Cyclosporin A Aggravates Calcification of Vascular Smooth Muscle Cells Under High-Glucose Conditions with a Calcifying Medium

Both high glucose and phosphate overload promote senescence-associated calcification of vascular muscle cells

PURPOSE

The NAD⁺-dependent deacetylase, sirtuin 1 (SIRT1), plays an important role in vascular calcification induced by high glucose and/or high phosphate levels. However, the mechanism by which SIRT1 regulates this process is still not fully understood. Thus, this study aimed to determine the role of high glucose and phosphate in vascular calcification and the molecular mechanisms underlying SIRT1 regulation.

METHODS

Vascular smooth muscle cells (VSMCs) were cultured under normal, high phosphate, and/or high-glucose conditions for 9 days. Alizarin red staining and calcification content analyses were used to determine calcium deposition. VSMC senescence was detected by β-galactosidase (SA-β-Gal) staining and p21 expression.

RESULTS

Mouse VSMCs exposed to high phosphate and high glucose in vitro showed increased calcification, which was correlated with the induction of cell senescence, as confirmed by the increased SA-β-galactosidase activity and p21 expression. SRT1720, an activator of SIRT1, inhibits p65 acetylation, the nuclear factor-κ-gene binding (NF-κB) pathway, and VSMC transdifferentiation, prevents senescence and reactive oxygen species (ROS) production, and reduces vascular calcification. In contrast, sirtinol, an inhibitor of SIRT1, increases p65 acetylation, activates the NF-κB pathway, induces vascular smooth muscle cell transdifferentiation and senescence, and promotes vascular calcification.

CONCLUSIONS

High glucose and high phosphate levels induce senescence and vascular calcification in VSMCs, and the combined effect of high glucose and phosphate can inhibit SIRT1 expression. SIRT1 inhibits vascular smooth muscle cell senescence and osteogenic differentiation by inhibiting NF-κB activity, thereby inhibiting vascular calcification.

Post-Transplant Cardiovascular Disease

Cardiovascular disease remains a leading cause of death and morbidity in kidney transplant recipients and a common reason for post-transplant hospitalization. Several traditional and nontraditional cardiovascular risk factors exist, and many of them present pretransplant and worsened, in part, due to the addition of immunosuppression post-transplant. We discuss optimal strategies for identification and treatment of these risk factors, including the emerging role of sodium-glucose cotransporter 2 inhibitors in post-transplant diabetes and cardiovascular disease. We present common types of cardiovascular disease observed after kidney transplant, including coronary artery disease, heart failure, pulmonary hypertension, arrhythmia, and valvular disease. We also discuss screening, treatment, and prevention of post-transplant cardiac disease. We highlight areas of future research, including the need for goals and best medications for risk factors, the role of biomarkers, and the role of screening and intervention.

Cardiovascular calcifications in kidney transplant recipients

Vascular and valvular calcifications are highly prevalent in kidney transplant recipients and are associated with an increased risk of cardiovascular events, which represent the leading cause of long-term mortality in these patients. However, cardiovascular calcification has been traditionally considered as a condition mostly associated with advanced chronic kidney disease stages and dialysis, and comparatively fewer studies have assessed its impact after kidney transplantation. Despite partial or complete resolution of uremia-associated metabolic derangements, kidney transplant recipients are still exposed to several pro-calcifying stimuli that favour the progression of pre-existing vascular calcifications or their de novo development. Traditional risk factors, bone mineral disorders, inflammation, immunosuppressive drugs and deficiency of calcification inhibitors may all play a role, and strategies to correct or minimize their effects are urgently needed. The aim of this work is to provide an overview of established and putative mediators involved in the pathogenesis of cardiovascular calcification in kidney transplantation, and to describe the clinical and radiological features of these forms. We also discuss current evidence on preventive strategies to delay the progression of cardiovascular calcifications in kidney transplant recipients, as well as novel therapeutic candidates to potentially prevent their long-term deleterious effects.

Calcium silicate bioactive ceramics induce osteogenesis through oncostatin M

Immune reactions are a key factor in determining the destiny of bone substitute materials after implantation. Macrophages, the most vital factor in the immune response affecting implants, are critical in bone formation, as well as bone biomaterial-mediated bone repair. Therefore, it is critical to design materials with osteoimmunomodulatory properties to reduce host-to-material inflammatory responses by inducing macrophage polarization. Our previous study showed that calcium silicate (CS) bioceramics could significantly promote osteogenesis. Herein, we further investigated the effects of CS on the behavior of macrophages and how macrophages regulated osteogenesis. Under CS extract stimulation, the macrophage phenotype was converted to the M2 extreme. Stimulation by a macrophage-conditioned medium that was pretreated by CS extracts resulted in a significant enhancement of osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), indicating the important role of macrophage polarization in biomaterial-induced osteogenesis. Mechanistically, oncostatin M (OSM) in the macrophage-conditioned medium promoted osteogenic differentiation of BMSCs through the ERK1/2 and JAK3 pathways. This in vivo study further demonstrated that CS bioceramics could stimulate osteogenesis better than β-TCP implants by accelerating new bone formation at defective sites in the femur. These findings improve our understanding of immune modulation of CS bioactive ceramics and facilitate strategies to improve the in vitro osteogenesis capability of bone substitute materials.

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Calcium silicate (CS) bioceramics significantly promoted osteogenesis by the regulating of macrophage polarization.

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ERK1/2 and JAK3 pathways mediated the osteogenic differentiation stimulated by CS.

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CS played a promising osteoimmunomodulatory agent for bone induction.

Rho-associated protein kinase and cyclophilin a are involved in inorganic phosphate-induced calcification signaling in vascular smooth muscle cells

Arterial calcification, a risk factor of cardiovascular events, develops with differentiation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells. Cyclophilin A (CypA) is a peptidyl-prolyl isomerase involved in cardiovascular diseases such as atherosclerosis and aortic aneurysms, and rho-associated protein kinase (ROCK) is involved in the pathogenesis of vascular calcification. CypA is secreted in a ROCK activity-dependent manner and works as a mitogen via autocrine or paracrine mechanisms in VSMCs. We examined the involvement of the ROCK-CypA axis in VSMC calcification induced by inorganic phosphate (Pi), a potent cell mineralization initiator. We found that Pi stimulated ROCK activity, CypA secretion, extracellular signal-regulated protein kinase (ERK) 1/2 phosphorylation, and runt-related transcription factor 2 expression, resulting in calcium accumulation in rat aortic smooth muscle cells (RASMCs). The ROCK inhibitor Y-27632 significantly suppressed Pi-induced CypA secretion, ERK1/2 phosphorylation, and calcium accumulation. Recombinant CypA was found to be associated with increased calcium accumulation in RASMCs. Based on these results, we suggest that autocrine CypA is mediated by ROCK activity and is involved in Pi-induced ERK1/2 phosphorylation following calcification signaling in RASMCs.