Lanthanum suppresses osteoblastic differentiation via pertussis toxin-sensitive G protein signaling in rat vascular smooth muscle cells

Vascular calcification and cellular signaling pathways as potential therapeutic targets

Increased vascular calcification (VC) is observed in patients with cardiovascular diseases such as atherosclerosis, diabetes, and chronic kidney disease. VC is divided into three types according to its location: intimal, medial, and valvular. Various cellular signaling pathways are associated with VC, including the Wnt, mitogen-activated protein kinase, phosphatidylinositol-3 kinase/Akt, cyclic nucleotide-dependent protein kinase, protein kinase C, calcium/calmodulin-dependent kinase II, adenosine monophosphate-activated protein kinase/mammalian target of rapamycin, Ras homologous GTPase, apoptosis, Notch, and cytokine signaling pathways. In this review, we discuss the literature concerning the key cellular signaling pathways associated with VC and their role as potential therapeutic targets. Inhibitors to these pathways represent good candidates for use as potential therapeutic agents for the prevention and treatment of VC.

Histopathological study of JNK in venous wall of patients with chronic venous insufficiency related to osteogenesis process

Chronic venous insufficiency (CVI) is one of the most common vascular pathologies worldwide. One of the risk factors for the development of CVI is aging, which is why it is related to senile changes. The main trigger of the changes that occur in the venous walls in CVI is blood flow reflux, which produces increased hydrostatic pressure, leading to valve incompetence. The cellular response is one of the fundamental processes in vascular diseases, causing the activation of cell signalling pathways such as c-Jun N-terminal kinase (JNK). Metabolic changes and calcifications occur in vascular pathology as a result of pathophysiological processes. The aim of this study was to determine the expression of JNK in venous disease and its relationship with the role played by the molecules involved in the osteogenic processes in venous tissue calcification. This was a cross-sectional study that analyzed the greater saphenous vein wall in 110 patients with (R) and without venous reflux (NR), classified according to age. Histopathological techniques were used and protein expression was analysed using immunohistochemistry techniques for JNK and markers of osteogenesis (RUNX2, osteocalcin (OCN), osteopontin (OPN)). Significantly increased JNK, RUNX2, OCN, OPN and pigment epithelium-derived factor (PEDF) protein expression and the presence of osseous metaplasia and amorphous calcification were observed in younger patients (<50 years) with venous reflux. This study shows for the first time the existence of an osteogenesis process related to the expression of JNK in the venous wall.

Cortistatin inhibits arterial calcification in rats via GSK3β/β-catenin and protein kinase C signalling but not c-Jun N-terminal kinase signalling

AIM

Cortistatin (CST) is a newly discovered endogenous active peptide that exerts protective effects on the cardiovascular system. However, the relationship between CST and aortic calcification and the underlying mechanism remain obscure. Therefore, we investigated effects of CST on aortic calcification and its signalling pathways.

METHODS

Calcium content and alkaline phosphatase (ALP) activity were measured using the o-cresolphthalein colorimetric method and ALP assay kit respectively. Protein expression of smooth muscle (SM)-ɑ-actin, osteocalcin (OCN), β-catenin, glycogen synthase kinase 3β (GSK3β), p-GSK3β, protein kinase C (PKC), p-PKC, c-Jun N-terminal kinase (JNK) and p-JNK was determined using Western blotting.

RESULTS

In aorta from a rat vitamin D3 calcification model, CST abrogated calcium deposition and pathological damage, decreased the protein expression of OCN and β-catenin and increased SM-ɑ-actin expression. In a rat cultured vascular smooth muscular cell (VSMC) calcification model induced by β-glycerophosphate (β-GP), CST inhibited the increase in ALP activity, calcium content and OCN protein and the decrease in SM-α-actin expression. CST also inhibited the β-GP-induced increase in p-GSK3β and β-catenin protein (both P < .05). The inhibitory effects of CST on ALP activity, calcium deposition and β-catenin protein were abolished by pretreatment with lithium chloride, a GSK3β inhibitor. CST promoted the protein expression of p-PKC by 68.5% (P < .01), but not p-JNK. The ability of CST to attenuate β-GP-induced increase in ALP activity, calcium content and OCN expression in the VSMC model was abolished by pretreatment with the PKC inhibitor Go6976.

CONCLUSION

These results indicate that CST inhibits aortic calcification and osteogenic differentiation of VSMCs likely via the GSK3β/β-catenin and PKC signalling pathways, but not JNK signalling pathway.

Harnessing the bone-seeking ability of Ca(ii)-like metal ions in the treatment of metastatic cancer and resorption disorders

In this tutorial review, we explore how a special relationship between metal ions and bones has been exploited to target therapeutic agents.

Palmitic acid increases medial calcification by inducing oxidative stress

BACKGROUND

Aortic medial calcification is a cellular-regulated process leading to arterial stiffness. Although epidemiological studies have suggested an association between the saturation of fatty acids (FA) and arterial stiffness, there is no evidence that saturated FA can induce arterial calcification. This study investigated the capacity of palmitic acid (PA) to induce medial calcification and the signaling pathway(s) implicated in this process.

METHODS

Rat aortic segments and vascular smooth muscle cells (VSMC) were exposed to calcification medium supplemented with PA. In vivo, rats were treated with warfarin to induce calcification and fed a PA-enriched diet.

RESULTS

In vitro and ex vivo, palmitate increases calcification and ROS production. Palmitate increases extracellular-signal-regulated kinase (ERK1/2) phosphorylation and osteogenic gene expression. Inhibition of NADPH oxidase with apocynin or an siRNA prevents these effects. ERK1/2 inhibition attenuates the amplification of osteogenic gene expression and calcification induced by palmitate. In vivo, a PA-enriched diet amplified medial calcification and pulse wave velocity (PWV). These effects are mediated by ROS production as indicated by the inhibition of calcification and PWV normalization in rats concomitantly treated with apocynin.

CONCLUSION

ROS induction by palmitate leads to ERK1/2 phosphorylation and subsequently induces the osteogenic differentiation of VSMC. © 2013 S. Karger AG, Basel.

Lanthanum prevents high phosphate-induced vascular calcification by preserving vascular smooth muscle lineage markers

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.

The dual-effects of LaCl₃ on the proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells

A series of experimental methods including 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, alkaline phosphatase (ALP) activity measurement, alizarin red S stain and measurement, quantitative real-time reverse transcriptase polymerase chain reaction, and Western blot analysis were employed to assess the effects of LaCl₃ on the proliferation, osteogenic differentiation, and mineralization of a murine preosteoblast cell line MC3T3-E1 at cell and molecular levels. The results indicated that LaCl₃ had dual effects on the proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells. First, LaCl₃ promoted the proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells at lower concentrations, then had no effects and further turned to inhibit the proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells with increasing concentrations. The expression of runt-related transcription factor 2 (Runx2), bone morphogenetic protein 2 (BMP2), ALP, bone sialoprotein (BSP), collagen I (Col I), and osteocalcin (OCN) genes was upregulated in the presence of 0.0001 and 0.1 μM LaCl₃, but these genes were downregulated in the MC3T3-E1 cells treated with 1,000 μM LaCl₃. In addition, the expression of BMP2, Runx2, and OCN proteins was promoted by LaCl₃ at the concentration of 0.0001 μM, but these proteins were downregulated after 1,000 μM LaCl₃ treatment. The results suggest that LaCl₃ likely up- or downregulates the expression of Runx2, which subsequently up- or downregulates osteoblasts marker genes Col I and BMP2 at early stages and ALP and OCN at later stages of differentiation, thus causes to promote or inhibit the proliferation, osteogenic differentiation and mineralization of MC3T3-E1 cells. The results will be helpful for understanding the mechanisms of bone metabolism and application of lanthanum-based compounds in the future.

Ghrelin attenuates the osteoblastic differentiation of vascular smooth muscle cells through the ERK pathway

Vascular calcification results from osteoblastic differentiation of vascular smooth muscle cells (VSMCs) and is a major risk factor for cardiovascular events. Ghrelin is a newly discovered bioactive peptide that acts as a natural endogenous ligand of the growth hormone secretagog receptor (GHSR). Several studies have identified the protective effects of ghrelin on the cardiovascular system, however research on the effects and mechanisms of ghrelin on vascular calcification is still quite rare. In this study, we determined the effect of ghrelin on osteoblastic differentiation of VSMCs and investigated the mechanism involved using the two universally accepted calcifying models of calcifying vascular smooth muscle cells (CVSMCs) and beta-glycerophosphate (beta-GP)-induced VSMCs. Our data demonstrated that ghrelin inhibits osteoblastic differentiation and mineralization of VSMCs due to decreased alkaline phosphatase (ALP) activity, Runx2 expression, bone morphogenetic protein-2 (BMP-2) expression and calcium content. Further study demonstrated that ghrelin exerted this suppression effect via an extracellular signal-related kinase (ERK)-dependent pathway and that the suppression effect of ghrelin was time dependent and dose dependent. Furthermore, inhibition of the growth hormone secretagog receptor (GHSR), the ghrelin receptor, by siRNA significantly reversed the activation of ERK by ghrelin. In conclusion, our study suggests that ghrelin may inhibit osteoblastic differentiation of VSMCs through the GHSR/ERK pathway.

The combination of lanthanum chloride and the calcimimetic calindol delays the progression of vascular smooth muscle cells calcification

Phosphate (Pi)-binders are commonly used in dialysis patients to control high Pi levels, that associated with vascular calcification (VC). The aim of this study was to investigate the effects of lanthanum chloride (LaCl(3)) on the progression of high Pi-induced VC, in rat vascular smooth muscle cells (VSMCs). Pi-induced Ca deposition was inhibited by LaCl(3), with a maximal effect at 100μM (59.0±2.5% inhibition). Furthermore, we studied the effects on VC of calcium sensing receptor (CaSR) agonists. Gadolinium chloride, neomycin, spermine, and the calcimimetic calindol significantly inhibited Pi-induced VC (55.9±2.2%, 37.3±4.7%, 30.2±5.7%, and 63.8±5.7%, respectively). To investigate the hypothesis that LaCl(3) reduces the progression of VC by interacting with the CaSR, we performed a concentration-response curve of LaCl(3) in presence of a sub-effective concentration of calindol (10nM). Interestingly, this curve was shifted to the left (IC(50) 9.6±2.6μM), compared to the curve in the presence of LaCl(3) alone (IC(50) 19.0±4.8μM). In conclusion, we demonstrated that lanthanum chloride effectively reduces the progression of high phosphate-induced vascular calcification. In addition, LaCl(3) cooperates with the calcimimetic calindol in decreasing Ca deposition in this in vitro model. These results suggest the potential role of lanthanum in the treatment of VC induced by high Pi.

Apelin attenuates the osteoblastic differentiation of vascular smooth muscle cells

Vascular calcification, which results from a process osteoblastic differentiation of vascular smooth muscle cells (VSMCs), is a major risk factor for cardiovascular morbidity and mortality. Apelin is a recently discovered peptide that is the endogenous ligand for the orphan G-protein-coupled receptor, APJ. Several studies have identified the protective effects of apelin on the cardiovascular system. However, the effects and mechanisms of apelin on the osteoblastic differentiation of VSMCs have not been elucidated. Using a culture of calcifying vascular smooth muscle cells (CVMSCs) as a model for the study of vascular calcification, the relationship between apelin and the osteoblastic differentiation of VSMCs and the signal pathway involved were investigated. Alkaline phosphatase (ALP) activity and osteocalcin secretion were examined in CVSMCs. The involved signal pathway was studied using the extracellular signal-regulated kinase (ERK) inhibitor, PD98059, the phosphatidylinositol 3-kinase (PI3-K) inhibitor, LY294002, and APJ siRNA. The results showed that apelin inhibited ALP activity, osteocalcin secretion, and the formation of mineralized nodules. APJ protein was detected in CVSMCs, and apelin activated ERK and AKT (a downstream effector of PI3-K). Suppression of APJ with siRNA abolished the apelin-induced activation of ERK and Akt. Furthermore, inhibition of APJ expression, and the activation of ERK or PI3-K, reversed the effects of apelin on ALP activity. These results showed that apelin inhibited the osteoblastic differentiation of CVSMCs through the APJ/ERK and APJ/PI3-K/AKT signaling pathway. Apelin appears to play a protective role against arterial calcification.

Lanthanum carbonate versus sevelamer hydrochloride: improvement of metabolic acidosis and hyperkalemia in hemodialysis patients

Sevelamer hydrochloride (SH) has been reported to aggravate metabolic acidosis and hyperkalemia. This study was performed to evaluate acid-base status and serum potassium changes after replacing SH with lanthanum carbonate (LC) in hemodialysis patients. SH was prescribed for 24 weeks in 14 stable hemodialysis patients and replaced by LC in a similar treatment schedule. Laboratory tests, including indices of acid-base status, nutrition, bone/mineral metabolism, and dialysis adequacy, were performed monthly during the study. Dialysate bicarbonate, potassium and calcium concentrations remained constant. Serum bicarbonate and pH rose, and serum potassium dropped significantly under LC. Alkaline phosphatase also decreased significantly under LC. No significant differences were observed in the other studied parameters between the two treatment periods. Control of serum phosphate was similar under both phosphate-binders and no differences were observed in calcium, Ca × P product, CRP, or lipid levels. Dialysis adequacy was constantly kept within K/DOQI target-range. Although full compliance to treatment was reported, three patients on LC complained of gastrointestinal upset and/or a metallic taste, and four had difficulty chewing the LC tablet. LC improves metabolic acidosis and hyperkalemia in hemodialysis patients previously under SH. Although both medications are well-tolerated, the gastrointestinal side-effects appear to occur more frequently with LC; a fact that, together with difficulties in chewing the tablet, may result in decreased compliance.