The calcimimetic R-568 prevents podocyte loss in uninephrectomized ApoE-/- mice.

Calcimimetics are indicated for secondary hyperparathyroidism in chronic kidney disease, and some data have suggested their protective role for progression of renal damage. We aimed to evaluate whether a calcimimetic can slow the progression of kidney damage in uninephrectomized apolipoprotein E (ApoE)-deficient (ApoE-/-) mice. To this end, we compared its effect with that of calcitriol. Male ApoE-/- mice (12 wk old) were randomized to undergo sham operation (sham) or unilateral nephrectomy (UNX) and subsequently received the calcimimetic R-568 (4 µg·kg⁻¹·day⁻¹), calcitriol (0.03 µg·kg⁻¹·day⁻¹), or vehicle intraperitoneally. Glomerular number and volume, damage indexes (glomerular, vascular, and interstitial), and glomerular (podocytes, mesangial, and endothelial) cell number and volume were assessed in perfused kidneys after a 12-wk treatment period. Lower numbers of podocytes per glomerulus were observed in the UNX + vehicle group compared with the sham group, and this was prevented in the UNX + R-568 group but not in the UNX + calcitriol group. In parallel, albuminuria was higher in the untreated UNX group compared with the sham group, and the increase was prevented in the UNX + R-568 group. Interstitial fibrosis was more prevalent in the vehicle-treated UNX group compared with the sham group, and this was prevented in the UNX group treated with R-568 and less effectively with calcitriol treatment. In all UNX groups, the weight of the residual kidney was significantly higher compared with all sham groups. No differences were observed in serum ionized calcium and systolic blood pressure between the groups. The calcimimetic R-568 prevented interstial fibrosis and podocyte loss after uninephrectomy in ApoE-/- mice. Minor renal dysfunction, lack of secondary hyperparathyroidism, and hypertension in this model support the hypothesis of direct effects of this compound on glomerular cells.

Effect of paricalcitol and calcitriol on aortic wall remodeling in uninephrectomized ApoE knockout mice.

Despite an only minor reduction in the glomerular filtration rate, uninephrectomy (UNX) markedly accelerates the rate of growth of atherosclerotic plaques in ApoE-/- mice. It has been suggested that vitamin D receptor (VDR) activation exerts an antiproliferative effect on vascular smooth muscle cells, but the side effects may limit its use. To assess a potentially different spectrum of actions, we compared the effects of paricalcitol and calcitriol on remodeling and calcification of the aortic wall in sham-operated and UNX ApoE-/- mice on a diet with normal cholesterol content. Sham-operated and UNX mice were randomly allotted to treatment with solvent, calcitriol (0.03 µg/kg) or paricalcitol (0.1 µg/kg) 5 times/wk intraperitoneally for 10 wk. Semithin (0.6 µm) sections of the aorta were analyzed by 1) morphometry, 2) immunohistochemistry, and 3) Western blotting of key proteins involved in vascular calcification and growth. Compared with sham-operated animals (5.6 ± 0.24), the wall-to-lumen ratio (x100) of the aorta was significantly higher in solvent- and calcitriol-treated UNX animals (6.64 ± 0.27 and 7.17 ± 0.81, respectively, P < 0.05), but not in paricalcitol-treated UNX (6.1 5 ± 0.32). Similar differences were seen with respect to maximal plaque height. Expression of transforming growth factor (TGF)-ß1 in aortic intima/plaque was also significantly higher in UNX solvent and UNX calcitriol compared with sham-operated and UNX paricalcitol animals. Treatment with both paricalcitol and calcitriol caused significant elevation of VDR expression in the aorta. While at the dose employed paricalcitol significantly reduced TGF-ß expression in plaques, calcitriol in contrast caused significant vascular calcification and elevated expression of related proteins (BMP2, RANKL, and Runx2).

Oxidative stress after uninephrectomy alters heart morphology in the apolipoprotein E -/- mouse.

OBJECTIVE: Even minor reduction in glomerular filtration rate accelerates atherogenesis and increases cardiovascular risk. The current study on the apolipoprotein E -/- mouse was designed to investigate whether nephron reduction by uninephrectomy causes cardiac remodeling and whether this is prevented by antioxidative treatment. METHODS: We randomized apolipoprotein E -/- mice to undergo uninephrectomy or sham operation and subsequent treatment with either Tempol, Ebselen, Trandolapril, or a combination of Tempol and Trandolapril. After 12 weeks, the experiment was terminated by perfusion fixation under anesthesia. The myocardium was analyzed by morphometry. Additionally, the expression of endothelial nitric oxide synthase, transforming growth factor-beta1, vascular endothelial growth factor, flt-1, collagen I and presence of nitrotyrosine were assessed using immunohistochemistry or western blotting. RESULTS: Untreated uninephrectomized animals had lower capillary length density and higher volume fraction of interstitial tissue in the myocardium and bigger plaques in aorta compared with those who underwent sham operation. These changes did not develop in uninephrectomized animals treated with Tempol, Ebselen, Trandolapril, or Tempol + Trandolapril. In untreated uninephrectomized mice, the presence of nitrotyrosine and the expression of transforming growth factor-beta1, vascular endothelial growth factor, and collagen I were more marked. This was ameliorated by Tempol, Ebselen, Trandolapril, and Tempol + Trandolapril. CONCLUSION: We conclude that in the apolipoprotein E -/- mouse, even minor reduction in renal function, for example, by uninephrectomy, causes remodeling of the heart. This was ameliorated to a similar extent by antioxidants and angiotensin-converting enzyme inhibition.

Cinacalcet does not affect longitudinal growth but increases body weight gain in experimental uraemia.

BACKGROUND: Cinacalcet (CIN) efficiently suppresses parathyroid hormone (PTH) secretion by the activation of the calcium-sensing receptor (CaR). Epiphyseal chondrocytes also express the CaR and its activation promotes cell proliferation and differentiation in vitro. Hence, the impact of CIN on the growth plate function requires assessment before routine administration in children. METHODS: We treated subtotally nephrectomized (SNX) and sham-operated, ad lib and pair-fed Sprague-Dawley rats with CIN (15 mg/kg day) or solvent (S) for 14 days p.o. and assessed whole body and tibia length gain, growth plate morphology, osseous front advance (OFA) (calcein staining) and chondrocyte proliferation rate [5-bromo-2'-deoxyuridine (BrdU) staining]. RESULTS: Total body length gain did not differ after 7 and 14 days (SNX + CIN 2.9 +/- 0.6, SNX + S 3.0 +/- 0.7; sham + CIN 4.2 +/- 0.4, sham + S 4.5 +/- 0.4; sham pair-fed + CIN 3.3 +/- 0.5, sham pair-fed + S 3.5 +/- 0.6 cm/14 days; P = n.s.). Tibia length, the height of the total growth plate and the hypertrophic zone, OFA and chondrocyte proliferation rate were similar with CIN and S. Serum Ca(2+) declined with CIN treatment; PTH was 61% lower in CIN- compared to S-treated SNX (P < 0.05). Food intake was similar, whereas body weight gain (21.6 +/- 8.7 versus 12.7 +/- 11.2 g) and body weight gain per food intake (141 +/- 50 versus 77 +/- 70 g/kg) improved in CIN- versus S-treated SNX animals (P < 0.05). CONCLUSION: CIN treatment does not impact on growth plate chondrocyte function in uraemic rats, but improves food efficiency and body weight gain.

Regression of glomerulosclerosis in subtotally nephrectomized rats: effects of monotherapy with losartan, spironolactone, and their combination.

Angiotensin II accelerates and renin-angiotensin system blockade halts progression; blockade with high doses even reverses established glomerulosclerosis. Aldosterone also accelerates progression of glomerulosclerosis, partially independently of angiotensin II. The purpose of this study was to assess the relative ability of an angiotensin receptor type 1 (AT1) blocker, a mineralocorticoid receptor blocker, and their combination to reverse glomerulosclerosis. Sprague-Dawley rats were subjected to subtotal renal ablation (SNX) or sham operation. Eight weeks after surgery, they were either euthanized or allocated to treatment with vehicle, losartan, spironolactone, their combination, or unspecific antihypertensive treatment (dihydralazine) for 4 wk. Renal morphology was evaluated by stereology in tissues obtained using pressure-controlled perfusion fixation. Systolic blood pressure was significantly higher in SNX compared with sham-operated animals and decreased in all treatment groups. Compared with wk 8 after SNX, the glomerulosclerosis index (GSI) had increased further by week 12 in the vehicle- and dihydralazine-treated groups but was significantly lowered in the SNX+losartan as well as in the SNX+losartan+spironolactone groups and had not progressed further in the SNX+spironolactone group. The study confirms the partial regression of established glomerulosclerosis in subtotally nephrectomized rats after high-dose AT1 receptor blockade. Nonhyperkalemic doses of spironolactone prevented the increase but failed to decrease the GSI below the 8-wk level and preserved podocyte numbers. Combining the AT1 blocker with mineralocorticoid receptor blockade failed to further increase the regression of glomerulosclerosis.

Calcimimetic R-568 or calcitriol: equally beneficial on progression of renal damage in subtotally nephrectomized rats.

Patients with renal insufficiency develop secondary hyperparathyroidism. Monotherapy with active vitamin D or calcimimetics ameliorates secondary hyperparathyroidism. We compared kidney damage in subtotally nephrectomized (SNX) rats treated with active vitamin D (calcitriol) or the calcimimetic R-568. Male Sprague-Dawley SNX and sham-operated (sham-op) rats were randomized into the following treatment groups: SNX + R-568, SNX + calcitriol, SNX + vehicle, sham-op + R-568, sham-op + calcitriol, and sham-op + vehicle. Albuminuria and blood pressure were monitored and kidneys were examined using morphometry, immunohistochemistry, quantitative RT-PCR, and in situ hybridization. Parathyroid hormone concentrations were lowered to the same extent by the two interventions, although phosphorus and the calcium-phosphorus product were reduced only by R-568 treatment. SNX rats developed marked albuminuria, which was significantly reduced in ad libitum- and pair-fed animals treated with R-568 and animals treated with calcitriol. Mean glomerular volume (6.05 +/- 1.46 vs. 2.70 +/- 0.91 mm(3)), podocyte volume (831 +/- 127 vs. 397 +/- 67 microm(3)), the degree of foot process fusion (mean width of foot processes = 958 +/- 364 vs. 272 +/- 35 nm), and glomerular basement membrane thickness (244 +/- 6 vs. 267 +/- 23 nm), as well as desmin staining, were significantly higher in vehicle-treated SNX than sham-operated animals. These changes were ameliorated with R-568 and calcitriol. In SNX, as well as sham-operated, animals, expression of the calcium-sensing receptor (protein and mRNA) was upregulated by treatment with the calcimimetic, but not calcitriol. Calcitriol and R-568 were similarly effective in ameliorating kidney damage.

High expression level of bone degrading proteins as a possible inducer of osteolytic features in pigmented villonodular synovitis.

Protein expression of osteopontin (OPN), osteoprotegerin (OPG), bone sialoprotein (BSP), osteocalcin (OC), RANKL and PTHrP was determined by use of immunohistochemical analysis on tissue arrays (48 cases of PVNS, 20 cases of active (a-RA), non-active rheumatoid arthritis (na-RA), and osteoarthritis (OA)). Additionally, gene expression was analysed using complimentary DNA (cDNA) microarrays. All PVNS cases showed a higher level of both protein and gene expression of RANKL, OPN and BSP in comparison with OA cases. Expression of OPG was not significantly different in PVNS compared to OA. The RANKL/OPG expression ratio was significantly higher in PVNS than in OA. High expressions level of proteins involved in bone degradation in PVNS may promote an intra-osseous propagation of the lesion. This evidence suggests that PVNS might respond to treatment using specific inhibitors of RANKL, OPN and BSP.