Mechanical Hypernociception Research Articles

Meloxicam subaracnoide não inibe a hipernocicepção mecânica no teste da carragenina em ratos

Background and objectiveEvaluate the antinociceptive effects of subarachnoid meloxicam on the mechanical hypernociception induced by carrageenan in rats. MethodsRandomized controlled trial. Eighteen adult male Wistar rats underwent a cannula implantation into the subarachnoid space and were randomly divided into two groups: Group I (GI) received saline solution 5μL, while Group II (GII) received meloxicam 30mg. The mechanical hypernociception was induced by intraplantar injection of carrageenan and evaluated using a digital analgesymeter every 30minutes during a 4 hour period. The results were recorded as the Δ withdrawal threshold (in g), calculated by subtracting the measurement value after ResultsThe Δ withdrawal threshold mean values were lower in the group of patients treated with meloxicam over all time points between 45 and 165minutes, however, there was no statistical significance, (p=0.835) for this difference. ConclusionSubarachnoid meloxicam at a dose of 30μg.animal–1 did not suppress the mechanical hypernociception in a model of inflammatory pain induced by intraplantar administration of carrageenan in rats. The data suggest that other dosages should be investigated the drug effect is discarded.

Involvement of cerebral nervous system areas and cytokines on antihyperalgesic and anti-inflammatory activities of Kielmeyera rugosa Choisy (Calophyllaceae) in rodents.

Kielmeyera rugosa is a medicinal plant known in Northeastern Brazil as 'pau-santo', and it is used in the treatment of several tropical diseases such as malaria, schistosomiasis, and leishmaniasis. We evaluated antihyperalgesic and anti-inflammatory activities of methanol stem extract of K. rugosa (MEKR) in mice. The mechanical hyperalgesia induced by carrageenan and tumor necrosis factor-alpha (TNF-α), prostaglandin E2 , and dopamine were assessed. We also investigated the anti-inflammatory effect of MEKR on carrageenan-induced pleurisy and paw edema. Ninety minutes after the treatment, the animals were submitted to an imunofluorescence for Fos protein. MEKR (100, 200, and 400 mg/kg; p.o.) inhibited the development of mechanical hypernociception and edema. MEKR significantly decreased TNF-α and interleukin 1β levels in pleural lavage and suppressed the recruitment of leukocytes. MEKR (1, 10, and 100 mg/mL) did not produce cytotoxicity, determined using the methyl-thiazolyl-tetrazolium assay in vitro. The locomotor activity was not affected. MEKR activated significantly the bulb olfactory, piriform cortex, and periaqueductal gray of the central nervous system. Our results provide first time evidence to propose that MEKR attenuates mechanical hyperalgesia and inflammation, in part, through an activation of central nervous system areas, mainly the periaqueductal gray and piriform cortex areas.

Anti-hypernociceptive effect of mangiferin in persistent and neuropathic pain models in rats

The present study examines the possible effect of the glucosylxanthone mangiferin (MG) on pain-related behaviors in a tonic acute pain model (formalin test at 5%) and in a chronic constriction injury (CCI) model to clarify the underlying transient and long-term mechanisms. Acute administration of MG (10–100mg/kg, i.p.) reduced licking/biting exclusivity in the tonic phase of formalin test in a naloxone and yohimbine-sensitive manner. This effect was enhanced by a nonselective nitric oxide synthase (NOS) inhibitor (NG-monomethyl-l-arginine) and by a non-competitive N-methyl-d-aspartate (NMDA) antagonist (ketamine), but it was reversed by the NOS substrate (l-arginine). Pre-treatment with intrathecal yohimbine prevented the anti-hypernociceptive effect of systemic MG. Pre-treatment during 4days before surgical and 3days after CCI with MG (50mg/kg, i.p.) reduced mechanical hypernociception and decreased the signs of Wallerian degeneration (WD) of the sciatic nerve. MG improved the PC-12 cellular viability exposure to glutamate-mediated neuronal death, also involved in neuropathic pain. The findings of this study suggest that MG shows ability to decrease tonic pain in the formalin test. A transient activity of this xanthone on nociceptive pathways mediated by α2 adrenergic receptors in cooperation with the opioid system could be involved, at least in part, in this effect. Its neuroprotective effect by preventing WD in mononeuropathic rats could be implicated in the mechano-antihypernociceptive long term mechanisms.

<b>Structural features and assessment of zymosan-induced arthritis in rat temporomandibular joint model using sulfated polysaccharide

The green seaweed Caulerpa cupressoides var. lycopodium contains three SPs fractions (Cc-SP1, Cc-SP2 and Cc-SP3). Cc-SP1 and Cc-SP2 had anticoagulant (in vitro), pro- and antithrombotic, antinociceptive and/or anti-inflammatory (in vivo) effects. This study analyzed structural features and the antinociceptive and anti-inflammatory effects of Cc-SP1 on zymosan-induced acute arthritis of the rat temporomandibular joint (TMJ). Cc-SP1 was investigated by infrared technique. Male Wistar rats (200- 240 g) received subcutaneously (s.c.) Cc-SP1 1h prior to intra-articular (i.art.) injection of zymosan (2 mg joint -1 ) or saline (0.9%) into the left TMJ. Mechanical hypernociception was measured by the electronic Von Frey method in the basal and 4h after zymosan injection. Animals were euthanized 6h after zymosan injection and the TMJ cavity was removed for total leukocyte counts from the synovial fluid and myeloperoxidase (MPO) activity assessment. Cc-SP1 (1, 3 or 9 mg kg -1 ) containing sulfate ester, galactose- 6-sulfate, uronic acid and glycosidic linkages reduced zymosan-induced hypernociception (78.12, 81.13 and 87.43%, respectively, p < 0.01), and inhibited the total leukocyte influx (85, 88.14 and 89.95%, respectively, p < 0.01), being confirmed by MPO activity (p < 0.05). Therefore, Cc-SP1 reveals a pharmacological tool for treating inflammatory arthropathies.

A lectin from the green seaweed Caulerpa cupressoides reduces mechanical hyper-nociception and inflammation in the rat temporomandibular joint during zymosan-induced arthritis.

Seaweed lectins have been widely investigated as anti-nociceptive and anti-inflammatory agents. This study analyzed the anti-nociceptive and anti-inflammatory responses of a lectin from the green seaweed Caulerpa cupressoides (CcL) on zymosan-induced arthritis of the rat temporomandibular joint (TMJ). Rats received i.v. CcL 30 min prior to injection of zymosan (2mg/art.) or 0.9% saline into the left TMJ. Mechanical hyper-nociception was measured by the electronic von Frey method at baseline and 4h after zymosan injection. Animals were euthanized 6h after zymosan injection and the synovial fluid was collected for leukocyte counting and myeloperoxidase activity assessment. Other animals were treated with ZnPP-IX (3mg/kg; s.c.), a specific heme oxygenase-1 pathway inhibitor, and naloxone (10 μg/art.), a nonselective opioid receptor antagonist. TMJ tissues were excised to perform histopathological and immunohistochemistry analyses. CcL (0.1, 1 or 10mg/kg) significantly reduced zymosan-induced hyper-nociception (81, 83 and 89.5%, respectively) and inhibited the leukocyte influx (77.3, 80.7 and 98.5%, respectively) compared with the zymosan-only group, as confirmed by myeloperoxidase activity; however, treatment with naloxone or ZnPP-IX did not revert the effects of CcL (10mg/kg), suggesting that the naloxone-sensitive opioid and heme oxygenase-1 pathways are not involved. CcL also reduced the leukocyte influx and the expression of IL-1β and TNF-α in the TMJ, based on histopathological and immunohistochemistry analyses, respectively. Therefore, CcL reduces TMJ hyper-nociception and inflammation with a mechanism that is partially dependent on TNF-α and IL-1β inhibition. CcL reveals a potentially valuable alternative tool for future studies of TMJ disorders.

Phyllanthus amarus Does Not Affect Hypernociception in Experimental Autoimmune Encephalomyelitis

Multiple sclerosis is an inflammatory disease of the central nervous system. Chronic pain is one of the main symptoms, affecting many patients. Studies show that the lignans or the apolar extracts of Phyllanthus amarus have antinociceptive effects in different animal models. To evaluate the antihypernociceptive effect of a hexanic extract of P. amarus in experimental autoimmune encephalomyelitis in mice, the chemical composition of the hexanic extract was analyzed by gas chromatography mass spectrometry. After EAE induction, animals were treated with the hexanic extract of P. amarus for 26 consecutive days. Motor coordination and mechanical hypernociception were evaluated on alternate days. The principal lignans found were phyllanthin, niranthin, and 5-demethoxyniranthin. The hexanic extract of P. amarus at a dose of 100, 200, or 400 mg/kg did not affect the development of the disease. The motor coordination and pain threshold of the treated animals were not altered in this experiment. In conclusion, in this test, the hexanic extract of P. amarus did not show evidence of antihypernociceptive activity in experimental autoimmune encephalomyelitis.

Role ofNMDAreceptors in the trigeminal pathway, and the modulatory effect of magnesium in a model of rat temporomandibular joint arthritis

Temporomandibular joint (TMJ) arthritis is a common cause of orofacial pain. In the present study, the modulatory effects of N-methyl-d-aspartate receptors (NMDA-Rs) and magnesium were investigated in TMJ arthritis hypernociception. Male Wistar rats received an intra-articular injection of carrageenan (Cg) in the TMJ, and mechanical hypernociception was measured. The NMDA-R antagonist, MK-801, and magnesium chloride (MgCl₂ ) were administered before arthritis induction. Magnesium deficiency was promoted by feeding rats a synthetic magnesium-free diet for 9 d before injection of Cg. The Cg induced mechanical hypernociception that lasted for 120 h. MK-801 inhibited this hypernociceptive state. MgCl₂ pretreatment prevented Cg-induced hypernociception and altered the nociceptive threshold in the absence of Cg. Magnesium deficiency increased hypernociception and induced spontaneous hypernociceptive behavior. TMJ arthritis increased the expression of mRNA for all NMDA-R subunits and immunostaining of phosphorylated NR1 (phospho-NR1). MgCl₂ inhibited expression of NR2B mRNA and phospho-NR1 immunostaining and increased expression of NR3 mRNA. Magnesium deficiency increased expression of both NR1 and NR3 mRNAs and phospho-NR1 immunostaining in the trigeminal subnucleus caudalis. We found that magnesium modulates nociceptive behavior and induces NMDA-R subunit rearrangement in the subnucleus caudalis. The present results may lead to a better understanding of central processing in the nociceptive trigeminal pathway and the development of new approaches to treat orofacial pain with a TMJ origin.

Fractalkine mediates inflammatory pain through activation of satellite glial cells

The activation of the satellite glial cells (SGCs) surrounding the dorsal root ganglion (DRG) neurons appears to play a role in pathological pain. We tested the hypothesis that fractalkine, which is constitutively expressed by primary nociceptive neurons, is the link between peripheral inflammation and the activation of SGCs and is thus responsible for the genesis of the inflammatory pain. The injection of carrageenin into the rat hind paw induced a decrease in the mechanical nociceptive threshold (hypernociception), which was associated with an increase in mRNA and GFAP protein expression in the DRG. Both events were inhibited by anti-fractalkine antibody administered directly into the DRG (L5) [intraganglionar (i.gl.)]. The administration of fractalkine into the DRG (L5) produced mechanical hypernociception in a dose-, time-, and CX3C receptor-1 (CX3CR1)-dependent manner. Fractalkine's hypernociceptive effect appears to be indirect, as it was reduced by local treatment with anti-TNF-α antibody, IL-1-receptor antagonist, or indomethacin. Accordingly, the in vitro incubation of isolated and cultured SGC with fractalkine induced the production/release of TNF-α, IL-1β, and prostaglandin E2. Finally, treatment with i.gl. fluorocitrate blocked fractalkine (i.gl.)- and carrageenin (paw)-induced hypernociception. Overall, these results suggest that, during peripheral inflammation, fractalkine is released in the DRG and contributes to the genesis of inflammatory hypernociception. Fractalkine's effect appears to be dependent on the activation of the SGCs, leading to the production of TNFα, IL-1β, and prostanoids, which are likely responsible for the maintenance of inflammatory pain. Thus, these results indicate that the inhibition of fractalkine/CX3CR1 signaling in SGCs may serve as a target to control inflammatory pain.

ANTIHYPERALGESIC EFFECT OF LATEX PROTEINS FROM CALOTROPIS PROCERA: INVOLVEMENT OF INFLAMMATORY MEDIATORS

Background and aimsCalotropis procera is a tropical plant found worldwide and has been used in the traditional medicinal for the treatment of various diseases. This study aimed to evaluate the effects of protein fraction from Calotropis procera latex (LP) in the mechanical hypernociception (increase in the sensitivity of nociception).MethodsSwiss male mice were used. b) Mechanical hypernociception (MH) was evaluated using the electronic version of the Von Frey before and after the injection of carrageenan (300 μg/paw‐Cg) or LP (0.5, 5 and 50 mg/kg, iv, 30 min before Cg application) into the mice paw (1, 3 and 5 hours after Cg). c) After 3 h of Cg injection, subplantar tissue was collected for measurement of: myeloperoxidase activity (MPO); cytokines (TNF‐α and IL‐1β) and chemokine (KC) production; prostaglandin E2 (PGE2) production. d) ANOVA/Bonferroni was used as statistical tests. P&lt;0.05 was accepted. e) Ethics Committee 61/11.ResultsLP 5 mg/kg reduced MH in 25%, 55% and 46% and LP 50 mg/kg in 39%, 64% and 60% in the 1st, 3rd and 5th hours. LP at 5 and 50 mg/kg decreased MPO concentration in 80% and 94% respectively. LP at 5mg/kg reduced the concentration of TNF‐ α, IL‐1β, KC and PGE2 at 71%, 81%, 72% and 72% respectively.ConclusionLP has antinociceptive properties in animal model of acute pain and this may be associated with the inhibition of neutrophil migration, cytokine and chemokine production. CAPES and CNPq.

CB1 and CB2 contribute to antinociceptive and anti-inflammatory effects of electroacupuncture on experimental arthritis of the rat temporomandibular joint

Electroacupuncture (EA) and cannabinoids have been reported to have anti-inflammatory and antinociceptive effects in animal models of arthritis. Male Wistar rats were injected with saline or zymosan (2 mg) into the temporomandibular joint (TMJ). EA (10 Hz, 30 min) was performed 2 h after or 1 h before zymosan administration. AM251 or AM630 (3 mg/kg, i.p.)were administered before EA treatment. Mechanical hypernociception was accessed after zymosan administration. Rats were sacrificed 6 h after zymosan administration and the joint was removed for histopathological analysis. The gene expression of CB₁ and CB₂ receptors was assessed after sacrifice of the TMJ arthritic animals. EA inhibited zymosan-induced hypernociception (p < 0.05). AM251 reversed significantly the antinociceptive effect of EA, suggesting that the CB₁ receptor is involved in this effect. AM630 reversed the anti-inflammatory effect of EA. CB₁ and CB₂ receptor gene expression was upregulated 6 h after zymosan-induced arthritis in the EA-treated group. We observed downregulation of CB₂ receptor gene expression in the EA group at the 24th hour compared with the 6th hour. Higher CB₁ receptor gene expression was also found compared with the 6th hour. EA produced antinociceptive and anti-inflammatory effects, and these effects appeared to be mediated through CB₁ and CB₂ receptor activation.

Antihypernociceptive activity of anethole in experimental inflammatory pain

Anethole has been reported to have antioxidant, antibacterial, antifungal, antiinflammatory, and anesthetic properties. In the present study, we evaluated the effects of anethole in two pain models of inflammatory origin: acute inflammation induced by carrageenan and persistent inflammation induced by Complete Freund's adjuvant. We evaluated the effects of anethole (125, 250, and 500 mg/kg) on the development of paw oedema and mechanical hypernociception. The liver was collected for histological analysis. Paw skin was collected to determine the levels of the cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-17 (IL-17), and myeloperoxidase activity. Blood was collected to assess alanine transaminase (ALT) and aspartate transaminase (AST). The chemical composition of star anise oil was determined by gas chromatography/mass spectrometry (GC/MS), showing a presence of anethole of 98.1%. Oral pretreatment with anethole in mice inhibited paw oedema, mechanical pernociception, myelopewroxidase activity, TNF-α, IL-1β and IL-17 levels in acute and persistent inflammation models. Additionally, anethole treatment did not alter prostaglandin E2-induced mechanical hypernociception. Possible side effects were also examined. Seven-day anethole treatment did not alter plasma AST and ALT levels, and the histological profile of liver tissue was normal. The present study provides evidence of the antiinflammatory and analgesic activities of anethole in acute and persistent inflammation models.

Involvement of the NO/cGMP/PKG/KATP pathway and endogenous opioids in the antinociceptive effect of a sulphated-polysaccharide fraction extracted from the red algae, Gracilaria caudata

We investigated the antinociceptive activity of a sulphated-polysaccharide (PLS) fraction extracted from the sea algae Gracilaria caudata against carrageenan-induced hypernociception in mice and the mechanism underlying the antinociceptive activity. Mechanical inflammatory hypernociception was measured with an electronic version of the Von Frey® test. Mice were treated with PLS (2.5, 5.0, and 10 mg/kg, 0.5mL, p.o.) 1h before carrageenan treatment. l-Noarg (100ng/paw; 50μL) was administered 1h before carrageenan administration. l-Arg (l-Arginine; 200 mg/kg; 0.5mL, p.o.) was administered 10min before l-Noarg injection. ODQ (8μg/paw), KT 5823 (1.5μg/paw), glibenclamide (160μg/paw), and naloxone (1.0μg/paw) were administered 30min before carrageenan administration. PLS reduced carrageenan-induced hypernociception (300μg/paw, 50μL, intraplantar injection). PLS-induced analgesia was reversed by l-Noarg, and the effect of l-Noarg was prevented by l-Arg. The soluble guanylyl cyclase inhibitor ODQ, the protein kinase G inhibitor KT 5823, the KATP blocker glibenclamide, and the opioid receptor antagonist naloxone, significantly reversed (P<0.05) the antinociceptive effect of PLS. The present study showed an intrinsic peripheral antinociceptive action of PLS administration in mice. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP/PKG pathway followed by the opening of KATP channels, and depended on endogenous opioids.

Geopropolis from Melipona scutellaris decreases the mechanical inflammatory hypernociception by inhibiting the production of IL-1β and TNF-α

Ethnopharmacological relevanceThe pharmacological activity of geopropolis collected by stingless bees (important and threatened pollinators), a product widely used in folk medicine by several communities in Brazil, especially in the Northeast Region, needs to be studied. ObjectiveThe aim of this study was to evaluate the antinociceptive activity of Melipona scutellaris geopropolis (stingless bee) using different models of nociception. Material and methodsThe antinociceptive activity of the ethanolic extract of geopropolis (EEGP) and fractions was evaluated using writhing induced by acetic acid, formalin test, carrageenan-induced hypernociception, and quantification of IL-1β and TNF-α. The chemical composition was assessed by quantification of total flavonoids and phenolic compounds. ResultsEEGP and its hexane and aqueous fractions showed antinociceptive activity. Both EEGP and its aqueous fraction presented activity in the mechanical inflammatory hypernociception induced by the carrageenan model, an effect mediated by the inhibition of IL-1β and TNF-α. The chemical composition of EEGP and its hexane and aqueous fractions showed a significant presence of phenolic compounds and absence of flavonoids. ConclusionOur data indicate that geopropolis is a natural source of bioactive substances with promising antinociceptive activity.

Antiinflammatory and antinociceptive effects in mice of a sulfated polysaccharide fraction extracted from the marine red algae Gracilaria caudata

Many algal species contain relatively high concentrations of polysaccharide substances, a number of which have been shown to have anti-inflammatory and/or immunomodulatory activity. In this study, we evaluated the anti-inflammatory and antinociceptive effects in mice of a sulfated polysaccharide fraction (PLS) extracted from the algae Gracilaria caudata. The antiinflammatory activity of PLS was evaluated using several inflammatory agents (carrageenan, dextran, bradykinin, and histamine) to induce paw edema and peritonitis in Swiss mice. Samples of the paw tissue and peritoneal fluid were removed to determine myeloperoxidase (MPO) activity or TNF-α and IL-1β levels, respectively. Mechanical hypernociception was induced by subcutaneous injection of carrageenan into the plantar surface of the paw. Pretreatment of mice by intraperitoneal administration of PLS (2.5, 5, and 10 mg/kg) significantly and dose-dependently reduced carrageenan-induced paw edema (p < 0.05) compared to vehicle-treated mice. Similarly, PLS 10 mg/kg effectively inhibited edema induced by dextran and histamine; however, edema induced by bradykinin was unaffected by PLS. PLS 10 mg/kg inhibited total and differential peritoneal leukocyte counts following carrageenan-induced peritonitis. Furthermore, PLS reduced carrageenan-increased MPO activity in paws and reduced cytokine levels in the peritoneal cavity. Finally PLS pretreatment also reduced hypernociception 3–4 h after carrageenan. We conclude that PLS reduces the inflammatory response and hypernociception in mice by reducing neutrophil migration and cytokines concentration.

α‐Terpineol Reduces Mechanical Hypernociception and Inflammatory Response

α-Terpineol (TPN), a volatile monoterpene alcohol, is relatively non-toxic and one of the major components of the essential oils of various plant species. In this study, we tested for the antihypernociceptive activity of TPN (25, 50 or 100 mg/kg, i.p.) in mice using mechanical models of hypernociception induced by carrageenan (CG, 300 μg/paw) and the involvement of important mediators of its cascade signalling, such as tumour necrosis factor-α (TNF-α, 100 pg/paw), prostaglandin E₂ (PGE₂, 100 ng/paw) or dopamine (DA, 30 μg/paw). We also investigated the anti-inflammatory effect of TPN on the model of carrageenan-induced pleurisy and the LPS-induced nitrite production in murine macrophages. Pre-systemic treatment with TPN (25, 50 or 100 mg/kg, i.p.) inhibited the development of mechanical hypernociception induced by CG or TNF-α. A similar effect was also observed upon PGE₂ and DA administration. In addition, TPN significantly inhibited the neutrophil influx in the pleurisy model. TPN (1, 10 and 100 μg/mL) also significantly reduced (p < 0.01) nitrite production in vitro. Our results provide information about the antinociceptive and anti-inflammatory properties of TPN on mechanical hypernociception and suggest that this compound might be potentially interesting in the development of new clinically relevant drugs for the management of painful and/or inflammatory disease.

Participation of the NO/cGMP/K+ATP pathway in the antinociception induced by Walker tumor bearing in rats

Implantation of Walker 256 tumor decreases acute systemic inflammation in rats. Inflammatory hyperalgesia is one of the most important events of acute inflammation. The L-arginine/NO/cGMP/K+ATP pathway has been proposed as the mechanism of peripheral antinociception mediated by several drugs and physical exercise. The objective of this study was to investigate a possible involvement of the NO/cGMP/K+ATP pathway in antinociception induced in Walker 256 tumor-bearing male Wistar rats (180-220 g). The groups consisted of 5-6 animals. Mechanical inflammatory hypernociception was evaluated using an electronic version of the von Frey test. Walker tumor (4th and 7th day post-implantation) reduced prostaglandin E2- (PGE2, 400 ng/paw; 50 µL; intraplantar injection) and carrageenan-induced hypernociception (500 µg/paw; 100 µL; intraplantar injection). Walker tumor-induced analgesia was reversed (99.3% for carrageenan and 77.2% for PGE2) by a selective inhibitor of nitric oxide synthase (L-NAME; 90 mg/kg, ip) and L-arginine (200 mg/kg, ip), which prevented (80% for carrageenan and 65% for PGE2) the effect of L-NAME. Treatment with the soluble guanylyl cyclase inhibitor ODQ (100% for carrageenan and 95% for PGE2; 8 µg/paw) and the ATP-sensitive K+ channel (KATP) blocker glibenclamide (87.5% for carrageenan and 100% for PGE2; 160 µg/paw) reversed the antinociceptive effect of tumor bearing in a statistically significant manner (P < 0.05). The present study confirmed an intrinsic peripheral antinociceptive effect of Walker tumor bearing in rats. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP pathway followed by the opening of KATP channels.

Antinociceptive and anti-inflammatory effects of electroacupuncture on experimental arthritis of the rat temporomandibular joint

This study investigated the antinociceptive and anti-inflammatory effects of electroacupuncture (EA) on zymosan-induced acute arthritis of the rat temporomandibular joint (TMJ). Male Wistar rats were injected with saline or zymosan (control group; 2mg) into the left TMJ. Low frequency EA (10Hz, 30min) was performed at acupoints (LI4, LI11, ST36, ST44) or sham points 2h after or 1h before zymosan administration. Mechanical hypernociception was accessed by the electronic Von Frey method after zymosan administration. Rats were sacrificed 6h after zymosan administration and the joint was removed for histopathological analysis, myeloperoxidase activity assessment, vascular permeability observations, and immunohistochemical verification of inflammatory mediators. The results showed that EA inhibited zymosan-induced hypernociception, compared with the control group and with the sham group (p< 0.05). The results showed that EA inhibited inflammatory parameters such as neutrophil migration, vascular permeability, and tumour necrosis factor α (TNF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expression in the TMJ compared with the sham group (p < 0.05). Histopathological analysis showed that EA significantly inhibited edema and periarticular infiltration (p< 0.05) compared with the control and sham groups. EA at acupoints produced antinociceptive and anti-inflammatory effects on zymosan-induced arthritis in the rat TMJ.

The protein LJM 111 from Lutzomyia longipalpis Salivary Gland Extract (SGE) accounts for the SGE-inhibitory effects upon inflammatory parameters in experimental arthritis model

Several studies have pointed out the immunomodulatory properties of the Salivary Gland Extract (SGE) from Lutzomyia longipalpis. We aimed to identify the SGE component (s) responsible for its effect on ovalbumin (OVA)-induced neutrophil migration (NM) and to evaluate the effect of SGE and components in the antigen-induced arthritis (AIA) model. We tested the anti-arthritic activities of SGE and the recombinant LJM111 salivary protein (rLJM111) by measuring the mechanical hypernociception and the NM into synovial cavity. Furthermore, we measured IL-17, TNF-α and IFN-γ released by lymph nodes cells stimulated with mBSA or anti-CD3 using enzyme-linked immunosorbent assay (ELISA). Additionally, we tested the effect of SGE and rLJM111 on co-stimulatory molecules expression (MHC-II and CD-86) by flow cytometry, TNF-α and IL-10 production (ELISA) of bone marrow-derived dendritic cells (BMDCs) stimulated with LPS, chemotaxis and actin polymerization from neutrophils. Besides, the effect of SGE on CXCR2 and GRK-2 expression on neutrophils was investigated. We identified one plasmid expressing the protein LJM111 that prevented NM in OVA-challenged immunized mice. Furthermore, both SGE and rLJM111 inhibited NM and pain sensitivity in AIA and reduced IL-17, TNF-α and IFN-γ. SGE and rLJM111 also reduced MHC-II and CD-86 expression and TNF-α whereas increased IL-10 release by LPS-stimulated BMDCs. SGE, but not LJM 111, inhibited neutrophils chemotaxis and actin polymerization. Additionally, SGE reduced neutrophil CXCR2 expression and increased GRK-2. Thus, rLJM111 is partially responsible for SGE mechanisms by diminishing DC function and maturation but not chemoattraction of neutrophils.

Carvacrol attenuates mechanical hypernociception and inflammatory response

Carvacrol is a phenolic monoterpene present in the essential oil of the family Lamiaceae, as in the genera Origanum and Thymus. We previously reported that carvacrol is effective as an analgesic compound in various nociceptive models, probably by inhibition of peripheral mediators that could be related with its strong antioxidant effect observed in vitro. In this study, the anti-hypernociceptive activity of carvacrol was tested in mice through models of mechanical hypernociception induced by carrageenan, and the involvement of important mediators of its signaling cascade, as tumor necrosis factor-alpha (TNF-α), prostaglandin E(2) (PGE(2)), and dopamine, were assessed. We also investigated the anti-inflammatory effect of carvacrol on the model of carrageenan-induced pleurisy and mouse paw edema, and the lipopolysaccharide (LPS)-induced nitrite production in murine macrophages was observed. Systemic pretreatment with carvacrol (50 or 100mg/kg; i.p.) inhibited the development of mechanical hypernociception and edema induced by carrageenan and TNF-α; however, no effect was observed on hypernociception induced by PGE(2) and dopamine. Besides this, carvacrol significantly decreased TNF-α levels in pleural lavage and suppressed the recruitment of leukocytes without altering the morphological profile of these cells. Carvacrol (1, 10, and 100μg/mL) also significantly reduced (p < 0.001) the LPS-induced nitrite production in vitro and did not produce citotoxicity in the murine peritoneal macrophages in vitro. The spontaneous locomotor activity of mice was not affected by carvacrol. This study adds information about the beneficial effects of carvacrol on mechanical hypernociception and inflammation. It also indicates that this monoterpene might be potentially interesting in the development of novel tools for management and/or treatment of painful conditions, including those related to inflammatory and prooxidant states.

Toll-like receptor 2/MyD88 signaling mediates zymosan-induced joint hypernociception in mice: Participation of TNF-α, IL-1β and CXCL1/KC

Arthritic pain is a serious health problem that affects a large number of patients. Toll-like receptors (TLRs) activation within the joints has been implicated in pathophysiology of arthritis. However, their role in the genesis of arthritic pain needs to be demonstrated. In the present study, it was addressed the participation of TLR2 and TLR4 and their adaptor molecule MyD88 in the genesis of joint hypernociception (a decrease in the nociceptive threshold) during zymosan-induced arthritis. Zymosan injected in the tibio-tarsal joint induced mechanical hypernociception in C57BL/6 wild type mice that was reduced in TLR2 and MyD88 null mice. On the other hand, zymosan-induced hypernociception was similar in C3H/HePas and C3H/HeJ mice (TLR4 mutant mice). Zymosan-induced joint hypernociception was also reduced in TNFR1 null mice and in mice treated with IL-1 receptor antagonist or with an antagonist of CXCR1/2. Moreover, the joint production of TNF-α, IL-1β and CXCL1/KC by zymosan was dependent on TLR2/MyD88 signaling. Investigating the mechanisms by which TNF-α, IL-1β and CXCL1/KC mediate joint hypernociception, joint administration of these cytokines produced mechanical hypernociception, and they act in an interdependent manner. In last instance, their hypernociceptive effects were dependent on the production of hypernociceptive mediators, prostaglandins and sympathetic amines. These results indicate that in zymosan-induced experimental arthritis, TLR2/MyD88 is involved in the cascade of events of joint hypernociception through a mechanism dependent on cytokines and chemokines production. Thus, TLR2/MyD88 signaling might be a target for the development of novel drugs to control pain in arthritis.