Extracellular calcium-sensing receptor is functionally expressed in human artery

Extracellular calcium-sensing receptor is functionally expressed in human artery. Am J Physiol Renal Physiol 293: F946-F955, 2007. First published May 30, 2007; doi:10.1152/ajprenal.00474.2006.- Accelerated medial calcification is a major cause of premature cardiovascular mortality in patients with chronic kidney disease (CKD). Evidence suggests that extracellular concentration of Ca-2 (+) and vascular smooth muscle cells may play a pivotal role in the pathogenesis of vascular calcification. The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that is expressed in a range of tissues, but characterization of its expression and function in the cardiovascular system is limited. Here we report the expression of CaSR mRNA (RT-PCR) and protein ( Western blotting and immunocytochemistry) in human aortic smooth muscle cells (HAoSMC). Treatment of HAoSMC with Ca2 (+) (0-5 mM; 0-30 min) or the CaSR agonists gentamycin and neomycin ( 0-300 mu M; 0-30 min) resulted in a dose- and time-dependent phosphorylation of ERK1/2. Gentamycin- and neomycin-mediated ERK1/2 stimulation was inhibited by pretreatment with PD-98059, an ERK-activating kinase 1 (MEK1) inhibitor, confirming specificity of the observed effects. ERK1/2 activation was inhibited in HAoSMC, with CaSR expression knocked down by transfection with specific small-interference RNA, which confirmed that the observed neomycin/gentamycininduced MEK1/ERK1/2 activation was mediated via the CaSR. CaSR mRNA and protein were also expressed in large and small arteries from normal subjects ( kidney donors) and patients with end-stage renal disease ( ESRD). The CaSR was detected in smooth muscle and endothelial cells. Expression was significantly lower in arteries from ESRD patients. In conclusion, these data not only demonstrate the presence of a functional CaSR in human artery but show a correlation between CaSR expression and progression of CKD.