pyrophosphate and Atherosclerosis

Patients with chronic kidney disease have increased cardiovascular mortality from a combination of increased atherosclerotic disease, left ventricular hypertrophy and increased prevalence of vascular calcification (VC). Previously VC was thought to be a passive process which involved the deposition of calcium and phosphate into the vessel wall. However, recent studies have shown that VC is a highly regulated, cell-mediated process similar to bone formation, in that it is associated with expression of bone-related proteins, such as type I collagen and alkaline phosphatase. Animal and in vitro models of VC have shown that a multitude of factors including phosphate, matrix gla protein (MGP) and fetuin are involved in regulating VC. Certain factors induce calcification whereas others inhibit the process. Despite these insights, it is still not fully known how VC is regulated and a treatment for VC remains elusive. Ongoing research will hopefully elucidate these mechanisms and thereby produce targets for future therapeutic intervention. This review will highlight some of the scientific models of VC and how they have increased the understanding of this complex process.

Topics: Alkaline Phosphatase; alpha-Fetoproteins; Animals; Apoptosis; Atherosclerosis; Calcinosis; Calcium-Binding Proteins; Cardiovascular Diseases; Collagen Type I; Diphosphates; Disease Models, Animal; Extracellular Matrix Proteins; Humans; Hypertrophy, Left Ventricular; Inflammation; Kidney Failure, Chronic; Matrix Gla Protein; Mice; Osteopontin; Phosphorus; Prevalence; Risk Factors; Vascular Diseases; Vitamin D; Vitamins

(1) Background: Tissue non-specific alkaline phosphatase (TNAP) is suspected to induce atherosclerosis plaque calcification. TNAP, during physiological mineralization, hydrolyzes the mineralization inhibitor inorganic pyrophosphate (PP

Topics: Adenosine Triphosphate; Alkaline Phosphatase; Animals; Aorta; Ascorbic Acid; Atherosclerosis; Cell Transdifferentiation; Chondrocytes; Diphosphates; Glycerophosphates; Humans; Magnetic Resonance Spectroscopy; Mice; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphates; Vascular Calcification

Vascular calcification is a major risk factor of cardiovascular mortality, particularly for patients with end-stage renal disease and diabetes. Although chronic inflammation is one of the etiologic factors, the underlying mechanism is not fully understood. To clarify this, we studied how nuclear factor-kappa B (NF-κB) induction, a mediator of inflammation, might promote vascular calcification. Activation of NF-κB by tumor necrosis factor (TNF) promoted inorganic phosphate-induced calcification in human aortic smooth muscle cells. Pyrophosphate (an inhibitor of calcification) efflux to the extracellular matrix was suppressed along with the decreased expression of ankylosis protein homolog (ANKH), a transmembrane protein that controls pyrophosphate efflux of cells. The restoration of ANKH expression in these cells overcame the decreased pyrophosphate efflux and calcification. Tristetraprolin, a downstream product of NF-κB activation, may mediate destabilization of ANKH mRNA as its knockdown by shRNA increased ANKH expression and decreased calcification. Furthermore, a rat chronic renal failure model, with increased serum TNF levels, activated NF-κB and decreased ANKH levels. In contrast, the inhibition of NF-κB maintained ANKH expression and attenuated vascular calcification both in vivo and in vitro. Both human calcified atherosclerotic lesions and arteries from patients with chronic kidney disease had activated NF-κB and decreased ANKH expression. Thus, TNF-activated NF-κB promotes inflammation-accelerated vascular calcification by inhibiting ankylosis protein homolog expression and consequent pyrophosphate secretion.

Topics: Animals; Atherosclerosis; Diphosphates; Disease Models, Animal; Disease Progression; Down-Regulation; Genes, Reporter; HEK293 Cells; Humans; I-kappa B Proteins; Inflammation Mediators; Kidney Failure, Chronic; Male; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; NF-kappa B; NF-KappaB Inhibitor alpha; Osteogenesis; Phosphate Transport Proteins; Promoter Regions, Genetic; Rats; Rats, Wistar; RNA Interference; RNA Stability; Signal Transduction; Time Factors; Transfection; Tristetraprolin; Tumor Necrosis Factor-alpha; Vascular Calcification