Investigação do efeito antinociceptivo do monoterpeno hidroxicitronelal por meio de abordagens in sílico e in vivo

Abstract

Pain is described as an unpleasant sensory and emotional experience associated with or resembling actual or potential tissue damage, being an important defense system of the organism. However, pain conditions, especially chronic pain, have a great impact on people's quality of life. Such health conditions commonly interfere with daily activities and individual well-being, being constantly associated with depressive symptoms and impaired social relationships. The search for new analgesics has been a priority for pharmacology researchers and the pharmaceutical industry, seeking safer and more effective drugs. In this sense, natural products present several potential bioactive compounds for pain treatment, among these compounds is hydroxicitronellal (HC), a monoterpene promising for the regulation of nociceptive processes. Thus, this work aims to investigate the antinociceptive effect of HC through in silico and in vivo methodologies. Initially, in silico studies were performed using the molecular docking tool, in order to evaluate the binding energy and interaction of HC with important targets involved in the nociceptive response. After that, in vivo studies were performed, in which Swiss albino mice (Mus musculus) males, about 3 months old, were subjected to the Acetic Acid-Induced Abdominal Contortions Test, Hot Plate Test, Formalin Test, Nociception Test Induced by Intraplantar Glutamate Injection, and subsequently, the participation of the opioid pathway in the formalin test was evaluated. For statistical analysis of in vivo studies, the Shapiro-Wilk test was performed to verify the normality of the data, and then the data were analyzed through one-way Analysis of Variance (ANOVA), followed by Tukey's post hoc test, being considered significant when p < 0.05. The results of the computational studies showed that HC has good binding energy with 7 of the 12 proteins studied, namely the 5-HT2B receptor, COX-2 enzyme, muscarinic M5 receptor, alpha-2a- adrenergic receptor, opioid μ receptor and TRPM3 and TRPV6 ion channels. Subsequently, in vivo studies were performed, in which the concentrations of 12.5, 25 and 50 mg/kg (i.p.) were used to evaluate the antinociceptive activity. In the acetic acid-induced abdominal contractions test, HC was able to reduce contractions significantly at all three doses when compared to control, with no difference between doses. In the first phase of the formalin test, there was a significant reduction in paw licking time, with HC at 12.5 mg/kg being the one with the greatest reduction, a fact that was reversed in the second phase of the test, in which all 3 doses obtained a significant reduction when compared to control, with HC at 25 and 50 mg/kg showing less licking time compared to the lowest dose (12.5 mg/kg). In the hot plate test, HC was not able to increase latency to nociceptive response at any of the tested doses. In the glutamate-induced nociception test, HC (12.5 mg/kg) was able to reduce licking time in both phases of the test compared to control, and a potentiated antinociceptive effect was observed by the association of HC with the glutamatergic antagonist MK-801. In the investigation of the participation of the opioid pathway, the antinociceptive effect of HC was not reversed by the use of the opioid antagonist naloxone in either phase of the formalin test. In view of this, this work demonstrated that HC has positive interactions with several nociception regulatory targets, presenting an antinociceptive effect in animal models, with a possible action through the glutamatergic pathway.