Aldosterone enhances high phosphate-induced vascular calcification through inhibition of AMPK-mediated autophagy

Aldosterone promotes calcification of vascular smooth muscle cells in mice through the AIF-1/Wnt/β-catenin signaling pathway

OBJECTIVE

This study aimed to investigate the impact of aldosterone on calcification in murine vascular smooth muscle cells (VSMCs) via the allograft inflammatory factor-1 (AIF-1)/Wnt/β-catenin signaling pathway.

METHODS

Mouse VSMCs were cultured in vitro, and calcification was induced by treatment with 100 nM aldosterone. The level of calcification in mouse VSMCs was evaluated using colorimetric assays to assess ALP activity and qRT-PCR to identify the expression of calcification-related markers, such as Runx2, α-SMA, OCN, and ALP mRNA. Western blot analysis was performed to determine the protein expression levels associated with the Wnt/β-catenin pathway (LRP6, p-LRP6, GSK3β, p-GSK3β, β-catenin) and AIF-1. Plasmid transfection techniques were utilized to either knock down or overexpress AIF-1, and the subsequent alterations in these markers were observed.

RESULTS

(1) Compared to the control group, the aldosterone treatment group with exhibited a significant increase in ALP. Concurrently, Runx2, OCN, and ALP mRNA levels increased, as did LRP6, p-LRP6, GSK3β, p-GSK3β, β-catenin, and AIF-1 protein levels. Additionally, a significant decrease in the expression of α-SMA mRNA was observed (P < 0.05). (2) The aldosterone + oe-AIF-1 group showed significant increases in ALP activity compared to the aldosterone + oe-NC group, whereas the aldosterone + sh-AIF-1 group showed significant decreases (P < 0.05). (3) The aldosterone + oe-AIF-1 group exhibited significantly upregulated expression of AIF-1, p-LRP6/LRP6, p-GSK3β/GSK3β, and β-catenin proteins relative to the aldosterone + oe-NC group (P < 0.05). This was concurrent with increased mRNA expression of Runx2, OCN, and ALP, and decreased α-SMA mRNA expression (P < 0.05).

CONCLUSION

Aldosterone affects the calcification process in mouse VSMCs, and the activation of the AIF-1/Wnt/β-catenin signaling pathway is the mechanism behind its action.

USP10 alleviates Nε-carboxymethyl-lysine-induced vascular calcification and atherogenesis in diabetes mellitus by promoting AMPK activation

Vascular calcification (VC) is a characteristic feature in patients with diabetes mellitus (DM) and is closely associated with the osteogenic differentiation of vascular smooth muscle cells (VSMCs). Ubiquitin-Specific Protease 10 (USP10) has been shown to regulate multiple cellular processes; however, its relationship with diabetic VC remains unclear. This study aims to elucidate the role of USP10 in VC development and the underlying regulatory mechanisms. Nε-carboxymethyl lysine (CML) was significantly increased in calcified ateries from diabetic atherosclerosis ApoE-/- mice fed with high-fat diets. CML downregulated USP10 expression in VSMCs and calcified mice coronary arteries, as assessd by Western blotting, RT-qPCR,immunofluorescence and immunohistochemistry. Loss-and gain-of-function experiments were conducted both in vitro and in vivo to verify the biological functions of USP10. Ectopic expression of USP10 mitigated the severity of VC. With regard to the mechanism, the interaction between USP10 and AMPKα was investigated through double-label immunofluorescence and Co-immunoprecipitation. In vitro ubiquitination assay revealed that USP10 was capable of mediating AMPKα ubiquitination and caused increased AMPKα phosphorylation level at Thr172. Moreover, the anticalcification effect of USP10 was reversed by pharmacological inhibition of AMPK signaling pathway. The current fundings suggest an important role of USP10 in diabetic VC progression, at least in part, via mediating the ubiquitination and activation of AMPKα. USP10 may serve as a novel therapeutic target for the treatment of diabetic VC.

Pathogenesis and Mechanism of Uremic Vascular Calcification

This review elucidates the modeling and mechanistic studies of vascular calcification in chronic kidney disease - mineral and bone disorder. In patients with chronic kidney disease, metabolic abnormalities in uremic toxins, including phosphate and indole sulfate, are closely associated with vascular calcification. Vitamin K, vascular circadian clock, and autophagy are also key factors involved in vascular calcification. Furthermore, communication between endothelial cells and smooth muscle cells also plays a pivotal role in the regulation of this process. Together, these factors accelerate vascular calcification progression and increase the risk of cardiovascular events. Therefore, timely intervention for vascular calcification is essential for patients with chronic kidney disease.

Mineralocorticoid Receptors in Vascular Smooth Muscle: Blood Pressure and Beyond

After half a century of evidence suggesting the existence of mineralocorticoid receptors (MR) in the vasculature, the advent of technology to specifically knockout the MR from smooth muscle cells (SMCs) in mice has elucidated contributions of SMC-MR to cardiovascular function and disease, independent of the kidney. This review summarizes the latest understanding of the molecular mechanisms by which SMC-MR contributes to (1) regulation of vasomotor function and blood pressure to contribute to systemic and pulmonary hypertension; (2) vascular remodeling in response to hypertension, vascular injury, obesity, and aging, and the impact on vascular calcification; and (3) cardiovascular pathologies including aortic aneurysm, heart valve dysfunction, and heart failure. Data are reviewed from in vitro studies using SMCs and in vivo findings from SMC-specific MR-knockout mice that implicate target genes and signaling pathways downstream of SMC-MR. By regulating expression of the L-type calcium channel subunit Cav1.2 and angiotensin II type-1 receptor, SMC-MR contributes to myogenic tone and vasoconstriction, thereby contributing to systemic blood pressure. MR activation also promotes SMC proliferation, migration, production and degradation of extracellular matrix, and osteogenic differentiation by regulating target genes including connective tissue growth factor, osteopontin, bone morphogenetic protein 2, galectin-3, and matrix metallopeptidase-2. By these mechanisms, SMC-MR promotes disease progression in models of aging-associated vascular stiffness, vascular calcification, mitral and aortic valve disease, pulmonary hypertension, and heart failure. While rarely tested, when sexes were compared, the mechanisms of SMC-MR-mediated disease were sexually dimorphic. These advances support targeting SMC-MR-mediated mechanisms to prevent and treat diverse cardiovascular disorders.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

AMPK-mediated autophagy is involved in the protective effect of canagliflozin in the vitamin D3 plus nicotine calcification model in rats

Vascular calcification (VC) is a major risk factor for cardiovascular events. A mutual interplay between inflammation, oxidative stress, apoptosis, and autophagy is implicated in its development. Herein, we aimed to evaluate the potential protective effects of canagliflozin in a vitamin D3 plus nicotine (VDN) model of VC, and to explore potential mechanisms. VC was induced by VDN in adult male Wistar rats on day one. Then, rats were randomly assigned into three groups to receive canagliflozin (10 mg or 20 mg/kg/day) or its vehicle for 4 weeks. Age-matched normal rats served as a control group. After euthanization, aorta and kidneys were harvested for biochemical and histopathological evaluation of calcification. Aortic markers of oxidative stress, alkaline phosphatase (ALP) activity, runt-related transcription factor (Runx2) and bone morphogenic protein-2 (BMP-2) levels were determined. Additionally, the protein expression of autophagic markers, LC3 and p62, and adenosine monophosphate activated protein kinase (AMPK) were also assessed in aortic homogenates. Canagliflozin dose-dependently improved renal function, enhanced the antioxidant capacity of aortic tissues and reduced calcium deposition in rat aortas and kidneys. Both doses of canagliflozin attenuated ALP and osteogenic markers while augmented the expression of autophagic markers and AMPK. Histopathological examination of aortas and kidneys by H&E and Von Kossa stain further support the beneficial effect of canagliflozin. Canagliflozin could alleviate VDN-induced vascular calcification, in a dose dependent manner, via its antioxidant effect and modulation of autophagy. Further studies are needed to verify whether this effect is a member or a class effect.

The Role of Autophagy in Type 2 Diabetic Kidney Disease Management

Diabetic kidney disease (DKD), or diabetic nephropathy (DN), is one of the most prevalent complications of type 2 diabetes mellitus (T2DM) and causes severe burden on the general welfare of T2DM patients around the world. While several new agents have shown promise in treating this condition and potentially halting the progression of the disease, more work is needed to understand the complex regulatory network involved in the disorder. Recent studies have provided new insights into the connection between autophagy, a physiological metabolic process known to maintain cellular homeostasis, and the pathophysiological pathways of DKD. Typically, autophagic activity plays a role in DKD progression mainly by promoting an inflammatory response to tissue damage, while both overactivated and downregulated autophagy worsen disease outcomes in different stages of DKD. This correlation demonstrates the potential of autophagy as a novel therapeutic target for the disease, and also highlights new possibilities for utilizing already available DN-related medications. In this review, we summarize findings on the relationship between autophagy and DKD, and the impact of these results on clinical management strategies.

Antihypertensive treatment with hydrochlorothiazide-hydralazine combination aggravates medial vascular calcification in CKD rats with mineral bone disorder

Background

Arterial stiffness and medial vascular calcification, leading to isolated systolic blood pressure (BP), are major cardiovascular risk factors in patients with chronic kidney disease (CKD) and mineral bone disorders (MBD). The impact of BP on MBD-induced medial vascular calcification in CKD remains uncertain. We investigated whether BP reduction improves arterial stiffness and medial vascular calcification in a rat model of CKD-MBD.

Methods

CKD was induced in Wistar rats by subtotal nephrectomy. Then, MBD was generated by a Ca/P-rich diet with calcitriol supplementation to induce medial vascular calcification. Two antihypertensive treatments were evaluated: (1) the angiotensin AT1 receptor antagonist losartan, and (2) the combination of the thiazide diuretic hydrochlorothiazide and the direct vasodilator hydralazine (HCTZ/HY). After 5 weeks, mean BP (MBP), pulse pressure (PP), and pulse wave velocity (PWV) were determined. Vascular calcification was assessed in the thoracic aorta.

Results

While MBP was similar in CKD-MBD and control CKD rats, PP and PWV were increased in CKD-MBD rats. The heightened arterial stiffness in CKD-MBD rats was associated with diffused medial calcification along the thoracic aorta. Although both losartan and HCTZ/HY reduced MBP in CKD-MBD rats, losartan did not affect PP and PWV nor medial vascular calcification, whereas HCTZ/HY, unexpectedly, further increased arterial stiffness and medial vascular calcification.

Conclusion

In the rat model of CKD-MBD, antihypertensive treatment with losartan did not affect arterial stiffness or medial vascular calcification. However, HCTZ/HY treatment aggravated arterial stiffness and vascular calcification despite a similar reduction of MBP, suggesting a blood pressure-independent mechanism for vascular calcification.

Upregulated LncRNA H19 Sponges MiR-106a-5p and Contributes to Aldosterone-Induced Vascular Calcification via Activating the Runx2-Dependent Pathway

BACKGROUND

Excess aldosterone is implicated in vascular calcification (VC), but the mechanism by which aldosterone-MR (mineralocorticoid receptor) complex promotes VC is unclear. Emerging evidence indicates that long-noncoding RNA H19 (H19) plays a critical role in VC. We examined whether aldosterone-induced osteogenic differentiation of vascular smooth muscle cells (VSMCs) through H19 epigenetic modification of Runx2 (runt-related transcription factor-2) in a MR-dependent manner.

METHODS

We induced in vivo rat model of chronic kidney disease using a high adenine and phosphate diet to explore the relationship among aldosterone, MR, H19, and VC. We also cultured human aortic VSMCs to explore the roles of H19 in aldosterone-MR complex-induced osteogenic differentiation and calcification of VSMCs.

RESULTS

H19 and Runx2 were significantly increased in aldosterone-induced VSMC osteogenic differentiation and VC, both in vitro and in vivo, which were significantly blocked by the MR antagonist spironolactone. Mechanistically, our findings reveal that the aldosterone-activated MR bound to H19 promoter and increased its transcriptional activity, as determined by chromatin immunoprecipitation, electrophoretic mobility shift assay, and luciferase reporter assay. Silencing H19 increased microRNA-106a-5p (miR-106a-5p) expression, which subsequently inhibited aldosterone-induced Runx2 expression at the posttranscriptional level. Importantly, we observed a direct interaction between H19 and miR-106a-5p, and downregulation of miR-106a-5p efficiently reversed the suppression of Runx2 induced by H19 silencing.

CONCLUSIONS

Our study clarifies a novel mechanism by which upregulation of H19 contributes to aldosterone-MR complex-promoted Runx2-dependent VSMC osteogenic differentiation and VC through sponging miR-106a-5p. These findings highlight a potential therapeutic target for aldosterone-induced VC.

Autophagy and podocytopathy

Autophagy is a complex process of lysosomal-dependent degradation of unwanted cellular material. In response to endogenous or exogenous stimuli, autophagy is induced and regulated by two kinases: the AMP activated kinase and the mammalian target of rapamycin (mTOR). Cells activated by Unc-51-like kinase 1 form a double membrane complex that sequesters the cargo (phagophore) and elongates producing spherical vesicles (autophagosomes). These reach and fuse with lysosomes, which degrade the cargo (autolysosomes). The resulting macromolecules are released back and recycled in the cytosol for reuse. In the podocyte, autophagy is a homeostatic mechanism that contributes to the formation and preservation of the morphological and functional integrity of actin cytoskeleton. Podocytes, fenestrated endothelial cells and glomerular basement membrane compose the glomerular filtration barrier. Podocyte damage may cause dysfunction of the glomerular barrier, proteinuria and glomerulosclerosis in different glomerular diseases and particularly in so-called podocytopathies, namely minimal change disease and focal segmental glomerulosclerosis. Several drugs and molecules may activate autophagic function in murine models. Among them, aldosterone inhibitors, mineralocorticoid inhibitors and vitamin D3 were proven to protect podocyte from injury and reduce proteinuria in clinical studies. However, no clinical trial with autophagy regulators in podocytopathies has been conducted. Caution is needed with other autophagy activators, such as mTOR inhibitors and metformin, because of potential adverse events.

Primary Aldosteronism and Drug Resistant Hypertension: A "Chicken-Egg" Story

Drug-resistant arterial hypertension (RH) is a major risk factor for cardiovascular disease, often due to overlooked underlying causes. Identification of such causes poses significant clinical challenges. In this setting, primary aldosteronism (PA) is a frequent cause of RH and its prevalence in RH patients is likely higher than 20%.The pathophysiological link between PA and the development and maintenance of RH involves target organ damage and the cellular and extracellular effects of aldosterone excess that promote pro-inflammatory and pro-fibrotic changes in the kidney and vasculature.The feasibility of adrenal vein sampling in PA patients with RH, and the clinical benefit achieved by adrenalectomy, further emphasize the need to implement systematic screening for this common form of secondary hypertension in the management of a high-risk population as RH patients.: We herein review the current knowledge of the factors that contribute to the RH phenotype with a focus on PA and discuss the issues regarding the screening for PA in this setting and the therapeutic approaches (surgical and medical) aimed at resolving RH caused by PA.

Cardiovascular Disease in Obstructive Sleep Apnea: Putative Contributions of Mineralocorticoid Receptors

Obstructive sleep apnea (OSA) is a chronic and highly prevalent condition that is associated with oxidative stress, inflammation, and fibrosis, leading to endothelial dysfunction, arterial stiffness, and vascular insulin resistance, resulting in increased cardiovascular disease and overall mortality rates. To date, OSA remains vastly underdiagnosed and undertreated, with conventional treatments yielding relatively discouraging results for improving cardiovascular outcomes in OSA patients. As such, a better mechanistic understanding of OSA-associated cardiovascular disease (CVD) and the development of novel adjuvant therapeutic targets are critically needed. It is well-established that inappropriate mineralocorticoid receptor (MR) activation in cardiovascular tissues plays a causal role in a multitude of CVD states. Clinical studies and experimental models of OSA lead to increased secretion of the MR ligand aldosterone and excessive MR activation. Furthermore, MR activation has been associated with worsened OSA prognosis. Despite these documented relationships, there have been no studies exploring the causal involvement of MR signaling in OSA-associated CVD. Further, scarce clinical studies have exclusively assessed the beneficial role of MR antagonists for the treatment of systemic hypertension commonly associated with OSA. Here, we provide a comprehensive overview of overlapping mechanistic pathways recruited in the context of MR activation- and OSA-induced CVD and propose MR-targeted therapy as a potential avenue to abrogate the deleterious cardiovascular consequences of OSA.

Autophagy Is Required to Sustain Increased Intestinal Cell Proliferation during Phenotypic Plasticity Changes in Honey Bee (Apis mellifera)

Tissue phenotypic plasticity facilitates rapid adaptation of organisms to biotic and/or abiotic pressure. The reproductive capacity of honey bee workers (Apis mellifera) is plastic and responsive to pheromones produced by broods and the queen. Egg laying workers (ELWs), which could reactivate their ovaries and lay haploid eggs upon queen lost, have been commonly discussed from many aspects. However, it remains unclear whether midgut homeostasis in ELWs is affected during plastic changes. Here, we found that the expression of nutrition- and autophagy-related genes was up-regulated in the midguts of ELWs, compared with that in nurse workers (NWs) by RNA-sequencing. Furthermore, the area and number of autophagosomes were increased, along with significantly increased cell death in the midguts of ELWs. Moreover, cell cycle progression in the midguts of ELWs was increased compared with that in NWs. Consistent with the up-regulation of nutrition-related genes, the body and midgut sizes, and the number of intestinal proliferation cells of larvae reared with royal jelly (RJ) obviously increased more than those reared without RJ in vitro. Finally, cell proliferation was dramatically suppressed in the midguts of ELWs when autophagy was inhibited. Altogether, our data suggested that autophagy was induced and required to sustain cell proliferation in ELWs' midguts, thereby revealing the critical role of autophagy played in the intestines during phenotypic plasticity changes.

Knockdown of circHIPK3 promotes the osteogenic differentiation of human bone marrow mesenchymal stem cells through activating the autophagy flux

Many circular RNAs (circRNAs) involved in the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs) have recently been discovered. The role of circHIPK3 in osteogenesis has yet to be determined. Cell transfection was conducted using small-interfering RNAs (siRNAs). Expression of osteogenic markers were detected by quantitative reverse transcription-polymerase chain reaction, western blotting analysis, and immunofluorescence staining. Ectopic bone formation models in nude mice were used to examined the bone formation ability in vivo. The autophagy flux was examined via western blotting analysis, immunofluorescence staining and transmission electron microscopy analysis. RNA immunoprecipitation (RIP) analysis was carried out to analyze the binding between human antigen R (HUR) and circHIPK3 or autophagy-related 16-like 1 (ATG16L1). Actinomycin D was used to determine the mRNA stability. Our results demonstrated that silencing circHIPK3 promoted the osteogenesis of hBMSCs while silencing the linear mHIPK3 did not affect osteogenic differentiation, both in vivo and in vitro. Moreover, we found that knockdown of circHIPK3 activated autophagy flux. Activation of autophagy enhanced the osteogenesis of hBMSCs and inhibition of autophagy reduced the osteogenesis through using autophagy regulators chloroquine and rapamycin. We also discovered that circHIPK3 and ATG16L1 both bound to HUR. Knockdown of circHIPK3 released the binding sites of HUR to ATG16L1, which stabilized the mRNA expression of ATG16L1, resulting in the upregulation of ATG16L1 and autophagy activation. CircHIPK3 functions as an osteogenesis and autophagy regulator and has the potential for clinical application in the future.

Aldosterone as a Mediator of Cardiovascular Damage

Besides the physiological regulation of water, sodium, and potassium homeostasis, aldosterone modulates several physiological and pathological processes in the cardiovascular system. At the vascular level, aldosterone excess stimulates endothelial dysfunction and infiltration of inflammatory cells, enhances the development of the atherosclerotic plaque, and favors plaque instability, arterial stiffness, and calcification. At the cardiac level, aldosterone increases cardiac inflammation, fibrosis, and myocardial hypertrophy. As a clinical consequence, high aldosterone levels are associated with enhanced risk of cardiovascular events and mortality, especially when aldosterone secretion is inappropriate for renin levels and sodium intake, as in primary aldosteronism. Several clinical trials showed that mineralocorticoid receptor antagonists reduce cardiovascular mortality in patients with heart failure and reduced ejection fraction, but inconclusive results were reported for other cardiovascular conditions, such as heart failure with preserved ejection fraction, myocardial infarction, and atrial fibrillation. In patients with primary aldosteronism, adrenalectomy or treatment with mineralocorticoid receptor antagonists significantly mitigate adverse aldosterone effects, reducing the risk of cardiovascular events, mortality, and incident atrial fibrillation. In this review, we will summarize the major preclinical and clinical studies investigating the cardiovascular damage mediated by aldosterone and the protective effect of mineralocorticoid receptor antagonists for the reduction of cardiovascular risk in patients with cardiovascular diseases and primary aldosteronism.

Sex-Related Signaling of Aldosterone/Mineralocorticoid Receptor Pathway in Calcific Aortic Stenosis

BACKGROUND

There are sex differences in the pathophysiology of aortic valve (AV) calcification in patients with aortic stenosis, although the molecular and cellular mechanisms have not been elucidated. Aldosterone (Aldo) promotes proteoglycan synthesis in valve interstitial cells (VICs) from mitral valves via the mineralocorticoid receptor (MR). We investigated the influence of sex in the role of Aldo/MR pathway in AV alterations in patients with aortic stenosis.

METHODS AND RESULTS

MR was expressed by primary aortic VICs and in AVs from patients with aortic stenosis. MR expression positively correlated with VIC activation markers in AVs from both sexes. However, MR expression was positively associated with molecules involved in AV calcification only in AV from men. Aldo enhanced VIC activation markers in cells from men and women. Interestingly, Aldo increased the expression of calcification markers only in VICs isolated from men. In female VICs, Aldo enhanced fibrotic molecules. MR antagonism (spironolactone) blocked all the above effects. Cytokine arrays showed ICAM (intercellular adhesion molecule)-1 and osteopontin to be specifically increased by Aldo in male VICs. In AVs from men, MR expression positively associated with both ICAM-1 (intercellular adhesion molecule-1) and osteopontin. Only in female VICs, estradiol treatment blocked Aldo-induced VICs activation, inflammation, and fibrosis.

CONCLUSIONS

These findings demonstrate that the Aldo/MR pathway could play a role in early stages of aortic stenosis by promoting VICs activation, fibrosis, and ulterior calcification. Importantly, Aldo/MR pathway is involved in fibrosis in women and in early AV calcification only in men. Accordingly, MR antagonism emerges as a new sex-specific pharmacological treatment to prevent AV alterations.

Effect of eplerenone on cognitive impairment in spontaneously hypertensive rats

OBJECTIVE

The present study aimed to determine the effect of blocking brain mineralocorticoid receptor on cognitive impairment in spontaneously hypertensive rats and its intracellular changes.

METHODS

12-week-old male spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were given eplerenone (EPL, 30 mg/Kg/d or 100 mg/Kg/d) or pure water via oral gavage daily for 8 weeks. Effects of blocking brain mineralocorticoid receptor (MR) on cognitive function were examined through cognitive behavioral experiments. The morphology of hippocampal neurons was observed. Synaptic proteins and autophagy levels were detected by western blot.

RESULTS

The results showed decreases in both short-term working memory and long-term spatial learning and memory ability, hippocampal neuron damage, and reduced expression of synaptic proteins in the SHR-Veh group. Impaired autophagy was found in the SHR-Veh group as evidenced by decreased expression levels of Beclin-1 protein and a defect in P62 degradation. These abnormalities were reversed by eplerenone, either the high dosage or low dosage. Reduced cognitive dysfunction and enhanced autophagy in hippocampal neurons in both SHR-EPL30 group and SHR-EPL100 group were independent of lowering blood pressure.

CONCLUSION

Eplerenone improves cognitive deficits observed in SHRs, and increases autophagy in hippocampal neurons of SHRs, which suggests a new site of MR antagonists in treatment of hypertension-related cognitive impairment.

Aldosterone is a possible new stimulating factor for promoting vascular calcification

Background: Aldosterone is an important hormone in the renin-angiotensin-aldosterone system (RAAS), and playing a pivotal role in the development of hypertension, heart failure, and other cardiovascular diseases. Material and method: In this study, the role of the aldosterone in vascular calcification was underwent in rat model compared with other drugs. Vascular calcification, calcium concentration, activity of alkaline phosphatase (ALP), aldosterone, Urotensin II, mineralocorticoid receptor (MR) and Osteopontin (OPN) were detected or confirmed by the von Kossa staining, colorimetric assays, immunohistochemistry and radioimmunoassay, separately. Result: Results revealed that the aldosterone was significantly increased compared calcification + aldosterone group with calcification group, whereas it was notably decreased in calcification + Spironolactone group in the aortic wall. Compared with control group and aldosterone group, calcium content in vascular tissues was increased in calcification group and calcification + aldosterone group. As the immunoreactivity of the MR, OPN, Urotensin II, IL-6, monocyte chemoattractant protein-1, and deposition of collagen in calcification group and aldosterone group, they all were increased slightly, but were significantly increased in calcification + aldosterone group. Conclusion: It is implied that aldosterone may be involved in the development of vascular calcification, however, the mechanism needs to be further studied.

Deletion of soluble epoxide hydrolase suppressed chronic kidney disease-related vascular calcification by restoring Sirtuin 3 expression

Vascular calcification is common in chronic kidney disease (CKD) and contributes to cardiovascular disease (CVD) without any effective therapies available up to date. The expression of soluble epoxide hydrolase (sEH) is different in patients with and without vascular calcification. The present study investigates the role of sEH as a potential mediator of vascular calcification in CKD. Both Ephx2^−/− and wild-type (WT) mice fed with high adenine and phosphate (AP) diet were used to explore the vascular calcification in CKD. Compared with WT, deletion of sEH inhibited vascular calcification induced by AP. sEH deletion also abolished high phosphorus (Pi)-induced phenotypic transition of vascular smooth muscle cells (VSMCs) independent of its epoxyeicosatrienoic acids (EETs) hydrolysis. Further gene expression analysis identified the potential role of Sirtuin 3 (Sirt3) in the sEH-regulated VSMC calcification. Under high Pi treatment, sEH interacted with Sirt3, which might destabilize Sirt3 and accelerate the degradation of Sirt3. Deletion of sEH may preserve the expression of Sirt3, and thus maintain the mitochondrial adenosine triphosphate (ATP) synthesis and morphology, significantly suppressing VSMC calcification. Our data supported that sEH deletion inhibited vascular calcification and indicated a promising target of sEH inhibition in vascular calcification prevention.

β-Hydroxybutyric Inhibits Vascular Calcification via Autophagy Enhancement in Models Induced by High Phosphate

Background: Vascular calcification (VC) is a landmark of aging, while β-hydroxybutyric acid (BHB) induced by calorie restriction has been identified as a promising factor to extend the lifespan. However, the effect of BHB on VC and the potential mechanism remain unknown. Methods: A total of 160 subjects with or without metabolic abnormalities (MAs) were assigned to four groups according to different calcification severities. The association between BHB, MAs, and VC was investigated via mediation analysis. Then, with high phosphate-induced calcification models, the effect of BHB on arterial ring calcification and osteogenic phenotypic differentiation of vascular smooth muscle cells (VSMCs) was investigated. Hereafter the expressions of autophagy biomarkers, autophagy flux, and effects of autophagy inhibitors on VC were detected. Results: Severe VC was observed in the elderly, accompanied with a higher proportion of hypertension, chronic kidney disease, and lower estimated glomerular filtration rate. The serum BHB level was an independent influencing factor of VC severities. With mediation analysis, BHB was determined as a significant mediator in the effects of MAs on VC, and the indirect effect of BHB accounted for 23% of the total effect. Furthermore, BHB directly inhibited arterial ring calcification and osteogenic phenotypic differentiation in VSMCs, accompanied with autophagy enhancement in VSMCs. In accordance, the inhibition of autophagy counteracted the protective effect of BHB on VC. Conclusion: The present study demonstrated that BHB mediated the effects of MAs on VC; then, it further elucidated that BHB could inhibit arterial and VSMC calcification via autophagy enhancement.

Roles of Nuclear Receptors in Vascular Calcification

Vascular calcification is defined as an inappropriate accumulation of calcium depots occurring in soft tissues, including the vascular wall. Growing evidence suggests that vascular calcification is an actively regulated process, sharing similar mechanisms with bone formation, implicating both inhibitory and inducible factors, mediated by osteoclast-like and osteoblast-like cells, respectively. This process, which occurs in nearly all the arterial beds and in both the medial and intimal layers, mainly involves vascular smooth muscle cells. In the vascular wall, calcification can have different clinical consequences, depending on the pattern, localization and nature of calcium deposition. Nuclear receptors are transcription factors widely expressed, activated by specific ligands that control the expression of target genes involved in a multitude of pathophysiological processes, including metabolism, cancer, inflammation and cell differentiation. Some of them act as drug targets. In this review we describe and discuss the role of different nuclear receptors in the control of vascular calcification.

κ-opioid receptor stimulation alleviates rat vascular smooth muscle cell calcification via PFKFB3-lactate signaling

In the present study, the effects and mechanism of action of U50,488H (a selective κ-opioid receptor agonist) on calcification of rat vascular smooth muscle cells (VSMCs) induced by β-glycerophosphate (β-GP) were investigated. VSMCs were isolated and cultured in traditional FBS-based media. A calcification model was established in VSMCs under hyperphosphatemia and intracellular calcium contents. Alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and lactate were detected in cell culture supernatants before and after treatment. Alizarin red staining was used to detect the degree of calcification of VSMCs. Expression levels of key molecules of osteogenic markers, fructose-2,6-biphosphatase 3 (PFKFB3), and proline hydroxylase 2 (PHD2), were determined using western blotting. Further, vascular calcification was induced by vitamin D3 plus nicotine in rats and isolated thoracic aortas, calcium concentration was assessed in rat aortic rings in vitro. We demonstrated that U50,488H inhibited VSMC calcification in a concentration-dependent manner. Moreover, U50,488H significantly inhibited osteogenic differentiation and ALP activity in VSMCs pretreated with β-GP. Further studies confirmed that PFKFB3 expression, LDH level, and lactate content significantly increased during calcification of VSMCs; U50,488H reversed these changes. PHD2 expression showed the opposite trend compared to PFKFB3 expression. nor-BNI or 3-PO abolished U50,488H protective effects. Besides, U50,488H inhibited VSMC calcification in rat aortic rings ex vivo. Collectively, our experiments show that κ-opioid receptor activation inhibits VSMC calcification by reducing PFKFB3 expression and lactate content, providing a potential drug target and strategy for the clinical treatment of vascular calcification.

AMPK: Potential Therapeutic Target for Vascular Calcification

Vascular calcification (VC) is an urgent worldwide health issue with no available medical treatment. It is an active cell-driven process by osteogenic differentiation of vascular cells with complex mechanisms. The AMP-activated protein kinase (AMPK) serves as the master sensor of cellular energy status. Accumulating evidence reveals the vital role of AMPK in VC progression. AMPK is involved in VC in various ways, including inhibiting runt-related transcription factor 2 signaling pathways, triggering autophagy, attenuating endoplasmic reticulum stress and dynamic-related protein 1-mediated mitochondrial fission, and activating endothelial nitric oxide synthase. AMPK activators, like metformin, are associated with reduced calcification deposits in certain groups of patients, indicating that AMPK is a potential therapeutic target for VC.

Tryptanthrin Regulates Vascular Smooth Muscle Cell Phenotypic Switching in Atherosclerosis by AMP-Activated Protein Kinase/Acetyl-CoA Carboxylase Signaling Pathway

ABSTRACT

Atherosclerosis (AS) is one of the most severe cardiovascular diseases involved in the phenotypic switching of vascular smooth muscle cells (VSMCs). Tryptanthrin is a natural product with broad biological activities. However, the effect of tryptanthrin on atherosclerotic progression is unclear. The aim of this study was to determine the role of tryptanthrin in AS and explore the potential mechanism. In vitro, primary VSMCs were stimulated with platelet-derived growth factor-BB (PDGF) to induce cell dedifferentiation. Treatment with tryptanthrin (5 μM or 10 μM) suppressed the proliferation and recovered the contractility of VSMCs in the presence of PDGF. The contractile proteins (α-smooth muscle actin, calponin, and SM22α) were increased, and the synthetic protein vimentin was decreased by tryptanthrin in PDGF-induced VSMCs. ApoE-/- mice fed with high-fat diet were used as an in vivo model of AS. Similarly, gavage administration of tryptanthrin (50 mg/kg or 100 mg/kg) attenuated VSMC phenotypic changes from a contractile to a synthetic state in aortic tissues of AS mice. The serum lipid level, atherosclerotic plaque formation, and arterial intimal hyperplasia were attenuated by tryptanthrin. Furthermore, tryptanthrin increased the expression levels of phosphorylated AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) both in vitro and in vivo. Administration of compound C, an AMPK inhibitor, reversed the inhibitory effect of tryptanthrin on VSMC dedifferentiation in vitro. Thus, we demonstrate that tryptanthrin protects against AS progression through the inhibition of VSMC switching from a contractile to a pathological synthetic phenotype by the activation of AMPK/ACC pathway. It provides novel insights into AS prevention and treatment.