Effect of selective cannabinoid receptors stimulation on mouse alveolar macrophage

Alveolar macrophages (AMs) act in alveoli microenvironment in physiological conditions and in the recognition and elimination of pathogens, contributing to the inflammatory process (1). The impact of the Cannabis sativa in the pulmonary immunity was poorly addressed in the literature, and the development of specific agonists and antagonists of cannabinoid receptor type 1 (CBR1) and type 2 (CB2R) allowed us to investigate the effect of selective activation of CBRs in key AM functions (2). The objective of this project was to evaluate the effects of stimulation of CB1R and CB2R in AMs of C57BL/6 mice regarding the production of inflammatory mediators. Mice were subjected to bronchoalveolar lavage and the AMs obtained were cultured in vitro under stimulation with specific CB1 (ACEA) and CB2 (HU-308) agonists in the presence of inflammatory stimulus. The quantification of the cytokine secretion (IL-6, TNF- α, CCL3, and CXCL1) and lipid mediators (PGE₂, LTB₄, and Cys-LT) was analyzed by immunoenzymatic assay (ELISA). Nitric Oxide (NO) quantification was assessed using the Greiss assay. Our results show that the treatment with HU-308 (100nM) and ACEA (1µM) did not alter the NO production. Regarding the cytokine secretion, HU-308 (10µM) reduced IL-6, CCL3 and CXCL1 levels, whereas ACEA (10µM) decreased IL-6 and CCL3. Neither agonists tested affected TNF-α production. Additionally, it was observed that the agonists at 10nM reduced Cys-LT secretion, indicating an immunomodulatory action of the inflammatory response in AM. However, we did not observe changes in PGE₂ and LTB₄ production. As a perspective of the project, we will investigate the influence of treatment with cannabinoid agonists on the phagocytic capacity and the polarization profile of the AMs. These findings reinforce that activation of CB2 signaling is capable to attenuate inflammatory response in lung environment.

UFRJ Ethics Committee on Animal Use (CEUA/UFRJ, protocol no. 008/24).