The thiocarbamate disulphide drug, disulfiram induces osteopenia in rats by inhibition of osteoblast function due to suppression of acetaldehyde dehydrogenase activity

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

A cautionary note on the use of N-acetylcysteine as a reactive oxygen species antagonist to assess copper mediated cell death

A new form of cell death has recently been proposed involving copper-induced cell death, termed cuproptosis. This new form of cell death has been widely studied in relation to a novel class of copper ionophores, including elesclomol and disulfiram. However, the exact mechanism leading to cell death remains contentious. The oldest and most widely accepted biological mechanism is that the accumulated intracellular copper leads to excessive build-up of reactive oxygen species and that this is what ultimately leads to cell death. Most of this evidence is largely based on studies using N-acetylcysteine (NAC), an antioxidant, to relieve the oxidative stress and prevent cell death. However, here we have demonstrated using inductively coupled mass-spectrometry, that NAC pretreatment significantly reduces intracellular copper uptake triggered by the ionophores, elesclomol and disulfiram, suggesting that reduction in copper uptake, rather than the antioxidant activity of NAC, is responsible for the diminished cell death. We present further data showing that key mediators of reactive oxygen species are not upregulated in response to elesclomol treatment, and further that sensitivity of cancer cell lines to reactive oxygen species does not correlate with sensitivity to these copper ionophores. Our findings are in line with several recent studies proposing the mechanism of cuproptosis is instead via copper mediated aggregation of proteins, resulting in proteotoxic stress leading to cell death. Overall, it is vital to disseminate this key piece of information regarding NAC's activity on copper uptake since new research attributing the effect of NAC on copper ionophore activity to quenching of reactive oxygen species is being published regularly and our studies suggest their conclusions may be misleading.

Sesamol improves bone mass in ovary intact growing and adult rats but accelerates bone deterioration in the ovariectomized rats

Sesamol, an active component in sesame seeds, is known for its health benefits. However, its effect on bone metabolism remains unexplored. The present study aims to investigate the effect of sesamol on growing, adult and osteoporotic skeleton and its mechanism of action. Sesamol at various doses were administered orally to growing, ovariectomized, and ovary-intact rats. Alterations in bone parameters were examined using micro-CT and histological studies. Western blot and mRNA expression from long bones were performed. We further evaluated the effect of sesamol on osteoblast and osteoclast function and its mode of action in the cell culture system. These data showed that sesamol was able to promote peak bone mass in growing rats. However, sesamol had the opposite effect in ovariectomized rats, evident from gross deterioration of trabecular and cortical microarchitecture. Concurrently, it improved the bone mass in adult rats. In vitro results revealed that sesamol enhances the bone formation by stimulating osteoblast differentiation through MAPK, AKT, and BMP-2 signaling. In contrast, it enhances osteoclast differentiation and expression of osteoclast-specific genes in osteoclast differentiation medium. Interestingly, in presence of estrogen, the effect reversed and sesamol decreased osteoclast differentiation, in vitro. Sesamol improves bone microarchitecture in growing and ovary-intact rats, whereas it enhances the bone deterioration in ovariectomized rats. While sesamol promotes bone formation, its opposing effect on the skeleton can be attributed to its dual effect on osteoclastogenesis in presence and absence of estrogen. These findings in the preclinical context suggests a special attention towards the detrimental effect of sesamol in postmenopausal women.

Gene Therapy to Treat Osteopenia Associated With Chronic Ethanol Consumption and Aldehyde Dehydrogenase 2 Deficiency

Aldehyde dehydrogenase 2 (ALDH2) deficiency affects 35% to 45% of East Asians and 8% of the world population. ALDH2 is the second enzyme in the ethanol metabolism pathway. The common genetic variant ALDH2*2 allele has a glutamic acid-to-lysine substitution at position 487 (E487K) that reduces the enzyme activity, resulting in an accumulation of acetaldehyde after ethanol consumption. The ALDH2*2 allele is associated with increased risk of osteoporosis and hip fracture. Our prior study showed that administration of an adeno-associated virus (AAV) serotype rh.10 gene transfer vector expressing the human ALDH2 cDNA (AAVrh.10hALDH2) before initiation of ethanol consumption prevented bone loss in ALDH2-deficient homozygous knockin mice carrying the E487K mutation (Aldh2 E487K+/+). We hypothesized that AAVrh.10hALDH2 administration after establishment of osteopenia would be able to reverse bone loss due to ALDH2 deficiency and chronic ethanol consumption. To test this hypothesis, male and female Aldh2 E487K+/+ mice (n = 6) were given ethanol in the drinking water for 6 weeks to establish osteopenia and then administered AAVrh.10hALDH2 (1011 genome copies). Mice were evaluated for an additional 12 weeks. AAVrh.10hALDH2 administration after osteopenia was established corrected weight loss and locomotion phenotypes and, importantly, increased midshaft femur cortical bone thickness, the most important component of bone in the resistance to fractures, and showed a trend toward increased trabecular bone volume. AAVrh.10hALDH2 is a promising therapeutic for osteoporosis in ALDH2-deficient individuals. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Protective effect of rutin against thiram-induced cytotoxicity and oxidative damage in human erythrocytes

Thiram is a fungicide that is used to prevent fungal diseases in seeds and crops and also as an animal repellent. The pro-oxidant activity of thiram is well established. Rutin is a flavonoid glycoside present in many fruits and plants and has several beneficial properties, including antioxidant effects. We have previously shown that thiram causes oxidative damage in human erythrocytes. The present study was designed to evaluate the protective effect of rutin against thiram-induced damage in human erythrocytes. Treatment of erythrocytes with 0.5 mM thiram for 4 h increased the level of oxidative stress markers, decreased antioxidant power and lowered the activity of antioxidant and membrane bound enzymes. It also enhanced the generation of reactive oxygen and nitrogen species (ROS and RNS) and altered the morphology of erythrocytes. However, prior treatment of erythrocytes with rutin (0.5, 1 and 2 mM) for 2 h, followed by 4 h incubation with 0.5 mM thiram, led to a decrease in the level of oxidative stress markers in a rutin concentration-dependent manner. A significant restoration in the antioxidant power and activity of antioxidant enzymes was observed upon the treatment of erythrocytes with 1 and 2 mM rutin. Pre-incubation with rutin lowered the generation of ROS and RNS which will reduce oxidative damage in erythrocytes. The thiram-induced changes in cell morphology and activity of membrane-bound enzymes were also attenuated by rutin. These results suggest that rutin can be used to mitigate thiram-induced oxidative damage in human erythrocytes.

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

Thiram exposure in environment: A critical review on cytotoxicity

Thiram is used in large quantities in agriculture and may contaminate the environment by improper handling or storage in chemical plants and warehouses. A review of the literature has shown that thiram can affect different organs in animals and its toxic mechanisms can be elucidated in more detail at molecular level. We have summarized several impacts of thiram on animals: the effects of the perspectives of oxidative stress, mitochondrial damage, autophagy, apoptosis, and the IHH/PTHrP pathway on regulating abnormal skeletal development in particular tibial dyschondroplasia and kyphosis; angiogenesis inhibition was investigated from the perspective of angiogenesis factor inhibition, PI3K/AKT signaling pathway and CD147; the inhibition effect of thiram on fibroblasts and erythrocytes via the perspective of oxidative stress, mitochondrial damage and inhibition of growth factors in animal skin fibroblasts and erythrocytes; studied fertilized egg size, reduced fertility, neurodegeneration, and immune damage from the perspectives of CYP51 inhibition and dopamine-b-hydroxylase inhibition in the reproductive system, vitamin D deficiency in the nervous system, and inflammatory damage in the immune system; embryonic dysplasia in terms of thyroid hormone repression in animal embryonic development and repression of the SOX9a transcription factor. The elucidation of the mechanisms of toxicity of thiram on various organs of animals at molecular level will enable a more detailed understanding of the mechanisms of toxicity of thiram in animals and will facilitate the exploration of the treatment of thiram poisoning at molecular level.

Aldehyde Dehydrogenase 2 as a Therapeutic Target in Oxidative Stress-Related Diseases: Post-Translational Modifications Deserve More Attention

Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.

Diosmin, a citrus fruit-derived phlebotonic bioflavonoid protects rats from chronic kidney disease-induced loss of bone mass and strength without deteriorating renal function

Kidney Disease: Improving Global Outcomes (KDIGO) 2017 Clinical Practice Guideline recommended treatment decisions for patients with chronic kidney disease (CKD) with osteoporosis and/or high risk of fracture. Bisphosphonates, the first-line...

Oral administration of thiram inhibits brush border membrane enzymes, oxidizes proteins and thiols, impairs redox system and causes histological changes in rat intestine: A dose dependent study

Pesticides are extensively employed worldwide, especially in agriculture to control weeds, insect infestation and diseases. Besides their targets, pesticides can also affect the health of non-target organisms, including humans The present study was conducted to study the effect of oral exposure of thiram, a dithiocarbamate fungicide, on the intestine of rats. Male rats were administered thiram at doses of 100, 250, 500 and 750 mg/kg body weight for 4 days. This treatment reduced cellular glutathione, total sulfhydryl groups but enhanced protein carbonyl content and hydrogen peroxide levels. In addition, the activities of all major antioxidant enzymes (catalase, thioredoxin reductase, glutathione peroxidase and glutathione-S-transferase) except superoxide dismutase were decreased. The antioxidant power of the intestine was impaired lowering the metal-reducing and free radical quenching ability. Administration of thiram also led to inhibition of intestinal brush border membrane enzymes, alkaline phosphatase, γ-glutamyl transferase, leucine aminopeptidase and sucrase. Activities of enzymes of pentose phosphate pathway, citric acid cycle, glycolysis and gluconeogenesis were also inhibited. Histopathology showed extensive damage in the intestine of thiram-treated rats at higher doses. All the observed effects were in a thiram dose-dependent manner. The results of this study show that thiram causes significant oxidative damage in the rat intestine which is associated with the marked impairment in the antioxidant defense system.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Increased Bone Marrow-Specific Adipogenesis by Clofazimine Causes Impaired Fracture Healing, Osteopenia, and Osteonecrosis Without Extraskeletal Effects in Rats

Mycobacterium leprae infection causes bone lesions and osteoporosis, however, the effect of antileprosy drugs on the bone is unknown. We, therefore, set out to address it by investigating osteogenic differentiation from bone marrow (BM)-derived mesenchymal stem cells (MSCs). Out of 7 antileprosy drugs, only clofazimine (CFZ) reduced MSCs viability (IC50 ∼ 1 μM) and their osteogenic differentiation but increased adipogenic differentiation on a par with rosiglitazone, and this effect was blocked by a peroxisome proliferator-activated receptor gamma antagonist, GW9662. CFZ also decreased osteoblast viability and resulted in impaired bone regeneration in a rat femur osteotomy model at one-third human drug dose owing to increased callus adipogenesis as GW9662 prevented this effect. CFZ treatment decreased BM MSC population and homing of MSC to osteotomy site despite drug levels in BM being much less than its in vitro IC50 value. In adult rats, CFZ caused osteopenia in long bones marked by suppressed osteoblast function due to enhanced adipogenesis and increased osteoclast functions. A robust increase in marrow adipose tissue (MAT) by CFZ did not alter the hematologic parameters but likely reduced BM vascular bed leading to osteonecrosis (ON) characterized by empty osteocyte lacunae. However, CFZ had no effect on visceral fat content and was not associated with any metabolic and hematologic changes. Levels of unsaturated fatty acids in MAT were higher than saturated fatty acids and CFZ further increased the former. From these data, we conclude that CFZ has adverse skeletal effects and could be used for creating a rodent ON model devoid of extraskeletal effects.

Regulation of Myelination by Exosome Associated Retinoic Acid Release from NG2-Positive Cells

In the CNS, oligodendrocytes are responsible for myelin formation and maintenance. Following spinal cord injury, oligodendrocyte loss and an inhibitory milieu compromise remyelination and recovery. Here, we explored the role of retinoic acid receptor-beta (RARβ) signaling in remyelination. Using a male Sprague Dawley rat model of PNS-CNS injury, we show that oral treatment with a novel drug like RARβ agonist, C286, induces neuronal expression of the proteoglycan decorin and promotes myelination and differentiation of oligodendrocyte precursor cells (NG2⁺ cells) in a decorin-mediated neuron–glia cross talk. Decorin promoted the activation of RARα in NG2⁺ cells by increasing the availability of the endogenous ligand RA. NG2⁺ cells synthesize RA, which is released in association with exosomes. We found that decorin prevents this secretion through regulation of the EGFR–calcium pathway. Using functional and pharmacological studies, we further show that RARα signaling is both required and sufficient for oligodendrocyte differentiation. These findings illustrate that RARβ and RARα are important regulators of oligodendrocyte differentiation, providing new targets for myelination.

SIGNIFICANCE STATEMENT This study identifies novel therapeutic targets for remyelination after PNS-CNS injury. Pharmacological and knock-down experiments show that the retinoic acid (RA) signaling promotes differentiation of oligodendrocyte precursor cells (OPCs) and remyelination in a cross talk between neuronal RA receptor-beta (RARβ) and RARα in NG2⁺ cells. We show that stimulation of RARα is required for the differentiation of OPCs and we describe for the first time how oral treatment with a RARβ agonist (C286, currently being tested in a Phase 1 trial, ISRCTN12424734) leads to the endogenous synthesis of RA through retinaldehyde dehydrogenase 2 (Raldh2) in NG2 cells and controls exosome-associated-RA intracellular levels through a decorin–Ca²⁺ pathway. Although RARβ has been implicated in distinct aspects of CNS regeneration, this study identifies a novel function for both RARβ and RARα in remyelination.

The case for thyroid disruption in early life stage exposures to thiram in zebrafish (Danio rerio)

Thiram, a pesticide in the dithiocarbamate chemical family, is widely used to prevent fungal disease in seeds and crops. Its off-site movement to surface waters occurs and may place aquatic organisms at potential harm. Zebrafish embryos were used for investigation of acute (1 h) thiram exposure (0.001-10 µM) at various developmental stages. Survival decreased at 1 µM and 10 µM and hatching was delayed at 0.1 µM and 1 µM. Notochord curvatures were seen at 0.1 and 1 μM thiram when exposure was initiated at 2 and at 10 hpf. Similar notochord curvatures followed exposure to the known TPO inhibitor, methimazole (MMI). Changes were absent in embryos exposed at later stages, i.e., 12 hpf. In embryos exposed to 0.1 or 1 μM at 10 hpf, levels of the thyroid enzyme, Deiodinase 3, increased by 12 hpf. Thyroid peroxide (TPO), important in T4 synthesis, decreased by 48 hpf in embryos exposed to 1 µM at 10 hpf. Thiram toxicity was stage-dependent and early life stage exposure may be responsible for adverse effects seen later. These effects may be due to impacts on the thyroid via regulation of specific thyroid genes including TPO and Deiodinase 3.

An Fe3O4@SiO2/Schiff base/Cu(ii) complex as an efficient recyclable magnetic nanocatalyst for selective mono N-arylation of primary O-alkyl thiocarbamates and primary O-alkyl carbamates with aryl halides and arylboronic acids

A convenient and efficient selective mono N-arylation of primary O-alkyl thiocarbamates and carbamates is reported by a recyclable magnetic Cu(ii) nanocatalyst.

Lipid Peroxidation-Derived Aldehydes, 4-Hydroxynonenal and Malondialdehyde in Aging-Related Disorders

Among the various mechanisms involved in aging, it was proposed long ago that a prominent role is played by oxidative stress. A major way by which the latter can provoke structural damage to biological macromolecules, such as DNA, lipids, and proteins, is by fueling the peroxidation of membrane lipids, leading to the production of several reactive aldehydes. Lipid peroxidation-derived aldehydes can not only modify biological macromolecules, by forming covalent electrophilic addition products with them, but also act as second messengers of oxidative stress, having relatively extended lifespans. Their effects might be further enhanced with aging, as their concentrations in cells and biological fluids increase with age. Since the involvement and the role of lipid peroxidation-derived aldehydes, particularly of 4-hydroxynonenal (HNE), in neurodegenerations, inflammation, and cancer, has been discussed in several excellent recent reviews, in the present one we focus on the involvement of reactive aldehydes in other age-related disorders: osteopenia, sarcopenia, immunosenescence and myelodysplastic syndromes. In these aging-related disorders, characterized by increases of oxidative stress, both HNE and malondialdehyde (MDA) play important pathogenic roles. These aldehydes, and HNE in particular, can form adducts with circulating or cellular proteins of critical functional importance, such as the proteins involved in apoptosis in muscle cells, thus leading to their functional decay and acceleration of their molecular turnover and functionality. We suggest that a major fraction of the toxic effects observed in age-related disorders could depend on the formation of aldehyde-protein adducts. New redox proteomic approaches, pinpointing the modifications of distinct cell proteins by the aldehydes generated in the course of oxidative stress, should be extended to these age-associated disorders, to pave the way to targeted therapeutic strategies, aiming to alleviate the burden of morbidity and mortality associated with these disturbances.

Guava fruit extract and its triterpene constituents have osteoanabolic effect: Stimulation of osteoblast differentiation by activation of mitochondrial respiration via the Wnt/β-catenin signaling

The aim of this study was to evaluate the skeletal effect of guava triterpene-enriched extract (GE) in rats and identify osteogenic compounds thereof, and determine their modes of action. In growing female rats, GE at 250 mg/kg dose increased parameters of peak bone mass including femur length, bone mineral density (BMD) and biomechanical strength, suggesting that GE promoted modeling-directed bone growth. GE also stimulated bone regeneration at the site of bone injury. In adult osteopenic rats (osteopenia induced by ovariectomy, OVX) GE completely restored the lost bones at both axial and appendicular sites, suggesting a strong osteoanabolic effect. Serum metabolomics studies showed changes in several metabolites (some of which are related to bone metabolism) in OVX compared with ovary-intact control and GE treatment to OVX rats reversed those. Out of six abundantly present triterpenes in GE, ursolic acid (UA) and 2α-hydroxy ursolic acid (2α-UA) induced osteogenic differentiation in vitro as did GE by activating Wnt/β-catenin pathway assessed by phosphorylation of GSK-3β. Over-expressing of constitutively active GSK-3β (caGSK-3β) in osteoblasts abolished the differentiation-promoting effect of GE, UA and 2α-UA. All three increased both glycolysis and mitochondrial respiration but only rotenone (inhibitor of mitochondrial electron transfer) and not 2-deoxyglucose (to block glycolysis) inhibited osteoblast differentiation. In addition, caGSK-3β over-expression attenuated the enhanced mitochondrial respiration caused by GE, UA and 2α-UA. We conclude that GE has osteoanabolic effect which is contributed by UA and 2α-UA, and involve activation of canonical Wnt signaling which in turn modulates cellular energy metabolism leading to osteoblast differentiation.

Theophylline, a methylxanthine drug induces osteopenia and alters calciotropic hormones, and prophylactic vitamin D treatment protects against these changes in rats

The drug, theophylline is frequently used as an additive to medications for people suffering from chronic obstructive pulmonary diseases (COPD). We studied the effect of theophylline in bone cells, skeleton and parameters related to systemic calcium homeostasis. Theophylline induced osteoblast apoptosis by increasing reactive oxygen species production that was caused by increased cAMP production. Bone marrow levels of theophylline were higher than its serum levels, indicating skeletal accumulation of this drug. When adult Sprague-Dawley rats were treated with theophylline, bone regeneration at fracture site was diminished compared with control. Theophylline treatment resulted in a time-dependent (at 4- and 8 weeks) bone loss. At 8 weeks, a significant loss of bone mass and deterioration of microarchitecture occurred and the severity was comparable to methylprednisone. Theophylline caused formation of hypomineralized osteoid and increased osteoclast number and surface. Serum bone resorption and formation marker were respectively higher and lower in the theophylline group compared with control. Bone strength was reduced by theophylline treatment. After 8 weeks, serum 25-D3 and liver 25-hydroxylases were decreased in theophylline group than control. Further, theophylline treatment reduced serum 1, 25-(OH)2 vitamin D3 (1,25-D3), and increased parathyroid hormone and fibroblast growth factor-23. Theophylline treated rats had normal serum calcium and phosphate but displayed calciuria and phosphaturia. Co-administration of 25-D3 with theophylline completely abrogated theophylline-induced osteopenia and alterations in calcium homeostasis. In addition, 1,25-D3 protected osteoblasts from theophylline-induced apoptosis and the attendant oxidative stress. We conclude that theophylline has detrimental effects in bone and prophylactic vitamin D supplementation to subjects taking theophylline could be osteoprotective.

Disulfiram attenuates osteoclast differentiation in vitro: a potential antiresorptive agent

Disulfiram (DSF), a cysteine modifying compound, has long been clinically employed for the treatment of alcohol addiction. Mechanistically, DSF acts as a modulator of MAPK and NF-κB pathways signaling pathways. While these pathways are crucial for osteoclast (OC) differentiation, the potential influence of DSF on OC formation and function has not been directly assessed. Here, we explore the pharmacological effects of DSF on OC differentiation, activity and the modulation of osteoclastogenic signaling cascades. We first analyzed cytotoxicity of DSF on bone marrow monocytes isolated from C57BL/6J mice. Upon the establishment of optimal dosage, we conducted osteoclastogenesis and bone resorption assays in the presence or absence of DSF treatment. Luciferase assays in RAW264.7 cells were used to examine the effects of DSF on major transcription factors activation. Western blot, reverse transcription polymerase chain reaction, intracellular acidification and proton influx assays were employed to further dissect the underlying mechanism. DSF treatment dose-dependently inhibited both mouse and human osteoclastogenesis, especially at early stages of differentiation. This inhibition correlated with a decrease in the expression of key osteoclastic marker genes including CtsK, TRAP, DC-STAMP and Atp6v0d2 as well as a reduction in bone resorption in vitro. Suppression of OC differentiation was found to be due, at least in part, to the blockade of several key receptor activators of nuclear factor kappa-B ligand (RANKL)-signaling pathways including ERK, NF-κB and NFATc1. On the other hand, DSF failed to suppress intracellular acidification and proton influx in mouse and human osteoclasts using acridine orange quenching and microsome-based proton transport assays. Our findings indicate that DSF attenuates OC differentiation via the collective suppression of several key RANKL-mediated signaling cascades, thus making it an attractive agent for the treatment of OC-mediated disorders.