Using The Rat Grimace Scale to Detect Orofacial Pain in Mechanically-induced Temporomandibular Joint Pain in Rats

Introduction: Orofacial pain in animal models of TMJ disorders is typically evaluated by measuring evoked reflexive responses. Since the rat grimace scale (RGS) was adopted recently to assess spontaneous pain in other pathologies, this study evaluated its effectiveness for TMJ pain in the rat. RGS was evaluated using a well-defined pain model of TMJ loading. Material and Methods: Female Holtzman rats were assigned to separate groups: loading (n=10); sham (n=4); loading with naproxen (n=4) or vehicle (n=3) on days 4 and 5 after pain developed. Jaw loading was imposed for 7 consecutive days under anesthesia by repeated mouth-opening for 1hr. Sham had no mouth-opening. Naproxen or vehicle (1mg/kg) was given intravenously. Rats were videotaped for 30mins daily after loading, and for 7 days after loading was stopped. Images were randomized and quantitatively scored using 4 action units: orbital tightening, nose/cheek flattening, ear change, whisker change. The RGS score was compared between groups using a repeated-measures ANOVA and Tukey\u27s post-hoc test. Results: Loading induced significantly higher (p\u3c0.001) RGS scores than sham on days 1 and 5. After loading was stopped, RGS scores returned to sham levels for the remainder of test days. Naproxen injection significantly lowered (p\u3c0.001) RGS scores from loading alone on day 7. Conclusion: Orofacial pain can be detected by the RGS, which may provide a useful new method to evaluate TMJ pain

Management of Orofacial Manifestations of Juvenile Idiopathic Arthritis: Interdisciplinary Consensus-Based Recommendations

Involvement of the temporomandibular joint (TMJ) is common in juvenile idiopathic arthritis (JIA). TMJ arthritis can lead to orofacial symptoms, orofacial dysfunction, and dentofacial deformity with negative impact on quality of life. Management involves interdisciplinary collaboration. No current recommendations exist to guide clinical management. We undertook this study to develop consensus-based interdisciplinary recommendations for management of orofacial manifestations of JIA, and to create a future research agenda related to management of TMJ arthritis in children with JIA. Recommendations were developed using online surveying of relevant stakeholders, systematic literature review, evidence-informed generation of recommendations during 2 consensus meetings, and Delphi study iterations involving external experts. The process included disciplines involved in the care of orofacial manifestations of JIA: pediatric rheumatology, radiology, orthodontics, oral and maxillofacial surgery, orofacial pain specialists, and pediatric dentistry. Recommendations were accepted if agreement was >80% during a final Delphi study. Three overarching management principles and 12 recommendations for interdisciplinary management of orofacial manifestations of JIA were outlined. The 12 recommendations pertained to diagnosis (n = 4), treatment of TMJ arthritis (active TMJ inflammation) (n = 2), treatment of TMJ dysfunction and symptoms (n = 3), treatment of arthritis-related dentofacial deformity (n = 2), and other aspects related to JIA (n = 1). Additionally, a future interdisciplinary research agenda was developed. These are the first interdisciplinary recommendations to guide clinical management of TMJ JIA. The 3 overarching principles and 12 recommendations fill an important gap in current clinical practice. They emphasize the importance of an interdisciplinary approach to diagnosis and management of orofacial manifestations of JIA

Anti-inflammatory Effect of Secoisolariciresinol Diglucoside (SDG) in Microglia

Secoisolariciresinol diglucoside (SDG) is the main plant lignan in flaxseed and has been thoroughly researched in the past decades due to its unique health properties. SDG has been shown to have therapeutic benefits for an array of diseases including breast and prostate cancer, hyperlipidemia, atherosclerosis, hypertension, diabetes mellitus, and radiation pneumonopathy. With a number of studies recognizing the various health benefits of SDG, few have focused on its potential anti-inflammatory effect and, specifically, its interaction with the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Thus, the aim of this study is to elucidate the interaction between SDG and NF-κB in microglial cells in vitro. Mixed rat cortical cells were cultured for 2 weeks and microglia were isolated according to a previously established protocol with slight modifications. Wells were divided between 7 groups based on pre-treatment with vehicle or SDG and treatment with water or TNF-α: Vehicle group (V) pre-treated with 2 µL PBS vehicle and treated with 10 µL H2O; SDG 50 (S50) pre-treated with 50µM and treated with 10 µL H2O; SDG 100 (S100) pre-treated with 100µM SDG and treated with H2O; Vehicle + TNF-α (V+T10) pre-treated with 2 µL PBS vehicle and treated with 10 ng/mL TNF-α; SDG 50 + TNF-α (S50+T10) pre-treated with 50µM SDG and treated with 10 ng/mL TNF-α; SDG 100 + TNF-α (S100+T10) pre-treated with 100µM SDG and treated with 10 ng/mL TNF-α; and SDG 100x2 + TNF-α (S100x2+T10) pre-treated with 100µM SDG and treated with both 100µM SDG and 10 ng/mL TNF-α. Pre-treatment occurred 4 hours prior to treatment. Groups were further divided based on harvest time at 2-, 6-, and 24-hours for different analyses. ELISA, nitrate-nitrite assay, and qPCR analyses probing for IL-1β and IL-6, nitrate and nitrite, and TNF-α and IL-1β, respectively, were performed to measure NF-κB activity. The qPCR results show a significant increase in mRNA expression of IL-1β and TNF-α after treatment with 10 ng/mL TNF-α (p \u3c .05). For both NF-κB targets, no significant difference was seen between TNF-α treatment groups with or without 50 µM SDG pre-treatment. ELISA results did not show any trends for IL-1β or IL-6. No increase in the concentrations of either NF-κB target was seen after treatment with TNF-α. Nitrate-nitrite assay results did not show significant differences between any groups (p \u3e .05). TNF-α did not elicit an increase in NO metabolite concentration in the positive control group (Veh + T10). The data obtained suggest that SDG does not have an inhibitory effect on the NF-κB pathway in microglia under these experimental conditions. After TNF-α-induced microglial activation, SDG did not significantly alter the expression of NF-κB targets. The results of this study do not support the hypothesis that SDG has an anti-inflammatory effect in microglia mediated through the NF-κB pathway. Thus, therapeutic effects of SDG in microglia may be attributed to other mechanisms. Changes in protocol may prove helpful in finding an interaction but it is recommended that future investigation of SDG’s effect on microglia focus on other pathways

Anti-inflammatory Effect of Secoisolariciresinol Diglucoside (SDG) in Microglia

Secoisolariciresinol diglucoside (SDG) is the main plant lignan in flaxseed and has been thoroughly researched in the past decades due to its unique health properties. SDG has been shown to have therapeutic benefits for an array of diseases including breast and prostate cancer, hyperlipidemia, atherosclerosis, hypertension, diabetes mellitus, and radiation pneumonopathy. With a number of studies recognizing the various health benefits of SDG, few have focused on its potential anti-inflammatory effect and, specifically, its interaction with the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Thus, the aim of this study is to elucidate the interaction between SDG and NF-κB in microglial cells in vitro. Mixed rat cortical cells were cultured for 2 weeks and microglia were isolated according to a previously established protocol with slight modifications. Wells were divided between 7 groups based on pre-treatment with vehicle or SDG and treatment with water or TNF-α: Vehicle group (V) pre-treated with 2 µL PBS vehicle and treated with 10 µL H2O; SDG 50 (S50) pre-treated with 50µM and treated with 10 µL H2O; SDG 100 (S100) pre-treated with 100µM SDG and treated with H2O; Vehicle + TNF-α (V+T10) pre-treated with 2 µL PBS vehicle and treated with 10 ng/mL TNF-α; SDG 50 + TNF-α (S50+T10) pre-treated with 50µM SDG and treated with 10 ng/mL TNF-α; SDG 100 + TNF-α (S100+T10) pre-treated with 100µM SDG and treated with 10 ng/mL TNF-α; and SDG 100x2 + TNF-α (S100x2+T10) pre-treated with 100µM SDG and treated with both 100µM SDG and 10 ng/mL TNF-α. Pre-treatment occurred 4 hours prior to treatment. Groups were further divided based on harvest time at 2-, 6-, and 24-hours for different analyses. ELISA, nitrate-nitrite assay, and qPCR analyses probing for IL-1β and IL-6, nitrate and nitrite, and TNF-α and IL-1β, respectively, were performed to measure NF-κB activity. The qPCR results show a significant increase in mRNA expression of IL-1β and TNF-α after treatment with 10 ng/mL TNF-α (p \u3c .05). For both NF-κB targets, no significant difference was seen between TNF-α treatment groups with or without 50 µM SDG pre-treatment. ELISA results did not show any trends for IL-1β or IL-6. No increase in the concentrations of either NF-κB target was seen after treatment with TNF-α. Nitrate-nitrite assay results did not show significant differences between any groups (p \u3e .05). TNF-α did not elicit an increase in NO metabolite concentration in the positive control group (Veh + T10). The data obtained suggest that SDG does not have an inhibitory effect on the NF-κB pathway in microglia under these experimental conditions. After TNF-α-induced microglial activation, SDG did not significantly alter the expression of NF-κB targets. The results of this study do not support the hypothesis that SDG has an anti-inflammatory effect in microglia mediated through the NF-κB pathway. Thus, therapeutic effects of SDG in microglia may be attributed to other mechanisms. Changes in protocol may prove helpful in finding an interaction but it is recommended that future investigation of SDG’s effect on microglia focus on other pathways

Variability in the Analgesic Response to Ibuprofen Is Associated With Cyclooxygenase Activation in Inflammatory Pain

Theken KN, Hersh EV, Lahens NF, et al. Variability in the Analgesic Response to Ibuprofen Is Associated With Cyclooxygenase Activation in Inflammatory Pain. Clinical Pharmacology & Therapeutics. 2019;106(3):632-641.The mechanisms underlying interindividual variability in analgesic efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) are not well understood. Therefore, we performed pain phenotyping, functional neuroimaging, pharmacokinetic/pharmacodynamic assessments, inflammation biomarkers, and gene expression profiling in healthy subjects who underwent surgical extraction of bony impacted third molars and were treated with ibuprofen (400 mg; N = 19) or placebo (N = 10). Analgesic efficacy was not associated with demographic or clinical characteristics, ibuprofen pharmacokinetics, or the degree of cyclooxygenase inhibition by ibuprofen. Compared with partial responders to ibuprofen (N = 9, required rescue medication within the dosing interval), complete responders (N = 10, no rescue medication) exhibited greater induction of urinary prostaglandin metabolites and serum tumor necrosis factor-α and interleukin 8. Differentially expressed genes in peripheral blood mononuclear cells were enriched for inflammation-related pathways. These findings suggest that a less pronounced activation of the inflammatory prostanoid system is associated with insufficient pain relief on ibuprofen alone and the need for additional therapeutic intervention