Inhibition of endoplasmic reticulum stress mediates the ameliorative effect of apelin on vascular calcification

Apelin-13 alleviates contrast-induced acute kidney injury by inhibiting endoplasmic reticulum stress

Contrast-induced acute kidney injury (CI-AKI) is a severe complication associated with significant morbidity and mortality, and effective therapeutic strategies are still lacking. Apelin is an endogenous physiological regulator with antioxidative, anti-inflammatory and antiapoptotic properties. However, the role of apelin-13 in CI-AKI remains unclear. In our study, we found that the protein expression levels of apelin were significantly downregulated in rat kidney tissues and HK-2 cells during contrast media treatment. Moreover, we explored the protective effect of apelin-13 on renal tubule damage using in vitro and in vivo models of CI-AKI. Exogenous apelin-13 ameliorated endoplasmic reticulum stress, reactive oxygen species and apoptosis protein expression in contrast media-treated cells and rat kidney tissues. Mechanistically, the downregulation of endoplasmic reticulum stress contributed critically to the antiapoptotic effect of apelin-13. Collectively, our findings reveal the inherent mechanisms by which apelin-13 regulates CI-AKI and provide a prospective target for the prevention of CI-AKI.

Intermedin alleviates diabetic vascular calcification by inhibiting GLUT1 through activation of the cAMP/PKA signaling pathway

BACKGROUND AND AIMS

Vascular calcification (VC) is regarded as an independent risk factor for cardiovascular events in type 2 diabetic patients. Glucose transporter 1 (GLUT1) involves VC. Intermedin/Adrenomedullin-2 (IMD/ADM2) is a cardiovascular protective peptide that can inhibit multiple disease-associated VC. However, the role and mechanism of IMD in diabetic VC remain unclear. Here, we investigated whether IMD inhibits diabetic VC by inhibiting GLUT1.

METHODS AND RESULTS

It was found that plasma IMD concentration was significantly decreased in type 2 diabetic patients and in fructose-induced diabetic rats compared with that in controls. Plasma IMD content was inversely correlated with fasting blood glucose level and VC severity. IMD alleviated VC in fructose-induced diabetic rats. Deficiency of Adm2 aggravated and Adm2 overexpression attenuated VC in high-fat diet-induced diabetic mice. In vitro, IMD mitigated high glucose-induced calcification of vascular smooth muscle cells (VSMCs). Mechanistically, IMD reduced advanced glycation end products (AGEs) content and the level of receptor for AGEs (RAGE). IMD decreased glucose transporter 1 (GLUT1) levels. The inhibitory effect of IMD on RAGE protein level was blocked by GLUT1 knockdown. GLUT1 knockdown abolished the effect of IMD on alleviating VSMC calcification. IMD receptor antagonist IMD17-47 and cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) inhibitor H89 abolished the inhibitory effects of IMD on GLUT1 and VSMC calcification.

CONCLUSIONS

These findings revealed that IMD exerted its anti-calcification effect by inhibiting GLUT1, providing a novel therapeutic target for diabetic VC.

Feedback Interaction Between Apelin and Endoplasmic Reticulum Stress in the Rat Myocardium

ABSTRACT

Apelin is an endogenous active peptide, playing a crucial role in regulating cardiovascular homeostasis. This study aimed to investigate the interaction between apelin and endoplasmic reticulum stress (ERS). Tunicamycin (Tm) and dithiothreitol (DTT) were used to induce ERS in the ex vivo cultured myocardium of rats. Myocardial injury was determined by the activities of lactate dehydrogenase and creatine kinase-MB in the culture medium. The protein levels of an ERS-associated molecule, apelin, and its receptor angiotensin domain type 1 receptor-associated proteins (APJ) in the myocardium were determined by western blot analysis. The level of apelin in the culture medium was determined by enzyme immunoassay. Administration of Tm and DTT triggered ERS activation and myocardial injury, and led to a decrease in protein levels of apelin and APJ, in a dose-dependent manner. Integrated stress response inhibitor, an inhibitor of eukaryotic initiation factor 2α phosphorylation that is commonly used to prevent activation of protein kinase R-like ER kinase cascades, blocked ERS-induced myocardial injury and reduction of apelin and APJ levels. The ameliorative effect of integrated stress response inhibitor was partially inhibited by [Ala]-apelin-13, an antagonist of APJ. Furthermore, apelin treatment inhibited activation of the 3 branches of ERS induced by Tm and DTT in a dose-dependent manner, thereby preventing Tm-induced or DTT-induced myocardial injury. The negative feedback regulation between ERS activation and apelin/APJ suppression might play a critical role in myocardial injury. Restoration of apelin/APJ signaling provides a potential target for the treatment and prevention of ERS-associated tissue injury and diseases.

Endogenous Vasoactive Peptides and Vascular Aging-Related Diseases

Vascular aging is a specific type of organic aging that plays a central role in the morbidity and mortality of cardiovascular and cerebrovascular diseases among the elderly. It is essential to develop novel interventions to prevent/delay age-related vascular pathologies by targeting fundamental cellular and molecular aging processes. Endogenous vasoactive peptides are compounds formed by a group of amino acids connected by peptide chains that exert regulatory roles in intercellular interactions involved in a variety of biological and pathological processes. Emerging evidence suggests that a variety of vasoactive peptides play important roles in the occurrence and development of vascular aging and related diseases such as atherosclerosis, hypertension, vascular calcification, abdominal aortic aneurysms, and stroke. This review will summarize the cumulative roles and mechanisms of several important endogenous vasoactive peptides in vascular aging and vascular aging-related diseases. In addition, we also aim to explore the promising diagnostic function as biomarkers and the potential therapeutic application of endogenous vasoactive peptides in vascular aging-related diseases.

The Ameliorative Effect of Berberine on Vascular Calcification by Inhibiting Endoplasmic Reticulum Stress

ABSTRACT

Vascular calcification (VC), which currently cannot be prevented or treated, is an independent risk factor for cardiovascular events. We aimed to investigate the ameliorative effect of berberine on VC via the activation of Akt signaling and inhibition of endoplasmic reticulum stress (ERS). The VC model was induced by high-dose Vitamin D 3 in rats and beta-glycerophosphate in primary vascular smooth muscle cells of rat aortas, which were evaluated by Alizarin red staining to determine the calcium content and alkaline phosphatase activity. ERS was determined by the levels of GRP78 and CHOP, whereas that of the Akt signaling pathway was determined by the levels of phosphorylated Akt and GSK3β. VC was significantly ameliorated by berberine treatment in vivo and in vitro, and the inhibition of ERS and the activation of the Akt/GSK3 signaling pathway. In the vascular smooth muscle cells of primary rats, tunicamycin, an ERS activator, blocked the ameliorative effect of berberine on VC and ERS, but not the activation of Akt/GSK3. The ameliorative effects of berberine on VC, ERS, and the Akt signaling pathway were all prevented by inhibitor IV. Four-phenylbutyric acid, an ERS inhibitor, can restore the ameliorative effect of berberine on VC and ERS that was blocked by inhibitor IV. Our results are the first to demonstrate the ameliorative effect of VC that was mediated by the activation of the Akt signaling pathway and inhibition of ERS. These results may provide a new pharmaceutical candidate for the prevention and treatment of VC.

APJ/apelin: a promising target for the treatment of retinopathy of prematurity

Retinopathy of prematurity is a noticeable retinal abnormality causing common blindness in children. An uncontrolled retinal vasculature in retinopathy of prematurity inflicts vision loss in numerous children despite the accessibility to a wide range of clinical treatments prescribed for retinopathy of prematurity. Apelin/APJ [class A (rhodopsin-like) G-protein-coupled receptor] signaling regulates retinopathy of prematurity augmented with uncontrolled angiogenesis. Antagonists targeting pathological apelin/APJ-signaling-induced angiogenesis could be effective in attenuating retinopathy of prematurity. The therapeutic proficiency of antagonists in diverse modalities: peptides, bioactive molecules and antibodies, targeting apelin peptides or the APJ receptor is discussed in this review. We hypothesize the antagonists could effectively attenuate the retinal vasculature triggered by apelin/APJ signaling activation governing vision impairment in young children.

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.

Ameliorative effect of allicin on vascular calcification via inhibiting endoplasmic reticulum stress

OBJECTIVES

Vascular calcification (VC) is an independent predictor for cardiovascular events and mortality. However, there are currently no effective methods to reverse or prevent it. The present study aimed to determine the ameliorative effect of allicin on VC.

METHODS

VC model of rats was induced by high-dose vitamin D₃, which was valued by Alizarin Red staining, calcium contents, and alkaline phosphatase in the aorta. Systolic blood pressure, pulse pressure, and pulse wave velocity were measured to determine aortic stiffness. Protein levels were detected by Western blot.

RESULTS

Allicin treatment rescued aortic VC and stiffness. The increased protein levels of RUNX2 and BMP2, two markers of osteoblastic phenotype of vascular smooth muscle cells, in the calcified aorta were attenuated by allicin, whereas the decreased levels of calponin and SM22α induced by calcification were improved. Allicin treatment significantly attenuated the increased protein levels of GRP78, GRP94, and CHOP, which are key markers of endoplasmic reticulum stress, in the calcified aorta. The activation of PERK/eIF2α/ATF4 cascades was also prevented by allicin.

CONCLUSIONS

Allicin could ameliorate aortic VC and stiffness. The ameliorative effect of allicin on VC might be mediated by inhibiting PERK/eIF2α/ATF4 cascades. Our results might provide a new proof for VC treatment.