Emerging therapeutic targets in cancer induced bone disease: A focus on the peripheral type 2 cannabinoid receptor.

Skeletal complications are a common cause of morbidity in patients with primary bone cancer and bone metastases. The type 2 cannabinoid (Cnr2) receptor is implicated in cancer, bone metabolism and pain perception. Emerging data have uncovered the role of Cnr2 in the regulation of tumour-bone cell interactions and suggest that agents that target Cnr2 in the skeleton have potential efficacy in the reduction of skeletal complications associated with cancer. This review aims to provide an overview of findings relating to the role of Cnr2 receptor in the regulation of skeletal tumour growth, osteolysis and bone pain, and highlights the many unanswered questions and unmet needs. This review argues that development and testing of peripherally-acting, tumour-, Cnr2-selective ligands in preclinical models of metastatic cancer will pave the way for future research that will advance our knowledge about the basic mechanism(s) by which the endocannabinoid system regulate cancer metastasis, stimulate the development of a safer cannabis-based therapy for the treatment of cancer and provide policy makers with powerful tools to assess the science and therapeutic potential of cannabinoid-based therapy. Thus, offering the prospect of identifying selective Cnr2 ligands, as novel, alternative to cannabis herbal extracts for the treatment of advanced cancer patients.

Discovery of a high affinity and selective pyridine analog as a potential positron emission tomography imaging agent for cannabinoid type 2 receptor.

As part of our efforts to develop CB2 PET imaging agents, we investigated 2,5,6-substituted pyridines as a novel class of potential CB2 PET ligands. A total of 21 novel compounds were designed, synthesized, and evaluated for their potency and binding properties toward human and rodent CB1 and CB2. The most promising ligand 6a was radiolabeled with carbon-11 to yield 16 ([(11)C]RSR-056). Specific binding of 16 to CB2-positive spleen tissue of rats and mice was demonstrated by in vitro autogadiography and verified in vivo in PET and biodistribution experiments. Furthermore, 16 was evaluated in a lipopolysaccharid (LPS) induced murine model of neuroinflammation. Brain radioactivity was strikingly higher in the LPS-treated mice than the control mice. Compound 16 is a promising radiotracer for imaging CB2 in rodents. It might serve as a tool for the investigation of CB2 receptor expression levels in healthy tissues and different neuroinflammatory disorders in humans.

Effect of Rubus coreanus extracts on diabetic osteoporosis by simultaneous regulation of osteoblasts and osteoclasts.

OBJECTIVE: Diabetes mellitus has been known to be associated with a high risk of osteoporosis. Rubus coreanus Miquel, a traditional Asian herbal medicine, has various uses, such as antiobesity and antiosteoporosis treatment, among others. We investigated the effect of R. coreanus extracts on diabetic osteoporosis. METHODS: Rats were not treated, or treated with streptozotocin or R. coreanus, or ovariectomized, in various combinations. After 6 weeks of treatment, the rats were killed, and serum biochemistry, histopathology, immunohistochemistry, and semiquantitative reverse transcription polymerase chain reaction were performed. In addition, in vitro studies were performed in MC3T3-E1 and RAW 264.7 cells. RESULTS: Rats treated using R. coreanus showed significant improvement in trabecular bone histopathology. Increased expression of osteocalcin was observed in rats treated with streptozotocin and R. coreanus, whether ovariectomized or not. In addition, the expression levels of cannabinoid receptors 1 and 2 and receptor activator for nuclear factor κß ligand were increased in rats that were ovariectomized and treated with streptozotocin and R. coreanus but decreased in those treated with streptozotocin and R. coreanus alone. These results indicate that the antiosteoporotic effect of R. coreanus in postmenopausal diabetic osteoporosis is attributable to the cannabinoid receptor-dependent maximal up-regulation of osteoblastogenesis. CONCLUSIONS: The present study shows that R. coreanus may rescue diabetic osteoporotic bone loss by simultaneous alteration of activation in osteoblasts and osteoclasts. Furthermore, these effects may be partially influenced by the up-regulation of the endocannabinoid system. In conclusion, dietary R. coreanus may be of use in improving the conditions of diabetic osteoporosis.

Design and evaluation of a novel fluorescent CB2 ligand as probe for receptor visualization in immune cells.

Cannabinoid CB2 receptor has emerged as a very promising target over the last decades. We have synthesized and evaluated a new fluorescent probe designated NMP6 based on 6-methoxyisatin scaffold, which exhibited selectivity and K(i) value at hCB2 of 387 nM. We have demonstrated its ability to be an effective probe for visualization of CB2 receptor binding using confocal microscopy and a flow cytometry probe for the analysis of CB2 protein expression. Furthermore, NMP6 was easily obtained in two chemical steps from commercially available building blocks.

Effects of palmitoylethanolamide on release of mast cell peptidases and neurotrophic factors after spinal cord injury.

Spinal cord injury (SCI) has a significant impact on quality of life, expectancy, and economic burden, with considerable costs associated with primary care and loss of income. The complex pathophysiology of SCI may explain the difficulty in finding a suitable therapy for limiting neuronal injury and promoting regeneration. Although innovative medical care, advances in pharmacotherapy have been limited. The aim of the present study was to carefully investigate molecular pathways and subtypes of glial cells involved in the protective effect of PEA on inflammatory reaction associated with an experimental model of SCI. The compression model induced by applying an aneurysm clip to the spinal cord in mice is closer to the human situation, since it replicates the persistence of cord compression. Spinal cord trauma was induced in mice by the application of vascular clips to the dura via a four-level T5-T8 laminectomy. Repeated PEA administration (10 mg/kg i.p., 6 and 12 h after SCI) significantly reduced the degree of the severity of spinal cord trauma through the reduction of mast cell infiltration and activation. Moreover, PEA treatment significantly reduced the activation of microglia and astrocytes expressing cannabinoid CB(2) receptor after SCI. Importantly, the protective effect of PEA involved changes in the expression of neurotrophic factors, and in spinal cord dopaminergic function. Our results enhance our understanding about mechanisms related to the anti-inflammatory property of the PEA suggesting that this N-acylethanolamine may represent a crucial therapeutic intervention both diminishing the immune/inflammatory response and promoting the initiation of neurotrophic substance after SCI.

[Effects of electroacupuncture on the immunoreactivity of focal cutaneous CB2 receptor positive cells in arthritis rats].

OBJECTIVE: To study the effects of electroacupuncture (EA) on the immunoreactivity of focal cutaneous cannabinoid receptor 2 (CB2) positive cells in adjuvant arthritis (AA) rats. METHODS: A total of 48 adult female SD rats were randomly divided into control group (n = 12), model group (n = 12), acupoint group (n = 12), and non-acupoint group (n = 12). Arthritis model was established by hypodermic injection of complete Freund's adjuvant (CFA, 50 microL) into the left ankle joint. EA (2/ 15 Hz, 1 mA) was applied to "Huantiao" (GB 30) and "Yanglingquan" (GB 34) or two control points 5 mm left to GB30 and GB34 on the diseased side for 30 min, once every other day from the second day on after injection of CFA. Behavioral performance (pain test score) was assesed by using dorsiflexion and plantarflexion pain tests. On the 6th and 16th day after injection of CAF, the animals were anesthetized with 20% urethane (1 g/kg) for collecting the focal skin and subcutaneous tissue samples which were cut into sections (5 microm) to be stained with HE (haematoxylin & cosin) method and immunohistochemical technique respectively for observing changes of the focal cells of the inflamatory tissue and the immunoactivity of the focal cutaneous CB receptor positive cells. RESULTS: 1) In comparison with control group, the scores of both dorsiflexion and plantarflexion pain tests in model, acupoint and non-acupoint groups increased evidently after modeling (P < 0.05). Compared with model group, the scores of dorsiflexion test on the 3rd day and 5th day and plantarflexion test on the 5th day in EA-acupoint group were considerably lower (P < 0.05), and the scores of the two tests on the 3rd day and 5th day of acupoint group were also markedly lower than those of non-acupoint group (P < 0.05), suggesting a marked pain-relief after EA; while no significant differences were found between non-acupoint and model groups. 2) HE staining showed that the inflammatory cells in the dermal layer of the focus of acupoint group were evidently fewer than those of model and non-acupoint groups on the 6th day and 16th day after modeling. 3) The immunohistochemical results revealed that compared with control group, on the 6th day, the percentages of CB2 receptor positive cell area in the focus of model, non-acupoint and acupoint groups were significantly higher (P < 0.05), and that of acupoint group was markedly higher than those of model and non-acupoint groups (P < 0.05), suggesting further upregulation of the expression of CB2 receptor positive cells; no significant differences of percentages of CB2 receptor immunoreaction positive cell area among model, non-acupoint and acupoint groups were found on the 16th day (P > 0.05). CONCLUSION: EA of GB30 and GB34 can raise the immunoactivity of cutaneous CB2 receptor positive cells in the inflammatory tissue which maybe contribute to its effects in relieving inflammatory pain and suppressing focal inflammation and adjusting the balance of nociception and antinociception in AA rats.