Oxidative stress contributes to vascular calcification in patients with chronic kidney disease

Sulforaphane upregulates the mRNA expression of NRF2 and NQO1 in non-dialysis patients with chronic kidney disease

Sulforaphane (SFN), found in cruciferous vegetables, is a known activator of NRF2 (master regulator of cellular antioxidant responses). Patients with chronic kidney disease (CKD) present an imbalance in the redox state, presenting reduced expression of NRF2 and increased expression of NF-κB. Therefore, this study aimed to evaluate the effects of SFN on the mRNA expression of NRF2, NF-κB and markers of oxidative stress in patients with CKD. Here, we observed a significant increase in the mRNA expression of NRF2 (p = 0.02) and NQO1 (p = 0.04) in the group that received 400 μg/day of SFN for 1 month. Furthermore, we observed an improvement in the levels of phosphate (p = 0.02), glucose (p = 0.05) and triglycerides (p = 0.02) also in this group. On the other hand, plasma levels of LDL-c (p = 0.04) and total cholesterol (p = 0.03) increased in the placebo group during the study period. In conclusion, 400 μg/day of SFN for one month improves the antioxidant system and serum glucose and phosphate levels in non-dialysis CKD patients.

Associations between the composite dietary antioxidant index and abdominal aortic calcification among United States adults: A cross-sectional study

BACKGROUND

Oxidative stress has previously been shown to play a pivotal role in the pathogenesis of vascular calcification. In the present study, we aimed to investigate the association between the composite dietary antioxidant index (CDAI) and abdominal aortic calcification (AAC).

METHODS

We conducted a cross-sectional study of United States adults using data from the 2013-2014 National Health and Nutrition Examination Survey. The CDAI was calculated from vitamins A, C, E, selenium, zinc, and caretenoid through two rounds of 24-h dietary recall interviews. AAC was assessed by a lateral dual-energy x-ray absorptiometry scan of the thoraco-lumbar spine. The association between CDAI and AAC was evaluated with weighted multivariable logistic regression.

RESULTS

Overall, an unweighted 1081 participants were analyzed, including 110 with AAC and 971 without AAC. In the multivariable fully adjusted logistic regression model, CDAI was significantly associated with AAC (odds ratio = 0.89, 95% CI 0.81-0.98; P = 0.02). Compared with the lowest quartile, the highest quartile of CDAI was related to a 0.33-fold risk of AAC (95% CI 0.12-0.90; P = 0.03). Subgroup analysis showed that the significant association between CDAI and AAC was only observed in participants without hypertension (P for interaction = 0.002).

CONCLUSION

A higher CDAI was associated with a lower prevalence of AAC among adults without hypertension in the US. Further large-scale prospective studies are required to analyze the protective role of the CDAI in AAC progression.

Relationship between arginine methylation and vascular calcification

In patients on maintenance hemodialysis (MHD), vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD), which is the primary cause of death in chronic kidney disease (CKD). The main component of VC in CKD is the vascular smooth muscle cells (VSMCs). VC is an ordered, dynamic activity. Under the stresses of oxidative stress and calcium-‑phosphorus imbalance, VSMCs undergo osteogenic phenotypic transdifferentiation, which promotes the formation of VC. In addition to traditional epigenetics like RNA and DNA control, post-translational modifications have been discovered to be involved in the regulation of VC in recent years. It has been reported that the process of osteoblast differentiation is impacted by catalytic histone or non-histone arginine methylation. Its function in the osteogenic process is comparable to that of VC. Thus, we propose that arginine methylation regulates VC via many signaling pathways, including as NF-B, WNT, AKT/PI3K, TGF-/BMP/SMAD, and IL-6/STAT3. It might also regulate the VC-related calcification regulatory factors, oxidative stress, and endoplasmic reticulum stress. Consequently, we propose that arginine methylation regulates the calcification of the arteries and outline the regulatory mechanisms involved.

MicroRNAs regulate the vicious cycle of vascular calcification-osteoporosis in postmenopausal women

Menopause is a normal physiological process accompanied by changes in various physiological states. The incidence of vascular calcification (VC) increases each year after menopause and is closely related to osteoporosis (OP). Although many studies have investigated the links between VC and OP, the interaction mechanism of the two under conditions of estrogen loss remains unclear. MicroRNAs (miRNAs), which are involved in epigenetic modification, play a critical role in estrogen-mediated mineralization. In the past several decades, miRNAs have been identified as biomarkers or therapeutic targets in diseases. Thus, we hypothesize that these small molecules can provide new diagnostic and therapeutic approaches. In this review, we summarize the close interactions between VC and OP and the role of miRNAs in their interplay.

Oxidized phospholipid POVPC contributes to vascular calcification by triggering ferroptosis of vascular smooth muscle cells

Vascular calcification is an actively regulated biological process resembling bone formation, and osteogenic differentiation of vascular smooth muscle cells (VSMCs) plays a crucial role in this process. 1-Palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC), an oxidized phospholipid, is found in atherosclerotic plaques and has been shown to induce oxidative stress. However, the effects of POVPC on osteogenic differentiation and calcification of VSMCs have yet to be studied. In the present study, we investigated the role of POVPC in vascular calcification using in vitro and ex vivo models. POVPC increased mineralization of VSMCs and arterial rings, as shown by alizarin red staining. In addition, POVPC treatment increased expression of osteogenic markers Runx2 and BMP2, indicating that POVPC promotes osteogenic transition of VSMCs. Moreover, POVPC increased oxidative stress and impaired mitochondria function of VSMCs, as shown by increased ROS levels, impairment of mitochondrial membrane potential, and decreased ATP levels. Notably, ferroptosis triggered by POVPC was confirmed by increased levels of intracellular ROS, lipid ROS, and MDA, which were decreased by ferrostatin-1, a ferroptosis inhibitor. Furthermore, ferrostatin-1 attenuated POVPC-induced calcification of VSMCs. Taken together, our study for the first time demonstrates that POVPC promotes vascular calcification via activation of VSMC ferroptosis. Reducing the levels of POVPC or inhibiting ferroptosis might provide a novel strategy to treat vascular calcification.

Calcitriol combined with high-calcium and high-phosphorus diet induces vascular calcification model in chronic kidney disease rats

BACKGROUND

Cardiovascular diseases represent a significant complication arising from chronic kidney disease (CKD). Vascular calcification is an important risk factor for cardiovascular diseases. Reducing vascular calcification is therefore critical to reducing mortality in CKD patients.

HYPOTHESIS

This study aims to establish a vascular calcification model in rats with CKD by administering subcutaneous injections of calcitriol in combination with a high-calcium and high-phosphorus diet.

METHODS

The rats were divided into the CKD vascular calcification model group (subtotal nephrectomy+ [SNx+]) and the sham-operated control group (subtotal nephrectomy- [SNx-]). The rats in the SNx(+) group were administered high-calcium and high-phosphorus feeds following a 5/6 nephrectomy. Calcitriol (1 μg/kg, three times a week) was injected subcutaneously at weeks 0, 4, 8, and 12 after the operation. Measurements of body weight, urine, serum biochemical indicators and vascular calcification level were conducted in rats.

RESULTS

(1) Compared with the SNx(-) group, rats in the SNx(+) group experienced an increase in 24-h urine output, urinary phosphorus, and urinary microprotein excretion, along with the development of severe anemia. Additionally, there was a notable elevation in serum phosphorus, blood urea nitrogen, blood creatinine, fibroblast growth factor 23 (FGF-23), and intact parathyroid hormone levels, accompanied by severe hypoproteinemia at week 12. (2) The results of micro-compuyed tomography (μCT) and alizarin S staining of the thoracic aorta demonstrated an increase in vascular calcification in the SNx(+) group. (3) The expression levels of vascular calcification-related proteins were increased.

CONCLUSIONS

The administration of calcitriol combined with a high-calcium and high-phosphorus diet was found to induce vascular calcification in CKD rats, leading to a disturbance in mineral metabolism. Vascular calcification was effectively induced in CKD rats after 12 weeks of modeling, thereby presenting a novel approach for establishing a vascular calcification model in CKD rats, helping to elucidate this clinical condition and its underlying molecular mechanisms.

The emerging roles of irisin in vascular calcification

Vascular calcification is a common accompanying pathological change in many chronic diseases, which is caused by calcium deposition in the blood vessel wall and leads to abnormal blood vessel function. With the progress of medical technology, the diagnosis rate of vascular calcification has explosively increased. However, due to its mechanism's complexity, no effective drug can relieve or even reverse vascular calcification. Irisin is a myogenic cytokine regulating adipose tissue browning, energy metabolism, glucose metabolism, and other physiological processes. Previous studies have shown that irisin could serve as a predictor for vascular calcification, and protect against hypertension, diabetes, chronic kidney disease, and other risk factors for vascular calcification. In terms of mechanism, it improves vascular endothelial dysfunction and phenotypic transformation of vascular smooth muscle cells. All the above evidence suggests that irisin plays a predictive and protective role in vascular calcification. In this review, we summarize the association of irisin to the related risk factors for vascular calcification and mainly explore the role of irisin in vascular calcification.

Effect of magnesium on vascular calcification in chronic kidney disease patients: a systematic review and meta-analysis

PURPOSE

To evaluate the effects of magnesium (Mg) supplementation on vascular calcification (VC) in patients with chronic kidney disease (CKD).

METHODS

PubMed, Embase, Cochrane Library, Medline, Web of Science, CNKI, VIP, and WanFang databases were searched from build to July 2022. Randomized controlled trials (RCT) and non-RCT related to whether Mg supplementation inhibits VC in patients with CKD were included. The literature was screened according to inclusion and exclusion criteria, and quality evaluation and data collection were performed. Meta-analysis was performed using Review Manager 5.4 software.

RESULTS

8 RCTs and 1 non-RCT studies with a total of 496 patients were eventually included. Compared to control groups, Mg supplementation increased serum Mg levels (SMD = 1.26, 95% CI: -0.70 to 1.82, p < 0.001), but it was not statistically significant in alleviating the degree of VC, increasing T50, and reducing serum phosphorus (P) levels in patients with CKD (all p > 0.05). Oral Mg reduced left (WMD=-0.06, 95% CI. -0.11 to -0.01, p = 0.03) and right (WMD=-0.07, 95% CI: -0.13 to -0.01, p = 0.02) carotid intima-media thickness (cIMT). Additionally, calcium (Ca) (SMD=-0.43, 95% CI: -0.74 to -0.11, p = 0.008) and parathyroid hormone (PTH) (SMD=-0.43, 95% CI: -0.75 to -0.11, p = 0.008) levels were reduced by increasing dialysate Mg concentration.

CONCLUSIONS

Mg supplementation increased serum Mg levels and reduced Ca, PTH, and cIMT, but it did not reduce VC scores in patients with CKD. This still requires further studies with larger samples to evaluate the effect of Mg supplementation on VC.

Phenylacetylglutamine and trimethylamine N-oxide: Two uremic players, different actions

BACKGROUND

Chronic kidney disease (CKD) patients exhibit a heightened cardiovascular (CV) risk which may be partially explained by increased medial vascular calcification. Although gut-derived uremic toxin trimethylamine N-oxide (TMAO) is associated with calcium-phosphate deposition, studies investigating phenylacetylglutamine's (PAG) pro-calcifying potential are missing.

METHODS

The effect of TMAO and PAG in vascular calcification was investigated using 120 kidney failure patients undergoing living-donor kidney transplantation (LD-KTx), in an observational, cross-sectional manner. Uremic toxin concentrations were related to coronary artery calcification (CAC) score, epigastric artery calcification score, and markers of established non-traditional risk factors that constitute to the 'perfect storm' that drives early vascular aging in this patient population. Vascular smooth muscle cells were incubated with TMAO or PAG to determine their calcifying effects in vitro and analyse associated pathways by which these toxins may promote vascular calcification.

RESULTS

TMAO, but not PAG, was independently associated with CAC score after adjustment for CKD-related risk factors in kidney failure patients. Neither toxin was associated with epigastric artery calcification score; however, PAG was independently, positively associated with 8-hydroxydeoxyguanosine. Similarly, TMAO, but not PAG, promoted calcium-phosphate deposition in vitro, while both uremic solutes induced oxidative stress.

CONCLUSIONS

In conclusion, our translational data confirm TMAO's pro-calcifying effects, but both toxins induced free radical production detrimental to vascular maintenance. Our findings suggest these gut-derived uremic toxins have different actions on the vessel wall and therapeutically targeting TMAO may help reduce CV-related mortality in CKD.

Redox Metabolism and Vascular Calcification in Chronic Kidney Disease

Vascular calcification (VC) is a common complication in patients with chronic kidney disease which increases their mortality. Although oxidative stress is involved in the onset and progression of this disorder, the specific role of some of the main redox regulators, such as catalase, the main scavenger of H2O2, remains unclear. In the present study, epigastric arteries of kidney transplant recipients, a rat model of VC, and an in vitro model of VC exhibiting catalase (Cts) overexpression were analysed. Pericalcified areas of human epigastric arteries had increased levels of catalase and cytoplasmic, rather than nuclear runt-related transcription factor 2 (RUNX2). In the rat model, advanced aortic VC concurred with lower levels of the H2O2-scavenger glutathione peroxidase 3 compared to controls. In an early model of calcification using vascular smooth muscle cells (VSMCs), Cts VSMCs showed the expected increase in total levels of RUNX2. However, Cts VMSCs also exhibited a lower percentage of the nucleus stained for RUNX2 in response to calcifying media. In this early model of VC, we did not observe a dysregulation of the mitochondrial redox state; instead, an increase in the general redox state was observed in the cytoplasm. These results highlight the complex role of antioxidant enzymes as catalase by regulation of RUNX2 subcellular location delaying the onset of VC.

Vascular calcification in CKD: New insights into its mechanisms

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD) and contributes to an increased risk of cardiovascular morbidity and mortality. However, effective therapies are still unavailable at present. It has been well established that VC associated with CKD is not a passive process of calcium phosphate deposition, but an actively regulated and cell-mediated process that shares many similarities with bone formation. Additionally, numerous studies have suggested that CKD patients have specific risk factors and contributors to the development of VC, such as hyperphosphatemia, uremic toxins, oxidative stress and inflammation. Although research efforts in the past decade have greatly improved our knowledge of the multiple factors and mechanisms involved in CKD-related VC, many questions remain unanswered. Moreover, studies from the past decade have demonstrated that epigenetic modifications abnormalities, such as DNA methylation, histone modifications and noncoding RNAs, play an important role in the regulation of VC. This review seeks to provide an overview of the pathophysiological and molecular mechanisms of VC associated with CKD, mainly focusing on the involvement of epigenetic modifications in the initiation and progression of uremic VC, with the aim to develop promising therapies for CKD-related cardiovascular events in the future.

Overview of multifunctional cysteinyl cathepsins in atherosclerosis-based cardiovascular disease: from insights into molecular functions to clinical implications

Cysteinyl cathepsins (CTSs) are widely known to have a proteolysis function that mediates recycling of unwanted proteins in endosomes and lysosomes, and investigation of CTSs has greatly improved with advances in live-imaging techniques both in vivo and in vitro, leading to three key findings. (1) CTSs are relocated from the lysosomes to other cellular spaces (i.e., cytosol, nucleus, nuclear membrane, plasma membrane, and extracellular milieu). (2) In addition to acidic cellular compartments, CTSs also exert biological activity in neutral environments. (3) CTSs also exert multiple nontraditional functions in, for example, extracellular matrix metabolism, cell signaling transduction, protein processing/trafficking, and cellular events. Various stimuli regulate the expression and activities of CTSs in vivo and vitro-e.g., inflammatory cytokines, oxidative stress, neurohormones, and growth factors. Accumulating evidence has confirmed the participation of CTSs in vascular diseases characterized by atherosclerosis, plaque rupture, thrombosis, calcification, aneurysm, restenosis/in-stent-restenosis, and neovasel formation. Circulating and tissue CTSs are promising as biomarkers and as a diagnostic imaging tool in patients with atherosclerosis-based cardiovascular disease (ACVD), and pharmacological interventions with their specific and non-specific inhibitors, and cardiovascular drugs might have potential for the therapeutic targeting of CTSs in animals. This review focuses on the update findings on CTS biology and the involvement of CTSs in the initiation and progression of ACVD and discusses the potential use of CTSs as biomarkers and small-molecule targets to prevent deleterious nontraditional functions in ACVD.

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

Fibroblast growth factor 21 inhibits vascular calcification by ameliorating oxidative stress of vascular smooth muscle cells

Vascular calcification is very common in clinical. Severe vascular calcification is related to the occurrence of adverse events. Oxidative stress (OS) plays a pathophysiological role in the formation of vascular calcification. Previous studies have demonstrated that fibroblast growth factor 21(FGF21) could inhibit vascular calcification both in vivo and in vitro. FGF21 has also been proved to promote the recovery of superoxide dismutase (SOD) and thereby alleviate OS. Thus, our assumption was that FGF21 inhibit vascular calcification partly by restoring the level of antioxidant SOD and reducing OS. In this study, we established the vascular calcification by 5/6 nephrectomy plus high phosphate diet chronic kidney disease (CKD) model. The results showed the receptor of FGF21, fibroblast growth factor receptor 1 (FGFR1) and βKlotho in the aorta increased in CKD group, and mainly located in the media of the artery. Ulteriorly, immunofluorescence (IF) and IHC staining showed that FGFR1 and βKlotho mainly existed in arterial vascular smooth muscle cells (VSMCs). When FGF21 was knock out, the calcification was more severe in FGF21 KO + CKD mice, compared to wild type (WT)+ CKD mice. The transcriptional level of vascular calcification-related genes was significantly higher in FGF21 KO mice than control group. The dihydroethidium (DHE) staining reactive oxygen species (ROS) level in the CKD group was higher compared to the control group, but lower in FGF21 KO + CKD group, and the transcriptional level of SOD1 and SOD2 in FGF21 KO + CKD group was significantly higher than that in CKD group. In conclusion, FGF21 could inhibit vascular calcification, partly by restoring the level of antioxidant SOD and reducing vascular oxidative stress. This study provides further evidence for FGF21 as a candidate drug for cardiovascular protective agents.

Inhibition of mitochondrial phosphate carrier prevents high phosphate-induced superoxide generation and vascular calcification

Vascular calcification is a serious complication of hyperphosphatemia that causes cardiovascular morbidity and mortality. Previous studies have reported that plasmalemmal phosphate (Pi) transporters, such as PiT-1/2, mediate depolarization, Ca²⁺ influx, oxidative stress, and calcific changes in vascular smooth muscle cells (VSMCs). However, the pathogenic mechanism of mitochondrial Pi uptake in vascular calcification associated with hyperphosphatemia has not been elucidated. We demonstrated that the phosphate carrier (PiC) is the dominant mitochondrial Pi transporter responsible for high Pi-induced superoxide generation, osteogenic gene upregulation, and calcific changes in primary VSMCs isolated from rat aortas. Notably, acute incubation with high Pi markedly increased the protein abundance of PiC via ERK1/2- and mTOR-dependent translational upregulation. Genetic suppression of PiC prevented Pi-induced ERK1/2 activation, superoxide production, osteogenic differentiation, and vascular calcification of VSMCs in vitro and aortic rings ex vivo. Pharmacological inhibition of mitochondrial Pi transport using butyl malonate (BMA) or mersalyl abolished all pathologic changes involved in high Pi-induced vascular calcification. BMA or mersalyl also effectively prevented osteogenic gene upregulation and calcification of aortas from 5/6 subtotal nephrectomized mice fed a high-Pi diet. Our results suggest that mitochondrial Pi uptake via PiC is a critical molecular mechanism mediating mitochondrial superoxide generation and pathogenic calcific changes, which could be a novel therapeutic target for treating vascular calcification associated with hyperphosphatemia.

The association of renal impairment with different patterns of intracranial arterial calcification: Intimal and medial calcification

BACKGROUND AND AIMS

Increasing knowledge about calcification together with improved imaging techniques provided evidence that intracranial arterial calcification (IAC) can be divided into two distinct entities: intimal and medial calcification. The purpose of this study was to investigate the association between kidney function and the two patterns of IAC, which could clarify the underlying mechanisms of intimal or medial calcification and its clinical consequence.

METHODS

A total of 516 participants were enrolled in this study. Kidney function was assessed using the estimated glomerular filtration rate (eGFR) based on modified glomerular filtration rate estimating equation. The degree of IAC measured by IAC scores was evaluated on non-contrast head computed tomography (CT) images and IAC was classified as intimal or medial calcification. Associations of kidney function with IAC scores and patterns were assessed sing multivariate logistic regression analysis.

RESULTS

In 440 patients (85.27%) with IAC, 189 (42.95%) had predominant intimal calcifications and 251 (57.05%) had predominant medial calcifications. Multivariate analysis revealed that lower eGFR level (eGFR <60 ml/min/1.73 m²) was associated with higher IAC scores (odds ratio [OR] 2.01; 95% confidence interval [CI], 1.50-2.71; p < 0.001). Medial calcification was more frequent in the lower eGFR group (eGFR <60 ml/min/1.73 m²) compared to the other two groups with eGFR 60 to 89 and eGFR >90 ml/min/1.73 m² (78.72% vs. 53.65%, p < 0.001; 78.72% vs. 47.78%, p < 0.001). In multivariable analysis, impaired kidney function was associated with an increased odds of medial calcification presence in patients with eGFR <60 ml/min/1.73 m² (OR, 1.47; 95% CI, 1.05 to 2.06).

CONCLUSIONS

Our findings demonstrated that impaired renal function was independently associated with a higher degree of calcification in intracranial arteries, especially medial calcification, which reflects a distinction between two types of arterial calcification and raise the possibility for specific prevention of lesion formation.

Association of oxidative stress with erectile dysfunction in community-dwelling men and men on dialysis

OBJECTIVES

To investigate the association between oxidative stress and erectile dysfunction (ED) in community-dwelling men and men on dialysis.

METHODS

This cross-sectional study included 398 community-dwelling men and 42 men on dialysis. Oxidative stress was assessed using 8-hydroxy-2'-deoxyguanosine (8-OHdG). Univariable and multivariable logistic regression analyses were performed to evaluate the association between oxidative stress and ED.

RESULTS

Spearman's rank correlation test showed no significant correlation between urine 8-OHdG levels and the 5-Item International Index of Erectile Function scores in community-dwelling men (ρ = -0.005, p = 0.917) and between plasma 8-OHdG levels and the Sexual Health Inventory for Men scores in men on dialysis (ρ = 0.166, p = 0.295). In community-dwelling men, univariable and multivariable analyses revealed that urine 8-OHdG level was not significantly associated with ED (odds ratio [OR]: 1.005, 95% confidence interval [CI]: 0.884-1.144, p = 0.934; OR: 0.930, 95% CI: 0.798-1.084, p = 0.353; respectively). In men on dialysis, univariable analyses revealed that plasma 8-OHdG level was not significantly associated with severe ED (OR: 0.967, 95% CI: 0.876-1.066, p = 0.498).

CONCLUSIONS

Oxidative stress was not significantly associated with ED prevalence and severity in community-dwelling men and men on dialysis.

Repression of the antiporter SLC7A11/glutathione/glutathione peroxidase 4 axis drives ferroptosis of vascular smooth muscle cells to facilitate vascular calcification

Vascular calcification is a common pathologic condition in patients with chronic kidney disease (CKD). Cell death such as apoptosis plays a critical role in vascular calcification. Ferroptosis is a type of iron-catalyzed and regulated cell death resulting from excessive iron-dependent reactive oxygen species and lipid peroxidation. However, it is unclear whether ferroptosis of vascular smooth muscle cells (VSMCs) regulates vascular calcification in CKD. Our results showed that high calcium and phosphate concentrations induced ferroptosis in rat VSMCs in vitro. Inhibition of ferroptosis by ferrostatin-1 dose-dependently reduced mineral deposition in rat VSMCs under pro-osteogenic conditions, as indicated by alizarin red staining and quantification of calcium content. In addition, gene expression analysis revealed that ferrostatin-1 inhibited osteogenic differentiation of rat VSMCs. Similarly, ferrostatin-1 remarkably attenuated calcification of rat and human arterial rings ex vivo and aortic calcification in vitamin D₃-overloaded mice in vivo. Moreover, inhibition of ferroptosis by either ferrostatin-1 or deferoxamine attenuated aortic calcification in rats with CKD. Mechanistically, high calcium and phosphate downregulated expression of SLC7A11 (a cystine-glutamate antiporter), and reduced glutathione (GSH) content in VSMCs. Additionally, GSH depletion induced by erastin (a small molecule initiating ferroptotic cell death) significantly promoted calcification of VSMCs under pro-osteogenic conditions, whereas GSH supplement by N-acetylcysteine reduced calcification of VSMCs. Consistently, knockdown of SLC7A11 by siRNA markedly promoted VSMC calcification. Furthermore, high calcium and phosphate downregulated glutathione peroxidase 4 (GPX4) expression, and reduced glutathione peroxidase activity. Inhibition of GPX4 by RSL3 promoted VSMC calcification. Thus, repression of the SLC7A11/GSH/GPX4 axis triggers ferroptosis of VSMCs to promote vascular calcification under CKD conditions, providing a novel targeting strategy for vascular calcification.

Mineral Bone Disorders in Kidney Disease Patients: The Ever-Current Topic

Chronic kidney disease (CKD) is a complex and multifactorial disease, and one of the most prevalent worldwide. Chronic kidney disease–mineral bone disorders (CKD–MBD) with biochemical and hormonal alterations are part of the complications associated with the progression of CKD. Pathophysiology of CKD–MBD focused on abnormalities in serum levels of several biomarkers (such as FGF-23, klotho, phosphate, calcium, vitamin D, and PTH) which are discussed in this review. We therefore examine the prognostic association between CKD–MBD and the increased risk for cardiovascular events, mortality, and CKD progression to end-stage kidney disease (ESKD). Lastly, we present specific treatments acting on CKD to prevent and treat the complications associated with secondary hyperparathyroidism (SHPT): control of hyperphosphatemia (with dietary restriction, intestinal phosphate binders, and adequate dialysis), the use of calcimimetic agents, vitamin D, and analogues, and the use of bisphosphonates or denosumab in patients with osteoporosis.

Downregulation of HDAC9 by the ketone metabolite β-hydroxybutyrate suppresses vascular calcification

Vascular calcification is an actively regulated process resembling bone formation and contributes to the cardiovascular morbidity and mortality of chronic kidney disease (CKD). However, effective therapy for vascular calcification is still lacking. The ketone body β-hydroxybutyrate (BHB) has been demonstrated to have health-promoting effects including anti-inflammation and cardiovascular protective effects. However, whether BHB protects against vascular calcification in CKD remains unclear. In this study, Alizarin Red staining and calcium content assay showed that BHB reduced calcification of vascular smooth muscle cells (VSMCs) and arterial rings. Of note, compared with CKD patients without thoracic calcification, serum BHB levels were lower in CKD patients with thoracic calcification. Supplementation with 1,3-butanediol (1,3-B), the precursor of BHB, attenuated aortic calcification in CKD rats and VitD3-overloaded mice. Furthermore, RNA-Seq analysis revealed that BHB downregulated HDAC9, which was further confirmed by RT-qPCR and western blot analysis. Both pharmacological inhibition and knockdown of HDAC9 attenuated calcification of human VSMCs, while overexpression of HDAC9 exacerbated calcification of VSMCs and aortic rings, indicating that HDAC9 promotes vascular calcification under CKD conditions. Of note, BHB treatment antagonized HDAC9-induced vascular calcification. In addition, HDAC9 overexpression activated NF-κB signaling pathway and inhibition of NF-κB attenuated HDAC9-induced VSMC calcification, suggesting that HDAC9 promotes vascular calcification via activation of NF-κB. In conclusion, our study demonstrates that BHB supplementation inhibits vascular calcification in CKD via modulation of the HDAC9-dependent NF-κB signaling pathway. Moreover, we unveil a crucial mechanistic role of HDAC9 in vascular calcification under CKD conditions, thus nutritional intervention or pharmacological approaches to enhance BHB levels could act as promising therapeutic strategies to target HDAC9 for the treatment of vascular calcification in CKD. This article is protected by copyright. All rights reserved.

Ferroptosis: A Potential Therapeutic Target in Acute Kidney Injury

Ferroptosis is a recently recognized form of nonapoptotic cell death that is triggered by reactive oxidative species (ROS) due to iron overload, lipid peroxidation accumulation, or the inhibition of phospholipid hydroperoxidase glutathione peroxidase 4 (GPX4). Recent studies have reported that ferroptosis plays a vital role in the pathophysiological process of multiple systems such as the nervous, renal, and pulmonary systems. In particular, the kidney has higher rates of O₂ consumption in its mitochondria than other organs; therefore, it is susceptible to imbalances between ROS and antioxidants. In ischemia/reperfusion (I/R) injury, which is damage caused by the restoring blood flow to ischemic tissues, the release of ROS and reactive nitrogen species is accelerated and contributes to subsequent inflammation and cell death, such as ferroptosis, as well as apoptosis and necrosis being induced. At the same time, I/R injury is one of the major causes of acute kidney injury (AKI), causing significant morbidity and mortality. This review highlights the current knowledge on the involvement of ferroptosis in AKI via oxidative stress.

Vascular Calcification in Chronic Kidney Disease: An Update and Perspective

Chronic kidney disease is a devastating condition resulting from irreversible loss of nephron numbers and function and leading to end-stage renal disease and mineral disorders. Vascular calcification, an ectopic deposition of calcium-phosphate salts in blood vessel walls and heart valves, is an independent risk factor of cardiovascular morbidity and mortality in chronic kidney disease. Moreover, aging and related metabolic disorders are essential risk factors for chronic kidney disease and vascular calcification. Marked progress has been recently made in understanding and treating vascular calcification in chronic kidney disease. However, there is a paucity of systematic reviews summarizing this progress, and investigating unresolved issues is warranted. In this systematic review, we aimed to overview the underlying mechanisms of vascular calcification in chronic kidney diseases and discuss the impact of chronic kidney disease on the pathophysiology of vascular calcification. Additionally, we summarized potential clinical diagnostic biomarkers and therapeutic applications for vascular calcification with chronic kidney disease. This review may offer new insights into the pathogenesis, diagnosis, and therapeutic intervention of vascular calcification.

Potential Actions of Baicalein for Preventing Vascular Calcification of Smooth Muscle Cells In Vitro and In Vivo

Vascular calcification (VC) is associated with cardiovascular disease. Baicalein, a natural flavonoid extract of Scutellaria baicalensis rhizome has several biological properties which may inhibit VC. We investigated whether baicalein suppresses Runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 2 (BMP-2) and upregulates smooth muscle 22-alpha (SM22-α) and alpha-smooth muscle actin (α-SMA). In an in vitro experiment, primary rat aortic vascular smooth muscle cells (VSMCs) were pretreated with 0.1, 1, and 5 μM baicalein, followed by β-glycerophosphate (β-GP) to induce calcification. In an in vivo experiment, VC was generated by vitamin D3 plus nicotine (VDN) administration to male Sprague Dawley (SD) rats randomly assigned into a control group, a VC group, a VC group pretreated with baicalein, and a baicalein alone group. Each group comprised 10 rats. Left ventricular (LV) morphology, function and performance were assessed by echocardiography. Calcium content was measured by Alizarin red S staining and alkaline phosphatase (ALP) activity assays. Apoptotic VSMCs were detected by flow cytometry. Protein levels and superoxide changes were evaluated using Western blotting and immunofluorescence assays respectively. Plasma malondialdehyde (MDA) was assayed. Baicalein pretreatment significantly reduced calcium content in calcified VSMCs (p < 0.001) as well as in VC rat aortic smooth muscle (p < 0.001). Additionally, ALP activity was decreased in calcified VSMCs and VC rat aortic smooth muscle (p < 0.001). Apoptosis was significantly attenuated by 1 μM baicalein pretreatment in calcified VSMCs. Runx2 and BMP-2 expressions were downregulated by the baicalein in calcified VSMCs. Baicalein pretreatment increased typical VSMCs markers SM22-α and α-SMA in calcified VSMCs. Baicalein pretreatment was associated with adverse changes in LV morphometry. Markers of oxidative stress declined, and endogenous antioxidants increased in VC rats pretreated with baicalein. Baicalein mitigates VC through the inhibition of Runx2/BMP-2 signaling pathways, enhancement of vascular contractile phenotype and oxidative stress reduction. However, our study is of basic experimental design; more advanced investigations to identify other molecular regulators of VC and their mechanisms of action is required.

Ubiquitin-specific protease 47 is associated with vascular calcification in chronic kidney disease by regulating osteogenic transdifferentiation of vascular smooth muscle cells

Chronic kidney disease (CKD) has recently become a serious health and social concern. Vascular calcification, a common complication of CKD, is a risk factor that increases the incidence and mortality of cardiovascular events in patients with CKD. However, there are currently no effective therapeutic targets that can facilitate treatment with fewer side effects for vascular calcification in CKD. To identify potential therapeutic targets, we performed label-free quantification (LFQ) analyses of protein samples from rat aortic vascular smooth muscle cells (RASMCs) after high-phosphorus treatment by nano-UPLC-MS/MS. We determined that ubiquitin-specific protease 47 (USP47) may be associated with CKD vascular calcification by regulating the osteogenic transdifferentiation of the vascular smooth muscle cell (VSMC) phenotype, thus suggesting a novel and potentially effective therapeutic target for CKD vascular calcification. USP47 knockdown significantly reduced the expression of β-transducin repeat-containing protein (BTRC), serine/threonine-protein kinase akt-1 (AKT1), Klotho, fibroblast growth factor (FGF23), and matrix Gla protein (MGP) in RASMCs after high-phosphorus treatment. Consistent with the results of protein-protein interaction (PPI) analyses, USP47 may be involved in regulating osteogenic transdifferentiation markers, such as runt-related transcription factor 2 (RUNX2), Klotho, FGF23, and MGP through the BTRC/AKT1 pathway upon CKD vascular calcification. These data indicate that USP47 may be associated with vascular calcification in CKD by regulating osteogenic differentiation of VSMCs. USP47 may regulate osteogenic transdifferentiation in VSMCs upon CKD vascular calcification through a process involving the BTRC/AKT1 pathway. This study identified a novel potential therapeutic target for the treatment of vascular calcification in CKD.

Irisin protects against vascular calcification by activating autophagy and inhibiting NLRP3-mediated vascular smooth muscle cell pyroptosis in chronic kidney disease

Irisin protects the cardiovascular system against vascular diseases. However, its role in chronic kidney disease (CKD) -associated vascular calcification (VC) and the underlying mechanisms remain unclear. In the present study, we investigated the potential link among Irisin, pyroptosis, and VC under CKD conditions. During mouse vascular smooth muscle cell (VSMC) calcification induced by β-glycerophosphate (β-GP), the pyroptosis level was increased, as evidenced by the upregulated expression of pyroptosis-related proteins (cleaved CASP1, GSDMD-N, and IL1B) and pyroptotic cell death (increased numbers of PI-positive cells and LDH release). Reducing the pyroptosis levels by a CASP1 inhibitor remarkably decreased calcium deposition in β-GP-treated VSMCs. Further experiments revealed that the pyroptosis pathway was activated by excessive reactive oxygen species (ROS) production and subsequent NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in calcified VSMCs. Importantly, Irisin effectively inhibited β-GP-induced calcium deposition in VSMCs in vitro and in mice aortic rings ex vivo. Overexpression of Nlrp3 attenuated the suppressive effect of Irisin on VSMC calcification. In addition, Irisin could induce autophagy and restore autophagic flux in calcified VSMCs. Adding the autophagy inhibitor 3-methyladenine or chloroquine attenuated the inhibitory effect of Irisin on β-GP-induced ROS production, NLRP3 inflammasome activation, pyroptosis, and calcification in VSMCs. Finally, our in vivo study showed that Irisin treatment promoted autophagy, downregulated ROS level and thereby suppressed pyroptosis and medial calcification in aortic tissues of adenine-induced CKD mice. Together, our findings for the first time demonstrated that Irisin protected against VC via inducing autophagy and inhibiting VSMC pyroptosis in CKD, and Irisin might serve as an effective therapeutic agent for CKD-associated VC.

Bone marrow mesenchymal stem cell-derived exosomal microRNA-381-3p alleviates vascular calcification in chronic kidney disease by targeting NFAT5

Vascular calcification (VC) is a significant complication of chronic kidney disease (CKD) and cellular apoptosis is one of the intricate mechanisms of VC. Bone marrow mesenchymal stem cell-derived exosome (BMSC-Exo) alleviates VC, but the mechanism remains unclear. We investigated the mechanism of BMSC-Exo using high phosphate stimulated Human aortic smooth muscle cells (HA-VSMCs) and 5/6 subtotal nephrectomy (SNx) rat models. We demonstrated that the effect of BMSC-Exo on the inhibition of cellular apoptosis and calcification partially depended on exosomal microRNA-381-3p (miR-381-3p) both in vivo and in vitro, and confirmed that miR-381-3p could inhibit Nuclear Factor of Activated T cells 5 (NFAT5) expression by directly binding to its 3′ untranslated region. Additionally, we found that severe calcification of arteries in dialysis patients was associated with decreased miR-381-3p and increased NFAT5 expression levels. Collectively, our findings proved that BMSC-Exo plays anti-calcification and anti-apoptosis roles in CKD by delivering enclosed miR-381-3p, which directly targets NFAT5 mRNA, and leads to a better understanding of the mechanism of CKD-VC.

Oxidative Stress Related to Plasmalemmal and Mitochondrial Phosphate Transporters in Vascular Calcification

Inorganic phosphate (Pi) is essential for maintaining cellular function but excess of Pi leads to serious complications, including vascular calcification. Accumulating evidence suggests that oxidative stress contributes to the pathogenic progression of calcific changes. However, the molecular mechanism underlying Pi-induced reactive oxygen species (ROS) generation and its detrimental consequences remain unclear. Type III Na⁺-dependent Pi cotransporter, PiT-1/-2, play a significant role in Pi uptake of vascular smooth muscle cells. Pi influx via PiT-1/-2 increases the abundance of PiT-1/-2 and depolarization-activated Ca²⁺ entry due to its electrogenic properties, which may lead to Ca²⁺ and Pi overload and oxidative stress. At least four mitochondrial Pi transporters are suggested, among which the phosphate carrier (PiC) is known to be mainly involved in mitochondrial Pi uptake. Pi transport via PiC may induce hyperpolarization and superoxide generation, which may lead to mitochondrial dysfunction and endoplasmic reticulum stress, together with generation of cytosolic ROS. Increase in net influx of Ca²⁺ and Pi and their accumulation in the cytosol and mitochondrial matrix synergistically increases oxidative stress and osteogenic differentiation, which could be prevented by suppressing either Ca²⁺ or Pi overload. Therapeutic strategies targeting plasmalemmal and mitochondrial Pi transports can protect against Pi-induced oxidative stress and vascular calcification.

NRF2-suppressed vascular calcification by regulating the antioxidant pathway in chronic kidney disease

Vascular calcification (VC), in which vascular smooth muscle cells (VSMCs) undergo differentiation and osteogenic transition, is a common complication of chronic kidney disease (CKD). Recent findings show that nuclear factor-erythroid-2-related factor 2 (NRF2) is an evolutionarily conserved antioxidant and beneficial in preventing vascular senescence and calcification. The roles of NRF2 in the initiation and progression of VC in CKD still need further investigation. CKD-associated VC model rats exhibited significant upregulation of NRF2, NAD(P)H: quinone oxidoreductase-1 (NQO1), osteogenic markers such as alkaline phosphatase (ALP), runt-related transcription factor-2 (RUNX2) and osteopontin (OPN), and β-catenin compared to CKD rats. Immunohistochemistry further verified these results. In addition, rat aortic VSMCs were isolated and subjected to four treatments: normal control, phosphorus-induced (Pi), Pi + NRF2 activator DMF, and Pi + NRF2 inhibitor ML385. The reactive oxygen species (ROS) generation, malondialdehyde (MDA) content, and calcium deposition of the four treatments were determined. The mRNA and protein expression levels of NRF2, NQO1, and haem oxygenase 1 (HO1) and the osteogenic markers ALP, Runx1, OPN, bone morphogenetic protein 2 (BMP2), and β-catenin were quantified by RT-PCR and western blotting. VSMC apoptosis was calculated by flow cytometry. The in vitro results suggested that intracellular oxidative stress and calcification were closely associated with NRF2 activity and that the activation of NRF2 could significantly suppress osteogenic transition and apoptosis in VSMCs. Thus, this study indicated that the NRF2-related antioxidant pathway can positively respond to and protect against the initiation and progression of VC in CKD by reducing oxidative stress. This study may contribute insights facilitating the application of the NRF2 antioxidative system as a therapeutic treatment for vascular diseases such as CKD.

Vascular Calcification in Chronic Kidney Disease: Distinct Features of Pathogenesis and Clinical Implication

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and leads to increased cardiovascular morbidity and mortality. In patients with CKD, traditional factors do not fully explain the high prevalence of VC. This suggests that a CKD-specific pathobiology is involved in the development of VC and mounting evidence indicates that VC in CKD patients has distinct features of clinical presentation and that clinical implications are changed compared to those in the general population. In this review, we discuss the mechanism, diagnostic imaging modalities, clinical features and implications, and management of VC in patients with CKD.

Chronic kidney disease (CKD) is associated with a higher prevalence of vascular calcification (VC) and cardiovascular disease. VC in CKD patients showed different pathophysiological features from those of the general population. The pathogenesis of VC in CKD is a highly organized process, and prior studies have suggested that patients with CKD have their own specific contributors to the phenotypic change of vascular smooth muscle cells (VSMCs), including uremic toxins, CKD-mineral and bone disease (CKD-MBD), inflammation, and oxidative stress. For the diagnosis and monitoring of VC in CKD, several imaging modalities, including plain radiography, ultrasound, and computed tomography have been utilized. VC in CKD patients has distinct clinical features and implications. CKD patients revealed a more intense and more prevalent calcification on the intimal and medial layers, whereas intimal calcification is predominantly observed in the general population. While a higher VC score is clearly associated with a higher risk of all-cause mortality and cardiovascular events, a greater VC score in CKD patients does not fully reflect the burden of atherosclerosis, because they have more calcification at equal volumes of atheromatous plaques. The primary goal of VC treatment in CKD is the prevention of VC progression, and the main management is to control the biochemical components of CKD-MBD. Cinacalcet and non-calcium-containing phosphate binders are the mainstay of VC prevention in CKD-MBD management. VC in patients with CKD is an ongoing area of research and is expected to advance soon.

Chronic kidney disease measures for cardiovascular risk prediction

Chronic kidney disease (CKD) affects 15-20% of adults globally and causes various complications, one of the most important being cardiovascular disease (CVD). CKD has been associated with many CVD subtypes, especially severe ones like heart failure, independent of potential confounders such as diabetes and hypertension. There is no consensus in major clinical guidelines as to how to incorporate the two key measures of CKD (glomerular filtration rate and albuminuria) for CVD risk prediction. This is a critical missed opportunity to appropriately refine predicted risk and personalize prevention therapies according to CKD status, particularly since these measures are often already evaluated in clinical care. In this review, we provide an overview of CKD definition and staging, the subtypes of CVD most associated with CKD, major pathophysiological mechanisms, and the current state of CKD as a predictor of CVD in major clinical guidelines. We will introduce the novel concept of a "CKD Add-on", which allows the incorporation of CKD measures in existing risk prediction models, and the implications of taking into account CKD in the management of CVD risk.

Up-regulation of heme oxygenase-1 by celastrol alleviates oxidative stress and vascular calcification in chronic kidney disease

Vascular calcification is very commonly observed in patients with chronic kidney disease (CKD), but there is no efficient therapy available. Oxidative stress plays critical roles in the progression of vascular calcification. Celastrol (Cel), a natural constituent derived from Chinese herbals, exhibits anti-oxidative stress activity. Here, we investigated the effect of celastrol on vascular calcification using vascular smooth muscle cells (VSMCs), arterial rings and CKD rats. Alizarin red staining and gene expression analysis showed that Cel dose-dependently inhibited rat VSMC calcification and osteogenic differentiation. Similarly, ex vivo study revealed that Cel inhibited calcification of rat and human arterial rings. In addition, micro-computed tomography, alizarin red staining and calcium content analysis confirmed that Cel inhibited aortic calcification in CKD rats. Interestingly, Cel treatment increased the mRNA and protein levels of heme oxygenase-1 (HMOX-1), and reduced the levels of reactive oxygen species (ROS) in VSMCs. Furthermore, both pharmacological inhibition of HMOX-1 and knockdown of HMOX-1 by siRNA independently counteracted the inhibitory effect of Cel on vascular calcification. Moreover, knockdown of HMOX-1 prevented Cel treatment-mediated reduction in ROS levels. Finally, Cel treatment reduced Vitamin D3-induced aortic calcification in mice and this effect was blocked by HMOX-1 inhibitor ZnPP9. Collectively, our results suggest that up-regulation of HMOX-1 is required for the inhibitory effect of Cel on vascular calcification. Modulation of HMOX-1 may provide a novel strategy for the treatment of vascular calcification in CKD.

Mitochondria Homeostasis and Vascular Medial Calcification

Vascular calcification occurs highly prevalent, which commonly predicts adverse cardiovascular events. The pathogenesis of calcification, a complicated and multifactorial process, is incompletely characterized. Accumulating evidence shows that mitochondrial dysfunction may ultimately be more detrimental in the vascular smooth muscle cells (VSMCs) calcification. This review summarizes the role of mitochondrial dysfunction and metabolic reprogramming in vascular calcification, and indicates that metabolic regulation may be a therapeutic target in vascular calcification.

Human Vascular Smooth Muscle Function and Oxidative Stress Induced by NADPH Oxidase with the Clinical Implications

Among reactive oxygen species, superoxide mediates the critical vascular redox signaling, resulting in the regulation of the human cardiovascular system. The reduced form of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase, NOX) is the source of superoxide and relates to the crucial intracellular pathology and physiology of vascular smooth muscle cells, including contraction, proliferation, apoptosis, and inflammatory response. Human vascular smooth muscle cells express NOX1, 2, 4, and 5 in physiological and pathological conditions, and those enzymes play roles in most cardiovascular disorders caused by hypertension, diabetes, inflammation, and arteriosclerosis. Various physiologically active substances, including angiotensin II, stimulate NOX via the cytosolic subunits’ translocation toward the vascular smooth muscle cell membrane. As we have shown, some pathological stimuli such as high glucose augment the enzymatic activity mediated by the phosphatidylinositol 3-kinase-Akt pathway, resulting in the membrane translocation of cytosolic subunits of NOXs. This review highlights and details the roles of human vascular smooth muscle NOXs in the pathophysiology and clinical aspects. The regulation of the enzyme expressed in the vascular smooth muscle cells may lead to the prevention and treatment of human cardiovascular diseases.

Extracellular Inorganic Phosphate-Induced Release of Reactive Oxygen Species: Roles in Physiological Processes and Disease Development

Inorganic phosphate (Pi) is an essential nutrient for living organisms and is maintained in equilibrium in the range of 0.8-1.4 mM Pi. Pi is a source of organic constituents for DNA, RNA, and phospholipids and is essential for ATP formation mainly through energy metabolism or cellular signalling modulators. In mitochondria isolated from the brain, liver, and heart, Pi has been shown to induce mitochondrial reactive oxygen species (ROS) release. Therefore, the purpose of this review article was to gather relevant experimental records of the production of Pi-induced reactive species, mainly ROS, to examine their essential roles in physiological processes, such as the development of bone and cartilage and the development of diseases, such as cardiovascular disease, diabetes, muscle atrophy, and male reproductive system impairment. Interestingly, in the presence of different antioxidants or inhibitors of cytoplasmic and mitochondrial Pi transporters, Pi-induced ROS production can be reversed and may be a possible pharmacological target.

Age- and sex-specific reference intervals for superoxide dismutase enzyme and several minerals in a healthy adult cohort

Introduction

The aim of this study was to establish RIs for clinically important markers including superoxide dismutase (SOD), serum copper, zinc, calcium, magnesium, and phosphate in a cohort of healthy Iranian adults.

Materials

A subsample from MASHAD cohort study was used to assess serum SOD, copper, zinc, calcium, magnesium and phosphate. Serum SOD was measured according to its inhibitory potential of pyrogallol oxidation. Micro‐ and macro‐minerals were measured using flame atomic absorption spectrometry and a BT3000 autoanalyzer, respectively. Sex‐ and age‐specific RIs were then calculated based on CLSI Ep28‐A3 guidelines.

Results

Reference value distributions for studied parameters did not demonstrate any age‐specific differences that were statistically significant. In addition, sex partitioning was not required for all parameters, apart from serum magnesium, which showed a wider range in females (0.81–1.26 mg/dl) compared with males (0.82–1.23 mg/dl).

Conclusion

The RIs established in this study can be expected to improve mineral assessment and clinical decision‐making in the Iranian adult population.

Vascular Calcification Mechanisms: Updates and Renewed Insight into Signaling Pathways Involved in High Phosphate-Mediated Vascular Smooth Muscle Cell Calcification

Vascular calcification (VC) is associated with aging, cardiovascular and renal diseases and results in poor morbidity and increased mortality. VC occurs in patients with chronic kidney disease (CKD), a condition that is associated with high serum phosphate (Pi) and severe cardiovascular consequences. High serum Pi level is related to some pathologies which affect the behaviour of vascular cells, including platelets, endothelial cells (ECs) and smooth muscle cells (SMCs), and plays a central role in promoting VC. VC is a complex, active and cell-mediated process involving the transdifferentiation of vascular SMCs to a bone-like phenotype, systemic inflammation, decreased anti-calcific events (loss of calcification inhibitors), loss in SMC lineage markers and enhanced pro-calcific microRNAs (miRs), an increased intracellular calcium level, apoptosis, aberrant DNA damage response (DDR) and senescence of vascular SMCs. This review gives a brief overview of the current knowledge of VC mechanisms with a particular focus on Pi-induced changes in the vascular wall important in promoting calcification. In addition to reviewing the main findings, this review also sheds light on directions for future research in this area and discusses emerging pathways such as Pi-regulated intracellular calcium signaling, epigenetics, oxidative DNA damage and senescence-mediated mechanisms that may play critical, yet to be explored, regulatory and druggable roles in limiting VC.

Bone mesenchymal stem cell derived exosomes alleviate high phosphorus-induced calcification of vascular smooth muscle cells through the NONHSAT 084969.2/NF-κB axis

Our previous study showed that bone marrow mesenchymal stem cell derived exosomes (BMSC-Exos) suppress high phosphorus (Pi)-induced calcification of vascular smooth muscle cells (VSMCs). However, the mechanism had remained unclear. This study aimed to investigate the mechanism by which BMSC-Exos inhibit vascular calcification (VC). We found that BMSC-Exos reduced high Pi-induced Runx2, osteocalcin and BMP2 expression and inhibited the calcium deposition. Gene expression of human VSMCs stimulated by Pi or Pi plus BMSC-Exos (Pi + Exo) was systematically examined by microarray technology. NONHSAT 084969.2 and transcription factor p65 expression was significantly lower in the Pi + Exo group compared with the Pi group. This finding indicated that NONHSAT 084969.2 and the nuclear factor-κB pathway might play an important role in VC inhibition by BMSC-Exos. By silencing NONHSAT 084969.2 with small interfering RNA, Runx2, BMP2, and osteocalcin expression was decreased significantly. The calcified nodule content and alkaline phosphatase activity were reduced after NONHSAT 084969.2 inhibition and p65, p50, and IκB kinase-α expression was decreased significantly. These results indicated that BMSC-Exos inhibited Pi-induced transdifferentiation and calcification of VSMCs by regulating the NONHSAT 084969.2/nuclear factor-κB axis.

The ameliorative effect of terpinen-4-ol on ER stress-induced vascular calcification depends on SIRT1-mediated regulation of PERK acetylation

Endoplasmic reticulum (ER) stress-mediated phenotypic switching of vascular smooth muscle cells (VSMCs) is key to vascular calcification (VC) in patients with chronic kidney disease (CKD). Studies have shown that activation/upregulation of SIRT1 has a protective effect on CKD-VC. Meanwhile, although terpinen-4-ol has been shown to exert a protective effect against cardiovascular disease, its role and underlying mechanism in VC remain unclear. Herein, we explored whether terpinen-4-ol alleviates ER stress-mediated VC through sirtuin 1 (SIRT1) and elucidated its mechanism to provide evidence for its application in the clinical prevention and treatment of VC. To this end, a CKD-related VC animal model and β-glycerophosphate (β-GP)-induced VSMC calcification model were established to investigate the role of terpinen-4-ol in ER stress-induced VC, in vitro and in vivo. Additionally, to evaluate the involvement of SIRT1, mouse and VSMC Sirt1-knockdown models were established. Results show that terpinen-4-ol inhibits calcium deposition, phenotypic switching, and ER stress in VSMCs in vitro and in vivo. Furthermore, pre-incubation of VSMCs with terpinen-4-ol or a SIRT1 agonist, decreased β-GP-induced calcium salt deposition, increased SIRT1 protein level, and inhibited PERK-eIF2α-ATF4 pathway activation, thus, alleviating VC. Similar results were observed in VSMCs induced to overexpress SIRT1 via lentivirus transcription. Meanwhile, the opposite results were obtained in SIRT1-knockdown models. Further, results suggest that SIRT1 physically interacts with, and deacetylates PERK. Specifically, mass spectrometry analysis identified lysine K889 as the acetylation site of SIRT1, which regulates PERK. Finally, inhibition of SIRT1 reduced the effect of terpinen-4-ol on the deacetylation of PERK in vitro and in vivo and weakened the inhibitory effect of terpinen-4-ol against ER stress-mediated VC. Cumulatively, terpinen-4-ol was found to inhibit post-translational modification of PERK at the K889 acetylation site by upregulating SIRT1 expression, thereby ameliorating VC by regulating ER stress. This study provides insights into the underlying molecular mechanism of terpinen-4-ol, supporting its development as a promising therapeutic agent for CKD-VC.

Vascular Calcification in Rodent Models-Keeping Track with an Extented Method Assortment

Simple Summary

Arterial vessel diseases are the leading cause of death in the elderly and their accelerated pathogenesis is responsible for premature death in patients with chronic renal failure. Since no functioning therapy concepts exist so far, the identification of the main signaling pathways is of current research interest. To develop therapeutic concepts, different experimental rodent models are needed, which should be subject to the 3R principle of Russel and Burch: “Replace, Reduce and Refine”. This review aims to summarize the current available experimental rodent models for studying vascular calcification and their quantification methods.

Abstract

Vascular calcification is a multifaceted disease and a significant contributor to cardiovascular morbidity and mortality. The calcification deposits in the vessel wall can vary in size and localization. Various pathophysiological pathways may be involved in disease progression. With respect to the calcification diversity, a great number of research models and detection methods have been established in basic research, relying mostly on rodent models. The aim of this review is to provide an overview of the currently available rodent models and quantification methods for vascular calcification, emphasizing animal burden and assessing prospects to use available methods in a way to address the 3R principles of Russel and Burch: “Replace, Reduce and Refine”.

Oxidative stress in vascular calcification

Vascular calcification (VC), which is closely associated with significant mortality in cardiovascular disease, chronic kidney disease (CKD), and/or diabetes mellitus, is characterized by abnormal deposits of hydroxyapatite minerals in the arterial wall. The impact of oxidative stress (OS) on the onset and progression of VC has not been well described. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, myeloperoxidase (MPO), nitric oxide synthases (NOSs), superoxide dismutase (SOD) and paraoxonases (PONs) are relevant factors that influence the production of reactive oxygen species (ROS). Furthermore, excess ROS-induced OS has emerged as a critical mediator promoting VC through several mechanisms, including phosphate balance, differentiation of vascular smooth muscle cells (VSMCs), inflammation, DNA damage, and extracellular matrix remodeling. Because OS is a significant regulator of VC, antioxidants may be considered as novel treatment options.

Vascular Calcification in Chronic Kidney Disease: Diversity in the Vessel Wall

Vascular calcification (VC) is one of the major causes of cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD). VC is a complex process expressing similarity to bone metabolism in onset and progression. VC in CKD is promoted by various factors not limited to hyperphosphatemia, Ca/Pi imbalance, uremic toxins, chronic inflammation, oxidative stress, and activation of multiple signaling pathways in different cell types, including vascular smooth muscle cells (VSMCs), macrophages, and endothelial cells. In the current review, we provide an in-depth analysis of the various kinds of VC, the clinical significance and available therapies, significant contributions from multiple cell types, and the associated cellular and molecular mechanisms for the VC process in the setting of CKD. Thus, we seek to highlight the key factors and cell types driving the pathology of VC in CKD in order to assist in the identification of preventative, diagnostic, and therapeutic strategies for patients burdened with this disease.

POSTN promotes diabetic vascular calcification by interfering with autophagic flux

Autophagy is a lysosomal degradative process that is closely related to the pathogenesis of vascular calcification. Recent evidence suggests that periostin (POSTN) is a unique extracellular matrix protein that is associated with diabetic vascular complications. The aim of current study is to investigate the role of POSTN in diabetic vascular calcification and the underlying mechanisms. Results showed that POSTN was highly upregulated in both calcified arteries of diabetic rats and AGEs-BSA mediated vascular smooth muscle cell (VSMC) calcification. POSTN blocked autophagic flux during the diabetic calcification process, as evidenced by increased protein expression of Beclin1, LC3-II, and P62, as well as the co-localization of LC3-II and LAMP1. Inhibition of POSTN alleviated AGEs-BSA-induced autophagic flux blockade, thereby attenuating AGEs-BSA-induced VSMC calcification. Mechanistically, the upregulation of POSTN impaired the fusion of autophagosomes and lysosome and resulted in the autophagic flux blockade in AGEs-BSA-treated VSMC. Furthermore, this autophagic blockade was intracellular ROS-dependent. In summary, this study uncovered a novel mechanism of POSTN in autophagy regulation of diabetic vascular calcification.

Kv1.3 Channel Inhibition Limits Uremia-Induced Calcification in Mouse and Human Vascular Smooth Muscle

Chronic kidney disease (CKD) significantly increases cardiovascular risk. In advanced CKD stages, accumulation of toxic circulating metabolites and mineral metabolism alterations triggers vascular calcification, characterized by vascular smooth muscle cell (VSMC) transdifferentiation and loss of the contractile phenotype. Phenotypic modulation of VSMC occurs with significant changes in gene expression. Even though ion channels are an integral component of VSMC function, the effects of uremia on ion channel remodeling has not been explored. We used an in vitro model of uremia-induced calcification of human aorta smooth muscle cells (HASMCs) to study the expression of 92 ion channel subunit genes. Uremic serum-induced extensive remodeling of ion channel expression consistent with loss of excitability but different from the one previously associated with transition from contractile to proliferative phenotypes. Among the ion channels tested, we found increased abundance and activity of voltage-dependent K+ channel Kv1.3. Enhanced Kv1.3 expression was also detected in aorta from a mouse model of CKD. Pharmacological inhibition or genetic ablation of Kv1.3 decreased the amount of calcium phosphate deposition induced by uremia, supporting an important role for this channel on uremia-induced VSMC calcification.

Mitoquinone attenuates vascular calcification by suppressing oxidative stress and reducing apoptosis of vascular smooth muscle cells via the Keap1/Nrf2 pathway

Oxidative stress and apoptosis of vascular smooth muscle cells (VSMCs) are key to vascular calcification in patients with chronic kidney disease (CKD). The mitochondria-targeted antioxidant, mitoquinone (MitoQ), which reduces oxidative stress and apoptosis, has a protective effect in acute models of renal injury but whether MitoQ can attenuate vascular calcification in CKD patients is unknown. This study was conducted to investigate whether MitoQ can prevent calcification, both in vitro and in vivo. Adenine was used to induce calcification in rats, and inorganic phosphate was used to induce calcification in VSMCs. To elucidate the underlying molecular mechanism, a specific inhibitor of Nrf2, ML385, was used 1 h before MitoQ administration. Histological staining, ELISA, flow cytometry, alizarin red staining and western blotting were used to test this hypothesis. Administration of MitoQ alleviated calcification and oxidative stress. The anti-apoptotic effect of MitoQ was associated with upregulation of Bcl-2, downregulation of Bax, and increased Nrf2 expression. The effects of MitoQ were reversed by treatment with ML385. This study offers evidence that MitoQ attenuates vascular calcification by suppressing oxidative stress and apoptosis of VSMCs through the Keap1/Nrf2 pathway. MitoQ should be further investigated as a potential therapy to prevent vascular calcification in CKD patients.

The association between hypozincemia and aortic stenosis prevalence in hemodialysis patients: a single-center cross-sectional study

Background

Hypozincemia contributes to phosphate-induced vascular calcification in model animals of renal failure, but the association between hypozincemia and aortic stenosis (AS) prevalence in patients with end-stage kidney disease remains unreported in clinical settings.

Methods

To investigate the association between hypozincemia and AS prevalence in patients undergoing hemodialysis, we designed a single-center cross-sectional study. Our outcome “AS” was defined as prevalence of moderate or severe AS or surgical history for AS. Depending on serum zinc levels, we divided patients undergoing hemodialysis into deciles. The association between hypozincemia and AS prevalence was analyzed via logistic regression adjusted for age, sex, dialysis vintage, diabetes history, serum albumin, and history of taking calcium-containing phosphate binder.

Results

Ninety-three patients undergoing hemodialysis were eligible. The mean serum zinc level was 61.3 ± 13.9 μg/dL. Twelve patients who belonged to 1st decile had serum zinc levels ≤ 48 μg/dL. Of these twelve patients, six patients (50 %) had AS. On the other hand, of eighty one patients who belonged to 2nd–10th deciles (serum zinc levels > 48 μg/dL), thirteen patients (16 %) had AS. Hypozincemia (serum zinc levels ≤ 48 μg/dL) was associated with AS prevalence (P = 0.038; odds ratio 4.43; 95% confidence interval 1.09–18.0).

Conclusions

AS was more prevalent in patients undergoing hemodialysis with severe hypozincemia in our cross-sectional study, although interventional studies are required to elucidate the benefit of zinc supplementation for AS progression.

Oxidative Stress in ESRD Patients on Dialysis and the Risk of Cardiovascular Diseases

Chronic kidney disease is highly prevalent worldwide. The decline of renal function is associated with inadequate removal of a variety of uremic toxins that exert detrimental effects on cells functioning, thus affecting the cardiovascular system. The occurrence of cardiovascular aberrations in CKD is related to the impact of traditional risk factors and non-traditional CKD-associated risk factors, including anemia; inflammation; oxidative stress; the presence of some uremic toxins; and factors related to the type, frequency of dialysis and the composition of dialysis fluid. Cardiovascular diseases are the most frequent cause for the deaths of patients with all stages of renal failure. The kidney is one of the vital sources of antioxidant enzymes, therefore, the impairment of this organ is associated with decreased levels of these enzymes as well as increased levels of pro-oxidants. Uremic toxins have been shown to play a vital role in the onset of oxidative stress. Hemodialysis itself also enhances oxidative stress. Elevated oxidative stress has been demonstrated to be strictly related to kidney and cardiac damage as it aggravates kidney dysfunction and induces cardiac hypertrophy. Antioxidant therapies may prove to be beneficial since they can decrease oxidative stress, reduce uremic cardiovascular toxicity and improve survival.

Urinary magnesium predicts risk of cardiovascular disease in Chronic Kidney Disease stage 1-4 patients

Observational studies on dietary or circulating magnesium and risk of cardiovascular disease (CVD) in Chronic Kidney Disease (CKD) stage 1-4 have reported no-to-modest inverse associations. 24 h Urinary magnesium concentration (24 h UMg), an indicator of intestinal magnesium absorption, may provide better insight into the connection of CKD progression. We examined 3179 participants aged 18-74 years with CKD stage 1-4 in the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE) study, a prospective population-based cohort study. Data were analysed using Spearman rank-order correlation coefficients for all comparisons. We also performed a time-to-event analysis of the data using the Kaplan-Meier survival model, Cox proportional hazard model and competing risk Fine and Gray subdistribution hazard model. During a median follow-up of 4.19 years (interquartile range, 3.43-5.09 years), when modelling end-stage renal disease (ESRD), CVD and death, 24 h UMg was associated with risk of CVD (HR, 1.612 (95% CI, 1.056-2.460)), while no significant association with ESRD and death endpoints could be detected. 24 h UMg risk variants display a modest association with CVD in CKD stage 1-4 patients. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT03041987. Registered January 1, 2012. (retrospectively registered) (https://www.clinicaltrials.gov/ct2/show/NCT03041987?term=Chinese+Cohort+Study+of+Chronic+Kidney+Disease+%28C-STRIDE%29&rank=1).

ROS/p38MAPK-induced lamin B1 accumulation promotes chronic kidney disease-associated vascular smooth muscle cells senescence

The incidence of cardiovascular thrombotic events which are highly associated with atherosclerotic plaque vulnerability and its rupture is much higher in chronic kidney disease (CKD) patients than that in the general population. It has been reported that the thinning of fibrous cap in atherosclerotic plaque is a crucial factor in plaque vulnerability and thrombosis. Moreover, vascular smooth muscle cells (VSMCs) senescence play a crucial role in maintaining the thickness of fibrous cap. Lamin B1, one of the members of laminin family, is an important component of the nuclear membrane and it is related to cell senescence. While whether lamin B1 participates CKD-related VSMCs senescence and plaque vulnerability and the underlying mechanism remain unclear. Here, we found that CKD promoted fibrous cap thinning and reduced the stability of atherosclerotic plaque through accelerating VSMCs senescence. VSMCs senescence induced by CKD was related to the increased expression of lamin B1 and abnormality of nuclear membrane structure. Knocking down the expression of lamin B1 with RNA interference prevented CKD-induced aberrant nuclear membrane structure and senescence in VSMCs. Additionally, overproduction of reactive oxidative stress (ROS) and subsequent activation of ROS/p38MAPK under CKD milieus contribute to these series of outcomes, as scavenging ROS with N-acety-l-cysteine (NAC) or inhibiting p38MAPK signal pathway with SB203580 could inhibit CKD-induced activation of ROS/p38MAPK, increased expression of lamin B1, abnormality of nuclear membrane structure and VSMCs senescence. Taken together, these results suggested that ROS/p38MAPK-mediated increased expression of lamin B1 and abnormality of nuclear membrane structure was an important mechanism of CKD-induced VSMCs senescence.

Uremic Toxins and Vascular Calcification-Missing the Forest for All the Trees

The cardiorenal syndrome relates to the detrimental interplay between the vascular system and the kidney. The uremic milieu induced by reduced kidney function alters the phenotype of vascular smooth muscle cells (VSMC) and promotes vascular calcification, a condition which is strongly linked to cardiovascular morbidity and mortality. Biological mechanisms involved include generation of reactive oxygen species, inflammation and accelerated senescence. A better understanding of the vasotoxic effects of uremic retention molecules may reveal novel avenues to reduce vascular calcification in CKD. The present review aims to present a state of the art on the role of uremic toxins in pathogenesis of vascular calcification. Evidence, so far, is fragmentary and limited with only a few uremic toxins being investigated, often by a single group of investigators. Experimental heterogeneity furthermore hampers comparison. There is a clear need for a concerted action harmonizing and standardizing experimental protocols and combining efforts of basic and clinical researchers to solve the complex puzzle of uremic vascular calcification.