Apelin Does Not Impair Coronary Artery Relaxation Mediated by Nitric Oxide-Induced Activation of BKCa Channels

Intravenous administration of apeling-13 induces a depressor response by releasing an unidentified substance

Apelin and APJ receptor play an important role in the regulating cardiovascular function; however, conflicting results have been reported regarding the effect of apelin on cardiovascular regulation. In this study, blood pressure and heart rate were measured by femoral arterial catheterization; and cardiac contractility was recorded by left ventricular catheterization through the right carotid artery in rats before and after intravenous administration of [pyr1]-apelin-13. The results show that intravenous administration of apelin-13 caused a dramatic reduction in BP but did not significantly alter heart rate and contractility. To study the mechanism of the apelin-induced depressor response, isometric tension was measured in isolated mesenteric arteries using a myograph approach. Surprisingly, treatment of the arteries with [pyr1]-apelin-13 did not cause relaxation of mesenteric arteries preconstricted with norepinephrine; however, treatment with plasma collected from rats that received intravenous administration of [pyr1]-apelin-13 caused pronounced relaxation of isolated arteries. Incubation with the guanylyl cyclase inhibitor, ODQ, blocked NO-induced relaxation, but did not significantly alter the relaxation response to the plasma from apelin-treated rats. Taken together, these findings demonstrate that intravenous injection of apelin causes a significant depressor response that is mediated by a NO-independent mechanism involving an unidentified substance released into the bloodstream leading to vasodilation.

Hemodynamic impacts of apelin-13 in a neonatal lamb model of septic peritonitis

BACKGROUND

Apelins are potential candidate therapeutic molecules for hemodynamic support. The objective of this study was to assess the hemodynamic impacts of apelin-13 in a neonatal lamb model of septic shock.

METHODS

Lambs were randomized to receive apelin-13 or normal saline. Septic shock was induced by injecting a fecal slurry into the peritoneal cavity. Lambs underwent volume repletion (30 mL/kg over 1 h) followed by intravenous administration of 5 incremental doses (D) of apelin-13 (D1 = 0.039 to D5 = 19.5 µg/kg/h) or normal saline.

RESULTS

Following fecal injection, mean arterial pressure (MAP) and cardiac index (CI) dropped in both groups (p < 0.05). The MAP decreased non-significantly from D1 to D5 (p = 0.12) in the saline group, while increasing significantly (p = 0.02) in the apelin group (-12 (-17; 12) vs. +15 (6; 23) % (p = 0.012)). Systemic vascular resistances were higher in the apelin-13 group at D5 compared to the saline group (4337 (3239, 5144) vs. 2532 (2286, 3966) mmHg/min/mL, respectively, p = 0.046). The CI increased non-significantly in the apelin-13 group.

CONCLUSION

Apelin-13 increased MAP in a neonatal lamb septic shock model.

IMPACT

Administration of apelin-13 stabilized hemodynamics during the progression of the sepsis induced in this neonatal lamb model. Systemic vascular resistances were higher in the apelin-13 group than in the placebo group. This suggests ontogenic differences in vascular response to apelin-13 and warrants further investigation. This study suggests that apelin-13 could eventually become a candidate for the treatment of neonatal septic shock.

Apelin pathway in cardiovascular, kidney, and metabolic diseases: Therapeutic role of apelin analogs and apelin receptor agonists

The apelin/apelin receptor (ApelinR) signal transduction pathway exerts essential biological roles, particularly in the cardiovascular system. Disturbances in the apelin/ApelinR axis are linked to vascular, heart, kidney, and metabolic disorders. Therefore, the apelinergic system has surfaced as a critical therapeutic strategy for cardiovascular diseases (including pulmonary arterial hypertension), kidney disease, insulin resistance, hyponatremia, preeclampsia, and erectile dysfunction. However, apelin peptides are susceptible to rapid degradation through endogenous peptidases, limiting their use as therapeutic tools and translational potential. These proteases include angiotensin converting enzyme 2, neutral endopeptidase, and kallikrein thereby linking the apelin pathway with other peptide systems. In this context, apelin analogs with enhanced proteolytic stability and synthetic ApelinR agonists emerged as promising pharmacological alternatives. In this review, we focus on discussing the putative roles of the apelin pathway in various physiological systems from function to dysfunction, and emphasizing the therapeutic potential of newly generated metabolically stable apelin analogs and non-peptide ApelinR agonists.

Regulation of Apelin-13 on Bcl-2 and Caspase-3 and Its Effects on Adipocyte Apoptosis

OBJECTIVE

The effects of apelin-13 on the expression of Bcl-2 and caspase-3 factors and the apoptosis of adipocytes were studied at the cellular and animal levels.

METHODS

3T3-L1 preadipocytes were cultured and grouped. The third-generation cells were added to the control DMSO solvent and amidation-modified apelin-13. The expression of Bcl-2 and caspase-3 were detected. The cell growth viability and cell apoptosis were detected. DOI model rats were established. The effects of apelin-13 on DOI rat biochemical indicators, the expression of Bcl-2, caspase-3, and cell apoptosis were investigated by injecting amidation-modified apelin-13 through the tail vein.

RESULT

In in vitro experiments, amidation-modified apelin-13 can significantly reduce the growth viability of adipocytes and the expression of Bcl-2, increase the expression of caspase-3, and promote the apoptosis of adipocytes. Animal experiments also show that apelin-13 modified by amidation can adjust the abnormal biochemical indicators of DOI rats, decrease the expression of Bcl-2 in adipose tissue, increase the expression of caspase-3, and promote the apoptosis of adipocytes.

CONCLUSION

Amidation of apelin-13 can promote fat cell apoptosis and reduce the incidence of obesity. The mechanism may be accomplished by inhibiting Bcl-2 and caspase-3 factors. This study helps us understand the effect of apelin-13 on fat cell apoptosis and hopes to provide a basis for the development of antiobesity drugs.