Anti-ANKH (aa 108-157) polyclonal antibody

Introduction: Chondrocalcinosis (CC) most commonly results from calcium pyrophosphate crystal deposition (CPPD). The objective of this study is to examine the association between candidate single-nucleotide polymorphisms (SNPs) and radiographic CC. Methods: SNPs in ankylosis human (ANKH), high ferritin (HFE), tissue non-specific alkaline phosphatase (TNAP), ecto-neucleotide pyrophosphatase 1 (ENPP1), and transferrin (TE) genes were genotyped in participants of the Genetics of Osteoarthritis and Lifestyle (GOAL) and Nottingham Osteoarthritis Case-Control studies. Adjusted genotype odds ratio (aOR(GENOTYPE)), the OR for association between one additional minor allele and CC, was calculated and adjusted for age, gender, body mass index (BMI), and osteoarthritis (OA) by using binary logistic regression. Statistical significance was set at P <= 0.003 after Bonferroni correction for multiple tests. Results: The -4bpG > A polymorphism in the 5' untranslated region (5' UTR) of ANKH associated with CC after Bonferroni correction. This was independent of age, gender, OA, and BMI; aOR(GENOTYPE) (95% confidence interval, or CI) was 1.39 (1.14-1.69) (P = 0.001). rs3045 and rs875525, two other SNPs in ANKH, associated with CC; aOR(GENOTYPE) (95% CI) values were 1.31 (1.09-1.58) (P = 0.005) and 1.18 (1.03-1.35) (P = 0.015), respectively; however, this was non-significant after Bonferroni correction. Conclusions: This study validates the association between a functional polymorphism in the 5' UTR of ANKH and CC and shows for the first time that this is independent of age and OA - the two key risk factors for CC. It shows that other SNPs in ANKH may also associate with CC. This supports the role of extracellular inorganic pyrophosphate in the pathogenesis of CC. The findings of this hospital-based study require replication in a community-based population.

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-kappa B) induction, a mediator of inflammation, might promote vascular calcification. Activation of NF-kappa B 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-kappa B 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-kappa B and decreased ANKH levels. In contrast, the inhibition of NF-kappa B 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-kappa B and decreased ANKH expression. Thus, TNF-activated NF-kappa B promotes inflammation-accelerated vascular calcification by inhibiting ankylosis protein homolog expression and consequent pyrophosphate secretion. Kidney International (2012) 82, 34-44; doi: 10.1038/ki.2012.40; published online 21 March 2012