Histamine stimulates production of osteoclast differentiation factor/receptor activator of nuclear factor-kappaB ligand by osteoblasts

Oral administration of live combined Bacillus subtilis and Enterococcus faecium alleviates colonic oxidative stress and inflammation in osteoarthritic rats by improving fecal microbiome metabolism and enhancing the colonic barrier

Osteoarthritis (OA) causes intestinal damage. The protective effect of probiotics on the intestine is indeed effective; however, the mechanism of protection against intestinal damage in OA is not clear. In this study, we used meniscal/ligamentous injury (MLI) to mimic OA in rats and explored the colonic protective effects of Bacillus subtilis and Enterococcus faecium on OA. Our study showed that treatment with B. subtilis and E. faecium attenuated colonic injury and reduced inflammatory and oxidative stress factors in the serum of osteoarthritic rats. α- and ß diversity of the fecal flora were not different among groups; no significant differences were observed in the abundances of taxa at the phylum and genus levels. We observed the presence of the depression-related genera Alistipes and Paraprevotella. Analysis of fecal untargeted metabolism revealed that histamine level was significantly reduced in the colon of OA rats, affecting intestinal function. Compared to that in the control group, the enriched metabolic pathways in the OA group were primarily for energy metabolisms, such as pantothenate and CoA biosynthesis, and beta-alanine metabolism. The treatment group had enriched linoleic acid metabolism, fatty acid biosynthesis, and primary bile acid biosynthesis, which were different from those in the control group. The differences in the metabolic pathways between the treatment and OA groups were more evident, primarily in symptom-related metabolic pathways such as Huntington's disease, spinocerebellar ataxia, energy-related central carbon metabolism in cancer, pantothenate and CoA biosynthesis metabolic pathways, as well as some neurotransmission and amino acid transport, and uptake- and synthesis-related metabolic pathways. On further investigation, we found that B. subtilis and E. faecium treatment enhanced the colonic barrier of OA rats, with elevated expressions of tight junction proteins occludin and Zonula occludens 1 and MUC2 mRNA. Intestinal permeability was reduced, and serum LPS levels were downregulated in the treatment group. B. subtilis and E. faecium also regulated the oxidative stress pathway Keap1/Nrf2, promoted the expression of the downstream protective proteins HO-1 and Gpx4, and reduced intestinal apoptosis. Hence, B. subtilis and E. faecium alleviate colonic oxidative stress and inflammation in OA rats by improving fecal metabolism and enhancing the colonic barrier.

Immunology of osteoporosis: relevance of inflammatory targets for the development of novel interventions

Osteoporosis is recognized as low bone mass and deteriorated bone microarchitecture. It is the leading cause of fractures and consequent morbidity globally. The established pathophysiological evidence favors the endocrine factors for osteoporosis and the role of the immune system on the skeletal system has been recently identified. Due to the common developmental niche bone and immune system interactions have led to the emergence of osteoimmunology. Immune dysregulation can initiate inflammatory conditions that adversely affect bone integrity. The role of immune cells, such as T-lymphocytes subsets (Th17), cannot be neglected in the pathogenesis of osteoporosis. Local inflammation within the bone from any cause attracts immune cells that participate in the activation of osteoclasts. This work summarizes the present knowledge of osteoimmunology in reference to osteoporosis and identifies novel targets for immunotherapy of osteoporosis.

Effects of Histamine Receptor Antagonist Cetirizine on Orthodontic Tooth Movement

Many patients regularly take histamine receptor antagonists, such as cetirizine, to prevent allergic reactions, but these antiallergic drugs may have inadvertent effects on orthodontic treatment. In previous studies, histamine has been shown to modulate the sterile inflammatory reaction underlying orthodontic tooth movement. Pertinent effects of histamine antagonization via cetirizine during orthodontic treatment, however, have not been adequately investigated. We thus treated male Fischer344 rats either with tap water (control group) or cetirizine by daily oral gavage corresponding to the clinically used human dosage adjusted to the rat metabolism (0.87 mg/kg) or to a previously published high dosage of cetirizine (3 mg/kg). Experimental anterior movement of the first upper left molar was induced by insertion of a nickel-titanium (NiTi) coil spring (0.25 N) between the molar and the upper incisors. Cone-beam computed tomography (CBCT), micro-computed tomography (µCT) images, as well as histological hematoxylin-eosin (HE), and tartrate-resistant acid phosphatase (TRAP) stainings were used to assess the extent of tooth movement, cranial growth, periodontal bone loss, root resorptions, and osteoclast activity in the periodontal ligament. Both investigated cetirizine dosages had no impact on the weight gain of the animals and, thus, animal welfare. Neither the extent of tooth movement, nor cranial growth, nor root resorption, nor periodontal bone loss were significantly influenced by the cetirizine dosages investigated. We, thus, conclude that histamine receptor antagonist cetirizine can be used during orthodontic treatment to prevent allergic reactions without clinically relevant side effects on orthodontic tooth movement.

Effects of loratadine, a histamine H1 receptor antagonist, on the skeletal system of young male rats

Background

Histamine H₁ receptor antagonists are widely used in the treatment of allergic diseases. H₁ receptors are expressed on bone cells and histamine takes part in regulation of bone metabolism. Loratadine is often prescribed to children.

Purpose

The aim of the present study was to investigate the effects of loratadine on the skeletal system of young rats.

Material and methods

Loratadine (0.5, 5, and 50 mg/kg p.o. daily) was administered for 4 weeks to male Wistar rats, 6-week-old at the start of the experiment. Bone mass, mass of bone mineral, calcium, and phosphorus content in the bone mineral of the tibia, femur, and L-4 vertebra, histomorphometric parameters of the femur, mechanical properties of the proximal tibial metaphysis, femoral diaphysis and femoral neck, and serum levels of bone turnover markers were examined.

Results

Loratadine at 0.5 and 5 mg/kg did not significantly affect the skeletal system of young rats. At 50 mg/kg, loratadine decreased the femoral length, increased content of calcium and phosphorus in the bone mineral of the vertebra, and tended to improve mechanical properties of the tibial metaphysis.

Conclusion

High-dose loratadine slightly but significantly affected development of the skeletal system in rapidly growing rats.

Impaired skeletal health in patients with chronic atrophic gastritis

OBJECTIVE

In chronic atrophic gastritis (CAG), destruction of gastric parietal cells causes anacidity and hypergastrinemia. Use of proton pump inhibitors, which also induces gastric anacidity, is associated with increased fracture rates. Our objectives were to study possible differences in bone mineral density (BMD) and bone quality in patients with CAG compared to controls.

MATERIAL AND METHODS

We performed a cross-sectional study on 17 CAG patients aged 54 ± 13 years and 41 sex- and age-matched controls. Lumbar and femoral BMD and bone quality assessed by lumbar trabecular bone score (TBS) were measured by DXA, and bone material strength (BMS) by microindentation of the tibia. Serum bone markers (CTX, P1NP, sclerostin, osteocalcin, OPG, RANKL) were analyzed.

RESULTS

We found lower lumbar BMD Z-score (-0.324 ± 1.096 versus 0.456 ± 1.262, p = 0.030), as well as a higher frequency of osteoporosis at the lumbar spine (p = 0.046) and osteopenia at total hip (p = 0.019) in patients compared to controls. In a post hoc subgroup analysis, we observed that the differences were confined to the male patients. TBS also tended to be lower in male patients (p = 0.059), while BMS did not differ between the groups. Osteocalcin, sclerostin, OPG, and OPG/RANKL ratio were lower in patients compared to controls, while CTX and P1NP did not differ between the groups.

CONCLUSIONS

We observed lower lumbar BMD, increased frequency of osteopenia and osteoporosis in male, but not female patients with CAG. Bone markers suggest a decrease in bone formation and increased bone resorption in CAG patients compared to controls.

Effects of the Histamine 1 Receptor Antagonist Cetirizine on the Osteoporotic Phenotype in H(+) /K(+) ATPase Beta Subunit KO Mice

Epidemiological studies suggest increased fracture risk in patients using proton pump inhibitors (PPIs). We have previously shown that the H(+) /K(+) ATPase beta subunit knockout (KO) mouse, which is a model of PPI-use, have lower bone mineral density (BMD) and impaired bone quality compared to wild type (WT) mice. Like PPI users, these KO mice display elevated gastric pH and hypergastrinemia, which in turn stimulates gastric histamine release. Previous studies have suggested a negative effect of histamine on bone, thus, we wanted to study whether a histamine 1 receptor (H1R) antagonist could improve bone quality in KO mice. Female KO and WT mice aged 8 weeks received either an H1R antagonist (cetirizine) or polyethylene glycol (PEG) for 6 months. At the end of the study, KO mice displayed elevated plasma histamine levels compared to WT. As demonstrated previously, the KO mice also exhibited lower whole body BMD, reduced mechanical bone strength, and impaired bone quality assessed by μCT. No significant differences, however, were found between the KO groups receiving cetirizine or PEG for any of the measured bone parameters. In vitro gene expression analyses of histamine receptors revealed the presence of H1R and H2R both in osteoblasts and osteoclasts, and H3R in late stage osteoblasts. In conclusion, administration of the H1R antagonist cetirizine in a concentration of 3 mg/kg did not rescue the osteoporotic phenotype in H(+) /K(+) ATPase beta subunit KO mice. It can, however, not be ruled out that histamine may influence bone via other receptors. J. Cell. Biochem. 117: 2089-2096, 2016. © 2016 Wiley Periodicals, Inc.

[Expression and function of the histamine receptors in dermal and articular tissues]

Histamine was first identified in 1910 as a physiologically active amine. It is now recognized for its multiple regulatory activities in the digestive, neuronal, and immune systems, and new roles are still being elucidated. Histamine exerts its effects through four distinct receptor subtypes. The histamine H4 receptor was identified in 2000 and is the most recently identified of the four histamine receptors. It is expressed primarily in immune cells and is involved in physiologic functions related to inflammation and allergy. Recently, the H4 receptor was highlighted as a promising therapeutic target in atopic dermatitis, asthma, and chronic arthritis. In fact, some H4 receptor antagonists have reached clinical trials for the treatment of asthma, atopic dermatitis, and allergic rhinitis. Based on an initial assessment of its distribution, the H4 receptor has been referred to as the histamine receptor of the hematopoietic system. However, the H4 receptor has also been implicated in the regulation of other non-hematopoietic systems. Here, I review the expression and function of the identified histamine receptors, including the H4 receptor with a focus on articular and dermal tissues. In articular tissue, H4 receptor expression has been detected in synovial cells. Chondrocytes, a major cell source for cartilage tissue engineering, also express the H4 receptor. In skin, the H4 receptor is expressed in both the epidermis and dermis, with stronger receptor expression in the epidermis. Further understanding of the functions of H4 receptors in non-hematopoietic cells might lead to novel treatments for diseases with unmet medical needs.

Lemnalol attenuates mast cell activation and osteoclast activity in a gouty arthritis model

OBJECTIVES

In this study, we investigated the effects of a soft coral-derived anti-inflammatory compound, lemnalol, on mast cell (MC) function and osteoclast activity in rats with monosodium urate (MSU) crystal-induced gouty arthritis.

METHODS

In this study, we examined the therapeutic effects of lemnalol on intra-articular injection of MSU induces gouty arthritis with the measurement of ankle oedema. Toluidine blue staining were used to analyse the infiltration and the percentage degranulation MCs. Immunohistochemical analysis showed CD117, transforming growth factor beta 1 (TGF-β1), matrix metalloproteinase 9 (MMP-9), the osteoclast markers cathepsin K and tartrate-resistant acid phosphatase (TRAP) protein expression in ankle tissue.

KEY FINDINGS

We found that both infiltration and degranulation of MCs increased at 24 h after MSU injection in the ankle joint. Immunohistochemical analysis showed that MSU induced upregulation of TGF-β1, MMP-9, the osteoclast markers cathepsin K and TRAP in ankle tissues. Administration of lemnalol ameliorated MSU-induced TGF-β1, MMP-9, cathepsin K and TRAP protein expression.

CONCLUSIONS

Taken together, our results show that MSU-induced gouty arthritis is accompanied by osteoclast-related protein upregulation and that lemnalol treatment may be beneficial for the attenuation of MC infiltration and degranulation and for suppressing osteoclast activation in gouty arthritis.

Modifications of histamine receptor signaling affect bone mechanical properties in rats

Histamine receptors are expressed on bone cells and histamine may be involved in regulation of bone metabolism. The aim of the present study was to investigate the effects of loratadine (an H(1) receptor antagonist), ranitidine (an H(2) receptor antagonist) and betahistine (an H(3) receptor antagonist and H(1) receptor agonist) on bone mechanical properties in rats. Loratadine (5 mg/kg/day, po), ranitidine (50 mg/kg/day, po), or betahistine dihydrochloride (5 mg/kg/day, po), were administered for 4 weeks to non-ovariectomized and bilaterally ovariectomized (estrogen-deficient) 3-month-old rats, and their effects were compared with appropriate controls. Serum levels of bone turnover markers, bone mineralization and mechanical properties of the proximal tibial metaphysis, femoral diaphysis and femoral neck were studied. In rats with normal estrogen level, administration of loratadine slightly favorably affected mechanical properties of compact bone, significantly increasing the strength of the femoral neck (p < 0.05), and tending to increase the strength of the femoral diaphysis. Ranitidine did not significantly affect the investigated parameters, and betahistine decreased the strength of the tibial metaphysis (cancellous bone, p < 0.01). There were no significant effects of the drugs on serum bone turnover markers. In estrogen-deficient rats, the drugs did not significantly affect the investigated skeletal parameters. In conclusion, the effects of histamine H(1), H(2) and H(3) receptor antagonists on the skeletal system in rats were differential and dependent on estrogen status.

The ability of H1 or H2 receptor antagonists or their combination in counteracting the glucocorticoid-induced alveolar bone loss in rats

BACKGROUND

The aim of the present study was to compare between three possible osteoporotic treatments in prevention of glucocorticoid-induced alveolar bone loss.

METHODS

Fifty adult female Wistar rats with an average weight 150-200 g were randomized into five groups: group I (control) was intraperitoneally injected with saline. The other experimental groups (II & III, IV & V) were intraperitoneally injected with 200 µg/100 g body weight dexamethasone. The experimental groups III, IV and V received intraperitoneal injection of 10 mg/kg/day pheniramine maleate (H1 receptor antagonist), ranitidine hydrochloride (H2 receptor antagonist) and concomitant doses of both H1 & H2 receptor antagonists respectively. After 30 days, the rats have been sacrificed. The mandibles were examined histologically, histochemically and histomorphometrically. The bone mineral density was measured using dual-energy X-ray absorptiometry (DEXA).

RESULTS

Histopathologically the glucocorticoid group showed wide medullary cavities with wide osteocytic lacunae. These marrow cavities were reduced in the prophylactic groups (III, IV) but increased in group V. Bone histomorphometric analysis revealed improvement in static bone parameters in groups III and IV and deterioration in group V in comparison to group II. The DEXA revealed significant reduction in the bone mineral density in all experimental groups compared to the control group.

CONCLUSIONS

In a rat model, the administration of H1 or H2 receptor antagonists separately could minimize the alveolar bone loss caused by the administration of glucocorticoids while concomitant administration of both H1 and H2 receptor antagonists deteriorated the bone condition.

Increased apoptosis in osteoclasts and decreased RANKL immunoexpression in periodontium of cimetidine-treated rats

It has been demonstrated that histamine interferes with the recruitment, formation and activity of osteoclasts via H(1)- and H(2)-receptors. Cimetidine is a H(2)-receptor antagonist used for treatment of gastric ulcers that seems to prevent bone resorption. In this study, a possible cimetidine interference was investigated in the number of alveolar bone osteoclasts. The incidence of osteoclast apoptosis and immunoexpression of RANKL (receptor activator of nuclear factor κB ligand) was also evaluated. Adult male rats were treated with 100 mg kg(-1) of cimetidine for 50 days (CimG); the sham group (SG) received saline. Maxillary fragments containing the first molars and alveolar bone were fixed, decalcified and embedded in paraffin. The sections were stained by H&E or submitted to tartrate-resistant acid phosphatase (TRAP) method. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) method and immunohistochemical reactions for detecting caspase-3 and RANKL were performed. The number of TRAP-positive osteoclasts, the frequency of apoptotic osteoclasts and the numerical density of RANKL-positive cells were obtained. Osteoclast death by apoptosis was confirmed by transmission electron microscopy (TEM). In CimG, TRAP-positive osteoclasts with TUNEL-positive nuclei and caspase-3-immunolabeled osteoclasts were found. A significant reduction in the number of TRAP-positive osteoclasts and a high frequency of apoptotic osteoclasts were observed in CimG. Under TEM, detached osteoclasts from the bone surface showed typical features of apoptosis. Moreover, a significant reduction in the numerical density of RANKL-positive cells was observed in CimG. The significant reduction in the number of osteoclasts may be due to cimetidine-induced osteoclast apoptosis. However, RANKL immunoexpression reduction also suggests a possible interference of cimetidine treatment in the osteoclastogenesis.

The anti-allergic compound tranilast attenuates inflammation and inhibits bone destruction in collagen-induced arthritis in mice

BACKGROUND AND PURPOSE

Recent findings suggest the importance of mast cells in the pathogenesis of rheumatoid arthritis and their potential as a therapeutic target. Tranilast is an anti-allergic compound with a potent membrane-stabilizing effect on mast cells and a wide range of anti-inflammatory effects, thus may be advantageous in the treatment of arthritis. Here, we have evaluated the effects of tranilast on the progression of collagen-induced arthritis in mice.

EXPERIMENTAL APPROACH

Tranilast (400 mg.kg(-1).day(-1)) was orally administered for 8 weeks to mice with established collagen-induced arthritis. Arthritis was assessed by clinical signs and X-ray scores. In paw tissue, the numbers of mast cells and osteoclasts were measured by histological analysis, and several inflammatory factors were assessed by RT-PCR and Western blot analysis.*

KEY RESULTS

TNF-alpha-positive mast cells were present extensively throughout the inflamed synovium of vehicle-treated arthritic mice, with some mast cells in close proximity to osteoclasts in areas of marked bone and cartilage destruction. Tranilast significantly reduced clinical and X-ray scores of arthritis and decreased numbers of TNF-alpha-positive mast cells and mRNA levels of TNF-alpha, chymase (mouse mast cell protease 4), tryptase (mouse mast cell protease 6), stem cell factor, interleukin-6, cathepsin-K, receptor activator of nuclear factor-kappaB, and of receptor activator of nuclear factor-kappaB-ligand, but increased interleukin-10 mRNA level in paws of arthritic mice. Osteoclast numbers were decreased by treatment with tranilast.

CONCLUSIONS AND IMPLICATIONS

Tranilast possesses significant anti-rheumatic efficacy and, probably, this therapeutic effect is partly mediated by inhibition of mast cell activation and osteoclastogenesis.

Histamine promotes osteoclastogenesis through the differential expression of histamine receptors on osteoclasts and osteoblasts

In addition to the numerous roles of histamine in both the immune and nervous systems, previous studies have suggested that this bioamine might also be involved in bone metabolism. Following our observations of impaired bone resorption in ovariectomized rats after histamine receptor antagonist treatment, we focused in this study on osteoclasts and osteoclast precursors. We looked for a direct action of histamine on these cells using both in vivo and in vitro approaches. In vivo, we triggered a remodeling sequence in rat mandibular bone and treated the animals with either histamine or histamine receptor antagonists. Histamine was shown to increase the number of osteoclasts and osteoclast precursors whereas antagonists of histamine receptor-1 and -2 decreased both osteoclast recruitment and resorption. In vitro, spleen cells from histamine-deficient mice were treated with receptor activator for nuclear factor kappa B ligand and macrophage colony stimulating factor, giving rise to both reduced numbers of osteoclasts and decreased resorption on dentin slices. Histamine enhanced resorption in these cultures in a dose-dependent manner. In addition, we identified osteoclast precursors as a source of histamine. In contrast, histamine increased the receptor activator for nuclear factor kappa B ligand/osteoprotegerin ratio in primary osteoblasts that did not secrete histamine. We observed a differential expression of histamine receptor-1 and -2 mRNAs in both primary osteoclasts and osteoblasts, confirming their functional roles with selective antagonists. Thus, histamine acts directly on osteoclasts, osteoclast precursors, and osteoblasts, promoting osteoclastogenesis through autocrine/paracrine mechanisms.

Antihistamine therapy and bone mineral density: analysis in a population-based US sample

BACKGROUND

Histamine may play an important role in bone turnover. The data regarding histamine 1 receptor antagonist (H1RA), histamine 2 receptor antagonist (H2RA), and bone mineral density in humans are sparse. We examined bone mineral density in subjects using histamine receptor antagonists in a representative US population-based sample from the Third National Health and Nutrition Examination Survey (1988-1994).

METHODS

Adult subjects aged 60 years and more using H1RA or H2RA who underwent dual energy x-ray absorptiometry scanning in the Third National Health and Nutrition Examination Survey were identified. We compared the femoral neck bone mineral density among users of these agents with nonusers in adjusted linear regression models that included known demographic, anthropometric, and medical risk factors for osteoporosis.

RESULTS

The mean age of the study subjects was 72.6 years; 52% were women and 59% were white. Among subjects with femoral neck bone mineral density measured, 199 used H1RAs, 297 used H2RAs, and 4162 were nonusers of histamine receptor antagonists. Femoral neck bone mineral density adjusting for age and gender and other covariates was slightly higher in H1RA users (0.74 g/cm(2)) versus nonusers (0.72 g/cm(2); P=.037). H2RA users showed slightly lower adjusted bone mineral density compared with nonusers (0.69 g/cm(2) vs 0.72 g/cm(2); P=.003), but bone densities were similar between H2RA users and nonusers when daily calcium intake exceeded 800 mg per day.

CONCLUSION

Femoral neck bone mineral density may be higher in H1RA users than nonusers among older adults. H2RA users with reduced calcium intake had lower bone mineral density than nonusers.

Inhibitory effects of Ficus erecta leaves on osteoporotic factors in vitro

Osteoporosis is recognized as a major concern among menopausal women and the elderly. When estrogen is reduced in the body, local factors such as IL-1beta, IL-6 and PGE2, which are known to be related to bone resorption, are increased and promote osteoclastogenesis, which is responsible for bone resorption and results in the clinical disorder osteoporosis. In this study, we investigated the anti-osteoporotic activity of Ficus erecta. MG-63 cells were stimulated with IL-1beta (10 ng/mL) to induce osteoporotic factors (IL-6, COX-2 and PGE2) and RAW 264.7 cells were stimulated with RANKL (100 ng/mL) to induce their differentiation into osteoclasts. We found F. erecta fractions decreased the mRNA expression of IL-6 and COX-2, and protein levels of COX-2 and PGE2 production. Among sequential solvent fractions, hexane and EtOAc fractions decreased differentiation into osteoclasts of RAW 264.7 cells. These results suggest that F. erecta may have significant effects on osteoporotic factors and may be provided as a possible anti-osteoporotic therapeutic plant.

Mast cell activation and degranulation occur early during induction of periosteal bone resorption

We have previously postulated that mast cells participate in the cellular network involved in osteoclastic resorption, probably through histamine release. In this study, we examined mast cell activation and histamine release during origination of resorption. Groups of 10 rats were killed 0, 0.5, 1, 1.5, 3, 6, 9, 12 and 18 h after induction of resorption in a synchronized model of cortical resorption along the mandible. The total number of mast cells was transiently decreased by about one-third at 1 and 9 h. Mast cell activation was monitored by Alcian blue-safranin staining. Early after induction, mast cells started to release their mediator stores; complete release led to the apparent disappearance of the cells with the staining technique used. Histamine immunostaining confirmed the release of histamine and its diffusion in the extracellular environment. Massive degranulation was observed at 1.5 and 9 h with toluidine blue staining. Cell recovery, assessed in terms of histidine decarboxylase expression, occurred gradually. The number of ED1+ osteoclast precursors strongly increased from 12 h up to 18 h. Most parameters had returned to baseline at 18 h, except the ED1+ cells. H2 receptor inhibition with famotidine strongly decreased ED1+ osteoclast precursors at 12 h and subsequently osteoclasts at the peak of resorption. These data support a role of mast cells in resorption origination. They show an early and transient intervention of mast cells in the events regulating the recruitment of circulating osteoclast precursors and ultimately of resorption. Mast cell activation and degranulation induce the release of mediators, particularly histamine acting through its H2 receptors, which are likely involved in these reactions.

Increased bone fracture prevalence in postmenopausal women suffering from pollen-allergy

INTRODUCTION

Our aim was to investigate whether pollen-allergy can affect bone mass and fractures in postmenopausal women.

METHODS

A total of 125 postmenopausal pollen-allergic women (mean age: 61.26 yr) were split into four groups: (1) treated with neither H1 histamine receptor (H1R) antagonist nor inhaled corticosteroid (n=43); (2) treated only with H1R antagonist (n=53); (3) treated with both H1R antagonist and inhaled corticosteroid (n=17); (4) treated with only inhaled corticosteroid (n=12). Treatment, in the appropriate groups, had occurred for at least 5 years, seasonally. One-hundred non-allergic postmenopausal subjects matched for age, body mass index (BMI), and age at menopause served as controls.

RESULTS

Overweight and obesity (25 kg/m(2) < or =BMI) were common among the allergic women (76%). Allergic patients without treatment had a slightly lower bone density than their non-allergic counterparts. The rate (34.9%) of prevalent low-energy fractures (distal forearm, hip, and clinical vertebral fractures) in untreated allergic patients was almost triple that observed in non-allergic women (13%, chi(2) p=0.003). Bone fracture occurred more often in H1R-only treated patients (30.19%) than in controls (chi(2) p=0.01); however, clinical vertebral or hip fractures developed neither in those treated only with H1R antagonist nor in those who received both H1R antagonist and inhaled corticosteroid. Bone fractures were more frequent among patients with inhaled steroid treatment than among patients with a combined treatment of inhaled steroid and antihistamine (50 versus 29.4%). BMI predicted prevalent fractures at 1.278 (95% CI: 1.047-1.559, p=0.016) for a 1 kg/m(2) increase among untreated allergic patients.

CONCLUSION

In conclusion, we found a high prevalence of low-energy fractures among pollen-allergic postmenopausal women which was associated with obesity. It is possible that the H1R antagonists compensate for both the negative effect of pollen-allergy and the adverse effect of inhaled corticosteroid treatment on bone fracture risk.

mu-Calpain regulates receptor activator of NF-kappaB ligand (RANKL)-supported osteoclastogenesis via NF-kappaB activation in RAW 264.7 cells

To clarify the role of calpain in the receptor activator of NF-kappaB ligand (RANKL)-supported osteoclastogenesis, RANKL-induced calpain activation was examined by using murine RAW 264.7 cells and bone marrow-derived monocyte/macrophage progenitors. We found that calpain activity increased in response to RANKL in both cell types based on alpha-spectrinolysis and that mu-calpain, rather than m-calpain, was activated during RANKL-supported osteoclastogenesis in RAW 264.7 cells. Overexpression of mu-calpain clearly augmented RANKL-supported osteoclastogenesis in RAW 264.7 cells, thereby implicating its pivotal role in this process. Cell-permeable calpain inhibitors, including calpastatin and calpeptin, were sufficient to suppress RANKL-supported osteoclastogenesis based on decreased expression of the osteoclastogenic marker, matrix metalloproteinase 9, and the generation of tartrate-resistant acid phosphatase-positive multinucleated cells in both cell types. Calpain inhibitors suppressed NF-kappaB activation via inhibition of the cleavage of inhibitor of NF-kappaB(IkappaBalpha)in RAW 264.7 cells. Taken together, our findings suggest that mu-calpain is essential to the regulation of RANKL-supported osteoclastogenesis via NF-kappaB activation.

The molecular triad OPG/RANK/RANKL: involvement in the orchestration of pathophysiological bone remodeling

The past decade has seen an explosion in the field of bone biology. The area of bone biology over this period of time has been marked by a number of key discoveries that have opened up entirely new areas for investigation. The recent identification of the receptor activator of nuclear factor kappaB ligand (RANKL), its cognate receptor RANK, and its decoy receptor osteoprotegerin (OPG) has led to a new molecular perspective on osteoclast biology and bone homeostasis. Specifically, the interaction between RANKL and RANK has been shown to be required for osteoclast differentiation. The third protagonist, OPG, acts as a soluble receptor antagonist for RANKL that prevents it from binding to and activating RANK. Any dysregulation of their respective expression leads to pathological conditions such as bone tumor-associated osteolysis, immune disease, or cardiovascular pathology. In this context, the OPG/RANK/RANKL triad opens novel therapeutic areas in diseases characterized by excessive bone resorption. The present article is an update and extension of an earlier review published by Kwan Tat et al. [Kwan Tat S, Padrines M, Theoleyre S, Heymann D, Fortun Y. IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology. Cytokine Growth Factor Rev 2004;15:49-60].

“Culture shock” from the bone cell's perspective: emulating physiological conditions for mechanobiological investigations

Bone physiology can be examined on multiple length scales. Results of cell-level studies, typically carried out in vitro, are often extrapolated to attempt to understand tissue and organ physiology. Results of organ- or organism-level studies are often analyzed to deduce the state(s) of the cells within the larger system(s). Although phenomena on all of these scales—cell, tissue, organ, system, organism—are interlinked and contribute to the overall health and function of bone tissue, it is difficult to relate research among these scales. For example, groups of cells in an exogenous, in vitro environment that is well defined by the researcher would not be expected to function similarly to those in a dynamic, endogenous environment, dictated by systemic as well as organismal physiology. This review of the literature on bone cell culture describes potential causes and components of cell “culture shock,” i.e., behavioral variations associated with the transition from in vivo to in vitro environment, focusing on investigations of mechanotransduction and experimental approaches to mimic aspects of bone tissue on a macroscopic scale. The state of the art is reviewed, and new paradigms are suggested to begin bridging the gap between two-dimensional cell cultures in petri dishes and the three-dimensional environment of living bone tissue.

Myeloma cells can directly contribute to the pool of RANKL in bone bypassing the classic stromal and osteoblast pathway of osteoclast stimulation

Summary The ratio of osteoprotegerin [OPG, tumour necrosis factor receptor superfamily, member 11b (TNFRSF11B)] to receptor activator of nuclear factor kappaB ligand [RANKL, tumour necrosis factor (ligand) superfamily, member 11 (TNFSF11)] in bone is critical for the regulation of bone remodelling. Myeloma cells can home to bone, triggering increased RANKL and decreased OPG expression by stromal cells, leading to osteolysis. Whether myeloma cells contribute directly to the pool of RANKL or OPG in bone has been contentious. Here we provide evidence of RANKL expression by reverse transcription polymerase chain reaction and in situ hybridization, demonstrating transcripts encoding both the membrane-bound and secreted forms of RANKL in five human multiple myeloma cell lines (LP-1, NCI-H929, OPM-2, RPMI8226, U266) and myeloma cells purified from bone marrow aspirates of myeloma patients. We demonstrated that RANKL encoding mRNAs are translated to protein by antibody detection of RANKL. In vitro assays showed that myeloma cells induced bone marrow derived mononuclear cells to differentiate into adherent tartrate-resistant acid phosphatase positive multinucleated cells, indicative of the formation of functional osteoclasts. This differentiation could also be achieved with passaged myeloma media alone, implicating secreted products. Finally, we provide evidence that the differentiation observed is at least in part the result of myeloma cell expression of RANKL. We therefore conclude that myeloma cells can directly contribute to the pool of RANKL in bone.

NEW MOLECULES IN THE TUMOR NECROSIS FACTOR LIGAND AND RECEPTOR SUPERFAMILIES WITH IMPORTANCE FOR PHYSIOLOGICAL AND PATHOLOGICAL BONE RESORPTION

Osteoclasts are tissue-specific polykaryon bone-resorbing cells derived from the monocyte/macrophage hematopoietic lineage with specialized functions required for the adhesion of the cells to bone and the subsequent polarization of the cell membrane, secretion of acid to dissolve mineral crystals, and release of proteolytic enzymes to degrade the extracellular matrix proteins. Most pathological conditions in the skeleton lead to loss of bone due to excess osteoclastic bone resorption, including periodontal disease, rheumatoid arthritis, and osteoporosis. In rare cases, most of them genetic, patients with osteopetrosis exhibit sclerotic bone due either to a lack of osteoclasts or to non-functional osteoclasts. Mainly because of phenotypic findings in genetically manipulated mice or due to spontaneous mutations in humans, mice, and rats, several genes have been discovered as being crucial for osteoclast formation and activation. Recent breakthroughs in our understanding of osteoclast biology have revealed the critical roles in osteoclast differentiation played by RANKL, RANK, and OPG, three novel members of the tumor necrosis factor ligand and receptor superfamilies. The further study of these molecules and downstream signaling events are likely to provide a molecular basis for the development of new drugs for the treatment of diseases with excess or deficient osteoclastic bone resorption.

Molecular mechanisms underlying osteoclast formation and activation

Osteoporosis is one of the leading causes of morbidity in the elderly and is characterized by a progressive loss of total bone mass and bone density. Bone loss in osteoporosis is due to the persistent excess of osteoclastic bone resorption over osteoblastic bone formation. Receptor activator of NFkappaB ligand (RANKL) critically regulates both osteoclast differentiation and activation. TRAFs appear to be central coupling molecules in the signal transduction pathways that regulate osteoclastogenesis, cathepsin K is the major mediator of osteoclastic bone resorption, and sex steroids and aging also affect osteoclastogenesis and osteoclast activity. However, bone homeostasis depends upon the intimate coupling of bone formation and bone resorption, wherein both osteoclasts and osteoblasts exert vital stimulatory and inhibitory effects upon each other via molecules such as RANKL, TGFbeta, PDGF, BMP2, and Mim-1. This review will highlight some of the major features of the complex circuit of cytokines, growth factors, and hormones that underlies the formation and function of osteoclasts and the dynamic equilibrium that marks the interaction between osteoclasts and osteoblasts.

Targeted deletion of histidine decarboxylase gene in mice increases bone formation and protects against ovariectomy-induced bone loss

Targeted disruption of the histidine decarboxylase gene (HDC(-/-)), the only histamine-synthesizing enzyme, led to a histamine-deficient mice characterized by undetectable tissue histamine levels, impaired gastric acid secretion, impaired passive cutaneous anaphylaxis, and decreased mast cell degranulation. We used this model to study the role of histamine in bone physiology. Compared with WT mice, HDC(-/-) mice receiving a histamine-free diet had increased bone mineral density, increased cortical bone thickness, higher rate of bone formation, and a marked decrease in osteoclasts. After ovariectomy, cortical and trabecular bone loss was reduced by 50% in HDC(-/-) mice compared with WT. Histamine deficiency protected the skeleton from osteoporosis directly, by inhibiting osteoclastogenesis, and indirectly, by increasing calcitriol synthesis. Quantitative RT-PCR showed elevated 25-hydroxyvitamin D-1alpha-hydroxylase and markedly decreased 25-hydroxyvitamin D-24-hydroxylase mRNA levels. Serum parameters confirming this indirect effect included elevated calcitriol, phosphorus, alkaline phosphatase, and receptor activator of NF-kappaB ligand concentrations, and suppressed parathyroid hormone concentrations in HDC(-/-) mice compared with WT mice. After ovariectomy, histamine-deficient mice were protected from bone loss by the combination of increased bone formation and reduced bone resorption.

The histamine H2-receptor antagonist, cimetidine, inhibits the articular osteopenia in rats with adjuvant-induced arthritis by suppressing the osteoclast differentiation induced by histamine

The effects of cimetidine on rat adjuvant arthritis (AA) and rat osteoclast differentiation were studied. For the in vivo experiments, AA was induced by injections of Mycobacterium tuberculosis H37RA either subcutaneously into the base of the tail or into the right hind paw. The osteoclast differentiation was assessed by estimating the number of tartrate-resistant acid phosphatase-positive multinuclear cells in the bone marrow culture. Cimetidine, at the dose of 25 mg/kg body weight, reduced the paw swelling by 70% (P<0.01). Cimetidine, at 10 microM concentration, inhibited 1,25-dihydroxyvitamin D(3) (1,25[OH](2)D(3)) and histamine mediated osteoclast differentiations by 40% (P<0.01) and 60% (P<0.001), respectively. Dimaprit, at 0.3 microM, stimulated the cell differentiation by 100% (P<0.01). Mepyramine reduced osteoclast differentiation, but the reduction was not statistically significant. Measurements of bone mineral density of the femur indicated that 5 mg/kg of cimetidine treated animals had 30% (P<0.01) higher mineral density in comparison with that of the AA control group that received no cimetidine. These results suggest that histamine is a potent inducer of osteoclast differentiation, at least in part, through the histamine H(2)-receptor, and cimetidine has a preventive effect on articular destruction and accompanying inflammation in arthritic rats. These observations may provide critical insights into the pathogenesis of the bone pathology seen in patients with RA.