Evaluation of the Cannabidiol effects under neuroimmunoendocrine and behavioral alterations induced by stress in mice

Author(s)

Alice Hartmann dos Santos

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina de Ribeirão Preto (PCARP/BC)
• Defense date: 2020-10-15

Examining board members

Francisco Silveira Guimarães; Newton Sabino Canteras; Fabrício de Araújo Moreira

• Advisor: Francisco Silveira Guimarães; Sabrina Francesca de Souza Lisboa

Abstract

Several pieces of evidence suggest the involvement of proinflammatory cytokines in psychiatric patients as well as in animal models of mental disorders. Interleukin-1β (IL- 1β) levels, widely described as neuroinflammatory agent, is increased in patients with depression, anxiety and post-traumatic stress disorder (PTSD). NFkB and NLRP3 inflammasome pathway mediate IL-1β transcription and function. The activation of this complex has been related to mental disorders. Cannabidiol (CBD) has several therapeutical effects already described. However, the interaction between CBD and immune system, as well as the involvement of immunological mechanisms mediating behavioral effects of this drug, are still poorly understood. This work aimed to evaluate the involvement of NLRP3 inflammasome pathway on the mechanisms by which CBD can prevent of reverse behavioral and neuroimmunoendocrine alterations in animal models. Adult male C57Bl/6 mice were exposed to the following protocols: chronic unpredictable stress (CUS; 21 days), restraint stress (RS; 6h) or 2 inescapable foot shocks (PTSD; 1.5mA). Additionally, an animal model of anxiety, based on selective breeding, was used. Results obtained with CUS model showed a reduction on the body weight, increase in immobility time on the forced swim test as well as hipolocomotion on the open field test of stressed mice in comparison with control. However, on the novelty suppressed feeding test, animals showed that the feeding was generally suppressed and not just by neophobia. Sucrose preference test wasn\'t able to give us reliable results. CBD wasn\'t able to alter behavioral effects induced by stress. Considering the low reproducibility of the results obtained with this model, we decided to use RS. Six hours of RS decreased the time spent and number of entries in the open arms of the elevated plus maze (EPM) 24h and 7 days after stress. There were no changes on the tail suspension test and body weight. Repeated treatment with CBD (30 mg/kg) prevents behavioral consequences of stress in stressed mice, despite induced an anxiogenic-like effect per se in controls. During the abroad internship in Germany, we used mice with high-anxiety trait (HAB) and their respective controls (NAB). HAB mice showed an increase in anxiety related behaviors in the EPM and beetle mania task when compared to NAB. In the auditory fear conditioning test, HAB mice did extinguish aversive memory, however were not able to consolidate extinction memory and spontaneously recovered fear responses when compared to NAB. CBD treatment (15 and 30 mg/kg) did not show any improvement in comparison with vehicle in HAB mice. In the absence of acute CBD effects, we decided to use an animal model of PTSD. Three weeks after the trauma, daily treatment with vehicle or CBD (10-30 mg/kg, 1 injection i.p.) started. After one week of treatment, animals were tested for generalization and long-lasting consequences of shocks. Twenty for hours later, mice were tested for fear expression and recovery. Stress increased freezing time and decreased number of rearings in both tests. Repeated treatment with CBD did not revert the alterations induced by this model. In the same way, there was no effect of stress and/or treatment of mice submitted to trauma and tested in the beetle mania task. In general, the difficulties faced hindered the progress of the project. Results obtained with CUS suggest that this protocol induce changes that makes possible preclinical studies of mental disorders and that repeated treatment with CBD, 30 mg/kg, induce a dual effect that depends on the previous stress condition of the animal. The experiment with HAB lineage evidence that these mice did present innate anxiety-related phenotype, despite CBD had no acute effect. Finally, PTSD model is able to induce robust and long-lasting behavioral alterations in mice. Although CBD wasn\'t able to ameliorate these stress\' effects, this result can suggest that this phytocannabinoid is not effective in patients with PTSD already installed after a long period of trauma; since previous studies by our and other groups have shown that the compound can prevent behavioral consequences in other animal models of PTSD, when administered shorly after the trauma or a new stressor - reminder. (AU)

• FAPESP's process: 16/14282-6 - Evaluation of the Cannabidiol effects under neuroimmunoendocrine and behavioral alterations induced by stress in mice
• Grantee: Alice Hartmann dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate