Analysis of the Effect of the TRPC4/TRPC5 Blocker, ML204, in Sucrose-Induced Metabolic Imbalance

Sugar-induced metabolic imbalances are a major health problem since an excessive consumption of saccharides has been linked to greater obesity rates at a global level. Sucrose, a disaccharide composed of 50% glucose and 50% fructose, is commonly used in the food industry and found in a range of fast, restaurant, and processed foods. Herein, we investigated the effects of a TRPC4/TRPC5 blocker, ML204, in the metabolic imbalances triggered by early exposure to sucrose-enriched diet in mice. TRPC4 and TRPC5 belong to the family of non-selective Ca+2 channels known as transient receptor potential channels. High-sucrose (HS)-fed animals with hyperglycaemia and dyslipidaemia, were accompanied by increased body mass index. mesenteric adipose tissue accumulation with larger diameter cells and hepatic steatosis in comparison to those fed normal diet. HS mice also exhibited enhanced adipose, liver, and pancreas TNFα and VEGF levels. ML204 exacerbated hyperglycaemia, dyslipidaemia, fat tissue deposition, hepatic steatosis, and adipose tissue and liver TNFα in HS-fed mice. Normal mice treated with the blocker had greater hepatic steatosis and adipose tissue cell numbers/diameter than those receiving vehicle, but showed no significant changes in tissue inflammation, glucose, and lipid levels. The results indicate that TRPC4/TRPC5 protect against the metabolic imbalances caused by HS ingestion.

Automated preclinical detection of mechanical pain hypersensitivity and analgesia

ABSTRACT

The lack of sensitive and robust behavioral assessments of pain in preclinical models has been a major limitation for both pain research and the development of novel analgesics. Here, we demonstrate a novel data acquisition and analysis platform that provides automated, quantitative, and objective measures of naturalistic rodent behavior in an observer-independent and unbiased fashion. The technology records freely behaving mice, in the dark, over extended periods for continuous acquisition of 2 parallel video data streams: (1) near-infrared frustrated total internal reflection for detecting the degree, force, and timing of surface contact and (2) simultaneous ongoing video graphing of whole-body pose. Using machine vision and machine learning, we automatically extract and quantify behavioral features from these data to reveal moment-by-moment changes that capture the internal pain state of rodents in multiple pain models. We show that these voluntary pain-related behaviors are reversible by analgesics and that analgesia can be automatically and objectively differentiated from sedation. Finally, we used this approach to generate a paw luminance ratio measure that is sensitive in capturing dynamic mechanical hypersensitivity over a period and scalable for high-throughput preclinical analgesic efficacy assessment.

Water soluble microparticles of Sambucus nigra L. (elderberry) as a potential herbal medicine

Although traditional use of elderberry flowers is recognized by Medical Agencies, there are not suitable products on the Brazilian market. To overcome poor stability of tinctures of Sambucus nigra flowers, we aimed to develop spray dried microparticles. Statistical experimental design was applied taking inlet temperature and maltodextrin% at five different levels. Next, we applied a stability study for 60 days under accelerated conditions (40 °C/75% RH) and 180 days at room temperature (15-30 °C). We monitored flavonoid content as markers. The best drying condition was 188 °C and 65% of carrier and enabled microparticles with more than 90% of markers recovery. After 180 days, the dried extract remained with 90.8% at room temperature. The markers were released from microparticles in two minutes. In conclusion, the spray drying process and formulation enabled elderberry flowers to be easier to apply in solid pharmaceutical forms.

Taxane-induced neurotoxicity: Pathophysiology and therapeutic perspectives

Taxane-derived drugs are antineoplastic agents used for the treatment of highly common malignancies. Paclitaxel and docetaxel are the most commonly used taxanes; however, other drugs and formulations have been used, such as cabazitaxel and nab-paclitaxel. Taxane treatment is associated with neurotoxicity, a well-known and relevant side effect, very prevalent amongst patients undergoing chemotherapy. Painful peripheral neuropathy is the most dose-limiting side effect of taxanes, affecting up to 97% of paclitaxel-treated patients. Central neurotoxicity is an emerging side effect of taxanes and it is characterized by cognitive impairment and encephalopathy. Besides impairing compliance to chemotherapy treatment, taxane-induced neurotoxicity (TIN) can adversely affect the patient's life quality on a long-term basis. Despite the clinical relevance, not many reviews have comprehensively addressed taxane-induced neurotoxicity when they are used therapeutically. This article provides an up-to-date review on the pathophysiology of TIN and the novel potential therapies to prevent or treat this side effect.

Biological and Toxicological Evaluation of N-(4methyl-phenyl)-4-methylphthalimide on Bone Cancer in Mice

BACKGROUND

It was recently demonstrated that the phthalimide N-(4-methyl-phenyl)-4- methylphthalimide (MPMPH-1) has important effects against acute and chronic pain in mice, with a mechanism of action correlated to adenylyl cyclase inhibition. Furthermore, it was also demonstrated that phthalimide derivatives presented antiproliferative and anti-tumor effects. Considering the literature data, the present study evaluated the effects of MPMPH-1 on breast cancer bone metastasis and correlated painful symptom, and provided additional toxicological information about the compound and its possible metabolites.

METHODS

In silico toxicological analysis was supported by in vitro and in vivo experiments to demonstrate the anti-tumor and anti-hypersensitivity effects of the compound.

RESULTS

The data obtained with the in silico toxicological analysis demonstrated that MPMPH-1 has mutagenic potential, with a low to moderate level of confidence. The mutagenicity potential was in vivo confirmed by micronucleus assay. MPMPH-1 treatments in the breast cancer bone metastasis model were able to prevent the osteoclastic resorption of bone matrix. Regarding cartilage, degradation was considerably reduced within the zoledronic acid group, while in MPMPH-1, chondrocyte multiplication was observed in random areas, suggesting bone regeneration. Additionally, the repeated treatment of mice with MPMPH-1 (10 mg/kg, i.p.), once a day for up to 36 days, significantly reduces the hypersensitivity in animals with breast cancer bone metastasis.

CONCLUSION

Together, the data herein obtained show that MPMPH-1 is relatively safe, and significantly control the cancer growth, allied to the reduction in bone reabsorption and stimulation of bone and cartilage regeneration. MPMPH-1 effects may be linked, at least in part, to the ability of the compound to interfere with adenylylcyclase pathway activation.

Quantification of Sambucus nigra (Adoxaceae) Markers Related to Tincture Stability

Stability tests are essential to assuring herbal derivative quality, especially because of the complexity of the herbal matrix. To monitor the stability of Sambucus nigra L. flower tincture, a practical liquid chromatography (LC)-UV method was developed and validated. Rutin, the flower's pharmacopeial marker, in addition to other markers, isoquercitrin and quercetin, were quantified. The last two represent the degradation products of glycosylated flavonoids. In addition, other chromatographic peaks exhibiting typical flavonoid UV absorption profiles (total flavonoids) were also quantified and expressed in rutin equivalents. The method was developed with a reverse phase C18 column, using a gradient mobile phase at 0.7 mL min -1 at 30°C. The herbal drug and tincture obtained by percolation at 60 °C with ethanol 25% (v/v) were submitted to accelerated (40°C/75% RH, 2 months) and long duration (15–30°C, 6 months) studies. The LC-UV method was linear in the ranges of 1–200 μg mL-1 (rutin) and 1–100 μg mL-1 (isoquercitrin and quercetin), without interference of herbal matrix, and was precise (RSD ≤ 2.0% for intra and interday precision), selective, and robust (changes in mobile phase flow, pH and temperature). The tincture revealed the presence of quercetin, which was absent in the herbal drug, likely due to the hydrolysis process. After 2 months under accelerated study, the total flavonoids in the tincture decreased by approximately 20%, and after 6 months at room temperature, they decreased by approximately 30%. These results indicate the thermolability of the S. nigra tincture and the importance of monitoring phytomedicine stability.

Anti-hyperalgesic effects of two sphingosine derivatives in different acute and chronic models of hyperalgesia in mice

BACKGROUND

The study evaluated the effects of two sphingosine derivatives N-(2-tert-butoxycarbamylhexadecyl)glutaramide (AA) and N-(1-benzyloxyhexadec-2-yl)glutaramide (OA) in different models of hypersensitivity in mice.

METHODS

Male Swiss mice were orally pre-treated with AA or OA (0.3-3mg/kg). After 1h, they received λ-carrageenan (300μg/paw), lipopolysaccharide (LPS; 100ng/paw), bradykinin (BK; 500ng/paw) or prostaglandin E₂ (PGE₂; 0.1nmol/paw) or epinephrine (100ng/paw), and the mechanical withdrawal thresholds were evaluated using von Frey filament (0.6g) at different time points. The effect of the compounds against inflammatory and neuropathic pain was also evaluated using complete Freund's adjuvant (CFA), or by performing partial sciatic nerve ligation (PSNL).

RESULTS

Animals pre-treated with AA and OA reduced hypersensitivity induced by carrageenan, LPS and BK, and modest inhibition of PGE₂-induced hypersensitivity and carrageenan-induced paw oedema were observed in mice treated with OA. Though the partial effect presented by AA and OA, when dosed once a day, both compounds were able to significantly reduce the persistent inflammatory and neuropathic pain induced by CFA and PSNL, respectively.

CONCLUSION

These results demonstrate that the sphingosine derivatives AA and OA present important anti-hypersensitive effects, suggesting a possible interaction with the kinin signalling pathway. This may represent an interesting tool for the management of acute and chronic pain, with good bioavailability and safety.

Cytotoxic, antitumour and antimetastatic activity of two new polyacetylenes isolated from Vernonia scorpioides (Lam.) Pers

Vernonia scorpioides (Lam.) Pers., popularly known as Enxuga, Erva-de-São Simão and Piracá, has been used in folk medicine for its anti-inflammatory, wound healing and antimicrobial properties. Two polyacetylenes, 5-octa-2,4,6-triynyl-furan-2(5H)-one (1) and 8'-hydroxy 3-4 dihydrovernoniyne (2), were isolated from the dichloromethane extract fraction of V. scorpioides. In this study, polyacetylene 1 demonstrated a more potent cytotoxic activity than 2 in the tumour cell lines examined, and cytotoxicity was found to be comparable to a commercial drug (p > 0.05) in melanoma cells. No significant cytotoxic effect was observed in normal cell lines. Furthermore, polyacetylene 1 induced an in vitro increase in caspase-3 activity in B16F10 cells. When polyacetylene 1 was administered intraperitoneally (i.p.) in mice, a reduction in solid tumour volume and metastasis was observed in mice injected with B16F10 cells. An increase in locomotor activity was also observed in mice with solid tumours, and an inhibition of mechanical hypersensitivity was observed in a mouse model of metastasis. Notably, no significant morphological change was observed in several organs harvested from the treated mice. In conclusion, in vitro and in vivo anticancer activity of polyacetylene 1 was consistently observed and involved the induction of apoptosis by the activation of caspase-3. The anticancer activity demonstrated by polyacetylene 1, together with the absence of preliminary toxicological effects, represents a new and interesting option for the management of neoplastic disease.

Antinociceptive, anti-inflammatory and wound healing features in animal models treated with a semisolid herbal medicine based on Aleurites moluccana L. Willd. Euforbiaceae standardized leaf extract: semisolid herbal

ETHNOPHARMACOLOGICAL RELEVANCE

Aleurites moluccana L. (Willd) Euforbiaceae is a native tree of Indonesia and India that has become acclimatized and well-adapted to the South and Southwest of Brazil. It is commonly used in traditional medicine to treat pain, fever, inflammation, asthma, hepatitis, headache, gastric ulcer, cuts, skin sores and other ailments. The oral antinociceptive effects of standardized 70:30 (v/v) ethanol:water spray dried extract of A. moluccana leaf, as well as its flavonoids 2"-O-rhamnosylswertisin (I) and swertisin (II), have previously been reported.

AIM

The aim of this study was to develop a stable and effective semisolid herbal medicine for topical use in the treatment of pain, inflammation and wound healing, containing 0.5 and 1.0% of standardized dried extract of A. moluccana.

MATERIALS AND METHODS

The chemical markers I and II were assayed by HPLC-UV analysis after extraction by matrix solid dispersion phase (MSDP) followed analytical validation as ICH Guidelines. The semisolid preparations of Hostacerin CG(®) vehicle containing 0.5 and 1.0% of dried extract of A. moluccana were submitted to stability studies (180 day of accelerated and long-term studies). The phytomedicine semisolid was analysed in croton oil-induced ear oedema model in mice, in the healing process, using the excisional wound model in rats, and to prevent mechanical sensitization following plantar incision in rats in the postoperative model of pain.

RESULTS

The MSDP method showed average recovery of 101.6 and 105.7% for I and II, respectively, with good precision (RSD<2.0%) and selectivity, without interference of the excipients. The formulations were approved in the stability studies, maintaining conformity after 180 day of accelerated and long-term studies, with variation<10% in the analytical parameters. The phytomedicine reduced the ear oedema in 37.6±5.7% and 64.8±6.2%, for 0.5 and 1.0% of dried extract, respectively. The formulation also accelerated the healing process by up to 50.8±4.1% and 46.0±4.0% at 0.5 and 1.0% of extract, respectively, and both amounts were capable of preventing the development of mechanical sensitization following plantar incision in rats.

CONCLUSIONS

The MSDP followed by HPLC-UV analytical method was appropriate for the quality control of the topical phytomedicine based on A. moluccana. The formulation developed at 0.5 and 1.0% of A. moluccana dried extract proved to be effective as an analgesic, anti-inflammatory and wound healing in the pre-clinical studies, which is in agreement with the ethnopharmacological data.

Antihyperalgesic activity of the methanol extract and some constituents obtained from Polygala cyparissias (Polygalaceae)

Polygala cyparissias, used in folk medicine as an anaesthetic, has already demonstrated antinociceptive activity against acute pain. In this study, we investigated the antihyperalgesic activity of the P. cyparissias methanol extract (PCME) from which the following compounds were isolated: α-spinasterol (PC1), 1,3-dihydroxy-7-methoxyxanthone (PC2), 1,7-dihydroxy-2,3-methylenedioxyxanthone (PC3) and 1,3,6,8-tetrahydroxy-2,7-dimethoxyxanthone (PC4). The antihyperalgesic effect was evaluated using experimental models of persistent pain induced by carrageenan, lipopolysaccharide (LPS), Freund's Complete Adjuvant (CFA), PGE(2) or epinephrine. The partial ligation of the sciatic nerve (PLSN) model was also used. In inflammatory hyperalgesia induced by carrageenan, LPS, CFA or PGE(2), the inhibition values obtained with the PCME treatment were 68 ± 3%, 89 ± 5%, 43 ± 3% and 40 ± 4%, respectively. In epinephrine-induced hyperalgesia, the extract was effective, reducing 99 ± 11% of response frequency, while in PLSN, 54 ± 4% of inhibition was obtained. These results allow to suggest that the antihyperalgesic activity of PCME is, at least in part, related to its capability to inhibit the hypersensitization induced by pro-inflammatory mediators, such as LPS, carrageenan and CFA, without interfering with locomotor activity or motor performance. Furthermore, compounds PC1, PC3 and PC4 inhibited the carrageenan-induced hyperalgesia with inhibition of 42 ± 6%, 48 ± 5% and 64 ± 4%, respectively. In summary, our data demonstrate that PCME has relevant antihyperalgesic activity and that the isolated PC1, PC3 and PC4 seem to be responsible, at least in part, for this important effect.

Cannabinoid agonists inhibit neuropathic pain induced by brachial plexus avulsion in mice by affecting glial cells and MAP kinases

Background

Many studies have shown the antinociceptive effects of cannabinoid (CB) agonists in different models of pain. Herein, we have investigated their relevance in neuropathic pain induced by brachial plexus avulsion (BPA) in mice.

Methodology/Principal Findings

Mice underwent BPA or sham surgery. The mRNA levels and protein expression of CB₁ and CB₂ receptors were assessed by RT-PCR and immunohistochemistry, respectively. The activation of glial cells, MAP kinases and transcription factors were evaluated by immunohistochemistry. The antinociceptive properties induced by cannabinoid agonists were assessed on the 5^th and 30^th days after surgery. We observed a marked increase in CB₁ and CB₂ receptor mRNA and protein expression in the spinal cord and dorsal root ganglion, either at the 5^th or 30^th day after surgery. BPA also induced a marked activation of p38 and JNK MAP kinases (on the 30^th day), glial cells, such as microglia and astrocytes, and the transcription factors CREB and NF-κB (at the 5^th and 30^th days) in the spinal cord. Systemic treatment with cannabinoid agonists reduced mechanical allodynia on both the 5^th and 30^th days after surgery, but the greatest results were observed by using central routes of administration, especially at the 30^th day. Treatment with WIN 55,212-2 prevented the activation of both glial cells and MAP kinases, associated with an enhancement of CREB and NF-κB activation.

Conclusions/Significance

Our results indicate a relevant role for cannabinoid agonists in BPA, reinforcing their potential therapeutic relevance for the management of chronic pain states.

N-antipyrine-3, 4-dichloromaleimide, an effective cyclic imide for the treatment of chronic pain: the role of the glutamatergic system

BACKGROUND

In recent years, cyclic imides have attracted the attention of the scientific community because of their promising therapeutic potential. Studies with the compound N-antipyrine-3,4-dichloromaleimide (NA-3,4-DCM) also demonstrated an antinociceptive effect in formalin or capsaicin models of nociception, and that it reduced acetic acid-induced abdominal writhing in mice.

METHODS

In this study, we examined the effects of NA-3,4-DCM on mechanical hypernociception in persistent pain-like behavioral models in mice. We also investigated the peripheral, topical, spinal, and supraspinal antinociceptive properties of NA-3,4-DCM and evaluated the involvement of the glutamatergic system on the antinociceptive effects of NA-3,4-DCM in mice.

RESULTS

NA-3,4-DCM, dosed systemically (intraperitoneally or per os), was capable of interfering with the development of mechanical hypernociception induced by intraplantar injection of carrageenan and complete Freund adjuvant in mice. Interestingly, repeated intraperitoneal or per os treatment with NA-3,4-DCM, administered after the induction of hypernociception, also reversed the mechanical sensitization induced by complete Freund adjuvant injection or partial ligation of the sciatic nerve in mice, with lower doses than gabapentin, a drug used clinically to treat chronic pain. When administered systemically, locally, spinally, or supraspinally, NA-3,4-DCM was able to inhibit the overt nociception of both phases of the formalin test. The systemic administration of NA-3,4-DCM also reduced the nociception induced by intraplantar or intrathecal injection of glutamate in mice. Furthermore, NA-3,4-DCM caused marked inhibition of the nociceptive response induced by intrathecal injection of a group I metabotropic glutamate receptors agonist (1S,3R)-aminocyclopentane-trans-1,3-dicardboxylic acid (ACPD) or N-methyl-d-aspartate (NMDA), without interfering with nociception induced by other non-NMDA receptor agonists (alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid and kainate) or by substance P. Notably, in the same range of doses, the antinociception caused by the compound NA-3,4-DCM was not associated with nonspecific effects such as changes in locomotor activity or motor coordination.

CONCLUSION

These results provide strong evidence that NA-3,4-DCM produces antihypernociception in mice at peripheral, spinal, and supraspinal sites, and that interaction with the group I metabotropic glutamate receptors and NMDA receptors contributes to the mechanisms underlying its effect.

Anti-inflammatory and antinociceptive effects of Baccharis dracunculifolia DC (Asteraceae) in different experimental models

AIM OF THE STUDY

The aerial parts of Baccharis dracunculifolia D.C., popularly known as "alecrim do campo", are used in folk medicine as anti-inflammatory. The aim of the present study was to evaluate the anti-inflammatory and antinociceptive activities of the crude hydroalcoholic extract obtained from leaves of Baccharis dracunculifolia (BdE), which have not been reported.

MATERIALS AND METHODS

BdE was analyzed by HPLC and in vivo evaluated (doses ranging from 50 to 400mg/kg, p.o.) by using the acetic acid-induced abdominal constrictions, paw oedema induced by carrageenan or histamine, overt nociception models using capsaicin, glutamate or phorbol myristate acetate (PMA), formalin-induced nociception and mechanical hypernociception induced by carrageenan or complete Freund adjuvant (CFA). As positive controls it was used paracetamol in both acetic acid and formalin tests; dipyrone in capsaicin, glutamate and PMA-induced nociception; indomethacin in CFA and carrageenan-induced hypernociception models. In addition, the in vitro effects of BdE on COX-2 activity and on the activation of NF-kappaB were also evaluated.

RESULTS

BdE (50-400mg/kg, p.o.) significantly diminished the abdominal constrictions induced by acetic acid, glutamate and CFA. Furthermore, BdE also inhibited the nociceptive responses in both phases of formalin-induced nociception. BdE, administered orally, also produced a long-lasting anti-hypernociceptive effect in the acute model of inflammatory pain induced by carrageenan. It was also observed the inhibition of COX-2 activity by BdE.

CONCLUSION

In summary, the data reported in this work confirmed the traditional anti-inflammatory indications of Baccharis dracunculifolia leaves and provided biological evidences that Baccharis dracunculifolia, like Brazilian green propolis, possess antinociceptive and anti-inflammatory activities.

Evidence for the role of neurogenic inflammation components in trypsin-elicited scratching behaviour in mice

BACKGROUND AND PURPOSE

We investigated the mechanisms underlying the pruritogenic response induced by trypsin in mice, to assess the relevance of neurogenic inflammation components in this response.

EXPERIMENTAL APPROACH

Itching was induced by an intradermal injection of trypsin in the mouse neck. The animals were observed for 40 min and their scratching behaviour was quantified.

KEY RESULTS

Trypsin-induced itching was blocked by the lima bean trypsin inhibitor, the selective proteinase-activated receptor-2 (PAR-2) antagonist FSLLRY and PAR-2 receptor desensitization. An important involvement of mast cells was observed, as chronic pretreatment with the mast cell degranulator compound 48/80 or the mast cell stabilizer disodium cromoglycate prevented scratching. Also, trypsin response was inhibited by the selective COX-2 inhibitor celecoxib and by the selective kinin B2 (FR173657) and B1 (SSR240612) receptor antagonists. Moreover, an essential role for the mediators of neurogenic inflammation was established, as the selective NK1 (FK888), NK3 (SR142801) and calcitonin gene-related peptide (CGRP(8-37) fragment) receptor antagonists inhibited trypsin-induced itching. Similarly, blockade of transient receptor potential vanilloid 1 (TRPV1) receptors by the selective TRPV1 receptor antagonist SB366791, or by genetic deletion of TRPV1 receptor reduced this behaviour in mice. C-fibre desensitization showed a very similar result.

CONCLUSIONS AND IMPLICATIONS

Trypsin intradermal injection proved to be a reproducible model for the study of itching and the involvement of PAR-2 receptors. Also, trypsin-induced itching seems to be widely dependent on neurogenic inflammation, with a role for TRPV1 receptors. In addition, several other mediators located in the sensory nerves and skin also seem to contribute to this process.

Evaluation of the effects of the herbal product Catuama in inflammatory and neuropathic models of nociception in rats

Here we evaluated the antinociceptive effects of the herbal drug Catuama in rat inflammatory and neuropathic models of pain, in order to assess some of the mechanisms involved in its actions. Catuama given orally, in both acute and chronic schedules of treatment, consistently inhibited the mechanical allodynia induced by the intraplantar (i.pl.) injection of complete Freund's adjuvant (CFA). The same treatment with Catuama failed to significantly affect CFA-caused thermal hyperalgesia. In addition, Catuama did not significantly modify the mechanical allodynia or hyperalgesia observed following the partial ligation of the sciatic nerve or the diabetic polyneuropathy, respectively. In another series of experiments, Catuama caused a striking reduction of the mechanical allodynia induced by LPS. Oral treatment with Catuama was not, however, effective in altering the production of the pro-inflammatory mediators IL-1beta, TNFalpha, PGE(2) or LTB(4) following i.pl. administration of LPS in the rat paw. Of high interest, the antinociceptive effects of Catuama in the LPS model were reversed significantly by the non-selective dopamine antagonist haloperidol, but not by serotonin methysergide or adrenergic yohimbine receptor antagonists. Our results indicate that the herbal drug Catuama diminishes inflammatory, but not neuropathic, nociceptive responses in rats, by mechanisms involving an interference with dopaminergic pathways. Catuama might represent a potential therapeutic tool for the management of persistent inflammatory pain.

Mechanisms underlying the nociceptive and inflammatory responses induced by trypsin in the mouse paw

It has been demonstrated that trypsin is able to evoke the classical signals of inflammation, mainly via the activation of proteinase-activated receptor-2 (PAR-2). This study was designed to evaluate the inflammatory and nociceptive responses caused by trypsin injection in the mouse paw. Trypsin produced a dose- and time-related paw edema, a response that was markedly reduced in PAR-2-deficient mice compared to wild-type mice, particularly at the early time-points after trypsin injection. In addition, trypsin produced an increase in myeloperoxidase (MPO) activity, which was significantly reduced in PAR-2-deficient mice. The injection of trypsin into the mouse paw also elicited a dose- and time-dependent spontaneous nociception, as well as thermal and mechanical hypernociceptive responses, which were consistently decreased in mice with genetic deletion of PAR-2. Pharmacological evaluation revealed that edema formation and spontaneous nociception caused by trypsin injection in the mouse paw are mediated by a complex range of mediators. Both edema and nociception seem to rely on the production of neuropeptides, probably involving C-fibre activation and vanilloid receptor-1 (TRPV1), besides the stimulation of kinin B(2) receptors. Edematogenic response is also likely related to the production of cyclooxygenase (COX) metabolites, whereas the mast cell activation appears to be greatly associated to spontaneous nociception. Altogether, the present results indicate that trypsin-induced edema and nociception in the mouse paw represent multi-mediated responses that are largely, but not exclusively, related to the activation of PAR-2. These pieces of evidence provide new insights on the role of trypsin in pain and inflammation.

Anti-hypernociceptive properties of agmatine in persistent inflammatory and neuropathic models of pain in mice

The present study examined the anti-hypernociceptive effects of agmatine (AGM) in acute and chronic models of behavioural pain in mice. Agmatine (30 mg/kg, i.p. 30 min early), produced time-dependent inhibition of mechanical hypernociception induced by Complete Freund's Adjuvant (CFA) injected in the mice paw (inhibition of 52+/-7%) after 4 h. Given chronically (twice a day) during 10 days, AGM significantly reversed the mechanical hypernociception caused by CFA (inhibition of 43+/-6% to 67+/-5%). Moreover, AGM also significantly reduced the mechanical hypernociception caused by partial sciatic nerve ligation (PSNL) during 6 h, with inhibition of 81+/-8%. In thermal hypernociception (cold stimuli) caused by PSNL the antinociceptive effect of AGM was prolonged by 4 h with inhibition of 97+/-3% observed 1 h after the treatment. Nevertheless, AGM failed to inhibit the paw oedema caused by CFA and the myeloperoxidase enzyme activity. Of note, AGM (10-100 mg/kg, i.p., 30 min before) also elicited a pronounced inhibition of the biting response induced by TNF-alpha and IL-1beta in mice, with mean ID(50) values of 61.3 mg/kg (47.7-78.6 mg/kg) and 30.4 mg/kg (18.6-49.8 mg/kg) and inhibitions of 75+/-5% and 66+/-6%, respectively. Together, present and previous findings show that AGM given systemically is effective in inhibiting mechanical and thermal hypernociception present in chronic inflammatory processes caused by CFA and also the neuropathic pain caused by PSNL.

Relevance of tumour necrosis factor-alpha for the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw

1. The present study evaluated the participation of tumour necrosis factor-alpha (TNF-alpha) in the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw. 2. The intraplantar injection of carrageenan (300 microg paw-1) induced a marked and biphasic paw oedema formation (peaks at 6 and 72 h), which was accompanied by a long-lasting mechanical allodynia (that remained elevated for up to 72 h) and a significant increase of myeloperoxidase (MPO) activity (peak at 6 h) in both Swiss and C57/BL6 mice. 3. The paw oedema, the elevation of MPO activity and to a lesser extent the mechanical allodynia elicited by carrageenan were found to be significantly reduced in TNF-alpha p55 receptor knockout mice. 4. Of interest, the systemic administration of an anti-TNF-alpha antibody produced a significant inhibition of paw oedema, mechanical allodynia and MPO activity. A noteworthy decrease in inflammatory and nociceptive responses caused by carrageenan was also observed when mice were previously treated with the preferential inhibitor of TNF-alpha synthesis, thalidomide. 5. The present results clearly indicate that the proinflammatory cytokine TNF-alpha plays a critical role in the oedema formation, as well as in the mechanical allodynia and the neutrophil migration, following carrageenan administration into the mouse paw. Intraplantar injection of carrageenan in mice could constitute a useful model for assessment of the in vivo effects of potential inhibitors of TNF-alpha-related pathways.

Long-lasting neuropathic pain induced by brachial plexus injury in mice: Role triggered by the pro-inflammatory cytokine, tumour necrosis factor α

Brachial plexus avulsion (BPA) resulted in a marked and long-lasting mechanical hypernociception (up to 80 days) in comparison to a sham-operated group, as assessed by Von Frey filaments, in both Swiss and C57/BL6 mice. In the tail-flick test, both Swiss and C57/BL6 mice submitted to BPA showed a significant thermal hypernociception, which persisted for 10 days. Both mechanical and thermal hypernociception following BPA were abolished in tumour necrosis factor alpha (TNFalpha) p55 receptor knockout mice. Moreover, the mechanical hypernociception caused by BPA was inhibited by the local application of the anti-TNFalpha (10 and 100 ng/site) antibody at the time of the surgery or by the intravenous administration (100 microg/kg) of this antibody at the time of the surgery or 4 days after the BPA. A similar inhibition of the mechanical hypernociception was observed when treating mice with the TNFalpha synthesis inhibitor thalidomide (50 mg/kg, s.c.), either at the time of the surgery or 4 days after. The results suggest that the persistent thermal, and especially the persistent mechanical, hypernociception observed following BPA in mice is largely dependent on the generation of TNFalpha. Based on these results, it is possible to suggest that therapeutic strategies for blocking TNFalpha could represent a valuable approach for the treatment of persistent neuropathic pain.

The effects of diacerhein on mechanical allodynia in inflammatory and neuropathic models of nociception in mice

In this study we analyzed the systemic antiallodynic properties of diacerhein, a drug used to treat osteoarthritis, in inflammatory and neuropathic models of nociception in mice. The effects of diacerhein were compared with those of gabapentin, a drug used clinically for the management of neuropathic pain. Similar to gabapentin, diacerhein was able to significantly reverse the mechanical allodynia induced by carrageenan. A significant inhibition of carrageenan-induced nociception was also observed when diacerhein was administered by the intrathecal but not by the intraplantar route. The treatment with diacerhein or with gabapentin also inhibited the mechanical allodynia induced by complete Freund's adjuvant (CFA) or after the partial ligation of the sciatic nerve (PLSN). In the same range of doses, diacerhein or gabapentin did not affect the locomotor activity, motor coordination, or body temperature of the animals. The present results indicate that diacerhein produces marked antiallodynic effects in carrageenan and CFA nociception models and also inhibits the neuropathic pain after PLSN, with an efficacy similar to that observed for gabapentin. Diacerhein may be a potentially interesting tool for the management of inflammatory and neuropathic pain.