Ligand-Dependent Effects of Methionine-8 Oxidation in Parathyroid Hormone Peptide Analogues.

LA-PTH is a long-acting parathyroid hormone (PTH) peptide analogue in preclinical development for hypoparathyroidism (HP). Like native PTH, LA-PTH contains a methionine at position 8 (Met8) that is predicted to be critical for function. We assessed the impact of Met oxidation on the functional properties of LA-PTH and control PTH ligands. Oxidation of PTH(1-34) resulted in marked (~20-fold) reductions in binding affinity on the PTH receptor-1 (PTHR1) in cell membranes, similarly diminished potency for 3',5'-cyclic AMP signaling in osteoblastic cell lines (SaOS-2 and UMR106), and impaired efficacy for raising blood calcium in mice. Surprisingly, oxidation of LA-PTH resulted in little or no change in these functional responses. The signaling potency of oxidized-LA-PTH was, however, reduced approximately 40-fold compared to LA-PTH in cells expressing a PTHR1 construct that lacks the N-terminal extracellular domain (ECD). Molecular modeling revealed that while Met8 of both LA-PTH and PTH(1-34) is situated within the orthosteric ligand-binding pocket of the receptor's transmembrane domain bundle (TMD), the Met8 sidechain position is shifted for the 2 ligands so that on Met8 oxidation of PTH(1-34), steric clashes occur that are not seen with oxidized LA-PTH. The findings suggest that LA-PTH and PTH(1-34) engage the receptor differently in the Met8-interaction environment of the TMD bundle, and that this interaction environment can be allosterically influenced by the ECD component of the ligand-receptor complex. The findings should be useful for the future development of novel PTH-based peptide therapeutics for diseases of bone and mineral ion metabolism.

No impact of anti-Rank ligand and PTH analogs on cardiovascular risk in postmenopausal osteoporosis: a systematic literature review and meta-analysis.

The mutual effects of drugs used in osteoporosis and cardiovascular diseases are a point of interest. A literature review and meta-analysis were conducted to address the impact of PTH analogs and anti-Rank ligand on cardiovascular events and overall mortality in individuals with idiopathic osteoporosis; these treatments do not appear to have any effect. INTRODUCTION: Two meta-analyses have been conducted to explore the cardiovascular effects of bisphosphonates. There is no review for other osteoporosis treatments. A literature review and meta-analysis were conducted to address the impact of PTH analogs and anti-Rank ligand on cardiovascular events and overall mortality in individuals with idiopathic osteoporosis. METHODS: A systematic review was conducted in December 2017 in the PubMed, Embase, and Cochrane databases and updated on PubMed in July 2019, selecting trials with a treatment and a control group. We also conducted a search for abstracts of the French Rheumatology Society, American College of Rheumatology, and European League Against Rheumatism's annual meetings over the past 4 years. The main endpoint was the occurrence of cardiovascular events; the secondary was mortality (all causes). RESULTS: Of the 2782 reports initially found, 16 articles were used for the meta-analysis (6 for the anti-Rank ligand and 10 for the PTH analog group). After meta-analysis, there was no significant difference between the placebo group and the anti-Rank ligand group for overall mortality (p = 0.13), the combined endpoint (overall mortality, coronary artery disease, and stroke; p 0.77), and the individual risk of coronary artery disease (p 0.53), arrhythmia (p 0.95), and stroke (p 0.62). After meta-analysis, there was no significant difference between the placebo group and the PTH analogs group for overall mortality (p 0.77), the combined endpoint (p = 0.95), and the individual risk of coronary artery disease (p = 0.74), arrhythmia (p = 0.28), and stroke (p = 0.61). CONCLUSIONS: The anti-Rank ligand and PTH analogs have no impact on cardiovascular risk and overall mortality in idiopathic osteoporosis. To better answer the question whether these treatments can reduce the long-term cardiovascular risk, further comparative studies with longer duration are required.

Novel therapies in osteoporosis: PTH-related peptide analogs and inhibitors of sclerostin.

Bone-forming approaches to treat patients with severe osteoporosis are effective, but treatment options are limited, and there is an unmet clinical need for additional drugs. This review discusses two novel and advanced anabolic therapeutic concepts that have successfully completed phase 3 trials. Romosozumab is a monoclonal antibody that targets the Wnt inhibitor sclerostin. Two phase 3 trials (FRAME and ARCH) of romosozumab for the treatment of postmenopausal osteoporosis have been completed. Both trials successfully reached their primary endpoint by reducing vertebral fractures by 75% compared to placebo (FRAME trial) and 48% compared to alendronate (ARCH trial), respectively. Abaloparatide is a PTH-related protein (PTHrP) analog that has displayed bone anabolic activity. In the phase 3 ACTIVE trial, abaloparatide was compared to placebo and teriparatide for 18 months in postmenopausal women who had already experienced an osteoporotic fracture. Abaloparatide successfully reduced the rate of new vertebral fractures by 86% compared to placebo. Furthermore, abaloparatide achieved greater BMD increases at all measured sites compared to both placebo and teriparatide. Based on these results, abaloparatide was FDA approved in April 2017. This review discusses available data of both agents with regard to efficacy and safety as well as their possible future application.

Parathyroid hormone(1-34) and its analogs differentially modulate osteoblastic Rankl expression via PKA/SIK2/SIK3 and PP1/PP2A-CRTC3 signaling.

Osteoporosis can result from the loss of sex hormones and/or aging. Abaloparatide (ABL), an analog of parathyroid hormone-related protein (PTHrP(1-36)), is the second osteoanabolic therapy approved by the United States Food and Drug Administration after teriparatide (PTH(1-34)). All three peptides bind PTH/PTHrP receptor type 1 (PTHR1), but the effects of PTHrP(1-36) or ABL in the osteoblast remain unclear. We show that, in primary calvarial osteoblasts, PTH(1-34) promotes a more robust cAMP response than PTHrP(1-36) and ABL and causes a greater activation of protein kinase A (PKA) and cAMP response element-binding protein (CREB). All three peptides similarly inhibited sclerostin (Sost). Interestingly, the three peptides differentially modulated two other PKA target genes, c-Fos and receptor activator of NF-κB ligand (Rankl), and the latter both in vitro and in vivo Knockdown of salt-inducible kinases (SIKs) 2 and 3 and CREB-regulated transcription coactivator 3 (CRTC3), indicated that all three are part of the pathway that regulates osteoblastic Rankl expression. We also show that the peptides differentially regulate the nuclear localization of CRTC2 and CRTC3, and that this correlates with PKA activation. Moreover, inhibition of protein phosphatases 1 and 2A (PP1/PP2A) activity revealed that they play a major role in both PTH-induced Rankl expression and the effects of PTH(1-34) on CRTC3 localization. In summary, in the osteoblast, the effects of PTH(1-34), PTHrP(1-36), and ABL on Rankl are mediated by differential stimulation of cAMP/PKA signaling and by their downstream effects on SIK2 and -3, PP1/PP2A, and CRTC3.

Parathyroid Hormone and Parathyroid Hormone-Related Protein Analogs in Osteoporosis Therapy.

PURPOSE OF REVIEW: The purpose is to review the efficacy and optimal use of parathyroid hormone and parathyroid hormone-related protein analogs in osteoporosis treatment. RECENT FINDINGS: The parathyroid hormone analog teriparatide, a potent stimulator of bone remodeling, increases hip and spine bone mineral density and reduces the risk of vertebral and non-vertebral fractures in postmenopausal osteoporotic women. The parathyroid hormone-related protein analog, abaloparatide, also reduces fracture incidence but has pharmacological effects that differ from teriparatide, particularly in cortical bone. These analogs provide maximal benefit when their use is followed by a potent antiresorptive medication. Moreover, studies have shown that the combination of teriparatide and the RANK-ligand inhibitor, denosumab, increase bone density and estimated strength more than monotherapy and more than any currently available regimen. Parathyroid hormone and parathyroid hormone-related protein analogs, whether as monotherapy, in combination with antiresorptive agents or in sequence with antiresorptive agents, will likely play an expanding role in osteoporosis management.

Diphtheria Toxin- and GFP-Based Mouse Models of Acquired Hypoparathyroidism and Treatment With a Long-Acting Parathyroid Hormone Analog.

Hypoparathyroidism (HP) arises most commonly from parathyroid (PT) gland damage associated with neck surgery, and is typically treated with oral calcium and active vitamin D. Such treatment effectively increases levels of serum calcium (sCa), but also brings risk of hypercalciuria and renal damage. There is thus considerable interest in using PTH or PTH analogs to treat HP. To facilitate study of this disease and the assessment of new treatment options, we developed two mouse models of acquired HP, and used them to assess efficacy of PTH(1-34) as well as a long-acting PTH analog (LA-PTH) in regulating blood calcium levels. In one model, we used PTHcre-iDTR mice in which the diphtheria toxin (DT) receptor (DTR) is selectively expressed in PT glands, such that systemic DT administration selectively ablates parathyroid cells. For the second model, we generated GFP-PT mice in which green fluorescent protein (GFP) is selectively expressed in PT cells, such that parathyroidectomy (PTX) is facilitated by green fluorescence of the PT glands. In the PTHcre-iDTR mice, DT injection (2 × 5 µg/kg, i.p.) resulted in moderate yet consistent reductions in serum PTH and sCa levels. The more severe hypoparathyroid phenotype was observed in GFP-PT mice following GFP-guided PTX surgery. In each model, a single subcutaneous injection of LA-PTH increased sCa levels more effectively and for a longer duration (>24 hours) than did a 10-fold higher dose of PTH(1-34), without causing excessive urinary calcium excretion. These new mouse models thus faithfully replicate two degrees of acquired HP, moderate and severe, and may be useful for assessing potential new modes of therapy. © 2015 American Society for Bone and Mineral Research.

Investigational parathyroid hormone receptor analogs for the treatment of osteoporosis.

INTRODUCTION: Intermittent parathyroid hormone (PTH) administration, acting through multiple signaling pathways, exerts an osteoanabolic effect on the skeleton that surpasses the effect of other antiosteoporotic agents. However, its efficacy is limited by the coupling effect and relatively common adverse events. Thus, the development of more sophisticated PTH receptor analogs seems imperative. AREAS COVERED: In this review, the authors summarize the role of PTH signaling pathway in bone remodeling. The authors also summarize investigational analogs targeting this pathway, which may be potential treatments for osteoporosis. EXPERT OPINION: ß-arrestins are multifunctional cytoplasmic molecules that are decisive for regulating intracellular PTH signaling. Recently, in preclinical studies, arrestin analogs have achieved the anabolic bone effect of PTH without an accompanying increase in bone resorption. However, it is not yet known whether these analogs have adverse effects and there are no clinical data for their efficacy to date. On the other hand, several molecules derived either from PTH and PTH-related protein (PTHrP) molecules have been developed. Alternative routes of PTH 1 - 34 delivery (oral, transdermal), the PTH analog ostabolin and the N-terminal PTHrP analogs PTHrP 1 - 36 and abaloparatide, have recently been or are currently being tested in clinical trials and are more likely to become available for use in the near future.

Treatment and prevention of chemotherapy-induced alopecia with PTH-CBD, a collagen-targeted parathyroid hormone analog, in a non-depilated mouse model.

Alopecia is a psychologically devastating complication of chemotherapy for which there is currently no effective therapy. PTH-CBD is a collagen-targeted parathyroid hormone analog that has shown promise as a therapy for alopecia disorders. This study compared the efficacy of prophylactic versus therapeutic administration of PTH-CBD in chemotherapy-induced alopecia using a mouse model that mimics the cyclic chemotherapy dosing used clinically. C57BL/6J mice were treated with a single subcutaneous injection of PTH-CBD (320 mcg/kg) or vehicle control before or after hair loss developing from three courses of cyclophosphamide chemotherapy (50-150 mg/kg/week). Mice receiving chemotherapy alone developed hair loss and depigmentation over 6-12 months. Mice pretreated with PTH-CBD did not develop these changes and maintained a normal-appearing coat. Mice treated with PTH-CBD after development of hair loss showed a partial recovery. Observations of hair loss were confirmed quantitatively by gray scale analysis. Histological examination showed that in mice receiving chemotherapy alone, there were small, dystrophic hair follicles mostly in the catagen phase. Mice receiving PTH-CBD before chemotherapy showed a mix of normal-appearing telogen and anagen hair follicles with no evidence of dystrophy. Mice receiving PTH-CBD therapy after chemotherapy showed intermediate histological features. PTH-CBD was effective in both the prevention and the treatment of chemotherapy-induced alopecia in mice, but pretreatment appears to result in a better cosmetic outcome. PTH-CBD shows promise as an agent in the prevention of this complication of chemotherapy and improving the quality of life for cancer patients.

Parathyroid hormone and parathyroid hormone-related protein analogs as therapies for osteoporosis.

Osteoporotic fractures result in significant morbidity and mortality. Anabolic agents reverse the negative skeletal balance that characterizes osteoporosis by stimulating osteoblast-dependent bone formation to a greater degree than osteoclast-dependent bone resorption. Parathyroid hormone (PTH) and parathyroid hormone- related protein (PTHrP) are peptide hormones, which have anabolic actions when administered intermittently. The only FDA-approved anabolic bone agent for the treatment of osteoporosis in the United States is PTH 1-34, or teriparatide, administered by daily subcutaneous injections. However, PTH 1-84 is also available in Europe. Synthetic human PTHrP 1-36 and a PTHrP 1-34 analog, BA058, have also been shown to increase lumbar spine bone density. These agents and several other PTH and PTHrP analogs, including some which are not administered as injections, continue to be investigated as potential anabolic therapies for osteoporosis.

Cyclic AMP directs inositol (1,4,5)-trisphosphate-evoked Ca2+ signalling to different intracellular Ca2+ stores.

Cholesterol depletion reversibly abolishes carbachol-evoked Ca(2+) release from inositol (1,4,5)-trisphosphate (IP3)-sensitive stores, without affecting the distribution of IP3 receptors (IP3R) or endoplasmic reticulum, IP3 formation or responses to photolysis of caged IP3. Receptors that stimulate cAMP formation do not alone evoke Ca(2+) signals, but they potentiate those evoked by carbachol. We show that these potentiated signals are entirely unaffected by cholesterol depletion and that, within individual cells, different IP3-sensitive Ca(2+) stores are released by carbachol alone and by carbachol combined with receptors that stimulate cAMP formation. We suggest that muscarinic acetylcholine receptors in lipid rafts deliver IP3 at high concentration to associated IP3R, stimulating them to release Ca(2+). Muscarinic receptors outside rafts are less closely associated with IP3R and provide insufficient local IP3 to activate IP3R directly. These IP3R, probably type 2 IP3R within a discrete Ca(2+) store, are activated only when their sensitivity is increased by cAMP. Sensitization of IP3R by cAMP extends the effective range of signalling by phospholipase C, allowing muscarinic receptors that are otherwise ineffective to recruit additional IP3-sensitive Ca(2+) stores.

Critical role of parathyroid hormone (PTH) receptor-1 phosphorylation in regulating acute responses to PTH.

Agonist-induced phosphorylation of the parathyroid hormone (PTH) receptor 1 (PTHR1) regulates receptor signaling in vitro, but the role of this phosphorylation in vivo is uncertain. We investigated this role by injecting "knock-in" mice expressing a phosphorylation-deficient (PD) PTHR1 with PTH ligands and assessing acute biologic responses. Following injection with PTH (1-34), or with a unique, long-acting PTH analog, PD mice, compared with WT mice, exhibited enhanced increases in cAMP levels in the blood, as well as enhanced cAMP production and gene expression responses in bone and kidney tissue. Surprisingly, however, the hallmark hypercalcemic and hypophosphatemic responses were markedly absent in the PD mice, such that paradoxical hypocalcemic and hyperphosphatemic responses were observed, quite strikingly with the long-acting PTH analog. Spot urine analyses revealed a marked defect in the capacity of the PD mice to excrete phosphate, as well as cAMP, into the urine in response to PTH injection. This defect in renal excretion was associated with a severe, PTH-induced impairment in glomerular filtration, as assessed by the rate of FITC-inulin clearance from the blood, which, in turn, was explainable by an overly exuberant systemic hypotensive response. The overall findings demonstrate the importance in vivo of PTH-induced phosphorylation of the PTHR1 in regulating acute ligand responses, and they serve to focus attention on mechanisms that underlie the acute calcemic response to PTH and factors, such as blood phosphate levels, that influence it.

ß-Arrestin-biased signaling of PTH analogs of the type 1 parathyroid hormone receptor.

Parathyroid hormone (PTH) is an anabolic agent that mediates bone formation through activation of the Gα(s)-, Gα(q)- and ß-arrestin-coupled parathyroid hormone receptor type 1 (PTH1R). Pharmacological evidence based on the effect of PTH(7-34), a PTH derivative that is said to preferentially activate ß-arrestin signaling through PTH1R, suggests that PTH1R-activated ß-arrestin signaling mediates anabolic effects on bone. Here, we performed a thorough evaluation of PTH(7-34) signaling behaviour using quantitative assays for ß-arrestin recruitment, Gα(s)- and Gα(q)-signaling. We found that PTH(7-34) inhibited PTH-induced cAMP accumulation, but was unable to induce ß-arrestin recruitment, PTH1R internalization and ERK1/2 phosphorylation in HEK293, CHO and U2OS cells. Thus, the ß-arrestin bias of PTH(7-34) is not apparent in every cell type examined, suggesting that correlating in vivo effects of PTH(7-34) to in vitro pharmacology should be done with caution.

[Effect of signal-selective parathyroid hormone analogue peptide on expressions of Wnt signaling factors].

OBJECTIVE: To study the effect of signal-selective parathyroid hormone (PTH) analogue peptide on Wnt signaling factors in osteoblasts isolated from neonatal mouse, and provide theoretical basis for the mechanism of PTH's function in bone metabolism. METHODS: Osteoblasts were isolated from calvaria of 2-3-day-old C57BL neonatal mouse and identified by alkaline phosphatase (ALP) staining, and Alizarin red staining. The cells at passage 1 were divided into 4 groups: control group, PTH (1-34) group, G1R19 (1-34) group, and G1R19 (1-28) group. Then the medium was changed to a-MEM supplemented with 1% FBS. After 12 hours, trifluoroacetic acid or three peptides [(10 nmol/L PTH (1-34), 10 nmol/L G1R19 (1-34), and 100 nmol/L G1R19 (1-28)] were added into the culture medium. After 4 hours, the cells were washed gently with cold PBS 3 times before total RNA was isolated. The expressions of Wnt related genes were measured by quantitative real-time PCR. RESULTS: Most of the cells were polygonal and triangular; the cells were positive for ALP staining with blue cytoplasm at 14 days and the Alizarin red staining showed the formation of red mineralized nodules in the special mineralization induction medium at 28 days. The expressions of osteocalcin mRNA and Wnt5b mRNA in PTH (1-34) group, G1R19 (1-34) group, and G1R19 (1-28) group were significantly higher than those in control group (P < 0.05); the expression of Wnt2 mRNA was significantly lower than that in control group (P < 0.05); the expression of beta-catenin mRNA in PTH (1-34) group was significantly higher than that in control group (P < 0.05); the expression of Wnt7b mRNA in PTH (1-34) group and G1R19 (1-34) group was higher than that in control group, and the G1R19 (1-34) group was higher than PTH (1-34) group and G1R19 (1-28) group (P < 0.05). CONCLUSION: In the Wnt-related factors, PTH (1-34) and G1R19 (1-34) affect mainly canonical Wnt signal factors, but the G1R19 (1-28) chiefly acts on non-canonical Wnt signal factors.

Oral bisphosphonate use increases the risk for inflammatory jaw disease: a cohort study.

PURPOSE: The objective of this study was to address whether among people living in Denmark, those treated with medications to prevent osteoporosis have an increased risk for inflammatory jaw disease compared with those not treated. PATIENTS AND METHODS: A historical cohort study was designed to compare the rate of inflammatory jaw-related events, ie, osteomyelitis, osteitis, periostitis, or sequestrum, between Danish patients who had been prescribed oral bisphosphonates (BP) and other drugs for the treatment of osteoporosis between 1996 and 2006 (the exposed group), and a random sample of the Danish population drawn from a nationwide registry who had not been prescribed oral BPs or other medications to treat osteoporosis (the nonexposed group). The nonexposed subjects were age- and gender-matched to the exposed subjects and randomly drawn from the general population at a ratio of 3 non-BP subjects to 1 BP subject. The primary explanatory variable was oral BP exposure status. Associations between BP treatment and inflammatory jaw events were ascertained using hazard ratios (HR) Cox proportional hazards models. RESULTS: The study sample was composed of 103,562 index subjects and 310,683 control subjects. After adjusting for other factors, including diabetes and chemotherapy, alendronate (HR = 3.15, 95% confidence interval 1.44-6.87) and etidronate (HR = 2.23, 95% confidence interval 1.15-4.31) were associated with an increased risk for inflammatory jaw events. There was no association between oral BP dose and risk for inflammatory jaw events. CONCLUSION: The oral BPs alendronate and etidronate were associated with an increased risk for inflammatory jaw events.

Regulation of CYP24 splicing by 1,25-dihydroxyvitamin D3 in human colon cancer cells.

CYP24 is a well-established vitamin D receptor (VDR) target gene. The active VDR ligand 1,25(OH)2D3 regulates its own catabolism by increasing CYP24 expression. It is well known that in the presence of 1,25(OH)2D3, VDR binds to VDREs in the promoter region of CYP24 and initiates CYP24 transcription. However, little is known about the role of 1,25(OH)2D3 in the posttranscriptional modulation of CYP24. In this study, we investigated the functional significance of 1,25(OH)2D3 in CYP24 RNA splicing in colon cancer cells. Using RT-PCR, we found that 1,25(OH)2D3 actively induces CYP24 splicing in a time-dependent manner and CYP24 splicing pattern could be cell type or tissue specific. The induction of RNA splicing by 1,25(OH)2D3 was mainly CYP24 selective. Treatment of cells with parathyroid hormone inhibited basal CYP24 splicing, but failed to inhibit 1,25(OH)2D3-induced CYP24 splicing. Further experiments demonstrated that new RNA synthesis was required for the induction of CYP24 splicing by vitamin D. In addition, alteration of multiple signaling pathways also affected CYP24 splicing and cellular sensitivity in response to vitamin D appeared to correlate with the induction of CYP24 splicing. These results suggest that 1,25(OH)2D3 not only regulates CYP24 transcription, but also plays an important role in posttranscriptional modulation of CYP24 by inducing its splicing. Our findings reveal an additional regulatory step that makes the vitamin D mediated action more prompt and efficient.

Nasal administration of a novel recombinant human parathyroid hormone (1-34) analog for the treatment of osteoporosis of ovariectomized rats.

Synthetic human parathyroid (1-34) (hPTH (1-34)) is known to have the full biological activity of the holohormone for osteoporosis. This study is about designing a novel analog of hPTH (1-34) which is more suitable for intranasal administration. We likewise evaluate effectiveness of the nasal drops against osteoroporosis. Through fusion expression of combining gene, cell disruption, inclusion body washing, ethanol fraction precipitation, acid hydrolysis, and CM-52 ion exchange column chromatography Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro was designed and produced. Nasal drops of Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro were prepared and administrated to ovariectomized rats. After 12 weeks of raising, Bone Material Densities (BMD) of vertebrae were examined by Dual Energy X-Ray Absorptiometry (DEXA). The average BMD of these groups treated with nasal drops of the peptide were 28.0%-47.2% (P<0.01) higher than that of the group treated with normal saline (NS). The subchondral bone plates of the femoral heads were examined by scanning electron microscopy and a defined planar section was photographed. Percentage of the area of the cancellous bone was calculated. Percentages of the groups treated with nasal drops of the peptide increased; values were significantly different to that of the group treated with NS (P<0.001) and were even equivalent to that of normal groups. These results show that nasal drops of Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro are effective against osteoporosis.

Metabolic bone diseases in patients after allogeneic hematopoietic stem cell transplantation: report from the Consensus Conference on Clinical Practice in chronic graft-versus-host disease.

With improved outcome of allogeneic stem cell transplantation (allo-SCT) for hematologic malignancies, long-term complications gain greater importance. Skeletal complications such as osteoporosis or avascular necrosis (AVN) occur frequently in allogeneic recipients with a cumulative incidence of diminished bone mineral density of 24-50% between 2 and 12 months after allo-SCT and a cumulative incidence of AVN in as many as 19% of patients 3 years after allo-SCT. Here, we present a review as part of the German, Austrian, and Swiss Consensus Conference on clinical practice in chronic graft-versus-host disease, held 2009 in Regensburg. The Consensus Conference aimed to achieve a consensus on the current evidence of diagnosis, prevention, and therapeutic options of late complications after allo-SCT summarizing and discussing the literature on these topics. In this report, we provide recommendations for metabolic bone diseases agreed upon by the working party. This includes guidelines for diagnosis, prevention, and therapeutic options in patients with low bone mass or AVN.

Acute down-regulation of sodium-dependent phosphate transporter NPT2a involves predominantly the cAMP/PKA pathway as revealed by signaling-selective parathyroid hormone analogs.

The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PTHR1) in cells of the renal proximal tubule mediates the reduction in membrane expression of the sodium-dependent P(i) co-transporters, NPT2a and NPT2c, and thus suppresses the re-uptake of P(i) from the filtrate. In most cell types, the liganded PTHR1 activates Gα(S)/adenylyl cyclase/cAMP/PKA (cAMP/PKA) and Gα(q/11)/phospholipase C/phosphatidylinositol 1,4,5-trisphosphate (IP(3))/Ca(2+)/PKC (IP(3)/PKC) signaling pathways, but the relative roles of each pathway in mediating renal regulation P(i) transport remain uncertain. We therefore explored the signaling mechanisms involved in PTH-dependent regulation of NPT2a function using potent, long-acting PTH analogs, M-PTH(1-28) (where M = Ala(1,12), Aib(3), Gln(10), Har(11), Trp(14), and Arg(19)) and its position 1-modified variant, Trp(1)-M-PTH(1-28), designed to be phospholipase C-deficient. In cell-based assays, both M-PTH(1-28) and Trp(1)-M-PTH(1-28) exhibited potent and prolonged cAMP responses, whereas only M-PTH(1-28) was effective in inducing IP(3) and intracellular calcium responses. In opossum kidney cells, a clonal cell line in which the PTHR1 and NPT2a are endogenously expressed, M-PTH(1-28) and Trp(1)-M-PTH(1-28) each induced reductions in (32)P uptake, and these responses persisted for more than 24 h after ligand wash-out, whereas that of PTH(1-34) was terminated by 4 h. When injected into wild-type mice, both M-modified PTH analogs induced prolonged reductions in blood P(i) levels and commensurate reductions in NPT2a expression in the renal brush border membrane. Our findings suggest that the acute down-regulation of NPT2a expression by PTH ligands involves mainly the cAMP/PKA signaling pathway and are thus consistent with the elevated blood P(i) levels seen in pseudohypoparathyroid patients, in whom Gα(s)-mediated signaling in renal proximal tubule cells is defective.

Parathyroid hormone-related protein regulates osteoclast inhibitory lectin expression via multiple signaling pathways in osteoblast-like cells.

Osteoclast inhibitory lectin (OCIL) is a recently identified inhibitor of osteoclast formation. A variety of osteotropic factors regulate OCIL expression in osteoblastic cells, however, little information is available to date concerning how this gene is controlled. Using real-time RT-PCR, we examined the regulation of OCIL expression by PTHrp and the signaling pathways used. We demonstrated in rat osteoblast-like UMR-106 cells, rat calvarial primary osteoblastic cells, and murine MC3T3-E1 cells, PTHrp(1-34) increased OCIL expression. In UMR-106 cells, the increase began and reached maximum later than RANKL induction and OPG suppression. cAMP/PKA signaling activators PTH(1-31), forskolin and dibutyryl cAMP (db-cAMP), and calcium ionophore A23187 all increased OCIL levels. In contrast, PKC activator phorbol-12-myristate-13-acetate reduced OCIL expression in short term but induced OCIL mRNA in long term. PKA inhibitor KT5720, mitogen-activated protein kinase (MAPK) cascade inhibitor PD98059, calmodulin antagonist W-7, and Ca(2+)/calmodulin-dependent protein kinase II (CaMK II) inhibitor KN-62 all significantly blunted PTHrp-stimulated OCIL expression. Moreover, PD98059 blocked the stimulation of OCIL by FSK or db-cAMP but not that by A23187. In primarily cultured osteoblasts, the PTHrp induction of OCIL was blocked by KT5720, W-7, and PD98059 as well. The data established that PTHrp(1-34) regulates OCIL expression in vitro through cAMP/PKA, Ca(2+)/CaMK II, and MAPK signaling pathways.

[The necessity of cost-effectiveness analysis in osteoporosis]. / De la nécessité des études coût-efficacité en ostéoporose.

Economic evaluations are increasingly being used by decision-makers to estimate the cost-effectiveness of interventions. Major changes have recently occurred in the treatment of osteoporosis. The development of a valid economic model (Markov) in the field of osteoporosis is discussed, as well as these limitations. Intervention, such hip protectors, calcium and vitamin D, bisphosphonates, hormonal replacement therapy, SERMs, strontium ranélate, analogue of parathyroid hormone are analysed in the light of cost-effectiveness analyses.