Lanthanum Prevents High Phosphate-Induced Vascular Calcification by Preserving Vascular Smooth Muscle Lineage Markers
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Vascular calcification (VC) represents a major cardiovascular risk factor in chronic kidney disease patients. High phosphate (Pi) levels are strongly associated with VC in this population. Therefore, Pi binders are commonly used to control high Pi levels. The aim of this work was to study the mechanism of action of lanthanum chloride (LaCl3) on the progression of Pi-induced VC through its direct effect on vascular smooth muscle cells (VSMCs) in vitro. High Pi induced VSCM Ca deposition. We evaluated the action of LaCl3, compared to gadolinium chloride (GdCl3), and found different effects on the modulation of VSMC lineage markers, such as α-actin and SM22α. In fact, only LaCl3 preserved the expression of both VSMC lineage markers compared to high Pi-treated cells. Interestingly, both LaCl3 and GdCl3 reduced the high Pi-induced elevations of bone morphogenic protein 2 mRNA expression, with no reduction of the high core binding factor-alpha 1 mRNA levels observed in calcified VSMCs. Furthermore, we also found that only LaCl3 completely prevented the matrix GLA protein mRNA levels and osteonectin protein expression elevations induced by high Pi compared to GdCl3. Finally, LaCl3, in contrast to GdCl3, prevented the high Pi-induced downregulation of Axl, a membrane tyrosine kinase receptor involved in apoptosis. Thus, our results suggest that LaCl3 prevents VC by preserving VSMC lineage markers and by decreasing high Pi-induced osteoblastic differentiation.
KeywordsLanthanum Vascular calcification Phosphate Gadolinium
This research was supported in part by an investigator-supported trial grant from Shire Pharmaceuticals.
Fig. Suppl. I Effects of high phosphate on VSMCs, shown by electron microscopy. a Electron micrograph showing calcium electron-dense deposits in extracellular matrix between neighboring cells (arrows), 2,500 × original magnification. b A cytoplasmic process with calcium deposits close to the cell membrane, 10,000 × original magnification. Inset Higher magnification of the boxed area showing the remnant of an exocytosis vesicle on a membrane near a calcium deposit (JPG 196 kb)
Fig. Suppl. II Effects of lanthanum and gadolinium on VSMC marker expression during the progression of VC. VSMCs were cultured for 8, 9, or 12 days in calcification medium with 100°μM lanthanum or 50°μM gadolinium and challenged with 5 mM Pi α-Actin (a) and SM22 αc) protein expression was detected by immunoblotting analysis. Lane 1 Control VSMC (8 days); lane 2 5 mM Pi (8 days); lanes 3–5 100μM LaCl3 8, 9, and 12 days, respectively; lanes 6–8 50 μM GdCl3 8, 9, and 12 days, respectively. During progression of calcification lanthanum prevented, whereas gadolinium worsened, VSMC marker downregulation induced by Pi. Analysis of the intensity of the bands is shown for α actin (b) and SM22 α d). Representative bands of one of three different experiments are shown. Data are presented as mean ± SE of three different experiments (*p < 0.01) (JPG 56 kb)
Fig. Suppl. III Effects of lanthanum and gadolinium on Cbfα1/RUNX2 gene expression. VSMCs were cultured in calcification medium, and Cbfα1/RUNX2 mRNA expression was measured by RT-PCR. a Time course of Cbfα1/RUNX2 expression after challenge with 5 mM Pi. Four hours after Pi challenge there was a significant increase in Cbfα1/RUNX2 mRNA levels compared to the relative expression in normal VSMCs (t 0) (*p < 0.01). b Effect of lanthanum and gadolinium on Cbfα1/RUNX2 gene expression. Pretreatment with both 100 μM LaCl3 and 50 μM GdCl3 did not affect Cbfα1/RUNX2 levels at 4 hours after Pi challenge. Data are presented as mean ± SE of three different experiments (JPG 47 kb)
- 3.Hutchison AJ, Laville M, SPD405-313 Lanthanum Study Group (2008) Switching to lanthanum carbonate monotherapy provides effective phosphate control with a low tablet burden. Nephrol Dial Transplant 23(11):3677–3684Google Scholar
- 15.Raggi P, Chertow GM, Torres PU, et al., ADVANCE Study Group (2011) The ADVANCE study: a randomized study to evaluate the effects of cinacalcet plus low-dose vitamin D on vascular calcification in patients on hemodialysis. Nephrol Dial Transplant 26(4):1327–1339Google Scholar
- 19.Reynolds JL, Joannides AJ, Skepper JN et al (2004) Human vascular smooth muscle cells undergo vesicle-mediated calcification in response to changes in extracellular calcium and phosphate concentrations: a potential mechanism for accelerated vascular calcification in ESRD. J Am Soc Nephrol 15(11):2567–2857CrossRefGoogle Scholar