The Calcimimetic Calindol Prevents High Phosphate-Induced Vascular Calcification by Upregulating Matrix GLA Protein

Abstract

Background: High serum phosphate (Pi) levels represent a major issue in dialysis patients, because associate with secondary hyperparathyroidism, vascular calcification (VC), and cardiovascular outcomes. In this population, calcimimetics are used to control secondary hyperparathyroidism, hyperphosphatemia, and, more recently, to delay the progression of VC. The aim of this in vitro study was to investigate the direct effects of the calcimimetic calindol on the progression of high Pi-induced VC. Methods: Rat vascular smooth muscle cells (VSMCs) were incubated with high Pi concentrations, and the effects of calindol were investigated on vascular calcium deposition and VSMC osteoblastic differentiation. Results: Calindol inhibited calcium deposition concentration-dependently with a maximal inhibition of 64.0 ± 5.2% achieved at 100 n<smlcap>M</smlcap>. Furthermore, calindol was able to partially prevent the high Pi-induced bone morphogenic protein 2 (BMP-2) expression upregulation (32.4 ± 4.6% of inhibition; p < 0.01). Interestingly, the pretreatment with calindol enhanced the matrix Gla protein (MGP) gene expression significantly, compared to high Pi-treated cells (40.2 ± 6.6% of increase, p < 0.01). Conclusions: In conclusion, we demonstrated that the calcimimetic calindol prevents high Pi-induced VC by affecting osteoblastic differentiation in vitro. In particular, the inhibitory effect of calindol on VC is probably due to its stimulatory role on the calcium-sensing receptor, leading to an increase in the synthesis of MGP by VSMCs.

Calcimimetics and outcomes in CKD

“…13 The mechanism behind the inhibitory effect of calcimimetics on vascular calcification could be a stimulation of matrix-gla protein (MGP) production by VSMC, as initially suggested by Farzaneh-Far et al 15 and subsequently supported by observations of others in rat and bovine VSMCs, respectively. 14, 16 However, in vitro activation of CaR by R-568 did not modify phosphate-enhanced MGP release in our experimental human VSMC model. 13 These apparent discrepancies may be due to the use of VSMC from different species, with possibly variable induction of bone morphogenic protein-2 (BMP-2) which is itself a regulator of MGP synthesis and may decrease MGP expression.…”

“…13 These apparent discrepancies may be due to the use of VSMC from different species, with possibly variable induction of bone morphogenic protein-2 (BMP-2) which is itself a regulator of MGP synthesis and may decrease MGP expression. 17 Of interest, in the study by Ciceri et al 14 using bovine VSMC, increased expression of BMP-2 under high medium phosphate conditions was effectively prevented by calindol. Another possibility of the apparently inconsistent findings is that in none of these in vitro studies the state of gamma-glutamyl carboxylation and phosphorylation of the MGP molecule was assessed.…”

“…The calcimimetics R-568 13 and calindol 14 have been shown to decrease VSMC calcification induced by high phosphate concentrations in culture medium. This decrease was abolished in CaR-siRNA-transfected cells.…”

Activation of the calcium-sensing receptor in human valvular interstitial cells promotes calcification

“…Indeed, calcimimetic stimulation of the CaSR in VSMCs delayed both Pi-and Ca 2+induced mineralization processes in in vitro studies [22,24,44]. In particular, CaSR activation protects VSMCs from the osteogenic transition and collagen secretion, and can favor synthesis of the matrix Gla protein [24,45]. In animal models, calcimimetics were even able to prevent vascular calcification in the absence of changes in the serum parathyroid hormone level [46].…”

Calcitriol Prevents In Vitro Vascular Smooth Muscle Cell Mineralization by Regulating Calcium-Sensing Receptor Expression

“…The mechanisms whereby CaSR activation prevents VC in VSMCs are not yet fully understood. They may involve a reduction in collagen secretion (12), a decrease in BMP2 expression (15), and an increase in MGP production (14,15). Based on these recent findings, we hypothesized that other local or systemic factors may be able to modulate the expression of CaSR and thereby interfere with the process of VSMCs mineralization.…”