral medulla.[Pubmed:28255983]

J Physiol. 2017 Jun 1;595(11):3303-3318.

KEY POINTS: Dysfunctions in CNS regulation of arterial blood pressure lead to an increase in sympathetic nerve activity that participates in the pathogenesis of hypertension. The apelin-apelin receptor system affects arterial blood pressure homeostasis; however, the central mechanisms underlying apelin-mediated changes in sympathetic nerve activity and blood pressure have not been clarified. We explored the mechanisms involved in the regulation of [Pyr(1) ]apelin-13-mediated cardiovascular control within the rostral ventrolateral medulla (RVLM) using selective receptor antagonists. We show that [Pyr(1) ]apelin-13 acts as a modulating neurotransmitter in the normotensive RVLM to affect vascular tone through interaction with the vasopressin V1a receptor but that [Pyr(1) ]apelin-13-induced sympathoexcitation is independent of angiotensin II receptor type 1, oxytocin, ionotropic glutamate and GABAA receptors. Our data confirm a role for the apelin peptide system in cardiovascular regulation at the level of the RVLM and highlight that this system is a possible potential therapeutic target for the treatment of hypertension. ABSTRACT: Apelin is a ubiquitous peptide that can elevate arterial blood pressure (ABP) yet understanding of the mechanisms involved remain incomplete. Bilateral microinjection of [Pyr(1) ]apelin-13 into the rostral ventrolateral medulla (RVLM), a major source of sympathoexcitatory neurones, increases ABP and sympathetic nerve activity. We aimed to investigate the potential involvement of neurotransmitter systems through which the apelin pressor response may occur within the RVLM. Adult male Wistar rats were anaesthetized and ABP was monitored via a femoral arterial catheter. Bilateral RVLM microinjection of [Pyr(1) ]apelin-13 significantly increased ABP (9 +/- 1 mmHg) compared to saline (-1 +/- 2mmHg; P < 0.001), which was blocked by pretreatment with the apelin receptor antagonist, F13A (0 +/- 1 mmHg; P < 0.01). The rise in ABP was associated with an increase in the low frequency spectra of systolic BP (13.9 +/- 4.3% total power; P < 0.001), indicative of sympathetic vasomotor activation. The [Pyr(1) ]apelin-13-mediated pressor response and the increased low frequency spectra of systolic BP response were fully maintained despite RVLM pretreatment with the angiotensin II type 1 receptor antagonist losartan, the oxytocin receptor antagonist desGly-NH2 , d(CH2 )5 [D-Tyr(2) ,Thr(4) ]OVT, the ionotropic glutamate receptor antagonist kynurenate or the GABAA antagonist bicuculline (P > 0.05). By contrast, the [Pyr(1) ]apelin-13 induced pressor and sympathoexcitatory effects were abolished by pretreatment of the RVLM with the vasopressin V1a receptor antagonist, SR 49059 (-1 +/- 1 mmHg; 1.1 +/- 1.1% total power, respectively; P < 0.001). These findings suggest that the pressor action of [Pyr(1) ]apelin-13 in the RVLM of normotensive rats is not mediated via angiotensin II type 1 receptor, oxytocin, ionotropic glutamate or GABAA receptors but instead involves a close relationship with the neuropeptide modulator vasopressin.

Post-infarct treatment with [Pyr1]apelin-13 exerts anti-remodelling and anti-apoptotic effects in rats' hearts.[Pubmed:28181211]

Kardiol Pol. 2017;75(6):605-613.

BACKGROUND: Ischaemic heart disease is the main cause of mortality in the world. After myocardial infarction (MI) cardiomyocytes apoptosis and ventricular remodelling have occurred. Apelin is a peptide that has been shown to exert cardioprotective effects. AIM: The aim of this study was to investigate the anti-apoptotic and anti-remodelling effects of [Pyr(1)]apelin-13 in the rat model of post-MI. METHODS: Thirty-six male Wistar rats were randomly divided into three groups: (1) sham, (2) MI, and (3) MI treated with [Pyr(1)] apelin-13 (MI+Apel). MI animals were subjected to 30-min ligation of the left anterior descending coronary artery (LAD) and 14 days of reperfusion. Twenty-four hours after LAD ligation, [Pyr(1)]apelin-13 (10 nmol/kg/day, i.p.) was administered for five consecutive days. Hypertrophic parameters, left ventricular (LV) remodelling, and gene expression of Apel, apelin receptor (Apelr), Bax, caspase-3 (Casp-3), and Bcl-2 by real-time polymerase chain reaction and cardiomyocytes apoptosis by TUNEL immunostaining were assessed on day 14 post-MI. RESULTS: Post-infarct treatment with [Pyr(1)]apelin-13 improved myocardial hypertrophic and LV remodelling parameters and led to a significant increase in the expression of Apel, Apelr, and Bcl-2, and a decrease in the expression of Bax and Casp-3. Furthermore, treatment with [Pyr(1)]apelin-13 decreased cardiomyocyte apoptosis. CONCLUSIONS: [Pyr(1)]apelin-13 has anti-hypertrophic, anti-remodelling, and anti-apoptotic effects via overexpression of Apel, Apelr, and Bcl-2 and reduces gene expression of Bax and Casp-3 in the infarcted myocardium, which can in turn lead to repair myocardium.

Central and peripheral cardiovascular actions of apelin in conscious rats.[Pubmed:15582714]

Regul Pept. 2005 Feb 15;125(1-3):55-9.

APJ was cloned as an orphan G protein-coupled receptor and shares a close identity with angiotensin II type 1 receptor (AT1R). Apelin is a peptide that has recently been identified as an endogenous ligand of the APJ. Apelin and APJ mRNA are expressed in peripheral tissue and the central nervous system. However, little is known about the effects of apelin in cardiovascular regulation. To examine the central and peripheral role of apelin, we injected the active fragment of apelin [(Pyr1)apelin-13] intracerebroventricularly (ICV, 5 and 20 nmol, n=6) or intravenously (IV, 20 and 50 nmol, n=4 or 5) in conscious rats. ICV injection of (Pyr1)apelin-13 dose-dependently increased mean arterial pressure (MAP) and heart rate (HR) (19+/-3 mm Hg and 162+/-26 bpm at 20 nmol). Pretreatment with ICV injection of the AT1R antagonist (CV-11974, 20 nmol) did not alter the apelin-induced increase in MAP and HR. IV injection of (Pyr1)apelin-13 also dose-dependently increased MAP and HR (13+/-2 mm Hg and 103+/-18 bpm at 50 nmol); however, the peripheral effects of apelin were relatively weak compared to its central effects. Expression of c-fos in the paraventricular nucleus (PVN) of hypothalamus was increased in the rat that received ICV injection of (Pyr1)apelin-13 but not in the rat that received IV injection of (Pyr1)apelin-13. These results suggest that apelin plays a role in both central and peripheral cardiovascular regulation in conscious rats, and that the cardiovascular effects of apelin are not mediated by the AT1R.

Emerging roles of apelin in biology and medicine.[Pubmed:15907343]

Pharmacol Ther. 2005 Aug;107(2):198-211.

The family of apelin peptides is derived from a single gene and activates the 7-transmembrane G-protein-coupled receptor (GPCR) APJ. Apelins have been shown to be involved in the regulation of cardiovascular function and fluid homeostasis and interestingly represent substrates for ACE2, a carboxypeptidase recently described as a novel key enzyme in the renin-angiotensin-aldosterone system (RAS). APJ has further been reported to be a coreceptor for the infection of CD4-positive cells with HIV in the central nervous system (CNS). Apelin-36 and shorter C-terminal sequences have different potencies and efficacies in regulating these functions. Shorter sequences, especially (Pyr(1))apelin-13, are potent regulators of cardiovascular function, while longer peptides such as apelin-36 are more effective in inhibiting human immunodeficiency virus (HIV) infection by blocking the HIV coreceptor APJ. The pyroglutamate modification characteristic of the short apelin peptide (Pyr(1))apelin-13 indicates paramount biological importance of this peptide. The aim of this review is to compile conclusive evidence for the involvement of apelin/APJ in the regulation of cardiovascular function and HIV pathology, emphasizing the properties of this receptor system that may make it a successful future drug target.

[(125)I]-(Pyr(1))Apelin-13 is a novel radioligand for localizing the APJ orphan receptor in human and rat tissues with evidence for a vasoconstrictor role in man.[Pubmed:11250876]

Br J Pharmacol. 2001 Mar;132(6):1255-60.

1. We have determined the binding characteristics of [(125)I]-(Pyr(1))Apelin-13, a putative ligand for the APJ orphan receptor in human cardiovascular and rat tissue and investigated the functional properties of (Pyr(1))Apelin-13 in human saphenous vein. 2. The binding of [(125)I]-(Pyr(1))Apelin-13 to sections of human heart tissue was time dependent and rapid at 23 degrees C. Data were fitted to a single site model with an association rate constant (k(obs)) of 0.115 min(-1). [(125)I]-(Pyr(1))Apelin-13 also dissociated from a single site with a dissociation rate constant of 0.0105 min(-1). 3. In saturation binding experiments [(125)I]-(Pyr(1))Apelin-13 bound to human left ventricle with a K(D) value of 0.35+/-0.08 nM, B(max) of 4.3+/-0.9 fmol mg(-1) protein with a Hill slope of 0.97+/-0.04 and to the right atria with a K(D) of 0.33+/-0.09 nM, B(max) of 3.1+/-0.6 fmol mg(-1) protein and a Hill slope of 0.93+/-0.05. 4. [(125)I]-(Pyr(1))Apelin-13 binding sites were localized using autoradiography to human cardiovascular tissue, including coronary artery, aorta and saphenous vein grafts. In rat tissue a high density of receptors were localized to the molecular layer of the rat cerebellum, rat lung, rat heart and low levels in the rat kidney cortex. 2. (Pyr(1))Apelin-13 potently contracted human saphenous vein with a pD(2) value of 8.4+/-0.2 (n=8). The maximum response elicited by the peptide was 22.6+/-6% of 100 mM KCl. 6. We provide the first evidence of APJ receptor expression, relative densities and functional properties of (Pyr(1))Apelin-13 in human cardiovascular tissue.