Increased levels of advanced oxidation protein products (AOPPs) were associated with nociceptive behavior and clinical scores in an experimental progressive autoimmune encephalomyelitis model (PMS-EAE).

Multiple sclerosis (MS) is a neurodegenerative disease that affects the central nervous system (CNS) generating neuropathic pain and anxiety. Primary progressive MS (PPMS) is the most disabling clinical form, and the patients present an intense neurodegenerative process. In this context, the advanced oxidation protein products (AOPPs) are oxidized compounds and their accumulation in plasma has been related to clinical disability in MS patients. However, the involvement of AOPPs in neuropathic pain- and anxiety-like symptoms was not previously evaluated. To assess this, female mice C57BL/6J were used to induce progressive experimental autoimmune encephalomyelitis (PMS-EAE). Clinical score, weight, strength of plantar pressure, rotarod test, mechanical allodynia, and cold hypersensitivity were evaluated before induction (baseline) and on days 7th, 10th, and 14th post-immunization. We assessed nest building, open field, and elevated plus-maze tests 13 days post-immunization. Animals were killed at 14 days post-immunization; then, AOPPs levels, NADPH oxidase, and myeloperoxidase (MPO) activity were measured in the prefrontal cortex, hippocampus, and spinal cord samples. The clinical score increased 14th post-immunization without changes in weight and mobility. Reduced paw strength, mechanical allodynia, and cold allodynia increased in the PMS-EAE animals. PMS-EAE mice showed spontaneous nociception and anxiety-like behavior. AOPPs concentration, NADPH oxidase, and MPO activity increase in CNS structures. Multivariate analyses indicated that the rise of AOPPs levels, NADPH oxidase, and MPO activity influenced the clinical score and cold allodynia. Thus, we indicated the association between non-stimuli painful perception, anxiety-like, and CNS oxidative damage in the PMS-EAE model.

Nitric oxide involvement in the disability and active disease of multiple sclerosis: Systematic review and meta-analysis.

BACKGROUND: Multiple sclerosis (MS) is a chronic and immune-mediated disease of unknown etiology and leading to a physical and cognitive disability. Different studies suggest that nitrosative stress may play a pivotal role in the pathogenesis and disability in MS. Besides, reports evaluated NO and their metabolites, expressed by nitrite and nitrate (NOx) levels of MS patients compared with other pathologies, but did not evaluate disability and relapse/remission phases. OBJECTIVE: Thus, this study aimed to conduct a systematic review and meta-analysis of NOx levels in MS patients in relapse/remission phases and its involvement in patient disability. METHODS: The protocol was registered in PROSPERO (CRD42022327161). We used GRADE to estimate the articles' quality and evaluated the publication bias using Egger's and Begg's tests. RESULTS: Here, through a search in the Pubmed, Scopus, and EMBASE databases, 5.276 studies were found, and after the selection process, 20 studies were included in this systematic review and meta-analysis. The studies included data from 1.474 MS patients and 1.717 healthy controls, 1.010 RRMS and 221 primary progressive MS (PPMS). CONCLUSION: NOx levels are increased in relapsing-remitting MS (RRMS) patients in the relapse phase. Also, NOx levels were increased in MS patients with higher disability. However, further studies are still needed to control lifestyle habits, pain, and MS treatment effects in biased NOx levels.

Topical application of a TRPA1 antagonist reduced nociception and inflammation in a model of traumatic muscle injury in rats.

Musculoskeletal pain is a widely experienced public healthcare issue, especially after traumatic muscle injury. Besides, it is a common cause of disability, but this pain remains poorly managed. However, the pathophysiology of traumatic muscle injury-associated pain and inflammation has not been fully elucidated. In this regard, the transient receptor potential ankyrin 1 (TRPA1) has been studied in inflammatory and painful conditions. Thus, this study aimed to evaluate the antinociceptive and anti-inflammatory effect of the topical application of a TRPA1 antagonist in a model of traumatic muscle injury in rats. The mechanical trauma model was developed by a single blunt trauma impact on the right gastrocnemius muscle of Wistar male rats (250-350 g). The animals were divided into four groups (Sham/Vehicle; Sham/HC-030031 0.05%; Injury/Vehicle, and Injury/HC-030031 0.05%) and topically treated with a Lanette® N cream base containing a TRPA1 antagonist (HC-030031, 0.05%; 200 mg/muscle) or vehicle (Lanette® N cream base; 200 mg/muscle), which was applied at 2, 6, 12, 24, and 46 h after muscle injury. Furthermore, we evaluated the contribution of the TRPA1 channel on nociceptive, inflammatory, and oxidative parameters. The topical application of TRPA1 antagonist reduced biomarkers of muscle injury (lactate/glucose ratio), spontaneous nociception (rat grimace scale), inflammatory (inflammatory cell infiltration, cytokine levels, myeloperoxidase, and N-acetyl-ß-D-glucosaminidase activities) and oxidative (nitrite levels and dichlorofluorescein fluorescence) parameters, and mRNA Trpa1 levels in the muscle tissue. Thus, these results demonstrate that TRPA1 may be a promising anti-inflammatory and antinociceptive target in treating muscle pain after traumatic muscle injury.

Evaluation of the analgesic effect of ɑ-lipoic acid in treating pain disorders: A systematic review and meta-analysis of randomized controlled trials.

Neuropathic pain is the most prevalent form of chronic pain caused by a disease of the nervous system, such as diabetic polyneuropathy. ɑ-Lipoic acid (ALA) is an antioxidant that has been widely studied for the treatment of pain symptoms in diverse conditions. Therefore, this study aimed to investigate the efficacy of ALA in the treatment of different types of pain through a systematic review and meta-analysis of randomized clinical trials. The study protocol was registered in the International Prospective Registry of Systematic Reviews (CRD42021261971). A search of the databases resulted in 1154 articles, 16 of which were included in the review (9 studies with diabetic polyneuropathy and 7 studies with other painful conditions). Most of the included studies had a low risk of bias. ALA showed efficacy for the treatment of headache, carpal tunnel syndrome and burning mouth syndrome. Meta-analysis was conducted only with the studies using diabetic polyneuropathy. Compared to placebo, ALA treatment decreased the total symptom score (TSS). The subgroup meta-analysis indicated a decrease of stabbing pain, burning, paraesthesia, and numbness in ALA-treated patients compared to placebo. In addition, both routes of administration, intravenous and oral, demonstrated the efficacy to reduce TSS. Therefore, ALA should be used to treat diabetic polyneuropathy pain symptoms. However, the standardization of treatment time and the dose may advance for the approval of ALA for clinical use in diabetic polyneuroneuropathy.

Anti-genotoxic and anti-mutagenic effects of melatonin supplementation in a mouse model of melanoma.

Melanoma, an aggressive skin cancer originating from melanocytes, can metastasize to the lungs, liver, cortex, femur, and spinal cord, ultimately resulting in DNA mutagenic effects. Melatonin is an endogenous hormone and free radical scavenger that possesses the ability to protect the DNA and to exert anti-proliferative effects in melanoma cells. The aim of this study was to evaluate the effects of B16F10 melanoma cells and the effects of melatonin supplementation on genotoxic parameters in murine melanoma models. Thirty-two male C57Bl/6 mice were divided in the following four groups: PBS + vehicle (n = 6), melanoma + vehicle (n = 10), PBS + melatonin (n = 6), and melanoma + melatonin (n = 10). The melanoma groups received a B16F10 cell injection, and melatonin was administered during 60 days. After treatment, tumor sizes were evaluated. DNA damage within the peripheral blood, lungs, liver, cortex, and spinal cord was determined using comet assay, and the mutagenicity within the bone marrow was determined using the micronucleus test. B16F10 cells effectively induced DNA damage in all tissues, and melatonin supplementation decreased DNA damage in the blood, liver, cortex, and spinal cord. This hormone exerts anti-tumor activity via its anti-proliferative, antioxidative, and pro-apoptotic effects. As this result was not observed within the lungs, we hypothesized that melatonin can induce apoptosis in cancer cells, and this was not evaluated by comet assay. This study provides evidence that melatonin can reduce the genotoxicity and mutagenicity caused by B16F10 cells.

Oxidative stress mediates thalidomide-induced pain by targeting peripheral TRPA1 and central TRPV4.

BACKGROUND: The mechanism underlying the pain symptoms associated with chemotherapeutic-induced peripheral neuropathy (CIPN) is poorly understood. Transient receptor potential ankyrin 1 (TRPA1), TRP vanilloid 4 (TRPV4), TRPV1, and oxidative stress have been implicated in several rodent models of CIPN-evoked allodynia. Thalidomide causes a painful CIPN in patients via an unknown mechanism. Surprisingly, the pathway responsible for such proalgesic response has not yet been investigated in animal models. RESULTS: Here, we reveal that a single systemic administration of thalidomide and its derivatives, lenalidomide and pomalidomide, elicits prolonged (~ 35 days) mechanical and cold hypersensitivity in C57BL/6J mouse hind paw. Pharmacological antagonism or genetic deletion studies indicated that both TRPA1 and TRPV4, but not TRPV1, contribute to mechanical allodynia, whereas cold hypersensitivity was entirely due to TRPA1. Thalidomide per se did not stimulate recombinant and constitutive TRPA1 and TRPV4 channels in vitro, which, however, were activated by the oxidative stress byproduct, hydrogen peroxide. Systemic treatment with an antioxidant attenuated mechanical and cold hypersensitivity, and the increase in oxidative stress in hind paw, sciatic nerve, and lumbar spinal cord produced by thalidomide. Notably, central (intrathecal) or peripheral (intraplantar) treatments with channel antagonists or an antioxidant revealed that oxidative stress-dependent activation of peripheral TRPA1 mediates cold allodynia and part of mechanical allodynia. However, oxidative stress-induced activation of central TRPV4 mediated the residual TRPA1-resistant component of mechanical allodynia. CONCLUSIONS: Targeting of peripheral TRPA1 and central TRPV4 may be required to attenuate pain associated with CIPN elicited by thalidomide and related drugs.

Dacarbazine alone or associated with melanoma-bearing cancer pain model induces painful hypersensitivity by TRPA1 activation in mice.

Antineoplastic therapy has been associated with pain syndrome development characterized by acute and chronic pain. The chemotherapeutic agent dacarbazine, used mainly to treat metastatic melanoma, is reported to cause painful symptoms, compromising patient quality of life. Evidence has proposed that transient receptor potential ankyrin 1 (TRPA1) plays a critical role in chemotherapy-induced pain syndrome. Here, we investigated whether dacarbazine causes painful hypersensitivity in naive or melanoma-bearing mice and the involvement of TRPA1 in these models. Mouse dorsal root ganglion (DRG) neurons and human TRPA1-transfected HEK293 (hTRPA1-HEK293) cells were used to evaluate the TRPA1-mediated calcium response evoked by dacarbazine. Mechanical and cold allodynia were evaluated after acute or repeated dacarbazine administration in naive mice or after inoculation of B16-F10 melanoma cells in C57BL/6 mice. TRPA1 involvement was investigated by using pharmacological and genetic tools (selective antagonist or antisense oligonucleotide treatment and Trpa1 knockout mice). Dacarbazine directly activated TRPA1 in hTRPA1-HEK293 cells and mouse DRG neurons and appears to sensitize TRPA1 indirectly by generating oxidative stress products. Moreover, dacarbazine caused mechanical and cold allodynia in naive but not Trpa1 knockout mice. Also, dacarbazine-induced nociception was reduced by the pharmacological TRPA1 blockade (antagonism), antioxidants, and by ablation of TRPA1 expression. TRPA1 pharmacological blockade also reduced dacarbazine-induced nociception in a tumor-associated pain model. Thus, dacarbazine causes nociception by TRPA1 activation, indicating that this receptor may represent a pharmacological target for treating chemotherapy-induced pain syndrome in cancer patients submitted to antineoplastic treatment with dacarbazine.

Monosodium urate crystal interleukin-1ß release is dependent on Toll-like receptor 4 and transient receptor potential V1 activation.

OBJECTIVE: The present study aimed to elucidate the mechanisms involved in MSU-induced IL-1ß release in a rodent animal model of acute gout arthritis. METHODS: Painful (mechanical and thermal hypersensitivity, ongoing pain and arthritis score) and inflammatory (oedema, plasma extravasation, cell infiltration and IL-1ß release) parameters were assessed several hours after intra-articular injection of MSU (100 µg/articulation) in wild-type or knockout mice for Toll-like receptor 4 (TLR4), inducible nitric oxide synthase (iNOS), transient receptor potential (TRP) V1 and the IL-1 receptor (IL-1R). Also, wild-type animals were treated with clodronate, lipopolysaccharide from Rhodobacter sphaeroides (LPS-RS) (TLR4 antagonist), spleen tyrosine kinase (SYK) inhibitor (iSYK), aminoguanidine (AMG, an iNOS inhibitor) or SB366791 (TRPV1 antagonist). Nitrite/nitrate and IL-1ß levels were measured on the synovial fluid of wild-type mice, 2 h after intra-articular MSU injections, or medium from macrophages stimulated for MSU (1000 µg) for 2 h. RESULTS: Intra-articular MSU injection caused robust nociception and severe inflammation from 2 up to 6 h after injection, which were prevented by the pre-treatment with clodronate, LPS-RS, iSYK, AMG and SB366791, or the genetic ablation of TLR4, iNOS, TRPV1 or IL-1R. MSU also increased nitrite/nitrate and IL-1ß levels in the synovial fluid, which was prevented by clodronate, LPS-RS, iSYK and AMG, but not by SB366791. Similarly, MSU-stimulated peritoneal macrophages released nitric oxide, which was prevented by LPS-RS, iSYK and AMG, but not by SB366791, and released IL-1ß, which was prevented by LPS-RS, iSYK, AMG and SB366791. CONCLUSION: Our data indicate that MSU may activate TLR4, SYK, iNOS and TRPV1 to induce the release of IL-1ß by macrophages, triggering nociception and inflammation during acute gout attack.

Macrophages and Schwann cell TRPA1 mediate chronic allodynia in a mouse model of complex regional pain syndrome type I.

Complex regional pain syndrome type I (CRPS-I) is characterized by intractable chronic pain. Poor understanding of the underlying mechanisms of CRPS-I accounts for the current unsatisfactory treatment. Antioxidants and antagonists of the oxidative stress-sensitive channel, the transient receptor potential ankyrin 1 (TRPA1), have been found to attenuate acute nociception and delayed allodynia in models of CRPS-I, evoked by ischemia and reperfusion (I/R) of rodent hind limb (chronic post ischemia pain, CPIP). However, it is unknown how I/R may lead to chronic pain mediated by TRPA1. Here, we report that the prolonged (day 1-15) mechanical and cold allodynia in the hind limb of CPIP mice was attenuated permanently in Trpa1-/- mice and transiently after administration of TRPA1 antagonists (A-967079 and HC-030031) or an antioxidant (α-lipoic acid). Indomethacin treatment was, however, ineffective. We also found that I/R increased macrophage (F4/80+ cell) number and oxidative stress markers, including 4-hydroxynonenal (4-HNE), in the injured tibial nerve. Macrophage-deleted MaFIA (Macrophage Fas-Induced Apoptosis) mice did not show I/R-evoked endoneurial cell infiltration, increased 4-HNE and mechanical and cold allodynia. Furthermore, Trpa1-/- mice did not show any increase in macrophage number and 4-HNE in the injured nerve trunk. Notably, in mice with selective deletion of Schwann cell TRPA1 (Plp1-CreERT;Trpa1fl/fl mice), increases in macrophage infiltration, 4-HNE and mechanical and cold allodynia were attenuated. In the present mouse model of CRPS-I, we propose that the initial oxidative stress burst that follows reperfusion activates a feed forward mechanism that entails resident macrophages and Schwann cell TRPA1 of the injured tibial nerve to sustain chronic neuroinflammation and allodynia. Repeated treatment one hour before and for 3 days after I/R with a TRPA1 antagonist permanently protected CPIP mice against neuroinflammation and allodynia, indicating possible novel therapeutic strategies for CRPS-I.

Role of transient receptor potential ankyrin 1 (TRPA1) on nociception caused by a murine model of breast carcinoma.

Breast carcinoma causes severe pain, which decreases the quality of life of patients. Current treatments produce adverse effects and have limited efficacy. Transient potential receptor ankyrin 1 (TRPA1) is related to the onset of cancer and neuropathic pain. The aim of this study was to evaluate the involvement of TRPA1 in a model of breast carcinoma. We injected 4T1 cells in the fourth caudal mammary fat pad of female BALB/c mice, and after 20 days we observed mechanical and cold allodynia and spontaneous nociception behavior (mouse grimace scale detection, MGS). TRPA1 selective antagonist (HC-030031 or A-967079) administration or intrathecal administration of TRPA1 antisense (AS) oligonucleotide was performed. The activity of NADPH oxidase, superoxide dismutase (SOD) and hydrogen peroxide (H2O2) levels were evaluated. The chemical hyperalgesia produced by a TRPA1 agonist (allyl isothiocyanate, AITC) was also detected. The administration of TRPA1 antagonists, TRPA1 AS, or antioxidant, transiently attenuated MGS, or mechanical and cold allodynia. Intraplantar injection of AITC also caused nociception. NADPH oxidase or SOD activity and H2O2 levels were increased in the sciatic nerve and hind paw skin samples. The 4T1 cells did not express TRPA1, and the use of HC-030031 or α-lipoic acid did not reduce the cytotoxic effect of a chemotherapeutic drug (paclitaxel). Thus, TRPA1 could be investigated as a target for breast carcinoma pain treatment.

Glucocorticoid and brain-derived neurotrophic factor relationship: a brief investigation into the model of depression by chronic administration of corticosterone.

Depression is considered a common mental disorder that affects more than 300 million people worldwide. Despite this high incidence, its etiology is not completely elucidated instigating further studies. For this purpose, different animal models are used to study routes and molecular changes involved in depression, among them the chronic administration of corticosterone. However, the knowledge about neurochemical changes after this protocol is still controversial. In this work, we evaluated serum corticosterone levels, adrenal/body weight ratio, as well as glucocorticoid receptor and brain-derived neurotrophic factor protein expression and its receptor, tropomyosin-receptor kinase B. These analyzes were performed on prefrontal cortex, hippocampus, and striatum samples taken of mice after 21 days of administration of corticosterone. Exposure to corticosterone reduced the serum corticosterone levels and the adrenal/body weight ratio. Moreover, the glucocorticoid receptor and tyrosine-receptor kinase B expression were increased in the hippocampus while the brain-derived neurotrophic factor expression was reduced in the prefrontal cortex. We also found a positive correlation between the expression of glucocorticoid receptor and tyrosine-receptor kinase B and our results suggest a possible relationship between the glucocorticoid/glucocorticoid receptor and brain-derived neurotrophic factor/tropomyosin-receptor kinase B routes after chronic corticosterone administration. To our knowledge, this is the first study that evaluate these parameters concomitantly in important mood-related structures. In addition, these results may be useful to other research groups seeking to explore new pathways and substances with therapeutic potential to treat this silent epidemic.

Hydroalcoholic extract of leaf of Arachis hypogaea L. (Fabaceae) did not induce toxic effects in the repeated-dose toxicity study in rats.

Arachis hypogaea L. (peanut) leaf is traditionally used for the treatment of insomnia in Asia. However, studies describing the safety and toxicity profile for this plant preparation are limited. Thus, the goal of this study was to investigate the toxicity of peanut leaf hydroalcoholic extract (PLHE) repeated treatment. The extract was administered orally (100, 300 or 1000 mg/kg) in male and female Wistar rats for 28 days (OECD guideline 407). PLHE treatment did not cause mortality or weight variation in the animals. Also, there was no alteration on locomotor activity (open field test), motor coordination (rotarod test), or anxiety behaviour (elevated plus-maze test). Male rats had a reduction in relative liver weight (100 mg/kg) and an increase in total kidney weight (1000 mg/kg), but there was no change in biochemical and haematological parameters after PLHE treatment. Free extracellular double-stranded DNA (dsDNA) levels was also evaluated, but PLHE treatment did not increase this parameter in rat organs. Also, the dose of 1000 mg/kg of PLHE significantly increased the total thiols in the liver of females compared with the control animals. Thus, PLHE did not induce toxicity after repeated exposure for 28 days in rats.

Transient receptor potential ankyrin 1 (TRPA1) plays a critical role in a mouse model of cancer pain.

There is a major, unmet need for the treatment of cancer pain, and new targets and medicines are required. The transient receptor potential ankyrin 1 (TRPA1), a cation channel expressed by nociceptors, is activated by oxidizing substances to mediate pain-like responses in models of inflammatory and neuropathic pain. As cancer is known to increase oxidative stress, the role of TRPA1 was evaluated in a mouse model of cancer pain. Fourteen days after injection of B16-F10 murine melanoma cells into the plantar region of the right hind paw, C57BL/6 mice exhibited mechanical and thermal allodynia and thigmotaxis behavior. While heat allodynia was partially reduced in TRP vanilloid 1 (TRPV1)-deficient mice, thigmotaxis behavior and mechanical and cold allodynia were absent in TRPA1-deficient mice. Deletion of TRPA1 or TRPV1 did not affect cancer growth. Intrathecal TRPA1 antisense oligonucleotides and two different TRPA1 antagonists (HC-030031 or A967079) transiently attenuated thigmotaxis behavior and mechanical and cold allodynia. A TRPV1 antagonist (capsazepine) attenuated solely heat allodynia. NADPH oxidase activity and hydrogen peroxide levels were increased in hind paw skin 14 days after cancer cell inoculation. The antioxidant, α-lipoic acid, attenuated mechanical and cold allodynia and thigmotaxis behavior, but not heat allodynia. Whereas TRPV1, via an oxidative stress-independent pathway, contributes partially to heat hypersensitivity, oxidative stress-dependent activation of TRPA1 plays a key role in mediating thigmotaxis behavior and mechanical and cold allodynia in a cancer pain model. TRPA1 antagonists might be beneficial in the treatment of cancer pain.

Characterization of Cancer-Induced Nociception in a Murine Model of Breast Carcinoma.

Severe and poorly treated pain often accompanies breast cancer. Thus, novel mechanisms involved in breast cancer-induced pain should be investigated. Then, it is necessary to characterize animal models that are reliable with the symptoms and progression of the disease as observed in humans. Explaining cancer-induced nociception in a murine model of breast carcinoma was the aim of this study. 4T1 (104) lineage cells were inoculated in the right fourth mammary fat pad of female BALB/c mice; after this, mechanical and cold allodynia, or mouse grimace scale (MGS) were observed for 30 days. To determine the presence of bone metastasis, we performed the metastatic clonogenic test and measure calcium serum levels. At 20 days after tumor induction, the antinociceptive effect of analgesics used to relieve pain in cancer patients (acetaminophen, naproxen, codeine or morphine) or a cannabinoid agonist (WIN 55,212-2) was tested. Mice inoculated with 4T1 cells developed mechanical and cold allodynia and increased MGS. Bone metastasis was confirmed using the clonogenic assay, and hypercalcemia was observed 20 days after cells inoculation. All analgesic drugs reduced the mechanical and cold allodynia, while the MGS was decreased only by the administration of naproxen, codeine, or morphine. Also, WIN 55,212-2 improved all nociceptive measures. This pain model could be a reliable form to observe the mechanisms of breast cancer-induced pain or to observe the efficacy of novel analgesic compounds.

Peanut leaf extract has antioxidant and anti-inflammatory activity but no acute toxic effects.

Arachis hypogaea L. (peanut) leaves have been popularly used for the treatment of insomnia and inflammation, but no toxicological study has been performed for this plant preparation. This study aimed to examine the phytochemical composition of peanut leaf hydroalcoholic extract (PLHE) and describe its potential toxic effects and antioxidant and anti-inflammatory properties. The qualitative chemical analysis of PLHE by UHPLC-ESI-HRMS allowed the identification of eight metabolites types (totaling 29 compounds). The 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay revealed that PLHE had strong antioxidant effects; it also exhibited nitric oxide (NO)-scavenging capacity. Human peripheral blood mononuclear cells (PBMCs) exposed to PLHE showed no reduced cell viability or increased free double-stranded DNA, NO, or reactive species production. PLHE reversed the cytotoxicity, pro-inflammatory (release of interleukin-1ß), and pro-oxidant effects of H2O2 on human PBMCs. Acute PLHE toxicity analysis was performed in vivo using the Organization for Economic Co-operation and Development (OECD) 423 guidelines. PLHE single injection (2000 mg/kg, intragastric) did not cause mortality or morbidity or induce changes in hematological or biochemical parameters after 14 days of administration. Thus, PLHE could be a source of bioactive compounds and possesses antioxidant and anti-inflammatory properties without elicitin cytotoxicity or genotoxicity in human PBMCs or acute toxicity in rats.

Antinociceptive activity of Copaifera officinalis Jacq. L oil and kaurenoic acid in mice.

Copaifera officinalis L. possesses traditional uses as an analgesic, anti-inflammatory, and antiseptic. However, until now the antinociceptive effect and the mechanism of action were not described for Copaifera officinalis L. oil and no compound present in this oil was identified to be responsible for its biological effects. The goal of this study was to identify the presence of kaurenoic acid in Copaifera officinalis oil and investigate its antinociceptive effect, mechanism of action, and possible adverse effects in mice. The quantification of kaurenoic acid in Copaifera officinalis oil was done by HPLC-DAD technique. Male and female albino Swiss mice (25-35 g) were used to test the antinociceptive effect of Copaifera officinalis (10 mg/kg, intragastric) or kaurenoic acid (1 mg/kg) in the tail-flick test, intraplantar injection of capsaicin, allyl isothiocyanate (AITC) or complete Freund's adjuvant (CFA). Copaifera officinalis oil and kaurenoic acid caused the antinociceptive effect in the tail-flick test in a dose-dependent manner, and their effect was reversed by naloxone (an opioid antagonist). Copaifera officinalis oil or kaurenoic acid reduced the nociception caused by capsaicin or AITC and produced an anti-allodynic effect in the CFA model (after acute or repeated administration for 7 days). Possible adverse effects were also observed, and non-detectable adverse effect was observed for the intragastric administration of Copaiba officinalis oil or kaurenoic acid and in the same way, the treatments were neither genotoxic nor mutagenic at the doses tested. Thus, Copaiba officinalis oil, and kaurenoic acid possess antinociceptive action without adverse effects.

Buddleja thyrsoides Lam. crude extract presents antinociceptive effect on an arthritic pain model in mice.

Arthritis is a chronic inflammatory disease which reduces the life quality of affected individuals. Therapeutic tools used for treating inflammatory pain are associated with several undesirable effects. Buddleja thyrsoides Lam., known as 'Barbasco' or 'Cambara', is mostly used in several disorders and possesses antirheumatic, anti-inflammatory, and analgesic properties. Here, we investigated the antinociceptive and anti-inflammatory effects of the B. thyrsoides crude extract applied orally and topically in acute pain models and an arthritic pain model induced by complete Freund's adjuvant (CFA) paw injection in male mice (25-30 g). The high-performance liquid chromatography (HPLC) of the B. thyrsoides extract crude revealed the presence of the lupeol, stigmasterol, and ß-sitosterol. The stability study of the B. thyrsoides gel did not show relevant changes at low temperatures. The oral treatment with the B. thrysoides extract prevented the capsaicin-induced spontaneous nociception and the acetic acid-induced abdominal writhing, but did not alter the thermal threshold in the tail immersion test. The B. thyrsoides antinociceptive effect was not reversed by naloxone in the capsaicin test. The B. thyrsoides oral or topical treatment reversed the CFA-induced mechanical allodynia and thermal hyperalgesia with maximum inhibition (Imax) of 69 ± 6 and 68 ± 5% as well as 78 ± 15 and 87 ± 12%, respectively. Moreover, the topical but not oral treatment inhibited the CFA-induced cell infiltration, but did not reduce the paw edema significantly. The oral treatment with B. thyrsoides did not cause adverse effects. These findings suggest that the oral or topical treatment with B. thyrsoides presents antinociceptive actions in an arthritic pain model without causing adverse effects.

TRPA1 mediates trigeminal neuropathic pain in mice downstream of monocytes/macrophages and oxidative stress.

Despite intense investigation, the mechanisms of the different forms of trigeminal neuropathic pain remain substantially unidentified. The transient receptor potential ankyrin 1 channel (encoded by TRPA1) has been reported to contribute to allodynia or hyperalgesia in some neuropathic pain models, including those produced by sciatic nerve constriction. However, the role of TRPA1 and the processes that cause trigeminal pain-like behaviours from nerve insult are poorly understood. The role of TRPA1, monocytes and macrophages, and oxidative stress in pain-like behaviour evoked by the constriction of the infraorbital nerve in mice were explored. C57BL/6 and wild-type (Trpa1(+/+)) mice that underwent constriction of the infraorbital nerve exhibited prolonged (20 days) non-evoked nociceptive behaviour and mechanical, cold and chemical hypersensitivity in comparison to sham-operated mice (P < 0.05-P < 0.001). Both genetic deletion of Trpa1 (Trpa1(-/-)) and pharmacological blockade (HC-030031 and A-967079) abrogated pain-like behaviours (both P < 0.001), which were abated by the antioxidant, α-lipoic acid, and the nicotinamide adenine dinucleotide phosphate oxidase inhibitor, apocynin (both P < 0.001). Nociception and hypersensitivity evoked by constriction of the infraorbital nerve was associated with intra- and perineural monocytic and macrophagic invasion and increased levels of oxidative stress by-products (hydrogen peroxide and 4-hydroxynonenal). Attenuation of monocyte/macrophage increase by systemic treatment with an antibody against the monocyte chemoattractant chemokine (C-C motif) ligand 2 (CCL2) or the macrophage-depleting agent, clodronate (both P < 0.05), was associated with reduced hydrogen peroxide and 4-hydroxynonenal perineural levels and pain-like behaviours (all P < 0.01), which were abated by perineural administration of HC-030031, α-lipoic acid or the anti-CCL2 antibody (all P < 0.001). The present findings propose that, in the constriction of the infraorbital nerve model of trigeminal neuropathic pain, pain-like behaviours are entirely mediated by the TRPA1 channel, targeted by increased oxidative stress by-products released from monocytes and macrophages clumping at the site of nerve injury.

Antinociceptive effect of a novel armed spider peptide Tx3-5 in pathological pain models in mice.

The venom of the Brazilian armed spider Phoneutria nigriventer is a rich source of biologically active peptides that have potential as analgesic drugs. In this study, we investigated the analgesic and adverse effects of peptide 3-5 (Tx3-5), purified from P. nigriventer venom, in several mouse models of pain. Tx3-5 was administered by intrathecal injection to mice selected as models of postoperative (plantar incision), neuropathic (partial sciatic nerve ligation) and cancer-related pain (inoculation with melanoma cells) in animals that were either sensitive or tolerant to morphine. Intrathecal administration of Tx3-5 (3-300 fmol/site) in mice could either prevent or reverse postoperative nociception, with a 50 % inhibitory dose (ID50) of 16.6 (3.2-87.2) fmol/site and a maximum inhibition of 87 ± 10 % at a dose of 30 fmol/site. Its effect was prevented by the selective activator of L-type calcium channel Bay-K8644 (10 µg/site). Tx3-5 (30 fmol/site) also produced a partial antinociceptive effect in a neuropathic pain model (inhibition of 67 ± 10 %). Additionally, treatment with Tx3-5 (30 fmol/site) nearly abolished cancer-related nociception with similar efficacy in both morphine-sensitive and morphine-tolerant mice (96 ± 7 and 100 % inhibition, respectively). Notably, Tx3-5 did not produce visible adverse effects at doses that produced antinociception and presented a TD50 of 1125 (893-1418) fmol/site. Finally, Tx3-5 did not alter the normal mechanical or thermal sensitivity of the animals or cause immunogenicity. Our results suggest that Tx3-5 is a strong drug candidate for the treatment of painful conditions.

The role of kinin B1 receptor and the effect of angiotensin I-converting enzyme inhibition on acute gout attacks in rodents.

OBJECTIVE: Verify the role of the kinin B1 receptors (B1R) and the effect of ACE inhibitors (ACEi) on acute gout induced by monosodium urate (MSU) crystals in rodents. METHODS: Painful (overt pain and allodynia) and inflammatory parameters (joint oedema, leukocyte trafficking, interleukin-1ß levels) of acute gout attacks were assessed several hours after an intra-articular injection of MSU (1.25 or 0.5 mg/articulation) into the ankle of rats or mice, respectively. The role of B1R was investigated using pharmacological antagonism or gene deletion. Additionally, B1R immunoreactivity in ankle tissue and sensory neurons, kininase I activity and des-Arg(9)-bradykinin synovial levels were also measured. Similar tools were used to investigate the effects of ACEi on a low dose of MSU (0.0125 mg/articulation)-induced inflammation. RESULTS: Kinin B1R antagonism or gene deletion largely reduced all painful and inflammatory signs of gout. Furthermore, MSU increased B1R expression in articular tissues, the content of the B1 agonist des-Arg(9)-bradykinin and the activity of the B1 agonist-forming enzyme kininase I. A low dose of MSU crystals, which did not induce inflammation in control animals, caused signs of acute gout attacks in ACEi-treated animals that were B1R-dependent. CONCLUSIONS: Kinin B1R contributes to acute gouty attacks, including the ones facilitated by ACEi. Therefore, B1R is a potential therapeutic target for the treatment and prophylaxis of gout, especially in patients taking ACEi.