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Aims Vascular calcification (VC) contributes to morbidity and mortality in patients with chronic kidney disease (CKD). Allosteric modulators of the calcium (Ca)-sensing receptor (CaSR) may slow the progression of VC in CKD patients either by reducing serum parathyroid hormone (PTH), Ca, and phosphate levels or by a direct effect on the vessel wall. The aim of this study was to examine the effects of calcimimetics on CaSR expression, cell phenotype, and mineral deposition in human vascular smooth muscle cells (h-VSMCs). Methods and results Primary h-VSMCs were exposed for 14 days to increasing concentrations of Ca2+ (from 1.8 to 5 mmol/L) in the presence or absence of calcimimetics R-568 or AMG 641 (0.1 μmol/L). Mineralization was detected by Alizarin red staining, and the cell phenotype was assessed using immunocytochemistry and qRT–PCR. CaSR expression was evaluated using flow cytometry. Short- and long-term exposure (1 day to 14 days) of h-VSMCs to calcimimetics promoted CaSR protein transport from the endoplasmic reticulum to the plasma membrane with enhanced CaSR expression on the cell surface, together with an increase in total cell CaSR expression due to enhanced biosynthesis. In pro-mineralizing conditions, exposure to calcimimetics counteracted the Ca2+-dependent reduction of CaSR expression, decreased matrix collagen secretion, and mineral deposition by ∼90%. These effects involved CaSR activation since it could be inhibited by CaSR siRNA, but not scrambled siRNA. Conclusions The calcimimetic-dependent increase in biosynthesis and activation of the CaSR in h-VSMCs probably play a key role in the protection against calcium-induced VC.

Expression of the calcium-sensing receptor (CaSR) has previously been demonstrated in human circulating monocytes (HCM). The present study was designed to measure CaSR expression in HCM and to examine its potential modulation by pro-inflammatory cytokines, Ca2+, vitamin D sterols in U937 cell line. Twenty healthy volunteers underwent blood sampling with subsequent isolation of peripheral blood mononuclear cells (PBMC) at 3 visits. Flow cytometry analysis (FACS) was performed initially (V1) and 19 days later (V2) to examine intra- and intersubject fluctuations of total and surface CaSR expression in HCM and 15 weeks later (V3) to study the effect of vitamin D supplementation. In vitro experiments were conducted to assess the effects of pro-inflammatory cytokines, calcidiol, calcitriol and Ca2+ on CaSR expression in U937 cell line. By FACS analysis, more than 95% of HCM exhibited cell surface CaSR staining. In contrast, CaSR staining failed to detect surface CaSR expression in other PBMC. After cell permeabilization, total CaSR expression was observed in more than 95% of all types of PBMC. Both total and surface CaSR expression in HCM showed a high degree of intra-assay reproducibility (

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are specific constituents of mature skeletal collagens excreted in urine. Their measurement represents a sensitive index of bone resorption. In this study, we have measured urinary excretion of pyridinolines crosslinks by immunoassay (ELISA) and HPLC methods in 80 patients with different bone resorption rates. We chose a sample of 44 healthy adults (30 men and 14 women) and a sample of 36 elderly patients (7 men and 29 women) presenting a secondary hyperparathyroidism due to a vitamin D deficiency. The correlation between HPLC (x) and ELISA (y) was judged satisfactory (y = 0.794x + 6.947, r = 0.92). The sensitivity of pyridinolines estimation was 50 nmol/l for immunoassay and 20 nmol/l for HPLC. The intra-assay and inter-assay coefficients of variation for the two analytical methods was10%. The mean excretion of crosslinks (nmol/mmol of creatinine) measured by both methods in the sample of healthy adults was higher in women than in men. The amount of pyridinolines crosslinks excreted by elderly patients with vitamin D deficiency are three time higher than those of normal adults when measured by ELISA and HPLC methods. The distribution of different molecular forms of urinary pyridinoline crosslinks was investigated. Values of pyridinolines measured by HPLC in our samples of elderly patients have shown that free and peptide-bound pyridinolines with molecular weight (mol. wt.) smaller than 1000 Da represent approximately 80% of the total pyridinolines contained in urinary samples. A study on the evaluation of the antiserum used in the immunoassay for reacting with the different molecular forms isolated from urine showed a high affinity for free and peptide-bound pyridinolines with molecular weight smaller than 10,000 Da and that do not react strongly with peptide-bound with molecular weight greater than 10,000 Da. We conclude that, although this immunoassay does not measure total pyridinolines and does not distinguish between HP and LP, it seems convenient for diagnostic of metabolic bone diseases.

Uremic syndrome is attributed to the progressive retention of a large number of compounds, such as indoxyl sulfate, which under physiological conditions are excreted by the kidneys. Previous in vitro studies have demonstrated that uremic indoxyl sulfate concentrations induce a weak increase in the proliferation of both rat and human vascular aortic smooth muscle cells (hVASMC) after short term exposition to the toxin (i.e. 24 h). In the present study, we evaluated indoxyl sulfate effects on the proliferation of hVASMC at three different concentrations after long-term exposure (seven days). In contrast to previously published studies, we observed a dose-dependent and significant inhibitory effect of this toxin on hVASMC proliferation. We also demonstrated that indoxyl sulfate inhibits epidermal growth factor-induced hVASMC proliferation after long-term exposure. Indoxyl sulfate effects were associated with a dose-dependent induction of intracellular reactive oxygen species and up-regulation of p21 and p27 protein expression. Chronic exposure to indoxyl sulfate produces a significant inhibitory effect on hVASMC proliferation. The relevance of these findings must be evaluated by further studies, particularly in an in vivo setting.

Vascular calcification is frequent in patients with chronic kidney disease. Osteoprotegerin (OPG, a soluble factor which blocks osteoclast differentiation) has recently been implicated in the genesis of vascular calcification. Given that OPG can bind the pro-apoptotic tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), we hypothesized that the TRAIL protein is involved in the formation of vascular calcification both in vitro and in vivo. Using an immunohistochemical approach, we evaluated TRAIL and OPG expression on aortic valves slides from non-uremic and uremic wild type and apolipoprotein knockout (Apo E(-/-) ) mice. We also tested the in vitro effects of TRAIL on cultured primary human vascular smooth muscle cells (hVSMC). We further assayed serum soluble TRAIL (sTRAIL) levels in hemodialysis patients and correlated them with vascular calcification scores. Our results demonstrated that: (i) TRAIL and OPG were expressed inside the atheroma plaque in non-uremic ApoE(-/-) mice, but not in wild type mice; and (ii) uremia enhanced the expression levels. TRAIL enhanced the phosphate-induced mineralization of hVSMCs in a dose-dependent manner. In clinical terms, we demonstrated that sTRAIL is depressed in the sera of hemodialysis patients, but was not correlated with vascular calcification. Our results suggest that TRAIL may be involved in the formation of vascular calcification in certain experimental settings; however, its role in chronic kidney disease patients requires further evaluation.

Osteoporosis is a major public health problem for adults above 55 years of age, which leads to an increase in bone fragility. Last decade has witnessed remarkable advances in molecular biology and genetics that led to detailed understanding of the bone remodeling cycle and new therapeutic targets for its treatment have emerged. Thus, besides classical approach (vitamin D and calcium administration, bisphosphonates, oestrogen, raloxifene), new therapeutic agents such as parathyroid hormone (PTH) compounds, anti-RANKL antibodies and strontium ranelate are or will be increasingly used in the treatment of osteoporosis. In this review, we have presented the importance and therapeutic potential of strontium ranelate as a dual agent in the current treatment of osteoporosis.

Strontium ranelate exerts both an anticatabolic and an anabolic effect on bone cells. To further investigate the mechanism by which strontium ranelate inhibits bone resorption, the effects of varying concentrations of Sr(o)(2+) on osteoclastic differentiation were studied using RAW 264.7 cells and peripheral blood monocytic cells (PBMCs). We report that increasing concentrations of Sr(o)(2+) down-regulate osteoclastic differentiation and tartrate-resistant acid phosphatase activity, leading to inhibition of bone resorption (-48% when PBMCs were cultured for 14 days in the presence of 2 mM Sr(o)(2+)). Using a dominant-negative form of the calcium-sensing receptor (CaR) and a small interfering RNA approach, we provide evidences that the inhibition of osteoclast differentiation by Sr(o)(2+) is mediated by stimulation of the CaR. Moreover, our results suggest that the effects of Sr(o)(2+) on osteoclasts are, at least in part, mediated by inhibition of the receptor activator of nuclear factor-κB ligand (RANKL)-induced nuclear translocation of nuclear factor-κB and activator protein-1 in the early stages of osteoclastic differentiation. In conclusion, our data indicate that Sr(2+) directly inhibits the formation of mature osteoclasts through down-regulation of RANKL-induced osteoclast differentiation and decreases osteoclast differentiation through the activation of the CaR.

Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are intermolecular cross-linking amino acids of collagen and their urinary excretion reflects bone resorption. An isocratic high-performance liquid chromatographic assay using a reversed-phase column with a prefractionation step and fluorescence detection was developed. The accuracy and reproducibility were assessed by loading experiments and by double analysis of urinary samples. The recoveries after various loads were above 90% for HP and between 87 and 94% for LP, with an intra-assay relative standard deviation (R.S.D.) of 5% for HP and 8% for LP. The inter-assay R.S.D.s were 8% for HP and 12.4% for LP. The fasting and 24-h urinary excretions of HP and LP were measured in 40 healthy subjects (mean age 35 years) of both sexes. There was no difference between males and females. Mean adult normal values were 33.6 +/- 8.1 pmol/mumol creatinine for HP and 7.0 +/- 2.5 pmol/mumol creatinine for LP in morning fasting urine and 2-.9 +/- 7.0 pmol/mumol creatinine for HP and 5.8 +/- 1.9 pmol/mumol creatinine for LP after 24-h urinary collection. HP and LP excretions were significantly higher in morning fasting urine than in 24-h collections, in agreement with the physiological circadian rythm of bone resorption. This simplified and optimized procedure is a good method for the determination of pyridinolines and should be useful for the evaluation of bone resorption.

The calcium-sensing receptor (CaR) belongs to the G protein-coupled receptor superfamily, with a characteristic structure consisting of seven transmembrane helices, an intracellular C-terminal and an extracellular N terminal domain. The primary physiological function of the CaR is the maintenance of constant blood Ca2+ levels, as a result of its ability to sense very small changes in extracellular Ca2+ (Ca2+(o)). Nevertheless, in addition to being expressed in tissues involved in Ca2+(o) homeostasis, the CaR is also expressed in tissues not involved in mineral homeostasis, suggestive of additional physiological functions. Numerous agonists and modulators of the CaR are now known in addition to Ca2+(o), including various divalent and trivalent cations, aromatic l-amino acids, polyamines, and aminoglycoside antibiotics. The signaling of the CaR is also regulated by extracellular pH and ionic strength. The activated CaR couples mainly to the phospholipase Cbeta and extracellular signal-regulated kinase 1/2 signaling pathways, and it decreases intracellular cAMP levels, leading to various physiological effects. The recent identification of synthetic allosteric modulators of the CaR has opened up a new field of research possibilities. Calcimimetics and calcilytics, which increase and decrease agonist signaling via the CaR, respectively, may facilitate the manipulation of the CaR and thus aid in further investigations of its precise signaling. These allosteric modulators, as well as strontium, have been demonstrated to have therapeutic potential for the treatment of disorders involving the CaR. This review discusses the various agonists and modulators of the CaR, differences in their binding and signaling, and their roles as therapeutics in various diseases.

International audience; In this study, we showed that oligogalacturonic acid (OGA) purified from flax pectin inhibit osteoclastic bone resorption in a dose-dependent manner. The OGA inhibitory effect was neither linked to an effect on osteoclast apoptosis, nor to an inhibition of cathepsin K activity. By means of an collagen degradation assay we demonstrated that OGA prevented triple helical type I collagen cleavage by cathepsin K in a dose and chain length dependent manner. This inhibition was not restricted to cathepsin K, since collagenolytic activity of other lysosomal cysteine proteases, such as cathepsin B and cathepsin L, as well as matrixmetalloproteinases such as MMP-9 were also inhibited. Interestingly, using non-collagen substrates we demonstrated that OGA does not inhibit the proteolytic activity of cathepsin B and L, suggesting that OGA inhibits collagen degradation without affecting the lysosomal cysteine enzyme proteolytic activity. Finally, preliminary study using Surface Plasmon Resonance (SPR) showed that OGA binds to type I collagen but not to albumin, consistent with a specific effect on collagen. These results suggest that the observed inhibition of collagen degradation by OGA may be due to its ability to bind to the collagen molecule. By masking the collagen surface, OGA may render the collagen cleavage site less accessible to enzymes and thus prevent its enzymatic degradation.

International audience; The calcium-sensing receptor (CaR), is a G protein-dependent receptor that responds to increments in extracellular Ca(2+) ([Ca(2+)](o)). We previously reported that an increase in [Ca(2+)](o) induced a release of intracellular calcium and Ca(2+) entry via store operated channels (SOCs). We also demonstrated that MCF-7 cells express Transient Receptor Potential canonical 1 (TRPC1) channels. Herein, we investigated CaR intracellular signaling pathways and examined the role of TRPC1 in CaR-induced cell proliferation, through the extracellular signal-regulated Kinases 1 & 2 (ERK1/2) pathways. Treatment by [Ca(2+)](o) increased both MCF-7 cell proliferation and TRPC1 expression. Both the [Ca(2+)](o) proliferative effect and TRPC1 protein levels were abolished by the ERK1/2 inhibitors. Moreover, [Ca(2+)](o) failed to increase cell proliferation either in the presence of CaR or TRPC1 siRNAs. Both [Ca(2+)](o) and the selective CaR activator spermine, elicited time and dose-dependent ERK1/2 phosphorylation. ERK1/2 phosphorylation was almost completely inhibited by treatment with the phospholipase C and the protein kinase C inhibitors. Treatment with 2-aminoethoxydiphenyl borate (2-APB), and SKF-96365 or by siTRPC1 diminished both [Ca(2+)](o)- and spermine-stimulated ERK1/2 phosphorylation. Moreover, down-regulation of TRPC1 by siRNA reduced the Ca(2+) entry induced by CaR activation. We conclude that the CaR activates ERK1/2 via a PLC/PKC-dependent pathway. Moreover, TRPC1 is required for the ERK1/2 phosphorylation, Ca(2+) entry and the CaR-proliferative effect.

International audience; This study evaluates the effect of the mother-of-pearl (nacre) organic matrix on mammalian osteoclast activity and on cathepsin K protease. Rabbit osteoclasts were cultured on bovine cortical bone slices in the presence of water-soluble molecules extracted from nacre of the pearl oyster Pinctada margaritifera. Osteoclast resorption activity was determined by quantification of the resorption surface area on bovine bone slices. Papain and cathepsin K, B and L inhibition tests were performed in the presence of the nacre water-soluble extracts. The active crude extract was fractionated by dialysis and reversed-phase high-performance liquid chromatography before electrospray mass spectrometry analysis of inhibitory fractions. The water-soluble molecules extracted from nacre decreased bone resorption without jeopardizing osteoclast survival. The hydrolytic activity of cysteine proteinases was reduced when the enzymes were incubated with the nacre water-soluble molecules. Trending towards characterization of the molecules involved, it appears that cathepsin K inhibitors remain in different nacre water-soluble organic matrix subfractions, composed of low molecular weight molecules. Mollusk shell nacre contains molecules capable of reducing osteoclast bone resorption activity by inhibiting cathepsin K, giving a new facet of the bioactivity of nacre as bone biomaterial.

International audience; Osteoclast activity was studied on nacre, the mother of pearl (MOP) in order to assess the plasticity of bone resorbing cells and their capacity to adapt to a biomineralized material with a different organic and mineral composition from that of its natural substrate, bone. Pure MOP, a natural biomineralized CaCO(3) material, was obtained from Pinctada oyster shell. When implanted in the living system, nacre has proven to be a sustainable bone grafting material although a limited surface degradation process. Osteoclast stem cells and mature osteoclasts were cultured on MOP substrate and osteoclast precursor cells were shown to differentiate into osteoclasts capable of resorbing nacre substrate. However, analysis of the organization of the cytoskeleton showed that both a sealing zone and a podosome structure were observed on the nacre substrate. Moreover, MOP resorption efficiency was consistently found to be lower than that of bone and appeared to be a limited process.

The Nador lagoon is the largest one in Morocco and along the Mediterranean. It is located on the northeastern coast near the Rif chain (North Morocco), and it is surrounded by volcanic and sedimentary rocks of various lithofacies. The watershed has an area of about 2200 km2 and is drained by a dense river network. The lagoon dimension is of 115 km2 (25 x 7.5 km) with a depth not exceeding 8 m. The island barrier is 25 km in length and 350 m in average width. The carbonate fraction is the dominant component of the present-day sedimentation in the Nador lagoon. It represents 13 to 48 % of total sediments. Its distribution within the lagoon reflects the nature of marine and continental watershed. The carbonate fraction is composed, in decreasing order of importance, of calcite, magnesium calcite, dolomite and aragonite. The Sr isotopic signatures of lagoonal carbonates sediments show that they are dominated by marine biogenic sediments deposited, and by chemical precipitation. In addition, other carbonates of external origin and less radiogenic Sr isotopic are also present, coming from aerosols and ancient carbonates and transported by streams and rivers. From northwest to southeast, the Sr concentration of these lagoon carbonates increases, showing a slow renewal of waters in the southeastern zone because of its remoteness from communication with sea.

Flavonoids are micronutrients widely present in food of plant origin. They have been attributed pharmacological properties such as anticancer and prevention of age-related pathologies. It has been recently hypothesized that flavonoids increase bone mass and prevent osteoporosis. However, little is known about the in vitro effects of flavonoids on osteoclast activities. We investigated the effects of quercetin, one of the most commonly occurring flavonoids, on osteoclast differentiation which is a critical determinant step of in vivo bone resorption. Two in vitro models of osteoclast differentiation were used in this study: a murine one, involving the culture of RAW 264.7 cells in presence of receptor activator of NF kappa B ligand (RANKL), and a human model consisting of differentiating peripheral blood monocytic cells (PBMC) isolated from peripheral blood in presence of RANKL and macrophage-colony stimulating factor (M-CSF). Osteoclastogenesis was assessed by osteoclast-like number, tartrate resistant acid phosphatase (TRAP) activity, and bone resorbing activity. We showed that quercetin (0.1-10 microM) decreased osteoclastogenesis in a dose dependent manner in both models with significant effects observed at low concentrations, from 1 to 5 microM. The IC(50) value was about 1 microM. Analysis of protein-DNA interaction by electrophoretic mobility shift assay (EMSA) performed on RAW cells showed that a pre-treatment with quercetin inhibited RANKL-induced nuclear factor kB (NF kappa B) and activator protein 1 (AP-1) activation. NF kappa B and AP-1 are transcription factors highly involved in osteoclastic differentiation and their inhibition could play an important role in the decrease of osteoclastogenesis observed in the presence of quercetin. In conclusion, the present results demonstrate for the first time that quercetin, a flavonoid characterized by antioxidant activities, is a potent inhibitor of in vitro osteoclastic differentiation, via a mechanism involving NF kappa B and AP-1.

Cancer cells metastasized to bone stimulate osteoclastogenesis resulting in bone destruction. However, the influence of tumor cells on fully differentiated osteoclasts is much less known. We postulated that breast cancer cells directly stimulate the survival of mature osteoclasts. We thus tested the effect of conditioned media (CM) prepared from MDA-MB-231 cells on the activity and apoptosis of osteoclasts isolated from 10-day-old rabbit long bones. First, we demonstrated that CM increased the bone resorbing activity in our cell model of rabbit mature osteoclasts. Using a highly purified osteoclast cell population, we found that MDA-MB-231 CM dramatically inhibited osteoclast apoptosis. In the presence of 20% CM, apoptosis was decreased by approximately 60%. LY294002, a PI3 kinase inhibitor, strongly prevented the CM anti-apoptotic effect. Neutralizing experiments with human antibody revealed that macrophage-colony stimulating factor originating from MDA-MB 231 cells was possibly involved in the CM anti-apoptotic effect. These results suggest that breast cancer cells, in addition to stimulating osteoclastogenesis, potently inhibit mature osteoclast apoptosis, a mechanism which may greatly contribute to their osteolytic potential.

Many plant-derived substances have estrogenic activities. Due to their ability to bind the estrogen receptor (ER), these compounds have the potential to counteract the deleterious effects of estrogen deficiency on bone. In this study, we investigated the in vitro effect of two widespread flavonols, quercetin and kaempferol, on alkaline phosphatase (ALP) activity in MG-63 cultured human osteoblasts. We found that both flavonols significantly increased ALP activity. This effect was markedly reduced by PD 98059, an inhibitor of the extracellular regulated kinase (ERK) pathway, and by ICI 182780, an antagonist of ERs. Western blot studies confirmed that ERK is rapidly activated in cells treated by both flavonols. Finally, ICI 182780 markedly inhibits the flavonol-induced ERK activation. The data presented in this study support the conclusion that, in MG-63 osteoblasts (i) the increase in ALP activity by flavonols involves a rapid stimulation of ERK activation but also involves the ER, and that (ii) the activation of ERK by flavonols occurs most likely downstream of the ERs activation. Taken together, these results suggest that flavonols derivatives as quercetin and kaempferol can stimulate osteoblastic activity. Such compounds may represent new pharmacological tools for the treatment of osteoporosis.

Several recent studies have suggested that flavonols, a class of phytochemicals with many biological activities, might exert a protective effect against post-menopausal bone loss. In the present study, we investigated the effects of quercetin and kaempferol, two of the major naturally occurring flavonols on the in vitro bone resorbing activity of osteoclasts. Our results indicate that both compounds, at concentrations ranging from 0.1 to 100 microM reduce bone resorption in a time and dose-dependent manner. Significant inhibitory effects were observed at concentrations as low as 0.1 microM especially with kaempferol. The IC(50)s, or concentration inhibitory of 50% of basal resorption, calculated for quercetin and kaempferol were 1.6 and 5.3 microM, respectively. Using highly purified rabbit osteoclasts, we showed that both flavonols directly induce apoptosis of mature osteoclasts in the same dose-range effective for inhibiting bone resorption. When osteoclasts were treated with 50 microM of quercetin and kaempferol, intracellular reactive oxygen species levels decreased significantly by 75 and 25%, respectively, indicating these molecules keep their antioxidant properties at this concentration. However, at concentrations below 50 microM, neither quercetin nor kaempferol exerted antiradical action, suggesting that antioxidant properties cannot fully explain the inhibitory effect on bone resorption. Finally, we report that kaempferol-, but not the quercetin-induced inhibition of bone resorption was partially abolished by the presence of the pure anti-estrogen ICI 182780 suggesting that kaempferol's estrogenic effect could be involved in the inhibition of bone resorption. The present study demonstrates that flavonols widely distributed in human diet such as quercetin and kaempferol, exert a potent inhibitory effect on in vitro bone resorption.

Suspension cells of Nicotiana plumbaginifolia rapidly absorbed exogenously applied butyric acid and converted it into a new product within one day. The conversion product was found to be 6- O -butyryl- d -glucose. This molecule could be of great interest because of its capacity to transport and release butyric acid in vivo .

An HPLLC method for measuring total hydroxyproline in human urine was validated. Hydroxyproline derivatization was achieved with 9-fluorenylmethyl chloroformate after blocking primary amino acids with orthophthaldialdehyde. The derivatives (hydroxyproline and internal standard) were separated by reversed phase high-performance liquid chromatography and detected by absorbance at 254 nm. Duplicate measurements of hydroxyproline have a coefficient of variation of 3.9% and the recovery in spiked urine samples is between 99.5 and 100.8%. We have compared the HPLC procedure with a commercial colorimetric assay. Analytical criteria of these methods are identical. Regression analysis, involving 50 samples, shows an excellent correlation between hydroxyproline chromatographic ( y ) and colorimetric ( x ) procedures: y = 0.989 x + 2.99 ( r = 0.976). Hydroxyproline excretion was determined in urine samples from 76 women more than 5 years post-menopause. The mean hydroxyproline/creatinine ratio in this group was19.3 ± 5.6 μ mol/mmol (range 10.6–34.7). Finally, we compared in the same urinary samples hydroxyproline excretion with pyridinoline excretion (hydroxylysylpyridinoline and lysylpyridinoline), a new marker of bone resorption. The values show a significant correlation, with r = 0.417 for hydroxylysylpyridinoline and r = 0.443 for lysylpyridinoline.

Breast cancer is the most frequent form of cancer in women, with the highest incidence of metastasis to the bone. The reason for the preferential destination to the bone is believed to be due to chemoattractant factors released during bone resorption, which act on the cancer cells facilitating their metastasis. One of the factors released during osteolysis that may mediate breast cancer bone localization is Ca2+. Here, we show that extracellular Ca2+ (Ca2+(o)) acting via the calcium-sensing receptor (CaSR), greatly promotes the migration of bone-preferring breast cancer cells. In Boyden Chamber and Scratch Wound migration assays, an increase in breast cancer cell migration was observed at 2.5 mM and 5 mM Ca2+(o) compared to basal levels for three of the four breast cancer cell lines tested. However, a significantly greater migratory response was observed for the highly bone metastatic MDA-MB-231 cells, compared to the MCF7 and T47D, which have a lower metastatic potential in vivo. The BT474 cells, which do not metastasize to the bone, did not respond to elevated concentrations of Ca2+(o) in the migration assays. Inhibition of either ERK1/2 MAPK or phospholipase Cbeta (PLCbeta) led to an abolition of the Ca2+(o)-induced migration, implicating these pathways in the migratory response. Knockdown of the CaSR by siRNA resulted in an inhibition of the Ca2+(o)-induced migration, demonstrating the involvement of this receptor in the effect. These results suggest that the activation of the CaSR by elevated Ca2+(o) concentrations, such as those found near resorbing bone, produces an especially strong chemoattractant effect on bone metastatic breast cancer cells toward the Ca2+-rich environment.

Le cancer de la prostate (PCa) est une maladie des cellules de la prostate. Elle est caractérisée par une prolifération incontrôlée des cellules épithéliales de la glande prostatique, qui se multiplient de façon anarchique pour former une tumeur maligne. Pour traiter le PCa, la suppression androgénique (ADT), radiothérapie et la chimiothérapie sont les traitements de référence et sont prescrits depuis plusieurs années. Cependant, la maladie devient résistance à la castration après un certain temps. Face à d'évidents besoins en thérapies innovantes, le secteur pharmaceutique a montré́ un réel intérêt pour le développement de nouvelles hormonothérapies. Une nouvelle classe de hormonothérapies est disponible depuis 2011 : les hormonothérapies de deuxième génération telles que l'acétate d'abiratérone. Ces molécules ont révolutionné la prise en charge du PCa. En effet, elles ont amélioré la survie des patients et elles ont retardé la détérioration de la qualité de vie des malades mais aussi retarde l'utilisation de la thérapie cytotoxique. De ce fait, Comité de Cancérologie de l'Association Française d'Urologie (CCAFU) a mis à jour ses recommandations pour considérer que l'abiratérone en association avec l'ADT comme nouveau standard thérapeutique pour le traitement des cancers de la prostate métastatiques hormono et chimio-naïfs à haut risque nouvellement diagnostiqué.

Les glomérulonéphrites sont des pathologies rénales rares dont la physiopathologie complexe et ses répercussions à long terme sur la fonction rénale nécessitent un suivi rigoureux. De plus, on retrouve dans l’arsenal thérapeutique, les corticoïdes et autres molécules immunosuppressives qui sont contraignantes tant par leurs effets indésirables que leurs précautions d’emploi. Le but de ce travail était de réaliser des livrets d’accompagnement afin d’informer les patients sur leur maladie mais aussi sur les mesures à adopter pour supporter au mieux les traitements prescrits. L’utilisation des supports d’information écrits s’inscrit dans une pratique de la pharmacie au plus proche du parcours de soin du patient, optimise son accompagnement et l’observance de son traitement.

L’insuffisance rénale chronique induit de nombreux troubles du métabolisme minéral et osseux ainsi que des calcifications vasculaires impactant par conséquent le pronostic vital et fonctionnel. Une prise en charge exhaustive est donc essentielle pour augmenter l’espérance de vie et améliorer la qualité de vie des patients insuffisant rénaux. On distingue différentes atteintes osseuses définies par des lésions histologiques, ce sont les ostéodystrophies rénales. L’hyperparathyroïdie secondaire à l’insuffisance rénale chronique est associée à l’ostéite fibreuse, elle est caractérisée par une rétention de phosphate, une diminution de la synthèse rénale de calcitriol et une hypocalcémie. Le diagnostic des différentes atteintes osseuses s’appuie sur des examens biochimiques, radiologiques et dans certains cas sur une biopsie osseuse, examen de référence. Dans cette thèse, nous étudierons la physiopathologie de l’ostéodystrophie rénale, les traitements spécifiques de chaque atteinte ainsi que la prévention nutritionnelle. Aussi, nous verrons comment la prise en charge de l’acidose métabolique, du stress oxydatif alliée à une meilleure absorption de minéraux et vitamines peut potentiellement permettre de réduire l’incidence des atteintes osseuses.

L’hyperphosphatémie est l’un des plus importants facteurs de risque non-traditionnels liés à l’urémie qui est considéré comme facteur prédictif de la morbi-mortalité cardiovasculaire. À cet égard, différentes études épidémiologiques ont montré que des concentrations sériques élevées de phosphate étaient également associées aux maladies cardiovasculaires dans la population générale. Considérant les implications cliniques de l'hyperphosphatémie incontrôlée, les concentrations de phosphate doivent être maintenues dans une fourchette optimale malgré d'importantes fluctuations des apports en phosphate alimentaire. Ces considérations sont d’autant plus importantes puisque la teneur des aliments en phosphate est en augmentation, principalement en raison de la consommation accrue d'aliments transformés avec des additifs phosphatés. Les principales hormones et facteurs qui contribuent à la régulation rénale de phosphate comprennent l'hormone parathyroïdienne, le FGF23, klotho et la 1,25-dihydroxyvitamine D3 (1,25 (OH) 2D3). Il y a quatre principales stratégies pour contrôler la phosphatémie ; la restriction des apports alimentaires riches en phosphates, l'administration d'agents chélateurs de phosphate, le contrôle de l'hyperparathyroïdie et l’adéquation de la dialyse chez les patients en IRC avancée. Malgré toutes les stratégies disponibles, et l'introduction de nouvelles thérapeutiques sur le marché, le contrôle du phosphate sérique demeure difficile, et l'hyperphosphatémie continue d'être extrêmement fréquente chez les patients en IRC. Une meilleure compréhension des mécanismes d’altération du métabolisme du phosphate dans l’IRC peut aider à clarifier le rôle possible de l'excès de phosphate alimentaire comme facteur de risque dans la population générale.