Glucocorticoid-Induced Osteoporosis

Diagnosis and therapeutic approach to bone health in patients with hypopituitarism

The results of many studies in recent years indicate a significant impact of pituitary function on bone health. The proper function of the pituitary gland has a significant impact on the growth of the skeleton and the appearance of sexual dimorphism. It is also responsible for achieving peak bone mass, which protects against the development of osteoporosis and fractures later in life. It is also liable for the proper remodeling of the skeleton, which is a physiological mechanism managing the proper mechanical resistance of bones and the possibility of its regeneration after injuries. Pituitary diseases causing hypofunction and deficiency of tropic hormones, and thus deficiency of key hormones of effector organs, have a negative impact on the skeleton, resulting in reduced bone mass and susceptibility to pathological fractures. The early appearance of pituitary dysfunction, i.e. in the pre-pubertal period, is responsible for failure to achieve peak bone mass, and thus the risk of developing osteoporosis in later years. This argues for the need for a thorough assessment of patients with hypopituitarism, not only in terms of metabolic disorders, but also in terms of bone disorders. Early and properly performed treatment may prevent patients from developing the bone complications that are so common in this pathology. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary disease.

Reactive Oxygen Species-Responsive Dual Anti-Inflammatory and Antioxidative Nanoparticles for Anterior Uveitis

Anterior uveitis (AU) is an immune-mediated inflammatory disease that results in iritis, cyclitis, glaucoma, cataracts, and even a loss of vision. The frequent and long-term administration of corticosteroid drugs is limited in the clinic owing to the side effects and patient noncompliance with the drugs. Therefore, specifically delivering drugs to inflammatory anterior segment tissues and reducing the topical application dosage of the drug are still a challenge. Here, we developed dual dexamethasone (Dex) and curcumin (Cur)-loaded reactive oxygen species (ROS)-responsive nanoparticles (CPDC NPs) to treat anterior uveitis. The CPDC NPs demonstrated both anti-inflammatory and antioxidative effects, owing to their therapeutic characteristics of dexamethasone and curcumin, respectively. The CPDC NPs could effectively release dexamethasone and curcumin in the oxidizing physiological environment of the inflammation tissue. The CPDC NPs can effectively internalize by activated macrophage cells, subsequently suppressing the proinflammatory factor expression. Moreover, the CPDC NPs can inhibit ROS and inflammation via nuclear transcription factor E2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway activation. In an endotoxin-induced uveitis rabbit model, the CPDC NPs show a therapeutic effect that is better than that of either free drugs or commercial eye drops. Importantly, the CPDC NPs with a lower dexamethasone dosage could reduce the side effects significantly. Taken together, we believe that the dual-drug-loaded ROS-responsive NPs could effectively target and inhibit inflammation and have the potential for anterior uveitis treatment in clinical practice.

Association between alcohol intake and bone mineral density: results from the NHANES 2005-2020 and two-sample Mendelian randomization

We used the data from the NHANES cross-sectional study among 14,113 participants and indicated a positive correlation between alcohol intake frequency and bone mineral density in different body sites. Mendelian randomization was conducted, and no causal relationship is significant between these two variables. The study can provide some suggestions on the daily consumption of alcohol for osteoporosis patients.

PURPOSE

The effect of alcohol intake on bone mineral density (BMD) remains unclear. This study explored the association and causality between alcohol intake and BMD.

METHODS

Based on the 2005-2020 National Health and Nutrition Examination Survey including 14,113 participants, we conducted co-variate-adjusted multilinear regression analyses to explore the association between alcohol intake levels and spine or femur BMD. To evaluate the causal association between alcohol intake frequency and bone mineral density, the inverse variance weighted approach of two-sample Mendelian randomization (MR) was used with genetic data from the Medical Research Council Integrative Epidemiology Unit (462,346 cases) for alcohol intake frequency and the Genetic Factors for Osteoporosis Consortium (28,496 cases) for lumbar spine and femur neck BMD (32,735 cases).

RESULTS

Compared with non-drinkers, total femur BMDs but not total spine BMD increased with daily alcohol intake in males (β = 3.63*10-2 for mild drinkers, β = 4.21*10-2 for moderate drinkers, and β = 4.26*10-2 for heavy drinkers). By contrast, the higher total spine BMD in females was related to higher alcohol intake levels (β = 2.15*10-2 for mild drinkers, β = 2.59*10-2 for moderate drinkers, and β = 3.88*10-2 for heavy drinkers). Regarding the two-sample MR results, no causal relationship was observed between alcohol intake frequency and lumbar spine BMD (odds ratio [OR] = 1.016, P = 0.789) or femur neck BMD (OR = 1.048, P = 0.333).

CONCLUSION

This study suggests a positive association between alcohol intake frequency and BMD, although the causal relationship was not significant.

Insights into the antiosteoporotic mechanism of the soy-derived isoflavone genistein: Modulation of the Wnt/beta-catenin signaling

Bone remodeling is a process that involves osteoblasts, osteoclasts, and osteocytes, and different intracellular signaling, such as the canonical Wnt/β-catenin pathway. Dysregulations of this pathway may also occur during secondary osteoporosis, as in the case of glucocorticoid-induced osteoporosis (GIO), which accelerates osteoblast and osteocyte apoptosis by reducing bone formation, osteoblast differentiation and function, accelerates in turn osteoblast, and osteocyte apoptosis. Genistein is a soy-derived nutrient belonging to the class of isoflavones that reduces bone loss in osteopenic menopausal women, inhibiting bone resorption; however, genistein may also favor bone formation. The aim of this study was to investigate whether estrogen receptor stimulation by genistein might promote osteoblast and osteocyte function during glucocorticoid challenge. Primary osteoblasts, collected from C57BL6/J mice, and MLO-A5 osteocyte cell line were used to reproduce an in vitro model of GIO by adding dexamethasone (1 μM) for 24 h. Cells were then treated with genistein for 24 h and quantitative Polymerase Chain Reaction (qPCR) and western blot were performed to study whether genistein activated the Wnt/β-catenin pathway. Dexamethasone challenge reduced bone formation in primary osteoblasts and bone mineralization in osteocytes; moreover, canonical Wnt/β-catenin pathway was reduced following incubation with dexamethasone in both osteoblasts and osteocytes. Genistein reverted these changes and this effect was mediated by both estrogen receptors α and β. These data suggest that genistein could induce bone remodeling through Wnt/β-catenin pathway activation.

The multi-faceted nature of age-associated osteoporosis

Age-associated osteoporosis (AAOP) poses a significant health burden, characterized by increased fracture risk due to declining bone mass and strength. Effective prevention and early treatment strategies are crucial to mitigate the disease burden and the associated healthcare costs. Current therapeutic approaches effectively target the individual contributing factors to AAOP. Nonetheless, the management of AAOP is complicated by the multitude of variables that affect its development. Main intrinsic and extrinsic factors contributing to AAOP risk are reviewed here, including mechanical unloading, nutrient deficiency, hormonal disbalance, disrupted metabolism, cognitive decline, inflammation and circadian disruption. Furthermore, it is discussed how these can be targeted for prevention and treatment. Although valuable as individual targets for intervention, the interconnectedness of these risk factors result in a unique etiology for every patient. Acknowledgement of the multifaceted nature of AAOP will enable the development of more effective and sustainable management strategies, based on a holistic, patient-centered approach.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.

Unveiling the hidden impact: Subclinical hypercortisolism and its subtle influence on bone health

In recent years, advancements in imaging technologies have led to an increased detection rate of adrenal incidentalomas (AI), with age demonstrating a significant correlation with their incidence. Among the various forms of functional adrenal incidentalomas, subclinical hypercortisolism (SH) stands out as a predominant subtype. Despite the absence of typical symptoms associated with Cushing's syndrome, both domestic and international research consistently establishes a robust link between SH and diverse metabolic irregularities, including hypertension, lipid metabolism disorders, glucose metabolism abnormalities, and disruptions in bone metabolism. Individuals with SH face an elevated risk of cardiovascular events and mortality, highlighting the clinical significance of addressing this condition. Prolonged exposure to elevated cortisol levels poses a significant threat to bone health, contributing to bone loss, alterations in bone microstructure, and an increased susceptibility to fractures. However, comprehensive reviews addressing bone metabolism changes and associated mechanisms in SH patients are currently lacking. Furthermore, the profound impact of concurrent SH on the overall health of the elderly cannot be overstated. A comprehensive understanding of the skeletal health status in elderly individuals with concomitant SH is imperative. This article aims to fill this gap by offering a detailed review of bone metabolism changes and associated mechanisms in SH patients arising from AI. Additionally, it provides a forward-looking perspective on research concerning skeletal health in elderly individuals with concurrent SH.

Morroniside-mediated mitigation of stem cell and endothelial cell dysfunction for the therapy of glucocorticoid-induced osteonecrosis of the femoral head

BACKGROUND

Prolonged use of glucocorticoids (GCs) potentially lead to a condition known as GCs-induced osteonecrosis of the femoral head (GIONFH). The primary mechanisms underlying this phenomenon lies in stem cells and endothelial cells dysfunctions. Morroniside, an iridoid glycoside sourced from Cornus officinalis, possesses numerous biological capabilities, including combating oxidative stress, preventing apoptosis, opposing ischemic effects, and promoting the regeneration of bone tissue.

PURPOSE

This study aimed to analyze the impact of Morroniside on Dexamethasone (DEX)-induced dysfunction in stem cells and endothelial cells, and its potential as a therapeutic agent for GIONFH in rat models.

METHODS

ROS assay, JC-1 assay, and TUNEL assay were used to detect oxidative stress and apoptosis levels in vitro. For the evaluation of the osteogenic capability of bone marrow-derived mesenchymal stem cells, we employed ALP and ARS staining. Additionally, the angiogenic ability of endothelial cells was assessed using tube formation assay and migration assay. Microcomputed tomography analysis, hematoxylin-eosin staining, and immunohistochemical staining were utilized to evaluate the in vivo therapeutic efficacy of Morroniside.

RESULTS

Morroniside mitigates DEX-induced excessive ROS expression and cell apoptosis, effectively reducing oxidative stress and alleviating cell death. In terms of osteogenesis, Morroniside reverses DEX-induced osteogenic impairment, as evidenced by enhanced ALP and ARS staining, as well as increased osteogenic protein expression. In angiogenesis, Morroniside counteracts DEX-induced vascular dysfunction, demonstrated by an increase in tube-like structures in tube formation assays, a rise in the number of migrating cells, and elevated levels of angiogenic proteins. In vivo, our results further indicate that Morroniside alleviates the progression of GIONFH.

CONCLUSION

The experimental findings suggest that Morroniside concurrently mitigates stem cell and endothelial cell dysfunction through the PI3K/AKT signaling pathway both in vitro and in vivo. These outcomes suggest that Morroniside serves as a potential therapeutic agent for GIONFH.

Treating the Side Effects of Exogenous Glucocorticoids; Can We Separate the Good From the Bad?

It is estimated that 2% to 3% of the population are currently prescribed systemic or topical glucocorticoid treatment. The potent anti-inflammatory action of glucocorticoids to deliver therapeutic benefit is not in doubt. However, the side effects associated with their use, including central weight gain, hypertension, insulin resistance, type 2 diabetes (T2D), and osteoporosis, often collectively termed iatrogenic Cushing's syndrome, are associated with a significant health and economic burden. The precise cellular mechanisms underpinning the differential action of glucocorticoids to drive the desirable and undesirable effects are still not completely understood. Faced with the unmet clinical need to limit glucocorticoid-induced adverse effects alongside ensuring the preservation of anti-inflammatory actions, several strategies have been pursued. The coprescription of existing licensed drugs to treat incident adverse effects can be effective, but data examining the prevention of adverse effects are limited. Novel selective glucocorticoid receptor agonists and selective glucocorticoid receptor modulators have been designed that aim to specifically and selectively activate anti-inflammatory responses based upon their interaction with the glucocorticoid receptor. Several of these compounds are currently in clinical trials to evaluate their efficacy. More recently, strategies exploiting tissue-specific glucocorticoid metabolism through the isoforms of 11β-hydroxysteroid dehydrogenase has shown early potential, although data from clinical trials are limited. The aim of any treatment is to maximize benefit while minimizing risk, and within this review we define the adverse effect profile associated with glucocorticoid use and evaluate current and developing strategies that aim to limit side effects but preserve desirable therapeutic efficacy.

Enhancing Osteoporosis Treatment through Targeted Nanoparticle Delivery of Risedronate: In Vivo Evaluation and Bioavailability Enhancement

Risedronate-loaded mPEG-coated hydroxyapatite, thiolated chitosan-based (coated) and non-coated nanoparticles were tested for their potential effects in the treatment of osteoporosis. The prepared nanoparticles were evaluated for their bone-targeting potential by inducing osteoporosis in female Wistar rats via oral administration of Dexona (dexamethasone sodium phosphate). In vivo pharmacokinetic and pharmacodynamic studies were performed on osteoporotic rat models treated with different formulations. The osteoporotic model treated with the prepared nanoparticles indicated a significant effect on bone. The relative bioavailability was enhanced for RIS-HA-TCS-mPEG nanoparticles given orally compared to RIS-HA-TCS, marketed, and API suspension. Biochemical investigations also showed a significant change in biomarker levels, ultimately leading to bone formation/resorption. Micro-CT analysis of bone samples also demonstrated that the RIS-HA-TCS-mPEG-treated group showed the best results compared to other treatment groups. Moreover, the histology of bone treated with RIS-HA-TCS-mPEG showed a marked restoration of the architecture of trabecular bone along with a well-connected bone matrix and narrow inter-trabecular spaces compared to the toxic group. A stability analysis was also carried out according to ICH guidelines (Q1AR2), and it was found that RIS-HA-TCS-mPEG was more stable than RIS-HA-TCS at 25 °C. Thus, the results of present study indicated that mPEG-RIS-HA-TCS has excellent potential for sustained delivery of RIS for the treatment and prevention of osteoporosis, and for minimizing the adverse effects of RIS typically induced via oral administration.

Osteoporosis and risk of fracture in heart transplant patients

Introduction

Significant bone loss occurs after heart transplantation, predominantly in the first year, with increased risk of incident fractures. The goal of this study was to evaluate the prevalence of fragility fractures in a population of heart transplantation patients and to identify the independent risk factors for fractures.

Methods

This was a prospective monocentric study that included patients with heart transplantation occurring < 10 years who were undergoing heart transplantation monitoring. All patients underwent bone mineral density evaluation by dual-energy X-ray absorptiometry and radiographies to establish the presence of vertebral fractures.

Results

We included 79 patients (61 men); the mean age was 56.8 ± 10.8 years. The mean time between transplantation and inclusion was 32.3 ± 35.0 months. Incident fractures were diagnosed in 21 (27%) patients after heart transplantation. Vertebral fractures were the most frequent (30 vertebral fractures for 15 patients). Osteoporosis was confirmed in 22 (28%) patients. Mean bone mineral density at the femoral neck and total hip was lower with than without fracture (femoral neck: 0.777 ± 0.125 vs 0.892 ± 0.174 g/cm2, p<0.01; total hip: 0.892 ± 0.165 vs 0.748 ± 0.07 g/cm2, p<0.001), with a significant result on multivariate analysis. The mean time from transplantation to the first fracture was 8.0 ± 7.6 months.

Discussion

Our study confirmed a high vertebral fracture risk in heart transplant patients, especially during the first year after transplantation.

Bone and the Unfolded Protein Response: In Sickness and in Health

Differentiation and optimal function of osteoblasts and osteoclasts are contingent on synthesis and maintenance of a healthy proteome. Impaired and/or altered secretory capacity of these skeletal cells is a primary driver of most skeletal diseases. The endoplasmic reticulum (ER) orchestrates the folding and maturation of membrane as well as secreted proteins at high rates within a calcium rich and oxidative organellar niche. Three ER membrane proteins monitor fidelity of protein processing in the ER and initiate an intricate signaling cascade known as the Unfolded Protein Response (UPR) to remediate accumulation of misfolded proteins in its lumen, a condition referred to as ER stress. The UPR aids in fine-tuning, expanding and/or modifying  the cellular proteome, especially in specialized secretory cells, to match everchanging physiologic cues and metabolic demands. Sustained activation of the UPR due to chronic ER stress, however, is known to hasten cell death and drive pathophysiology of several diseases. A growing body of evidence suggests that ER stress and an aberrant UPR may contribute to poor skeletal health and the development of osteoporosis. Small molecule therapeutics that target distinct components of the UPR may therefore have implications for developing novel treatment modalities relevant to the skeleton. This review summarizes the complexity of UPR actions in bone cells in the context of skeletal physiology and osteoporotic bone loss, and highlights the need for future mechanistic studies to develop novel UPR therapeutics that mitigate adverse skeletal outcomes.

Immunological evaluation of herbal extracts commonly used for treatment of mental diseases during pregnancy

Nonpsychotic mental diseases (NMDs) affect approximately 15% of pregnant women in the US. Herbal preparations are perceived a safe alternative to placenta-crossing antidepressants or benzodiazepines in the treatment of nonpsychotic mental diseases. But are these drugs really safe for mother and foetus? This question is of great relevance to physicians and patients. Therefore, this study investigates the influence of St. John's wort, valerian, hops, lavender, and California poppy and their compounds hyperforin and hypericin, protopine, valerenic acid, and valtrate, as well as linalool, on immune modulating effects in vitro. For this purpose a variety of methods was applied to assess the effects on viability and function of human primary lymphocytes. Viability was assessed via spectrometric assessment, flow cytometric detection of cell death markers and comet assay for possible genotoxicity. Functional assessment was conducted via flow cytometric assessment of proliferation, cell cycle and immunophenotyping. For California poppy, lavender, hops, and the compounds protopine and linalool, and valerenic acid, no effect was found on the viability, proliferation, and function of primary human lymphocytes. However, St. John's wort and valerian inhibited the proliferation of primary human lymphocytes. Hyperforin, hypericin, and valtrate inhibited viability, induced apoptosis, and inhibited cell division. Calculated maximum concentration of compounds in the body fluid, as well as calculated concentrations based on pharmacokinetic data from the literature, were low and supported that the observed effects in vitro would probably have no relevance on patients. In-silico analyses comparing the structure of studied substances with the structure of relevant control substances and known immunosuppressants revealed structural similarities of hyperforin and valerenic acid to the glucocorticoids. Valtrate showed structural similarities to the T cells signaling modulating drugs.

Bone Remodeling Markers in Children with Acute Lymphoblastic Leukemia after Intensive Chemotherapy: The Screenshot of a Biochemical Signature

PURPOSE

to investigate the effects of intensive chemotherapy and glucocorticoid (GC) treatment on bone remodeling markers in children with acute lymphoblastic leukemia (ALL).

METHODS

A cross-sectional study was carried out in 39 ALL children (aged 7.64 ± 4.47) and 49 controls (aged 8.7 ± 4.7 years). Osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), osteocalcin (OC), C-terminal telopeptide of type I collagen (CTX), bone alkaline phosphatase (bALP), tartrate-resistant acid phosphatase 5b (TRACP5b), procollagen type I N-terminal propeptide (P1NP), Dickkopf-1 (DKK-1), and sclerostin were assessed. Statistical analysis was conducted using the principal component analysis (PCA) to study patterns of associations in bone markers.

RESULTS

ALL patients showed significantly higher OPG, RANKL, OC, CTX, and TRACP5b than the controls (p ≤ 0.02). Considering ALL group, we found a strong positive correlation among OC, TRACP5b, P1NP, CTX, and PTH (r = 0.43-0.69; p < 0.001); between CTX and P1NP (r = 0.5; p = 0.001); and between P1NP and TRAcP (r = 0.63; p < 0.001). The PCA revealed OC, CTX, and P1NP as the main markers explaining the variability of the ALL cohort.

CONCLUSIONS

Children with ALL showed a signature of bone resorption. The assessment of bone biomarkers could help identify ALL individuals who are most at risk of developing bone damage and who need preventive interventions.

Prednisone acetate modulates Th1/Th2 and Th17/Treg cell homeostasis in experimental autoimmune uveitis via orchestrating the Notch signaling pathway

Uveitis is an immune eye disease that can seriously impair vision. Glucocorticoids (GC_S) have been extensively used to treat uveitis, though the mechanisms have not been fully elucidated. In this study, we investigated the regulatory effects of prednisone acetate (PA) on the Th1/Th2 and Th17/Treg balance in experimental autoimmune uveitis (EAU) through modulating the Notch signaling pathway. Briefly, Lewis rats were randomly divided into the normal control (NC), EAU, and EAU + PA groups. Rats in EAU and EAU + PA groups were induced EAU, while those in the EAU + PA group were treated with PA. Clinical and histopathological scores were employed to assess the progression of EAU. The expression levels of Notch signaling-related molecules (Notch1, Notch2, Dll3, Dll4, and Rbpj) and Th-associated cytokines (IFN-γ, IL-4, IL-10, and IL-17) were assessed via quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA). In addition, the frequencies of Th1, Th2, Th17 and Treg cells were detected by flow cytometry. These experimental results indicated that activation of the Notch signaling pathway occurred in EAU rats and resulted in a severe imbalance of the Th17/Treg and Th1/Th2 ratios. PA treatment significantly alleviated ocular inflammation, inhibited activation of the Notch signaling pathway, and declined Th1, and Th17 cell differentiation, thereby restoring the Th1/Th2 and Th17/Treg balance. Collectively, PA can positively enhance the systemic immune response and improve the intraocular microenvironmental homeostasis by inhibiting activation of the Notch signaling pathway and by restoring Th1/Th2 and Th17/Treg balance, thus achieving the goal of treating uveitis.

Characteristics of the state of bone tissue in genetically modified mice with impaired enzymatic regulation of steroid hormone metabolism

Introduction: The aim was to evaluate the structural and functional changes of bone tissue in mice with null expression of 11β-HSD2 or both 11β-HSD2 and Apolipoprotein E.

Materials and methods: The experimental study was performed in 60 male mice, weighting 24–30 g. The animals were kept in accordance with the rules of laboratory practice for preclinical studies on the territory of the Russian Federation. Mice lacking 11β-HSD2 (Hsd2-/-) and male mice lacking 11β-HSD2 and Apolipoprotein E (Hsd2-/-/Apoe-/-) were used in the study. We studied and characterized the state of bone tissue, indicators of bone density, microcirculation in bone tissue, endothelial dysfunction coefficient, width of bone trabeculae, as well as serum concentrations of bone alkaline phosphatase, hydroxyproline, deoxyprinoline and expression levels of p53, Bcl2, Bax, eNOS genes.

Results and discussion: We showed that mice with the Hsd2-/- genotype with no expression of 11ß-HSD2 by the 6th month of life showed a statistically significant decrease in bone density, which progresses to the 7th and 8th months of life. At the 8th month of animal life, a decrease in bone density is accompanied by a statistically significant decrease in the level of microcirculation in the bone and an increase in the coefficient of endothelial dysfunction. Taking into account the relationship of endothelial dysfunction, atherogenesis and disorders in the processes of bone remodeling, in the framework of this study, we also assessed the state of bone tissue in double transgenes with the genotype Hsd2-/-/Apoe-/-, which lack the expression of both 11ß-HSD2 and Apolipoprotein E. In this study, we also saw increased activation of processes leading to disruption of bone remodeling processes. In the group of the animals with the genotype Hsd2-/-/Apoe-/-, we found statistically significant differences from the mice with no expression of 11ß-HSD2 in bone density and microcirculation, and the width of bone trabeculae. Also, a statistically significant increase in hydroxyproline and deoxyprinoline was found in the group of double transgenes, in the absence of significant changes in the concentration of bone alkaline phosphatase. This fact indicates a pronounced activation of bone resorption processes in the absence of activation of osteosynthesis processes, which leads to the detected violation of bone remodeling processes.

Conclusion: Thus, we have shown that a violation of the metabolic regulation of steroid hormone metabolism in animals with null expression of the 11ß-HSD2 (Hsd2-/- genotype) leads to the development of signs of osteoporosis – bone density decreases, which is accompanied by a decrease in the width of bone trabeculae, the level of microcirculation in bone tissue decreases simultaneously with an increase in the coefficient of endothelial dysfunction. The additional null expression of ApoE gene in double transgenes with the genotype Hsd2-/-/Apoe-/- leads to an increase in the severity of changes associated with a violation of bone remodeling processes and, in addition to a more pronounced change in bone tissue density, bone trabecular width, microcirculation and the coefficient of endothelial dysfunction leads to an increase in the concentration of biochemical markers of bone resorption. These changes indicate the important role of the enzyme 11ß-hydroxysteroid dehydrogenase type 2 in the processes of bone remodeling disorders.

Graphical abstract

Anabolic therapy for osteoporosis: update on efficacy and safety

Anabolic agents for the treatment of osteoporosis increase bone density, improve bone strength, and reduce fracture risk. They are distinguished from antiresorptive drugs by their property of increasing osteoblastic bone formation. Teriparatide and abaloparatide are parathyroid hormone receptor agonists that increase bone remodeling with bone formation increasing more than bone resorption. Romosozumab is a humanized monoclonal antibody to sclerostin that has a "dual effect" of increasing bone formation while decreasing bone resorption. The bone forming effects of anabolic therapy appear to be self-limited, making it imperative that it be followed by antiresorptive therapy to enhance or consolidate the beneficial effects achieved. Teriparatide, abaloparatide, and romosozumab each have unique pharmacological properties that must be appreciated when using them to treat patients at high risk for fracture. Clinical trials have shown a favorable balance of expected benefits and possible risks. Anabolic therapy is superior to bisphosphonates for high-risk patients, with greater benefit when initial treatment is with an anabolic agent followed by an antiresorptive drug, rather than the reverse sequence of therapy. Recent clinical practice guidelines have included recommendations with examples of patients who are candidates with anabolic therapy.

Bone-targeting delivery of platelet lysate exosomes ameliorates glucocorticoid-induced osteoporosis by enhancing bone-vessel coupling

BACKGROUND

Glucocorticoids (GCs) overuse is associated with decreased bone mass and osseous vasculature destruction, leading to severe osteoporosis. Platelet lysates (PL) as a pool of growth factors (GFs) were widely used in local bone repair by its potent pro-regeneration and pro-angiogenesis. However, it is still seldom applied for treating systemic osteopathia due to the lack of a suitable delivery strategy. The non-targeted distribution of GFs might cause tumorigenesis in other organs.

RESULTS

In this study, PL-derived exosomes (PL-exo) were isolated to enrich the platelet-derived GFs, followed by conjugating with alendronate (ALN) grafted PEGylated phospholipid (DSPE-PEG-ALN) to establish a bone-targeting PL-exo (PL-exo-ALN). The in vitro hydroxyapatite binding affinity and in vivo bone targeting aggregation of PL-exo were significantly enhanced after ALN modification. Besides directly modulating the osteogenic and angiogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs), respectively, PL-exo-ALN also facilitate their coupling under GCs' stimulation. Additionally, intravenous injection of PL-exo-ALN could successfully rescue GCs induced osteoporosis (GIOP) in vivo.

CONCLUSIONS

PL-exo-ALN may be utilized as a novel nanoplatform for precise infusion of GFs to bone sites and exerts promising therapeutic potential for GIOP.

Tocotrienol as a Protecting Agent against Glucocorticoid-Induced Osteoporosis: A Mini Review of Potential Mechanisms

Glucocorticoid-induced osteogenic dysfunction is the main pathologyical mechanism underlying the development of glucocorticoid-induced osteoporosis. Glucocorticoids promote adipogenic differentiation and osteoblast apoptosis through various pathways. Various ongoing studies are exploring the potential of natural products in preventing glucocorticoid-induced osteoporosis. Preclinical studies have consistently shown the bone protective effects of tocotrienol through its antioxidant and anabolic effects. This review aims to summarise the potential mechanisms of tocotrienol in preventing glucocorticoid-induced osteoporosis based on existing in vivo and in vitro evidence. The current literature showed that tocotrienol prevents oxidative damage on osteoblasts exposed to high levels of glucocorticoids. Tocotrienol reduces lipid peroxidation and increases oxidative stress enzyme activities. The reduction in oxidative stress protects the osteoblasts and preserves the bone microstructure and biomechanical strength of glucocorticoid-treated animals. In other animal models, tocotrienol has been shown to activate the Wnt/β-catenin pathway and lower the RANKL/OPG ratio, which are the targets of glucocorticoids. In conclusion, tocotrienol enhances osteogenic differentiation and bone formation in glucocorticoid-treated osteoblasts while improving structural integrity in glucocorticoid-treated rats. This is achieved by preventing oxidative stress and osteoblast apoptosis. However, these preclinical results should be validated in a randomised controlled trial.

Cladrin alleviates dexamethasone-induced apoptosis of osteoblasts and promotes bone formation through autophagy induction via AMPK/mTOR signaling

Glucocorticoid-induced osteoporosis (GIOP) is a common clinical consequence that arises due to the extensive usage of glucocorticoids. Cladrin (Clad), a methoxylated isoflavone has been reported to have a bone protecting effect by enhancing osteoblast proliferation and differentiation. However, its consequences on GIOP are not reported yet. This study investigates whether Clad protects against the deleterious effects of Dexamethasone (Dex) on osteoblast and bone. Mice calvarial osteoblasts were treated with Clad and then exposed to Dex to study the effect on osteoblast differentiation, proliferation, and survival. Further, GIOP mice were treated with Clad (5 and 10 mg/kg) doses along with reference standard alendronate (ALN 3 mg/kg) for evaluation of bone protecting effect of Clad. We analyzed bone and vertebral microarchitecture, mechanical strength, and biochemical parameters. We observed that Clad at 10 nM concentration mitigated Dex-induced cytotoxicity and defend osteoblasts against apoptosis. Subsequent results demonstrate that Clad suppressed apoptosis of osteoblast in the presence of Dex by enhancing autophagy in a way that was reliant on the AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) pathway. Furthermore, micro-CT scanning, eco MRI results, and serum CTX levels revealed that 12 weeks of Clad treatment prevented bone loss and preserved trabecular bone mass in GIOP animals. We also observed that Clad treated osteoblasts had a lower rate of apoptosis and a greater LC3-II/LC3-I ratio than the Dex group. Our findings show that Clad can protect osteoblasts against glucocorticoids by inducing autophagy via the AMPK/mTOR pathway.

Nrf2 signaling activation by a small molecule activator compound 16 inhibits hydrogen peroxide-induced oxidative injury and death in osteoblasts

We explored the potential activity of compound 16 (Cpd16), a novel small molecule Nrf2 activator, in hydrogen peroxide (H₂O₂)-stimulated osteoblasts. In the primary murine/human osteoblasts and MC3T3-E1 murine osteoblastic cells, Cpd16 treatment at micro-molar concentrations caused disassociation of Keap1-Nrf2 and Nrf2 cascade activation. Cpd16 induced stabilization of Nrf2 protein and its nuclear translocation, thereby increasing the antioxidant response elements (ARE) reporter activity and Nrf2 response genes transcription in murine and human osteoblasts. Significantly, Cpd16 mitigated oxidative injury in H₂O₂-stimulited osteoblasts. H₂O₂-provoked apoptosis as well as programmed necrosis in osteoblasts were significantly alleviated by the novel Nrf2 activator. Cpd16-induced Nrf2 activation and osteoblasts protection were stronger than other known Nrf2 activators. Dexamethasone- and nicotine-caused oxidative stress and death in osteoblasts were attenuated by Cpd16 as well. Cpd16-induced osteoblast cytoprotection was abolished by Nrf2 short hairpin RNA or knockout, but was mimicked by Keap1 knockout. Keap1 Cys151S mutation abolished Cpd16-induced Nrf2 cascade activation and osteoblasts protection against H₂O₂. Importantly, weekly Cpd16 administration largely ameliorated trabecular bone loss in ovariectomy mice. Together, Cpd16 alleviates H₂O₂-induced oxidative stress and death in osteoblasts by activating Nrf2 cascade.

Stimulation of osteoclast formation and bone resorption by glucocorticoids: Synergistic interactions with the calcium regulating hormones parathyroid hormone and 1,25(OH)2-vitamin D3

Osteoporosis is a significant health problem, with skeletal fractures increasing morbidity and mortality. Excess glucocorticoids (GC) represents the leading cause of secondary osteoporosis. The first phase of glucocorticoid-induced osteoporosis is increased bone resorption. In this Chapter, in vitro studies of the direct glucocorticoid receptor (GR) mediated cellular effects of GC on osteoclasts to affect bone resorption and indirect effects on osteoblast lineage cells to increase the RANKL/OPG ratio and stimulate osteoclastogenesis and bone resorption are reviewed in detail, together with detailed descriptions of in vivo effects of GC in different portions of the skeleton in research animals and humans. Brief sections are devoted to contrasting functions of GC in osteonecrosis, vitamin D formation, in vitro and in vivo bone resorptive actions dependent on vitamin D receptor and vitamin D toxicity, as well as the molecular basis of GR action. Included are also more detailed assessments of the interactions of GC with the major calcium regulating hormones, 1,25(OH)₂-vitamin D3 and parathyroid hormone, describing the in vitro increases in RANKL/OPG ratios, osteoclastogenesis and synergistic bone resorption that occurs when GC is combined with either 1,25(OH)₂-vitamin D3 or parathyroid hormone. Additionally, a molecular basic for the synergistic interaction of GC with 1,25(OH)₂-vitamin D3 is provided along with a suggested molecular basic for the interaction between GC and parathyroid hormone.

Antiosteoporosis effects of a marine antimicrobial peptide pardaxin via regulation of the osteogenesis pathway

Antimicrobial peptides (AMPs) are known to play an important role in natural immunity. Moreover, the diverse biological activities of AMPs showed great potency in treating many diseases. Thus, in this study, we used an AMP, that is, pardaxin, from a marine fish (Pardachirus marmoratus), which has been reported to possess antibacterial and antitumor activities. We first investigated the mechanisms of pardaxin in promoting osteogenic differentiation in vitro and in vivo. As per our data, it was determined that pardaxin could stimulate bone morphogenetic protein-2 (BMP-2) and downstream cascade. The activation of BMP-2 could further induce the phosphorylation of Akt and extracellular signal-regulated kinase (ERK). Additionally, the activation of p-Akt and p-ERK could prompt the elevation and translocation of runt-related transcription factor 2 (runx-2), which is associated with osteoblast differentiation. The translocation of runx-2 initiated transcription and translation of osteogenesis-related markers, including alkaline phosphatase (ALP), osterix, and osteocalcin. Pardaxin significantly facilitated preosteoblast cells in mineralization and reversed dexamethasone- (DM-) induced zebrafish bone formation deficiency by activating the osteogenesis pathway. Therefore, we suggest that pardaxin could be a possible candidate for osteoporosis treatment and a promising therapeutic agent.

Characterization of a novel non-steroidal glucocorticoid receptor agonist optimized for topical treatment

Glucocorticoids (GCs) are commonly used topical treatments for skin diseases but are associated with both local and systemic side effects. In this study, we describe a selective non-steroidal glucocorticoid receptor (GR) agonist for topical use, LEO 134310, which is rapidly deactivated in the blood resulting in low systemic exposure and a higher therapeutic index in the TPA-induced skin inflammation mouse model compared with betamethasone valerate (BMV) and clobetasol propionate (CP). Selectivity of LEO 134310 for GR was confirmed within a panel of nuclear receptors, including the mineralocorticoid receptor (MR), which has been associated with induction of skin atrophy. Topical treatment with LEO 134310 in minipigs did not result in any significant reduction in epidermal thickness in contrast to significant epidermal thinning induced by treatment with BMV and CP. Thus, the profile of LEO 134310 may potentially provide an effective and safer treatment option for skin diseases compared with currently used glucocorticoids.

Hypobaric hypoxia deteriorates bone mass and strength in mice

Mountaineers at high altitude are at increased risk of acute mountain sickness as well as high altitude pulmonary and cerebral edema. A densitometric study in mountaineers has suggested that expeditions at high altitude decrease bone mineral density. Surprisingly, the in vivo skeletal effects of hypobaric hypoxia are largely unknown, and have not been studied using advanced contemporary methods to assess bone microstructure. Eighty-four 22-week-old female mice were divided into seven groups with 12 mice in each group: 1. Baseline; 2. Normobaric, 4 weeks; 3. Hypobaric hypoxia, 4 weeks; 4. Normobaric, 8 weeks; 5. Hypobaric hypoxia, 8 weeks; 6. Normobaric, 12 weeks; and 7. Hypobaric hypoxia, 12 weeks. Hypobaric hypoxia mice were housed in hypobaric chambers at an ambient pressure of 500 mbar (5500 m altitude), while normobaric mice were housed at sea level atmospheric pressure for 4, 8, or 12 weeks, respectively. Hypobaric hypoxia had a profound impact on femoral cortical bone and L4 trabecular bone, while the effect on femoral trabecular bone was less pronounced. Hypobaric hypoxia reduced the bone strength of the femoral mid-diaphysis and L4 at all time-points. At femoral cortical bone, hypobaric hypoxia reduced bone formation through fewer mineralizing surfaces and lower bone formation rate after 2 weeks. In addition, bone strength decreased, and C-terminal telopeptide of type I collagen (CTX-I) increased independently of the duration of exposure to simulated high altitude. At L4, hypobaric hypoxia resulted in a substantial reduction in bone volume fraction, trabecular thickness, and trabecular number after 4 weeks of exposure. Hypobaric hypoxia reduced bone strength and femoral bone mass, while femoral trabecular bone was much less affected, indicating the skeletal response to hypobaric hypoxia differ between cortical and trabecular bone. These findings provide initial preclinical support for future clinical studies in mountaineers to assess bone status and bone strength after exposure to prolonged high altitude exposure.

Comprehensive analysis of the m6A-related molecular patterns and diagnostic biomarkers in osteoporosis

BACKGROUND

N6-methyladenosine (m6A) modification is a critical epigenetic modification in eukaryotes and involves several biological processes and occurrences of diseases. However, the roles and regulatory mechanisms of m6A regulators in osteoporosis (OP) remain unclear. Thus, the purpose of this study is to explore the roles and mechanisms of m6A regulators in OP.

METHODS

The mRNA and microRNA (miRNA) expression profiles were respectively obtained from GSE56815, GSE7158, and GSE93883 datasets in Gene Expression Omnibus (GEO). The differential expression of 21 m6A regulators between high-bone mineral density (BMD) and low-BMD women was identified. Then, a consensus clustering of low-BMD women was performed based on differentially expressed (DE)-m6A regulators. The m6A-related differentially expressed genes (DEGs), the differentially expressed miRNAs (DE-miRNAs), and biological functions were investigated. Moreover, a weighted gene co-expression network analysis (WGCNA) was constructed to identify the OP-related hub modules, hub genes, and the functional pathways. Then, an m6A regulator-target-pathway network and the competing endogenous RNA (ceRNA) network in key modules were constructed. A least absolute shrinkage and selection operation (LASSO) Cox regression model and a Support Vector Machine-Recursive Feature Elimination (SVM-RFE) model were constructed to identify the candidate genes for OP prediction. The receiver operator characteristic (ROC) curves were used to validate the performances of predictive models and candidate genes.

RESULTS

A total of 10,520 DEGs, 13 DE-m6A regulators, and 506 DE-miRNAs between high-BMD and low-BMD women were identified. Two m6A-related subclusters with 13 DE-m6A regulators were classified for OP. There were 5,260 m6A-related DEGs identified between two m6A-related subclusters, the PI3K-Akt, MAPK, and immune-related pathways, and bone metabolism was mainly enriched in cluster 2. Cell cycle-related pathways, RNA methylation, and cell death-related pathways were significantly involved in cluster 1. Five modules were identified as key modules based on WGCNA, and an m6A regulator-target gene-pathway network and the ceRNA network were constructed in module brown. Moreover, three m6A regulators (FTO, YTHDF2, and CBLL1) were selected as the candidate genes for OP.

CONCLUSION

M6A regulators play an important role in the occurrences and diagnosis of OP.

The effect of local steroid application on bony fusion in a rat posterolateral spinal arthrodesis model

INTRODUCTION

Local steroid administration during anterior cervical spine surgery has been shown to improve postoperative dysphagia. However, concerns over potential complications remain. This study aims to evaluate the effect of local steroid administration on bone regeneration and spine fusion in a preclinical model, as well as the impact on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) in a 3D culture system.

MATERIALS AND METHODS

Forty-five rats underwent bilateral L4-L5 posterolateral lumbar fusion (PLF) utilizing local delivery of low-dose recombinant human bone morphogenetic protein-2 (rhBMP-2; 0.5 μg/implant). Rats were divided into three groups: no steroid (control), low dose (0.5 mg/kg), and high dose (2.5 mg/kg) of triamcinolone. Bone growth and fusion were assessed using radiography, blinded manual palpation, and micro-CT analysis and were visualized by histology. The impact of triamcinolone exposure on osteogenic differentiation of hBM-MSCs was evaluated by gene expression analysis, alkaline phosphatase activity assay, and alizarin red staining.

RESULTS

No significant differences in fusion scores or rates were seen in the low- or high-dose steroid treatment groups relative to untreated controls. Quantification of new bone formation via micro-CT imaging revealed no significant between-group differences in the volume of newly regenerated bone. Triamcinolone also had no negative impact on pro-osteogenic gene transcript levels, and ALP activity was enhanced in the presence of triamcinolone. Mineral deposition appeared comparable in cultures grown with and without triamcinolone.

CONCLUSIONS

Local steroid application does not seem to inhibit rhBMP-2-mediated spine fusion in rats, though our study may not be adequately powered to detect differences in fusion as measured by manual palpation or bone volume as measured by micro-CT. These findings suggest that local triamcinolone may not increase pseudarthrosis in spine fusion procedures. Further large animal and clinical studies to verify its safety and efficacy are warranted.

Screening and Identification of Hub Genes in the Corticosteroid Resistance Network in Human Airway Epithelial Cells via Microarray Analysis

Background and Objective: Corticosteroid resistance is a major barrier to chronic obstructive pulmonary disease (COPD), but the exact mechanism of corticosteroid resistance in COPD has been less well studied. Methods: The microarray dataset GSE11906, which includes genomic and clinical data on COPD, was downloaded from the Gene Expression Omnibus (GEO) database, and the differentially expressed genes (DEGs) were identified using R software. Gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes (KEGG) were utilized to enrich and analyze the gene cohort related to the response to steroid hormones, respectively. The Connectivity Map (CMap) database was used to screen corticosteroid resistance-related drugs that might exert a potential therapeutic effect. STRING was used to construct a protein-protein interaction (PPI) network of the gene cohort, and the CytoHubba plug-in of Cytoscape was used to screen the hub genes in the PPI network. The expression levels of hub genes in cigarette smoke extract (CSE)-stimulated bronchial epithelial cells were assayed by quantitative real-time PCR and western blotting. Results: Twenty-one genes were found to be correlated with the response to steroid hormones. In the CMap database, 32 small-molecule compounds that might exert a therapeutic effect on corticosteroid resistance in COPD were identified. Nine hub genes were extracted from the PPI network. The expression levels of the BMP4, FOS, FN1, EGFR, and SPP1 proteins were consistent with the microarray data obtained from molecular biology experiments. Scopoletin significantly restrained the increases in the levels of AKR1C3, ALDH3A1, FN1 and reversed the decreases of phosphorylated GR and HDAC2 caused by CSE exposure. Conclusion: The BMP4, FOS, FN1, EGFR, and SPP1 genes are closely correlated with CSE-induced glucocorticoid resistance in airway epithelial cells. Scopoletin may be a potential drug for the treatment of glucocorticoid resistance caused by CSE.

A Review on Re-Packaging of Bisphosphonates Using Biomaterials

The need for bone repair and insight into new regeneration therapies as well as improvement of existing regeneration routes is constantly increasing as a direct consequence of the rise in the number of trauma victims, musculoskeletal disorders, and increased life expectancy. Bisphosphonates (BPs) have emerged as a class of drugs with proven efficacy against many bone disorders. The most recent ability of this class of drugs is being explored in its anti-cancer ability. However, despite the pharmacological success, there are certain shortcomings that have circumvented this class of the drug. The mediation of biomaterials in delivering bisphosphonates has greatly helped in overcoming some of these shortcomings. This article is focused on reviewing the benefits the bisphosphonates have provided upon getting delivered via the use of biomaterials. Furthermore, the role of bisphosphonates as a potent anticancer agent is also accounted. It is witnessed that employing engineering tools in combination with therapeutics has the potential to provide solutions to bone loss from degenerative, surgical, or traumatic processes, and also aid in accelerating the healing of large bone fractures and problematic non-union fractures. The role of nanotechnology in enhancing the efficacy of the bisphosphonates is also reviewed and innovative approaches are identified.

miR-433-3p suppresses bone formation and mRNAs critical for osteoblast function in mice

MicroRNAs (miRNAs) are key posttranscriptional regulators of osteoblastic commitment and differentiation. miR-433-3p was previously shown to target Runt-related transcription factor 2 (Runx2) and to be repressed by bone morphogenetic protein (BMP) signaling. Here, we show that miR-433-3p is progressively decreased during osteoblastic differentiation of primary mouse bone marrow stromal cells in vitro, and we confirm its negative regulation of this process. Although repressors of osteoblastic differentiation often promote adipogenesis, inhibition of miR-433-3p did not affect adipocyte differentiation in vitro. Multiple pathways regulate osteogenesis. Using luciferase-3' untranslated region (UTR) reporter assays, five novel miR-433-3p targets involved in parathyroid hormone (PTH), mitogen-activated protein kinase (MAPK), Wnt, and glucocorticoid signaling pathways were validated. We show that Creb1 is a miR-433-3p target, and this transcription factor mediates key signaling downstream of PTH receptor activation. We also show that miR-433-3p targets hydroxysteroid 11-β dehydrogenase 1 (Hsd11b1), the enzyme that locally converts inactive glucocorticoids to their active form. miR-433-3p dampens glucocorticoid signaling, and targeting of Hsd11b1 could contribute to this phenomenon. Moreover, miR-433-3p targets R-spondin 3 (Rspo3), a leucine-rich repeat-containing G-protein coupled receptor (LGR) ligand that enhances Wnt signaling. Notably, Wnt canonical signaling is also blunted by miR-433-3p activity. In vivo, expression of a miR-433-3p inhibitor or tough decoy in the osteoblastic lineage increased trabecular bone volume. Mice expressing the miR-433-3p tough decoy displayed increased bone formation without alterations in osteoblast or osteoclast numbers or surface, indicating that miR-433-3p decreases osteoblast activity. Overall, we showed that miR-433-3p is a negative regulator of bone formation in vivo, targeting key bone-anabolic pathways including those involved in PTH signaling, Wnt, and endogenous glucocorticoids. Local delivery of miR-433-3p inhibitor could present a strategy for the management of bone loss disorders and bone defect repair. © 2021 American Society for Bone and Mineral Research (ASBMR).

Lycii radicis cortex inhibits glucocorticoid‑induced bone loss by downregulating Runx2 and BMP‑2 expression

Lycii radicis cortex (LRC) has been used to regulate high blood pressure, body temperature, pain and bone disorders in East Asia. Glucocorticoids (GCs), also known as steroids, are potent immunity regulators widely used in the treatment of inflammatory diseases. However, despite their effectiveness, GC usage is strictly controlled due to severe side‑effects, such as osteoporosis. However, further research is required as to date, at least to the best of our knowledge, there is no appropriate model to overcome secondary osteoporosis as a side‑effect of GC use. Thus, the aim of the present study was to establish an experimental model of osteoporosis induced by GC. Furthermore, the present study aimed to establish the research methodology for medical evaluations of the effectiveness and side‑effects of GCs. A secondary osteoporosis animal model was established, and the animals were divided into two groups as follows: The allergic contact dermatitis (ACD)‑induced group and the non‑ACD‑induced group. In the ACD‑induced group, a GC topical application group was compared with a GC subcutaneous injection group. The results revealed that the presence of ACD affected the induction of GC‑mediated osteoporosis. Therefore, the group exhibiting induced ACD that was treated with a topical application of GC was selected for examining the side‑effects of GCs. The effects of LRC on secondary osteoporosis were confirmed in vivo and in vitro. The results indicated that LRC regulated dexamethasone‑induced osteoblast apoptotic markers, including caspase‑6, caspase‑9, X‑linked inhibitor of apoptosis, apoptosis inhibitor 1 and apoptosis inhibitor 2, and increased the expression of osteoblast differentiation‑related genes, such as Runt‑related transcription factor 2 and bone morphogenetic protein 2 in the MC3T3E‑1 cell line. LRC also significantly reduced GC‑induced osteoporosis and exerted anti‑inflammatory effects in vivo. In addition, LRC inhibited the reduction of calbindin‑D28k in the kidney. Overall, the results of the present study suggest that the use of LRC alleviates GC‑induced secondary osteoporosis.

A novel Keap1 inhibitor iKeap1 activates Nrf2 signaling and ameliorates hydrogen peroxide-induced oxidative injury and apoptosis in osteoblasts

An ultra-large structure-based virtual screening has discovered iKeap1 as a direct Keap1 inhibitor that can efficiently activate Nrf2 signaling. We here tested its potential effect against hydrogen peroxide (H₂O₂)-induced oxidative injury in osteoblasts. In primary murine and human osteoblasts, iKeap1 robustly activated Nrf2 signaling at micromole concentrations. iKeap1 disrupted Keap1-Nrf2 association, causing Nrf2 protein stabilization, cytosol accumulation and nuclear translocation in murine and human osteoblasts. The anti-oxidant response elements (ARE) activity and transcription of Nrf2-ARE-dependent genes (including HO1, NQO1 and GCLC) were increased as well. Significantly, iKeap1 pretreatment largely ameliorated H₂O₂-induced reactive oxygen species production, lipid peroxidation and DNA damage as well as cell apoptosis and programmed necrosis in osteoblasts. Moreover, dexamethasone- and nicotine-induced oxidative injury and apoptosis were alleviated by iKeap1. Importantly, Nrf2 shRNA or CRISPR/Cas9-induced Nrf2 knockout completely abolished iKeap1-induced osteoblast cytoprotection against H₂O₂. Conversely, CRISPR/Cas9-induced Keap1 knockout induced Nrf2 cascade activation and mimicked iKeap1-induced cytoprotective actions in murine osteoblasts. iKeap1 was ineffective against H₂O₂ in the Keap1-knockout murine osteoblasts. Collectively, iKeap1 activated Nrf2 signaling cascade to inhibit H₂O₂-induced oxidative injury and death of osteoblasts.

Bone microarchitecture in patients with autoimmune hepatitis

In patients with autoimmune hepatitis (AIH), osteoporosis represents a common extrahepatic complication, which we recently showed by an assessment of areal bone mineral density (aBMD) via dual-energy x-ray absorptiometry (DXA). However, it is well established that bone quality and fracture risk does not solely depend on aBMD, but also on bone microarchitecture. It is currently not known whether AIH patients exhibit a site-specific or compartment-specific deterioration in the skeletal microarchitecture. In order to assess potential geometric, volumetric, and microarchitectural changes, high-resolution peripheral quantitative computed tomography (HR-pQCT) measurements were performed at the distal radius and distal tibia in female patients with AIH (n = 51) and compared to age-matched female healthy controls (n = 32) as well as to female patients with AIH/primary biliary cholangitis (PBC) overlap syndrome (n = 25) and female patients with PBC alone (PBC, n = 36). DXA at the lumbar spine and hip, clinical characteristics, transient elastography (FibroScan) and laboratory analyses were also included in this analysis. AIH patients showed a predominant reduction of cortical thickness (Ct.Th) in the distal radius and tibia compared to healthy controls (p < .0001 and p = .003, respectively). In contrast, trabecular parameters such as bone volume fraction (BV/TV) did not differ significantly at the distal radius (p = .453) or tibia (p = .508). Linear regression models revealed significant negative associations between age and Ct.Th (95% confidence interval [CI], -14 to -5 μm/year, p < .0001), but not between liver stiffness, cumulative prednisolone dose (even after an adjustment for age), or disease duration with bone microarchitecture. The duration of high-dose prednisolone (≥7.5 mg) was negatively associated with trabecular thickness (Tb.Th) at the distal radius. No differences in bone microarchitecture parameters between AIH, AIH/PBC, and PBC could be detected. In conclusion, AIH patients showed a severe age-dependent deterioration of the cortical bone microarchitecture, which is most likely the major contribution to the observed increased fracture risk in these patients. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Glucocorticoids suppressed osteoblast differentiation by decreasing Sema3A expression via the PIK3/Akt pathway

Glucocorticoids(GCs) are extensively used to treat inflammatory and autoimmune diseases. Excessive prolonged exposure to glucocorticoids is associated with an increased risk of osteoporosis. The inhibition of osteoblast differentiation by GCs is suggested as a major cause for GCs-induced osteoporosis (GIO). However, the precise mechanism underlying the role of GCs in osteoblasts differentiation is not fully elucidated. Semaphorin 3A (Sema3A), a secreted member of the Semaphorin family, enhances bone formation and promotes fracture healing, which is known to increase osteoblastic differentiation and stimulate osteogenesis in bone metabolism. Here, the present study explored the effect of Sema3A in osteoblast differentiation using dexamethasone (Dex) treatment of bone marrow stromal cells (BMSCs). Dex treatment decreased Sema3A expression in BMSCs in a dose-dependent manner. Moreover, Dex stimulation suppressed the differentiation of osteoblasts by reducing alkaline phosphatase (ALP) activity, osteoblastic marker genes expression and mineralization, but all of these effects were ameliorated by exogenous recombinant Sema3A administration. Furthermore, exogenous Sema3A administration reversed the Dex-mediated decrease in nuclear accumulation of β-catenin and β-catenin activity in BMSCs. Meanwhile, Dex was capable of simultaneously suppressing the phosphorylation of protein kinase B(Akt) and the expression level of Sema3A in BMSCs. These changes were significantly abolished by the PI3K/Akt agonist. These results suggest that Dex inhibits osteoblast differentiation by suppressing Sema3A expression via the PI3K/Akt pathway. These data provide new insights into the molecular mechanisms of Dex-induced osteoblast differentiation inhibition.

Bone remodeling stages under physiological conditions and glucocorticoid in excess: Focus on cellular and molecular mechanisms

This review provides a rationale for the cellular and molecular mechanisms of bone remodeling stages under physiological conditions and glucocorticoids (GCs) in excess. Remodeling is a synchronous process involving bone resorption and formation, proceeding through stages of: (1) resting bone, (2) activation, (3) bone resorption, (4) reversal, (5) formation, (6) termination. Bone remodeling is strictly controlled by local and systemic regulatory signaling molecules. This review presents current data on the interaction of osteoclasts, osteoblasts and osteocytes in bone remodeling and defines the role of osteoprogenitor cells located above the resorption area in the form of canopies and populating resorption cavities. The signaling pathways of proliferation, differentiation, viability, and cell death during remodeling are presented. The study of signaling pathways is critical to understanding bone remodeling under normal and pathological conditions. The main signaling pathways that control bone resorption and formation are RANK / RANKL / OPG; M-CSF – c-FMS; canonical and non-canonical signaling pathways Wnt; Notch; MARK; TGFβ / SMAD; ephrinB1/ephrinB2 – EphB4, TNFα – TNFβ, and Bim – Bax/Bak. Cytokines, growth factors, prostaglandins, parathyroid hormone, vitamin D, calcitonin, and estrogens also act as regulators of bone remodeling. The role of non-encoding microRNAs and long RNAs in the process of bone cell differentiation has been established. MicroRNAs affect many target genes, have both a repressive effect on bone formation and activate osteoblast differentiation in different ways. Excess of glucocorticoids negatively affects all stages of bone remodeling, disrupts molecular signaling, induces apoptosis of osteocytes and osteoblasts in different ways, and increases the life cycle of osteoclasts. Glucocorticoids disrupt the reversal stage, which is critical for the subsequent stages of remodeling. Negative effects of GCs on signaling molecules of the canonical Wingless (WNT)/β-catenin pathway and other signaling pathways impair osteoblastogenesis. Under the influence of excess glucocorticoids biosynthesis of biologically active growth factors is reduced, which leads to a decrease in the expression by osteoblasts of molecules that form the osteoid. Glucocorticoids stimulate the expression of mineralization inhibitor proteins, osteoid mineralization is delayed, which is accompanied by increased local matrix demineralization. Although many signaling pathways involved in bone resorption and formation have been discovered and described, the temporal and spatial mechanisms of their sequential turn-on and turn-off in cell proliferation and differentiation require additional research.

The association between systemic autoimmune disorders and epilepsy and its clinical implications

Systemic autoimmune disorders occur more frequently in patients with epilepsy than in the general population, suggesting shared disease mechanisms. The risk of epilepsy is elevated across the spectrum of systemic autoimmune disorders but is highest in systemic lupus erythematosus and type 1 diabetes mellitus. Vascular and metabolic factors are the most important mediators between systemic autoimmune disorders and epilepsy. Systemic immune dysfunction can also affect neuronal excitability, not only through innate immune activation and blood-brain barrier dysfunction in most epilepsies but also adaptive immunity in autoimmune encephalitis. The presence of systemic autoimmune disorders in subjects with acute seizures warrants evaluation for infectious, vascular, toxic and metabolic causes of acute symptomatic seizures, but clinical signs of autoimmune encephalitis should not be missed. Immunosuppressive medications may have antiseizure properties and trigger certain drug interactions with antiseizure treatments. A better understanding of mechanisms underlying the co-existence of epilepsy and systemic autoimmune disorders is needed to guide new antiseizure and anti-epileptogenic treatments. This review aims to summarize the epidemiological evidence for systemic autoimmune disorders as comorbidities of epilepsy, explore potential immune and non-immune mechanisms, and provide practical implications on diagnostic and therapeutic approach to epilepsy in those with comorbid systemic autoimmune disorders.

Repression of transcription by the glucocorticoid receptor: A parsimonious model for the genomics era

Glucocorticoids are potent anti-inflammatory drugs that are used to treat an extraordinary range of human disease, including COVID-19, underscoring the ongoing importance of understanding their molecular mechanisms. Early studies of GR signaling led to broad acceptance of models in which glucocorticoid receptor (GR) monomers tether repressively to inflammatory transcription factors, thus abrogating inflammatory gene expression. However, newer data challenge this core concept and present an exciting opportunity to reframe our understanding of GR signaling. Here, we present an alternate, two-part model for transcriptional repression by glucocorticoids. First, widespread GR-mediated induction of transcription results in rapid, primary repression of inflammatory gene transcription and associated enhancers through competition-based mechanisms. Second, a subset of GR-induced genes, including targets that are regulated in coordination with inflammatory transcription factors such as NF-κB, exerts secondary repressive effects on inflammatory gene expression. Within this framework, emerging data indicate that the gene set regulated through the cooperative convergence of GR and NF-κB signaling is central to the broad clinical effectiveness of glucocorticoids in terminating inflammation and promoting tissue repair.

Paeoniflorin Attenuates Dexamethasone-Induced Apoptosis of Osteoblast Cells and Promotes Bone Formation via Regulating AKT/mTOR/Autophagy Signaling Pathway

Paeoniflorin, a natural product derived from Paeonia lactiflora, possesses diverse pharmacological activities such as anti-inflammatory, antitumor, and antidiabetic effects. It has been reported for promoting osteoblastogenesis and inhibiting osteoclastogenesis. This study investigates the therapeutic effects of paeoniflorin in glucocorticoid-induced osteoporosis (GIOP) in vitro and in vivo. MC3T3-E1 cells were incubated with dexamethasone (DEX; 200 μM) and/or paeoniflorin (10 μM), followed by the investigation of cell proliferation, differentiation, mineralization, apoptosis, and autophagy. The AKT activator SC79 was used for evaluating the involvement of the AKT/mTOR signaling pathway. After DEX pretreatments, paeoniflorin promoted osteoblast differentiation and mineralization characterized by increase in Runx2, ALP, beclin-1, and LC3-II/LC3-I ratio levels and a decrease in apoptosis. The autophagy-promoting effects of paeoniflorin were reversed by SC79. C57BL/6 mice were given DEX (1 mg/kg) once daily and paeoniflorin (15 mg/kg) 48 hours for a total of 8 weeks followed by the investigation of histological changes, the trabecular bone microarchitecture, and the levels of bone turnover markers. The results showed that paeoniflorin increased alkaline phosphatase (ALP) activity and upregulated the expression of osteocalcin and beclin-1 but reduced the levels of Bax and C-terminal telopeptide of type I collagen (CTX-1). Thus, paeoniflorin may alleviate DEX-induced osteoporosis by promoting osteogenic differentiation and autophagy via inhibition of the AKT/mTOR signaling pathway.

Arbutin ameliorates glucocorticoid-induced osteoporosis through activating autophagy in osteoblasts

Chronic long-term glucocorticoid use causes osteoporosis partly by interrupting osteoblast homeostasis and exacerbating bone loss. Arbutin, a natural hydroquinone glycoside, has been reported to have biological activities related to the differentiation of osteoblasts and osteoclasts. However, the role and underlying mechanism of arbutin in glucocorticoid-induced osteoporosis are elusive. In this study, we demonstrated that arbutin administration ameliorated osteoporotic disorders in glucocorticoid dexamethasone (Dex)-induced mouse model, including attenuating the loss of bone mass and trabecular microstructure, promoting bone formation, suppressing bone resorption, and activating autophagy in bone tissues. Furthermore, Dex-stimulated mouse osteoblastic MC3T3-E1 cells were treated with arbutin. Arbutin treatment rescued Dex-induced repression of osteoblast differentiation and mineralization, the downregulation of osteogenic gene expression, reduced autophagic marker expression, and decreased autophagic puncta formation. The application of autophagy inhibitor 3-MA decreased autophagy, differentiation, and mineralization of MC3T3-E1 cells triggered by arbutin. Taken together, our findings suggest that arbutin treatment fends off glucocorticoid-induced osteoporosis, partly through promoting differentiation and mineralization of osteoblasts by autophagy activation.

Re-appraising the potential of naringin for natural, novel orthopedic biotherapies

Naringin is a naturally occurring flavonoid found in plants of the Citrus genus that has historically been used in traditional Chinese medical regimens for the treatment of osteoporosis. Naringin modulates signaling through numerous molecular pathways critical to musculoskeletal development, cellular differentiation, and inflammation. Administration of naringin increases in vitro expression of bone morphogenetic proteins (BMPs) and activation of the Wnt/β-catenin and extracellular signal-related kinase (Erk) pathways, thereby promoting osteoblastic proliferation and differentiation from stem cell precursors for bone formation. Naringin also inhibits osteoclastogenesis by both modifying RANK/RANKL interactions and inducing apoptosis in osteoclasts in vitro. In addition, naringin acts on the estrogen receptor in bone to mimic the native bone-preserving effects of estrogen, with few systemic side effects on other estrogen-sensitive tissues. The efficacy of naringin therapy in reducing the osteolysis characteristic of common musculoskeletal pathologies such as osteoporosis, degenerative joint disease, and osteomyelitis, as well as inflammatory conditions affecting bone such as diabetes mellitus, has been extensively demonstrated in vitro and in animal models. Naringin thus represents a naturally abundant, cost-efficient agent whose potential for use in novel musculoskeletal biotherapies warrants re-visiting and further exploration through human studies. Here, we review the cellular mechanisms of action that have been elucidated regarding the action of naringin on bone resident cells and the bone microenvironment, in vivo evidence of naringin’s osteostimulative and chondroprotective properties in the setting of osteolytic bone disease, and current limitations in the development of naringin-containing translational therapies for common musculoskeletal conditions.

Four-octyl itaconate activates Nrf2 cascade to protect osteoblasts from hydrogen peroxide-induced oxidative injury

Four-octyl itaconate (4-OI) is the cell-permeable derivative of itaconate that can activate Nrf2 signaling by alkylating Keap1’s cysteine residues. Here, we tested the potential effect of 4-OI on hydrogen peroxide (H₂O₂)-induced oxidative injury in osteoblasts. In OB-6 cells and primary murine osteoblasts, 4-OI was able to activate Nrf2 signaling cascade and cause Keap1–Nrf2 disassociation, Nrf2 protein stabilization, cytosol accumulation, and nuclear translocation. 4-OI also augmented antioxidant-response element reporter activity and promoted expression of Nrf2-dependent genes (HO1, NQO1, and GCLC). Pretreatment with 4-OI inhibited H₂O₂-induced reactive oxygen species production, cell death, and apoptosis in osteoblasts. Furthermore, 4-OI inhibited H₂O₂-induced programmed necrosis by suppressing mitochondrial depolarization, mitochondrial cyclophilin D-ANT1 (adenine nucleotide translocase 1)-p53 association, and cytosol lactate dehydrogenase release in osteoblasts. Ectopic overexpression of immunoresponsive gene 1 (IRG1) increased endogenous itaconate production and activated Nrf2 signaling cascade, thereby inhibiting H₂O₂-induced oxidative injury and cell death. In OB-6 cells, Nrf2 silencing or CRISPR/Cas9-induced Nrf2 knockout blocked 4-OI-induced osteoblast cytoprotection against H₂O₂. Conversely, forced Nrf2 activation, by CRISPR/Cas9-induced Keap1 knockout, mimicked 4-OI-induced actions in OB-6 cells. Importantly, 4-OI was ineffective against H₂O₂ in Keap1-knockout cells. Collectively, 4-OI efficiently activates Nrf2 signaling to inhibit H₂O₂-induced oxidative injury and death of osteoblasts.

A Novel Approach to Safer Glucocorticoid Receptor-Targeted Anti-lymphoma Therapy via REDD1 (Regulated in Development and DNA Damage 1) Inhibition

Glucocorticoids are widely used for therapy of hematologic malignancies. Unfortunately, chronic treatment with glucocorticoids commonly leads to adverse effects including skin and muscle atrophy and osteoporosis. We found recently that REDD1 (regulated in development and DNA damage 1) plays central role in steroid atrophy. Here, we tested whether REDD1 suppression makes glucocorticoid-based therapy of blood cancer safer. Unexpectedly, approximately 50% of top putative REDD1 inhibitors selected by bioinformatics screening of Library of Integrated Network-Based Cellular Signatures database (LINCS) were PI3K/Akt/mTOR inhibitors. We selected Wortmannin, LY294002, and AZD8055 for our studies and showed that they blocked basal and glucocorticoid-induced REDD1 expression. Moreover, all PI3K/mTOR/Akt inhibitors modified glucocorticoid receptor function shifting it toward therapeutically important transrepression. PI3K/Akt/mTOR inhibitors enhanced anti-lymphoma effects of Dexamethasone in vitro and in vivo, in lymphoma xenograft model. The therapeutic effects of PI3K inhibitor+Dexamethasone combinations ranged from cooperative to synergistic, especially in case of LY294002 and Rapamycin, used as a previously characterized reference REDD1 inhibitor. We found that coadministration of LY294002 or Rapamycin with Dexamethasone protected skin against Dexamethasone-induced atrophy, and normalized RANKL/OPG ratio indicating a reduction of Dexamethasone-induced osteoporosis. Together, our results provide foundation for further development of safer and more effective glucocorticoid-based combination therapy of hematologic malignancies using PI3K/Akt/mTOR inhibitors.

Risk of fracture according to glucocorticoid use after renal biopsy: a nationwide population-based study

Few data are available regarding fracture risk in patients treated with glucocorticoids, including patients with kidney disease. A population-based retrospective cohort study was performed using Health Insurance Review and Assessment Service database, a South Korean nationwide cohort set. This study identified 44,702 patients with diagnosis code of kidney diseases who received a renal biopsy between January 1, 2012 and December 31, 2017. A total of 8,624 patients met all study inclusion criteria. A total of 1,406 fractures of any site were observed in the study period. The glucocorticoid-exposed group had more fractures than the unexposed (14.4% vs 8.8%, P < 0.0001). Vertebral fractures were the most common, followed by upper limb, and lower limb fractures. The exposed group showed a remarkably higher hazard ratio of fracture risk (HR 6.0, 95% CI 5.01-7.23) than the unexposed group, indicating systemic glucocorticoid exposure was highly associated with fracture risk. Although HR increased at doses even less than 5 mg/day, it was independent of dose. Older age showed a significant effect on fracture risk (HR 1.2, 95% CI 1.05-1.44), even after adjusting for systemic glucocorticoid exposure. Glucocorticoids was associated with higher risk of fracture even at a low daily dose and short term exposure.

Immunosuppressive Activity of Artemisia argyi Extract and Isolated Compounds

The need for novel drugs for the treatment of autoimmune diseases is high, since available pharmaceuticals often have substantial side effects and limited efficacy. Natural products are a good starting point in the development of immunosuppressive leads. Since enhanced T cell proliferation is a common feature of autoimmune diseases, we investigated the T cell proliferation inhibitory potential of an extract library of plants used in traditional Chinese medicine. Using a newly established cell-based screening platform, an ethyl acetate extract of Artemisia argyi H.Lév. & Vaniot (Asteraceae, A. argyi) was found to suppress the proliferation of human primary T lymphocytes in vitro in an IL-2-dependent manner. Flow cytometry- and ELISA-based techniques further demonstrated that the A. argyi extract reduced the activation and function of T cells. Transcription factor analysis and flow cytometric calcium influx investigations indicated that the immunomodulatory effect was based on specific modification of T cell signaling in a non-cytotoxic manner which is mediated via the NFAT pathway and a non-sequestrant inhibition of the calcium influx. A series of guaianolide and seco-guaianolide sesquiterpene lactones, as well as a flavonoid, were identified in a previous study as the bioactive compounds in the A. argyi extract. The effects of these bioactive compounds were compared to those of the crude extract. The tested sesquiterpene lactones act via the transcription factor NFAT and NF-κB, thereby exhibiting their immunosuppressive potential, but have an overall effect on T cell biology on a more-downstream level than the crude A. argyi extract.

Gene-Specific Actions of Transcriptional Coregulators Facilitate Physiological Plasticity: Evidence for a Physiological Coregulator Code

The actions of transcriptional coregulators are highly gene-specific, that is, each coregulator is required only for a subset of the genes regulated by a specific transcription factor. These coregulator-specific gene subsets often represent selected physiological responses among multiple pathways targeted by a transcription factor. Regulating the activity of a coregulator via post-translational modifications would thus affect only a subset of the transcription factor's physiological actions. Using the context of transcriptional regulation by steroid hormone receptors, this review focuses on gene-specific actions of coregulators and evidence linking individual coregulators with specific physiological pathways. Such evidence suggests that there is a 'physiological coregulator code', which represents a fertile area for future research with important clinical implications.

Review on long-term non-renal complications of childhood nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is the most common glomerular childhood disease. A body of literature has described the long-term renal prognosis of childhood-onset idiopathic NS. However, the nonrenal outcomes have not been studied as much.

AIM

We aimed to discuss the long-term non-renal outcomes of childhood NS, highlighting studies with a follow-up period of more than 10 years.

RESULTS

We reviewed the literature and found that a number of immunosuppressive agents have stopped inflammation, stabilised the podocyte cytoskeleton and reduce proteinuria. However, prolonged treatment has frequently been associated with a high risk of renal and non-renal complications in patients with a complicated disease course, defined as frequent relapses or steroid dependency. Non-renal complications may include impaired longitudinal growth and pubertal development, undesirable fertility outcomes, ocular complications, bone mineral diseases and potential malignancies.

CONCLUSION

This review discusses and summarises the non-renal outcomes of idiopathic childhood NS.