Properties and expression of human tartrate-resistant acid phosphatase isoform 5a by monocyte-derived cells

Dose-response effect of Montelukast on post-extraction dental socket repair and skeletal phenotype of mice

Bone metabolism and repair are directly regulated by arachidonic acid metabolites. At present, we analyzed the dose-response effects of a selective cysteinyl leukotriene receptor type-1 antagonist during bone repair after tooth extraction and on non-injured skeleton. Sixty-three 129 Sv/Ev male mice composed the groups: C-Control (saline solution); MTK2-2 mg/Kg of Montelukast (MTK) and MTK4-4 mg/Kg of MTK, daily administered by mouth throughout all experimental periods set at 7, 14, and 21 days post-operative. Dental sockets were analyzed by computed microtomography (microCT), histopathology, and immunohistochemistry. Femurs, L5 vertebra and organs were also removed for observation. Blood was collected for plasma bone and liver markers. Histopathology and microCT analysis revealed early socket repair of MTK2 and MTK4 animals, with significant increased BV/TV at days 14 and 21 compared to C. Higher plasma calcium was detected at days 7 and 21 in MTK4 in comparison to C, while phosphate was significantly increased in MTK2 in the same periods in comparison to C and MTK4. No significant differences were found regarding plasma ALP and TRAP, neither for local TRAP and Runx2 immunolabeling at the healing sockets. Organs did not present histological abnormalities. Increased AST levels have been detected in distinct groups and periods. In general, femur phenotype was improved in MTK treated animals. Collectively, MTK promoted early bone formation after tooth extraction and increased bone quality of femurs and vertebra in a time-dose-dependent manner, and should be considered as an alternative therapy when improved post-extraction socket repair or skeleton preservation is required.

Nitro-fatty acids decrease type I interferons and monocyte chemoattractant protein 1 in ex vivo models of inflammatory arthritis

BACKGROUND

Inflammatory arthritis including rheumatoid arthritis (RA) and spondyloarthritis (SpA) is characterized by inflammation and destruction of the joints. Approximately one third of patients do not respond to first-line treatments. Nitro-fatty acids are bioactive lipids with anti-inflammatory properties and tissue-protective functions. The nitro-fatty acid 10-NO₂-oleic acid (10-NO₂-OA) is being tested in clinical trials for patients with fibrotic and inflammatory conditions. Here, we tested whether 10-NO₂-OA could inhibit immune reactions involved in the inflammatory and joint destructive processes in inflammatory arthritis.

METHODS

Synovial fluid and blood samples were obtained from 14 patients with active RA or SpA. The in vitro models consisted of synovial fluid mononuclear cells (SFMCs) cultured for 48 h, SFMCs cultured for 21 days, and fibroblast-like synovial cells (FLSs) co-cultured with peripheral blood mononuclear cells (PBMCs) for 48 h. Cells were treated with or without 10-NO₂-OA or the tumor necrosis factor alpha (TNFα) inhibitor etanercept. Supernatants were analyzed for type I interferon, monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase 3 (MMP3) and tartrate resistant acid phosphatase (TRAP).

RESULTS

In SFMCs cultured for 48 h, 10-NO₂-OA dose-dependently decreased the secretion of bioactive type I interferons and MCP-1 but not MMP3 (P = 0.032, P = 0.0001, and P = 0.58, respectively). Both MCP-1 and MMP3 were decreased by etanercept (P = 0.0031 and P = 0.026, respectively). In SFMCs cultured for 21 days, 10-NO₂-OA significantly decreased the production of MCP-1 but not TRAP (P = 0.027 and P = 0.1523, respectively). Etanercept decreased the production of TRAP but not MCP-1 (P < 0.001 and P = 0.84, respectively). In co-cultures of FLSs and PBMCs, 10-NO₂-OA decreased the production of MCP-1 (P < 0.0001). This decrease in MCP-1 production was not seen with etanercept treatment (P = 0.47).

CONCLUSION

10-NO₂-OA decreased the release of MCP-1 in three models of inflammatory arthritis. Of particular interest, 10-NO₂-OA inhibited type I interferon, and 10-NO₂-OA was more effective in reducing MCP-1 production in cultures dominated by FLSs compared with etanercept. Our results encourage clinical investigations of 10-NO₂-OA in patients with inflammatory arthritis.

The Impact of Modern Therapeutic Methods on the Oxidant-Antioxidant Equilibrium and Activities of Selected Lysosomal Enzymes and Serine Protease Inhibitor in Amateur Athletes

Deep electromagnetic stimulation (DEMS) and low-frequency ultrasound (US) are new physical therapy methods used in the rehabilitation of the musculoskeletal system and wound healing. They are applied locally to treat the injured tissues. The beneficial effects of these methods in supportive care have been documented, but accurate biochemical effects are not known. The goal was to assess the effect of single DEMS and US sessions on the oxidant-antioxidant equilibrium, as well as the activities of lysosomal hydrolases and α ₁-antitrypsin (AAT) in peripheral blood of juvenile injured amateur athletes. In the athletes with low back pain (DEMS treated, N = 16) and pain in the shoulder or ankle joint (US treated, N = 14), as well as in healthy control amateur athletes (DEMS treated, N = 14; US treated, N = 17), before the sessions and 30 minutes and 24 hours after them, the levels of the following parameters were determined: thiobarbituric acid reactive substances (TBARS) in erythrocytes and plasma, superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) in erythrocytes, as well as acid phosphatase (AcP), arylsulfatase (ASA), cathepsin D (CTS D), and α ₁-antitrypsin (AAT) in serum. After both procedures, the levels of parameters changed in a negligible manner, excluding the cathepsin D activity, which was statistically significantly lower 30 min and 24 h after US in the control athletes compared to the baseline activity determined directly before the procedure (47.5% and 55.7% differences, respectively). Similar tendency was observed after DEMS (p > 0.05). The procedures, especially low-frequency US, decrease lysosomal proteolytic activity and do not significantly disrupt the oxidant-antioxidant and lysosomal equilibriums in the peripheral blood both of healthy and injured athletes. No systemic acute-phase response of AAT was also detected in the athletes after both procedures. This trial is registered with CTRI/2018/01/011344.

Effect of pre-treatment of strength training and raloxifene in periestropause on bone healing

BACKGROUND

There is evidence that strength training (ST) and raloxifene (Ral) treatment during periestropause promotes better bone quality. We wanted to determine whether the skeletal benefits of ST or Ral treatment, performed during periestropause, would persist after fracture. Therefore, the present study aimed to analyze the influence of pre-treatment with ST and administration of Ral during periestropause on bone healing after total unilateral osteotomy.

METHODS

Senescent female Wistar rats between 18 and 21 months of age, performed ST on a ladder three times per week, were administered Ral by gavage (2.3 mg/kg/day), or an association of both. After 120 days, the treatments were interrupted, and a total osteotomy was performed on the left tibia in all animals. They were euthanized 1 and 8 weeks post-osteotomy.

RESULTS

The administration of Ral during periestropause worsened the biochemical and oxidative profile, decreased gene expression of markers related to bone resorption and remodeling, which negatively affected the physicochemical properties; this lead to changes in the bone callus microarchitecture and mass, as well as a decrease in callus resistance to torsional deformation, resulting in lower tissue quality during bone healing. In contrast, ST performed prior to the osteotomy resulted in better bone healing, improvement of the biochemical and oxidative profile, alteration of the genetic profile in favor of bone formation and resorption, as well as the physic-ochemical properties of the callus. These changes led to better microarchitecture and bone mass and increased callus resistance to torsional deformation, confirming its beneficial effect on the quality of bone tissue, providing acceleration of bone consolidation. The combination of therapies at this exercise intensity and drug dosage showed a negative interaction, where the negative effect of Ral overcame the positive effect of ST, leading to decreased tissue quality in the bone healing process.

CONCLUSIONS

This study indicates that in addition to excellent non-pharmacological therapy and action in the prevention of osteoporosis, ST performed during the aging period may increase bone quality at the onset of healing and provide improved bone consolidation. Furthermore, the anti-osteoclastogenic effect of Ral shown in this model delayed the bone repair process, resulting in considerable clinical concern.

Effects of cachaça, a typical Brazilian alcoholic beverage, on submandibular glands of rats: a histomorphometric and biochemical study

OBJECTIVE

This study aimed to evaluate the effects of chronic consumption of cachaça, a Brazilian beverage containing alcohol, on submandibular glands (SM) of rats by using histomorphometric and biochemical parameters.

MATERIALS AND METHODS

Twenty-four male rats (40 days of age) were assigned into the following four groups (n = 6): two control groups for 75 days (C75) and 105 days (C105), and two experimental groups of cachaça ingestion with ascending concentrations for consecutive 75 days (CA75) and 105 days (CA105). On the right SM glands, the striated, granular and acini ducts were processed for histomorphometric analysis. The left SM glands were weighed and stored at - 80 °C, to evaluate through biochemical tests carried out by spectrophotometric methods, the functional activity of total acid phosphatase (TAP), tartrate-resistant acid phosphatase (TRAP), and alkaline phosphatase (ALP) and to determine the mucin levels.

RESULTS

The absolute and relative weights of the SM glands in both experimental groups were reduced in relation to the controls (p < 0.05). The histomorphometric analysis showed a significant reduction of the acini area (p < 0.05) and non-relevant reduction of striated ducts (p > 0.05). The granular ducts did not show a significant increase of the area (p > 0.05). The TAP and TRAP activities were significantly decreased in the experimental groups (p < 0.05), while the ALP functional activity decreased moderately (p > 0.05). Mucin levels also had a significant reduction when compared with the control groups (p < 0.05).

CONCLUSIONS

Chronic consumption of cachaça can cause morphological changes associated with glandular atrophy, loss of biochemical functionality of phosphatases, and the reduction of mucin synthesis.

CLINICAL RELEVANCE

The consumption of cachaça can compromise the functions of the submandibular glands by altering their morphology and enzymatic activity.

Characterisation of ACP5 missense mutations encoding tartrate-resistant acid phosphatase associated with spondyloenchondrodysplasia

Biallelic mutations in ACP5, encoding tartrate-resistant acid phosphatase (TRACP), have recently been identified to cause the inherited immuno-osseous disorder, spondyloenchondrodysplasia (SPENCD). This study was undertaken to characterize the eight reported missense mutations in ACP5 associated with SPENCD on TRACP expression. ACP5 mutant genes were synthesized, transfected into human embryonic kidney (HEK-293) cells and stably expressing cell lines were established. TRACP expression was assessed by cytochemical and immuno-cytochemical staining with a panel of monoclonal antibodies. Analysis of wild (WT) type and eight mutant stable cell lines indicated that all mutants lacked stainable enzyme activity. All ACP5 mutant constructs were translated into intact proteins by HEK-293 cells. The mutant TRACP proteins displayed variable immune reactivity patterns, and all drastically reduced enzymatic activity, revealing that there is no gross inhibition of TRACP biosynthesis by the mutations. But they likely interfere with folding thereby impairing enzyme function. TRACP exists as two isoforms. TRACP 5a is a less active monomeric enzyme (35kD), with the intact loop peptide and TRACP 5b is proteolytically cleaved highly active enzyme encompassing two subunits (23 kD and 16 kD) held together by disulfide bonds. None of the mutant proteins were proteolytically processed into isoform 5b intracellularly, and only three mutants were secreted in significant amounts into the culture medium as intact isoform 5a-like proteins. Analysis of antibody reactivity patterns revealed that T89I and M264K mutant proteins retained some native conformation, whereas all others were in “denatured” or “unfolded” forms. Western blot analysis with intracellular and secreted TRACP proteins also revealed similar observations indicating that mutant T89I is amply secreted as inactive protein. All mutant proteins were attacked by Endo-H sensitive glycans and none could be activated by proteolytic cleavage in vitro. In conclusion, determining the structure-function relationship of the SPENCD mutations in TRACP will expand our understanding of basic mechanisms underlying immune responsiveness and its involvement in dysregulated bone metabolism.

A Novel Sandwich ELISA for Tartrate-Resistant Acid Phosphatase 5a and 5b Protein Reveals that Both Isoforms are Secreted by Differentiating Osteoclasts and Correlate to the Type I Collagen Degradation Marker CTX-I In Vivo and In Vitro

Tartrate-resistant acid phosphatase type 5 (TRAP) exists as two isoforms, 5a and 5b. 5b is a marker of osteoclast number and 5a of chronic inflammation; however, its association with bone resorption is unknown. In this study, a double-TRAP 5a/5b sandwich ELISA measuring 5a and 5b protein in the same sample was developed. TRAP 5a and 5b protein levels were evaluated as osteoclast differentiation/activity markers in serum and in culture, and their correlation to the resorption marker CTX-I was examined. Serum TRAP 5a and 5b concentrations in healthy men were 4.4 ± 0.6 ng/ml and 1.3 ± 0.2 ng/ml, respectively, and they correlated moderately to each other suggesting that their secretion is coupled under healthy conditions. A correlation was also observed between serum TRAP 5a and 5b with CTX-I, suggesting that both TRAP isoforms associate with osteoclast number. During osteoclast differentiation on plastic/bone, predominantly 5b increased in media/lysate from M-CSF/RANKL-stimulated CD14+ PBMCs. However, substantial levels of 5a were detected at later stages suggesting that both isoforms are secreted from differentiating OCs. More TRAP 5b was released on bone indicating a connection to osteoclast resorptive activity, and a peak in TRAP 5b/5a-ratio coincided with rapid CTX-I release. At the end of the culture period of M-CSF + RANKL-stimulated CD14+ PBMCs, there was a correlation between the secretion of TRAP 5a and 5b proteins with CTX-I. The correlation of not only 5b but also 5a with collagen degradation, both in serum and osteoclast cultures indicates that a considerable proportion of the TRAP 5a originates from osteoclasts and may reflect a hitherto undisclosed regulatory mechanism during bone resorption and bone remodeling.

Cherubism Mice Also Deficient in c-Fos Exhibit Inflammatory Bone Destruction Executed by Macrophages That Express MMP14 Despite the Absence of TRAP+ Osteoclasts

Currently, it is believed that osteoclasts positive for tartrate-resistant acid phosphatase (TRAP+) are the exclusive bone-resorbing cells responsible for focal bone destruction in inflammatory arthritis. Recently, a mouse model of cherubism (Sh3bp2^KI/KI ) with a homozygous gain-of-function mutation in the SH3-domain binding protein 2 (SH3BP2) was shown to develop auto-inflammatory joint destruction. Here, we demonstrate that Sh3bp2^KI/KI mice also deficient in the FBJ osteosarcoma oncogene (c-Fos) still exhibit noticeable bone erosion at the distal tibia even in the absence of osteoclasts at 12 weeks old. Levels of serum collagen I C-terminal telopeptide (ICTP), a marker of bone resorption generated by matrix metalloproteinases (MMPs), were elevated, whereas levels of serum cross-linked C-telopeptide (CTX), another resorption marker produced by cathepsin K, were not increased. Collagenolytic MMP levels were increased in the inflamed joints of the Sh3bp2^KI/KI mice deficient in c-Fos. Resorption pits contained a large number of F4/80+ macrophages and genetic depletion of macrophages rescued these erosive changes. Importantly, administration of NSC405020, an MMP14 inhibitor targeted to the hemopexin (PEX) domain, suppressed bone erosion in c-Fos-deficient Sh3bp2^KI/KI mice. After activation of the NF-κB pathway, macrophage colony-stimulating factor (M-CSF)-dependent macrophages from c-Fos-deficient Sh3bp2^KI/KI mice expressed increased amounts of MMP14 compared with wild-type macrophages. Interestingly, receptor activator of NF-κB ligand (RANKL)-deficient Sh3bp2^KI/KI mice failed to show notable bone erosion, whereas c-Fos deletion did restore bone erosion to the RANKL-deficient Sh3bp2^KI/KI mice, suggesting that osteolytic transformation of macrophages requires both loss-of-function of c-Fos and gain-of-function of SH3BP2 in this model. These data provide the first genetic evidence that cells other than osteoclasts can cause focal bone destruction in inflammatory bone disease and suggest that MMP14 is a key mediator conferring pathological bone-resorbing capacity on c-Fos-deficient Sh3bp2^KI/KI macrophages. In summary, the paradigm that osteoclasts are the exclusive cells executing inflammatory bone destruction may need to be reevaluated based on our findings with c-Fos-deficient cherubism mice lacking osteoclasts. © 2017 American Society for Bone and Mineral Research.

Model of hindlimb unloading in adult female rats: Characterizing bone physicochemical, microstructural, and biomechanical properties

Prolonged bedrest and microgravity induce alterations to bone, leading to bone fragility and compromising the quality of life. In this study, we characterized the physicochemical changes, microstructure, and biomechanics of the femurs of female adult rats in response to hindlimb unloading for 21 days. Twenty 6-month-old Wistar female rats were distributed into control (CON) and hindlimb unloading (HLU) groups. Analysis the in vivo bone mineral density (BMD) by dual energy x-ray absorptiometry (DXA) from the femurs was performed at the beginning and end of the experiment; plasma levels of calcium, phosphorus, and alkaline phosphatase, tartrate-resistant acid phosphatase activity, assessed by spectrophotometry, and estradiol, measured by enzyme-linked immunosorbent assay, was performed after the experiment. We evaluated changes in the trabecular and cortical structure of the femur, after disuse, by micro-computed tomography with high resolution, for analysis of cortical porosity, Raman spectroscopy to measure the amount of physicochemical properties, and the biomechanical test to estimate the changes in biomechanical properties. Our results demonstrated that, after 21 days, HLU animals had decreased femoral BMD, deteriorated bone microarchitecture, particularly in the cortical compartment, with changes in the physicochemical properties and porosity, and reduced deformation capacity of the bone and resistance to the bone stresses. Nevertheless, this study showed the critical role of mechanical stimulation in maintaining the structure of the skeleton in female adults and that disuse, even for a few days, leads to microscopic changes in the structure of the bone matrix, which increases the risk of fracture.

Effects of strength training and raloxifene on femoral neck metabolism and microarchitecture of aging female Wistar rats

The aim of this study was to prevent female osteoporosis using strength training (ST), raloxifene (Ral) or a combination of ST plus Ral during the natural female aging process, specifically in the periestropause period. For a total of 120 days, aging female Wistar rats at 18-21 months of age performed ST on a ladder three times per week, and Ral was administered daily by gavage (1 mg/kg/day). Bone microarchitecture, areal bone mineral density, bone strength of the femoral neck, immunohistochemistry, osteoclast and osteoblast surface were assessed. We found that the treatments modulate the bone remodeling cycle in different ways. Both ST and Ral treatment resulted in improved bone microarchitecture in the femoral neck of rats in late periestropause. However, only ST improved cortical microarchitecture and bone strength in the femoral neck. Thus, we suggest that performing ST during the late period of periestropause is a valid intervention to prevent age-associated osteoporosis in females.

The effects of storage time and temperature on the stability of salivary phosphatases, transaminases and dehydrogenase

OBJECTIVES

To investigate the influence of temperature and storage time on salivary acid phosphatase (ACP), tartrate-resistant acid phosphatase (TRAP), alkaline phosphatase (ALP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and lactate dehydrogenase (LDH).

DESIGN

Unstimulated whole expectorated saliva was collected from healthy men and women subjects (n=26) between 8 and 10a.m. The saliva samples were centrifuged, and the supernatants were measured for ACP, TRAP, ALP, AST, ALT and LDH activities immediately (without freezing) [baseline values] and after time intervals of 3, 7, 14 and 28days (d) of storage at -20°C and -80°C using spectrophotometric methods The influence of storage time was analyzed by one-way ANOVA followed by the Dunnett post-test, while the paired Student's-t-test was used to compare the differences between the temperature (p<0.05).

RESULTS

There was significant decline in the activities of all enzymes at -20°C with increasing storage time. This decrease was relevant from day 14 onward for the majority of the enzymes, with the exception of AST. After day 28, the more sensitive enzymes were ALP and LDH, which showed residual activity of 39% and 16%, respectively, compared with baseline values. There were considerable, but insignificant changes, in the activities of all enzymes after storage at -80°C for 28days.

CONCLUSIONS

Frozen samples should be kept at -80°C to preserve these activities, but there are restrictions for the enzymes ALP, ALT and LDH. Storage of samples at -20°C could introduce high error variance in measured activities.

Carbohydrate Moieties and Cytoenzymatic Characterization of Hemocytes in Whiteleg Shrimp Litopenaeus vannamei

Hemocytes represent one of the most important defense mechanisms against foreign material in Crustacea and are also involved in a variety of other physiological responses. Fluorescent lectin-binding assays and cytochemical reactions were used to identify specificity and distribution of carbohydrate moieties and presence of several hydrolytic enzymes, in hemocytes of whiteleg shrimp Litopenaeus vannamei. Two general classes of circulating hemocytes (granular and agranular) exist in L. vannamei, which express carbohydrates residues for FITC-conjugated lectins WGA, LEA, and PNA; UEA and Con-A were not observed. Enzymatic studies indicated that acid phosphatase, nonspecific esterase, and specific esterases were present; alkaline phosphatase was not observed. The enzymes and carbohydrates are useful tools in hemocyte classification and cellular defense mechanism studies.

Sclerostin antibody prevented progressive bone loss in combined ovariectomized and concurrent functional disuse

Osteoporosis is characterized by low bone mass and compromised trabecular architecture, and is commonly occurred in post-menopausal women with estrogen deficiency. In addition, prolonged mechanical unloading, i.e., long term bed rest, can exaggerate the bone loss. Sclerostin is a Wnt signaling antagonist and acts as a negative regulator for bone formation. A sclerostin-neutralizing antibody (Scl-Ab) increased bone mineral density in women with postmenopausal osteoporosis and healthy men. The objective of this study was to characterize the condition of bone loss in ovariectomized (OVX) rats with concurrent mechanical unloading and evaluate the effect of sclerostin antibody treatment in mitigating the prospective severe bone loss conditions in this model. Four-month-old OVX- or sham-operated female SD rats were used in this study. They were subjected to functional disuse induced by hind-limb suspension (HLS) or free ambulance after 2days of arrival. Subcutaneous injections with either vehicle or Scl-Ab at 25mg/kg were made twice per week for 5weeks from the time of HLS. μCT analyses demonstrated a significant decrease in distal metaphyseal trabecular architecture integrity with HLS, OVX and HLS+OVX (bone volume fraction decreased by 29%, 71% and 87% respectively). The significant improvements of various trabecular bone parameters (bone volume fraction increased by 111%, 229% and 297% respectively as compared with placebo group) with the administration of Scl-Ab are associated with stronger mechanical property and increased bone formation by histomorphometry. These results together indicate that Scl-Ab prevented the loss of trabecular bone mass and cortical bone strength in OVX rat model with concurrent mechanical unloading. The data suggested that monoclonal sclerostin-neutralizing antibody represents a promising therapeutic approach for severe osteoporosis induced by estrogen deficiency with concurrent mechanical unloading.

Effect of Vitamin D on Peripheral Blood Mononuclear Cells from Patients with Psoriasis Vulgaris and Psoriatic Arthritis

Background

Psoriasis, a chronic skin disease with or without joint inflammation, has increased circulating proinflammatory cytokine levels. Vitamin D is involved in calcium homeostasis, bone formation, osteoclastogenesis and osteoclast activity, as well as regulation of immune response. We aimed to study osteoclast differentiation and cytokine secretion of peripheral blood mononuclear cells (PBMCs) from patients with psoriasis vulgaris and psoriatic arthritis, in response to 1,25(OH)₂D₃.

Methods

Serum levels of bone turnover markers were measured by ELISA in patients with psoriasis vulgaris and psoriatic arthritis, and healthy controls. PBMCs were isolated and cultured with or without RANKL/M-CSF and 1,25(OH)₂D₃. Osteoclast differentiation and cytokine secretion were assessed.

Results

Psoriatic arthritis patients had lower osteocalcin, as well as higher C-telopeptide of type I collagen and cathepsin K serum levels compared with psoriasis vulgaris patients and controls. RANKL/M-CSF-stimulated PBMCs from psoriatic arthritis patients produced higher proinflammatory cytokine levels and had a differential secretion profile in response to 1,25(OH)₂D₃, compared with psoriasis vulgaris and control PBMCs.

Conclusions

Our data confirmed altered bone turnover in psoriatic arthritis patients, and demonstrated increased osteoclastogenic potential and proinflammatory cytokine secretion capacity of these PBMCs compared with psoriasis vulgaris and controls. 1,25(OH)₂D₃ abrogated these effects.

Emerging role of alpha-lipoic acid in the prevention and treatment of bone loss

Osteoporosis is a chronic disease associated with decreased bone density that afflicts millions of people worldwide. Current pharmacological treatments are limited, costly, and linked to several negative side effects. These factors are driving current interest in the clinical use of naturally occurring bioactive compounds to mitigate bone loss. Alpha-lipoic acid, a potent antioxidant and essential member of mitochondrial dehydrogenases, has shown considerable promise as an antiosteoclastogenic agent due to its potent reactive oxygen species-scavenging capabilities along with a proven clinical safety record. Collectively, current data indicate that alpha-lipoic acid protects from bone loss via a 2-pronged mechanism involving inhibition of osteoclastogenic reactive oxygen species generation and upregulation of redox gene expression.

Association of Tartrate-Resistant Acid Phosphatase-Expressed Macrophages and Metastatic Breast Cancer Progression

Infiltrating neutrophils, lymphocytes, macrophages, and cytokines constitute a state of chronic inflammation within the tumor microenvironment. Tartrate-resistant acid phosphatase 5a (TRACP5a) protein, a novel product of activated macrophage, is postulated to be a biomarker for systemic inflammatory burden in states of chronic inflammation. We aimed to investigate the clinical significance of TRACP5a expression in tumor-infiltrating macrophages and serum TRACP5a in patients with metastatic breast cancer (BC). We retrospectively analyzed the clinical data from 34 BC patients with confirmed skeletal/visceral metastasis upon or during first-line palliative treatment. Patients were stratified into 3 groups based on the therapeutic responses and follow-up disease course. The association of TRACP5a protein with other inflammatory and cancer biomarkers was assessed among the clinically distinct group of patients. Higher TRACP5a protein was significantly correlated with earlier disease progression and survival (P = 0.0045) in comparison to other inflammatory markers, CRP or IL-6. Patients with higher serum TRACP5a level and shorter survival and treatment refractoriness also had more TRACP+ tumor-infiltrating macrophages. Our data support a hypothesis that serum TRACP5a protein can potentially be a predictive and prognostic marker to evaluate disease progression and therapeutic response in BC patients with bone/visceral metastasis. The associations between overall survival and TRACP expression by macrophages require further prospective investigation.

Paradoxical response to mechanical unloading in bone loss, microarchitecture, and bone turnover markers

BACKGROUND

Sclerostin, encoded by the SOST gene, has been implicated in the response to mechanical loading in bone. Some studies demonstrated that unloading leads to up-regulated SOST expression, which may induce bone loss.

PURPOSE

Most reported studies regarding the changes caused by mechanical unloading were only based on a single site. Considering that the longitudinal bone growth leads to cells of different age with different sensitivity to unloading, we hypothesized that bone turnover in response to unloading is site specific.

METHODS

We established a disuse rat model by sciatic neurectomy in tibia. In various regions at two time-points, we evaluated the bone mass and microarchitecture in surgically-operated rats and control rats by micro-Computed Tomography (micro-CT) and histology, sclerostin/SOST by immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and quantitative reverse transcription polymerase chain reaction (qPCR), tartrate resistant acid phosphatase 5b (TRAP 5b) by ELISA and TRAP staining, and other bone markers by ELISA.

RESULTS

Micro-CT and histological analysis confirmed bone volume in the disuse rats was significantly decreased compared with those in the time-matched control rats, and microarchitecture also changed 2 and 8 weeks after surgery. Compared with the control groups, SOST mRNA expression in the diaphysis was down-regulated at both week 2 and 8. On the contrary, the percentage of sclerostin-positive osteocytes showed an up-regulated response in the 5 - 6 mm region away from the growth plate, while in the 2.5 - 3.5 mm region, the percentage was no significant difference. Nevertheless, in 0.5 - 1.5 mm region, the percentage of sclerostin-positive osteocytes decreased after 8 weeks, consistent with serum SOST level. Besides, the results of TRAP also suggested that the expression in response to unloading may be opposite in different sites or system.

CONCLUSION

Our data indicated that unloading-induced changes in bone turnover are probably site specific. This implies a more complex response pattern to unloading and unpredictable therapeutics which target SOST or TRAP 5b.

Transient Effect of 17β-estradiol on Osteoporosis in Ovariectomized Rats Accompanied with Unilateral Disuse in the Early Phase

PURPOSE

It is clinically important to determine the efficacy of estrogen replacement for postmenopausal women combined with mobility difficulties, due to the potential risks of estradiol. The objective of the current study was to investigate the effect of estradiol replacement on osteoporosis induced by the ovariectomy (OVX) combined with unilateral sciatic neurectomy (SN) in a rat model.

METHOD

Female Sprague-Dawley rats were subjected to OVX and unilateral SN on the right hindlimb (OVX+SN) or sham surgery (CTRL). 17β-estradiol (E2) or vehicle was administrated to the rats immediately, and followed by every other day. Bone mass and trabecular microarchitecture were analyzed using micro-Computed Tomography (micro-CT) and histology at days 3, 7, 14, and 28 post-surgery. The local expressions of sclerostin/SOST, secreted exclusively by osteocytes, and tartrate-resistant acid phosphatase 5b (TRAP 5b), produced mostly by osteoclasts, were examined by immunohistochemistry and TRAP staining, respectively. Serum markers of bone resorption, including C-terminal telopeptides of type I collagen (CTx), receptor activator for nuclear factor κB ligand (RANKL), and TRAP 5b, were quantified by enzyme linked immunosorbent assay (ELISA).

RESULT

Based on micro-CT analysis, E2 treatment of OVX+SN rats improved the preservation of the bone volume fraction (BV/TV) and trabecular number (Tb.N) in the tibias at day 14 post-surgery, which were 43% and 46% higher in OVX+SN+E2 rats than those in OVX+SN rats, respectively. However, the impact of E2 was transient and disappeared at day 28. Expression of sclerostin in the tibias of OVX+SN rats was significantly elevated at day 7 post-surgery compared with the CTRL, but was suppressed until day 14 with E2 replacement.

CONCLUSION

Our results showed that estrogen replacement could transiently protect against bone loss in OVX rats combined with mechanical unloading. The up-regulation of sclerostin expression appears to be transiently delayed by E2 treatment in our models.

Immunohistochemical localization of key arachidonic acid metabolism enzymes during fracture healing in mice

This study investigated the localization of critical enzymes involved in arachidonic acid metabolism during the initial and regenerative phases of mouse femur fracture healing. Previous studies found that loss of cyclooxygenase-2 activity impairs fracture healing while loss of 5-lipoxygenase activity accelerates healing. These diametric results show that arachidonic acid metabolism has an essential function during fracture healing. To better understand the function of arachidonic acid metabolism during fracture healing, expression of cyclooxygenase-1 (COX-1), cyclooxygenase -2 (COX-2), 5-lipoxygenase (5-LO), and leukotriene A4 hydrolase (LTA4H) was localized by immunohistochemistry in time-staged fracture callus specimens. All four enzymes were detected in leukocytes present in the bone marrow and attending inflammatory response that accompanied the fracture. In the tissues surrounding the fracture site, the proportion of leukocytes expressing COX-1, COX-2, or LTA4H decreased while those expressing 5-LO remained high at 4 and 7 days after fracture. This may indicate an inflammation resolution function for 5-LO during fracture healing. Only COX-1 was consistently detected in fracture callus osteoblasts during the later stages of healing (day 14 after fracture). In contrast, callus chondrocytes expressed all four enzymes, though 5-LO appeared to be preferentially expressed in newly differentiated chondrocytes. Most interestingly, osteoclasts consistently and strongly expressed COX-2. In addition to bone surfaces and the growth plate, COX-2 expressing osteoclasts were localized at the chondro-osseous junction of the fracture callus. These observations suggest that arachidonic acid mediated signaling from callus chondrocytes or from callus osteoclasts at the chondro-osseous junction regulate fracture healing.

A molecular description of acid phosphatase

Acid phosphatase is ubiquitous in distribution in various organisms. Although it catalyzes simple hydrolytic reactions, it is considered as an interesting enzyme in biological systems due to its involvement in different physiological activities. However, earlier reviews on acid phosphatase reveal some fragmentary information and do not give a holistic view on this enzyme. So, the present review summarizes studies on biochemical properties, structure, catalytic mechanism, and applications of acid phosphatase. Recent advancement of acid phosphatase in agricultural and clinical fields is emphasized where it is presented as potent agent for sustainable agricultural practices and diagnostic marker in bone metabolic disorders. Also, its significance in prostate cancer therapies as a therapeutic target has been discussed. At the end, current studies and prospects of immobilized acid phosphatase are included.

Nano-osteoimmunology as an important consideration in the design of future implants

The size of wear particles emanating from a prosthesis at interfaces is critical to the interfacial properties of the joint replacement and responses from the biological environment. Nanoscale particles in particular require investigation. This project aimed to evaluate the osteoimmunological response to nanoscale ultrahigh molecular weight polyethylene (UHMWPE) wear particles in vitro, including dendritic cells (DCs), macrophages, osteoclasts (OCs), cytokine secretion, and co-cultured OCs and osteoblasts (OBs). The wear particles generated from a constant-load knee prosthesis actuator were profiled using atomic force microscopy and fractionated into sizes of 0.05-0.2, 0.2-0.8, 0.8-1, 1-5 and 5-10 μm. The fractions were exposed to DCs isolated from mice spleen, human OCs, and co-cultured human OBs and OCs, and the effects of the particles on the cells were determined. Results revealed that exposure to nanoscale UHMWPE wear particles induced significant DC activation (p<0.05) and consequently increased cytokine interleukin (IL)-6 and IL-1β secretion (p<0.05). Exposure to nanoscale particles promoted OC maturation, resulting in the suppression of OB proliferation in OB and OC co-cultures. Therefore, the results of this study could contribute to a more mechanistic understanding of wear-debris-associated prosthesis failure. Furthermore, nanoscale UHMWPE wear particles should be considered as mediators of periprosthetic inflammation in the future development of biomaterials for joint replacement bearing surfaces.

Serum tartrate-resistant acid phosphatase isoform 5a (TRACP5a) as a potential risk marker in cardiovascular disease

OBJECTIVE

This study was undertaken to determine the association between serum tartrate-resistant acid phosphatase 5a (TRACP5a) and cardiovascular disease (CVD) risk.

METHODS

Four hundred patients were enrolled including, 291 asymptomatic subjects grouped by the number of traditional risk factors, 36 patients undergoing cardiac arteriography, 34 undergoing percutaneous cardiac intervention, and 39 with acute myocardial infarction. Serum was collected at baseline and, in arteriograpy and intervention groups, periodically for 1 week afterward. In addition to laboratory and clinical evaluation for risk assessment, serum TRACP5a, C-reactive protein (CRP) and interleukin-6 (IL-6) were determined.

RESULTS

All biomarkers rose with increasing CVD risk. Only serum TRACP5a, logCRP and cholesterol were elevated in symptomatic patients. Serum TRACP5a was higher in men and correlated with age, logCRP, logIL-6 and log-triglycerides, and in symptomatic patients, with the number of diseased coronary arteries. IL-6 and CRP showed acute phase responses, whereas TRACP5a did not change over 1 week after arteriography or intervention. After adjustment for all other variables and risk factors, TRACP5a and logCRP were the only biomarkers to associate with symptomatic disease. TRACP5a was more specific than CRP to predict myocardial infarction among all subjects.

CONCLUSIONS

Serum TRACP5a is a macrophage-derived inflammation marker associated with CVD risk, and with coronary vessel disease and its severity and may be a useful marker for screening and assessment of CVD risk.

Differential expression of tartrate-resistant acid phosphatase isoforms 5a and 5b by tumor and stromal cells in human metastatic bone disease

Tartrate-resistant acid phosphatase (TRAP) exists in human serum as two major isoforms, monomeric 5a and proteolytically processed enzymatically active 5b. The 5b isoform is secreted by osteoclasts and has recently been advocated as a serum marker for bone metastasis in breast cancer patients. The 5a isoform, on the other hand, is not bone-derived and has been proposed to be a marker of activated macrophages and chronic inflammation. In this study, expression of TRAP protein and enzymatic activity in bone metastases from different primary sites was examined. TRAP activity was high in bone metastases from prostate cancer, intermediate in breast cancer, and low in lung and kidney cancers. The partially purified TRAP from breast cancer bone metastasis samples exhibited the enzymatic characteristics of purple acid phosphatase. Both 5a and 5b isoforms were expressed in bone metastases of different histogenetic origins, i.e. prostate, breast, lung and kidney, and also a novel previously unreported 42 kDa variant of the TRAP 5a isoform was identified in bone metastases. This novel TRAP 5a isoform was absent in human bone, indicating that the 42 kDa variant is specific to metastatic cancer tissue. Immunohistochemistry revealed that metastatic cancer cells were the predominant source of TRAP 5a, whereas tumor-associated macrophages and occasionally multinucleated giant cells in the tumor stroma preferentially expressed the proteolytically processed TRAP 5b variant. Our results indicate the presence of a previously unstudied variant of monomeric TRAP 5a in cancer cells, which may have functional and diagnostic implications. Moreover, the presence of TRAP-positive macrophages in bone metastases could, together with cancer cells and osteoclasts, contribute to the elevated levels of serum TRAP activity observed in patients with bone metastases.

The cathepsin K inhibitor AAE581 induces morphological changes in osteoclasts of treated patients

Inhibitors of Cathepsin K (Cat-K) are recognized as an interesting way to inhibit osteoclast (OC) activity. OCs from patients treated with the anticathepsin-K inhibitor AAE581 (balicatib) were found enlarged. They contained numerous vacuoles filled with tartrate resistant acid phosphatase (TRAcP), an intracellular enzyme that terminates the degradation of collagen internalized in OC transcytotic vesicles. In a phase 2 clinical study, 675 patients with postmenopausal osteoporosis received the Cat-K inhibitor AAE581 at 0, 5, 10, 25, or 50 mg/D during 1 year. Eleven patients had a transiliac bone biopsy, studied undecalcified. Histoenzymatic detection of TRAcP was used to identify and count OC number. The histomorphometrist was not aware of the randomization of patients at the time of analysis. OC were unstained in one patient because of a failure in the fixation protocol, but easily observable in the 10 remaining patients. Whatever the received dose, treated patients exhibited a characteristic aspect of the OC cytoplasm which appeared filled of deeply-stained brown vacuoles, making cells looking like bunches of grape. These round vacuoles, evidenced on TRAcP-stained sections, were due to the accumulation of intracytoplasmic TRAcP. This led to a moderate enlargement of the OC size when compared to a series of control osteoporotic patients. AAE581 did not induce OC apoptosis at any dosage but it modified OC morphology. Cat-K inhibition (inhibiting the extracellular collagen breakdown) is associated with a compensatory accumulation of intracellular TRAcP that could not be used to complete protein degradation. TRAcP is also known to be degraded by Cat-K.

Genome-wide expression analyses establish dendritic cells as a new osteoclast precursor able to generate bone-resorbing cells more efficiently than monocytes

Dendritic cells (DCs), mononuclear cells that initiate immune responses, and osteoclasts (OCs), multinucleated bone-resorbing cells, are hematopoietic cells derived from monocytic precursor cells. Using in vitro generated dendritic cells, we previously showed that human and murine DCs could transdifferentiate into resorbing osteoclasts in the presence of macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-kappaB ligand (RANKL). In this study we globally compared by transcriptomic profiling this new osteoclast differentiation pathway from DCs with the canonical differentiation pathway from monocytes. DNA chip data revealed that starting from two very distinct cell types, treatment with M-CSF and RANKL generated two highly similar types of osteoclast. In particular, DC-derived osteoclasts expressed all the characteristic marker genes of monocyte-derived osteoclasts. Two major molecular events could be observed during osteoclastogenesis: downregulation of a large set of monocyte or DC specific markers, together with upregulation of characteristic osteoclast marker genes. Most interestingly, our transcriptomic data showed a closer molecular profile between DCs and OCs than between monocytes and OCs. Our data establish DCs as a new osteoclast precursor able to generate OCs more efficiently than monocytes.

Effects of exercise on insulin sensitivity, inflammatory cytokines, and serum tartrate-resistant acid phosphatase 5a in obese Chinese male adolescents

The benefits of exercise on glucose metabolism, inflammation, and serum tartrate-resistant acid phosphatase 5a (TRACP 5a) protein levels in Chinese male adolescents have not been extensively analyzed. Therefore, we examined the effects of a 12-week exercise program on weight, adiposity, insulin sensitivity (IS), and inflammatory marker expression, including the novel macrophage marker TRACP 5a, in obese Chinese male adolescents. A total of 106 male adolescents were recruited from the Army Academy in Taiwan and classified as lean (body mass index [BMI], 20.9 +/- 0.2 kg/m(2)) or obese (BMI, 27.7 +/- 0.2 kg/m(2)). Body composition, IS, and inflammatory markers were measured in both groups at baseline and in the obese group after completion of a 12-week exercise program. Body weight, BMI, waist circumference, body fat mass and percentage, homeostasis model assessment for insulin resistance, fasting plasma glucose, fasting serum insulin, 2-hour postchallenge plasma glucose concentration, interleukin-6, C-reactive protein, and serum TRACP 5a were significantly higher in the obese group as compared with the lean group. In addition, serum TRACP 5a was positively correlated with body mass and fat indices. After completion of the exercise program, significant reductions in all anthropometric, metabolic, and inflammatory indicators, with the exception of serum TRACP 5a were observed. Although the obese participants remained obese, exercise training significantly improved IS and reduced interleukin-6 and C-reactive protein. Tartrate-resistant acid phosphatase 5a remained unaffected by exercise training, consistent with our hypothesis that it is associated with increased adipose tissue in obese individuals.

Biology and clinical significance of tartrate-resistant acid phosphatases: new perspectives on an old enzyme

Type 5 tartrate-resistant acid phosphatase (TRAP) has been a clinically relevant biomarker for about 50 years. It has always been a reliable and specific cytochemical marker for hairy cell leukemia and for differentiated cells of monocytic lineage. Only recently has the test for serum TRAP activity been accepted as sensitive and specific enough for clinical use as a marker of osteoclasts and bone resorption. This has come about through steady advances in knowledge about TRAP enzymology, structure, function, and molecular regulation and a consequent appreciation that TRAP isoforms 5a and 5b have very different clinical significance. As a measure of osteoclast number and bone resorption, TRAP 5b has diagnostic and prognostic applications in osteoporosis, cancers with bone metastasis, chronic renal failure, and perhaps other metabolic and pathologic bone diseases. Serum TRAP 5a, on the other hand, has no relationship to bone metabolism but seems instead to be a measure of activated macrophages and chronic inflammation. Exploration of the real clinical usefulness of serum TRAP 5a for diagnosis and disease management in a wide variety of chronic inflammatory diseases is only now beginning. This perspective traces the important basic scientific developments that have led up to the refinement of serum TRAP isoform immunoassays and their validation as biomarkers of disease. Many unanswered questions remain, providing a wealth of opportunity for continued research of this multifaceted enzyme.

Complex regulation of tartrate-resistant acid phosphatase (TRAP) expression by interleukin 4 (IL-4): IL-4 indirectly suppresses receptor activator of NF-kappaB ligand (RANKL)-mediated TRAP expression but modestly induces its expression directly

Interleukin 4 (IL-4) inhibits receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast formation and functional activity in a STAT6-dependent manner. IL-4 down-regulates expression of tartrate-resistant acid phosphatase (TRAP) in mature osteoclasts. To determine whether IL-4 regulates TRAP promoter activity, RAW264.7 cells were transfected with a TRAP promoter-luciferase reporter. Treatment with IL-4 alone modestly enhanced TRAP luciferase activity. However, IL-4 suppressed the ability of RANKL to up-regulate TRAP-luciferase activity, suggesting that IL-4 has multiple effects on TRAP transcription. IL-4 also reduced the RANKL-induced association of RNA polymerase II with the TRAP gene in osteoclasts. The TRAP promoter contains a STAT6-binding motif, and STAT6 bound to the endogenous TRAP promoter after IL-4 treatment. To determine the impact of STAT6 binding, we transfected cells with STAT6VT, a constitutively active STAT6 mutant. STAT6VT alone up-regulated TRAP-luciferase activity; this effect was abrogated by mutating the STAT6 binding site in the minimal TRAP promoter. STAT6VT did not inhibit the potent up-regulation of TRAP promoter activity caused by overexpression of NFATc1, PU.1, and microphthalmia transcription factor, downstream targets of macrophage colony-stimulating factor and RANKL. IL-4 down-regulated the expression of c-Fos and NFATc1 in mature osteoclasts. Knockdown of NFATc1 by short interfering RNA caused TRAP expression to be down-regulated, and ectopic expression of NFATc1 abrogated the IL-4-induced down-regulation of TRAP. These results suggest that STAT6 plays two distinct roles in TRAP expression. The IL-4-induced activation of STAT6 mediates suppression of the RANKL-induced TRAP promoter activity indirectly by inhibiting NFATc1 expression. However, in the absence of RANKL and osteoclast differentiation, STAT6 binds the TRAP promoter after IL-4 treatment and directly enhances TRAP expression.

Administration of high-dose macrophage colony-stimulating factor increases bone turnover and trabecular volume fraction

Macrophage colony-stimulating factor (M-CSF) is a hematopoietic growth factor that plays a critical role in early osteoclastogenesis. To characterize the skeletal effects of M-CSF, we administered soluble M-CSF to mice. It was hypothesized that M-CSF would stimulate bone formation through coupled activity of osteoclasts and osteoblasts. Twenty-four male C57BL/6 J mice (n = 12/group, aged 7 weeks) received subcutaneous injections of human M-CSF [5 mg/(kg day)] or inert vehicle (VEH) for 21 days. M-CSF increased serum bone turnover markers (+57% TRAP-5b and +44% osteocalcin). Microcomputed tomography revealed an anabolic effect on tibial trabecular bone, with higher bone volume fraction (+35%), connectivity density (+79%), and number (+18%), as well as lower trabecular separation (-18%). M-CSF had no significant effect on cortical bone mineral content, geometry, or strength. There was no change in quantitative histomorphometry parameters of femoral cortical bone. These results reveal the complex, site-specific effects of M-CSF. In particular, we have demonstrated an anabolic effect of M-CSF on trabecular bone achieved through coupled activation of osteoblasts. However, in contrast to previous studies, M-CSF was found to have no effect on cortical bone. M-CSF was demonstrated to significantly influence both bone modeling and remodeling in relatively young animals.

Biomarkers for osteoporosis management: utility in diagnosis, fracture risk prediction and therapy monitoring

Osteoporosis is a systemic disease characterized by low bone mass and microarchitectural deterioration of bone tissue, resulting in an increased risk of fracture. While the level of bone mass can be estimated by measuring bone mineral density (BMD) using dual X-ray absorptiometry (DXA), its measurement does not capture all the risk factors for fracture. Quantitative changes in skeletal turnover can be assessed easily and non-invasively by the measurement of serum and urinary biochemical markers; the most sensitive markers include serum osteocalcin, bone specific alkaline phosphatase, the N-terminal propeptide of type I collagen for bone formation, and the crosslinked C- (CTX) and N- (NTX) telopeptides of type I collagen for bone resorption. Advances in our knowledge of bone matrix biochemistry, most notably of post-translational modifications in type I collagen, are likely to lead to the development of new biochemical markers that reflect changes in the material property of bone, an important determinant of bone strength. Among those, the measurement of the urinary ratio of native (alpha) to isomerized (beta) CTX - an index of bone matrix maturation - has been shown to be predictive of fracture risk independently of BMD and bone turnover. In postmenopausal osteoporosis, levels of bone resorption markers above the upper limit of the premenopausal range are associated with an increased risk of hip, vertebral, and nonvertebral fracture, independent of BMD. Therefore, the combined use of BMD measurement and biochemical markers is helpful in risk assessment, especially in those women who are not identified as at risk by BMD measurement alone. Levels of bone markers decrease rapidly with antiresorptive therapies, and the levels reached after 3-6 months of therapy have been shown to be more strongly associated with fracture outcome than changes in BMD. Preliminary studies indicate that monitoring changes of bone formation markers could also be useful to monitor anabolic therapies, including intermittent parathyroid hormone administration and, possibly, to improve adherence to treatment. Thus, repeated measurements of bone markers during therapy may help improve the management of osteoporosis in patients.

Significance of serum TRACP in rheumatoid arthritis

Human serum contains two related isoforms of TRACP: TRACP 5a and TRACP 5b. Serum TRACP 5a protein is increased in about one third of rheumatoid arthritis (RA) sera. This study was undertaken to examine the significance of serum TRACP isoforms 5a and 5b as disease markers of inflammation and bone destruction in RA. One hundred eighteen patients were recruited including 50 with RA (25 with nodules), 26 with osteoarthritis (OA), and 42 with other rheumatic diseases. Twenty-six healthy adults served as controls. Serum TRACP 5a activity, TRACP 5a protein, and TRACP 5b activity were determined by in-house immunoassays. C-reactive protein (CRP) was determined by in-house immunoassay using commercial antibodies and CRP. Other commercial markers included bone-specific alkaline phosphatase (BALP), C-telopeptides of type-I collagen (ICTP), cartilage glycoprotein-39 (YKL-40), and IgM rheumatoid factors (IgM-RF). Mean TRACP 5a protein was significantly elevated only in RA compared with healthy controls and other disease groups. TRACP 5a protein correlated significantly only with IgM-RF in RA. Among RA patients, mean TRACP 5a protein and IgM RF were significantly higher in nodule formers. In contrast, TRACP 5b activity was slightly elevated in RA and correlated with BALP, ICTP, and YKL-40 but not with IgM-RF or CRP. Mean TRACP 5b activity was no different in RA patients with or without nodules. TRACP isoforms could be useful disease markers in RA; TRACP 5a protein may be a measure of systemic inflammatory macrophage burden and disease severity. TRACP 5b activity is a marker for osteoclast number and perhaps local or systemic bone destruction.

Monomeric tartrate resistant acid phosphatase induces insulin sensitive obesity

BACKGROUND

Obesity is associated with macrophage infiltration of adipose tissue, which may link adipose inflammation to insulin resistance. However, the impact of inflammatory cells in the pathophysiology of obesity remains unclear. Tartrate resistant acid phosphatase (TRAP) is an enzyme expressed by subsets of macrophages and osteoclasts that exists either as an enzymatically inactive monomer or as an active, proteolytically processed dimer.

PRINCIPAL FINDINGS

Using mice over expressing TRAP, we show that over-expression of monomeric, but not the dimeric form in adipose tissue leads to early onset spontaneous hyperplastic obesity i.e. many small fat cells. In vitro, recombinant monomeric, but not proteolytically processed TRAP induced proliferation and differentiation of mouse and human adipocyte precursor cells. In humans, monomeric TRAP was highly expressed in the adipose tissue of obese individuals. In both the mouse model and in the obese humans the source of TRAP in adipose tissue was macrophages. In addition, the obese TRAP over expressing mice exhibited signs of a low-grade inflammatory reaction in adipose tissue without evidence of abnormal adipocyte lipolysis, lipogenesis or insulin sensitivity.

CONCLUSION

Monomeric TRAP, most likely secreted from adipose tissue macrophages, induces hyperplastic obesity with normal adipocyte lipid metabolism and insulin sensitivity.

Secreted tartrate-resistant acid phosphatase 5b is a Marker of osteoclast number in human osteoclast cultures and the rat ovariectomy model

PURPOSE

To study the effects of estrogen withdrawal on osteoclast number and osteoclast activity in the rat ovariectomy (OVX) model.

METHODS

We first cultured human CD34+ osteoclast precursor cells on bovine bone slices, allowing them to differentiate into mature resorbing osteoclasts. Secreted tartrate-resistant acid phosphatase 5b (TRACP 5b) and C-terminal cross-linked telopeptides of type I collagen (CTX) were determined from the culture medium. TRACP 5b correlated strongly with osteoclast number and CTX with osteoclast activity, facilitating their subsequent use in the rat OVX model. An 8 week OVX study was then performed including sham-operated rats receiving vehicle, OVX rats receiving vehicle, and OVX rats receiving 10 microg/kg/day 17 beta-estradiol (E2). Trabecular bone parameters were determined from the tibial metaphysis using peripheral quantitative computed tomography and histomorphometry. Osteoclast number was normalized with bone perimeter (N.Oc/B.Pm) and tissue area (N.Oc/T.Ar, indicating absolute number of osteoclasts). TRACP 5b and CTX were determined from fasting serum samples.

RESULTS

Trabecular bone parameters indicated substantial bone loss after OVX that was prevented by E2. N.Oc/B.Pm increased after OVX, while N.Oc/T.Ar and TRACP 5b decreased, and TRACP 5b correlated strongly with N.Oc/T.Ar. However, CTX values increased after OVX, and the "resorption index" CTX/TRACP 5b showed more substantial changes than either CTX or TRACP 5b alone.

CONCLUSION

These results show that TRACP 5b is a reliable marker of osteoclast number, and the index CTX/TRACP 5b is a useful parameter in rat OVX model. The high elevation of CTX/TRACP 5b values by OVX demonstrates that estrogen withdrawal generates high activity of osteoclasts in the rat OVX model.

Expression of immune response genes in the stifle joint of dogs with oligoarthritis and degenerative cranial cruciate ligament rupture

Dysregulation of immune responses within joints plays an important role in development of inflammatory arthritis. We determined expression of a panel of immune response and matrix turnover genes in synovial fluid collected from a group of dogs with stifle oligoarthritis and associated degenerative cranial cruciate ligament (CCL) rupture (n=27). We also studied synovial fluid gene expression in dogs affected with other forms of degenerative arthritis (n=9) and in the stifle joint of healthy dogs with intact CCL (n=14). After collection, synovial cells were pelleted and RNA was isolated. Relative expression of cathepsin K, cathepsin S, tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), invariant chain (li), toll-like receptor-2 (TLR-2), and TLR-9 was determined using real-time quantitative RT-PCR. Data were normalized to peripheral blood mononuclear cells (PBMC) as an internal control. Relative expression of cathepsin K, MMP-9, TRAP, and li was increased in the stifle synovial fluid of dogs with oligoarthritis, when compared with the stifles of healthy dogs (P<0.05). In contrast, relative expression of all of the genes-of-interest in synovial fluid from joints affected with other forms of arthritis was not significantly different from the stifles of healthy dogs. TRAP expression was also significantly increased in the stifle joints of dogs with oligoarthritis, when compared to joint expression of TRAP in dogs with other forms of degenerative arthritis (P<0.05). In the dogs with stifle oligoarthritis, expression of both matrix turnover and immune response genes was increased in stifle synovial fluid, when compared with the internal PBMC control, whereas in healthy dogs and dogs with other forms of arthritis, only expression of matrix turnover genes was increased in synovial fluid, when compared with the internal PBMC control (P<0.05). Taken together, these findings suggest that antigen-specific immune responses within the stifle joint may be involved in the pathogenesis of persistent synovitis and associated joint degradation in dogs with oligoarthritis and degenerative CCL rupture.

Expression and proteolytic processing of mammalian purple acid phosphatase in CHO-K1 cells

Rat recombinant purple acid phosphatase (PAP) stably expressed in fibroblast-like CHO-K1 cells was purified and characterized with respect to post-translational modifications such as N-glycosylation and proteolytic processing in order to elucidate subcellular and molecular pathways for proteolytic activation. In these cells, proteolytically processed PAP was more abundant than the monomeric form. PAP-transfected CHO-K1 cells were expressing active cathepsin K intracellularly, which was partially co-localized with PAP. However, neither cathepsin K nor trypsin digestion of the purified monomeric PAP in vitro did result in a two-subunit form with kinetic and electrophoretic properties resembling the endogenous cellular two-subunit form. Treatment of PAP-transfected CHO-K1 cells with the cysteine proteinase inhibitor E-64 suggested that only a minor fraction of secreted PAP is processed intracellularly by cysteine proteinases. These data do not support a dominant or critical role for cathepsins or trypsin-like serine proteinases in the proteolytic activation of PAP in CHO-K1 cells, implicating yet unidentified proteinases in the proteolytic processing of both intracellular and secreted PAP in this cell line.

Increased tartrate-resistant acid phosphatase (TRAP) expression in malignant breast, ovarian and melanoma tissue: an investigational study

Background

Tartrate-resistant acid phosphatase (TRAP) is a metalloprotein enzyme that belongs to the acid phosphatases and is known to be expressed by osteoclasts. It has already been investigated as a marker of bone metastases in cancer patients. In this study, which examined the value of serum TRAP concentrations as a marker of bone disease in breast cancer patients, we observed high concentrations of TRAP even in patients without bone metastases. To elucidate this phenomenon, we examined the expression of TRAP in breast cancer cells and the cells of several other malignancies.

Methods

TRAP concentrations in the serum of tumor patients were determined by ELISA. The expression of TRAP in breast, ovarian, and cervical cancer and malignant melanoma was analyzed by immunohistochemistry. RT-PCR and immunocytology were used to evaluate TRAP expression in cultured tumor cells.

Results

A marked increase in serum TRAP concentrations was observed in patients with breast and ovarian cancer, regardless of the presence or absence of bone disease. TRAP expression was found in breast and ovarian cancers and malignant melanoma, while cervical cancer showed only minimal expression of TRAP. Expression of TRAP was absent in benign tissue or was much less marked than in the corresponding malignant tissue. TRAP expression was also demonstrated in cultured primary cancer cells and in commercially available cell lines.

Conclusion

Overexpression of TRAP was detected in the cells of various different tumors. TRAP might be useful as a marker of progression of malignant disease. It could also be a potential target for future cancer therapies.

Effects of proteolysis and reduction on phosphatase and ROS-generating activity of human tartrate-resistant acid phosphatase

Osteoclasts and macrophages express high amounts of tartrate-resistant acid phosphatase (TRACP), an enzyme with unknown biological function. TRACP contains a disulfide bond, a protease-sensitive loop peptide, and a redox-active iron that can catalyze formation of reactive oxygen species (ROS). We studied the effects of proteolytic cleavage by trypsin, reduction of the disulfide bond by beta-mercaptoethanol, and reduction of the redox-active iron by ascorbate on the phosphatase and ROS-generating activity of baculovirus-generated recombinant human TRACP. Ascorbate alone and trypsin in combination with beta-mercaptoethanol increased k(cat)/K(m) of the phosphatase activity seven- to ninefold. The pH-optimum was changed from 5.4-5.6 to 6.2-6.4 by ascorbate and trypsin cleavage. Trypsin cleavage increased k(cat)/K(m) of the ROS-generating activity 2.5-fold without affecting the pH-optimum (7.0). These results suggest that the protease-sensitive loop peptide, redox-active iron, and disulfide bond are important regulatory sites in TRACP, and that the phosphatase and ROS-generating activity are performed with different reaction mechanisms.

Development of immunoassays for serum tartrate-resistant acid phosphatase isoform 5a

BACKGROUND

Serum tartrate-resistant acid phosphatase (TRACP) consists of 2 structurally related isoforms, TRACP 5a and 5b. TRACP 5b is from bone-resorbing osteoclasts. TRACP 5a may be a macrophage product of inflammation. We used a novel antibody to TRACP 5a to standardize immunoassays for serum TRACP 5a activity and protein.

METHODS

Biotinylated anti-TRACP antibodies were used to immobilize serum TRACP isoforms. TRACP activity was measured using 4-nitrophenyl phosphate as substrate. TRACP 5a protein was measured with an independent peroxidase-conjugated anti-TRACP antibody. Immunoassays were standardized for linearity of serum dose response, sensitivity and precision. Reference ranges for TRACP 5a were established from serum of 50 healthy males and 50 healthy age-matched females. Serum TRACP 5a activity and protein were determined in 29 cases of rheumatoid arthritis.

RESULTS

Serum matrix interference in both TRACP 5a assays required dilution to 10% serum to approach linearity. Intra-assay and inter-assay CV% were <10%. Mean serum TRACP 5a activity and protein were significantly higher in healthy men than women. There was a slight, but significant age related increase in both serum TRACP 5a and 5b among females, but not males, from age 20 to 70 years. TRACP 5a activity was positively correlated to TRACP 5a protein in healthy sera. Neither TRACP 5a activity nor protein was correlated strongly to TRACP-5b activity. TRACP 5a protein was significantly increased in 8/29 RA sera, whereas TRACP 5a and 5b activities were not. TRACP 5a activity and protein were not significantly correlated in RA sera.

CONCLUSIONS

Although TRACP 5a and 5b are related biosynthetically, their circulating levels in healthy humans were independent, suggesting differential regulation of expression. In chronic diseases, increased TRACP 5a may represent pathological processes of inflammation unrelated to bone metabolism.

Proteolytic Excision of a Repressive Loop Domain in Tartrate-resistant Acid Phosphatase by Cathepsin K in Osteoclasts

Tartrate-resistant acid phosphatase (TRAP) is a metallophosphoesterase participating in osteoclast-mediated bone turnover. Activation of TRAP is associated with the redox state of the di-iron metal center as well as with limited proteolytic cleavage in an exposed loop domain. The cysteine proteinases cathepsin B, L, K, and S as well as the matrix metalloproteinase-2, -9, -13, and -14 are expressed by osteoclasts and/or other bone cells and have been implicated in the turnover of bone and cartilage. To identify proteases that could act as activators of TRAP in bone, we report here that cathepsins K and L, in contrast to the matrix metalloproteinases, efficiently cleaved and activated recombinant TRAP in vitro. Activation of TRAP by cathepsin K/L was because of increases in catalytic activity, substrate affinity, and sensitivity to reductants. Processing by cathepsin K occurred sequentially by an initial excision of the loop peptide Gly(143)-Gly(160) followed by the removal of a Val(161)-Ala(162) dipeptide at the N terminus of the C-terminal 16-kDa TRAP subunit. Cathepsin L initially released a shorter Gln(151)-Gly(160) peptide and completed processing at Ser(145) or Gly(143) at the C terminus of the N-terminal 23-kDa TRAP subunit and at Arg(163) at the N terminus of the C-terminal 16-kDa TRAP subunit. Mutation of Ser(145) to Ala partly mimicked the effect of proteolysis on catalytic activity, identifying Ser(145) as well as Asp(146) (Funhoff, E. G., Ljusberg, J., Wang, Y., Andersson, G., and Averill, B. A. (2001) Biochemistry 40, 11614-11622) as repressive amino acids of the loop region to maintain the TRAP enzyme in a catalytically latent state. The C-terminal sequence of TRAP isolated from rat bone was consistent with cathepsin K-mediated processing in vivo. Moreover, cathepsin K, but not cathepsin L, co-localized with TRAP in osteoclast-resorptive compartments, supporting a role for cathepsin K in the extracellular processing of monomeric TRAP in the resorption lacuna.