Cross-talk of receptor activator of nuclear factor-κB ligand signaling with renin-angiotensin system in vascular calcification

The role of SERCA in vascular diseases, a potential therapeutic target

SERCA, the sarco/endoplasmic reticulum Ca2+-ATPase, is a pivotal protein that transports calcium ions (Ca2+) from the cytoplasm into the sarcoplasmic/endoplasmic reticulum (SR/ER), thus sustaining cellular Ca2+ homeostasis. A growing body of evidence indicates that SERCA dysfunction correlates with disrupted cellular Ca2+ homeostasis and ER stress, precipitating a spectrum of chronic diseases. As a regulator of Ca2+ homeostasis, SERCA emerges as a potential therapeutic target for conditions associated with Ca2+ imbalance. This review delineates the association between SERCA and a variety of vascular diseases.

Vasoconstriction-inhibiting factor: an endogenous inhibitor of vascular calcification as a calcimimetic of calcium-sensing receptor

AIMS

Patients with chronic kidney disease (CKD) show a high risk of cardiovascular diseases, predominantly caused by accelerated vascular calcification. Vascular calcification is a highly regulated process with no current treatment. The vasoconstriction-inhibiting factor (VIF) peptide was recently discovered with vasoregulatory properties, but no information regarding calcification has been described.

METHODS AND RESULTS

In the present work, the inhibitory calcification effect of the VIF peptide was analysed in vitro in vascular smooth muscle cells (VSMCs), ex vivo in rat aortic rings, as well as in vivo in rats treated with vitamin D and nicotine (VDN). The VIF peptide inhibits vascular calcification by acting as a calcimimetic for the calcium-sensing receptor, increasing carboxylated matrix Gla protein production and blocking the activation of calcification pathways. The VIF peptide decreased calcium influx, the production of reactive oxygen species, and the activation of multiple kinases in VSMCs. Furthermore, calcium deposition in the aortas of patients with CKD negatively correlates with the VIF peptide concentration. Moreover, we show the cleavage of the VIF peptide from chromogranin-A by 'proprotein convertase subtilisin/kexin type 2' and 'carboxypeptidase E' enzymes. In addition, 'cathepsin K' degrades the VIF peptide. The active site of the native 35 amino acid-sequence long VIF peptide was identified with seven amino acids, constituting a promising drug candidate with promise for clinical translation.

CONCLUSION

The elucidation of the underlying mechanism by which the VIF peptide inhibits vascular calcification, as well as the active sequence and the cleavage and degradation enzymes, forms the basis for developing preventive and therapeutic measures to counteract vascular calcification.

Tripeptide DT-109 (Gly-Gly-Leu) attenuates atherosclerosis and vascular calcification in nonhuman primates

Advanced atherosclerotic lesions and vascular calcification substantially increase the risk of cardiovascular events. However, effective strategies for preventing or treating advanced atherosclerosis and calcification are currently lacking. This study investigated the efficacy of DT-109 (Gly-Gly-Leu) in attenuating atherosclerosis and calcification in nonhuman primates, exploring its broader therapeutic potential. In this study, twenty male cynomolgus monkeys were administered a cholesterol-rich diet ad libitum for 10 months. Then, the animals were treated either orally with DT-109 (150 mg/kg/day) or a vehicle (H2O) for 5 months while continuing on the same diet. Plasma lipid levels were measured monthly and at the end of the experiment, pathological examinations of the aortas and coronary arteries and RNA sequencing of the coronary arteries were performed. To explore possible molecular mechanisms, the effects of DT-109 on smooth muscle cells (SMCs) were examined in vitro. We found that DT-109 administration significantly suppressed atherosclerotic lesion formation in both the aorta and coronary arteries. Pathological examinations revealed that DT-109 treatment reduced lesional macrophage content and calcification. RNA sequencing analysis showed that DT-109 treatment significantly downregulated the pro-inflammatory factors NLRP3, AIM2, and CASP1, the oxidative stress factors NCF2 and NCF4, and the osteogenic factors RUNX2, COL1A1, MMP2, and MMP9, while simultaneously upregulating the expression of the SMCs contraction markers ACTA2, CNN1, and TAGLN. Furthermore, DT-109 inhibited SMC calcification and NLRP3 inflammasome activation in vitro. These results demonstrate that DT-109 effectively suppresses both atherosclerosis and calcification. These findings, in conjunction with insights from our previous studies, position DT-109 as a novel multifaceted therapeutic agent for cardiovascular diseases.

Ligustrazine alleviates the progression of coronary artery calcification by inhibiting caspase-3/GSDME mediated pyroptosis

Coronary artery calcification (CAC) is an early marker for atherosclerosis and is mainly induced by the osteoblast-like phenotype conversion of vascular smooth muscle cells (VSMCs). Recent reports indicate that NOD-like receptor protein 3 (NLRP3)-mediated pyroptosis plays a significant role in the calcification of vascular smooth muscle cells (VSMCs), making it a promising target for treating calcific aortic valve disease (CAC). Ligustrazine, or tetramethylpyrazine (TMP), has been found effective in various cardiovascular and cerebrovascular diseases and is suggested to inhibit NLRP3-mediated pyroptosis. However, the function of TMP in CAC is unknown. Herein, influences of TMP on β-glycerophosphate (β-GP)-stimulated VSMCs and OPG-/- mice were explored. Mouse Aortic Vascular Smooth Muscle (MOVAS-1) cells were stimulated by β-GP with si- caspase-3, si- Gasdermin E (GSDME) or TMP. Increased calcification, reactive oxygen species (ROS) level, Interleukin-1beta (IL-1β) and Interleukin-18 (IL-18) levels, lactate dehydrogenase (LDH) release, enhanced apoptosis, and activated cysteine-aspartic acid protease-3 (caspase-3)/GSDME signaling were observed in β-GP-stimulated MOVAS-1 cells, which was sharply alleviated by si-caspase-3, si-GSDME or TMP. Furthermore, the impact of TMP on the β-GP-induced calcification and injury in MOVAS-1 cells was abolished by raptinal, an activator of caspase-3. Subsequently, OPG-/- mice were dosed with TMP or TMP combined with raptinal. Calcium deposition, increased nodules, elevated IL-1β and IL-18 levels, upregulated CASP3 and actin alpha 2, smooth muscle (ACTA2), and activated caspase-3/GSDME signaling in OPG-/- mice were markedly alleviated by TMP, which were notably reversed by the co-administration of raptinal. Collectively, TMP mitigated CAC by inhibiting caspase-3/GSDME mediated pyroptosis.

RANKL signaling drives skeletal muscle into the oxidative profile

The bone-muscle unit refers to the reciprocal regulation between bone and muscle by mechanical interaction and tissue communication via soluble factors. The RANKL stimulation induces mitochondrial biogenesis and increases the oxidative capacity in osteoclasts and adipocytes. RANKL may bind to the membrane bound RANK or to osteoprotegerin (OPG), a decoy receptor that inhibits RANK-RANKL activation. RANK is highly expressed in skeletal muscle, but the contribution of RANKL to healthy skeletal muscle fiber remains elusive. Here we show that RANKL stimulation in C2C12-derived myotubes induced activation of mitochondrial biogenesis pathways as detected by RNA-seq and western blot. RANKL expanded the mitochondrial reticulum, as shown by mitochondrial DNA quantification and MitoTracker staining, and boosted the spare respiratory capacity. Using MEK and MAPK inhibitors, we found that RANKL signals via ERK and p38 to induce mitochondrial biogenesis. The soleus from OPG-/- and OPG+/- mice showed higher respiratory rates compared to C57BL6/J WT mice, which correlates with high serum RANKL levels. RANKL infusion using a mini-osmotic pump in WT mice increased the number of mitochondria, boosted the respiratory rate, increased succinate dehydrogenase activity in skeletal muscle, and improved the fatigue resistance of gastrocnemius. Therefore, our findings reveal a new role of RANKL as an osteokine-like protein that impacts muscle fiber metabolism.

Potential convergence of olfactory dysfunction in Parkinson's disease and COVID-19: The role of neuroinflammation

Parkinson's disease (PD) is a prevalent neurodegenerative disorder that affects 7-10 million individuals worldwide. A common early symptom of PD is olfactory dysfunction (OD), and more than 90% of PD patients suffer from OD. Recent studies have highlighted a high incidence of OD in patients with SARS-CoV-2 infection. This review investigates the potential convergence of OD in PD and COVID-19, particularly focusing on the mechanisms by which neuroinflammation contributes to OD and neurological events. Starting from our fundamental understanding of the olfactory bulb, we summarize the clinical features of OD and pathological features of the olfactory bulb from clinical cases and autopsy reports in PD patients. We then examine SARS-CoV-2-induced olfactory bulb neuropathology and OD and emphasize the SARS-CoV-2-induced neuroinflammatory cascades potentially leading to PD manifestations. By activating microglia and astrocytes, as well as facilitating the aggregation of α-synuclein, SARS-CoV-2 could contribute to the onset or exacerbation of PD. We also discuss the possible contributions of NF-κB, the NLRP3 inflammasome, and the JAK/STAT, p38 MAPK, TLR4, IL-6/JAK2/STAT3 and cGAS-STING signaling pathways. Although olfactory dysfunction in patients with COVID-19 may be reversible, it is challenging to restore OD in patients with PD. With the emergence of new SARS-CoV-2 variants and the recurrence of infections, we call for continued attention to the intersection between PD and SARS-CoV-2 infection, especially from the perspective of OD.

A Low Concentration of Citreoviridin Prevents Both Intracellular Calcium Deposition in Vascular Smooth Muscle Cell and Osteoclast Activation In Vitro

Vascular calcification (VC) and osteoporosis are age-related diseases and significant risk factors for the mortality of elderly. VC and osteoporosis may share common risk factors such as renin-angiotensin system (RAS)-related hypertension. In fact, inhibitors of RAS pathway, such as angiotensin type 1 receptor blockers (ARBs), improved both vascular calcification and hip fracture in elderly. However, a sex-dependent discrepancy in the responsiveness to ARB treatment in hip fracture was observed, possibly due to the estrogen deficiency in older women, suggesting that blocking the angiotensin signaling pathway may not be effective to suppress bone resorption, especially if an individual has underlying osteoclast activating conditions such as estrogen deficiency. Therefore, it has its own significance to find alternative modality for inhibiting both vascular calcification and osteoporosis by directly targeting osteoclast activation to circumvent the shortcoming of ARBs in preventing bone resorption in estrogen deficient individuals. In the present study, a natural compound library was screened to find chemical agents that are effective in preventing both calcium deposition in vascular smooth muscle cells (vSMCs) and activation of osteoclast using experimental methods such as Alizarin red staining and Tartrate-resistant acid phosphatase staining. According to our data, citreoviridin (CIT) has both an anti-VC effect and anti-osteoclastic effect in vSMCs and in Raw 264.7 cells, respectively, suggesting its potential as an effective therapeutic agent for both VC and osteoporosis.

Angiotensin II Induces Aortic Rupture and Dissection in Osteoprotegerin-Deficient Mice

Background

The biological mechanism of action for osteoprotegerin, a soluble decoy receptor for the receptor activator of nuclear factor‐kappa B ligand in the vascular structure, has not been elucidated. The study aim was to determine if osteoprotegerin affects aortic structural integrity in angiotensin II (Ang II)‐induced hypertension.

Methods and Results

Mortality was higher (P<0.0001 by log‐rank test) in 8‐week‐old male homozygotes of osteoprotegerin gene‐knockout mice given subcutaneous administration of Ang II for 28 days, with an incidence of 21% fatal aortic rupture and 23% aortic dissection, than in age‐matched wild‐type mice. Ang II‐infused aorta of wild‐type mice showed that osteoprotegerin immunoreactivity was present with proteoglycan. The absence of osteoprotegerin was associated with decreased medial and adventitial thickness and increased numbers of elastin breaks as well as with increased periostin expression and soluble receptor activator of nuclear factor‐kappa B ligand concentrations. PEGylated human recombinant osteoprotegerin administration decreased all‐cause mortality (P<0.001 by log‐rank test), the incidence of fatal aortic rupture (P=0.08), and aortic dissection (P<0.001) with decreasing numbers of elastin breaks, periostin expressions, and soluble receptor activator of nuclear factor‐kappa B ligand concentrations in Ang II‐infused osteoprotegerin gene‐knockout mice.

Conclusions

These data suggest that osteoprotegerin protects against aortic rupture and dissection in Ang II‐induced hypertension by inhibiting receptor activator of nuclear factor‐kappa B ligand activity and periostin expression.

Hypertension meets osteoarthritis - revisiting the vascular aetiology hypothesis

Osteoarthritis (OA) is a whole-joint disease characterized by subchondral bone perfusion abnormalities and neovascular invasion into the synovium and articular cartilage. In addition to local vascular disturbance, mounting evidence suggests a pivotal role for systemic vascular pathology in the aetiology of OA. This Review outlines the current understanding of the close relationship between high blood pressure (hypertension) and OA at the crossroads of epidemiology and molecular biology. As one of the most common comorbidities in patients with OA, hypertension can disrupt joint homeostasis both biophysically and biochemically. High blood pressure can increase intraosseous pressure and cause hypoxia, which in turn triggers subchondral bone and osteochondral junction remodelling. Furthermore, systemic activation of the renin-angiotensin and endothelin systems can affect the Wnt-β-catenin signalling pathway locally to govern joint disease. The intimate relationship between hypertension and OA indicates that endothelium-targeted strategies, including re-purposed FDA-approved antihypertensive drugs, could be useful in the treatment of OA.

Contribution of Gut Microbiota-Derived Uremic Toxins to the Cardiovascular System Mineralization

Chronic kidney disease (CKD) affects more than 10% of the world population and leads to excess morbidity and mortality (with cardiovascular disease as a leading cause of death). Vascular calcification (VC) is a phenomenon of disseminated deposition of mineral content within the media layer of arteries preceded by phenotypic changes in vascular smooth muscle cells (VSMC) and/or accumulation of mineral content within the atherosclerotic lesions. Medial VC results in vascular stiffness and significantly contributes to increased cardio-vascular (CV) morbidity, whereas VC of plaques may rather increase their stability. Mineral and bone disorders of CKD (CKD-MBD) contribute to VC, which is further aggravated by accumulation of uremic toxins. Both CKD-MBD and uremic toxin accumulation affect not only patients with advanced CKD (glomerular filtration rate (GFR) less than 15 mL/min/1.72 m², end-stage kidney disease) but also those on earlier stages of a disease. The key uremic toxins that contribute to VC, i.e., p-cresyl sulphate (PCS), indoxyl sulphate (IS) and trimethylamine-N-oxide (TMAO) originate from bacterial metabolism of gut microbiota. All mentioned toxins promote VC by several mechanisms, including: Transdifferentiation and apoptosis of VSMC, dysfunction of endothelial cells, oxidative stress, interaction with local renin–angiotensin–aldosterone system or miRNA profile modification. Several attractive methods of gut microbiota manipulations have been proposed in order to modify their metabolism and to limit vascular damage (and VC) triggered by uremic toxins. Unfortunately, to date no such method was demonstrated to be effective at the level of “hard” patient-oriented or even clinically relevant surrogate endpoints.

Epidemiological Research Advances in Vascular Calcification in Diabetes

Vascular calcification is the transformation of arterial wall mesenchymal cells, particularly smooth muscle cells (SMCs), into osteoblast phenotypes by various pathological factors. Additionally, vascular transformation mediates the abnormal deposition of calcium salts in the vascular wall, such as intimal and media calcification. Various pathological types have been described, such as calcification and valve calcification. The incidence of vascular calcification in patients with diabetes is much higher than that in nondiabetic patients, representing a critical cause of cardiovascular events in patients with diabetes. Because basic research on the clinical transformation of vascular calcification has yet to be conducted, this study systematically expounds on the risk factors for vascular calcification, vascular bed differences, sex differences, ethnic differences, diagnosis, severity assessments, and treatments to facilitate the identification of a new entry point for basic research and subsequent clinical transformation regarding vascular calcification and corresponding clinical evaluation strategies.

Circadian rhythm disorder: a potential inducer of vascular calcification?

Over the past decades, circadian rhythm has drawn a great attention in cardiovascular diseases. The expressions of rhythm genes fluctuate in accordance with the diurnal changes of vascular physiology, which highlights the pivotal effect of vascular clock. Recent researches show that the circadian clock can directly regulate the synthetic and secretory function of endothelial cells and phenotypic switch of vascular smooth muscle cells to adjust vascular relaxation and contraction. Importantly, dysfunction of vascular cells is involved in vascular calcification. Secretion of osteogenic cytokines and calcified vesicles in the vessel, osteogenic phenotype switch of vascular smooth muscle cells are all implicated in the calcification process. Moreover, circadian rhythm disorder can lead to abnormal hormone secretion, oxidative stress, inflammatory reaction, and autophagy, all of which should not be ignored in vascular calcification. Vascular senescence is another pathogenetic mechanism in vascular calcification. Accelerated vascular senescence may act as an important intermediate factor to promote vascular calcification in circadian rhythm disorders. In this review, we elaborate the potential effect of circadian rhythm disorder in vascular calcification and try to provide a new direction in the prevention of vascular calcification.

Vascular Aging and Central Aortic Blood Pressure: From Pathophysiology to Treatment

Large conductive arteries undergo to structural modifications by aging, eventually leading to increased vascular stiffness. As consequence, cardiovascular hemodynamic changes by increasing central blood pressure which may be also associated to the remodelling of peripheral resistance arteries that contribute to increase further the central vascular stiffness and blood pressure. These modifications resemble the ones that has been shown in essential hypertension, thus a condition of "early vascular aging" has been described in hypertensive patients. Since hypertension related target organs, particularly the heart, face aortic blood pressure rather than brachial blood pressure, it has been recently suggested that central blood pressure and other parameters of large arteries' stiffness, including pulse wave velocity (PWV), may better correlate with subclinical organ damage and might be useful to assess the cardiovascular risk of patients beyond the traditional risk factors. Different devices have been validated to measure central blood pressure and PWV, and are currently available for clinical use. The increasing application of these tools in clinical practice could improve the management of hypertensive patients by better defining the cardiovascular risk and address the antihypertensive therapy.

RANKL induces beige adipocyte differentiation in preadipocytes

The receptor activator of nuclear factor-κB (NF-κB) (RANK), its ligand (RANKL), and the decoy receptor osteoprotegerin (OPG) are a triad of proteins that regulate bone metabolism, and serum OPG is considered a biomarker for cardiovascular diseases and Type 2 diabetes; however, the implications of OPG in adipose tissue metabolism remains elusive. In this study, we investigate RANK-RANKL-OPG signaling in white adipose tissue browning. Histological analysis of osteoprotegerin knockout (OPG-/-) mice showed subcutaneous white adipose tissue (sWAT) browning, resistance for high-fat diet-induced weight gain, and preserved glucose metabolism compared with wild-type (WT) mice. Stromal vascular fraction (SVF) cells from sWAT of OPG-/- mice showed multilocular morphology and higher expression of brown adipocyte marker genes compared with those from the WT group. Infusion of RANKL induced browning and elevated respiratory rates in sWAT, along with increased whole body oxygen consumption in mice measured by indirect calorimetry. Subcutaneous WAT-derived SVF and 3T3-L1 cells, but not mature white adipocytes, differentiated into beige adipose tissue in the presence of RANKL. Moreover, SVF cells, even under white adipocyte differentiation, showed multilocular lipid droplet, lower lipid content, and increased expression of beige adipocyte markers with RANKL stimulation. In this study, we show for the first time the contribution of RANKL to increase energy expenditure by inducing beige adipocyte differentiation in preadipocytes.

Vascular Calcification: An Important Understanding in Nephrology

Vascular calcification (VC) is a life-threatening state in chronic kidney disease (CKD). High cardiovascular mortality and morbidity of CKD cases may root from medial VC promoted by hyperphosphatemia. Vascular calcification is an active, highly regulated, and complex biological process that is mediated by genetics, epigenetics, dysregulated form of matrix mineral metabolism, hormones, and the activation of cellular signaling pathways. Moreover, gut microbiome as a source of uremic toxins (eg, phosphate, advanced glycation end products and indoxyl-sulfate) can be regarded as a potential contributor to VC in CKD. Here, an update on different cellular and molecular processes involved in VC in CKD is discussed to elucidate the probable therapeutic pathways in the future.

Captopril Attenuates the Upregulated Connexin 43 Expression in Artery Calcification

OBJECTIVE

Vascular calcification is commonly observed in atherosclerosis and diabetes. The renin-angiotensin II system is associated with the regulation of arterial stiffening. The aim of this study was to examine whether the angiotensin-converting enzyme inhibitors captopril attenuates artery calcification.

METHODS

The rat model of arterial calcification was established by a combination of warfarin and vitamin K1. Two weeks after the induction of arterial calcification, captopril treatment was initiated. One week after captopril treatment, aortic arteries were examined to determine the calcification morphology and the connexin 43 expression. Matrix Gla protein (MGP), receptor activator of nuclear factor-κB ligand (RANKL) and extracellular regulated protein kinase (ERK) pathways were examined.

RESULTS

The morphology of the calcified arteries was significantly attenuated after captopril treatment. Consistently, captopril inhibited the increased connexin 43 expression and enhanced the decreased MGP expression in calcification arteries. Furthermore, captopril enhanced the decreased SM22 expression in calcified arteries by fluorescence assay. Finally, the calcification arteries increased the p38, p-ERK and RANKL expression, which were downregulated by captopril treatment.

CONCLUSIONS

We concluded that captopril attenuated the increased connexin 43 expression and enhanced the MGP and SM22 expression levels, which are associated with the inactivation of p-ERK, p38 and RANKL pathways in rat aortic arteries.

RANKL biology: bone metabolism, the immune system, and beyond

Receptor activator of NF-κB (RANK) ligand (RANKL) induces the differentiation of monocyte/macrophage-lineage cells into the bone-resorbing cells called osteoclasts. Because abnormalities in RANKL, its signaling receptor RANK, or decoy receptor osteoprotegerin (OPG) lead to bone diseases such as osteopetrosis, the RANKL/RANK/OPG system is essential for bone resorption. RANKL was first discovered as a T cell-derived activator of dendritic cells (DCs) and has many functions in the immune system, including organogenesis, cellular development. The essentiality of RANKL in the bone and the immune systems lies at the root of the field of "osteoimmunology." Furthermore, this cytokine functions beyond the domains of bone metabolism and the immune system, e.g., mammary gland and hair follicle formation, body temperature regulation, muscle metabolism, and tumor development. In this review, we will summarize the current understanding of the functions of the RANKL/RANK/OPG system in biological processes.

Pharmacological and Nutritional Modulation of Vascular Calcification

Vascular calcification is an independent predictor of cardiovascular disease, and therefore, inhibition or regression of this processes is of clinical importance. The standard care regarding prevention and treatment of cardiovascular disease at this moment mainly depends on drug therapy. In animal and preclinical studies, various forms of cardiovascular drug therapy seem to have a positive effect on vascular calcification. In particular, calcium channel blockers and inhibitors of the renin-angiotensin-aldosteron system slowed down arterial calcification in experimental animals. In humans, the results of trials with these drugs are far less pronounced and often contradictory. There is limited evidence that the development of new atherosclerotic lesions may be retarded in patients with coronary artery disease, but existing lesions can hardly be influenced. Although statin therapy has a proven role in the prevention and treatment of cardiovascular morbidity and mortality, it is associated with both regression and acceleration of the vascular calcification process. Recently, nutritional supplements have been recognized as a potential tool to reduce calcification. This is particularly true for vitamin K, which acts as an inhibitor of vascular calcification. In addition to vitamin K, other dietary supplements may also modulate vascular function. In this narrative review, we discuss the current state of knowledge regarding the pharmacological and nutritional possibilities to prevent the development and progression of vascular calcification.

[The renin-angiotensin-aldosterone system as a potential target for therapy in patients with calcific aortic stenosis: a literature review]

Calcific aortic valve stenosis (CAVS) is a serious socio-economic problem in developed countries because this disease is the most common indication for aortic valve replacement. Currently, there are no methods for non-invasive treatment of CAVS. Nevertheless, it is assumed that effective drug therapy for CAVS can be developed on the basis of modulators of the renin-angiotensin-aldosterone system (RAAS), which is involved in the pathogenesis of this disease. The purpose of this paper is to compile and analyze current information on the role of RAAS in the CAVS pathophysiology. Recent data on the effectiveness of RAAS inhibition are reviewed.

Development of calcific aortic valve disease: Do we know enough for new clinical trials?

Calcific aortic valve disease (CAVD), previously thought to represent a passive degeneration of the valvular extracellular matrix (VECM), is now regarded as an intricate multistage disorder with sequential yet intertangled and interacting underlying processes. Endothelial dysfunction and injury, initiated by disturbed blood flow and metabolic disorders, lead to the deposition of low-density lipoprotein cholesterol in the VECM further provoking macrophage infiltration, oxidative stress, and release of pro-inflammatory cytokines. Such changes in the valvular homeostasis induce differentiation of normally quiescent valvular interstitial cells (VICs) into synthetically active myofibroblasts producing excessive quantities of the VECM and proteins responsible for its remodeling. As a result of constantly ongoing degradation and re-deposition, VECM becomes disorganised and rigid, additionally potentiating myofibroblastic differentiation of VICs and worsening adaptation of the valve to the blood flow. Moreover, disrupted and excessively vascularised VECM is susceptible to the dystrophic calcification caused by calcium and phosphate precipitating on damaged collagen fibers and concurrently accompanied by osteogenic differentiation of VICs. Being combined, passive calcification and biomineralisation synergistically induce ossification of the aortic valve ultimately resulting in its mechanical incompetence requiring surgical replacement. Unfortunately, multiple attempts have failed to find an efficient conservative treatment of CAVD; however, therapeutic regimens and clinical settings have also been far from the optimal. In this review, we focused on interactions and transitions between aforementioned mechanisms demarcating ascending stages of CAVD, suggesting a predisposing condition (bicuspid aortic valve) and drug combination (lipid-lowering drugs combined with angiotensin II antagonists and cytokine inhibitors) for the further testing in both preclinical and clinical trials.

Charcot Pathogenesis: A Study of In Vivo Gene Expression

Charcot neuroarthropathy is a rare but often difficult to manage disease in the neuropathic patient. Early signs such as unremarkable edema, marginal trauma, or minor infection can activate a cascade of bony destruction and lead to gross prominence or deformity, with dire consequences. The exact molecular mechanism is poorly understood. Current theory states that an inflammatory reaction leads to the activation of osteoclasts mediated by specific cytokines. Our study sought to test the genetic expression of certain biomarkers in diabetic patients with and without Charcot neuroarthropathy compared with patients with and without diabetes or neuropathy. A total of 30 patients participated in the study, 17 (57%) males and 13 (43%) females. Peripheral blood samples were drawn, and gene expression was measured using real-time polymerase chain reaction. The expression levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin showed no significant increase in the Charcot neuroarthropathy group compared with the healthy control group. We determined that the levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin were not significantly increased in Charcot neuroarthropathy patients compared with healthy control patients. These results demonstrate a need for further investigation into alternative molecular pathways to determine the exact mechanism of the disease process.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

RANKL-mediated osteoclastogenic differentiation of macrophages in the abdominal aorta of angiotensin II-infused apolipoprotein E knockout mice

OBJECTIVE

Osteoclastogenic activation of macrophages (OCG) occurs in human abdominal aortic aneurysms (AAAs) and in calcium chloride-induced degenerative AAAs in mice, which have increased matrix metalloproteinase activity. As the activity of OCG in dissecting aneurysms is not clear, we tested the hypothesis that OCG contributes to angiotensin II (Ang II)-induced dissecting aneurysm (Ang II-induced AAA) in apolipoprotein E knockout mice.

METHODS

AAAs were produced in apolipoprotein E knockout mice via the administration of Ang II. Additionally, receptor activator of nuclear factor kB ligand (RANKL)-neutralizing antibody (5 mg/kg) was administered to one group of mice 7 days prior to Ang II infusion. Aneurysmal sections were probed for presence of RANKL and tartrate-resistant acid phosphatase via immunohistochemistry and immunofluorescence staining. Mouse aortas were also examined for RANKL and matrix metalloproteinase 9 expression via Western blot. In vitro murine vascular smooth muscle cells (MOVAS) and murine macrophages (RAW 264.7) were analyzed for the expression of osteogenic factors via Western blot, qPCR, and flow cytometry in response to Ang II or RANKL stimulation. The signaling pathway that mediates Ang II-induced RANKL expression in MOVAS cells was also investigated via application of TG101348, a Janus kinase 2 (JAK2) inhibitor, and Western blot analysis.

RESULTS

Immunohistochemical staining of Ang II-induced AAA sections revealed OCG as evidenced by increased RANKL and tartrate-resistant acid phosphatase expression compared with control mice. Immunofluorescence staining of AAA sections revealed co-localization of vascular smooth muscle cells and RANKL, revealing vascular smooth muscle cells as one potential source of RANKL. Systemic administration of RANKL-neutralizing antibody suppressed Ang II-induced AAA, with significant reduction of the maximum diameter of the abdominal aorta compared with vehicle controls (1.5 ± 0.4 mm vs 2.2 ± 0.2 mm). Ang II (1 μM) treatment induced a significant increase in RANKL messenger RNA expression levels in MOVAS cells compared with the vehicle control (1.0 ± 0.2 vs 2.8 ± 0.2). The activities of JAK2 and signal transducer and activator of transcription 5 (STAT5) were also significantly increased by Ang II treatment. Inhibition of JAK2/STAT5 suppressed Ang II-induced RANKL expression, suggesting the involvement of the JAK2/STAT5 signaling pathway.

CONCLUSIONS

OCG with increased RANKL expression was present in Ang II-induced AAA, and neutralization of RANKL suppressed AAA formation. As neutralization of RANKL has been used clinically to treat osteoporosis and other osteoclast-related diseases, additional study of the effectiveness of RANKL neutralization in AAA is warranted.

Diabetes and Abdominal Aortic Calcification-a Systematic Review

PURPOSE OF REVIEW

A systematic literature review was performed to evaluate diabetes mellitus (DM) as a risk factor of abdominal aortic calcification (AAC), and address factors that might contribute to the development of AAC in DM patients.

RECENT FINDINGS

DM is an independent risk factor of AAC development. Bone metabolism along with lifestyle factors among DM patients makes them more prone to AAC. Hip and vertebral fractures, high phosphate, smoking, hypertension, and low osteocalcin could make DM patients prone to AAC. Low levels of high-density lipoprotein (HDL), high low-density lipoprotein (LDL), high total cholesterol/HDL ratio, low bone mineral density (BMD) may be risk factors, but the literature is more ambiguous. Body mass index (BMI) does not appear to increase risk of AAC. High phosphate levels and low osteocalcin levels seem to be biomarkers of AAC in patients with diabetes. However, the association between DM and AAC is complicated.

The RANK/RANKL/OPG system in tumorigenesis and metastasis of cancer stem cell: potential targets for anticancer therapy

The molecular triad involving receptor activator of nuclear factor kβ (RANK)/RANK ligand (RANKL)/osteoprotegerin cytokine system has been well implicated in several physiological and pathological processes including bone metabolism, mammary gland development, regulation of the immune function, tumorigenesis and metastasis of cancer stem cell, thermoregulation, and vascular calcification. However, this review aimed to summarize several original and up-to-date articles focusing on the role of this signaling system in cancer cell development and metastasis as well as potential therapeutic agents targeting any of the three tumor necrotic factor super family proteins and/or their downstream signaling pathways. The RANK/RANKL axis has direct effects on tumor cell development. The system is well involved in the development of several primary and secondary tumors including breast cancer, prostate cancer, bone tumors, and leukemia. The signaling of this triad system has also been linked to tumor invasiveness in the advanced stage. Bone is by far the most common site of cancer metastasis. Several therapeutic agents targeting this system have been developed. Among them, a monoclonal antibody, denosumab, was clinically approved for the treatment of osteoporosis and cancer-related diseases.

AT1 receptor signaling pathways in the cardiovascular system

The importance of the renin angiotensin aldosterone system in cardiovascular physiology and pathophysiology has been well described whereas the detailed molecular mechanisms remain elusive. The angiotensin II type 1 receptor (AT1 receptor) is one of the key players in the renin angiotensin aldosterone system. The AT1 receptor promotes various intracellular signaling pathways resulting in hypertension, endothelial dysfunction, vascular remodeling and end organ damage. Accumulating evidence shows the complex picture of AT1 receptor-mediated signaling; AT1 receptor-mediated heterotrimeric G protein-dependent signaling, transactivation of growth factor receptors, NADPH oxidase and ROS signaling, G protein-independent signaling, including the β-arrestin signals and interaction with several AT1 receptor interacting proteins. In addition, there is functional cross-talk between the AT1 receptor signaling pathway and other signaling pathways. In this review, we will summarize an up to date overview of essential AT1 receptor signaling events and their functional significances in the cardiovascular system.

Effects on bone metabolism markers and arterial stiffness by switching to rivaroxaban from warfarin in patients with atrial fibrillation

In recent years, direct oral anticoagulants (DOACs) of dabigatran, rivaroxaban, apixaban, edoxaban, which are all alternatives to warfarin, have been released. The use of DOACs is becoming more widespread in the clinical management of thrombotic stroke risk in patients with atrial fibrillation (AF). In large-scale clinical trials of each drug, DOACs were reported to inhibit intracranial hemorrhage, stroke, and death compared to warfarin. Warfarin is an endogenous vitamin K antagonist; therefore, patients who are taking warfarin must be prohibited from taking vitamin K. Vitamin K is an essential cofactor required for the ɤ-carboxylation of vitamin K-dependent proteins including coagulation factors, osteocalcin (OC), matrix Gla protein (MGP), and the growth arrest-specific 6 (GAS6). OC is a key factor for bone matrix formation. MGP is a local inhibitor of soft tissue calcification in the vessel wall. GAS6 prevents the apoptosis of vascular smooth muscle cells. Therefore, decrease of blood vitamin K levels may cause osteoporosis, vascular calcification, and the inhibition of vessels angiogenesis. This study aimed to evaluate the effects of changing from warfarin to rivaroxaban on bone mineral metabolism, vascular calcification, and vascular endothelial dysfunction. We studied 21 consecutive patients with persistent or chronic AF, who were treated with warfarin at least for 12 months. Warfarin administration was changed to rivaroxaban (10 or 15 mg/day) in all patients. Osteopontin (OPN), bone alkaline phosphatase (BAP), and under-carboxylated osteocalcin (ucOC) were measured. Pulse wave velocity (PWV) and augmentation index (AI) were also measured as atherosclerosis assessments. All measurements were done before and six months after the rivaroxaban treatment. There was a significant increase in serum level of BAP compared to baseline (12.5 ± 4.6 to 13.4 ± 4.1 U/L, P < 0.01). In contrast, there was a significant decrease in the serum level of ucOC (9.5 ± 5.0 to 2.7 ± 1.3 ng/ml, P < 0.01). Also, in the ucOC levels, there was a significant negative correlation between baseline values and baseline to 6-months changes in high ucOC group (r = -0.97, P < 0.01). The atherosclerosis- and osteoporosis-related biomarker, serum level of OPN were significantly decreased compared to baseline (268.3 ± 46.8 to 253.4 ± 47.1 ng/ml, P < 0.01). AI and PWV were significantly decreased after 6 months of treatment with rivaroxaban (33.9 ± 18.4 to 24.7 ± 18.4%, P = 0.04; 1638.8 ± 223.0 to 1613.0 ± 250.1 m/s, P = 0.03, respectively). Switching to rivaroxaban from warfarin in patients with atrial fibrillation was associated with an increase of bone formation markers and a decrease of bone resorption markers, and also improvements of PWV and AI.

Targeting vasoactive peptides for managing calcific aortic valve disease

Calcific aortic valve disease (CAVD) represents a spectrum of disease spanning from milder degrees of calcification of valve leaflets, i.e., aortic sclerosis, to severe calcification i.e., aortic stenosis (AS) with hemodynamic instability. The prevalence of CAVD is increasing rapidly due to the aging of the population, being up to 2.8% among patients over 75 years of age. Even without significant aortic valve stenosis, aortic sclerosis is associated with a 50% increased risk of myocardial infarction and death from cardiovascular causes. To date, there is no pharmacological treatment available to reverse or hinder the progression of CAVD. So far, the cholesterol-lowering therapies (statins) and renin-angiotensin system (RAS) blocking drugs have been the major pharmacological agents investigated for treatment of CAVD. Especially angiotensin receptor blockers (ARB)s and angiotensin convertase enzyme inhibitors (ACEI)s, have been under active investigation in clinical trials, but have proven to be unsuccessful in slowing the progression of CAVD. Several studies have suggested that other vasoactive hormones, including endothelin and apelin systems are also associated with development of AS. In the present review, we discuss the role of vasoactive factors in the pathogenesis of CAVD as novel pharmacological targets for the treatment of aortic valve calcification. Key messages Vasoactive factors are involved in the progression of calcific aortic valve disease. Endothelin and renin-angiotensin systems seem to be most prominent targets for therapeutic interventions in the view of valvular pathogenesis. Circulating vasoactive factors may provide targets for diagnostic tools of calcified aortic valve disease.

Predictors of abdominal aortic calcification progression in patients with chronic kidney disease without hemodialysis

BACKGROUND AND AIMS

Abdominal aortic calcification (AAC) is an important predictor of cardiovascular mortality in patients with chronic kidney disease (CKD). However, little is known regarding AAC progression in these patients. This study aimed to identify risk factors associated with AAC progression in patients with CKD without hemodialysis.

METHODS

We recruited 141 asymptomatic patients with CKD without hemodialysis [median estimated glomerular filtration rate (eGFR), 40.3 mL/min/1.73 m²] and evaluated the progression of the abdominal aortic calcification index (ACI) over 3 years. To identify risk factors contributing to the rate of ACI progression, the associations between baseline clinical characteristics and annual change in ACI for each CKD category were analyzed. The annual change of ACI (ΔACI/year) was calculated as follows: (second ACI - first ACI)/duration between the two evaluations.

RESULTS

Median ΔACI/year values significantly increased in advanced CKD stages (0.73%, 0.87%, and 2.24%/year for CKD stages G1-2, G3, and G4-5, respectively; p for trend = 0.041). The only independent risk factor for AAC progression in mild to moderate CKD (G1-3, eGFR ≥ 30 mL/min/1.73 m²) was pulse pressure level (β = 0.258, p = 0.012). In contrast, parathyroid hormone (PTH) level was significantly correlated with ΔACI/year (β = 0.426, p = 0.007) among patients with advanced CKD (G4-5, eGFR < 30 mL/min/1.73 m²).

CONCLUSIONS

This study suggests that the AAC progression rate was significantly accelerated in patients with advanced CKD. In addition, measuring PTH is useful to evaluate both bone turnover and AAC progression in patients with advanced CKD.

Mechanisms of ectopic calcification: implications for diabetic vasculopathy

Vascular calcification (VC) is the deposition of calcium/phosphate in the vasculature, which portends a worse clinical outcome and predicts major adverse cardiovascular events. VC is an active process initiated and regulated via a variety of molecular signalling pathways. There are mainly two types of calcifications: the media VC and the intima VC. All major risk factors for cardiovascular disease (CVD) have been linked to the presence/development of VC. Besides the risk factors, a genetic component is also operative to determine arterial calcification. Several events take place before VC is established, including inflammation, trans-differentiation of vascular cells and homing of circulating pro-calcific cells. Diabetes is an important predisposing factor for VC. Compared with non-diabetic subjects, patients with diabetes show increased VC and higher expression of bone-related proteins in the medial layer of the vessels. In this review we will highlight the mechanisms underlying vascular calcification in diabetic patients.

Angiotensin II prevents calcification in vascular smooth muscle cells by enhancing magnesium influx

BACKGROUND

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD). Low magnesium levels are associated with VC, and recent in vitro studies confirm a protective role of magnesium, which is mediated by its entry into the VSMCs through the Transient Receptor Potential Melastatin 7 (TRPM7) channel. The role of Angiotensin II (Ang II) on VC is still unclear. As Ang II is able to stimulate TRPM7 activity, we hypothesize that it might prevent VC. Thus, the aim of this study was to dissect the direct effect of Ang II on VC.

MATERIALS AND METHODS

We worked with a model of high phosphate (HP)-induced calcification in human aortic smooth muscle cells, which resembles the CKD-related VC.

RESULTS

Addition of Ang II to cells growing in HP decreased calcification, which was associated with the upregulation of the osteogenic factors BMP2, Runx2/Cbfa1, Osterix and ALP. A reduction of magnesium entry into the HP-calcifying cells was found. The treatment with Ang II avoided this reduction, which was reversed by the cotreatment with the TRPM7-inhibitor 2-APB. The protective effect of Ang II was related to AT1R-induced ERK1/2 MAPKinase activation. HP-induced calcification was also associated with the upregulation of the canonical Wnt/beta-catenin pathway, while its downregulation was related to attenuation of calcification by Ang II.

CONCLUSION

As hypothesized, Ang II prevented phosphate-induced calcification in VSMCs, which appears mediated by the increase of magnesium influx and by the activation of the ERK1/2 and the inhibition of the canonical Wnt/beta-catenin signalling pathways.

Telmisartan to reduce cardiovascular risk in older HIV-infected adults: a pilot study

BACKGROUND

HIV-infected persons are at increased cardiovascular disease (CVD) risk, but traditional CVD therapies are understudied in this population. Telmisartan is an angiotensin receptor blocker (ARB) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist that improves endothelial function and cardiovascular mortality in HIV-uninfected populations. We assessed the effects of telmisartan on endothelial function in older HIV-infected persons at risk for CVD in a small pilot study.

METHODS

HIV-infected individuals≥50 years old on suppressive antiretroviral therapy (ART) with ≥1 traditional CVD risk factor received open-label telmisartan 80 mg daily for 6 weeks. Brachial artery flow-mediated dilation (FMD) measured endothelial function. The primary endpoint was 6-week change in maximum relative FMD.

RESULTS

Seventeen participants enrolled; 16 completed all evaluations (88% men, 65% non-White, median age 60 years, CD4+T lymphocyte count 625 cells/mm3). Antiretroviral therapy included 71% protease inhibitor (PI), 29% non-nucleoside reverse transcriptase inhibitor (NNRTI), 29% integrase inhibitor, 65% tenofovir, and 29% abacavir. Cardiovascular disease risk factor prevalence included 76% hyperlipidemia, 65% hypertension, 18% smoking, and 12% diabetes mellitus. After 6 weeks, statistically significant blood pressure changes were observed (systolic-16.0 mmHg, diastolic-6.0 mmHg) without significant changes in FMD. In subset analyses, FMD increased more among abacavir-treated, PI-treated, and non-smoking participants.

CONCLUSIONS

No significant FMD changes were observed after 6 weeks of telmisartan therapy; however, abacavir- and PI-treated participants and non-smokers showed greater FMD increases. Additional studies are needed to explore the effects of telmisartan on endothelial function among HIV-infected individuals with traditional CVD and/or ART-specific risk factors.

Pathologic Findings in NEMO Deficiency: A Surgical and Autopsy Survey

Hypomorphic mutations in nuclear factor κB (NF-κB) essential modulator (NEMO), encoded by IKBKG, lead to a variable combined immunodeficiency, which puts patients at risk of early death from infectious complications. The spectrum of clinical manifestations includes inflammatory disorders, especially colitis. Because of the multiple complications of NEMO deficiency, a variety of biopsy, excisional, and autopsy materials from these patients may be subject to pathologic examination. Therefore, using samples from a cohort of patients with this disorder, we aimed to survey the pathologic spectrum of NEMO deficiency and search for correlations between specific genotypes and phenotypes. Clinical and laboratory data, mutation analysis, and pathology from 13 patients were examined, including 6 autopsies. No specific genotype-pathology correlation was identified. However, we confirmed an association between ectodermal dysplasia and inflammatory conditions. We found no characteristic pathology to identify patients with NEMO deficiency; therefore, history, physical examination, and specific infections must remain the clues to suggest the diagnosis. Variability among patients and by infection makes the pathologic recognition of NEMO deficiency challenging.

Long-term warfarin therapy and biomarkers for osteoporosis and atherosclerosis

Background

Stroke prevention by warfarin, a vitamin K antagonist, has been an integral part in the management of atrial fibrillation. Vitamin K-dependent matrix Gla protein (MGP) has been known as a potent inhibitor of arterial calcification and osteoporosis. Therefore, we hypothesized that warfarin therapy affects bone mineral metabolism, vascular calcification, and vascular endothelial dysfunction.

Methods

We studied 42 atrial fibrillation patients at high-risk for atherosclerosis having one or more coronary risk factors. Twenty-four patients had been treated with warfarin for at least 12 months (WF group), and 18 patients without warfarin (non-WF group). Bone alkaline phosphatase (BAP) and under carboxylated osteocalcin (ucOC) and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured as bone metabolism markers. Reactive hyperemia-peripheral arterial tonometry (RH-PAT) index measured by Endo-PAT2000 was used as an indicator of vascular endothelial function.

Results

There were no significant differences in patient background characteristics and other clinical indicators between the two groups. In WF group, the ucOC levels were significantly higher than those in the non-WF group (10.3 ± 0.8 vs. 3.4 ± 0.9 ng/mL; P < 0.01), similarly, the RANKL levels in the WF group were higher than those in the non-WF group (0.60 ± 0.06 vs. 0.37 ± 0.05 ng/mL; P = 0.007). Moreover, RH-PAT index was significantly lower in the WF group compared to those in the non-WF group (1.48 ± 0.11 vs. 1.88 ± 0.12; P = 0.017).

Conclusions

Long-term warfarin therapy may be associated with bone mineral loss and vascular calcification in 60–80 year old hypertensive patients.

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Stroke prevention by warfarin has been an integral part in the management of atrial fibrillation.

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Warfarin prevents the activation of vitamin K-dependent proteins, MGP and Gas-6.

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Long-term warfarin therapy increases the serum levels of ucOC and RANKL.

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Long-term warfarin therapy is associated with vascular endothelial dysfunction.

Molecular Mechanisms of Vascular Calcification in Chronic Kidney Disease: The Link between Bone and the Vasculature

Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD) and increases mortality in those patients. Impaired calcium and phosphate homeostasis, increased oxidative stress, and loss of calcification inhibitors have been linked to vascular calcification in CKD. Additionally, impaired bone may perturb serum calcium/phosphate and their key regulator, parathyroid hormone, thus contributing to increased vascular calcification in CKD. Therapeutic approaches for CKD, such as phosphate binders and bisphosphonates, have been shown to ameliorate bone loss as well as vascular calcification. The precise mechanisms responsible for vascular calcification in CKD and the contribution of bone metabolism to vascular calcification have not been elucidated. This review discusses the role of systemic uremic factors and impaired bone metabolism in the pathogenesis of vascular calcification in CKD. The regulation of the key osteogenic transcription factor Runt-related transcription factor 2 (Runx2) and the emerging role of Runx2-dependent receptor activator of nuclear factor kappa-B ligand (RANKL) in vascular calcification of CKD are emphasized.

Vascular biology of ageing-Implications in hypertension

Ageing is associated with functional, structural and mechanical changes in arteries that closely resemble the vascular alterations in hypertension. Characteristic features of large and small arteries that occur with ageing and during the development of hypertension include endothelial dysfunction, vascular remodelling, inflammation, calcification and increased stiffness. Arterial changes in young hypertensive patients mimic those in old normotensive individuals. Hypertension accelerates and augments age-related vascular remodelling and dysfunction, and ageing may impact on the severity of vascular damage in hypertension, indicating close interactions between biological ageing and blood pressure elevation. Molecular and cellular mechanisms underlying vascular alterations in ageing and hypertension are common and include aberrant signal transduction, oxidative stress and activation of pro-inflammatory and pro-fibrotic transcription factors. Strategies to suppress age-associated vascular changes could ameliorate vascular damage associated with hypertension. An overview on the vascular biology of ageing and hypertension is presented and novel molecular mechanisms contributing to these processes are discussed. The complex interaction between biological ageing and blood pressure elevation on the vasculature is highlighted. This article is part of a Special Issue entitled: CV Ageing.

Angiotensin II and vascular injury

Vascular injury, characterized by endothelial dysfunction, structural remodelling, inflammation and fibrosis, plays an important role in cardiovascular diseases. Cellular processes underlying this include altered vascular smooth muscle cell (VSMC) growth/apoptosis, fibrosis, increased contractility and vascular calcification. Associated with these events is VSMC differentiation and phenotypic switching from a contractile to a proliferative/secretory phenotype. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Among the many factors involved in vascular injury is Ang II. Ang II, previously thought to be the sole biologically active downstream peptide of the renin-angiotensin system (RAS), is converted to smaller peptides, [Ang III, Ang IV, Ang-(1-7)], that are functional and that modulate vascular tone and structure. The actions of Ang II are mediated via signalling pathways activated upon binding to AT1R and AT2R. AT1R activation induces effects through PLC-IP3-DAG, MAP kinases, tyrosine kinases, tyrosine phosphatases and RhoA/Rho kinase. Ang II elicits many of its (patho)physiological actions by stimulating reactive oxygen species (ROS) generation through activation of vascular NAD(P)H oxidase (Nox). ROS in turn influence redox-sensitive signalling molecules. Here we discuss the role of Ang II in vascular injury, focusing on molecular mechanisms and cellular processes. Implications in vascular remodelling, inflammation, calcification and atherosclerosis are highlighted.

Exenatide can inhibit calcification of human VSMCs through the NF-kappaB/RANKL signaling pathway

Background

Arterial calcification is an important pathological change of diabetic vascular complication. Osteoblastic differentiation of vascular smooth muscle cells (VSMCs) plays an important cytopathologic role in arterial calcification. The glucagon-like peptide-1 receptor agonists (GLP-1RA), a novel type of antidiabetic drugs, exert cardioprotective effects through the GLP-1 receptor (GLP-1R). However, the question of whether or not GLP-1RA regulates osteoblastic differentiation and calcification of VSMCs has not been answered, and the associated molecular mechanisms have not been examined.

Methods

Calcifying VSMCs (CVSMCs) were isolated from cultured human arterial smooth muscle cells through limiting dilution and cloning. The extent of matrix mineralization was measured by Alizarin Red S staining. Protein expression and phosphorylation were detected by Western blot. Gene expression of receptor activator of nuclear factor-κB ligand (RANKL) was silenced by small interference RNA (siRNA).

Results

Exenatide, an agonist of GLP-1 receptor, attenuated β-glycerol phosphate (β-GP) induced osteoblastic differentiation and calcification of human CVSMCs in a dose- and time-dependent manner. RANKL siRNA also inhibited osteoblastic differentiation and calcification. Exenatide decreased the expression of RANKL in a dose-dependent manner. 1,25 vitD₃ (an activator of RANKL) upregulated, whereas BAY11-7082 (an inhibitor of NF-κB) downregulated RANKL, alkaline phosphatase (ALP), osteocalcin (OC), and core binding factor α1 (Runx2) protein levels and reduced mineralization in human CVSMCs. Exenatide decreased p-NF-κB and increased p-AMPKα levels in human CVSMCs 48 h after treatment. Significant decrease in p-NF-κB (p-Ser²⁷⁶, p-Ser⁵³⁶) level was observed in cells treated with exenatide or exenatide + BAY11-7082.

Conclusion

GLP-1RA exenatide can inhibit human VSMCs calcification through NF-κB/RANKL signaling.

OPG/RANKL/RANK axis is a critical inflammatory signaling system in ischemic brain in mice

Osteoprotegerin (OPG) is a soluble secreted protein and a decoy receptor, which inhibits a receptor activator of nuclear factor κB (NF-κB) ligand (RANKL)/the receptor activator of NF-κB (RANK) signaling. Recent clinical studies have shown that a high-serum-OPG level is associated with unfavorable outcome in ischemic stroke, but it is unclear whether OPG is a culprit or an innocent bystander. Here we demonstrate that enhanced RANKL/RANK signaling in OPG(-/-) mice or recombinant RANKL-treated mice contributed to the reduction of infarct volume and brain edema via reduced postischemic inflammation. On the contrary, infarct volume was increased by reduced RANKL/RANK signaling in OPG(-/-) mice and WT mice treated with anti-RANKL neutralizing antibody. OPG, RANKL, and RANK mRNA were increased in the acute stage and were expressed in activated microglia and macrophages. Although enhanced RANKL/RANK signaling had no effects in glutamate, CoCl2, or H2O2-stimulated neuronal culture, enhanced RANKL/RANK signaling showed neuroprotective effects with reduced expression in inflammatory cytokines in LPS-stimulated neuron-glia mixed culture, suggesting that RANKL/RANK signaling can attenuate inflammation through a Toll-like receptor signaling pathway in microglia. Our findings propose that increased OPG could be a causal factor of reducing RANKL/RANK signaling and increasing postischemic inflammation. Thus, the OPG/RANKL/RANK axis plays critical roles in controlling inflammation in ischemic brains.

Inflammatory, metabolic, and genetic mechanisms of vascular calcification

This review centers on updating the active research area of vascular calcification. This pathology underlies substantial cardiovascular morbidity and mortality, through adverse mechanical effects on vascular compliance, vasomotion, and, most likely, plaque stability. Biomineralization is a complex, regulated process occurring widely throughout nature. Decades ago, its presence in the vasculature was considered a mere curiosity and an unregulated, dystrophic process that does not involve biological mechanisms. Although it remains controversial whether the process has any adaptive value or past evolutionary advantage, substantial advances have been made in understanding the biological mechanisms driving the process. Different types of calcific vasculopathy, such as inflammatory versus metabolic, have parallel mechanisms in skeletal bone calcification, such as intramembranous and endochondral ossification. Recent work has identified important regulatory roles for inflammation, oxidized lipids, elastin, alkaline phosphatase, osteoprogenitor cells, matrix γ-carboxyglutamic acid protein, transglutaminase, osteoclastic regulatory factors, phosphate regulatory hormones and receptors, apoptosis, prelamin A, autophagy, and microvesicles or microparticles similar to the matrix vesicles of skeletal bone. Recent work has uncovered fascinating interactions between matrix γ-carboxyglutamic acid protein, vitamin K, warfarin, and transport proteins. And, lastly, recent breakthroughs in inherited forms of calcific vasculopathy have identified the genes responsible as well as an unexpected overlap of phenotypes. Until recently, vascular calcification was considered a purely degenerative, unregulated process. Since then, investigative groups around the world have identified a wide range of causative mechanisms and regulatory pathways, and some of the recent developments are highlighted in this review.