Low catechol-O-methyltransferase and stress potentiate functional pain and depressive behavior, especially in female mice

Temporomandibular disorders and mental health: shared etiologies and treatment approaches

The biopsychosocial model suggests that temporomandibular disorders (TMDs) often coexist with mental health disorders, particularly depression and anxiety, affecting a significant portion of the global population. The interplay between TMDs and mental health disorders contributes to a complex comorbidity, perpetuating a cycle of mutual influence and reinforcement. This review investigates the neurobiological mechanisms and epidemiological evidence supporting the shared etiology of TMDs and mental health disorders, exploring potential shared vulnerabilities and bidirectional causal relationships. Shared vulnerabilities between TMDs and mental health disorders may stem from genetic and epigenetic predispositions, psychosocial factors, and behavioral aspects. Inflammatory cytokines, neurotransmitters, neurotrophins, and neuropeptides play pivotal roles in both peripheral and central sensitization as well as neuroinflammation. Brain imaging studies suggest that TMDs and mental health disorders exhibit overlapping brain regions indicative of reward processing deficits and anomalies within the triple network model. Future research efforts are crucial for developing a comprehensive understanding of the underlying mechanisms and confirming the reciprocal causal effects between TMDs and mental health disorders. This review provides valuable insights for oral healthcare professionals, stressing the importance of optimizing treatment strategies for individuals dealing with concurrent TMDs and mental health issues through a personalized, holistic, and multidisciplinary approach.

miR-374 family is a key regulator of chronic primary pain onset

Introduction

Chronic primary pain conditions (CPPCs) are linked to catecholamine activation of peripheral adrenergic receptors. Yet, catecholamine-dependent epigenetic mechanisms, such as microRNA (miRNA) regulation of mRNA transcripts, remain largely unknown.

Objectives

We sought to identify RNA species correlated with case status in 3 pain cohorts, to validate RNAs found to be dysregulated in a mouse model of CPPC onset, and to directly test the role of adrenergic receptors in miRNA regulation. Furthermore, we tested antinociceptive effects of miR-374 overexpression.

Methods

We used RNA-seq and quantitative reverse transcription polymerase chain reaction to measure RNA expression in 3 pain cohorts. Next, we validated identified RNAs with quantitative reverse transcription polymerase chain reaction in a mouse model of CPPC onset, measuring expression in plasma, peripheral (adipose, muscle, dorsal root ganglia [DRG]), and central (spinal cord) tissues. Then, we stimulated adrenergic receptors in primary adipocyte and DRG cultures to directly test regulation of microRNAs by adrenergic signaling. Furthermore, we used in vitro calcium imaging to measure the antinociceptive effects of miR-374 overexpression.

Results

We found that one miRNA family, miR-374, was downregulated in the plasma of individuals with temporomandibular disorder, fibromyalgia syndrome, or widespread pain following a motor vehicle collision. miR-374 was also downregulated in plasma, white adipose tissue, and spinal cord from mice with multisite mechanical sensitivity. miR-374 downregulation in plasma and spinal cord was female specific. Norepinephrine stimulation of primary adipocytes, but not DRG, led to decreased miR-374 expression. Furthermore, we identified tissue-specific and sex-specific changes in the expression of predicted miR-374 mRNA targets, including known (HIF1A, NUMB, TGFBR2) and new (ATXN7, CRK-II) pain targets. Finally, we demonstrated that miR-374 overexpression in DRG neurons reduced capsaicin-induced nociceptor activity.

Conclusions

Downregulation of miR-374 occurs between adrenergic receptor activation and mechanical hypersensitivity, and its adipocyte source implicates adipose signaling in nociception. Further study of miR-374 may inform therapeutic strategies for the millions worldwide who experience CPPCs.

Protective potential of Bacillus subtilis (NMCC-path-14) against extraarticular manifestations during acute and sub-acute phase of arthritis using mice model

Extra-articular manifestations (EAM), which are associated with rheumatoid arthritis (RA), affect the quality of life of patients and are one of the critical causes of early mortality. This study was aimed at investigating whether Bacillus subtilis NMCC-path-14 (1 × 108 CFU/animal/day) could serve as a valuable therapeutic agent in managing EAM using complete Freund's adjuvant (CFA) induced arthritis during acute and sub-acute phases. Arthritis was induced using intra-dermal administration of CFA in the right hind paw of mice on day 1. Dexamethasone (Dexa) (5 mg/kg/day/animal) was used as a standard treatment. Animals in Dexa and Bacillus subtilis concurrent treatment (BS-CT) received treatments on day 1. The Bacillus subtilis pre-treatment (BS-PT) group received a probiotic dose 7 days before arthritis induction. Parameters like body weight, relative organ weight, colon length, hematology, serum biochemistry, antioxidant capacity, and histopathology of liver, kidney, spleen, colon, stress-related behavioral changes, and cortisol levels were evaluated on days 7 (acute) and 14 (sub-acute). Dexa failed to manage the EAM in arthritic mice and instead exacerbated them. On the other hand, B. subtilis NMCC-path-14 significantly declined EAM with no notable side effects, highlighting its safety and effectiveness. The current data show that B. subtilis NMCC-path-14 may be an alternative option for arthritis treatment that can reduce systemic symptoms associated with arthritis. More studies are required to comprehend the underlying mechanisms of mitigating the EAM by B. subtilis NMCC-path-14.

A mouse model of chronic primary pain that integrates clinically relevant genetic vulnerability, stress, and minor injury

Chronic primary pain conditions (CPPCs) affect over 100 million Americans, predominantly women. They remain ineffectively treated, in large part because of a lack of valid animal models with translational relevance. Here, we characterized a CPPC mouse model that integrated clinically relevant genetic (catechol-O-methyltransferase; COMT knockdown) and environmental (stress and injury) factors. Compared with wild-type mice, Comt+/- mice undergoing repeated swim stress and molar extraction surgery intervention exhibited pronounced multisite body pain and depressive-like behavior lasting >3 months. Comt+/- mice undergoing the intervention also exhibited enhanced activity of primary afferent nociceptors innervating hindpaw and low back sites and increased plasma concentrations of norepinephrine and pro-inflammatory cytokines interleukin-6 (IL-6) and IL-17A. The pain and depressive-like behavior were of greater magnitude and longer duration (≥12 months) in females versus males. Furthermore, increases in anxiety-like behavior and IL-6 were female-specific. The effect of COMT genotype × stress interactions on pain, IL-6, and IL-17A was validated in a cohort of 549 patients with CPPCs, demonstrating clinical relevance. Last, we assessed the predictive validity of the model for analgesic screening and found that it successfully predicted the lack of efficacy of minocycline and the CB2 agonist GW842166X, which were effective in spared nerve injury and complete Freund's adjuvant models, respectively, but failed in clinical trials. Yet, pain in the CPPC model was alleviated by the beta-3 adrenergic antagonist SR59230A. Thus, the CPPC mouse model reliably recapitulates clinically and biologically relevant features of CPPCs and may be implemented to test underlying mechanisms and find new therapeutics.

The Fibromyalgia Pain Experience: A Scoping Review of the Preclinical Evidence for Replication and Treatment of the Affective and Cognitive Pain Dimensions

Fibromyalgia is a chronic, widespread pain disorder that is strongly represented across the affective and cognitive dimensions of pain, given that the underlying pathophysiology of the disorder is yet to be identified. These affective and cognitive deficits are crucial to understanding and treating the fibromyalgia pain experience as a whole but replicating this multidimensionality on a preclinical level is challenging. To understand the underlying mechanisms, animal models are used. In this scoping review, we evaluate the current primary animal models of fibromyalgia regarding their translational relevance within the affective and cognitive pain realms, as well as summarize treatments that have been identified preclinically for attenuating these deficits.

Transforming Growth Factor-β-Activated Kinase 1 (TAK1) Mediates Chronic Pain and Cytokine Production in Mouse Models of Inflammatory, Neuropathic, and Primary Pain

The origin of chronic pain is linked to inflammation, characterized by increased levels of proinflammatory cytokines in local tissues and systemic circulation. Transforming growth factor beta-activated kinase 1 (TAK1) is a key regulator of proinflammatory cytokine signaling that has been well characterized in the context of cancer and autoimmune disorders, yet its role in chronic pain is less clear. Here, we evaluated the ability of our TAK1 small-molecule inhibitor, takinib, to attenuate pain and inflammation in preclinical models of inflammatory, neuropathic, and primary pain. Inflammatory, neuropathic, and primary pain was modeled using intraplantar complete Freund's adjuvant (CFA), chronic constriction injury (CCI), and systemic delivery of the catechol-O-methyltransferase (COMT) inhibitor OR486, respectively. Behavioral responses evoked by mechanical and thermal stimuli were evaluated in separate groups of mice receiving takinib or vehicle prior to pain induction (baseline) and over 12 days following CFA injection, 4 weeks following CCI surgery, and 6 hours following OR486 delivery. Hindpaw edema was also measured prior to and 3 days following CFA injection. Upon termination of behavioral experiments, dorsal root ganglia (DRG) were collected to measure cytokines. We also evaluated the ability of takinib to modulate nociceptor activity via in vitro calcium imaging of neurons isolated from the DRG of Gcamp3 mice. In all 3 models, TAK1 inhibition significantly reduced hypersensitivity to mechanical and thermal stimuli and expression of proinflammatory cytokines in DRG. Furthermore, TAK1 inhibition significantly reduced the activity of tumor necrosis factor (TNF)-primed/capsaicin-evoked DRG nociceptive neurons. Overall, our results support the therapeutic potential of TAK1 as a novel drug target for the treatment of chronic pain syndromes with different etiologies. PERSPECTIVE: This article reports the therapeutic potential of TAK1 inhibitors for the treatment of chronic pain. This new treatment has the potential to provide a greater therapeutic offering to physicians and patients suffering from chronic pain as well as reduce the dependency on opioid-based pain treatments.

Inconsistent Time-Dependent Effects of Tetramethylpyrazine on Primary Neurological Disorders and Psychiatric Comorbidities

The aim of this study was to investigate the time dependent effects of tetramethylpyrazine (TMP, main activity compound of Ligusticum chuanxiong Hort) on two neurological disorders and their neuropsychiatric comorbidities. 6 Hz corneal rapid kindling was used to induce epileptogenesis and the inflammatory pain was induced by intra-articular Complete Freund's adjuvant (CFA) injection. The mechanical pain thresholds were measured using von Frey hair (D4, D11, D18, D25 after CFA first injection), and the vertical rearings of the mice was observed. To test the neuropsychiatric comorbidities, anxiety-like behaviors of mice were examined by open field and elevated plus maze tests. Two behavioral despair models, tail suspension test and forced swimming test were also used to evaluate the depressive like behaviors. The results showed that TMP administered from the initial day (D1-D35 in kindling model, D0-D14 and D0-D28 in CFA model) of modeling retarded both the developments of 6 Hz corneal rapid kindling epileptogenesis and the CFA induced inflammatory pain. In comparison, late periods administration of TMP (D21-D35 in kindling and D14-D28 in CFA model) showed no effect on the epileptogenesis and the generalized seizures (GS) of kindling, but alleviated maintenance of CFA induced inflammatory pain. Furthermore, we also found all TMP treatments from the initial day of modeling alleviated the co-morbid depressive and anxiety-like behaviors in both models; however, late periods treatments did not, either in kindling or the CFA induced inflammatory pain. BDNF/ERK signaling impairment was also tested by western blot, and the results showed that TMP administered from the initial day of modeling increased the hippocampal BDNF/ERK expression, whereas late period administration showed no effects. Overall, our findings reveal the inconsistent time dependent effects of Tetramethylpyrazine on neurological disorders and their relative neuropsychiatric comorbidities, and provide novel insight into the early application of TMP that might enhance hippocampal BDNF/ERK signaling to alleviate neuropsychiatric comorbidities in neurological diseases.