The genetic ablation or pharmacological inhibition of TRPV1 signalling is beneficial for the restoration of quiescent osteoclast activity in ovariectomized mice

The role of calcium ions and the transient receptor potential vanilloid (TRPV) channel in bone remodelling and orthodontic tooth movement

During orthodontic treatment, the application of orthodontic forces to the periodontal tissues leads to the activation of osteoblasts and osteoclasts, which in turn induces bone remodelling and tooth movement. Calcium is a biologically essential element that exists in the internal environment and cells as calcium ions(Ca2+). The concentration of extracellular Ca2+ can affect the activity and function of osteoblasts and osteoclasts, as well as regulate bone remodelling. In the cell, calcium ions play a crucial role in cell signal transduction, acting as a second messenger. The orthodontic force increases intracellular Ca2+ concentration through a series of cascade reactions that affect the differentiation and apoptosis of osteoblasts and osteoclasts. Calcium channels on the cell membrane are crucial for intracellular and extracellular calcium transport. Transient Receptor Potential Vanilloid (TRPV) is a calcium ion permeable and mechanosensitive receptor comprising six calcium channel subtypes, TRPV1-6. This review will focus on the crucial role of Ca2+ in bone metabolism and provide a comprehensive description of the function and mechanism of each specific TRPV channel subtype in orthodontic tooth movement and bone remodelling.

Enhanced Bone Healing Through Systemic Capsaicin Administration: An Experimental Study on Wistar Rats

BACKGROUND The healing of bone defects is a serious challenge worldwide. One branch of dentistry deals with bone defects. Capsaicin has anti-inflammatory, anti-oxidative, and cholesterol-reducing effects. The aim of this study was to evaluate the effects of systemic capsaicin administered at different doses on bone healing. MATERIAL AND METHODS A total of 32 male wistar rats was used, their weight varying between 250 and 300 g. The rats were randomly divided into 4 groups of 8 rats each. The analyses served to evaluate the effect on healing of different doses of capsaicin and grafts. A significant increase was observed in the number of osteoblasts in the capsaicin-applied groups, compared with the control group. RESULTS The analyses served to evaluate the effect on healing of different doses of capsaicin and grafts. A significant increase was observed in the number of osteoblasts in the capsaicin-applied groups, compared with that of the control group. The inflammation scores showed a significant difference only in the control group and in the group administered with 50 mg/kg capsaicin (P=0.010). The osteoclast counts were significantly different between all groups. CONCLUSIONS As a result of the analyses, positive effects on bone healing were observed when capsaicin 0.25 mg/kg and 0.50 mg/kg was administered intraperitoneally. However, more studies are needed for more accurate information.

Classical cannabinoid receptors as target in cancer-induced bone pain: a systematic review, meta-analysis and bioinformatics validation

To test the hypothesis that genetic and pharmacological modulation of the classical cannabinoid type 1 (CB1) and 2 (CB2) receptors attenuate cancer-induced bone pain, we searched Medline, Web of Science and Scopus for relevant skeletal and non-skeletal cancer studies from inception to July 28, 2022. We identified 29 animal and 35 human studies. In mice, a meta-analysis of pooled studies showed that treatment of osteolysis-bearing males with the endocannabinoids AEA and 2-AG (mean difference [MD] - 24.83, 95% confidence interval [95%CI] - 34.89, - 14.76, p < 0.00001) or the synthetic cannabinoid (CB) agonists ACPA, WIN55,212-2, CP55,940 (CB1/2-non-selective) and AM1241 (CB2-selective) (MD - 28.73, 95%CI - 45.43, - 12.02, p = 0.0008) are associated with significant reduction in paw withdrawal frequency. Consistently, the synthetic agonists AM1241 and JWH015 (CB2-selective) increased paw withdrawal threshold (MD 0.89, 95%CI 0.79, 0.99, p < 0.00001), and ACEA (CB1-selective), AM1241 and JWH015 (CB2-selective) reduced spontaneous flinches (MD - 4.85, 95%CI - 6.74, - 2.96, p < 0. 00001) in osteolysis-bearing male mice. In rats, significant increase in paw withdrawal threshold is associated with the administration of ACEA and WIN55,212-2 (CB1/2-non-selective), JWH015 and AM1241 (CB2-selective) in osteolysis-bearing females (MD 8.18, 95%CI 6.14, 10.21, p < 0.00001), and treatment with AM1241 (CB2-selective) increased paw withdrawal thermal latency in males (mean difference [MD]: 3.94, 95%CI 2.13, 5.75, p < 0.0001), confirming the analgesic capabilities of CB1/2 ligands in rodents. In human, treatment of cancer patients with medical cannabis (standardized MD - 0.19, 95%CI - 0.35, - 0.02, p = 0.03) and the plant-derived delta-9-THC (20 mg) (MD 3.29, CI 2.24, 4.33, p < 0.00001) or its synthetic derivative NIB (4 mg) (MD 2.55, 95%CI 1.58, 3.51, p < 0.00001) are associated with reduction in pain intensity. Bioinformatics validation of KEGG, GO and MPO pathway, function and process enrichment analysis of mouse, rat and human data revealed that CB1 and CB2 receptors are enriched in a cocktail of nociceptive and sensory perception, inflammatory, immune-modulatory, and cancer pathways. Thus, we cautiously conclude that pharmacological modulators of CB1/2 receptors show promise in the treatment of cancer-induced bone pain, however further assessment of their effects on bone pain in genetically engineered animal models and cancer patients is warranted.

Transient receptor potential vanilloid 1: A potential therapeutic target for the treatment of osteoarthritis and rheumatoid arthritis

This study aims to determine the molecular mechanisms and analgesic effects of transient receptor potential vanilloid 1 (TRPV1) in the treatments of osteoarthritis (OA) and rheumatoid arthritis (RA). We summarize and analyse current studies regarding the biological functions and mechanisms of TRPV1 in arthritis. We search and analyse the related literature in Google Scholar, Web of Science and PubMed databases from inception to September 2023 through the multi-combination of keywords like 'TRPV1', 'ion channel', 'osteoarthritis', 'rheumatoid arthritis' and 'pain'. TRPV1 plays a crucial role in regulating downstream gene expression and maintaining cellular function and homeostasis, especially in chondrocytes, synovial fibroblasts, macrophages and osteoclasts. In addition, TRPV1 is located in sensory nerve endings and plays an important role in nerve sensitization, defunctionalization or central sensitization. TRPV1 is a non-selective cation channel protein. Extensive evidence in recent years has established the significant involvement of TRPV1 in the development of arthritis pain and inflammation, positioning it as a promising therapeutic target for arthritis. TRPV1 likely represents a feasible therapeutic target for the treatment of OA and RA.

Nociceptor mechanisms underlying pain and bone remodeling via orthodontic forces: toward no pain, big gain

Orthodontic forces are strongly associated with pain, the primary complaint among patients wearing orthodontic braces. Compared to other side effects of orthodontic treatment, orthodontic pain is often overlooked, with limited clinical management. Orthodontic forces lead to inflammatory responses in the periodontium, which triggers bone remodeling and eventually induces tooth movement. Mechanical forces and subsequent inflammation in the periodontium activate and sensitize periodontal nociceptors and produce orthodontic pain. Nociceptive afferents expressing transient receptor potential vanilloid subtype 1 (TRPV1) play central roles in transducing nociceptive signals, leading to transcriptional changes in the trigeminal ganglia. Nociceptive molecules, such as TRPV1, transient receptor potential ankyrin subtype 1, acid-sensing ion channel 3, and the P2X3 receptor, are believed to mediate orthodontic pain. Neuropeptides such as calcitonin gene-related peptides and substance P can also regulate orthodontic pain. While periodontal nociceptors transmit nociceptive signals to the brain, they are also known to modulate alveolar bone remodeling in periodontitis. Therefore, periodontal nociceptors and nociceptive molecules may contribute to the modulation of orthodontic tooth movement, which currently remains undetermined. Future studies are needed to better understand the fundamental mechanisms underlying neuroskeletal interactions in orthodontics to improve orthodontic treatment by developing novel methods to reduce pain and accelerate orthodontic tooth movement-thereby achieving "big gains with no pain" in clinical orthodontics.

Hemoglobin is associated with BMDs and risk of the 10-year probability of fractures in patients with type 2 diabetes mellitus

Purpose

This study aimed to investigate the associations between hemoglobin (HGB) levels and bone mineral density (BMD) and fracture risk in type 2 diabetes mellitus(T2DM) population of different ages.

Method

This cross-sectional study included 641 patients with T2DM (57.9% males). BMD of the femoral neck (FN), total hip (TH), and lumbar spine (LS) were measured using dual-energy X-ray absorptiometry. The 10-year probability of fracture was assessed using a fracture risk assessment tool (FRAX). HGB and other biochemical indices were measured in a certified laboratory at our hospital. Statistical analysis was performed using SPSS 26.0 and R language (R version 4.1.0). Generalized additive models (GAMs) were used to identify the associations between HGB and BMD and fracture risk.

Results

Patients with osteoporosis have lower HGB levels than the non-osteoporotic population and lower FN BMD in patients with anemia than in the non-anemic population. In patients with T2DM, there was sex- and age-related variability in the correlation between HGB levels and BMDs and fracture risk. In older men, HGB level was an independent determinant of BMD and was positively correlated with FN and TH BMD. In non-older women, HGB level was an independent determinant of BMD and fracture risk, positively associated with BMDs and negatively associated with 10-year probability of fracture risk. GAMs revealed a positive linear association between HGB level and BMDs in non-older female patients but not in older male patients.

Conclusion

Our study provides a new perspective on the association of HGB level and BMDs with fracture risk. Relatively high HGB levels are a protective factor for bone quality in patients with T2DM. However, the bone-protective effect of HGB is influenced by age and sex and persists only in older men and non-older women with T2DM.

Substance P aggravates ligature-induced periodontitis in mice

Periodontitis is one of the most common oral diseases in humans, affecting over 40% of adult Americans. Pain-sensing nerves, or nociceptors, sense local environmental changes and often contain neuropeptides. Recent studies have suggested that nociceptors magnify host response and regulate bone loss in the periodontium. A subset of nociceptors projected to periodontium contains neuropeptides, such as calcitonin gene-related peptide (CGRP) or substance P (SP). However, the specific roles of neuropeptides from nociceptive neural terminals in periodontitis remain to be determined. In this study, we investigated the roles of neuropeptides on host responses and bone loss in ligature-induced periodontitis. Deletion of tachykinin precursor 1 (Tac1), a gene that encodes SP, or treatment of gingiva with SP antagonist significantly reduced bone loss in ligature-induced periodontitis, whereas deletion of calcitonin related polypeptide alpha (Calca), a gene that encodes CGRP, showed a marginal role on bone loss. Ligature-induced recruitment of leukocytes, including neutrophils, and increase in cytokines leading to bone loss in periodontium was significantly less in Tac1 knockout mice. Furthermore, intra-gingival injection of SP, but not neurokinin A, induced a vigorous inflammatory response and osteoclast activation in alveolar bone and facilitated bone loss in ligature-induced periodontitis. Altogether, our data suggest that SP plays significant roles in regulating host responses and bone resorption in ligature-induced periodontitis.

The Impact of Plasma Membrane Ion Channels on Bone Remodeling in Response to Mechanical Stress, Oxidative Imbalance, and Acidosis

The extracellular milieu is a rich source of different stimuli and stressors. Some of them depend on the chemical–physical features of the matrix, while others may come from the ‘outer’ environment, as in the case of mechanical loading applied on the bones. In addition to these forces, a plethora of chemical signals drives cell physiology and fate, possibly leading to dysfunctions when the homeostasis is disrupted. This variety of stimuli triggers different responses among the tissues: bones represent a particular milieu in which a fragile balance between mechanical and metabolic demands should be tuned and maintained by the concerted activity of cell biomolecules located at the interface between external and internal environments. Plasma membrane ion channels can be viewed as multifunctional protein machines that act as rapid and selective dual-nature hubs, sensors, and transducers. Here we focus on some multisensory ion channels (belonging to Piezo, TRP, ASIC/EnaC, P2XR, Connexin, and Pannexin families) actually or potentially playing a significant role in bone adaptation to three main stressors, mechanical forces, oxidative stress, and acidosis, through their effects on bone cells including mesenchymal stem cells, osteoblasts, osteoclasts, and osteocytes. Ion channel-mediated bone remodeling occurs in physiological processes, aging, and human diseases such as osteoporosis, cancer, and traumatic events.

CB2 Receptor as Emerging Anti-Inflammatory Target in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a very severe X-linked dystrophinopathy. It is due to a mutation in the DMD gene and causes muscular degeneration in conjunction with several secondary co-morbidities, such cardiomyopathy and respiratory failure. DMD is characterized by a chronic inflammatory state, and corticosteroids represent the main therapy for these patients. To contradict drug-related side effects, there is need for novel and more safe therapeutic strategies. Macrophages are immune cells stringently involved in both physiological and pathological inflammatory processes. They express the CB2 receptor, one of the main elements of the endocannabinoid system, and have been proposed as an anti-inflammatory target in several inflammatory and immune diseases. We observed a lower expression of the CB2 receptor in DMD-associated macrophages, hypothesizing its involvement in the pathogenesis of this pathology. Therefore, we analyzed the effect of JWH-133, a CB2 receptor selective agonist, on DMD-associated primary macrophages. Our study describes the beneficial effect of JWH-133 in counteracting inflammation by inhibiting pro-inflammatory cytokines release and by directing macrophages' phenotype toward the M2 anti-inflammatory one.

Gender-specific effects of capsiate supplementation on body weight and bone mineral density: a randomized, double-blind, placebo-controlled study in slightly overweight women

INTRODUCTION

Overweight and obesity are highly prevalent conditions associated with premature morbidity and mortality worldwide. Capsiate, a nonpungent analogue of capsaicin, binds to TRP vanilloid 1 (TRPV1) receptor, which is involved in adipogenesis, and could be effective as a weight-lowering agent.

METHODS

Eighteen slightly overweight women were enrolled in this randomized, double-blind, placebo-controlled study. Nine patients were included in the capsiate intervention group and received 9 mg/day of capsinoids and 9 patients received placebo for 8 weeks. All patients underwent weight and waist circumference assessment before and after treatment. Body composition and bone mineral density (BMD) were also detected by dual-energy X-ray absorptiometry (DXA).

RESULTS

Fourteen patients completed the study. The treatment with capsiate or placebo for 8 weeks was not associated with significant changes in weight or waist circumference. After treatment, there was a significant improvement in BMD values measured at the spine in the capsiate group (1.158 vs 1.106 g/cm², + 4.7%; p = 0.04), but not in the group treated with placebo. Similarly, the capsiate group showed a 9.1% increase (p = 0.05) in the adipose tissue and an 8.5% decrease in lean mass measured at the supraclavicular level, whereas these changes were not statistically significant in the placebo group.

CONCLUSIONS

Treatment with capsiate for 8 weeks led to negligible changes in body weight in a small sample of slightly overweight women, but our findings suggest a potential effect of capsaicin on bone metabolism in humans.

Examining the role of cannabinoids on osteoporosis: a review

PURPOSE

Prior research studies have shown that the endocannabinoid system, influenced by CBD and THC, plays a role in bone remodeling. As both the research on cannabis and use of cannabis continue to grow, novel medicinal uses of both its constituents as well as the whole plant are being discovered. This review examines the role of cannabinoids on osteoporosis, more specifically, the endocannabinoid system and its role in bone remodeling and the involvement of the cannabinoid receptors 1 and 2 in bone health, as well as the effects of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and synthetic cannabinoids on bone.

METHODS

A comprehensive literature search of online databases including PUBMED was utilized.

RESULTS

A total of 29 studies investigating the effects of cannabis and/or its constituents as well as the activation or inactivation of cannabinoid receptors 1 and 2 were included and discussed.

CONCLUSION

While many of the mechanisms are still not yet fully understood, both preclinical and clinical studies show that the effects of cannabis mediated through the endocannabinoid system may prove to be an effective treatment option for individuals with osteoporosis.

Pharmacokinetics and local tissue response to local instillation of vocacapsaicin, a novel capsaicin prodrug, in rat and rabbit osteotomy models

Vocacapsaicin is a novel prodrug of trans-capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) being developed as a nonopioid, long-lasting, site-specific treatment for postsurgical pain management. The objective of these studies was to examine the safety and tolerability of vocacapsaicin in an osteotomy model in two animal species and to evaluate bone healing parameters. Rats undergoing unilateral femoral osteotomy received a single perioperative administration (by instillation) of vocacapsaicin (vehicle, 0.15, 0.3, and 0.6 mg/kg). Rabbits undergoing unilateral ulnar osteotomy received a single perioperative administration (by infiltration and instillation) of vocacapsaicin (vehicle, 0.256 and 0.52 mg) alone or in combination with 0.5% ropivacaine. Clinical signs, body weights, food consumption, radiography, histopathologic examinations, ex vivo bone mineral density measurements (rats only), and biomechanical testing were evaluated at 4 and 8 weeks in rats and at 2 and 10 weeks in rabbits. Plasma samples were also collected in rabbits. There were no vocacapsaicin-related effects on mortality, clinical observations, body weight, or food consumption in either species. Systemic exposure to vocacapsaicin and its metabolites, including capsaicin, was transient. In rats, vocacapsaicin was devoid of deleterious effects on bone healing parameters, and there was a trend for enhanced bone healing in rats treated with the mid-dose. In rabbits, vocacapsaicin administered alone or in combination with ropivacaine did not adversely affect bone healing parameters. In conclusion, a single perioperative administration of vocacapsaicin in unilateral osteotomy models was well tolerated, locally and systemically, supporting its continued development as a novel, nonopioid treatment for postsurgical pain management.

Calcium-Permeable Channels Cooperation for Rheumatoid Arthritis: Therapeutic Opportunities

Rheumatoid arthritis is a common autoimmune disease that results from the deposition of antibodies–autoantigens in the joints, leading to long-lasting inflammation. The main features of RA include cartilage damage, synovial invasion and flare-ups of intra-articular inflammation, and these pathological processes significantly reduce patients’ quality of life. To date, there is still no drug target that can act in rheumatoid arthritis. Therefore, the search for novel drug targets has become urgent. Due to their unique physicochemical properties, calcium ions play an important role in all cellular activities and the body has evolved a rigorous calcium signaling system. Calcium-permeable channels, as the main operators of calcium signaling, are widely distributed in cell membranes, endoplasmic reticulum membranes and mitochondrial membranes, and mediate the efflux and entry of Ca2+. Over the last century, more and more calcium-permeable channels have been identified in human cells, and the role of this large family of calcium-permeable channels in rheumatoid arthritis has gradually become clear. In this review, we briefly introduce the major calcium-permeable channels involved in the pathogenesis of RA (e.g., acid-sensitive ion channel (ASIC), transient receptor potential (TRP) channel and P2X receptor) and explain the specific roles and mechanisms of these calcium-permeable channels in the pathogenesis of RA, providing more comprehensive ideas and targets for the treatment of RA.

Preclinical and Clinical Evidence of Effect of Acid on Bone Health

Acid can have ill effect on bone health in the absence of frank clinical acidosis but affecting the bone mioneral matrix and bone cells via complex pathways botyh ascute;y and chronically. While the reaction of bone to an acid load is conserved in evolution and is adaptive, the capacity can be overwhelmed resulting in dire consequences. The preclinical an clincl evidence of the acdi effect on bone is very convincing and the clinical evidence in both association and interventiopn studies are also quite credible, The adverse effects of acid on bone is underappreoicated, under-investigated, and the potential benefits of alkali therapy is not generrally known.

The effects of cannabis and cannabinoids on the endocrine system

With the increase in cannabis use due to policy changes and areas of decriminalization, it is important to recognize the potential impact of these substances on endocrine processes. Cannabinoids have many effects by activating the endocannabinoid system. This system plays a role in the normal functioning of nearly every organ and consists of the body's natural endocannabinoids, the cannabinoid receptors, and the enzymes and processes that regulate endocannabinoids. Exogenous cannabinoids such as Δ9-tetrahydrocannabinol (THC) are known to act through cannabinoid type 1 and 2 receptors, and have been shown to mimic endocannabinoid signaling and affect receptor expression. This review summarizes the known impacts of cannabis on thyroid, adrenal, and gonadal function in addition to glucose control, lipids, and bone metabolism, including: reduced female fertility, increased risk of adverse pregnancy outcomes, reduced sperm counts and function, lower thyroid hormone levels with acute use, blunting of stress response with chronic use, increased risk of prediabetes but lower risk of diabetes, suggested improvement of high density lipoproteins and triglycerides, and modest increase in fracture risk. The known properties of endocannabinoids, animal data, population data, and the possible benefits and concerns of cannabinoid use on hormonal function are discussed. The interconnectivity of the endocrine and endocannabinoid systems suggests opportunities for future therapeutic modalities which are an area of active investigation.

Effects and mechanisms of microenvironmental acidosis on osteoclast biology

Due to continuous bone remodeling, the bone tissue is dynamic and constantly being updated. Bone remodeling is precisely regulated by the balance between osteoblast-induced bone formation and osteoclast-induced bone resorption. As a giant multinucleated cell, formation and activities of osteoclasts are regulated by macrophage colony-stimulating factor (M-CSF), receptor activator of nuclear factor-kappaB ligand (RANKL), and by pathological destabilization of the extracellular microenvironment. Microenvironmental acidosis, as the prime candidate, is a driving force of multiple biological activities of osteoclast precursor and osteoclasts. The mechanisms involved in these processes, especially acid-sensitive receptors/channels, are of great precision and complicated. Recently, remarkable progress has been achieved in the field of acid-sensitive mechanisms of osteoclasts. It is important to elucidate the relationship between microenvironmental acidosis and excessive osteoclasts activity, which will help in understanding the pathophysiology of diseases that are associated with excess bone resorption. This review summarizes physiological consequences and in particular, potential mechanisms of osteoclast precursor or osteoclasts in the context of acidosis microenvironments.

The mechanosensory and mechanotransductive processes mediated by ion channels and the impact on bone metabolism: A systematic review

Mechanical environments were associated with alterations in bone metabolism. Ion channels present on bone cells are indispensable for bone metabolism and can be directly or indirectly activated by mechanical stimulation. This review aimed to discuss the literature reporting the mechanical regulatory effects of ion channels on bone cells and bone tissue. An electronic search was conducted in PubMed, Embase and Web of Science. Studies about mechanically induced alteration of bone cells and bone tissue by ion channels were included. Ion channels including TRP family channels, Ca²⁺ release-activated Ca²⁺ channels (CRACs), Piezo1/2 channels, purinergic receptors, NMDA receptors, voltage-sensitive calcium channels (VSCCs), TREK2 potassium channels, calcium- and voltage-dependent big conductance potassium (BK_Ca) channels, small conductance, calcium-activated potassium (SK_Ca) channels and epithelial sodium channels (ENaCs) present on bone cells and bone tissue participate in the mechanical regulation of bone development in addition to contributing to direct or indirect mechanotransduction such as altered membrane potential and ionic flux. Physiological (beneficial) mechanical stimulation could induce the anabolism of bone cells and bone tissue through ion channels, but abnormal (harmful) mechanical stimulation could also induce the catabolism of bone cells and bone tissue through ion channels. Functional expression of ion channels is vital for the mechanotransduction of bone cells. Mechanical activation (opening) of ion channels triggers ion influx and induces the activation of intracellular modulators that can influence bone metabolism. Therefore, mechanosensitive ion channels provide new insights into therapeutic targets for the treatment of bone-related diseases such as osteopenia and aseptic implant loosening.

The role of TRPV channels in osteoporosis

As the world's population ages, the treatment of osteoporosis is a major problem to be addressed. The cause of osteoporosis remains unclear. Ca²⁺ is not only an important component of bones but also plays a key role in osteoporosis treatment. Transient receptor potential vanilloid (TRPV) channels are one of the TRP channel families that is widely distributed in various organs, playing an important role in the physiological regulation of the human body. Bone formation and bone absorption may require Ca²⁺ transport via TRPV channels. It has been proven that the TRPV subtypes 1, 2, 4, 5, 6 (TRPV1, TRPV2, TRPV4, TRPV5, TRPV6) may affect bone metabolism balance through selective regulation of Ca²⁺. They significantly regulate osteoblast/osteoclast proliferation, differentiation and function. The purpose of this review is to explore the mechanisms of TRPV channels involved in regulation of the differentiation of osteoblasts and osteoclasts, as well as to discuss the latest developments in current researches, which may provide new clues and directions for an in-depth study of osteoporosis and other related bone metabolic diseases.

Role of the Endocannabinoid/Endovanilloid System in the Modulation of Osteoclast Activity in Paget's Disease of Bone

The role of the endocannabinoid/endovanilloid (EC/EV) system in bone metabolism has recently received attention. Current literature evidences the modulation of osteoclasts and osteoblasts through the activation or inhibition of cannabinoid receptors in various pathological conditions with secondary involvement of bone tissue. However, this role is still unclear in primary bone diseases. Paget's disease of the bone (PDB) could be considered a disease model for analyzing the role of the EC/EV system on osteoclasts (OCs), speculating the potential use of specific agents targeting this system for managing metabolic bone disorders. The aim of the study is to analyze OCs expression of EC/EV system in patients with PDB and to compare OCs activity between this population and healthy people. Finally, we investigate whether specific agents targeting EC/EV systems are able to modulate OCs activity in this metabolic bone disorder. We found a significant increase in cannabinoid receptor type 2 (CB2) protein expression in patients with PDB, compared to healthy controls. Moreover, we found a significant reduction in multi-nucleated tartrate-resistant acid phosphatase (TRAP)-positive OCs and resorption areas after treatment with JWH-133. CB2 could be a molecular target for reducing the activity of OCs in PDB, opening new therapeutic scenarios for the management of this condition.

Osteosarcoma in Children: Not Only Chemotherapy

Osteosarcoma (OS) is the most severe bone malignant tumor, responsible for altered osteoid deposition and with a high rate of metastasis. It is characterized by heterogeneity, chemoresistance and its interaction with bone microenvironment. The 5-year survival rate is about 67% for patients with localized OS, while it remains at 20% in case of metastases. The standard therapy for OS patients is represented by neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy. The most used chemotherapy regimen for children is the combination of high-dose methotrexate, doxorubicin, and cisplatin. Considered that the necessary administration of high-dose chemotherapy is responsible for a lot of acute and chronic side effects, the identification of novel therapeutic strategies to ameliorate OS outcome and the patients' life expectancy is necessary. In this review we provide an overview on new possible innovative therapeutic strategies in OS.

The role of small leucine zipper protein in osteoclastogenesis and its involvement in bone remodeling

Bone remodeling is critical to maintain the quality of bone tissues and to heal bone tissue injury. Osteoclasts and osteoblasts are special types of cells involved in this event. In particular, the resorption activity of mature osteoclasts is required for the formation of new bones. Human small leucine zipper protein (sLZIP) is known to induce the osteoblast differentiation of mesenchymal stem cells. However, the roles of sLZIP in osteoclast differentiation and bone remodeling have not been explored. In this study, we investigated the roles of sLZIP in regulating osteoclast formation and in the bone remodeling process using sLZIP transgenic (TG) mice. Tibiae from sLZIP TG mice contained more osteoclasts than those from wild type (WT) mice. Bone marrow-derived macrophages (BMM) from sLZIP TG mice showed increased differentiation into osteoclasts compared with BMM from WT mice. sLZIP bound to the promotor and induced the expression of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) and its target osteoclastogenic genes. To understand the role of sLZIP in bone remodeling, a bone-defect model was generated. Results of micro-CT scanning and histologic analysis demonstrated that sLZIP TG mice have faster bone formation during healing compared with WT mice. Notably, the soft callus around the defect area was replaced faster by hard callus in sLZIP TG mice than in WT mice. These findings suggest that sLZIP promotes osteoclast differentiation and plays an important role in bone remodeling.

The Role of Ca2+-NFATc1 Signaling and Its Modulation on Osteoclastogenesis

The increasing of intracellular calcium concentration is a fundamental process for mediating osteoclastogenesis, which is involved in osteoclastic bone resorption. Cytosolic calcium binds to calmodulin and subsequently activates calcineurin, leading to NFATc1 activation, a master transcription factor required for osteoclast differentiation. Targeting the various activation processes in osteoclastogenesis provides various therapeutic strategies for bone loss. Diverse compounds that modulate calcium signaling have been applied to regulate osteoclast differentiation and, subsequently, attenuate bone loss. Thus, in this review, we summarized the modulation of the NFATc1 pathway through various compounds that regulate calcium signaling and the calcium influx machinery. Furthermore, we addressed the involvement of transient receptor potential channels in osteoclastogenesis.

Transient receptor potential vanilloid 1 and 4 double knockout leads to increased bone mass in mice

Calcium balance is important in bone homeostasis. The transient receptor potential vanilloid (TRPV) channel is a nonselective cation channel permeable to calcium and is activated by various physiological and pharmacological stimuli. TRPV1 and TRPV4, in particular, have important roles in intracellular Ca²⁺ signaling and extracellular calcium homeostasis in bone cells. TRPV1 and TRPV4 separately mediate osteoclast and osteoblast differentiation, and deficiency in any of these channels leads to increased bone mass. However, it remains unknown whether bone mass increases in the absence of both TRPV1 and TRPV4. In this study, we used TRPV1 and TRPV4 double knockout (DKO) mice to evaluate their bone mass in vivo, and osteoclast and osteoblast differentiation in vitro. Our results showed that DKO mice and wild type (WT) mice had no significant difference in body weight and femur length. However, the results of dual-energy X-ray absorption, microcomputed tomography, and bone histomorphometry clearly showed that DKO mice had higher bone mass than WT mice. Furthermore, DKO mice had less multinucleated osteoclasts and had lower bone resorption. In addition, the results of cell culture using flushed bone marrow from mouse femurs and tibias showed that osteoclast differentiation was suppressed, whereas osteoblast differentiation was promoted in DKO mice. In conclusion, our results suggest that the increase in bone mass in DKO mice was induced not only by the suppression of osteoclast differentiation and activity but also by the augmentation of osteoblast differentiation and activity. Our findings reveal that both the single deficiency of TRPVs and the concurrent deficiency of TRPVs result in an increase in bone mass. Furthermore, our data showed that DKO mice and single KO mice had varying approaches to osteoclast and osteoblast differentiation in vitro, and therefore, it is important to conduct further studies on TRPVs regarding the increase in bone mass to explore not only individual but also a combination of TRPVs.

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Knockout of either TRPV1 or TRPV4 results in increased bone mass in mice.

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This study evaluates the effects of TRPV1 and TRPV4 double knockout (DKO) in mice.

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Concurrent TRPV1 and TRPV4 deficiency increases mouse bone mass.

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TRPV1 and TRPV4 DKO suppresses osteoclast differentiation and activity.

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TRPV1 and TRPV4 DKO enhances osteoblast differentiation and activity.

The Role of Nerves in Skeletal Development, Adaptation, and Aging

The skeleton is well-innervated, but only recently have the functions of this complex network in bone started to become known. Although our knowledge of skeletal sensory and sympathetic innervation is incomplete, including the specific locations and subtypes of nerves in bone, we are now able to reconcile early studies utilizing denervation models with recent work dissecting the molecular signaling between bone and nerve. In total, sensory innervation functions in bone much as it does elsewhere in the body-to sense and respond to stimuli, including mechanical loading. Similarly, sympathetic nerves regulate autonomic functions related to bone, including homeostatic remodeling and vascular tone. However, more study is required to translate our current knowledge of bone-nerve crosstalk to novel therapeutic strategies that can be effectively utilized to combat skeletal diseases, disorders of low bone mass, and age-related decreases in bone quality.

Cannabinoid receptors in osteoporosis and osteoporotic pain: a narrative update of review

OBJECTIVE

Osteoporosis is a skeletal disease with decreased bone mass and alteration in microarchitecture of bone tissue, and these changes put patients in risk of bone fracture. As a common symptom of osteoporosis and complication of osteoporotic fracture, chronic pain is a headache for clinicians. Nonsteroidal anti-inflammatory drugs (NSAIDs), selective COX-2 inhibitors and opioid drugs can temporarily reduce osteoporotic pain but have relevant side effects, such as addiction, tolerability and safety. The review summarized the recent advancements in the study of CB receptors in osteoporosis and osteoporotic pain and related mechanisms.

KEY FINDINGS

Recent studies indicated the two nociceptive receptors, cannabinoid receptor (CB) and transient receptor potential vanilloid type 1 (TRPV1) channel, are co-expressed in bone cells and play important role in the metabolism of bone cells, suggesting that dualtargeting these 2 receptors/channel may provide a novel approach for osteoporotic pain. In addition, both CB receptor and TRPV1 channel are found to be expressed in the glial cells which play vital role in mediating inflammation, chronic pain and metabolism of bone cells, suggesting a role of glial cells inosteoporotic pain.

SUMMARY

Multiple-targeting against glial cells, CB receptors and TRPV1 channel may be one effective therapeutic strategy for osteoporotic pain in the future, following the elucidation of the complicated mechanism.

The Endocannabinoid/Endovanilloid System in Bone: From Osteoporosis to Osteosarcoma

Bone is a dynamic tissue, whose homeostasis is maintained by a fine balance between osteoclast (OC) and osteoblast (OB) activity. The endocannabinoid/endovanilloid (EC/EV) system’s receptors are the cannabinoid receptor type 1 (CB1), the cannabinoid receptor type 2 (CB2), and the transient receptor potential cation channel subfamily V member 1 (TRPV1). Their stimulation modulates bone formation and bone resorption. Bone diseases are very common worldwide. Osteoporosis is the principal cause of bone loss and it can be caused by several factors such as postmenopausal estrogen decrease, glucocorticoid (GC) treatments, iron overload, and chemotherapies. Studies have demonstrated that CB1 and TRPV1 stimulation exerts osteoclastogenic effects, whereas CB2 stimulation has an anti-osteoclastogenic role. Moreover, the EC/EV system has been demonstrated to have a role in cancer, favoring apoptosis and inhibiting cell proliferation. In particular, in bone cancer, the modulation of the EC/EV system not only reduces cell growth and enhances apoptosis but it also reduces cell invasion and bone pain in mouse models. Therefore, EC/EV receptors may be a useful pharmacological target in the prevention and treatment of bone diseases. More studies to better investigate the biochemical mechanisms underlining the EC/EV system effects in bone are needed, but the synthesis of hybrid molecules, targeting these receptors and capable of oppositely regulating bone homeostasis, seems to be a promising and encouraging prospective in bone disease management.

Bortezomib and endocannabinoid/endovanilloid system: a synergism in osteosarcoma

Osteosarcoma is the most common primary malignant tumor of bone in children and adolescents. Bortezomib (BTZ) is an approved anticancer drug, classified as a selective reversible inhibitor of the ubiquitin-dependent proteasome system, that leads to cancer cell cycle arrest and apoptosis reducing the invasion ability of Osteosarcoma cells in vitro. It also regulates the RANK/RANKL/OPG system, involved in the pathogenesis of bone tumors and in cell migration. A side effect of BTZ is to induce painful sensory peripheral neuropathy which lead to cessation of therapy or dose reduction. Recently BTZ has been evaluated in combination with Cannabinoids targeting CB1 receptor, demonstrating a promising synergic effect. The Endocannabinoid/Endovanilloid (EC/EV) system includes two G protein-coupled receptors (CB1 and CB2), the Transient Potential Vanilloid 1 (TRPV1) channel and their endogenous ligands and enzymes. CB1 and CB2 are expressed mainly in Central Nervous System and Immune Peripheral cells respectively. TRPV1 is also expressed in primary sensory neurons and is involved in pain modulation. EC/EV system induces apoptosis, reduces invasion and cell proliferation in Osteosarcoma cell lines and is involved in bone metabolism. We analyzed the effects of BTZ, alone and in combination with selective agonists at CB2 (JWH-133) and TRPV1 (RTX) receptors, in the Osteosarcoma cell line (HOS) on Apoptosis, Cell Cycle progression, migration and bone balance. We observed that the stimulation of CB2 and TRPV1 receptors increase the efficacy of BTZ in inducing apoptosis and reducing invasion, cell cycle progression and by modulating bone balance. These data suggest the possibility to use BTZ, in combination with EC/EV agonists, in Osteosarcoma therapy reducing its dose and its side effects.

Antibiotic-induced microbiota perturbation causes gut endocannabinoidome changes, hippocampal neuroglial reorganization and depression in mice

The microbiota-gut-brain axis (MGBA) regulates the reciprocal interaction between chronic inflammatory bowel and psychiatric disorders. This interaction involves multiple pathways that are highly debated. We examined the behavioural, biochemical and electrophysiological alterations, as well as gut microbiota composition in a model of antibiotic-induced experimental dysbiosis. Inflammation of the small intestine was also assessed. Mice were exposed to a mixture of antimicrobials for 2weeks. Afterwards, they received Lactobacillus casei DG (LCDG) or a vehicle for up to 7days via oral gavage. Perturbation of microbiota was accompanied by a general inflammatory state and alteration of some endocannabinoidome members in the gut. Behavioural changes, including increased immobility in the tail suspension test and reduced social recognition were observed, and were associated with altered BDNF/TrkB signalling, TRPV1 phosphorylation and neuronal firing in the hippocampus. Moreover, morphological rearrangements of non-neuronal cells in brain areas controlling emotional behaviour were detected. Subsequent probiotic administration, compared with vehicle, counteracted most of these gut inflammatory, behavioural, biochemical and functional alterations. Interestingly, levels of Lachnospiraceae were found to significantly correlate with the behavioural changes observed in dysbiotic mice. Our findings clarify some of the biomolecular and functional modifications leading to the development of affective disorders associated with gut microbiota alterations.

The skeletal endocannabinoid system: clinical and experimental insights

Recently, there has been a rapidly growing interest in the role of cannabinoids in the regulation of skeletal remodeling and bone mass, addressed in basic, translational and clinical research. Since the first publications in 2005, there are more than 1000 publications addressing the skeletal endocannabinoid system. This review focuses on the roles of the endocannabinoid system in skeletal biology via the cannabinoid receptors CB1, CB2 and others. Endocannabinoids play important roles in bone formation, bone resorption and skeletal growth, and are sometimes age, gender, species and strain dependent. Controversies in the literature and potential therapeutic approaches targeting the endocannabinoid system in skeletal disorders are also discussed.

Anti-proliferative, pro-apoptotic and anti-invasive effect of EC/EV system in human osteosarcoma

Osteosarcoma is the most common and aggressive bone tumor in children. The Endocannabinoid/Endovanilloid system has been proposed as anticancer target in tumor of different origins. This system is composed of two receptors (CB1 and CB2), the Transient Potential Vanilloid 1 (TRPV1) channel and their ligands and enzymes. CB1 is expressed mainly in central nervous system while CB2 predominantly on immune and peripheral cells. We investigated the effects of JWH-133 (CB2 agonist) and RTX (TRPV1 agonist) in six human Osteosarcoma cell lines: MG-63, U-2OS, MNNG/HOS, Saos-2, KHOS/NP, Hs888Lu, by Apoptosis and Migration-Assay. We also compared the effects of these compounds on Caspase-3, AKT, MMP-2 and Notch-1 regulation by Q-PCR and Western Blotting.

We observed an anti-proliferative, pro-apoptotic, anti-invasive effect. Our results show that both CB2 stimulation and TRPV1 activation, in different Osteosarcoma cell lines, can act on the same pathways to obtain the same effect, indicating the Endocannabinoid/Endovanilloid system as a new therapeutic target in Osteosarcoma.

TRPV1 deletion impaired fracture healing and inhibited osteoclast and osteoblast differentiation

Fracture healing, in which osteoclasts and osteoblasts play important roles, has drawn much clinical attention. Osteoclast deficiency or decreased osteoblast activity will impair fracture healing. TRPV1 is a member of the Ca2+ permeable cation channel subfamily, and pharmacological inhibition of TRPV1 prevents ovariectomy-induced bone loss, which makes TRPV1 a potential target for osteoporosis. However, whether long term TRPV1 inhibition or TRPV1 deletion will affect the fracture healing process is unclear. In this study, we found that the wild-type mice showed a well-remodeled fracture callus, whereas TRPV1 knockout mice still had an obvious fracture gap with unresorbed soft-callus 4 weeks post-fracture. The number of osteoclasts was reduced in the TRPV1 knockout fracture callus, and osteoclast formation and resorption activity were also impaired in vitro. TRPV1 deletion decreased the calcium oscillation frequency and peak cytoplasmic concentration in osteoclast precursors, subsequently reducing the expression and nuclear translocation of NFATc1 and downregulating DC-stamp, cathepsin K, and ATP6V. In addition, TRPV1 deletion caused reduced mRNA and protein expression of Runx2 and ALP in bone marrow stromal cells (BMSCs) and reduced calcium deposition in vitro. Our results suggest that TRPV1 deletion impairs fracture healing, and inhibited osteoclastogenesis and osteogenesis.

PKCβII-mediated cross-talk of TRPV1/CB2 modulates the glucocorticoid-induced osteoclast overactivity

In this study, we investigated the role of the endovanilloid/endocannabinoid system in the glucocorticoid-induced osteoclast overactivity. Receptorial and enzymatic component of the endovanilloid/endocannabinoid system are expressed in bone cells, and dysregulated when bone mass is reduced. Moreover, blockade or desensitization of vanilloid receptor 1 (TRPV1) and/or stimulation of cannabinoid receptor 2 (CB2) are beneficial for reducing number and activity of the bone cells modulating resorption, the osteoclasts. We have treated in vitro healthy woman derived osteoclasts with methylprednisolone in presence or not of CB2 or TRPV1 agonists/antagonists, analysing the effect on osteoclast function and morphology through a multidisciplinary approach. Moreover, a treatment with a protein kinase C inhibitor to evaluate osteoclast activity and endovanilloid/endocannabinoid component expression levels was performed in osteoclasts derived from healthy subjects in presence of not of methylprednisolone. Our results show, for the first time, that the endovanilloid/endocannabinoid system is dysregulated by the treatment with methylprednisolone, that the osteoclast activity is increased and that pharmacological compounds stimulating CB2 or inhibiting TRPV1 might reduce, possible inhibiting protein kinase C beta II, the methylprednisolone-induced osteoclast over-activation, suggesting their therapeutic use for protecting from the glucocorticoid-induced bone mass loss.

From Phytocannabinoids to Cannabinoid Receptors and Endocannabinoids: Pleiotropic Physiological and Pathological Roles Through Complex Pharmacology

Apart from having been used and misused for at least four millennia for, among others, recreational and medicinal purposes, the cannabis plant and its most peculiar chemical components, the plant cannabinoids (phytocannabinoids), have the merit to have led humanity to discover one of the most intriguing and pleiotropic endogenous signaling systems, the endocannabinoid system (ECS). This review article aims to describe and critically discuss, in the most comprehensive possible manner, the multifaceted aspects of 1) the pharmacology and potential impact on mammalian physiology of all major phytocannabinoids, and not only of the most famous one Δ9-tetrahydrocannabinol, and 2) the adaptive pro-homeostatic physiological, or maladaptive pathological, roles of the ECS in mammalian cells, tissues, and organs. In doing so, we have respected the chronological order of the milestones of the millennial route from medicinal/recreational cannabis to the ECS and beyond, as it is now clear that some of the early steps in this long path, which were originally neglected, are becoming important again. The emerging picture is rather complex, but still supports the belief that more important discoveries on human physiology, and new therapies, might come in the future from new knowledge in this field.

Neuronal TRPV1 activation regulates alveolar bone resorption by suppressing osteoclastogenesis via CGRP

The transient receptor potential vanilloid 1 (TRPV1) channel is abundantly expressed in peripheral sensory neurons where it acts as an important polymodal cellular sensor for heat, acidic pH, capsaicin, and other noxious stimuli. The oral cavity is densely innervated by afferent sensory neurons and is a highly specialized organ that protects against infections as well as physical, chemical, and thermal stresses in its capacity as the first part of the digestive system. While the function of TRPV1 in sensory neurons has been intensively studied in other organs, its physiological role in periodontal tissues is unclear. In this study we found that Trpv1^−/− mice developed severe bone loss in an experimental model of periodontitis. Chemical ablation of TRPV1-expressing sensory neurons recapitulated the phenotype of Trpv1^−/− mice, suggesting a functional link between neuronal TRPV1 signaling and periodontal bone loss. TRPV1 activation in gingival nerves induced production of the neuropeptide, calcitonin gene-related peptide (CGRP), and CGRP treatment inhibited osteoclastogenesis in vitro. Oral administration of the TRPV1 agonist, capsaicin, suppressed ligature-induced bone loss in mice with fewer tartrate-resistant acid phosphatase (TRAP)-positive cells in alveolar bone. These results suggest that neuronal TRPV1 signaling in periodontal tissue is crucial for the regulation of osteoclastogenesis via the neuropeptide CGRP.

Multi-Functional Diarylurea Small Molecule Inhibitors of TRPV1 with Therapeutic Potential for Neuroinflammation

Transient receptor potential vanilloid type 1 (TRPV1), a heat-sensitive calcium channel protein, contributes to inflammation as well as to acute and persistent pain. Since TRPV1 occupies a central position in pathways of neuronal inflammatory signaling, it represents a highly attractive potential therapeutic target for neuroinflammation. In the present work, we have in silico identified a series of diarylurea analogues for hTRPV1, of which 11 compounds showed activity in the nanomolar to micromolar range as validated by in vitro biological assays. Then, we utilized molecular docking to explore the detailed interactions between TRPV1 and the compounds to understand the contributions of the different substituent groups. Tyr511, Leu518, Leu547, Thr550, Asn551, Arg557, and Leu670 were important for the recognition of the small molecules by TRPV1. A hydrophobic group in R2 or a polar/hydrophilic group in R1 contributed significantly to the activities of the antagonists at TRPV1. In addition, the subtle different binding pose of meta-chloro in place of para-fluoro in the R2 group converted antagonism into partial agonism, as was predicted by our short-term molecular dynamics (MD) simulation and validated by bioassay. Importantly, compound 15, one of our best TRPV1 inhibitors, also showed potential binding affinity (1.39 μM) at cannabinoid receptor 2 (CB2), which is another attractive target for immuno-inflammation diseases. Furthermore, compound 1 and its diarylurea analogues were predicted to target the C-X-C chemokine receptor 2 (CXCR2), although bioassay validation of CXCR2 with these compounds still needs to be performed. This prediction from the modeling is of interest, since CXCR2 is also a potential therapeutic target for chronic inflammatory diseases. Our findings provide novel strategies to develop a small molecule inhibitor to simultaneously target two or more inflammation-related proteins for the treatment of a wide range of inflammatory disorders including neuroinflammation and neurodegenerative diseases with potential synergistic effect.

The Roles of Acidosis in Osteoclast Biology

The adverse effect of acidosis on the skeletal system has been recognized for almost a century. Although the underlying mechanism has not been fully elucidated, it appears that acidosis acts as a general stimulator of osteoclasts derived from bone marrow precursors cells and enhances osteoclastic resorption. Prior work suggests that acidosis plays a significant role in osteoclasts formation and activation via up-regulating various genes responsible for its adhesion, migration, survival and bone matrix degradation. Understanding the role of acidosis in osteoclast biology may lead to development of novel therapeutic approaches for the treatment of diseases related to low bone mass. In this review, we aim to discuss the recent investigations into the effects of acidosis in osteoclast biology and the acid-sensing molecular mechanism.

Calcium channels: the potential therapeutic targets for inflammatory bone destruction of rheumatoid arthritis

INTRODUCTION

Inflammatory bone resorption causes progressive joint destruction which ultimately leads to functional disability in rheumatoid arthritis (RA). The primary cell responsible for bone resorption is the osteoclast, which means it is a potential therapeutic target against bone destruction. In fact, experimental and clinical findings suggest that blockade of osteoclast differentiation and function is highly effective in inhibiting bone destruction in RA.

DISCUSSION AND CONCLUSION

In this report, we show several lines of experimental evidence which suggest that a variety of Ca(2+) channels are essential in osteoclast differentiation and function, and present a hypothesis that modulation of Ca(2+) channels is a highly effective therapeutic strategy in preventing osteoclast-induced structural damage in RA.

Estrogen-dependent up-regulation of TRPA1 and TRPV1 receptor proteins in the rat endometrium

Transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) receptors expressed predominantly in sensory nerves are activated by inflammatory stimuli and mediate inflammation and pain. Although they have been shown in the human endometrium, their regulation and function are unknown. Therefore, we investigated their estrogen- and progesterone-dependent alterations in the rat endometrium in comparison with the estrogen-regulated inflammatory cytokine macrophage migration inhibitory factor (MIF). Four-week-old (sexually immature) and four-month-old (sexually mature) female rats were treated with the non-selective estrogen receptor (ER) agonist diethylstilboestrol (DES), progesterone and their combination, or ovariectomized. RT-PCR and immunohistochemistry were performed to determine mRNA and protein expression levels respectively. Channel function was investigated with ratiometric [Ca(2+)]i measurement in cultured primary rat endometrial cells. Both TRP receptors and MIF were detected in the endometrium at mRNA and protein levels, and their localizations were similar. Immunostaining was observed in the immature epithelium, while stromal, glandular and epithelial positivity were observed in adults. Functionally active TRP receptor proteins were shown in endometrial cells by activation-induced calcium influx. In adults, Trpa1 and Trpv1 mRNA levels were significantly up-regulated after DES treatment. TRPA1 increased after every treatment, but TRPV1 remained unchanged following the combined treatment and ovariectomy. In immature rats, DES treatment resulted in increased mRNA expression of both channels and elevated TRPV1 immunopositivity. MIF expression changed in parallel with TRPA1/TRPV1 in most cases. DES up-regulated Trpa1, Trpv1 and Mif mRNA levels in endometrial cell cultures, but 17β-oestradiol having ERα-selective potency increased only the expression of Trpv1. We provide the first evidence for TRPA1/TRPV1 expression and their estrogen-induced up-regulation in the rat endometrium in correlation with the MIF.

Calcium Entry Through Thermosensory Channels

ThermoTRPs are unique channels that mediate Na(+) and Ca(2+) currents in response to changes in ambient temperature. In combination with their activation by other physical and chemical stimuli, they are considered key integrators of environmental cues into neuronal excitability. Furthermore, roles of thermoTRPs in non-neuronal tissues are currently emerging such as insulin secretion in pancreatic β-cells, and links to cancer. Calcium permeability through thermoTRPs appears a central hallmark for their physiological and pathological activities. Moreover, it is currently being proposed that beyond working as a second messenger, Ca(2+) can function locally by acting on protein complexes near the membrane. Interestingly, thermoTRPs can enhance and expand the inherent plasticity of signalplexes by conferring them temperature, pH and lipid regulation through Ca(2+) signalling. Thus, unveiling the local role of Ca(2+) fluxes induced by thermoTRPs on the dynamics of membrane-attached signalling complexes as well as their significance in cellular processes, are central issues that will expand the opportunities for therapeutic intervention in disorders involving dysfunction of thermoTRP channels.

CB(2) and TRPV(1) receptors oppositely modulate in vitro human osteoblast activity

In the current study, we have investigated the effect of CB2 and TRPV1 receptor ligands on in vitro osteoblasts from bone marrow of human healthy donors. A pivotal role for the endocannabinoid/endovanilloid system in bone metabolism has been highlighted. We have demonstrated a functional cross-talk between CB2 and TRPV1 in human osteoclasts, suggesting these receptors as new pharmacological target for the treatment of bone resorption disease as osteoporosis. Moreover, we have shown the presence of these receptors on human mesenchimal stem cells, hMSCs. Osteoblasts are mononucleated cells originated from hMSCs by the essential transcription factor runt-related transcription factor 2 and involved in bone formation via the synthesis and release of macrophage colony-stimulating factor, receptor activator of nuclear factor kappa-B ligand and osteoprotegerin. For the first time, we show that CB2 and TRPV1 receptors are both expressed on human osteoblasts together with enzymes synthesizing and degrading endocannabinoids/endovanilloids, and oppositely modulate human osteoblast activity in culture in a way that the CB2 receptor stimulation improves the osteogenesis whereas TRPV1 receptor stimulation inhibits it.

Endocannabinoid signaling at the periphery: 50 years after THC

In 1964, the psychoactive ingredient of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC), was isolated. Nearly 30 years later the endogenous counterparts of THC, collectively termed endocannabinoids (eCBs), were discovered: N-arachidonoylethanolamine (anandamide) (AEA) in 1992 and 2-arachidonoylglycerol (2-AG) in 1995. Since then, considerable research has shed light on the impact of eCBs on human health and disease, identifying an ensemble of proteins that bind, synthesize, and degrade them and that together form the eCB system (ECS). eCBs control basic biological processes including cell choice between survival and death and progenitor/stem cell proliferation and differentiation. Unsurprisingly, in the past two decades eCBs have been recognized as key mediators of several aspects of human pathophysiology and thus have emerged to be among the most widespread and versatile signaling molecules ever discovered. Here some of the pioneers of this research field review the state of the art of critical eCB functions in peripheral organs. Our community effort is aimed at establishing consensus views on the relevance of the peripheral ECS for human health and disease pathogenesis, as well as highlighting emerging challenges and therapeutic hopes.

Red peppers with moderate and severe pungency prevent the memory deficit and hepatic insulin resistance in diabetic rats with Alzheimer's disease

BACKGROUND

Dementia induced by β-amyloid accumulation impairs peripheral glucose homeostasis, but red pepper extract improves glucose homeostasis. We therefore evaluated whether long-term oral consumption of different red pepper extracts improves cognitive dysfunction and glucose homeostasis in type 2 diabetic rats with β-amyloid-induced dementia.

METHODS

Male diabetic rats received hippocampal CA1 infusions of β-amyloid (25-35) (AD) or β-amyloid (35-25, non-plaque forming), at a rate of 3.6 nmol/day for 14 days (Non-AD). AD rats were divided into four dietary groups receiving either 1% lyophilized 70% ethanol extracts of either low, moderate and severe pungency red peppers (AD-LP, AD-MP, and AD-SP) or 1% dextrin (AD-CON) in Western diets (43% energy as fat).

RESULTS

The ascending order of control < LSP < MSP and SSP potentiated the phosphorylation of CREB and GSK and inhibited Tau phosphorylation in the hippocampus which in turn inhibited β-amyloid accumulation. The inhibition by MP and SP reduced the memory deficit measured by passive avoidance test and water maze test. Furthermore, the accumulation of β-amyloid induced glucose intolerance, although serum insulin levels were elevated during the late phase of oral glucose tolerance test (OGTT). All of the red pepper extracts prevented the glucose intolerance in AD rats. Consistent with OGTT results, during euglycemic hyperinulinemic clamp glucose infusion rates were lower in AD-CON than Non-AD-CON with no difference in whole body glucose uptake. Hepatic glucose output at the hyperinsulinemic state was increased in AD-CON. β-amyloid accumulation exacerbated hepatic insulin resistance, but all red pepper extract treatments reversed the insulin resistance in AD rats.

CONCLUSIONS

The extracts of moderate and severe red peppers were found to prevent the memory deficit and exacerbation of insulin resistance by blocking tau phosphorylation and β-amyloid accumulation in diabetic rats with experimentally induced Alzheimer's-like dementia. These results suggest that red pepper consumption might be an effective intervention for preventing age-related memory deficit.

The pharmacology of TRP channels

This themed issue of the British Journal of Pharmacology contains review and research articles on recent advances in transient receptor potential (TRP) channel pharmacology. The review articles, written by a panel of distinguished experts, address the rapid progress in TRP channel research in fields as diverse as oncology, urology, dermatology, migraine, inflammation and pain. These reviews are complemented by original research reports focusing, among others, on the emerging roles of TRPV1 in osteoporosis and cystitis and on evodiamine as a lead structure for the development of potent TRPV1 agonists/desensitizers. Other papers highlight the differences in TRPV3 pharmacology between recombinant and native systems, the mechanisms of TRPM3 activation/inhibition and TRPP2 as a target of naringenin, a dietary flavonoid with anticancer actions. New therapeutic opportunities in pain may arise from the strategy to combine TRP channel and cell membrane impermeant sodium channel blockers to inhibit sensory nerve activity.

Trafficking of ThermoTRP Channels

ThermoTRP channels (thermoTRPs) define a subfamily of the transient receptor potential (TRP) channels that are activated by changes in the environmental temperature, from noxious cold to injurious heat. Acting as integrators of several stimuli and signalling pathways, dysfunction of these channels contributes to several pathological states. The surface expression of thermoTRPs is controlled by both, the constitutive and regulated vesicular trafficking. Modulation of receptor surface density during pathological processes is nowadays considered as an interesting therapeutic approach for management of diseases, such as chronic pain, in which an increased trafficking is associated with the pathological state. This review will focus on the recent advances trafficking of the thermoTRP channels, TRPV1, TRPV2, TRPV4, TRPM3, TRPM8 and TRPA1, into/from the plasma membrane. Particularly, regulated membrane insertion of thermoTRPs channels contributes to a fine tuning of final channel activity, and indeed, it has resulted in the development of novel therapeutic approaches with successful clinical results such as disruption of SNARE-dependent exocytosis by botulinum toxin or botulinomimetic peptides.