The transient receptor potential ankyrin 1 (TRPA1) has been identified as a relevant target for the development of novel analgesics. Gallic acid (GA) is a polyphenolic compound commonly found in green tea and various berries and possesses a wide range of biological activities. The goal of this study was to identify GA as a TRPA1 antagonist and observe its antinociceptive effects in different pain models. First, we evaluated the ability of GA to affect cinnamaldehyde-induced calcium influx. Then, we observed the antinociceptive and antiedematogenic effects of GA (3-100 mg/kg) oral administration after the intraplantar (i.pl.) injection of TRPA1 agonists (allyl isothiocyanate, cinnamaldehyde, or hydrogen peroxide-H2O2) in either an inflammatory pain model (carrageenan i.pl. injection) or a neuropathic pain model (chronic constriction injury) in male Swiss mice (25-35 g). GA reduced the calcium influx mediated by TRPA1 activation. Moreover, the oral administration of GA decreased the spontaneous nociception triggered by allyl isothiocyanate, cinnamaldehyde, and H2O2. Carrageenan-induced allodynia and edema were largely reduced by the pretreatment with GA. Moreover, the administration of GA was also capable of decreasing cold and mechanical allodynia in a neuropathic pain model. Finally, GA was absorbed after oral administration and did not produce any detectable side effects. In conclusion, we found that GA is a TRPA1 antagonist with antinociceptive properties in relevant models of clinical pain without detectable side effects, which makes it a good candidate for the treatment of painful conditions.

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Medulloblastomas (MB) occur in the central nervous system and are the most common pediatric intracranial tumors. Despite the knowledge regarding the molecular biology of these tumors, patients still suffer long-term side effects in consequence of the current treatments. Several advances have collaborated to the identification of new therapeutic targets for cancer treatment, including the characterization of BDNF/TrkB signalling in cell fate. This pathway has been associated with increased proliferative capabilities, invasiveness, and chemotherapy resistance in many types of cancer. We have previously shown that the selective TrkB inhibitor, ANA-12, markedly reduced the viability and survival of MB cell lines. These findings provided a rationale to further investigations relating TrkB inhibition as a potential novel strategy for MB treatment. We investigated the effects of ANA-12 in apoptosis and the effects of combined treatment with cisplatin in MB cell viability. Human MB cell lines D283 and UW-228 were treated with increasing concentrations of ANA-12 (5, 20, or 30 μM) or BDNF (50 ng/ml) for 24 or 48 hours. Cells were also treated with different combinations of ANA-12 and cisplatin for 48 hours. Cell viability was assessed by trypan blue cell counting. Cell apoptosis was analyzed by flow cytometry to annexin-V and propidium iodide staining. Data represent at least three independent experiments performed in triplicates. Statistical analyses: two-way ANOVA followed by followed by Tukey for multiple comparisons. We found that ANA-12 leads to a dose- and time-dependent reduction of D283 and UW-228 MB cell viability. ANA-12 at 30 μM increased the population of apoptotic cells in both MB cell lines. In D283 29.9% and 61.9% of the cells were apoptotic after 24 and 48 hours of treatment, respectively. In UW-228 apoptosis rates were 49.1% after 24 hours and 80.7% after 48 hours. When used in combination, ANA-12 enhanced cisplatin cytotoxic effects in UW-228 cells. Cell viability in the presence of 5 μM of cisplatin alone was 37.48% (UW-228) and 49.8% (D283), but decreased with the combination of 20 μM of ANA-12, 18.4% (UW-228) and 23.4% (D283). Here we present the evidence that in human MB, ANA-12 decreases viability, induces apoptosis, and acts synergistically with cisplatin in suppressing MB cell viability. Citation Format: Amanda Thomaz, Kelly V. Pinheiro, Camila A. da Silva, Caroline B. de Farias, Rafael Roesler. Anticancer activity of selective TrkB inhibition in medulloblastoma cells [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A66.