Plasma Membrane Calcium ATPase Overexpression in Arterial Smooth Muscle Increases Vasomotor Responsiveness and Blood Pressure

Abstract

Abstract-In vascular smooth muscle cells (SMCs), several mechanisms act in concert to regulate the intracellular calcium concentration [Ca 2ϩ ] i , which may in turn affect vascular tone. One such mechanism is the extrusion of Ca 2ϩ by the plasma membrane calcium ATPase (PMCA). To address, in particular, the role of the neuronal nitric oxide synthase (nNOS)-associating isoform PMCA4b in regulating vascular tone, a doxycycline-responsive transgene for human PMCA4b was overexpressed in arterial SMCs of mice. Overexpression of hPMCA4b resulted in a 2-fold increase in total aortic PMCA4 protein expression and significant real-time RT-PCR-documented differences in the levels of endogenous mouse PMCA1, PMCA4, SERCA2, and IP3R1 gene expression in arterial SMCs. Whereas no significant difference in basal [Ca 2ϩ ] i or Ca 2ϩ sensitivity was observed in vascular SMCs or mesenteric arteries, respectively, from hPMCA4b-overexpressing versus control mice, hPMCA4b-overexpressing mice revealed a reduced set-point and increased extent of myogenic response and heightened sensitivity to vasoconstrictors. Treatment of arteries with an nNOS inhibitor resulted in a reduced set-point and increased extent of the myogenic response in control but not hPMCA4b-overexpressing mice. Moreover, aortic SMCs from hPMCA4b-overexpressing mice exhibited reduced levels of cGMP under both basal and phenylephrine-stimulated conditions. These changes were associated with significant doxycycline-reversible elevations in blood pressure. Taken together, these data show that overexpression of hPMCA4b in arterial SMCs increases vascular reactivity and blood pressure, an effect that may be mediated in part by negative regulation of nNOS. Key Words: transgenic mice Ⅲ blood pressure Ⅲ nitric oxide synthase Ⅲ intracellular calcium Ⅲ myogenic tone H ypertension is a polygenic disease responsive to environmental factors. Although more than 50 genes have been implicated in the regulation of blood pressure, 1 the complexity of hypertension has been additionally revealed by studies suggesting that insertion or deletion of single genes can lead to either reduced or elevated blood pressure. 2 One hallmark of hypertension is increased peripheral resistance attributable to both structural and functional changes in resistance arteries. 3 On a functional level, peripheral resistance is a balance between vasodilator and vasoconstrictor mechanisms of vascular smooth muscle cells (SMCs), in turn dependent on the intracellular calcium concentration ([Ca 2ϩ ] i ) and the Ca 2ϩ sensitivity of the contractile apparatus. Homeostasis of Ca 2ϩ involves several distinct mechanisms, including the extrusion of Ca 2ϩ by plasma membrane calcium ATPase (PMCA). These high-affinity calmodulin-responsive Ca 2ϩ efflux pumps are P-type transport proteins encoded for by a family of 4 genes (PMCA1 through PMCA4). Both PMCA1 and PMCA4 are ubiquitously expressed, whereas PMCA2 and PMCA3 show cell-specific patterns of expression. 4 From these 4 genes, more than 20 distinct isoforms of PMCA ...

Recapitulation of two genomewide association studies on blood pressure and essential hypertension in the Korean population

“…ATP2B1 regulates the homeostasis of cellular calcium ion levels, which is important in controlling vascular smooth muscle contraction and dilation. 13,14 However, it has been difficult to speculate the exact role of ATP2B1 in physiology because of the large number of isoforms and the multiplicity of interacting molecules. 15 Related to its role in blood pressure, it is not clear yet whether ATP2B1 directly regulates the contraction and dilation of vascular smooth muscle by pumping out intracellular Ca ++ or it indirectly regulates the blood pressure by transmitting signals from vascular endothelial cells into the vascular smooth muscle cells.…”

Genetic variations in ATP2B1, CSK, ARSG and CSMD1 loci are related to blood pressure and/or hypertension in two Korean cohorts

“…The biological function of ATP2B1 involves the homeostasis of cellular calcium ion levels, which is known to control vascular smooth muscle contraction and dilation. 14,15 The SNP rs1378942 is located in the first intron of CSK (c-src tyrosine kinase) at chromosome position 15q23-25. Our results showed that rs1378942 is associated with SBP in both cohorts (meta-analysis, P ¼ 1.34 Â 10 À5 ).…”

Ca2+ clearance in smooth muscle: lessons from gene-altered mice

“…The latter is based on the PDZ domains in PMCA4b which lead to a complex with nitric oxide synthase I in caveolae of vascular smooth muscle (Schuh et al, 2001). PMCA gene-altered mice to date include gene-targeted PMCA1 , PMCA4 Schuh et al, 2004) and mice expressing PMCA4 using smooth muscle specific promoters (Gros et al, 2003;Schuh et al, 2003). At the level of PMCA mRNA message in mouse aorta, PMCA1 is reported to be approximately twice that of PMCA4, which is reversed in the PMCA4 smooth muscle specific transgenic.…”