Daniela Almeida Cabrini

Inflammatory pain: kinins and antagonists.

This short review focuses on the most recent findings in the rapidly expanding field of kinin research. Through a series of recent publications, the crucial relevance of this group of peptides as mediators of inflammatory pain is becoming increasingly evident. On the strength of this idea, kinins have been implicated as algogen peptides produced in response to noxious stimuli. The importance of kinins has been elucidated by different pharmacological and molecular approaches. Special attention has been given to studies with selective kinin antagonists, as well as to the use of receptor gene deletion technology. The gathering of results has demonstrated that both B1 and B2 receptors seem to exert a meaningful role during nociceptive responses, the B1 receptor being most relevant in the chronic stages of inflammatory pain. It is hoped that new effective and useful therapeutic agents, mainly B1 kinin selective receptor antagonists, might soon be available.

Bradykinin B1 Receptor Expression Induced by Tissue Damage in the Rat Portal Vein A Critical Role for Mitogen-Activated Protein Kinase and Nuclear Factor-κB Signaling Pathways

The bradykinin B1 receptor (B1R) is normally absent under physiological conditions, but is highly inducible during inflammatory conditions or following tissue damage. The present study attempted to determine some of the mechanisms underlying B1R upregulation following tissue injury in rat portal vein. Damage induced by tissue isolation and in vitro incubation caused a significant and time-dependent increase in des-Arg9–bradykinin (des-Arg9–BK) responsiveness that paralleled the B1R mRNA expression, as confirmed by real-time quantitative PCR. In vitro incubation of rat portal vein also induced the activation of some members of the mitogen activated protein kinase (MAPK) family, namely, extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAPK, an effect accompanied by degradation of the inhibitory protein IκB&agr; and translocation of nuclear transcription factor-κB (NF-κB) to the nucleus. The blockade of p38 MAPK, JNK or NF-κB, but not ERK pathways with selective inhibitors, resulted in a significant reduction of the upregulated contractile response caused by the selective B1R agonist des-Arg9–BK, and largely prevented the induction of B1R mRNA expression in the rat portal vein. Together, these results demonstrate that in vitro tissue damage induces activation of several intracellular signaling pathways that have a key role in the control of B1R expression. B1R could exert a pivotal role in the development of the cardiovascular response associated with vascular damage.

Mechanisms operated by endothelin ETA and ETB receptors in the trigeminal ganglion contribute to orofacial thermal hyperalgesia induced by infraorbital nerve constriction in rats

Endothelins, acting through specific endothelin ET(A) and/or ET(B) receptors, participate in nociceptive processing in models of cancer, inflammatory and neuropathic pain. The present study investigated which cell types express endothelin receptors in the trigeminal ganglion, and the contribution of mechanisms mediated by endothelin ET(A) and ET(B) receptors to orofacial heat hyperalgesia induced by unilateral constriction of the infraorbital nerve (CION). Both receptor types were identified by immunohistochemistry in the trigeminal ganglion, ET(A) receptors on small-sized non-myelinated and myelinated A-fibers and ET(B) receptors on both satellite glial cells and small-sized non-myelinated neuronal cells. CION promoted ipsilateral orofacial heat hyperalgesia which lasted from Day 2 until Day 10 after surgery. Ongoing CION-induced heat hyperalgesia (on Day 4) was reduced transiently, but significantly, by systemic or local treatment with antagonists of endothelin ET(A) receptors (atrasentan, 10 mg/kg, i.v.; or BQ-123, 10 nmol/lip), endothelin ET(B) receptors (A-192621, 20 mg/kg, i.v.; or BQ-788, 10 nmol/ lip), or of both ET(A)/ET(B) receptors (bosentan, 10 mg/kg, i.v.; or BQ-123 plus BQ-788, each at 10 nmol/lip). On the other hand, CION-induced heat hyperalgesia was transiently abolished over the first 90 min following i.p. injection of morphine hydrochloride (2.5 mg/kg), but fully resistant to reversal by indomethacin (4 mg/kg, i.p.) or celecoxib (10 mg/kg, i.p.). Thus, heat hyperalgesia induced by CION is maintained, in part, by peripheral signaling mechanisms operated by ET(A) and ET(B) receptors. Endothelin receptors might represent promising therapeutic targets for the control of trigeminal neuropathic pain.

Anti-inflammatory effects of hydroalcoholic extract and two biflavonoids from Garcinia gardneriana leaves in mouse paw oedema.

Garcinia gardneriana (Planch. & Triana) Zappi (Clusiaceae) is widely distributed in Brazil and used in folk medicine to treat inflammation, pain, and urinary tract and other infections. However, very few studies have analyzed these therapeutic effects. In this study, the anti-inflammatory effects of the hydroalcoholic extracts from Garcinia gardneriana (HEGG) and some of its isolated biflavonoids were evaluated. The results showed that HEGG from the leaves, bark and seeds reduced carrageenan-induced mouse paw inflammation, in addition to diminishing the myeloperoxidase activity in the stimulated tissues. The reduction of neutrophil infiltration by treatment with the HEGG from leaves was confirmed by histology. The leaf extract also reduced the paw oedema evoked by bradykinin, histamine, prostaglandin E2 and 12-O-tetradecanoylphorbol acetate. However, it partially decreased substance P and compound 48/80-caused paw oedema, without any influence on the arachidonic acid-induced oedema. Both of the isolated compounds, fukugetin and GB-2a, prevented the carrageenan-induced paw oedema. In conclusion, this study showed important anti-inflammatory effects of HEGG through its interaction with different intracellular signaling pathways, without interfering with the formation of arachidonic acid (AA) metabolites. These characteristics, in addition to the wide distribution and culturing ease of the plant, confirm its popular use and highlight its promise in the development of new anti-inflammatory drugs.

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.

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.

Analysis of the Potential Topical Anti-Inflammatory Activity of Averrhoa carambola L. in Mice

Inflammatory skin disorders, such as psoriasis and atopic dermatitis, are very common in the population; however, the treatments currently available are not well tolerated and are often ineffective. Averrhoa carambola L. (Oxalidaceae) is an Asian tree that has been used in traditional folk medicine in the treatment of several skin disorders. The present study evaluates the topical anti-inflammatory effects of the crude ethanolic extract of A. carambola leaves, its hexane, ethyl acetate, and butanol fractions and two isolated flavonoids on skin inflammation. Anti-inflammatory activity was measured using a croton oil-induced ear edema model of inflammation in mice. Topically applied ethanolic extract reduced edema in a dose-dependent manner, resulting in a maximum inhibition of 73 ± 3% and an ID50 value of 0.05 (range: 0.02–0.13) mg/ear. Myeloperoxidase (MPO) activity was also inhibited by the extract, resulting in a maximum inhibition of 60 ± 6% (0.6 mg/ear). All of the fractions tested caused inhibition of edema formation and of MPO activity. Treatment with the ethyl acetate fraction was the most effective, resulting in inhibition levels of 75 ± 5 and 54 ± 8% for edema formation and MPO activity, respectively. However, treatment of mice with isolated compounds [apigenin-6-C-β-l-fucopyranoside and apigenin-6-C-(2″-O-α-l-rhamnopyranosyl)-β-l-fucopyranoside] did not yield successful results. Apigenin-6-C-(2″-O-α-l-rhamnopyranosyl)-β-l-fucopyranoside caused only a mild reduction in edema formation (28 ± 11%). Taken together, these preliminary results support the popular use of A. carambola as an anti-inflammatory agent and open up new possibilities for its use in skin disorders.

Pre-clinical anti-inflammatory aspects of a cuisine and medicinal millennial herb: Malva sylvestris L.

Malva sylvestris has been used since ancient times for its emollient, laxative and anti-inflammatory properties, being extensively used as salads, soups and teas. The preset study evaluated the topical anti-inflammatory action of M. sylvestris hydroalcoholic extract (HE) and its compounds in mice ear inflammation caused by 12-O-tetradecanoylphorbol-acetate in mice. The LC-MS analysis of the HE confirmed the presence of scopoletin, quercetin and malvidin 3-glucoside compounds in the HE of M. sylvestris. Topical application of the HE reduced ear oedema, polymorphonuclear cells influx (myeloperoxydase activity and histological analysis) and interleukin-1β levels in the tissue. The topical application of the compound present in the HE, malvidin 3-glucoside was also able to inhibit ear oedema and leukocytes migration. The other tested compounds, scopoletin, quercetin and malvidin 3,5-glucoside were able to prevent the formation of oedema and cell infiltration, but with less effectiveness when compared to HE and malvidin 3-glucoside. Therefore, these results consistently support the notion that M. sylvestris leaves possesses topical anti-inflammatory activity, the compound malvidin 3-glucoside seems to be major responsible for this effect, with the participation of other anti-inflammatory compounds in the extract. Thus, as recommended by population, M. sylvestris can be used as a future treatment to skin disorders.

Structure of the mammalian kinin receptor gene locus

The genes encoding the two kinin receptors, B1 and B2, are closely linked on the same chromosome in human, mouse, and rat. In this article, we present the organisation of the B B2 locus in these mammals. This organisation was obtained by comparing the kinin receptor mRNA sequences of man and mouse with the sequence of chromosomes 14 and 12, respectively. We found that the two genes are located in tandem orientation, separated by only 7.8 kb in mice and 12 kb in humans. The distance of the two genes on rat chromosome 6 was determined by long-range PCR to be 9.5 kb. The organisation of the two genes encoding the kinin receptors is similar in the three species, except that the human B1 gene harbors an additional exon, which may originate from the insertion of an Alu repetitive sequence during evolution. Moreover, the human and rat, but not the murine, B2 genes carry an alternatively spliced exon between exons 2 and 3, termed exon 2b.

Morinda citrifolia Linn (Noni): In vivo and in vitro reproductive toxicology

UNLABELLED Morinda citrifolia Linn (syn. Noni) is a plant widely used as food and medicine worldwide but there are no toxicological tests about this plant focused on reproduction. AIM OF THE STUDY To investigate possible endocrine activity and toxic effect on the reproductive system of Wistar rats by exposure of aqueous extract of the Morinda citrifolia. MATERIALS AND METHODS Two experimental protocols in vivo were developed, (a) uterotrophic assay and (b) in utero and lactational assay, and one test in vitro to investigate the effect on the contractility of pregnant uteri isolated from rats (doses of the extract: 7.5, 75 and 750 mg/kg). RESULTS The uterotrophic assay indicates presence of in vivo antiestrogenic activity of extract at doses of 7.5 and 750 mg/kg. The in utero and lactation exposure showed that the treatment with extract at the dose of 7.5mg/kg induced a reduction of 50% in parturition index and an increase of 74% in postimplantation losses index. The in vitro test showed that uteri from rats treated with 7.5mg/kg of the extract presented a 50% reduction on contraction induced by arachidonic acid. CONCLUSION The exposure of aqueous extract of Morinda citrifolia in Wistar rats induced reproductive toxicity in nonlinear dose-response.