Peritoneal delivery of sodium pyrophosphate blocks the progression of pre-existing vascular calcification in uremic apolipoprotein-E knockout mice.

Chronic kidney disease (CKD) is generally associated with disturbances of mineral and bone metabolism. They contribute to the development of vascular calcification (VC), a strong, independent predictor of cardiovascular risk. Pyrophosphate (PPi), an endogenous inhibitor of hydroxyapatite formation, has been shown to slow the progression of VC in uremic animals. Since in patients with CKD treatment is usually initiated for already existing calcifications, we aimed to compare the efficacy of PPi therapy with that of the phosphate binder sevelamer, using a uremic apolipoprotein-E knockout mouse model with advanced VCs. After CKD creation or sham surgery, 12-week-old female mice were randomized to one sham group and four CKD groups (n = 18-19/group). Treatment was initiated 8 weeks after left nephrectomy allowing prior VC development. Uremic groups received either intraperitoneal PPi (high dose, 1.65 mg/kg or low dose, 0.33 mg/kg per day), oral sevelamer (3 % in diet), or placebo treatment for 8 weeks. Both intima and media calcifications worsened with time in placebo-treated CKD mice, based on both quantitative image analysis and biochemical measurements. Progression of calcification between 8 and 16 weeks was entirely halted by PPi treatment, as it was by sevelamer treatment. PPi did not induce consistent bone histomorphometry changes. Finally, the beneficial vascular action of PPi probably involved mechanisms different from that of sevelamer. Further studies are needed to gain more precise insight into underlying mechanisms and to see whether PPi administration may also be useful in patients with CKD and VC.

Effects of pyrophosphate delivery in a peritoneal dialysis solution on bone tissue of apolipoprotein-E knockout mice with chronic kidney disease.

Vascular calcification (VC) is a risk factor for cardiovascular mortality in the setting of chronic kidney disease (CKD). Pyrophosphate (PPi), an endogenous molecule that inhibits hydroxyapatite crystal formation, has been shown to prevent the development of VC in animal models of CKD. However, the possibility of harmful effects of exogenous administration of PPi on bone requires further investigation. To this end, we examined by histomorphometry the bone of CKD mice after intraperitoneal PPi administration. After CKD creation or sham surgery, 10-week-old female apolipoprotein-E knockout (apoE(-/-)) mice were randomized to one non-CKD group or 4 CKD groups (n = 10-35/group) treated with placebo or three distinct doses of PPi, and fed with standard diet. Eight weeks later, the animals were killed. Serum and femurs were sampled. Femurs were processed for bone histomorphometry. Placebo-treated CKD mice had significantly higher values of osteoid volume, osteoid surface and bone formation rate than sham-placebo mice with normal renal function. Slightly higher osteoid values were observed in CKD mice in response to very low PPi dose (OV/BV, O.Th and ObS/BS) and, for one parameter measured, to high PPi dose (O.Th), compared to placebo-treated CKD mice. Treatment with PPi did not modify any other structural parameters. Mineral apposition rates, and other parameters of bone formation and resorption were not significantly different among the treated animal groups or control CKD placebo group. In conclusion, PPi does not appear to be deleterious to bone tissue in apoE(-/-) mice with CKD, although a possible stimulatory PPi effect on osteoid formation may be worth further investigation.

Farnesyltransferase inhibitor R115777 protects against vascular disease in uremic mice.

BACKGROUND: Atherosclerosis and vascular calcification are major contributors to cardiovascular morbidity and mortality among chronic kidney disease patients. The mevalonate pathway may play a role in this vascular pathology. Farnesyltransferase inhibitors such as R115777 block one branch of mevalonate pathway. We studied the effects of farnesyltransferase inhibitor R115777 on vascular disease in apolipoprotein E deficient mice with chronic renal failure and on mineral deposition in vitro. METHODS AND RESULTS: Female uremic and non-uremic apolipoprotein E deficient mice were randomly assigned to four groups and treated with either farnesyltransferase inhibitor R115777 or vehicle. Farnesyltransferase inhibitor R115777 inhibited protein prenylation in mice with chronic renal failure. It decreased aortic atheromatous lesion area and calcification in these animals, and reduced vascular nitrotyrosine expression and total collagen as well as collagen type I content. Proteomic analysis revealed that farnesyltransferase inhibitor corrected the chronic renal failure-associated increase in serum apolipoprotein IV and α globin, and the chronic renal failure-associated decrease in serum fetuin A. Farnesyltransferase inhibitor further inhibited type I collagen synthesis and reduced mineral deposition in vascular smooth muscle cells in vitro, probably involving Ras-Raf pathway. CONCLUSIONS: We show for the first time that farnesyltransferase inhibition slows vascular disease progression in chronic renal failure by both indirect systemic and direct local actions. This beneficial effect was mediated via a reduction in oxidative stress and favorable changes in vasoprotective peptides.

Effects of sevelamer treatment on cardiovascular abnormalities in mice with chronic renal failure.

Elevated serum phosphate and fibroblast growth factor 23 (FGF23) levels are associated with cardiovascular disease (CVD) in patients with chronic renal failure (CRF). The phosphate-binder sevelamer has been shown to decrease both phosphate and FGF23, but limited data indicate that sevelamer improves CRF-related CVD, such as diastolic dysfunction, left ventricular hypertrophy (LVH), and aortic stiffness. To gain additional information, we measured the effects of sevelamer on CVD in a murine model of CRF. Groups of CRF and sham-operated mice received regular chow or 3% sevelamer-HCl in the chow for 14 weeks, starting 6 weeks after the initiation of CRF or sham operation. After the first 8 weeks of sevelamer treatment, CRF mice had decreased serum phosphate levels and an improved aortic systolic expansion rate, pulse-wave velocity, and diastolic function, although LVH remained unchanged. Following an additional 6-week course of sevelamer, LVH had not progressed. The FGF23 serum level was not reduced by sevelamer until after 14 weeks of treatment. In multiple regression analysis, serum phosphate, but not FGF23, was independently correlated with LV diastolic function and mass. Thus, sevelamer first improved aortic stiffness and diastolic dysfunction and secondarily prevented LVH in mice with CRF. The phosphate-lowering, rather than FGF23-lowering, effect appears to be responsible for the observed cardiovascular improvement.

Inorganic phosphate accelerates the migration of vascular smooth muscle cells: evidence for the involvement of miR-223.

BACKGROUND: An elevated serum inorganic phosphate (Pi) level is a major risk factor for kidney disease and downstream vascular complications. We focused on the effect of Pi levels on human aortic vascular smooth muscle cells (VSMCs), with an emphasis on the role of microRNAs (miRNAs). METHODOLOGY/PRINCIPAL FINDINGS: Exposure of human primary VSMCs in vitro to pathological levels of Pi increased calcification, migration rate and concomitantly reduced cell proliferation and the amount of the actin cytoskeleton. These changes were evidenced by significant downregulation of miRNA-143 (miR-143) and miR-145 and concomitant upregulation of their targets and key markers in synthetic VSMCs, such as Krüppel-like factors-4 and -5 and versican. Interestingly, we also found that miR-223 (a marker of muscle damage and a key factor in osteoclast differentiation) is expressed in VSMCs and is significantly upregulated in Pi-treated cells. Over-expressing miR-223 in VSMCs increased proliferation and markedly enhanced VSMC migration. Additionally, we found that the expression of two of the known miR-223 targets, Mef2c and RhoB, was highly reduced in Pi treated as well as miR-223 over-expressing VSMCs. To complement these in vitro findings, we also observed significant downregulation of miR-143 and miR-145 and upregulation of miR-223 in aorta samples collected from ApoE knock-out mice, which display vascular calcification. CONCLUSIONS/SIGNIFICANCE: Our results suggest that (i) high levels of Pi increase VSMC migration and calcification, (ii) altered expression levels of miR-223 could play a part in this process and (iii) miR-223 is a potential new biomarker of VSMC damage.

Lanthanum carbonate, like sevelamer-HCl, retards the progression of vascular calcification and atherosclerosis in uremic apolipoprotein E-deficient mice.

BACKGROUND: Atherosclerosis and vascular calcification (VC) progression in chronic kidney disease is favored by disturbances of mineral metabolism. We compared the effect of phosphate binder lanthanum (La) carbonate with sevelamer-HCl on atherosclerosis, VC and bone structure and function in mice with chronic renal failure (CRF). METHODS: Apolipoprotein E-deficient (apoE(-/-)) mice were randomized to one non-CRF and three CRF groups, fed with standard diet (one non-CRF and one CRF) or diet supplemented with either 3% lanthanum carbonate (La3%) or 3% sevelamer-HCl (Sev3%). RESULTS: Both La3% and Sev3% supplemented CRF mice displayed a decrease of serum phosphorus, calcification at both intimal and medial aortic sites and atherosclerosis. This was associated with a reduction of plaque Type I collagen expression by both binders and of positive nitrotyrosine staining in response to sevelamer-HCl only. Increased mineral apposition and bone formation rates in unsupplemented CRF mice were reduced by Sev3% but not by La3%. CONCLUSIONS: The beneficial effects of La carbonate and sevelamer-HCl on the progression of VC and atherosclerosis in CRF mice could be mainly due to a decrease in phosphate retention and likewise a reduction of arterial Type I collagen expression. The effect of La carbonate differed from that of sevelamer-HCl in that it did not appear to exert its vascular effects via changes in oxidative stress or bone remodeling in the present model.

Upregulation of BAD, a pro-apoptotic protein of the BCL2 family, in vascular smooth muscle cells exposed to uremic conditions.

Chronic kidney disease (CKD) has recently emerged as a major risk factor for cardiovascular pathology. CKD patients display accelerated atherosclerotic process, leading to circulatory complications. However, it is currently not clear how uremic conditions accelerate atherosclerosis. Apoptosis is an important homeostatic regulator of vascular smooth cells under pathological conditions. In the present study, we explored the regulation of apoptosis in cells of the vascular wall in the uremic context. We analysed the expression and regulation of the proteins of the BCL2 family that play an essential role in apoptosis. Our results, obtained in mice and primary human smooth muscle cells exposed to two uremic toxins, point to the existence of an alteration in expression and function of one pro-apoptotic member of this family, the protein BAD. We explore the regulation of BAD by uremic toxins and report the sensitization of vascular smooth muscle cells to apoptosis upon BAD induction.

Tissue accumulation of lanthanum as compared to aluminum in rats with chronic renal failure--possible harmful effects after long-term exposure.

BACKGROUND: Lanthanum (La) carbonate is a new treatment for hyperphosphatemia. We tested the effects of oral La carbonate and aluminum hydroxide, respectively, on tissue accumulation and liver function in rats with chronic renal failure (CRF). METHODS: Adult male non-CRF and CRF rats were randomly assigned to 3 groups receiving either standard diet (St.D), or the same diet supplemented with 3% La carbonate (non-CRF La vs. CRF La) or 3% aluminum hydroxide (non-CRF Al vs. CRF Al). RESULTS: After 12 weeks, serum phosphorus was decreased in both CRF La and Al groups. Urinary La and Al excretion was increased in these two groups, and so was liver and bone La content, and liver Al content. Both total body and liver weight were decreased in CRF La and CRF Al rats. Liver cell proliferation was decreased in these groups, while plasma total alkaline phosphatases and alanine aminotransferase were increased. Hepatic total cytochrome p450 content was reduced in CRF La, but not in CRF Al rats. CONCLUSION: Long-term oral La overload in rats with CRF was associated with a decrease in liver (and total body) weight and mild alterations of liver function, as was Al overload, possibly as a consequence of trace element accumulation.