Vascular calcification (VC) is highly correlated with increased morbidity and mortality in advanced chronic kidney disease (CKD) patients. Allosteric modulation of the calcium-sensing receptor (CaR) by calcimimetics inhibits VC in animal models of advanced CKD. Here, we investigated the expression of the CaR in the vasculature and tested the ability of calcimimetics to prevent vascular smooth muscle cell (VSMC) calcification in vitro. Immunohistochemical staining demonstrated that CaR protein is present in VSMC in normal, non-calcified human arteries. In contrast, low levels of CaR immunoreactivity were detected in atherosclerotic, calcified arteries. Immunfluorescence and immunoblotting revealed that CaR protein was also expressed by human and bovine VSMC in vitro. Acute stimulation of VSMC with increased Ca²⁺ stimulated extracellular signal-regulated kinase (ERK1/2) phosphorylation, suggesting that the VSMC CaR is functional. VSMC CaR expression decreased when these cells deposited a mineralized matrix or following 24 h incubation in mineralization medium with increased (i.e. 1.8 or 2.5 mM) Ca²⁺. Culturing VSMC in mineralization medium containing 1.8 and 2.5 mM Ca²⁺ or with the membrane-impermeant CaR agonist Gd³⁺ enhanced mineral deposition compared with that observed in 1.2 mM Ca²⁺. Over-expression of dominant-negative (R185Q) CaR enhanced, whereas the calcimimetic R-568 attenuated, VSMC mineral deposition. These results demonstrate that: (i) VSMCs express a functional CaR; (ii) a reduction in CaR expression is associated with increased mineralization in vivo and in vitro; (iii) calcimimetics decrease mineral deposition by VSMC. These data suggest that calcimimetics may inhibit the development of VC in CKD patients.

OBJECTIVE The receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) signaling pathway (RANKL/RANK/OPG signaling) is implicated in the osteolysis associated with diabetic Charcot neuroarthropathy (CN); however, the links with medial arterial calcification (MAC) seen in people with CN are unclear. This study aimed to investigate the role of RANKL/OPG in MAC in patients with CN. RESEARCH DESIGN AND METHODS Enzyme-linked immunosorbent assay and Bio-plex multiarray technology were used to quantify a range of cytokines, including RANKL and OPG in sera from 10 patients with diabetes, 12 patients with CN, and 5 healthy volunteers. Human tibial artery segments were immunohistochemically stained with Alizarin red and human RANKL antibody. Human vascular smooth muscle cells (VSMCs) were also explanted from arterial segments for in vitro studies. RESULTS We demonstrate colocalization and upregulation of RANKL expression in areas displaying MAC. Systemic levels of RANKL, OPG, and inflammatory cytokines (interleukin-8, granulocyte colony–stimulating factor) were elevated in those with CN compared with diabetic patients and healthy control subjects. Human VSMCs cultured in CN serum showed accelerated osteoblastic differentiation (alkaline phosphatase activity) and mineralization (alizarin red staining) compared with cells treated with diabetic or control serum (P < 0.05). Coincubation with OPG, the decoy receptor for RANKL, attenuated osteogenic differentiation of VSMCs and was independent of a high calcium-phosphate milieu. The accelerated mineralization induced by RANKL and CN serum correlated with nuclear translocation of nuclear factor-κB, a process abrogated by OPG. CONCLUSIONS Our data provide direct evidence that RANKL/RANK/OPG signaling is modulated in patients with CN and plays a role in vascular calcification. This study highlights this pathway as a potential target for intervention.

A β-galactosidase gene expression construct was used to investigate the effectiveness of gene delivery and expression when DNA/liposome complexes were topically applied to mouse skin in vivo. DNA was complexed with a commercial preparation of N-[1-(2,3-dioleoyloxy) propyl]-N, N, N-trimethyl-ammonium-methyl-sulphate (DOTAP) in a ratio of 1:1.6 (w/w). The DNA rapidly penetrated the skin and was expressed in the epidermis, dermis and hair follicles. A DNA concentration of 267 μg/ml DNA was found to be optimal for efficient transfection. Expression was seen as early as 6 h post-application, persisted at high levels 24 and 48 h post-treatment, but was markedly reduced by 7 days after application. In conclusion, utilising a commercially available liposome preparation, topically-applied DNA/liposome complexes can be efficiently delivered and expressed in several cell types within the skin. This simple, non-invasive technique may have implications for a number of gene therapy applications.

Endothelial microparticles (EMPs) are endothelium‐derived submicron vesicles that are released in response to diverse stimuli and are elevated in cardiovascular disease, which is correlated with risk factors. This study investigates the effect of EMPs on endothelial cell function and dysfunction in a model of free fatty acid (FFA) palmitate‐induced oxidative stress. EMPs were generated from TNF‐α‐stimulated HUVECs and quantified by using flow cytometry. HUVECs were treated with and without palmitate in the presence or absence of EMPs. EMPs were found to carry functional eNOS and to protect against oxidative stress by positively regulating eNOS/Akt signaling, which restored NO production, increased superoxide dismutase and catalase, and suppressed NADPH oxidase and reactive oxygen species (ROS) production, with the involvement of NF‐erythroid 2‐related factor 2 and heme oxygenase‐1. Conversely, under normal conditions, EMPs reduced NO release and increased ROS and redox‐sensitive marker expression. In addition, functional assays using EMP‐treated mouse aortic rings that were performed under homeostatic conditions demonstrated a decline in endothelium‐dependent vasodilatation, but restored the functional response under lipid‐induced oxidative stress. These data indicate that EMPs harbor functional eNOS and potentially play a role in the feedback loop of damage and repair during homeostasis, but are also effective in protecting against FFA‐induced oxidative stress; thus, EMP function is reflected by the microenvironment.— Mahmoud, A. M., Wilkinson, F. L., McCarthy, E. M., Moreno‐Martinez, D., Langford‐Smith, A., Romero, M., Duarte, J., Alexander, M. Y. Endothelial microparticles prevent lipid‐induced endothelial damage via Akt/eNOS signaling and reduced oxidative stress. FASEB J. 31, 4636–4648 (2017). www.fasebj.org

Age is a significant risk factor for the development of vascular diseases, such as atherosclerosis. Although pharmacological treatments, including statins and anti-hypertensive drugs, have improved the prognosis for patients with cardiovascular disease, it remains a leading cause of mortality in those aged 65 years and over. Furthermore, given the increased life expectancy of the population in developed countries, there is a clear need for alternative treatment strategies. Consequently, the relationship between aging and progenitor cell-mediated repair is of great interest. Endothelial progenitor cells (EPCs) play an integral role in the cellular repair mechanisms for endothelial regeneration and maintenance. However, EPCs are subject to age-associated changes that diminish their number in circulation and function, thereby enhancing vascular disease risk. A great deal of research is aimed at developing strategies to harness the regenerative capacity of these cells. In this review, we discuss the current understanding of the cells termed “EPCs,” examine the impact of age on EPC-mediated repair and identify therapeutic targets with potential for attenuating the age-related decline in vascular health via beneficial actions on EPCs.