Amifostine protects from the peripheral sensory neuropathy induced by oxaliplatin in mice.

Sensory neuropathy is a dose-limiting side effect of oxaliplatin-based cancer treatment. This study investigated the antinociceptive effect of amifostine and its potential neuroprotective mechanisms on the oxaliplatin-related peripheral sensory neuropathy in mice. Oxaliplatin (1 mg/kg) was injected intravenously in Swiss albino male mice twice a week (total of nine injections), while amifostine (1, 5, 25, 50, and 100 mg/kg) was administered subcutaneously 30 min before oxaliplatin. Mechanical and thermal nociceptive tests were performed once a week for 49 days. Additionally, c-Fos, nitrotyrosine, and activating transcription factor 3 (ATF3) immunoexpressions were assessed in the dorsal root ganglia. In all doses, amifostine prevented the development of mechanical hyperalgesia and thermal allodynia induced by oxaliplatin (P<0.05). Amifostine at the dose of 25 mg/kg provided the best protection (P<0.05). Moreover, amifostine protected against neuronal hyperactivation, nitrosative stress, and neuronal damage in the dorsal root ganglia, detected by the reduced expression of c-Fos, nitrotyrosine, and ATF3 (P<0.05 vs the oxaliplatin-treated group). In conclusion, amifostine reduced the nociception induced by oxaliplatin in mice, suggesting the possible use of amifostine for the management of oxaliplatin-induced peripheral sensory neuropathy.

Amifostine protects from the peripheral sensory neuropathy induced by oxaliplatin in mice

Sensory neuropathy is a dose-limiting side effect of oxaliplatin-based cancer treatment. This study investigated the antinociceptive effect of amifostine and its potential neuroprotective mechanisms on the oxaliplatin-related peripheral sensory neuropathy in mice. Oxaliplatin (1 mg/kg) was injected intravenously in Swiss albino male mice twice a week (total of nine injections), while amifostine (1, 5, 25, 50, and 100 mg/kg) was administered subcutaneously 30 min before oxaliplatin. Mechanical and thermal nociceptive tests were performed once a week for 49 days. Additionally, c-Fos, nitrotyrosine, and activating transcription factor 3 (ATF3) immunoexpressions were assessed in the dorsal root ganglia. In all doses, amifostine prevented the development of mechanical hyperalgesia and thermal allodynia induced by oxaliplatin (P<0.05). Amifostine at the dose of 25 mg/kg provided the best protection (P<0.05). Moreover, amifostine protected against neuronal hyperactivation, nitrosative stress, and neuronal damage in the dorsal root ganglia, detected by the reduced expression of c-Fos, nitrotyrosine, and ATF3 (P<0.05 vs the oxaliplatin-treated group). In conclusion, amifostine reduced the nociception induced by oxaliplatin in mice, suggesting the possible use of amifostine for the management of oxaliplatin-induced peripheral sensory neuropathy.

Antidepressant-like effect of nitric oxide synthase inhibitors and sildenafil against lipopolysaccharide-induced depressive-like behavior in mice.

Inflammation, oxidative and nitrosative stress underlie depression being assessed in rodents by the systemic administration of lipopolysacharide (LPS). There is an increasing body of evidence of an involvement of nitric oxide (NO) pathway in depression, but this issue was not investigated in LPS-induced model. Thus, herein we evaluated the effects of NO-pathway-modulating drugs, named aminoguanidine, l-NAME, sildenafil and l-arginine, on the behavioral (forced swimming test [FST], sucrose preference [SPT] and prepulse inhibition [PPI] of the startle) and neurochemical (glutathione [GSH], lipid peroxidation, IL-1ß) alterations in the prefrontal cortex, hippocampus and striatum as well as in BDNF levels in the hippocampus 24h after LPS (0.5mg/kg, i.p.) administration, a time-point related to depressive-like behavior. Twenty-four hours post LPS there was an increase in immobility time in the FST, decrease in sucrose preference and PPI levels accompanied by a decrease in GSH levels and an increase in lipid peroxidation, IL-1ß and hippocampal BDNF levels suggestive of a depressive-like state. The pretreatment with the NOS inhibitors, l-NAME and aminoguanidine as well as sildenafil prevented the behavioral and neurochemical alterations induced by LPS, although sildenafil and l-NAME were not able to prevent the increase in hippocampal BDNF levels induced by LPS. The iNOS inhibitor, aminoguanidine, and imipramine prevented all behavioral and neurochemical alterations induced by LPS. l-arginine did not prevent the alterations in immobility time, sucrose preference and GSH induced by LPS. Taken together our results show that the NO-cGMP pathway is important in the modulation of the depressive-like alterations induced by LPS.

Blockade of TRPA1 with HC-030031 attenuates visceral nociception by a mechanism independent of inflammatory resident cells, nitric oxide and the opioid system.

BACKGROUND: Some studies have shown a somatic nociceptive response due to the activation of transient receptor potential A1 channels (TRPA1), which is modulated by the TRPA1 antagonist HC-030031. However, a few studies report the role of TRPA1 in visceral pain. Therefore, we investigated the participation of TRPA1 in visceral nociception and the involvement of nitric oxide, the opioid system and resident cells in the modulation of these channels. METHODS: Mice were treated with vehicle or HC-030031 (18.75-300 mg/kg) before ifosfamide (400 mg/kg), 0.75% mustard oil (50 µL/colon), acetic acid 0.6% (10 mL/kg), zymosan (1 mg/cavity) or misoprostol (1 µg/cavity) injection. Visceral nociception was assessed through the electronic von Frey test or the writhing response. Ifosfamide-administered mice were euthanized for bladder analysis. The involvement of nitric oxide and the opioid system were investigated in mice injected with ifosfamide and mustard oil, respectively. The participation of resident peritoneal cells in acetic acid-, zymosan- or misoprostol-induced nociception was also evaluated. RESULTS: HC-030031 failed to protect animals against ifosfamide-induced bladder injury (p > 0.05). However, a marked antinociceptive effect against ifosfamide, mustard oil, acetic acid, zymosan and misoprostol was observed (p < 0.05). Neither L-arginine (600 mg/kg) nor naloxone (2 mg/kg) could reverse the antinociceptive effect of HC-030031. The reduction of the peritoneal cell population inhibited the acetic acid and zymosan-related writhes without interfering with the misoprostol effect. CONCLUSIONS: Our findings suggest that the blockade of TRPA1 attenuates visceral nociception by a mechanism independent of the modulation of resident cells, nitric oxide and opioid pathways.

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

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

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

Implantation of Walker 256 tumor decreases acute systemic inflammation in rats. Inflammatory hyperalgesia is one of the most important events of acute inflammation. The L-arginine/NO/cGMP/K(+)ATP pathway has been proposed as the mechanism of peripheral antinociception mediated by several drugs and physical exercise. The objective of this study was to investigate a possible involvement of the NO/cGMP/K(+)ATP pathway in antinociception induced in Walker 256 tumor-bearing male Wistar rats (180-220 g). The groups consisted of 5-6 animals. Mechanical inflammatory hypernociception was evaluated using an electronic version of the von Frey test. Walker tumor (4th and 7th day post-implantation) reduced prostaglandin E(2)- (PGE(2), 400 ng/paw; 50 µL; intraplantar injection) and carrageenan-induced hypernociception (500 µg/paw; 100 µL; intraplantar injection). Walker tumor-induced analgesia was reversed (99.3% for carrageenan and 77.2% for PGE(2)) by a selective inhibitor of nitric oxide synthase (L-NAME; 90 mg/kg, ip) and L-arginine (200 mg/kg, ip), which prevented (80% for carrageenan and 65% for PGE(2)) the effect of L-NAME. Treatment with the soluble guanylyl cyclase inhibitor ODQ (100% for carrageenan and 95% for PGE(2); 8 µg/paw) and the ATP-sensitive K(+) channel (KATP) blocker glibenclamide (87.5% for carrageenan and 100% for PGE(2); 160 µg/paw) reversed the antinociceptive effect of tumor bearing in a statistically significant manner (P < 0.05). The present study confirmed an intrinsic peripheral antinociceptive effect of Walker tumor bearing in rats. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP pathway followed by the opening of KATP channels.

Role of the haem oxygenase/carbon monoxide pathway in Clostridium difficile toxin A-induced enteritis in mice.

Clostridium difficile is the major cause of antibiotic-associated colitis, a disease with significant morbidity and mortality. This study investigated the role of the haem oxygenase-1 (HO-1)/carbon monoxide (CO) pathway in C. difficile toxin A-induced enteritis in mice. The HO substrate haemin, zinc protoporphyrin IX (ZnPP IX), a specific HO-1 inhibitor, dimanganese decacarbonyl (DMDC), a CO donor, or an equivalent volume of their respective vehicles were injected subcutaneously 30 min prior to local challenge with toxin A (25 or 50 µg per ileal loop) or PBS. Intestinal ileal loop weight/length ratios were calculated 3 h later. Ileal tissues were collected for histological analysis and measurement of myeloperoxidase (MPO) activity, tumour necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1ß) production by ELISA and immunohistochemistry for HO-1. Treatment of mice subjected to C. difficile toxin A (TcdA) with haemin or DMDC prevented oedema, mucosal disruption and neutrophil infiltration observed in histological analysis. It also decreased TcdA-induced MPO activity and TNF-α or IL-1ß production. In contrast, the specific HO-1 inhibitor (ZnPP IX) exacerbated all these evaluated parameters. TcdA increased HO-1 expression as seen by immunohistochemistry. These results suggest that the HO-1/CO pathway exerts a protective role in TcdA-induced enteritis and that its pharmacological modulation might be important for the management of C. difficile-associated disease.

Tumor bearing decreases systemic acute inflammation in rats--role of mast cell degranulation.

OBJECTIVE AND DESIGN: To investigate the effect of experimental tumor bearing on acute inflammation models in rats. METHODS: Four and 7 days after Walker tumor implantation in the right armpit, carrageenan or dextran- induced edema in the contralateral paw, carrageenan induced neutrophil migration into peritoneal cavities, cutaneous vascular permeability induced by bradykinin, histamine, serotonin, substance P, capsaicin or compound 48/80, and mesenteric mast cell degranulation induced by compound 48/80 were evaluated. The control group did not receive tumor implantation. Statistical analysis was performed using one way analysis of variance (ANOVA) followed by the Bonferroni test. RESULTS: On the 7(th) day after tumor inoculation, there were significant decreases in both carrageenan and dextran- induced paw edema. Tumor bearing did not change the neutrophil infiltration induced by carrageenan. There were decreases in cutaneous vascular permeability induced by compound 48/80, serotonin or bradykinin, but not that induced by histamine, substance P. A significant inhibition of mesenteric mast cell degranulation induced by compound 48/80 was observed, on the 4(th) and 7(th) days after tumor inoculation. CONCLUSION: Tumor bearing can limit mast cell function and vascular events in acute systemic inflammation in rats, without changes in neutrophil migration.

Lippia sidoides and Myracrodruon urundeuva gel prevents alveolar bone resorption in experimental periodontitis in rats.

In Brazilian folk medicine, Lippia sidoides (Ls) and Myracrodruon urundeuva (Mu) have gained popularity and reputation as effective antimicrobial and anti-inflammatory agents. This work aimed to evaluate the effect of topical herbal gel from Ls 0.5% (v/w) and Mu 5% (w/w) in experimental periodontal disease (EPD) in rats. Wistar rats were subjected to ligature placement around the second upper left molars. Animals were treated topically with Ls and/or Mu-based gel, immediately after EPD induction and three times/day for 11 days until the rats were sacrificed (11th day). Saline-based gel was utilized as control for all experiments and doxycycline based gel 10% (w/w) was utilized as reference substance. Animals were weighed daily. Alveolar bone loss was measured as the difference (in millimeters) between the cusp tip and the alveolar bone. The periodontum and the surrounding gingivae were examined at histopathology, as well as the neutrophil influx into the gingivae was assayed using myeloperoxidase activity and cytokine production mainly tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) levels by ELISA method. The local bacterial flora was assessed through culture of the gingival tissue in standard aerobic and anaerobic media. Alveolar bone loss was significantly inhibited by Ls and Mu combined treatment compared to the saline control group. Ls and Mu combined treatment reduced tissue lesion at histopathology, with partial preservation of the periodontum, coupled to decreased myeloperoxidase activity as well as significantly inhibited TNF-alpha and IL-1beta production in gingival tissue compared to the saline control group. Ls and Mu combined treatment also prevented the growth of oral microorganisms and the weight loss. Ls and Mu combined based gel treatment preserved alveolar bone resorption and demonstrated anti-inflammatory and antibacterial activities in experimental periodontitis.

Role of NO/cGMP/KATP pathway in antinociceptive effect of sildenafil in zymosan writhing response in mice.

OBJECTIVE: Previous studies have found that sildenafil produces antinociception in experimental models. This work was undertaken to determine the participation of the NO/cGMP/K(ATP) pathway in the antinociception induced by sildenafil. METHODS AND RESULTS: The antinociceptive effect of sildenafil was determined in the zymosan-induced writhing response in mice. Sildenafil (1-30 mg/kg; i. p.), given 30 min before zymosan (1 mg/animal; i. p.), inhibited the writhing response (5.0 +/- 1.3 versus 26.6 +/- 2.7; p < 0.001) in a dose-dependent manner. L-NAME (30 mg/kg; s. c.) significantly (p < 0.05) reversed this effect (16.6 +/- 3.1 versus 6.4 +/- 1.6) and L-arginine (200 mg/kg; i. p.) prevented the L-NAME effect (6.8 +/- 0.8 versus 16.6 +/- 3.1; p < 0.05). ODQ (0,3-1 mg/kg; i. p.) and glybenclamide (0.3-1 mg/kg; p. o.) pre-treatment significantly (p < 0.01) inhibited the antinociceptive effect of sildenafil (18.0 +/- 1.7 versus 2.1 +/- 1.0 and 5.5 +/- 0.7 versus 1.6+0.7, respectively). Diazoxide (10 mg/kg; s. c) significantly (p < 0.001) abolished the glybenclamide effect (1.6 +/- 0.8 versus 14 +/- 1.2). CONCLUSIONS: The data indicate that the antinociceptive effect of sildenafil is dependent on the activation of the NO/cGMP/ K(ATP) pathway.

Role of nitric oxide on pathogenesis of 5-fluorouracil induced experimental oral mucositis in hamster.

INTRODUCTION: Mucositis induced by antineoplastic drugs is an important, dose-limiting, and costly side effect of cancer therapy. AIM: To investigate the role of nitric oxide (NO) on the pathogenesis of 5-fluorouracil (5-FU)-induced oral mucositis. MATERIALS AND METHODS: Oral mucositis was induced by two intraperitoneal (i.p) administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) in male hamsters. Animals were treated subcutaneously with saline (0.4 ml), 1,400 W (1 mg/kg), aminoguanidine (5 or 10 mg/kg) or Nphi-Nitro-L-Arginine Methyl Ester (L-NAME) (5, 10, or 20 mg/kg) 1 h before the injections of 5-FU and daily until sacrifice, on the tenth day. Macroscopic and histopathological analyses were evaluated and graded. Tissues from the cheek pouches were harvested for measurement of myeloperoxidase (MPO) activity, nitrite level, and immunohistochemistry for induced nitric oxide synthase (iNOS). RESULTS: Treatment with 1,400 W or aminoguanidine reduced macroscopic and histological parameters of oral mucositis, and reduced the inflammatory cell infiltration as detected by histopathology and by MPO activity. In contrast, the administration of L-NAME did not significantly reverse the inflammatory alterations induced by experimental mucositis. Increased NOS activity, nitrite level and immunostaining for iNOS were detected on the check pouch tissue of animals submitted to 5-FU-induced oral mucositis on the tenth day. CONCLUSION: These results suggest an important role of NO produced by iNOS in the pathogenesis of oral mucositis induced by 5-FU.

Dual effect of cAMP on the writhing response in mice.

The intraperitoneal injection of agents that increase the intracellular level of cyclic AMP (cAMP), reduced significantly the number of writhes induced by acetic acid and zymosan in mice. However, dibutyryl cyclic AMP (Db-cAMP) induced a dual response: (a) low doses caused antinociception, and (b) a high dose potentiated the nociceptive effect of a low concentration of acetic acid. High doses of Db-cAMP also reversed the antinociceptive effect of dexamethasone and the depletion of resident peritoneal cells. We also demonstrated that a low dose of Db-cAMP, forskolin or dexamethasone inhibited the production of tumor necrosis factor-alpha and interleukin-1 beta by macrophages stimulated by zymosan. In conclusion, this study suggests that cAMP has a dual effect in the writhing model: an antinociceptive effect due to its modulatory action on resident peritoneal cells, thus, reducing the synthesis of mediators involved in the nociceptive response, and a nociceptive effect by directly sensitizing the nociceptive neuron.

Analgesic effect of thalidomide on inflammatory pain.

Tumor necrosis factor alpha (TNF-alpha) may have a pivotal role in the genesis of mechanical inflammatory hyperalgesia in rats and in the nociceptive writhing response in mice. Thalidomide has been shown to selectively inhibit TNF-alpha production. We therefore investigated the effect of thalidomide on these responses as well as on the hot plate response in mice. Hyperalgesic responses to intraplantar (i.pl.) injections of carrageenin or bradykinin, which act by stimulating TNF-alpha release, but not responses to TNF-alpha or prostaglandin E(2), were inhibited in a dose-dependent manner by pretreatment of the animals with thalidomide. The nociceptive writhing responses induced by intraperitoneal (i.p.) injections of zymosan or acetic acid were also inhibited in a dose-dependent manner by pretreatment of mice with thalidomide. Moreover, the thalidomide pretreatment also reduced the TNF-alpha mRNA levels in the peritoneal cells induced by injection of zymosan in mice. The analgesic effect of thalidomide is not due to a central effect, since the drug had no effect in the hot plate test. The demonstration that thalidomide is able to inhibit inflammatory hyperalgesia in rats and the writhing nociceptive response in mice suggests that these analgesic effects seem to be a consequence of the inhibition of TNF-alpha production, and indicates the need for investigations on the possibility of the use of thalidomide for the treatment of pain refractory to classical non-narcotic analgesics.

Involvement of resident macrophages and mast cells in the writhing nociceptive response induced by zymosan and acetic acid in mice.

Intraperitoneal administration of zymosan and acetic acid induced a dose-dependent nociceptive writhing response in mice. Lavage of the peritoneal cavities with saline reduced the number of total resident peritoneal cells and caused a proportional decrease in the nociceptive responses induced by these stimuli. Furthermore, the specific reduction of the peritoneal mast cell population by intraperitoneal administration of compound 48/80 also reduced the nociceptive responses induced by zymosan and acetic acid. In contrast, enhancement of the peritoneal macrophage population by pretreatment of the cavities with thioglycollate caused an increase in the number of writhes induced by both stimuli. These data suggest that the nociceptive responses induced by zymosan and acetic acid are dependent upon the peritoneal resident macrophages and mast cells. These cells modulate the nociceptive response induced by zymosan and acetic acid via release of tumour necrosis factor alpha (TNF-alpha), interleukin 1beta and interleukin 8. This suggestion is supported by the following observations: (a) pretreatment of the peritoneal cavities with antisera against these cytokines reduced the nociceptive responses induced by these stimuli; (b) peritoneal cells harvested from cavities injected with zymosan or acetic acid released both interleukin 1beta and TNF-alpha; (c) although individual injection of TNF-alpha, interleukin 1beta or interleukin 8 did not induce the nociceptive effect, intraperitoneal injection of a mixture of these three recombinant cytokines caused a significant nociceptive writhing response. In conclusion, our results suggest that the nociceptive activity of zymosan and acetic acid in the writhing model is due to the release of TNF-alpha, interleukin 1beta and interleukin 8 by resident peritoneal macrophages and mast cells.