Apelin-13 attenuates early brain injury through inhibiting inflammation and apoptosis in rats after experimental subarachnoid hemorrhage

Elabela ameliorates neuronal pyroptosis and mitochondrial fission via APJ/ZBP1 signaling in ischemic stroke

Pyroptosis signifies a significant form of programmed neuronal demise subsequent to ischemic stroke. In our prior investigations, we demonstrated that the Elabela (ELA)-Apelin receptor (APJ) axis alleviated neuronal death by improving collateral circulation and mitigating ferroptosis in a murine model of middle cerebral artery occlusion (MCAO). However, the connection between ELA and neuronal pyroptosis remains further elucidation. Here, we observed an upregulation of ELA and APJ expression in both murine brain specimens and cultured HT-22 hippocampal neurons exposed to experimental ischemic stroke. ELA administration markedly diminished the infarct size in comparison to controls. ELA treatment ameliorated neurological deficits and anxiety-like symptoms in mice with stroke, concurrently inhibiting pyroptosis and mitochondria fission in neurons. Conversely, ELA knockdown yielded the opposite effects. Utilizing RNA-sequencing analysis, we identified a candidate for pyroptosis priming, Z-DNA-binding protein 1 (ZBP1), which was suppressed in ELA-treated HT-22 neurons during oxygen-glucose deprivation/reperfusion (OGD/R). Subsequent co-immunoprecipitation analyses demonstrated the binding between APJ and ZBP1. Specifically, APJ suppressed ZBP1 to inhibit NLRP3 inflammasome activation and dynamin-related protein 1-mediated mitochondrial fission in neurons. In summary, our findings suggest that ELA functions as a stroke-induced signal limiting neuronal pyroptosis and mitochondrial fission via APJ/ZBP1 signaling, thereby underscoring ELA as a potential therapeutic target for ischemic stroke treatment.

Neuroprotective effect of apelin-13 and other apelin forms-a review

Neurodegenerative diseases, which occur when neurons begin to deteriorate, affect millions of people worldwide. These age-related disorders are becoming more common partly because the elderly population has increased in recent years. While no treatments are accessible, every year an increasing number of therapeutic and supportive options become available. Various substances that may have neuroprotective effects are currently being researched. One of them is apelin. This review aims to illustrate the results of research on the neuroprotective effect of apelin amino acid oligopeptide which binds to the apelin receptor and exhibits neuroprotective effects in the central nervous system. The collected data indicate that apelin can protect the central nervous system against injury by several mechanisms. More studies are needed to thoroughly investigate the potential neuroprotective effects of this peptide in neurodegenerative diseases and various other types of brain damage.

Apelin-13: A Protective Role in Vascular Diseases

Vascular disease is a common problem with high mortality all over the world. Apelin-13, a key subtype of apelin, takes part in many physiological and pathological responses via regulating many target genes and target molecules or participating in many signaling pathways. More and more studies have demonstrated that apelin-13 is implicated in the onset and progression of vascular disease in recent years. It has been shown that apelin-13 could ameliorate vascular disease by inhibiting inflammation, restraining apoptosis, suppressing oxidative stress, and facilitating autophagy. In this article, we sum up the progress of apelin-13 in the occurrence and development of vascular disease and offer some insightful views about the treatment and prevention strategies of vascular disease.

Apelin-13 protects against cisplatin-induced ototoxicity by inhibiting apoptosis and regulating STAT1 and STAT3

The ototoxic side effect of cisplatin is a main cause of sensorineural hearing loss. This side effect limits the clinical application of cisplatin and affects patients' quality of life. This study was designed to investigate the effect of apelin-13 on cisplatin-induced C57BL/6 mice hearing loss model and explore the potential underlying molecular mechanisms. Mice were intraperitoneally injected with 100 μg/kg apelin-13 2 h before 3 mg/kg cisplatin injection for 7 consecutive days. Cochlear explants cultured in vitro were pretreated with 10 nM apelin-13 2 h prior to 30 μM cisplatin treatment for another 24 h. Hearing test and morphology results showed that apelin-13 attenuated cisplatin-induced mice hearing loss and protected cochlear hair cells and spiral ganglion neurons from damage. In vivo and in vitro experimental results showed that apelin-3 reduced cisplatin-induced apoptosis of hair cells and spiral ganglion neurons. In addition, apelin-3 preserved mitochondrial membrane potential and inhibited ROS production in cultured cochlear explants. Mechanistic studies showed that apelin-3 decreased cisplatin-induced cleaved caspase 3 expression but increased Bcl-2; inhibited the expression of pro-inflammatory factors TNF-a and IL-6; and increased STAT1 phosphorylation but decreased STAT3 phosphorylation. In conclusion, our results indicate that apelin-13 could be a potential otoprotective agent to prevent cisplatin-induced ototoxicity by inhibiting apoptosis, ROS production, TNF-α and IL-6 expression, and regulating phosphorylation of STAT1 and STAT3 transcription factors.

Apelin/APJ system: an emerging therapeutic target for neurological diseases

Apelin, an endogenous ligand for the G protein-coupled receptor APJ, is extensively expressed in various systems, especially the nervous system. This article reviews the role of apelin/APJ system in neurological diseases. In detail, apelin/APJ system can relieve acute brain injury including subarachnoid hemorrhage, traumatic brain injury, and ischemic stroke. Also, apelin/APJ system has therapeutic effects on chronic neurodegenerative disease models, involving the regulation of neurotrophic factors, neuroendocrine, oxidative stress, neuroinflammation, neuronal apoptosis, and autophagy. In addition, through different routes of administration, apelin/APJ system has a biphasic effect on depression, epilepsy, and pain. However, apelin/APJ system exacerbates the proliferation and invasion of glioblastoma. Thus, apelin/APJ system is expected to be a therapeutic target for the treatment of nervous system diseases.

Apelin-13 reduces lipopolysaccharide-induced neuroinflammation and cognitive impairment via promoting glucocorticoid receptor expression and nuclear translocation (Manuscript-revision)

Neuroinflammation is usually associated with cognitive decline, which is involved in neurodegenerative diseases. Apelin, a neuropeptide, exerts various biological roles in central nervous system. Recent evidence showed that apelin-13, an active form of apelin, suppresses neuroinflammation and improves cognitive decline in diverse pathological processes. However, the underlying mechanism of apelin-13 in neuroinflammation remains largely unknown. The present study aimed to determine underlying mechanism of apelin-13 on neuroinflammation-related cognitive decline. The lipopolysaccharide (LPS) intracerebroventricular (i.c.v.) to is used to establish a rat model of neuroinflammation-related cognitive decline. The results showed that apelin-13 inhibits LPS-induced neuroinflammation and improves cognitive impairment. Apelin-13 upregulates the GR level and nuclear translocation in hippocampus of rats. Moreover, glucocorticoid receptor inhibitor RU486 prevents apelin-13-mediated neuroprotective actions on cognitive function. Taken together, apelin-13 could exert a protective effect in neuroinflammation-mediated cognitive impairment via the activation of GR expression and nuclear translocation.

The beneficial roles of apelin-13/APJ system in cerebral ischemia: Pathogenesis and therapeutic strategies

The incidence of cerebral ischemia has increased in the past decades, and the high fatality and disability rates seriously affect human health. Apelin is a bioactive peptide and the ligand of the G protein-coupled receptor APJ. Both are ubiquitously expressed in the peripheral and central nervous systems, and regulate various physiological and pathological process in the cardiovascular, nervous and endocrine systems. Apelin-13 is one of the subtypes of apelin, and the apelin-13/APJ signaling pathway protects against cerebral ischemia by promoting angiogenesis, inhibiting excitotoxicity and stabilizing atherosclerotic plaques. In this review, we have discussed the role of apelin-13 in the regulation of cerebral ischemia and the underlying mechanisms, along with the therapeutic potential of the apelin-13/APJ signaling pathway in cerebral ischemia.