Network analysis of monoamines involved in anxiety-like behavior in a rat model of osteoarthritis.

BACKGROUND: Chronic pain is a major health problem that affects a significant number of patients, resulting in personal suffering and substantial health care costs. One of the most commonly reported causal conditions is osteoarthritis (OA). In addition to sensory symptoms, chronic pain shares an inherent overlap with mood or anxiety disorders. The involvement of the frontal cortex, striatum and nucleus accumbens, in the affective processing of pain is still poorly understood. METHODS: Male Wistar rats were divided into two groups: MIA (monoiodoacetate injected into the knee-model of OA) and sham (NaCl). Behavioral tests assessing pain, anxiety, and depressive behavior were performed at week 1, 3, 4, 6, 8, and 10. Neurochemical assays were conducted at weeks 3, 6, and 10 post-MIA injection, followed by the neurotransmitters and their metabolites correlation matrix and network analysis. RESULTS: OA animals developed rapid pain phenotype, whereas anxiety-like behavior accompanied the development of a pain phenotype from 6 week post-MIA injection. We did not detect any depressive-like behavior. Instead, immobility time measured in the forced swimming test transiently decreased at 3 weeks post-MIA in the OA group. We detected changes in noradrenaline and serotonin levels in analyzed structures at distinct time points. Network analysis revealed noradrenaline and serotonin neurotransmission changes in the nucleus accumbens, confirming it to be the key structure affected by chronic pain. CONCLUSION: Animals with chronic pain exhibit symptoms of anxiety-like behavior and we identified underlying neurochemical changes using network analysis.

Mimicking the Human Articular Joint with In Vitro Model of Neurons-Synoviocytes Co-Culture.

The development of in vitro models is essential in modern science due to the need for experiments using human material and the reduction in the number of laboratory animals. The complexity of the interactions that occur in living organisms requires improvements in the monolayer cultures. In the work presented here, neuroepithelial stem (NES) cells were differentiated into peripheral-like neurons (PLN) and the phenotype of the cells was confirmed at the genetic and protein levels. Then RNA-seq method was used to investigate how stimulation with pro-inflammatory factors such as LPS and IFNγ affects the expression of genes involved in the immune response in human fibroblast-like synoviocytes (HFLS). HFLS were then cultured on semi-permeable membrane inserts, and after 24 hours of pro-inflammatory stimulation, the levels of cytokines secretion into the medium were checked. Inserts with stimulated HFLS were introduced into the PLN culture, and by measuring secreted ATP, an increase in cell activity was found in the system. The method used mimics the condition that occurs in the joint during inflammation, as observed in the development of diseases such as rheumatoid arthritis (RA) or osteoarthritis (OA). In addition, the system used can be easily modified to simulate the interaction of peripheral neurons with other cell types.

Inhibition of anandamide breakdown reduces pain and restores LTP and monoamine levels in the rat hippocampus via the CB1 receptor following osteoarthritis.

Chronic pain is a persistent, complex condition that contributes to impaired mood, anxiety and emotional problems. Osteoarthritis (OA) is one of the major causes of chronic pain in adults and elderly people. A substantial body of evidence demonstrate that hippocampal neural circuits, especially monoamine dopamine and serotonin levels, contributes to negative affect and avoidance motivation experienced during pain. Current pharmacological strategies for OA patients are unsatisfying and the endocannabinoid system modulation might represent an alternative for the treatment of OA-related pain. In the present study, we used a rat model of osteoarthritis induced by intra-articular injection of sodium monoiodoacetate to assess, 28 days post-induction, the contribution of endocannabinoid system on the possible alteration in pain perception and affective behavior, in LTP and monoamine levels in the lateral entorhinal cortex-dentate gyrus pathway. The results show that OA-related chronic pain induces working memory impairment and depressive-like behavior appearance, diminishes LTP, decreases dopamine levels and increases serotonin levels in the rat dentate gyrus. URB597 administration (i.p., 1 mg/kg) reduces hyperalgesia and mechanical allodynia, improves recognition memory and depressive-live behavior, restores LTP and normalizes monoamine levels in the hippocampus. The effect was observed 60-120 min post-treatment and was blocked by AM251, which proves the action of URB597 via the CB1 receptor. Therefore, our study confirms the role of anandamide in OA-related chronic pain management at the behavioral and hippocampal levels. This article is part of the Special Issue on 'Advances in mechanisms and therapeutic targets relevant to pain'.

Inflammation-Driven Secretion Potential Is Upregulated in Osteoarthritic Fibroblast-Like Synoviocytes.

Osteoarthritis (OA) is one of the most common joint pathologies and a major cause of disability among the population of developed countries. It manifests as a gradual degeneration of the cartilage and subchondral part of the bone, leading to joint damage. Recent studies indicate that not only the cells that make up the articular cartilage but also the synoviocytes, which build the membrane surrounding the joint, contribute to the development of OA. Therefore, the aim of the study was to determine the response to inflammatory factors of osteoarthritic synoviocytes and to identify proteins secreted by them that may influence the progression of OA. This study demonstrated that fibroblast-like synoviocytes of OA patients (FLS-OA) respond more strongly to pro-inflammatory stimulation than cells obtained from control patients (FLS). These changes were observed at the transcriptome level and subsequently confirmed by protein analysis. FLS-OA stimulated by pro-inflammatory factors [such as lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNFα) were shown to secrete significantly more chemokines (CXCL6, CXCL10, and CXCL16) and growth factors [angiopoietin-like protein 1 (ANGPTL1), fibroblast growth factor 5 (FGF5), and insulin-like growth factor 2 (IGF2)] than control cells. Moreover, the translation of proteolytic enzymes [matrix metalloprotease 3 (MMP3), cathepsin K (CTSK), and cathepsin S (CTSS)] by FLS-OA is increased under inflammatory conditions. Our data indicate that the FLS of OA patients are functionally altered, resulting in an enhanced response to the presence of pro-inflammatory factors in the environment, manifested by the increased production of the previously mentioned proteins, which may promote further disease progression.

Antinociceptive and chondroprotective effects of prolonged ß-caryophyllene treatment in the animal model of osteoarthritis: Focus on tolerance development.

Osteoarthritis (OA) is a chronic joint disease in which cartilage degeneration leads to chronic pain. The endocannabinoid system has attracted attention as an emerging drug target for OA. However, the therapeutic potential of cannabinoids is limited by psychoactive side-effects related to CB1 activation and tolerance development for analgesic effects. ß-Caryophyllene (BCP) is a low-efficacy natural agonist of CB2 and a common constituent of human diet with well-established anti-inflammatory properties. The results presented herein show the anti-nociceptive and chondroprotective potential of BCP in an animal model of OA induced by intra-articular injection of monoiodoacetate (MIA). Behavioural assessment included pressure application measurement and kinetic weight bearing tests. Histological assessment of cartilage degeneration was quantified using OARSI scoring. Experiments established the dose-response effects of BCP and pharmacological mechanisms of the antinociceptive action dependent on CB2 and opioid receptors. Chronic BCP treatment was able to hamper cartilage degeneration without producing tolerance for the analgesic effects. The data presented herein show that BCP is able to produce both acute and prolonged antinociceptive and chondroprotective effects. Together with the safety profile and legal status of BCP, these results indicate a novel and promising disease-modifying strategy for treating OA.

Computational Approach Reveals Pronociceptive Potential of Cannabidiol in Osteoarthritis: Role of Transient Receptor Potential Channels.

Systems pharmacology employs computational and mathematical methods to study the network of interactions a drug may have within complex biological pathways. These tools are well suited for research on multitarget drugs, such as natural compounds, in diseases with complex etiologies, such as osteoarthritis (OA). The present study focuses on cannabidiol (CBD), a non-psychoactive constituent of cannabis, targeting over 60 distinct molecular targets as a potential treatment for OA, a degenerative joint disease leading to chronic pain with a neuropathic component. We successfully identified molecular targets of CBD that were relevant in the context of OA treatment with both beneficial and detrimental effects. Our findings were confirmed by in vivo and molecular studies. A key role of PPARγ in mediating the therapeutic potential of CBD was revealed, whereas upregulation of multiple transient receptor potential channels demasked CBD-induced heat hyperalgesia. Our findings pave the way for novel CBD-based therapy with improved therapeutic potential but also encourage the use of bioinformatic tools to predict the mechanism of action of CBD in different conditions. We have also created an accessible web tool for analogous analysis of CBD pharmacology in the context of any disease of interest and made it publicly available.

GP trainers and trainees - trait and gender differences in personality: implications for GP training.

This study looked at differences between established GP trainers and current GP trainees in relation to personality traits. Personality differences are particularly important for training in the UK context where the attributes of successful GPs may be evolving as the context changes, and where there is a unique one-to-one relationship between trainer and trainee. GP trainers and trainees attending educational events were invited to participate in this study by completing the NEO-PI-R, a personality measure. Correlation and multiple regression analysis demonstrated differences between these groups; some in line with expected differences relating to age and gender. Others, such as lower reported levels of emotional resilience, may be particular to this trainee population. Overall the gender differences are significant given the trend towards the feminisation of the medical profession. Generational differences may also explain some behaviour and attitudinal differences which can aid trainers' understanding of training issues. The findings have important implications for training, particularly in relation to the development of emotional resilience for GP trainees, and for recruitment. Further research correlating educational outcomes and perceived satisfaction with a GP career and GP training would indicate if trainer/trainee personality differences have a direct bearing on educational outcomes and future practice.