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

Apelin alleviated neuroinflammation and promoted endogenous neural stem cell proliferation and differentiation after spinal cord injury in rats

Background

Spinal cord injury (SCI) causes devastating neurological damage, including secondary injuries dominated by neuroinflammation. The role of Apelin, an endogenous ligand that binds the G protein-coupled receptor angiotensin-like receptor 1, in SCI remains unclear. Thus, our aim was to investigate the effects of Apelin in inflammatory responses and activation of endogenous neural stem cells (NSCs) after SCI.

Methods

Apelin expression was detected in normal and injured rats, and roles of Apelin in primary NSCs were examined. In addition, we used induced pluripotent stem cells (iPSCs) as a carrier to prolong the effective duration of Apelin and evaluate its effects in a rat model of SCI.

Results

Co-immunofluorescence staining suggested that Apelin was expressed in both astrocytes, neurons and microglia. Following SCI, Apelin expression decreased from 1 to 14 d and re-upregulated at 28 d. In vitro, Apelin promoted NSCs proliferation and differentiation into neurons. In vivo, lentiviral-transfected iPSCs were used as a carrier to prolong the effective duration of Apelin. Transplantation of transfected iPSCs in situ immediately after SCI reduced polarization of M1 microglia and A1 astrocytes, facilitated recovery of motor function, and promoted the proliferation and differentiation of endogenous NSCs in rats.

Conclusion

Apelin alleviated neuroinflammation and promoted the proliferation and differentiation of endogenous NSCs after SCI, suggesting that it might be a promising target for treatment of SCI.

Correlation Between Apelin and Collateral Circulation in Patients with Middle Cerebral Artery Occlusion and Moyamoya Disease

Background and Objectives

Moyamoya disease (MMD) is a unique cerebrovascular occlusive disease with abnormal vascular hyperplasia, which causes cerebrovascular accidents like intracranial arteriosclerosis. This study aimed to explore whether plasma apelin levels are related to good collateral circulation in ischemic diseases, which may be higher in patients with MMD than middle cerebral artery (MCA) occlusion or healthy controls, and may have a connection with the MMD grades.

Methods

We recruited 68 MMD patients and 25 MCA occlusion patients diagnosed by angiography, including 29 patients without cerebrovascular problems as controls. We examined the plasma apelin, serum nitric oxide (NO), and vascular endothelial growth factor (VEGF) levels of all subjects by ELISA kit. We compared the relationship between apelin, NO, and VEGF in the blood of three groups, to explore the relationship. We also investigated whether the plasma apelin-13, apelin-17, and apelin-36 levels correlate with the MMD classification.

Results

Univariate analyses indicated that the MMD group had the higher plasma apelin-13, apelin-17, apelin-36, and serum NO levels than the MCA occlusion and healthy control groups. Binary logistic regression analyses further showed that the apelin-13 level was substantially higher in MMD patients than in MCA occlusion patients. Patients with MMD were significantly younger than patients with MCA occlusion by their mean ages. Linear regression analyses were performed to compare apelin levels between different grades of the patients with MMD. Apelin-13, apelin-17, and apelin-36 levels increased with the gradual increase of compensation grades level independent of NO and VEGF. Apelin-13 and apelin-36 showed a positive effect on the compensation scores in MMD.

Conclusion

Our study demonstrated that apelin-13 was significantly increased in patients with MMD than patients with MCA occlusion independent of NO and VEGF. Moreover, plasma apelin-13, apelin-17, and apelin-36 levels increase with the grades of MMD.

Contribution of Apelin-17 to Collateral Circulation Following Cerebral Ischemic Stroke

Apelin, an essential mediator of homeostasis, is crucially involved in cardiovascular diseases, including ischemic stroke. However, the functional roles of apelin-17 in cerebral collateral circulation and ischemic stroke protection are unknown. Here, we investigated the association between plasma apelin-17 levels and collateral circulation in patients with ischemic stroke and examined the mechanism undergirding the effects of apelin-17 on cerebral artery contraction and ischemic stroke protection in an animal model. Plasma nitric oxide (NO), apelin-17, and apelin-36 levels were assessed by enzyme-linked immunosorbent assays in ischemic stroke patients with good or poor collateral circulation and in healthy participants. Additionally, the effects of apelin-17 on rat basilar artery contractions (in vitro) and cerebral ischemia (in vivo) were determined using vessel tension measurements and nuclear magnetic resonance, respectively. Patients with good collateral circulation had significantly higher plasma apelin-17 and apelin-36 levels than both patients with poor collateral circulation and healthy participants and plasma NO levels significantly higher than those in healthy participants. In vitro, apelin-17 pretreatment markedly attenuated U46619-induced rat basilar artery contractions in an endothelium-dependent manner. Additionally, NO production or guanylyl cyclase inhibitors abolished the apelin-17 effect on U46619-induced vascular contraction. Intravenous pretreatment of rats with apelin-17 markedly reduced cerebral infarct volume at 24 h after middle cerebral artery occlusion. Plasma apelin-17 levels in ischemic stroke patients were positively associated with enhanced collateral circulation, which our animal study data suggested may have resulted from an apelin-17-induced cerebral artery dilation mediated through the NO-cGMP pathway.