Elabela is a newly discovered peptide in recent years.It is the endogenous ligand of Apelin receptor(APJ)and plays an important role in embryonic development and adult organs.Elabela-APJ axis is closely related to organ fibrosis.Elabela can protect the functions of heart and kidney by antagonizing renin-angiotensin system and regulating blood pressure.In addition,it can prevent kidney and heart fibrosis by down-regulating the expression of fibrosis and inflammatory factors.However,there is a positive correlation between the level of Elabela and the degree of liver fibrosis,suggesting that Elabela may play a role in promoting liver fibrosis.This review aims to explore the role of Elabela-APJ axis in renal fibrosis,cardiac fibrosis,and liver fibrosis,and to provide a new therapeutic target for organ fibrosis.
Apelin ; Apelin Receptors ; Blood Pressure ; Female ; Fibrosis ; Humans ; Peptide Hormones ; Pregnancy

OBJECTIVETo study the effects of swimming exercise on the expression of apelin and its receptor (APJ) system in pulmonary tissues of rats with pulmonary hypertension induced by hypoxia.

METHODSForty-five male SD rats were randomly divided into control group, hypoxia group (seven-week) and swimming group (four-week swimming group after three-week hypoxia). The animal model of hypoxic pulmonary hypertension was established by exposing the rats to isobaric hypoxic chamber (8 h/d, 6 d/w). The rats of swimming group swam 60 min/day, 7 d/week for 4 weeks after three-week hypoxia. The mean pulmonary arterial pressure (mPAP) and the mean carotid arterial pressure (mCAP) were measured by either right or left cardiac catheterization, and the weight ratio of right ventricule/left ventricle plus septum [RV/(LV + S)] were calculated. The Masson's trichrome stained lung specimens were used by light microscope to examine the vessel wall area/total area (WA/TA), vessel cavity area/total area (CA/TA) and media thickness of pulmonary arterioles (PAMT). Meanwhile, apelin/ APJ expressions were determined by Western blot and immunohistochemistry.

RESULTS(1) mPAP and RV/(LV + S) of hypoxia group were higher than those of control group by 73.6% and 31.2% (P < 0.01), and mPAP and RV/(LV + S) of swimming group were lower than those of hypoxia group by 21.1%and 8.9 % (P < 0.05), respectively. (2) Masson's trichrome staining revealed that WA/TA and PAMT of hypoxia group were higher than those of control group by 70.8% and 102%. However, WA/TA and PAMT of swimming group were lower than those of hypoxia group by 24.8% and 40.1% (all P < 0.01), respectively. CA/TA of hypoxia group was lower than that of control group by 15.1%, and CA/TA of swimming group was lower than that of hypoxia group by 10.3% (all P < 0.01). (3) Compared with control group, hypoxia group showed up-regulated apelin expression and down-regulated APJ expression in pulmonary tissues (all P < 0.01). Compared with hypoxia group, swimming group showed decreased apelin expression and elevated APJ expression in pulmonary tissues (all P < 0.01). (4) Apelin localized mainly in intracytoplasm of inflammatory cell and tunica adventitia of vessel, and APJ were in vascular intima and tunica externa and plasmalemma of inflammatory cell.

CONCLUSIONThe improving effect of swimming exercise on hypoxic pulmonary hypertension in rats could be mediated by regulating the pulmonary apelin/APJ system.

Animals ; Apelin ; Apelin Receptors ; Hypertension, Pulmonary ; metabolism ; Hypoxia ; metabolism ; Intercellular Signaling Peptides and Proteins ; metabolism ; Male ; Physical Conditioning, Animal ; Rats ; Rats, Sprague-Dawley ; Receptors, G-Protein-Coupled ; metabolism ; Swimming

OBJECTIVETo explore the role of bromodomain and extra terminal (BET) bromodomain in hematopoietic differentiation from human enbryonic stem cells (hESC).

METHODSThe effect of BET hematopoietic inhibitor I-BET151 on hematopoietic differentiation from hESC was detected by using a monolayer hematopoietic defferentiation model, immunofluorescence, flow cytometry and real-time PCR; moreover the role of I-BET151 in process of hematopoietic differentiation was explored by adding I-BET151 in different differentiation stages.

RESULTSThe analysis results of immunofluorescence, flow cytometry and real-time PCR showed that I-BET 151 significantly inhibited the generation of CD43 positive hematopoietic stem and progenitor cells (HSPCs). It was found that the addition of I-BET 151 in different stages, including APLNR lateral plate mesoderm production, CD34CD31 hemogenic endothelium (HEP) generation and endothelial-to-hematopoietic transition, significantly suppressed the generation of CD43 positive hematopoietic progenitor cells.

CONCLUSIONI-BET 151 inhibites hematopoietic differentiation from hESCs at several stages, suggesting that the BET bromodomain plays important roles in multiple stages of hematopoietic differentiation from hESCs.

Apelin Receptors ; Cell Differentiation ; Flow Cytometry ; Hemangioblasts ; Hematopoietic Stem Cells ; Human Embryonic Stem Cells ; Humans

OBJECTIVETo observe the change of apelin and its receptor (APJ) in the lung tissue of rats with pulmonary hypertension induced by monocrotaline and to explore its significance.

METHODSTwenty-five male SD rats were randomly divided into control group (n = 10) and monocrotaline group (n = 15). On the twenty-first day after the rats were intraperitoneally injected 60 mg/kg monocrotaline for monocrotaline group or equal volume vehicle for control group, the mean pulmonary artery pressure was measured by right heart catheterization. Histopathological study of lung tissue was done with hematoxylin-eosin (HE) and Masson's trichrome staining. The concentration of apelin in the plasma was measured by radioimmunoassay. The expressions of apelin/APJ proteins and genes in lung tissue were measured respectively by Western blot and reverse transcription polymerase chain reaction (RT-PCR).

RESULTSThe mean pulmonary arterial pressure, right ventricular hypertrophy, pulmonary vascular remodeling index, content of apelin protein in lung tissue of monocrotaline group were higher than those in control group. APJ protein and gene expression in monocrotaline group were significantly lower than those in control group (P < 0.01, P < 0.05), but apelin gene expression in the lung tissue between the two groups had no significant difference.

CONCLUSIONEndogenous apelin/APJ dysfunction may play an important role in the development of pulmonary hypertension induced by monocrotaline.

Animals ; Apelin ; Apelin Receptors ; Hypertension, Pulmonary ; chemically induced ; metabolism ; Intercellular Signaling Peptides and Proteins ; metabolism ; Lung ; metabolism ; Male ; Monocrotaline ; adverse effects ; Rats ; Rats, Sprague-Dawley ; Receptors, G-Protein-Coupled ; metabolism

OBJECTIVETo investigate whether ginsenoside-Rb1 (Gs-Rb1) inhibits the apoptosis of hypoxia cardiomyocytes by up-regulating apelin-APJ system and whether the system is affected by hypoxia-induced factor 1α (Hif-1α).

METHODSNeonatal rat cardiomyocytes were randomly divided into 6 groups: a control group, a simple CoCl group, a simple Gs-Rb1 group, a CoCl and Gs-Rb1 hypoxia group, a CoCl and 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) group, a CoCl and YC-1 group and a Gs-Rb1 group, in which YC-1 inhibits the synthesis and accelerates the degradation of Hif-1a. The concentration of CoCl, Gs-Rb1 and YC-1 was 500 μmol/L, 200 μmol/L and 5 μmol/L, respectively; the apoptosis ratio was analyzed with a flow cytometer; and apelin, APJ and Hif-1α were assayed with immunocytochemistry, Western blot assays and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS(1) The anti-apoptosis effect of Gs-Rb1 on hypoxia cardiomyocytes was significantly inhibited by YC-1; (2) Hypoxia significantly up-graded the expression of mRNA and protein of apelin; this effect was further reinforced by Gs-Rb1 and significantly inhibited by YC-1; (3) Gs-Rb1 further strengthened the expression of APJ mRNA and APJ proteins once hypoxia occurred, which was significantly inhibited by YC-1; (4) Gs-Rb1 significantly increased the expression of Hif-1α, which was completely abolished by YC-1; (5) There was a negative relationship between AR and apelin (or APJ, including mRNA and protein), a positive correlation between apelin (or APJ) protein and Hif-1a protein, in hypoxia cardiomyocytes.

CONCLUSIONThe apelin-APJ system plays an important role in the anti-apoptosis effect of Gs-Rb1 on hypoxia neonatal cardiomyocytes, which was partly adjusted by Hif-1α.

Animals ; Animals, Newborn ; Apelin ; Apelin Receptors ; Cell Hypoxia ; drug effects ; Ginsenosides ; pharmacology ; Hypoxia-Inducible Factor 1, alpha Subunit ; metabolism ; Immunohistochemistry ; Intercellular Signaling Peptides and Proteins ; genetics ; metabolism ; Myocytes, Cardiac ; cytology ; drug effects ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats, Wistar ; Receptors, G-Protein-Coupled ; metabolism

OBJECTIVETo explore the effect of puerarin combined with felodipine on the mRNA and protein expression of apelin and APJ in renal tissue of renovascular hypertensive rat.

METHODSixty-two Sprague-Dawley rats were used, of which 8 rats were randomly chosen as sham-operation group. The remaining rats were made for the rat model with renovascular hypertension. The renovascular hypertensive rats were randomly divided into 5 groups as follows: 4 groups which were treated with felodipine (0.8 mg x kg(-1) x d(-1)), puerarin (50 mg x kg(-1) x d(-1)), puerarin combined with felodipine (puerarin 25 mg x kg(-1) x d(-1) + felodipine 0.4 mg x kg(-1) x d(-1)) or captopril combined with felodipine (captopril 15 mg x kg(-1) x d(-1) x felodipine 0.4 mg x kg(-1) x d(-1)), and 1 group which was treated with distilled water. Drugs or distilled water were administered for 8 weeks. The expression of apelin and APJ mRNA and protein in ischemic and non-ischemic kidneys was assessed by RT-PCR or Western blot.

RESULTCompared with sham-operation group, the expression of apelin mRNA and protein in ischemic and non-ischemic kidneys in model group was increased significantly (P < 0.01); the expression of APJ mRNA and protein in ischemic kidneys had no significance, while that in non-ischemic kidneys was decreased (P < 0. 01). Compared with model group, the expression of apelin mRNA and protein in ischemic and non-ischemic kidneys was decreased significantly in all drug-treated groups (P < 0.01); while that of APJ mRNA and protein in non-ischemic kidneys was upregulated (P < 0.01). Compared with felodipine group, the expression of apelin mRNA and protein in ischemic and non-ischemic kidneys was decreased (P < 0.01 or P < 0.05) in the group treated with both puerarin and felodipine; and the expression of APJ mRNA and protein in ischemic kidneys did not reach significant level, however, that was upregulated in non-ischemic kidneys (P < 0.01 or P < 0.05).

CONCLUSIONPuerarin downregulates the expression of apelin mRNA and protein in ischemic and non-ischemic kidneys, and upregulates that of APJ mRNA and protein in non-ischemic kidneys. Combination of puerarin and felodipine enhances the above-mentioned effects and shows no significant difference versus the combination of felodipine and captopril. The results suggest that puerarin regulates blood pressure and protects target organ through apelin/APJ pathway and that puerarin has synergetic effects with CCB.

Animals ; Antihypertensive Agents ; pharmacology ; Apelin ; Apelin Receptors ; Blotting, Western ; Captopril ; pharmacology ; Drug Synergism ; Felodipine ; pharmacology ; Gene Expression ; drug effects ; Hypertension, Renovascular ; genetics ; metabolism ; Intercellular Signaling Peptides and Proteins ; genetics ; metabolism ; Ischemia ; Isoflavones ; pharmacology ; Kidney ; blood supply ; drug effects ; metabolism ; Male ; RNA, Messenger ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, G-Protein-Coupled ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Vasodilator Agents ; pharmacology

OBJECTIVETo examine the change of puerarin on the expression of apelin and its receptor of the two-kidney, one-clip (2K1C) rats.

METHODTirty male Sprague-Dawley rats were randomly divided into normal control group (C), model group (M) and puerarin group (P). The mean of carotid arterial pressure (mCAP), mean of left ventricular end diastolic pressure (LVEDP), and the weight ratio of left ventricular mass (left ventricle plus septum) to bodyweight (LVM/BW) were measured to evaluate the model of 2K1C renal hypertension. The concentrations of apelin in the plasma and left ventricle (LV) were measured with radioimmunoassay. Apelin mRNA and APJ mRNA expressed in the LV were examined by reverse transcription-polymerase chain reaction (RT-PCR). The peptides of apelin and APJ expressed in the LV were detected with immunohistochemistry (IHC).

RESULTCompared with C group, the mCAP, LVEDP and LVM/BW of M group were higher 36.58%, 333.8% and 20.24%, respectively (P<0.05, P<0.01, P<0.01). Compared with M group, LVEDP and LVM/BW of P group were lower 65.24% and 13.12%, respectively (both P<0.05). However mCAP was of no significant difference between these two groups. The levels of apelin-36 in the plasma and LV of M group were respectively higher 18.56% and 207.38% than those of C group (both P<0.05), while ones of P group were lower 24.21% and 49.40% than those of M group (both P<0.05). The expressions of apelin mRNA and APJ mRNA at left ventricle tissues of 2K1C rats were higher 77.66% and 119.00% (both P<0.05) than those of C group. The ones of P group were lower 27.40% and 45.66% than those of M group (both P<0.01). The IHC results indicate that the expressions of apelin and APJ peptides at left ventricle tissues of 2K1C rats were higher 129.51% and 154.1% (both P<0.01) than those of C group, respectively. Whereas the ones of P group were lower 65.36% and 62.87% than those of M group (both P<0.01).

CONCLUSIONThrough regulating apelin/APJ system puerarin has protective effect on the development of left ventricular hypertrophy by renal hypertension.

Animals ; Apelin ; Apelin Receptors ; Carrier Proteins ; genetics ; metabolism ; Gene Expression ; drug effects ; Hypertension, Renal ; drug therapy ; metabolism ; physiopathology ; Hypertrophy, Left Ventricular ; prevention & control ; Immunohistochemistry ; Intercellular Signaling Peptides and Proteins ; Isoflavones ; therapeutic use ; Male ; Radioimmunoassay ; Rats ; Rats, Sprague-Dawley ; Receptors, G-Protein-Coupled ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction

BACKGROUNDApoptosis is a major cause of ischemic heart dysfunction. Apelin, the endogenous ligand for the G-protein-coupled APJ receptor, has been reported to exert cardioprotective effects during myocardial injury. The aim of this study was to investigate the effects of apelin on apoptosis of rat cardiomyocytes induced by glucose deprivation (GD) and study the related signaling pathway.

METHODSApelin and APJ mRNA expression were determined by RT-PCR in neonatal rat cardiomyocytes during different durations of GD. Cardiomyocyte apoptosis was detected by annexin V-FITC/propidium iodide (PI) staining after GD for 12 hours with or without apelin-13 (10 and 100 nmol/L) pretreatment. Protein levels of Akt and the mammalian target of rapamycin (mTOR) as well as cell apoptosis were detected in the presence or absence of LY294002 (a phosphatidylinositol 3-kinases (PI3K) inhibitor) or rapamycin (a mTOR inhibitor).

RESULTSApelin mRNA expression was up-regulated when cardiomyocytes were exposed to GD for 6, 12, 18, and 24 hours compared with the base level (P > 0.05, P < 0.01, P < 0.01, P < 0.01). However, when cardiomyocytes were exposed to GD for up to 36 hours, apelin mRNA expression was 17% lower than the base level (P < 0.05). APJ mRNA expression paralleled that of apelin. Apelin-13 pretreatment at 100 nmol/L significantly inhibited GD-induced cardiomyocyte apoptosis (P < 0.05) and increased Akt and mTOR phosphorylation (P < 0.01, P < 0.01). At the same time apelin-13 (100 nmol/L) up-regulated Bcl-2 protein expression and down-regulated Bax and cleaved caspase-3 expression (P < 0.01, P < 0.05, P < 0.05). The anti-apoptotic effect of apelin-13 was blocked by LY294002 (P < 0.01) but not by rapamycin.

CONCLUSIONSThe endogenous apelin-APJ system is compensatorily up-regulated and ultimately down-regulated following sustained myocardial ischemia. Apelin protects against ischemic cardiomyocyte apoptosis via activation of the PI3K/Akt pathway.

Animals ; Apelin ; Apelin Receptors ; Apoptosis ; Carrier Proteins ; genetics ; physiology ; Caspase 3 ; analysis ; Cell Survival ; Cells, Cultured ; Glucose ; deficiency ; Intercellular Signaling Peptides and Proteins ; Myocytes, Cardiac ; physiology ; Phosphatidylinositol 3-Kinases ; physiology ; Proto-Oncogene Proteins c-akt ; physiology ; Proto-Oncogene Proteins c-bcl-2 ; analysis ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Receptors, G-Protein-Coupled ; physiology ; Signal Transduction ; bcl-2-Associated X Protein ; analysis

OBJECTIVETo investigate the effect of nitric oxide (NO) on the expression of apelin receptor mRNA, as well as their correlation, in the caudate nucleus of rat.

METHODSL-Arginine (L-Arg), N(G)-nitro-L-arginine methyl ester (L-NAME) and normal saline (NS) was separately microinjected into rat caudate nucleus. Expressions of neuronal NO synthase (nNOS) mRNA and apelin receptor mRNA were detected by RT-PCR at 4, 8, 12, 24 and 48 h after microinjection, and their correlation was determined.

RESULTSThe expressions of nNOS mRNA and apelin receptor mRNA were both significantly increased after microinjection of L-Arg, but significantly decreased after microinjection of L-NAME compared with the NS control group. The nNOS mRNA had a positive correlation with the expression of apelin receptor mRNA after microinjection of L-Arg and L-NAME.

CONCLUSIONThe activity of NOS in the central nervous system, especially in the caudate nucleus, is one of the key factors for NO to exert many kinds of biological actions, such as modulation of central pain, as a neurotransmitter. The neurobiological action of NO in rat caudate nucleus may be associated with apelin receptors.

Animals ; Apelin Receptors ; Arginine ; pharmacology ; Caudate Nucleus ; drug effects ; metabolism ; Enzyme Inhibitors ; pharmacology ; Gene Expression Regulation ; drug effects ; physiology ; Male ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; physiology ; Nitric Oxide Synthase Type I ; metabolism ; RNA, Messenger ; Rats ; Rats, Wistar ; Receptors, G-Protein-Coupled ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; methods