Cássia Regina Silva

Anxiolytic-like effect of lavender essential oil inhalation in mice: participation of serotonergic but not GABAA/benzodiazepine neurotransmission.

ETHNOPHARMACOLOGICAL RELEVANCE Lavandula angustifolia (lavender) inhalation has been used in folk medicine for the treatment of anxiety, and clinical and animal studies have corroborated its anxiolytic effect, although its mechanism of action is still not fully understood. AIMS OF THE STUDY The objective of the present study was to determine whether the GABAA/benzodiazepine complex or serotonin neurotransmission mediates the anxiolytic-like effect of lavender essential oil. MATERIALS AND METHODS Male Swiss mice were subjected to the marble-burying test after being exposed to the aroma of lavender essential oil (1-5%), amyl acetate (5%; used as a behaviorally neutral odor), or distilled water for 15 min via inhalation. Additionally, the effect of 5% lavender essential oil was also evaluated in mice subjected to the elevated plus maze. GABAA/benzodiazepine mediation was evaluated by pretreating the mice with the GABAA receptor antagonist picrotoxin before the marble burying test and [(3)H]flunitrazepam binding to the benzodiazepine site on the GABAA receptor. Serotonergic mediation was studied by pretreating the mice with O-methyl-[3H]-N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride (WAY100635), a serotonin 5-HT1A receptor antagonist before the marble burying test. We also evaluated changes in the pharmacologically induced serotonin syndrome and the effects of combined administration of subeffective doses of lavender essential oil and the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). RESULTS Lavender essential oil (1-5%) decreased the number of marbles buried compared with the control and amyl acetate groups. In the elevated plus maze, 5% lavender essential oil inhalation increased the percentage of time spent on and number of entries into the open arms compared with controls. No effect was seen in the number of closed arm entries or number of beam interruptions in the automated activity chamber. Pretreatment with the GABAA receptor antagonist picrotoxin (0.5mg/kg) did not modify the behavioral effect of 5% lavender essential oil in the marble-burying test. Lavender essential oil also did not alter [(3)H]flunitrazepam binding to the benzodiazepine site on the GABAA receptor. Pretreatment with the serotonin 5-HT1A receptor antagonist WAY100635 (3mg/kg) blocked the anxiolytic-like effect of lavender essential oil and the 5-HT1A receptor agonist 8-OH-DPAT (3mg/kg). A combination of ineffective doses of 8-OH-DPAT (0.5mg/kg) and lavender essential oil (0.1%) reduced the number of marbles buried. Finally, 5% lavender essential oil attenuated the serotonin syndrome induced by 40 mg/kg fluoxetine plus 80 mg/kg 5-hydroxytryptophan. CONCLUSIONS These results indicate an important role for the serotonergic system in the anxiolytic-like effect of lavender essential oil.

Involvement of mast cells in a mouse model of postoperative pain.

Recent studies have indicated that nearly half of all surgical patients still have inadequate pain relief; therefore, it is becoming increasingly more important to understand the mechanisms involved in postoperative pain in order to be better treated. Previous studies have shown that incisions can cause mast cell degranulation. Thus, the aim of this study was to investigate the involvement of mast cells in a model of postoperative pain in mice. The depletion of mast cell mediators produced by pre-treatment with compound 48/80 (intraplantar (i.pl.)) widely (98 ± 23% of inhibition) and extensively (up to 96 h) prevented postoperative nociception and reduced histamine and serotonin levels (88 ± 4% and 68 ± 10%, respectively) in operated tissue. Furthermore, plantar surgery produced immense mast cell degranulation, as assessed by histology and confirmed by the increased levels of serotonin (three-fold higher) and histamine (fifteen-fold higher) in the perfused tissue, 1h after surgery. Accordingly, pre-treatment with the mast cell membrane stabilizer cromoglycate (200 μg/paw, i.pl.) prevented mechanical allodynia (inhibition of 96 ± 21%) and an increase in histamine (44 ± 10% of inhibition) and serotonin (73 ± 5% of inhibition) levels induced by plantar surgery. Finally, local treatment with H(1) (promethazine, 100 μg/paw, i.pl.), 5-HT(3) (ondansetron, 10 μg/paw, i.pl.) or 5-HT(2A) (ketanserin, 5 μg/paw, i.pl.) receptor antagonists partially decreased postoperative nociception in mice, but when co-administered together it completely reversed the mechanical allodynia in operated mice. Thus, mast cell activation mechanisms are interesting targets for the development of novel therapies to treat postoperative pain.

TRPA1 receptor stimulation by hydrogen peroxide is critical to trigger hyperalgesia and inflammation in a model of acute gout.

Acute gout attacks produce severe joint pain and inflammation associated with monosodium urate (MSU) crystals leading to oxidative stress production. The transient potential receptor ankyrin 1 (TRPA1) is expressed by a subpopulation of peptidergic nociceptors and, via its activation by endogenous reactive oxygen species, including hydrogen peroxide (H2O2), contributes to pain and neurogenic inflammation. The aim of this study was to investigate the role of TRPA1 in hyperalgesia and inflammation in a model of acute gout attack in rodents. Inflammatory parameters and mechanical hyperalgesia were measured in male Wistar rats and in wild-type (Trpa1(+/+)) or TRPA1-deficient (Trpa1(-/-)) male mice. Animals received intra-articular (ia, ankle) injection of MSU. The role of TRPA1 was assessed by receptor antagonism, gene deletion or expression, sensory fiber defunctionalization, and calcitonin gene-related peptide (CGRP) release. We found that nociceptor defunctionalization, TRPA1 antagonist treatment (via ia or oral administration), and Trpa1 gene ablation abated hyperalgesia and inflammatory responses (edema, H2O2 generation, interleukin-1β release, and neutrophil infiltration) induced by ia MSU injection. In addition, we showed that MSU evoked generation of H2O2 in synovial tissue, which stimulated TRPA1 producing CGRP release and plasma protein extravasation. The MSU-elicited responses were also reduced by the H2O2-detoxifying enzyme catalase and the reducing agent dithiothreitol. TRPA1 activation by MSU challenge-generated H2O2 mediates the entire inflammatory response in an acute gout attack rodent model, thus strengthening the role of the TRPA1 receptor and H2O2 production as potential targets for treatment of acute gout attacks.

Antinociceptive effect of Brazilian armed spider venom toxin Tx3-3 in animal models of neuropathic pain.

&NA; Venoms peptides have produced exceptional sources for drug development to treat pain. In this study we examined the antinociceptive and side effects of Tx3–3, a peptide toxin isolated from Phoneutria nigriventer venom, which inhibits high‐voltage‐dependent calcium channels (VDCC), preferentially P/Q and R‐type VDCC. We tested the effects of Tx3–3 in animal models of nociceptive (tail‐flick test), neuropathic (partial sciatic nerve ligation and streptozotocin‐induced diabetic neuropathy), and inflammatory (intraplantar complete Freunds adjuvant) pain. In the tail‐flick test, both intrathecal (i.t.) and intracerebroventricular (i.c.v.) injection of Tx3–3 in mice caused a short‐lasting effect (ED50 and 95% confidence intervals of 8.8 [4.1–18.8] and 3.7 [1.6–8.4] pmol/site for i.t. and i.c.v. injection, respectively), without impairing motor functions, at least at doses 10–30 times higher than the effective dose. By comparison, &ohgr;‐conotoxin MVIIC, a P/Q and N‐type VDCC blocker derived from Conus magus venom, caused significant motor impairment at doses close to efficacious dose in tail flick test. Tx3–3 showed a long‐lasting antinociceptive effect in neuropathic pain models. Intrathecal injection of Tx3–3 (30 pmol/site) decreased both mechanical allodynia produced by sciatic nerve injury in mice and streptozotocin‐induced allodynia in mice and rats. On the other hand, i.t. injection of Tx3–3 did not alter inflammatory pain. Taken together, our data show that Tx3–3 shows prevalent antinociceptive effects in the neuropathic pain models and does not cause adverse motor effects at antinociceptive efficacious doses, suggesting that this peptide toxin holds promise as a novel therapeutic agent for the control of neuropathic pain. The Brazilian armed spider Tx3–3, a new P/Q and R‐type calcium channel blocker, effectively alleviates allodynia in animal neuropathic pain models.

Anthocyanins restore behavioral and biochemical changes caused by streptozotocin-induced sporadic dementia of Alzheimer's type.

AIMS The aim of this study was to analyze if the pre-administration of anthocyanin on memory and anxiety prevented the effects caused by intracerebroventricular streptozotocin (icv-STZ) administration-induced sporadic dementia of Alzheimers type (SDAT) in rats. Moreover, we evaluated whether the levels of nitrite/nitrate (NOx), Na(+),K(+)-ATPase, Ca(2+)-ATPase and acethylcholinesterase (AChE) activities in the cerebral cortex (CC) and hippocampus (HC) are altered in this experimental SDAT. MAIN METHODS Male Wistar rats were divided in 4 different groups: control (CTRL), anthocyanin (ANT), streptozotocin (STZ) and streptozotocin+anthocyanin (STZ+ANT). After seven days of treatment with ANT (200mg/kg; oral), the rats were icv-STZ injected (3mg/kg), and four days later the behavior parameters were performed and the animals submitted to euthanasia. KEY FINDINGS A memory deficit was found in the STZ group, but ANT treatment showed that it prevents this impairment of memory (P<0.05). Our results showed a higher anxiety in the icv-STZ group, but treatment with ANT showed a per se effect and prevented the anxiogenic behavior induced by STZ. Our results reveal that the ANT treatment (100μM) tested displaces the specific binding of [(3)H] flunitrazepam to the benzodiazepinic site of GABAA receptors. AChE, Ca(+)-ATPase activities and NOx levels were found to be increased in HC and CC in the STZ group, which was attenuated by ANT (P<0.05). STZ decreased Na(+),K(+)-ATPase activity and ANT was able to prevent these effects (P<0.05). SIGNIFICANCE In conclusion, these findings demonstrated that ANT is able to regulate ion pump activity and cholinergic neurotransmission, as well as being able to enhance memory and act as an anxiolytic compound in animals with SDAT.

The involvement of TRPA1 channel activation in the inflammatory response evoked by topical application of cinnamaldehyde to mice

AIMS In the present work, we characterize the inflammatory process induced by the topical application of cinnamaldehyde on the skin of mice and verify the participation of transient receptor potential A1 TRPA1 receptors in this process. MAIN METHODS We measured mouse ear edema and sensitization/desensitization after topical application of cinnamaldehyde or/and capsaicin. We also quantified cellular infiltration through myeloperoxidase (MPO) activity and histological and immunohistochemical analyses and evaluated the expression of TRPV1 and TRPA1 by western blot. KEY FINDINGS Cinnamaldehyde induced ear edema in mice (1-6μg/ear) with a maximum effect of 4μg/ear. Cinnamaldehyde promoted leukocyte infiltration as detected by increasing MPO activity and confirmed by histological analyses. The edema and cellular infiltration evoked by the application of 4μg/ear of cinnamaldehyde were prevented by topical application of ruthenium red, a non-selective TRP antagonist as well as camphor and HC030031, two TRPA1 receptor antagonists. Cinnamaldehyde-induced edema, but not cellular infiltration, was prevented by topical application of the tachykinin NK1 antagonist, aprepitant, indicating a neuropeptide release phenomenon in this process. Additionally, we observed that repeated topical applications of cinnamaldehyde did not induce changes in sensitization or desensitization with respect to the edema response. Interestingly, repeated treatment with the TRPV1 agonist, capsaicin, abrogated it edematogenic response, confirming the desensitization process and partially decreasing the cinnamaldehyde-induced edema, suggesting the involvement of capsaicin-sensitive fibers. SIGNIFICANCE Our data demonstrate that the topical application of cinnamaldehyde produces an inflammatory response that is dependent on TRPA1 receptor stimulation.

Antinociceptive effect of 3-(4-fluorophenyl)-5-trifluoromethyl-1H-1-tosylpyrazole. A Celecoxib structural analog in models of pathological pain

Pain is the most common complaint in the medical field and the identification of novel compounds that can effectively treat painful states without causing side effects remains a major challenge in biomedical research. The aim of the present study is to investigate the antinociceptive effect of 3-(4-fluorophenyl)-5-trifluoromethyl-1H-1-tosylpyrazole (FTosPz) in models of pathological pain in mice and compare these effects with those produced by Celecoxib. FTosPz (100-500 μmol/kg) or Celecoxib (26-260 μmol/kg) was administrated orally. The administration of either FTosPz or Celecoxib reduced the hyperalgesia but not the edema or leukocyte infiltration that was caused by Complete Freunds Adjuvant (CFA), used as an arthritis model. Oral administration of both FTosPz and Celecoxib also attenuated the postoperative hyperalgesia as well as the hyperalgesia caused by partial sciatic nerve ligation, used as a neuropathic pain model. FTosPz and Celecoxib produced antinociceptive effects without altering the locomotor activity of animals. Furthermore, FTosPz neither altered AST/ALT enzyme activity nor the urea/creatinine levels. Still, the FTosPz did not alter the COX-1 and COX-2 enzyme activities. Thus, FTosPz is an interesting prototype for the development of novel analgesic drugs.

Nanoencapsulation of rice bran oil increases its protective effects against UVB radiation-induced skin injury in mice.

Excessive UV-B radiation by sunlight produces inflammatory and oxidative damage of skin, which can lead to sunburn, photoaging, and cancer. This study evaluated whether nanoencapsulation improves the protective effects of rice bran oil against UVB radiation-induced skin damage in mice. Lipid-core nanocapsules containing rice bran oil were prepared, and had mean size around 200 nm, negative zeta potential (∼-9 mV), and low polydispersity index (<0.20). In order to allow application on the skin, a hydrogel containing the nanoencapsulated rice bran oil was prepared. This formulation was able to prevent ear edema induced by UVB irradiation by 60 ± 9%, when compared with a hydrogel containing LNC prepared with a mixture of medium chain triglycerides instead of rice bran oil. Protein carbonylation levels (biomarker of oxidative stress) and NF-κB nuclear translocation (biomarker of pro-inflammatory and carcinogenesis response) were reduced (81% and 87%, respectively) in animals treated with the hydrogel containing the nanoencapsulated rice bran oil. These in vivo results demonstrate the beneficial effects of nanoencapsulation to improve the protective properties of rice bran oil on skin damage caused by UVB exposure.

Critical role of protease-activated receptor 2 activation by mast cell tryptase in the development of postoperative pain.

Background:Studies have indicated that nearly half of all surgical patients still have inadequate pain relief. Thus, it is crucial to understand the mechanisms involved in postoperative pain in order to better treat it. Thus, the aim of this study was to investigate the involvement of mast cell degranulation, tryptase and its substrate, the protease-activated receptor 2, in a model of postoperative pain in mice. Methods:We evaluated the effect of the compound 48/80 (to cause mast cell mediator depletion), cromoglycate or ketotifen (mast cell stabilizers), gabexate (tryptase inhibitor) or N3-methylbutyryl-N-6-aminohexanoyl-piperazine (protease-activated receptor 2 antagonist) in a postoperative pain model in mice (n = 5–10). Mast cell degranulation and tryptase activity were also evaluated in the operated tissue (n= 5–8). Results:The pre-treatment with compound 48/80 or ketotifen was able to prevent nociception throughout the postoperative hyperalgesia course (until 5 days after surgery), whereas cromoglycate presented a shorter effect (until 1 day). Gabexate or N3-methylbutyryl-N-6-aminohexanoyl-piperazine also produced a short-lasting effect in preventing postoperative nociception. However, neither gabexate, N3-methylbutyryl-N-6-aminohexanoyl-piperazine nor cromoglycate was capable of reversing nociception when administered after incision. Surgery led to early mast cell degranulation on the incised tissue and increased tryptase activity in tissue perfusates. Cromoglycate fully prevented the tryptase release in the perfusate and the compound 48/80 substantially reduced tryptase activity in the incised tissue. Conclusion:Thus, the mast cell degranulation with the subsequent release of tryptase and protease-activated receptor 2 activation are potential targets for the development of novel therapies to prevent, but not reverse, postoperative pain.

Anti-inflammatory and antioxidant effects of Aloe saponaria Haw in a model of UVB-induced paw sunburn in rats.

Ultraviolet B (UVB) irradiation mainly affects biological tissues by inducing an increase in reactive oxygen species (ROS) production which leads to deleterious outcomes for the skin, including pain and inflammation. As a protective strategy, many studies have focused on the use of natural products. The aim of this study was to investigate the effects of Aloe saponaria on nociceptive, inflammatory, and oxidative parameters in a model of UVB-induced sunburn in adult male Wistar rats. Sunburned animals were topically treated with vehicle (base cream), 1% silver sulfadiazine (positive control) or A. saponaria (10%) once a day for 6days. UVB-induced nociception (allodynia and hyperalgesia), inflammation (edema and leukocyte infiltration) and oxidative stress (increases in H2O2, protein carbonyl levels and lipid peroxidation and a decrease in non protein thiol content) were reduced by both A. saponaria and sulfadiazine topical treatment. Furthermore, A. saponaria or its constituents aloin and rutin reduced the oxidative stress induced by H2O2 in skin homogenates in vitro. Our results demonstrate that topical A. saponaria treatment displayed anti-nociceptive and anti-inflammatory effects in a UVB-induced sunburn model, and these effects seem to be related to its antioxidant components.