Effects of apelin on the cardiovascular system

A promoter polymorphism in APJ gene is significantly associated with blood pressure changes and hypertension risk in Chinese women

The aim of this study was to interrogate the gender-specific association of 5 well-defined polymorphisms in apelin/APJ system with both blood pressure changes and hypertension risk in a northeastern Chinese population. This is a population-based case-control study, including 650 hypertensive patients and 645 normotensive controls. Data were analyzed by STATA and Haplo.Stats. The genotype distributions of 5 study polymorphisms were in Hardy-Weinberg equilibrium in both genders. The rs7119375 and rs10501367 were completely linked. The genotypes (P = 0.001) and alleles (P < 0.001) of rs7119375 differed significantly between patients and controls in women. Carriers of rs7119375-AA genotype had significant higher systolic blood pressure (SBP) than carriers of rs7119375-GG genotype in both patients and controls of female gender (P < 0.01). Moreover, carriers of rs7119375-A allele were 1.80 times more likely to develop hypertension relative to carriers of rs7119375-GG genotype after adjusting for age, body mass index and glucose (odds ratio: 1.80; 95% confidence interval: 1.03–3.16; P = 0.040). Further allele combination analysis supported the leading contribution of rs7119375 to hypertension risk. Our findings demonstrated that the mutation of promoter polymorphism rs7119375 in APJ gene was significantly associated with elevated SBP and increased hypertension risk in Chinese women.

Effects of apelin on retinal microglial cells in a rat model of oxygen-induced retinopathy of prematurity

This study explores the effects of apelin on retinal microglial cells in rat models of oxygen-induced retinopathy of prematurity (ROP). Totally, 274 rats were selected for establishing oxygen-induced retinopathy (OIR) models, and 92 healthy rats for control group. OIR rats were assigned into OIR, 10^-5  g/L apelin, 10^-4  g/L apelin, and 10^-3  g/L apelin groups. Immunohistochemistry was employed to determine morphology of microglial cells and cell number. CDllb, ionized calcium-binding adapter molecule 1 (IBA-1), TNF-α, and iNOS mRNA and protein expressions were identified using RT-qPCR and Western blotting, respectively. ELISA was employed to determine the levels of VEGF and glial fibrillary acidic protein (GFAP). The amoeboid microglial cells were found in the OIR and 10^-3  g/L apelin groups, while bipolar microglial cells were found in the normal control, 10^-5  g/L apelin and 10^-4  g/L apelin groups. In the 1, 2, 3, and 4th week after apelin treatment, there were significantly decreased bipolar microglial cells, lower mRNA and protein expressions of CDllb, IBA-1, TNF-α and iNOS, and the levels of VEGF and GFAP in the 10^-4  g/L apelin group than in the OIR, 10^-3  g/L apelin and 10^-5  g/L apelin groups. The differences between the normal control and 10^-4  g/L apelin groups are not significant. Compared with the OIR group, the 10^-5  g/L apelin and 10^-3  g/L apelin groups presented decreased microglial cells and mRNA and protein expressions of CDllb, IBA-1, TNF-α, and iNOS. Appropriate concentration of apelin may reduce retinal microglial cells in a rat model of oxygen-induced ROP.

Apelin13/APJ promotes proliferation of colon carcinoma by activating Notch3 signaling pathway

Background

The link between Apelin (APL)/APL receptor (APJ) and Jagged (JAG)/Notch signaling pathways in colorectal cancer (CRC) has been poorly investigated. APL/APJ system, a potent angiogenic factor, is up-regulated in a variety of cancers. It contributes to tumor angiogenesis, and correlates with progression of malignancy. JAG/Notch signaling also contributes to progression, proliferation and metastasis of multiple cancers, including CRC. Here we tested the hypothesis that APL/APJ system promotes CRC proliferation by up-regulating Notch3, thus allowing further binding of JAG1 to Notch3.

Materials and Methods

We used a variety of methods including Western blot, RT-qPCR, gene silencing, ELISA, immunofluorescence staining, to investigate the interaction between APL/APJ system and Notch3 signaling pathway in both surgically-resected specimens and CRC cell line LS180.

Results

We show that the expression of APL13, APJ, and Notch3 is elevated in CRC. We further demonstrate that APL13 can be secreted into culture media of LS180 cells, suggesting the existence of autocrine loop in CRC. Moreover, we found that APL13 stimulated expression of Notch3. Finally, we found that inhibition of either APJ or Notch3 prevents proliferation of LS180 cells.

Conclusions

Our results suggest that APL13/APJ and JAG1/Notch3 signaling pathways are linked in CRC. These findings provide a new direction to the efforts targeting effective therapeutic and management approaches in the treatment of CRC.

Load-dependent effects of apelin on murine cardiomyocytes

The apelin peptide is described as one of the most potent inotropic agents, produced endogenously in a wide range of cells, including cardiomyocytes. Despite positive effects on cardiac contractility in multicellular preparations, as well as indications of cardio-protective actions in several diseases, its effects and mechanisms of action at the cellular level are incompletely understood.

Here, we report apelin effects on dynamic mechanical characteristics of single ventricular cardiomyocytes, isolated from mouse models (control, apelin-deficient [Apelin-KO], apelin-receptor KO mouse [APJ-KO]), and rat. Dynamic changes in maximal velocity of cell shortening and relaxation were monitored. In addition, more traditional indicators of inotropic effects, such as maximum shortening (in mechanically unloaded cells) or peak force development (in auxotonic contracting cells, preloaded using the carbon fibre technique) were studied.

The key finding is that, using Apelin-KO cardiomyocytes exposed to different preloads with the 2-carbon fibre technique, we observe a lowering of the slope of the end-diastolic stress-length relation in response to 10 nM apelin, an effect that is preload-dependent. This suggests a positive lusitropic effect of apelin, which could explain earlier counter-intuitive findings on an apelin-induced increase in contractility occurring without matching rise in oxygen consumption.

Prospective evaluation of the diagnostic value of plasma apelin 12 levels for differentiating patients with moyamoya and intracranial atherosclerotic diseases

Patients with moyamoya disease (MMD) or intracranial atherosclerotic disease (ICAD) experience similar cerebral ischaemic events. However, MMD patients show greater angiogenesis and arteriogenesis, which play crucial roles in collateral circulation development to enhance clinical prognosis and outcome. Apelins have been associated with angiogenesis and arteriogenesis. Therefore, the aim of the present study was to determine whether apelin levels were higher in patients with MMD than in patients with ICAD or in healthy controls. We compared plasma apelin levels in 29 patients with MMD, 82 patients with ICAD, and 25 healthy participants. Twelve-hour fasting blood samples were collected and analysed using commercially available kits. Univariate analyses indicated that compared with the ICAD and healthy control groups, the MMD group had higher apelin-12, apelin-13, apelin-36, and nitric oxide levels. Binary logistic regression analyses further showed that the plasma apelin-12 level was substantially higher in MMD patients than in ICAD patients. Patients with MMD were also differentiated from patients with ICAD by their mean ages, with the former being younger. Therefore, the plasma apelin-12 level is a potential diagnostic marker for differentiating MMD and ICAD and may provide a treatment strategy for enhancing collateral circulation development and clinical prognosis and outcome.

Apelin/APJ system: A novel promising therapy target for pathological angiogenesis

Apelin is the endogenous ligand of the G protein-coupled receptor APJ. Both Apelin and APJ receptor are widely distributed in various tissues such as heart, brain, limbs, retina and liver. Recent research indicates that the Apelin/APJ system plays an important role in pathological angiogenesis which is a progress of new blood branches developing from preexisting vessels via sprouting. In this paper, we review the important role of the Apelin/APJ system in pathological angiogenesis. The Apelin/APJ system promotes angiogenesis in myocardial infarction, ischemic stroke, critical limb ischemia, tumor, retinal angiogenesis diseases, cirrhosis, obesity, diabetes and other related diseases. Furthermore, we illustrate the detailed mechanism of pathological angiogenesis induced by the Apelin/APJ system. In conclusion, the Apelin/APJ system would be a promising therapeutic target for angiogenesis-related diseases.

Development of original metabolically stable apelin-17 analogs with diuretic and cardiovascular effects

Apelin, a (neuro)vasoactive peptide, plays a prominent role in controlling cardiovascular functions and water balance. Because the in vivo apelin half-life is in the minute range, we aimed to identify metabolically stable apelin-17 (K17F) analogs. We generated P92 by classic chemical substitutions and LIT01-196 by original addition of a fluorocarbon chain to the N terminus of K17F. Both analogs were much more stable in plasma (half-life >24 h for LIT01-196) than K17F (4.6 min). Analogs displayed a subnanomolar affinity for the apelin receptor and behaved as full agonists with regard to cAMP production, ERK phosphorylation, and apelin receptor internalization. Ex vivo, these compounds induced vasorelaxation of rat aortas and glomerular arterioles, respectively, precontracted with norepinephrine and angiotensin II, and increased cardiac contractility. In vivo, after intracerebroventricular administration in water-deprived mice, P92 and LIT01-196 were 6 and 160 times, respectively, more efficient at inhibiting systemic vasopressin release than K17F. Administered intravenously (nmol/kg range) in normotensive rats, these analogs potently increased urine output and induced a profound and sustained decrease in arterial blood pressure. In summary, these new compounds, which favor diuresis and improve cardiac contractility while reducing vascular resistances, represent promising candidates for the treatment of heart failure and water retention/hyponatremic disorders.-Gerbier, R., Alvear-Perez, R., Margathe, J.-F., Flahault, A., Couvineau, P., Gao, J., De Mota, N., Dabire, H., Li, B., Ceraudo, E., Hus-Citharel, A., Esteoulle, L., Bisoo, C., Hibert, M., Berdeaux, A., Iturrioz, X., Bonnet, D., Llorens-Cortes, C. Development of original metabolically stable apelin-17 analogs with diuretic and cardiovascular effects.

[A preliminary investigation of relationship between serum apelin level and pulmonary artery pressure in children with congenital heart disease]

OBJECTIVE

To preliminarily investigate the relationship between serum apelin level and pulmonary artery pressure in children with congenital heart disease.

METHODS

One hundred and twenty-six children with congenital heart disease undergoing surgical treatment were enrolled as subjects. The serum level of apelin was determined before surgery and at 7 days after surgery. The ratio of pulmonary artery systolic pressure to aortic systolic pressure (Pp/Ps) was calculated before extracorporeal circulation. According to the Pp/Ps value, patients were classified into non-pulmonary arterial hypertension (PAH) group, mild PAH group, moderate PAH group, and severe PAH group. Pulmonary artery mean pressure was estimated by echocardiography at 7 days after surgery.

RESULTS

The non-PAH group had the highest serum level of apelin before and after surgery, followed by the mild PAH group, moderate PAH group, and severe PAH group (P<0.05). All groups had significantly increased serum levels of apelin at 7 days after surgery (P<0.05). The serum level of apelin was negatively correlated with pulmonary artery pressure before surgery (r=-0.51, P<0.05) and at 7 days after surgery (r=-0.54, P<0.05).

CONCLUSIONS

The decrease in serum apelin level is associated with the development of pulmonary hypertension in children with congenital heart disease. The significance of serum apelin in predicting the development and degree of pulmonary hypertension in children with congenital heart disease deserves further studies.

Apelin induces vascular smooth muscle cells migration via a PI3K/Akt/FoxO3a/MMP-2 pathway

Apelin is an adipokine that has a critical role in the development of atherosclerosis, which may offer potential for therapy. Because migration of vascular smooth muscle cells (VSMCs) is a key event in the development of atherosclerosis, understanding its effect on the atherosclerotic vasculature is needed. Here we investigated the effect of apelin on VSMC migration and the possible signaling mechanism. In cultured rat VSMCs, apelin dose- and time-dependently promoted VSMC migration. Apelin increased the phosphorylation of Akt, whereas LY294002, an inhibitor of phosphatidylinositol 3-kinase (PI3K), and an Akt1/2 kinase inhibitor blocked the apelin-induced VSMC migration. Apelin dose-dependently induced phosphorylation of Forkhead box O3a (FoxO3a) and promoted its translocation from the nucleus to cytoplasm, which were blocked by LY294002 and Akt1/2 kinase inhibitor. Furthermore, apelin increased matrix metalloproteinase 2 (MMP-2) expression and gelatinolytic activity. Overexpression of a constitutively active, phosphorylation-resistant mutant, TM-FoxO3a, in VSMCs abrogated the effect of apelin on MMP-2 expression and VSMC migration. ARP101, an inhibitor of MMP-2, suppressed apelin-induced VSMC migration. Moreover, the levels of apelin, phosphorylated Akt, FoxO3a, and MMP-2 were higher in human carotid-artery atherosclerotic plaque than in adjacent normal vessels. We demonstrate that PI3K/Akt/FoxO3a signaling may be involved in apelin inducing VSMC migration. Phosphorylation of FoxO3a plays a central role in mediating the apelin-induced MMP-2 activation and VSMC migration.

Microglia-Induced Maladaptive Plasticity Can Be Modulated by Neuropeptides In Vivo

Microglia-induced maladaptive plasticity is being recognized as a major cause of deleterious self-sustaining pathological processes that occur in neurodegenerative and neuroinflammatory diseases. Microglia, the primary homeostatic guardian of the central nervous system, exert critical functions both during development, in neural circuit reshaping, and during adult life, in the brain physiological and pathological surveillance. This delicate critical role can be disrupted by neural, but also peripheral, noxious stimuli that can prime microglia to become overreactive to a second noxious stimulus or worsen underlying pathological processes. Among regulators of microglia, neuropeptides can play a major role. Their receptors are widely expressed in microglial cells and neuropeptide challenge can potently influence microglial activity in vitro. More relevantly, this regulator activity has been assessed also in vivo, in experimental models of brain diseases. Neuropeptide action in the central nervous system has been associated with beneficial effects in neurodegenerative and neuroinflammatory pathological experimental models. This review describes some of the mechanisms of the microglia maladaptive plasticity in vivo and how neuropeptide activity can represent a useful therapeutical target in a variety of human brain pathologies.