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.

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.

Correction to: The kinin B1 and B2 receptors and TNFR1/p55 axis on neuropathic pain in the mouse brachial plexus.

Unfortunately, the Fig. 7 was wrongly downloaded in the original publication.

The kinin B1 and B2 receptors and TNFR1/p55 axis on neuropathic pain in the mouse brachial plexus.

Tumour necrosis factor (TNF) and kinins have been associated with neuropathic pain-like behaviour in numerous animal models. However, the way that they interact to cause neuron sensitisation remains unclear. This study assessed the interaction of kinin receptors and TNF receptor TNFR1/p55 in mechanical hypersensitivity induced by an intraneural (i.n.) injection of rm-TNF into the lower trunk of brachial plexus in mice. The i.n. injection of rm-TNF reduced the mechanical withdrawal threshold of the right forepaw from the 3rd to the 10th day after the injection, indicating that TNF1/p55 displays a critical role in the onset of TNF-elicited neuropathic pain. The connection between TNF1/p55 and kinin B1 and B2 receptors (B1R and B2R) was confirmed using both knockout mice and mRNAs quantification in the injected nerve, DRG and spinal cord. The treatment with the B2R antagonist HOE 140 or with B1R antagonist des-Arg9-Leu8-BK reduced both BK- and DABK-induced hypersensitivity. The experiments using kinin receptor antagonists and CPM inhibitor (thiorphan) suggest that BK does not only activate B2R as an orthosteric agonist, but also seems to be converted into DABK that consequently activates B1R. These results indicate a connection between TNF and the kinin system, suggesting a relevant role for B1R and B2R in the process of sensitisation of the central nervous systems by the cross talk between the receptor and CPM after i.n. injection of rm-TNF.

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.

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.

Synthetic chalcones as potential tool for acute- and chronic-pain control.

The purpose of this study was to validate the potential anti-hypersensitive activity of two chalcones, (2E)-1-(4-aminophenyl)-3-(4-nitrophenyl)prop-2-en-1-one (ANCh) and N-{4-[(2E)-3-(4-nitrophenyl)prop-2-enoil]phenyl}acetamide (AcANCh), by different models of acute and persistent pain in mice, besides in silico analysis. Molecules computational investigation for prediction of Lipinki's and Veber's rules to determine solubility, % absorption, drug likeness and toxicity liabilities was performed. Male and female C57BL/6 mice (20-30 g, n = 6) were used. Firstly, mice were pre-treated with the compounds ANCh or AcANCh and then submitted to the models of acute hypersensitivity by the intraplantar injection of different phlogistic agents. The mechanical sensitivity was assessed using von Frey hairs (0.6 g). The obtained data shows that both compounds presented important inhibitory effects on mechanical hypersensitivity induced by carrageenan (with oral bioavailability). The anti-hypersensitive effect was also accompanied by the interference in leukocyte migration, interleukin-1ß (IL-1ß) and tumour necrosis factor (TNF) levels reduction and by the absence of unspecific effects. Added to the in vivo results, the in silico analysis presented none violation in Lipinski's or Veber's rules, good probability to cell membrane permeability and oral bioavailability, positive values of drug likeness and few risk of computational toxicity. ANCh partially reduced the hypersensitivity induced by IL-1ß and TNF, epinephrine and prostaglandin E2 (PGE2). AcANCh had similar effect, except for the absent of inhibition in PGE2-injected mice. Both compounds were capable of reducing the mechanical hypersensitivity presented in all persistent models of hypersensitivity (inflammatory pain, chronic nerve constriction and cancer pain), with emphasis for ANCh. These results suggest that both chalcones could represent good strategies for the control of acute and chronic pain, without important side effects. ANCh seems to involve cell migration and cytokines production as the main mechanism, together with interference in PGE2 neuronal sensitization pathway. In vivo and in silico analyses reinforce the potential characteristics of the compounds to become future drugs.

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.

Aleurites moluccana and its main active ingredient, the flavonoid 2″-O-rhamnosylswertisin, have promising antinociceptive effects in experimental models of hypersensitivity in mice.

This study investigated the antinociceptive effect of Aleurites moluccana dried extract (DE; 125 to 500 mg/kg, p.o.) and the isolated flavonoid 2″-O-rhamnosylswertisin (5 to 50.6 µmol/kg, p.o.) using different models of long-lasting inflammatory and neuropathic pain in mice. Attempts were made to analyse the mechanisms through which A. moluccana exerted its effects. A. moluccana DE inhibited complete Freund's adjuvant (CFA)-induced mechanical nociception. It was also evidenced by a reduction of sensitization in the contralateral hindpaw. The extract reversed the mechanical hypersensitivity of partial ligation of sciatic nerve (PLSN)-treated animals, similar to gabapentin. In PLSN model, the opioid, dopaminergic and oxidonitrergic pathways were involved in the A. moluccana DE antinociceptive effects. A single dose of 2″-O-rhamnosylswertisin inhibited the carrageenan- and CFA-induced mechanical nociception. Furthermore, the compound caused expressive antinociception in PLSN-mice, with inhibition value greater than obtained with gabapentin. Oral treatment with the extract or the isolated compound attenuated the neutrophil migration and IL-1ß levels following carrageenan injection. Of note, A. moluccana DE did not interfere with thermal sensitivity in healthy mice. The absence of side effects, including interference in locomotor activity, motor performance in animals treated with the extract, showed excellent potential for the therapeutic use of this medicinal plant in treating persistent pain in humans.

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 CB(1) and CB(2) 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 CB(1) and CB(2) 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.

Aleurites moluccana (L.) Willd. Leaves: Mechanical Antinociceptive Properties of a Standardized Dried Extract and Its Chemical Markers.

Seeking to develop a new analgesic phytomedicine, a spray-dried extract (SDE) of Aleurites moluccana (L.) Willd. leaves was developed in scale up (5 kg). The SDE was standardized at 3% w/w in relation to the flavonoid 2''-O-rhamnosylswertisin. The SDE batches were evaluated in relation to their physical, physiochemical, and pharmacological characteristics. The results demonstrated the reproducibility of the scale up SDE process which, when dosed orally, reduced carrageenan-induced mechanical hypernociception, with an ID(50)% of 443 mg/kg. Similar results were obtained with animals injected with complete Freund's adjuvant (CFA), in which SDE caused inhibition of 48 ± 4%. SDE was effective in preventing prostaglandin E2 (PGE2)-induced mechanical hypernociception (inhibition of 26 ± 10% and 33 ± 3%, at 250 and 500 mg/kg, respectively). Swertisin and 2''-O-rhamnosylswertisin isolated from the own extract were effective in inhibiting the hypernociceptive response induced by carrageenan (70 ± 2% and 50 ± 5%, resp.). Furthermore, 2''-O-rhamnosylswertisin was capable of significantly inhibiting the mechanical sensitization induced by CFA or PGE2, with inhibitions of 25 ± 3% and 94 ± 6%, respectively. These results suggest that the effects of SDE are related, at least in part, to the presence of these flavonoids.

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.

The effects of the selective and non-peptide CXCR2 receptor antagonist SB225002 on acute and long-lasting models of nociception in mice.

This study evaluated the antinociceptive effects of the selective and non-peptide CXCR2 antagonist SB225002 in mouse models of pain. As assessed in different tests of spontaneous nociception, intraperitoneal (i.p.) administration of SB225002 caused consistent and dose-related reduction of acetic acid-induced abdominal constrictions, whereas it did not significantly affect the nociception evoked by formalin, capsaicin, glutamate or phorbol ester acetate (PMA). Systemic treatment with SB225002 strikingly reduced the spontaneous nociception induced by 8-bromo-cAMP (8-Br-cAMP), or mechanical hypernociception induced by prostaglandin E(2) (PGE(2)), epinephrine, or the keratinocyte-derived chemokine (KC). In the carrageenan model, SB225002 markedly reduced mechanical hypernociception when administered by i.p., intrathecal (i.t.) or intracerebroventricular (i.c.v.) routes, or even when co-administered with carrageenan into the mouse paw, indicating peripheral and central sites of action for SB225002. In addition, i.p. treatment with SB225002 significantly attenuated the increase in MPO activity or the elevation of IL-1beta, TNFalpha or KC levels following carrageenan injection. In the persistent models of pain evoked by complete Freund's adjuvant (CFA) or by the partial ligation of the sciatic nerve (PLSN), the repeated administration of SB225002 displayed prominent and long-lasting antinociceptive effects. Notably, SB225002 did not evoke unspecific central effects, as evaluated in the open-field and rota-rod tests, or even in the latency responses for thermal stimuli. Our data confirm the previous notion on the critical role exerted by chemokines in pain, indicating that selective CXCR2 antagonists, such as SB225002, might well represent interesting and innovative alternatives for the management of both acute and chronic pain.

Mechanisms underlying the nociceptive responses induced by platelet-activating factor (PAF) in the rat paw.

Platelet-activating factor (PAF) is an inflammatory mediator widely known to exert relevant pathophysiological functions. However, the relevance of PAF in nociception has received much less attention. Herein, we have investigated the mechanisms underlying PAF-induced spontaneous nociception and mechanical hypersensitivity in the rat paw. PAF injection (1- 30 nmol/paw) resulted in a dose-related overt nociception, whilst only the dose of 10 nmol/ paw produced a significant and time-related mechanical hypersensitivity. Local coinjection of PAF antagonist WEB2086 significantly inhibited both spontaneous nociception and mechanical hypersensitivity. Moreover, the coinjection of the natural IL-1beta receptor antagonist (IRA) notably prevented both PAF-induced nociceptive responses, whilst these responses were not altered by anti-TNFalpha coinjection. Interestingly, pretreatment with the ultrapotent vaniloid agonist resiniferotoxin, coinjection of the TRPV1 receptor antagonist SB366791, or mast cell depletion with compound 48/80 markedly prevented PAF-induced spontaneous nociception. Conversely, PAF-elicited mechanical hypersensitivity was strikingly susceptible to distinct antineutrophil-related strategies, namely the antineutrophil antibody, the selectin blocker fucoidin, the chemokine CXCR2 receptor antagonist SB225002, and the C5a receptor antibody anti-CD88. Notably, the same antineutrophil migration strategies significantly prevented the increase of myeloperoxidase activity induced by PAF. The mechanical hypersensitivity caused by PAF was also prevented by the cyclooxygenase inhibitors indomethacin or celecoxib, and by the selective beta(1) adrenergic receptor antagonist atenolol. Collectively, the present results provide consistent evidence indicating that distinct mechanisms are involved in the spontaneous nociception and mechanical hypersensitivity caused by PAF. They also support the concept that selective PAF receptor antagonists might constitute interesting targets for the development of new analgesic drugs.

Neuropathic pain-like behavior after brachial plexus avulsion in mice: the relevance of kinin B1 and B2 receptors.

The relevance of kinin B(1) (B(1)R) and B(2) (B(2)R) receptors in the brachial plexus avulsion (BPA) model was evaluated in mice, by means of genetic and pharmacological tools. BPA-induced hypernociception was absent in B(1)R, but not in B(2)R, knock-out mice. Local or intraperitoneal administration of the B(2)R antagonist Hoe 140 failed to affect BPA-induced mechanical hypernociception. Interestingly, local or intraperitoneal treatment with B(1)R antagonists, R-715 or SSR240612, dosed at the time of surgery, significantly reduced BPA-evoked mechanical hypernociception. Intrathecal or intracerebroventricular administration of these antagonists, at the surgery moment, did not prevent the hypernociception. Both antagonists, dosed by intraperitoneal or intrathecal routes (but not intracerebroventricularly) 4 d after the surgery, significantly inhibited the mechanical hypernociception. At 30 d after the BPA, only the intracerebroventricular treatment effectively reduced the hypernociception. A marked increase in B(1)R mRNA was observed in the hypothalamus, hippocampus, thalamus, and cortex at 4 d after BPA and only in the hypothalamus and cortex at 30 d. In the spinal cord, a slight increase in B(1)R mRNA expression was observed as early as at 2 d. Finally, an enhancement of B(1)R protein expression was found in all the analyzed brain structures at 4 and 30 d after the BPA, whereas in the spinal cord, this parameter was augmented only at 4 d. The data provide new evidence on the role of peripheral and central kinin B(1)R in the BPA model of neuropathic pain. Selective B(1)R antagonists might well represent valuable tools for the management of neuropathic 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.