Paw Thickness Research Articles

Common bacterial metabolite indole directly activates nociceptive neuron through transient receptor potential ankyrin 1 channel.

Nociceptors are known to directly recognize bacterial cell wall components or secreted toxins, thereby leading to pain induced by bacterial infection. However, direct activation of nociceptors by bacterial metabolites remains unclear although bacteria produce numerous metabolites related to health and disease. In this study, we investigated whether and how a common bacterial metabolite, indole, which is produced by normal microflora of the gastrointestinal tract and oral cavity, can directly activate nociceptive sensory neurons. We found that indole elicits calcium response and evokes inward currents in subsets of dorsal root ganglia (DRG) neurons. Intraplantar (i.pl.) injection of indole produced nocifensive behaviors in adult mice, which were enhanced in complete Freund's adjuvant-induced chronic inflammatory condition. Indole increased calcitonin gene-related peptide release in DRG neurons, and i.pl. injection of indole increased hind paw thickness, suggesting its role in generation of neurogenic inflammation. These in vitro and in vivo indole-induced responses were pharmacologically blocked by transient receptor potential ankyrin 1 (TRPA1) antagonist, HC-030031, and significantly abolished in TRPA1 knockout (KO) mice, indicating that indole targets TRPA1 for its action in DRG neurons. Nocifensive licking behavior induced by the injection of live Escherichia coli was significantly decreased in tryptophanase mutant (TnaA KO) E. coli- injected mice that lack indole production, further supporting the idea that bacteria-derived indole can induce pain during infection. Identifying the mechanism of action of indole through TRPA1 provides insights into bacteria-neuron interactions and the role of bacterial metabolites in pain signaling, especially in inflammation-accompanied bacterial infection.

Oral administration of Weissella and Pediococcus sp alleviates formalin induced inflammation in rats by Cytokine Modulation

This study was designed to study the cytokine modulatory activity of three lactic acid bacteria (LAB) strains, Weisella cibaria II-1-59, Weisella confusa JMC 1093, and Pediococcus pentosaceus DSM20336 isolated from a Nigerian locally fermented food condiment; “iru” using paw oedema acute inflammatory model induced with 1% formalin in Wistar rats. Rats were distributed into six groups (A-F). Rats in Groups A were neither administered formalin nor treated with LAB, while Group B received formalin injection only. Rats in Groups C, D, and E were administered formalin and were treated orally with 2 × 107 CFU/ml of Weisella cibaria II-1-59, Weisella confusa JMC 1093, and Pediococcus pentosaceus DSM20336 respectively, while Group F received diclofenac sodium treatment following administration of formalin. The dose of LAB strain used for the oral treatment was 2 × 107 CFU/ml for all the groups while the dose of diclofenac sodium used was 150 mg/kg body weight of the rats. Paw thickness (mm) was checked at t = 0, 1, 4, 8, 24, 72, 168 and 336 h. Cytokine assay for C-reactive protein (CRP), Interleukin (IL-10) and Transforming growth factor (TGF-β) was performed on serum samples of the rats using Enzyme-linked immunosorbent assay (ELISA). Oral administration of W. cibaria II-1-59 showed the best significant decrease in the paw thickness of the rats, which was followed by P. pentosaceus DSM20336 and W. confusa JMC 1093 respectively, and was shown to be statistically significant at P<0.05. There was also a significant decrease (below standard 2000 pg/ml) in the secretion of pro-inflammatory biomarker (CRP) in all LAB treated groups at 1 hour, while there was an increase in the serum levels of anti-inflammatory cytokines IL-10 and TGF- β in Groups C-E rats which was maximally increased in W. confusa JMC 1093 treated rats. This study suggests that W. cibaria II-1-59, W. confusa JMC 1093 and P. pentosaceus DSM20336 possess anti-inflammatory potentials.
 Keywords: Inflammation, Cytokines, Weisella, Formalin, Oedema, Pediococcus

Anti-inflammatory and antipyretic potential of Arbutus andrachne L. methanolic leaf extract in rats

Objective: To explore the anti-inflammatory and antipyretic effects of methanolic leaf extract from Arbutus andrachne and its mechanism of action. Methods: Paw edema was induced by intraplantar (i.pl.) injection of λ-carrageenan (1% w/v, 100 μL/paw) while pyrexia was evoked by intraperitoneal (i.p.) injection of 20% baker's yeast (20 mL/kg body wt) in male Wistar rats. The anti-inflammatory and antipyretic effects of Arbutus andrachne methanolic leaf extract were explored by injecting rats with different doses of the plant extract (150, 300, and 600 mg/kg body wt, i.p.). Selective antagonists for transient receptor potential vanilloid-1 (TRPV1), cannabinoid receptor 1 (CB1), and alpha-2 adrenergic receptor (a2-AR) were used to unravel the extracts’ mechanism of action. Blood samples were collected from the heart of rats to measure the levels of interleukin-6 (IL-6) and prostaglandin E2 (PGE2) by enzyme-linked immunosorbent assay. Results: The extract exhibited potent anti-inflammatory activity by decreasing paw thickness and IL-6 levels. In addition, yeast-evoked pyrexia was attenuated by the extract treatment via TRPV1 and CB1 receptors and a reduction in PGE2 levels. No significant effects were found for a2-AR. Moreover, the rats that received the plant extract demonstrated similar responses to the positive control group. Conclusions: Arbutus andrachne can be a good candidate for treating inflammation and pyrexia and should be further investigated.

SZAP exerts analgesic effects on rheumatalgia in CIA rats by suppressing pain hyperalgesia and inhibiting TRPV1 and P2X3

Ethnopharmacological relevanceShexiangZhuifeng Analgesic Plaster (SZAP) is a traditional Chinese medicine and transdermal formulation composed of many Chinese herbs and active compounds. SZAP was recently approved by the China Food and Drug Administration for the treatment of pain associated with osteoarticular diseases and is preferred by most rheumatoid arthritis patients in China. However, its mechanism has not been elucidated in detail. Aim of the studyWe sought to determine the analgesic effect of SZAP in collagen-induced arthritis (CIA) rats and explore the underlying mechanisms of pain transmission, such as via the TRPV1 and P2X3 receptors. MethodsAfter CIA was established, rats were treated with SZAP for 7 days. Paw thickness, arthritis score, and haematoxylin and eosin staining were used to evaluate the effectiveness of SZAP. Paw withdrawal threshold (PWT) and tail-flick latency (TFL) were used to estimate the analgesic effect of SZAP. The levels of PGE2, BK, 5-HT, SP, and CGRP in the serum and synovium were determined using ELISA kits, and ATP in the synovium was measured using HPLC. The expression of TRPV1 and P2X3 in the DRG was detected using western blotting and immunofluorescence. TRPV1 and P2X3 agonists were further used to determine the analgesic effects of SZAP on CIA rats based on PWT and TFL. ResultsSZAP not only significantly ameliorated arthritis scores and paw thickness by improving the pathological damage of synovial joints, but also remarkably alleviated pain in CIA rats. Further, treatment with SZAP significantly reduced peripheral 5-HT, PGE2 BK, SP, CGRP, and ATP. Additionally, the expression of TRPV1 and P2X3 in the DRG was markedly downregulated by SZAP. Interestingly, the analgesic effect of SZAP was weakened (reduction of PWT and TFL) when TRPV1 and P2X3 were activated by capsaicin or α,β-meATP, respectively. ConclusionSZAP ameliorates rheumatalgia by suppressing hyperalgesia and pain transmission through the inhibition of TRPV1 and P2X3 in the DRG of CIA rats.

Standardized study of atorvastatin possible osteoarthritis disease-modifying effect in a rat model of osteoarthritis.

We studied the osteoarthritis (OA)-modifying effects of atorvastatin in an experimental OA rat model and possible underlining mechanisms. We used 62 adult male Sprague-Dawley rats (250-300 g): 32 rats were used to assess the effects of atorvastatin on surgically induced OA in the knee, and 30 rats were used to assess the potential inflammatory effects of carrageenan-induced paw edema. In the OA model, joint stiffness was assessed by measuring the knee extension angle, and pathological changes in the OA knee joint were determined by histological examination and the measurement of serum biochemical markers, including interleukin-1β (IL-1β), matrix metalloproteinase-13 (MMP-13), and reduced glutathione (GSH). In the carrageenan-induced paw edema model, both paw thickness and pain threshold were assessed in different groups. Atorvastatin significantly improved joint stiffness, pathological changes, a significant mitigation of the higher MMP-13 and IL-1β, and a significant increase of reduced GSH in OA rats. Additionally, atorvastatin significantly improved both paw thickness and pain threshold in animals. Atorvastatin is a potential OA-modifying drug that warrants further clinical investigation.

Anti-inflammatory and osteoprotective effects of Chikusetsusaponin Ⅳa on rheumatoid arthritis via the JAK/STAT signaling pathway

BackgroundRheumatoid arthritis (RA) is a common autoimmune disease, for which no economical and safe target drug treatment is available. Chikusetsusaponin Ⅳa (CS-IVa), an active compound in Panax japonicus C.A. Mey, has a good anti-inflammatory effect, but whether this compound can serve as a targeted drug for RA and the corresponding therapeutic mechanism remain unclear. PurposeTo investigate the anti-inflammatory and bone-protecting effects of CS-IVa on RA and the possible corresponding mechanisms of action. MethodsBiomarkers and underlying pathological mechanisms were examined by performing a bioinformatics analysis of RA synovial gene expression data profiles, and the feasibility of CS-IVa treatment for RA was predicted using molecular docking and molecular dynamics simulation techniques. Histomorphological and molecular biology techniques were used to verify the feasibility and molecular mechanism of CS-IVa treatment for RA in vivo using a collagen-induced arthritis (CIA) model. ResultsCS-IVa alleviated symptoms and reduced the immune organ index, arthritis index, hind paw thickness, and number of swollen joints in the foot for CIA mice. Bioinformatics analysis suggested that interferon-gamma (IFN-γ), interleukin-1 β (IL-1β), and the Janus kinase/signal transduction and activator of transcription (JAK/STAT) pathway played important roles in the pathogenesis of RA. The results of molecular docking and molecular dynamics simulations showed that CS-IVa bound effectively to IFN-γ and IL-1β and that the combined pose has good stability and flexibility. The histomorphological results showed that CS-IVa reduced joint histopathology scores, OARSI scores, and TRAP-positive cell counts. Molecular biology analysis indicated that CS-IVa reduced the concentration of inflammatory factors in the peripheral serum of CIA mice and suppressed the mRNA expression of these factors in the spleen in a dose-dependent manner. The protein expression level of the JAK/STAT pathway was also inhibited by CS-IVa. ConclusionThe results of the current study demonstrate a novel inhibitory effect of CS-IVa on inflammation and bone destruction in CIA mice, and the mechanism may be related to the JAK/STAT signaling pathway, which provides new insights into the development of CS-IVa as a therapeutic agent for RA.

In Vivo Pharmacological Testing of Herbal Drugs for Anti-Allergic and Anti-Asthmatic Properties.

Background:Asthma is a chronic inflammatory disease characterized by reversible airway obstruction, hyperresponsiveness, and remodeling. Asthma prevalence has increased significantly globally over the last decade, and it remains incurable to this date.Aims and Objectives:The present study evaluated some of the antiasthmatic medicinal plants to assess their mode of action.Materials and Method:Animal models for milk-induced leukocytosis, milk-induced eosinophilia, mast cell degranulation, clonidine-induced catalepsy, and active paw anaphylaxis were used to assess the pharmacological effects of Ammi visnaga, Medicago sativa, and Urtica dioica.Results:Mice pretreated with diazepam, methanolic extract of M. sativa, and U. dioica exhibited significant (P < 0.05) inhibition in milk-induced leukocytosis. However, only M. sativa showed statistically significant (P < 0.05) results. All plants showed a statistically significant (P < 0.05) tendency to decrease milk-induced eosinophilia. Methanolic extracts of all plants significantly (P < 0.05) protected mast cells against degranulation by clonidine. A. visnaga and U. dioica significantly (P < 0.05) protected mice against clonidine-induced catalepsy. An acute treatment by M. sativa potentiated the catalepsy, while it significantly inhibited the catalepsy (P < 0.05) upon chronic treatment. In the allergic inflammation model, methanolic extracts of all plants under study decreased paw thickness in a statistically significant manner (P < 0.05).Conclusion:All the three plants in this study demonstrated anti-inflammatory and antihistaminic effects, as well as decreased paw thickness, validate anti-allergic properties. A. visnaga showed a mast cell-stabilizing effect. A. visnaga and U. dioica inhibited the histamine-mediated clonidine-induced catalepsy from mast cells which proves the antihistaminic activity of these plants.

Isopsoralen ameliorates rheumatoid arthritis by targeting MIF

BackgroundIsopsoralen (IPRN), one of the active ingredients of Psoralea corylifolia Linn, has anti-inflammatory properties. We attempted to investigate the inhibitory effects of IPRN on rheumatoid arthritis (RA) and characterize its potential mechanism.MethodsRA fibroblast-like synoviocytes (FLSs) and mice with collagen-induced arthritis (CIA) were used as in vitro and in vivo models to analyze the antiarthritic effect of IPRN. Histological analysis of the inflamed joints from mice with CIA was performed using microcomputed tomography (micro-CT) and hematoxylin-eosin (HE) staining. RNA sequencing (RNA-Seq), network pharmacology analysis, molecular docking, drug affinity responsive target stability (DARTS) assay, and cellular thermal shift assay (CETSA) were performed to evaluate the targets of IPRN.ResultsIPRN ameliorated the inflammatory phenotype of RA FLSs by inhibiting their cytokine production, migration, invasion, and proangiogenic ability. IPRN also significantly reduced the severity of CIA in mice by decreasing paw thickness, arthritis score, bone damage, and serum inflammatory cytokine levels. A mechanistic study demonstrated that macrophage migration inhibitory factor (MIF), a key protein in the inflammatory process, was the specific target by which IPRN exerted its anti-inflammatory effects in RA FLSs.ConclusionOur study demonstrates the antiarthritic effect of IPRN, which suggests the therapeutic potential of IPRN in RA.

Systemic and topical Ginkgo biloba leaf extract (Egb-761) ameliorated rat paw inflammation in comparison to dexamethasone

Ethnopharmacological relevanceGinkgo Biloba leaf extract (Egb-761) is used for treating various inflammatory disease conditions therefore this study was performed. Aim of the studyThe present study aimed at comparing the ameliorative effects of both systemic and topical Egb-761 versus dexamethasone on carrageenan-induced hind paw inflammation in rats. Material and methodsWistar albino rats were injected with carrageenan solution in the sub-planter region of the right hind paw. Egb-761 and dexamethasone were administered systemically to two groups while Egb-761 ointment 2% and dexamethasone sodium phosphate ointment were applied topically for another two groups. Vernier Caliper was used to assess rat paw thickness. Tissue malondialdehyde (MDA), nitric oxide (NO), and tumor necrosis factor-α (TNF-α) levels have been estimated. ResultsCarrageenan induced a significant rat paw edema and inflammation noticed 1 h post-injection as well as an increase of MDA, NO, and TNF-α in the inflamed skin tissues compared to the control group. Systemic and topical administration of Egb-761 and dexamethasone resulted in a significant reduction in carrageenan-induced rat paw edema. They reduced the tissue levels of MDA, NO, and TNF-α. Dexamethasone showed a little bit superior anti-inflammatory and antioxidant efficacy over Egb-761. ConclusionOur findings indicate the possibility of the therapeutic value of Egb-761 for alleviation of local inflammation by attenuating the increased MDA, NO and TNF-α levels.

Blocking Jak/STAT signalling using tofacitinib inhibits angiogenesis in experimental arthritis

ObjectiveDuring rheumatoid arthritis (RA), the angiogenic processes, occurring with pannus-formation, may be a therapeutic target. JAK/STAT-pathway may play a role and the aim of this work was to investigate the inhibiting role of a JAK-inhibitor, tofacitinib, on the angiogenic mechanisms occurring during RA.MethodsAfter ethical approval, JAK-1, JAK-3, STAT-1, STAT-3 and VEGF expression was evaluated on RA-synovial-tissues. In vitro, endothelial cells (ECs), stimulated with 20 ng/ml of VEGF and/or 1 μM of tofacitinib, were assessed for tube formation, migration and proliferation, by Matrigel, Boyden chamber assay and ki67 gene-expression. In vivo, 32 mice received collagen (collagen-induced arthritis (CIA)) and 32 mice PBS (control). At day 19, CIA and controls mice were divided: 16 mice receiving vehicle and 16 mice receiving tofacitinib. At day 35, the arthritis score, the thickness of paw joints and the serum levels of VEGF and Ang-2 were evaluated.ResultsThe expression of JAK-1, JAK-3, STAT-1, STAT-3 and VEGF in synovial tissue of RA-patients were significantly higher than healthy controls. In vitro, tofacitinib inhibited the ECs ability to form vessels, to proliferate and to migrate. In vivo, administration of tofacitinib prevented the increase of the arthritis score, the paw thickness, the synovial vessels and VEGF and Ang-2 serum-accumulation, when compared to CIA without tofacitinib.ConclusionsWe explored the anti-angiogenic role of tofacitinib, reporting its ability to inhibit in vitro the angiogenic mechanisms of ECs and in vivo the formation of new synovial vessels, occurring in CIA model. These findings suggest that the therapeutic effect of tofacitinib during RA may be also related to its anti-angiogenic activity.

Activation of formyl peptide receptor 1 elicits therapeutic effects against collagen-induced arthritis.

Rheumatoid arthritis (RA) is an autoimmune disorder which shows production of autoantibodies, inflammation, bone erosion, swelling and pain in joints. In this study, we examined the effects of an immune‐modulating peptide, WKYMVm, that is an agonist for formyl peptide receptors (FPRs). Administration of WKYMVm into collagen‐induced arthritis (CIA) mice, an animal model for RA, attenuated paw thickness, clinical scores, production of type II collagen‐specific antibodies and inflammatory cytokines. WKYMVm treatment also decreased the numbers of TH1 and TH17 cells in the spleens of CIA mice. WKYMVm attenuated TH1 and TH17 differentiation in a dendritic cell (DC)‐dependent manner. WKYMVm‐induced beneficial effects against CIA and WKYMVm‐attenuated TH1 and TH17 differentiation were reversed by cyclosporin H but not by WRW4, indicating a crucial role of FPR1. We also found that WKYMVm augmented IL‐10 production from lipopolysaccharide‐stimulated DCs and WKYMVm failed to suppress TH1 and TH17 differentiation in the presence of anti‐IL‐10 antibody. The therapeutic administration of WKYMVm also elicited beneficial outcome against CIA. Collectively, we demonstrate that WKYMVm stimulation of FPR1 in DCs suppresses the generation of TH1 and TH17 cells via IL‐10 production, providing novel insight into the function of FPR1 in regulating CIA pathogenesis.

Anti-inflammatory role of Dunaliella salina carotenoid enrich fractions in paw oedema via down-regulation of COX-2/PGE2 pathway

Dunaliella salina (D. salina) is rich in natural potent antioxidants as beta carotene and zeaxanthin. It exhibits several therapeutic effects for diabetes, cancer, eye, and cardiovascular disorders. This study assesses the anti-inflammatory effect of beta carotene and zeaxanthin enrich fractions of D. salina against carrageenan induced inflammation in rats. HPLC analysis was performed, inflammation and oedema was induced by 1% carrageenan in all the groups. Crude extract of Dunaliella salina and carotenoids enrich fractions; zeaxanthin and β-carotene were administered orally concurrent with carrageenan. Paw thickness was measured at t = 1, 2, 3 and 4 hours. Oxidative stress biomarkers; nitric oxide (NO), malondialdehyde (MDA) and catalase, proinflammatory cytokines; tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2) and neurotransmitters as serotonin were performed on serum samples. The HPLC analysis showed that crude extract contains β-carotene (19.167 mg/g extract) and zeaxanthin (‎16.196 mg/g extract), while beta carotene enrich fraction contains β-carotene (43.157 mg/g fraction) and zeaxanthin enrich fraction contains β-carotene (22.015 mg/g fraction). D. salina and carotenoids enrich fractions showed a statistically significant decrease in paw thickness at P < 0.05. D. salina and carotenoids rich fractions downregulated TNF-α, IL-6, COX-2, PGE2 and serotonin. D. salina and carotenoids enrich fractions ameliorated carrageenan inflammatory reaction by suppressing the oxidative stress and proinflammatory cytokines pathway.

Anti-Inflammatory Activity of Artemisia vulgaris Leaves, Originating from Three Different Altitudes of Nepal.

This study aimed to evaluate and compare the in vivo chronic anti-inflammatory efficacy, from the ethyl acetate and ethanolic extracts of Artemisia vulgaris leaves, grown at three different altitudes in Nepal, by formalin-induced paw edema in Swiss albino mice. Edema was induced on the mice paw by administering 0.2% of formalin injection. Indomethacin was used as a standard drug at the concentration of 5 mg/kg of body weight. Ethyl acetate and ethanolic leaves extract, at the concentration of 200 mg/kg and 400 mg/kg, were used as test drugs. Standard drug and all the extracts were administered 30 min before formalin injection. The paw thickness was measured at 0, 1, 2, 3, 24, 48, and 72 hours after formalin injection, using a Vernier caliper. It was observed that both ethyl acetate and ethanolic extract from all the altitudes exhibited significant inhibition of paw edema (p < 0.05) induced by formalin. Maximum activity was shown by 400 mg/kg of the plant leaf extract taken from the temperate zone, with 54.05% of paw edema inhibition, and it is almost similar to the inhibition of standard drug (56.75%). Moreover, the ethanolic extract was found to be more effective than ethyl acetate extract in all the plant samples. The results suggested that the anti-inflammatory effect of A. vulgaris leaves increases with an increase in altitudes and this plant can be used as a useful source of medicine to treat chronic inflammation.

Effect of Glabridin on Microvascular Permeability of Plasma Proteins Induced by Carrageenan

In the present study, investigate the anti-inflammatory effects of glabridin (GLA) in the carrageenan-induced paw edema test of rats. Inflammation is an answer to the body's immune response to various stimuli such as physical trauma, various antigens, chemicals, microorganisms, radiation-damaged tissues. The cause of this edema is the increase of vascular permeability, an increase in local blood flow, as well as the penetration of neutrophils and macrophages into the inflamed tissue. The current study aimed to determine the mechanism of microvascular leakage on carrageenan (CAR)-induced paw edema of GLA. Therefore, 10, 20 and 40 mg / kg doses of GLA were given intraperitoneal 3 days before intraplantar administration of CAR by using Evans blue (EB) method and by measuring paw thickness with electronic digital calipers. As a result, GLA inhibited both edema and microvascular leak. The results of our study suggest that pretreat-GLA to CAR-induced paw edema of rats via anti-inflammatory potential through inhibition of parameters such as microvascular escape and anti-edematous effect. These findings may be a new treatment of inflammation by anti-protein leakage of GLA.

Antioxidant, anti-inflammatory and anti-arthritic activities of methanol extract of Tamus communis L. roots

Purpose: To evaluate the antioxidant, anti-inflammatory and anti‐arthritic effects of the methanol extract of Tamus communis roots.&#x0D; Methods: The total phenolic and flavonoid contents were determined using Folin–Ciocalteu’s reagent and aluminium chloride assays, respectively while the antioxidant capacity was determined using DPPH and β-carotene/linoleate tests. For anti-inflammatory activity, carrageenan-induced paw edema in rat was used. Formaldehyde-induced paw edema and adjuvant-induced arthritis in rats were used to evaluate the anti-arthritic effect of the extract.&#x0D; Results: The total phenolic and flavonoid contents of T. communis showed 55.2 ± 0.036 mg GAE/g dry weight and 1.191 ± 0.002 mg QEq/g dry weight, respectively while the antioxidant activity (DPPH) showed a half-maximal inhibitory concentration (IC50 of 0.128 ± 0.011 mg/mL. Using βcarotene/linoleate assay, the extract showed 88.13 ± 4.03 % inhibition. In carrageenan-induced paw edema in rat, all doses of T. communis did not show inhibition of edema. In contrast, formaldehyde induced paw edema decreased at the dose of 150 mg/kg days 2 and 4. However, doses of 300 and 600 mg/kg did not show any activity. In adjuvant-induced arthritis, all used doses caused no reduction in arthritic scores and in paw thickness except a significant decrease with the dose 150 mg/kg at the last day.&#x0D; Conclusion: T. communis extract exhibits high antioxidant activity related to the phenolic compound contents. However, the results of the anti-inflammatory and anti‐arthritic studies did not support its use in folk medicine in the treatment of rheumatic ailment except on low doses

Porphyromonas gingivalis induces periodontitis, causes immune imbalance, and promotes rheumatoid arthritis.

Periodontitis induced by bacteria especially Porphyromonas gingivalis (P. gingivalis) is the most prevalent microbial disease worldwide and is a significant risk factor for systemic diseases such as rheumatoid arthritis (RA). RA and periodontitis share similar clinical and pathologic features. Moreover, the prevalence of RA is much higher in patients with periodontitis than in those without periodontitis. To explore the immunologic mechanism of periodontitis involved in RA, we established a mouse model of periodontitis and then induced RA. According to the results of paw thickness, arthritis clinical score, arthritis incidence, microscopic lesion using H&E staining, and micro-CT analysis, periodontitis induced by P. gingivalis promoted the occurrence and development of collagen-induced arthritis (CIA) in mice. Furthermore, periodontitis enhanced the frequency of CD19+ B cells, Th17, Treg, gMDSCs, and mMDSCs, whereas down-regulated IL-10 producing regulatory B cells (B10) in CIA mice preinduced for periodontitis with P. gingivalis. In vitro stimulation with splenic cells revealed that P. gingivalis directly enhanced differentiation of Th17, Treg, and mMDSCs but inhibited the process of B cell differentiation into B10 cells. Considering that adoptive transfer of B10 cells prevent RA development, our study, although preliminary, suggests that down-regulation of B10 cells may be the key mechanism that periodontitis promotes RA as the other main immune suppressive cells such as Treg and MDSCs are up-regulated other than down-regulated in group of P. gingivalis plus CIA.

Melatonin Alleviates Acute Gouty Inflammation In Vivo and In Vitro.

The aim of this study was to identify the effects of melatonin on acute gouty inflammation and to investigate the underlying mechanisms. We found significantly lower serum melatonin levels in gout patients in the acute phase than in those in the remission phase or in normal individuals. The mRNA expression of melatonin receptor 2 (MT2) was also lower in gout patients than in normal individuals. To verify the in-vivo role of melatonin, a gouty arthritis model was established by intraarticular injection of monosodium urate (MSU, 1 mg) crystals into the paws of C57BL/6 mice. Joint inflammation in the mouse model was evaluated by measuring the thickness of the right paw/left paw, and the inflammation index was determined by examining infiltrating neutrophils with haematoxylin and eosin (H&E) staining. Melatonin was found to reduce both paw thickness and the inflammation index in the mouse model, and melatonin also reduced the mRNA levels of interleukin-1 beta (IL-1β), IL-6 and NLR family pyrin domain containing 3 (NLRP3) inflammasome. To mimic gouty inflammation in vitro, mouse peritoneal macrophages were stimulated with lipopolysaccharides (LPS) plus MSU. Melatonin was revealed to reduce IL-1β secretion by stimulated macrophages. The mRNA expression levels of IL-1β and IL-6 were also inhibited by melatonin. Western blot analysis showed that the expression of NLRP3, caspase-1 and pro-IL-1β was also inhibited by melatonin. In conclusion, our study demonstrated that melatonin alleviated gouty inflammation in vivo and in vitro, and the underlying mechanism may involve inhibiting the assembly of the NLRP3 inflammasome.

Monoacylglycerol Lipase Inhibition Using JZL184 Attenuates Paw Inflammation and Functional Deficits in a Mouse Model of Inflammatory Arthritis.

Background: Patients with rheumatoid arthritis (RA) experience joint swelling and cartilage destruction resulting in chronic pain, functional disability, and compromised joint function. Current RA treatments, including glucocorticoid receptor agonists, produce adverse side effects and lack prolonged treatment efficacy. Cannabinoids (i.e., cannabis-like signaling molecules) exert anti-inflammatory and analgesic effects with limited side effects compared to traditional immunosuppressants, making them excellent targets for the development of new arthritic therapeutics. Monoacylglycerol lipase (MAGL) inhibition reduces inflammation in mouse models of acute inflammation, through cannabinoid receptor dependent and independent pathways. The current study investigated the efficacy of inhibiting synthetic and catabolic enzymes that regulate the endocannabinoid 2-arachidonoylglycerol (2-AG) in blocking paw inflammation, pain-related behaviors, and functional loss caused by collagen-induced arthritis (CIA). Methods: Male DB1A mice subjected to CIA were administered the glucocorticoid agonist dexamethasone (DEX), MAGL inhibitor JZL184 (8 or 40 mg/kg, s.c.), alone or in combination, or diacylglycerol lipase β (DAGLβ) inhibitor KT109 (40 mg/kg, s.c.). CIA-induced deficits were assayed by arthritic clinical scoring, paw thickness measurements, and behavioral tests of pain and paw function. Results: DEX or dual administration with JZL184 reduced paw thickness and clinical scores, and JZL184 dose-dependently attenuated grip strength and balance beam deficits caused by CIA. Traditional measures of pain-induced behaviors (hyperalgesia and allodynia) were inconsistent. The antiarthritic effects of JZL184 (40 mg/kg) were largely blocked by coadministration of the CB2 antagonist SR144528, and the DAGLβ inhibitor KT109 had no effect on CIA, indicating that these effects likely occurred through CB2 activation. Conclusions: MAGL inhibition reduced paw inflammation and pain-depressed behavioral signs of arthritis, likely through an endocannabinoid mechanism requiring CB2. These data support the development of MAGL as a target for therapeutic treatment of inflammatory arthritis.

Linalyl acetate as a potential preventive agent against muscle wasting in rheumatoid arthritis rats chronically exposed to nicotine

Cigarette smoking has detrimental effects on rheumatoid arthritis (RA), characterized by muscle wasting. Linalyl acetate (LA), the main component of Lavandula angustifolia Mill (lavender) oil, has anti-inflammatory properties. We investigated the detrimental effects of chronic nicotine exposure in rats with RA, as well as the abilities of lavender oil and LA to prevent muscle wasting. Rats with RA induced by type II collagen were exposed to nicotine for 22 days from day 1. Lavender oil or LA was administered twice a week during the experiment. Compared with control, collagen-induced arthritis (CIA) and chronic nicotine exposure plus CIA (NicoCIA) showed increases in hind paw thickness and serum interleukin (IL)-6 and decreases in body weight and serum insulin-like growth factor (IGF)-1 levels. Moreover, weight and fiber cross-sectional area of the gastrocnemius muscle were much lower, and mitochondrial membrane potential of the gastrocnemius muscle was higher, in the NicoCIA than in the CIA. These alterations in the NicoCIA were prevented by lavender oil and LA. Importantly, LA showed greater activity than lavender oil in preventing IGF-1 reduction in the NicoCIA. These findings suggest that lavender oil and LA may have preventive benefit in RA by counteracting muscle wasting associated with chronic nicotine exposure.

Effect of Epstein-Barr Virus DNA on the Incidence and Severity of Arthritis in a Rheumatoid Arthritis Mouse Model.

ObjectiveWe recently demonstrated that EBV DNA is correlated with proinflammatory responses in mice and in rheumatoid arthritis (RA) patients; hence, we utilized an RA mouse model to examine whether EBV DNA enhances the risk and severity of arthritis and to assess its immunomodulatory effects.MethodsC57BL/6J mice were treated with collagen (arthritis-inducing agent), EBV DNA 6 days before collagen, EBV DNA 15 days after collagen, Staphylococcus epidermidis DNA 6 days before collagen, EBV DNA alone, or water. Mice were then monitored for clinical signs and affected joints/footpads were histologically analysed. The relative concentration of IgG anti- chicken collagen antibodies and serum cytokine levels of IL-17A and IFNϒ were determined by ELISA. The number of cells co-expressing IL-17A and IFNϒ in joint histological sections was determined by immunofluorescence.ResultsThe incidence of arthritis was significantly higher in mice that received EBV DNA prior to collagen compared to mice that only received collagen. Similarly, increased clinical scores, histological scores and paw thicknesses with a decreased gripping strength were observed in groups treated with EBV DNA and collagen. The relative concentration of IgG anti-chicken collagen antibodies was significantly increased in the group that received EBV DNA 6 days prior to collagen in comparison to the collagen receiving group. On the other hand, the highest number of cells co-expressing IFNϒ and IL-17A was observed in joints from mice that received both collagen and EBV DNA.ConclusionEBV DNA increases the incidence and severity of arthritis in a RA mouse model. Targeting mediators triggered by viral DNA may hence be a potential therapeutic avenue.