Investigação das propriedades imunomoduladoras do extrato GGA e sua ação no tratamento da alergia pulmonar

Abstract

The immune responses are fundamental to the defense and, consequently, to the survival of organism. However, uncontrolled immune responses may lead to the development of chronic diseases, such as asthma, which represent the greatest burden of morbidity and mortality in Brazil. Also, although there are several ways to modulate the immune system and treat related diseases, these therapies have several side effects and do not guarantee cure. Thus, the need for new, more effective approaches to immune system control is evident. In this context, medicinal plants stand out because they are sources of biologically active compounds. Under this circumstances, the present study aimed to investigate, in vitro and in vivo, the immunomodulatory properties of a plant extract called GGA. As a methodology, the toxicity of the extract was initially determined on different cells of the immune system by the MTT assay. Then, macrophages (M) and dendritic cells (DCs) were used to evaluate the influence of the extract on the production of nitric oxide (NO) and cytokines (GRIESS and ELISA method, respectively). The influence of the extract on the expression of costimulatory molecules as well as the CD73 molecule was determined by flow cytometry. To relate the effects of the extract to the purinergic system, pharmacological blockers of CD73 or adenosine receptors were used. In relation to the in vivo assays, BALB/c mice were submitted to the ovalbumin-induced pulmonary allergy model and treated with oral GGA. In these animals the number and type of cells in the bronchoalveolar lavage (BAL) were evaluated, as well as the inflammatory infiltrate and the presence of mucus in the lungs. In addition, lung tissue was used to determine the production of cytokines and the activity of the enzymes eosinophilic peroxidase (EPO) and myeloperoxidase (MPO). Levels of IgE and IgG2A were evaluated in serum. In vitro results revealed that, at non-toxic concentrations, the extract is able to reduce the production of inflammatory mediators while increasing IL-10 production in both M and DCs. In these cells, the treatment also induced an increased expression of costimulatory molecules. GGA also induced increased expression of the molecule both M and DCs and lymphocytes. Associated with this, blockade of CD73 or adenosine receptors partially restored NO production by M, demonstrating that the action of the extract is associated with the modulation of the purinergic system. In vivo, treatment with extract reduced the number of total cells, eosinophils and neutrophils in BAL, in addition to inflammatory infiltrate and goblet cells in the lung. Treatment with GGA also reduced the production of cytokines IL-4, IL-5, TSLP, IL-33, IL-9, IL-25, CCL11 and IL-13 such as the activity of the EPO and MPO enzymes. Interestingly, the treatment promoted a reduction in serum IgE levels and an increase in IgG2a. The results suggest that the extract is able to modulate the immune response and these effects seem to be related to the modulation of the purinergic system. In this way, GGA extract demonstrates potential for use in the treatment of chronic inflammatory diseases, such as asthma, and may compose future therapies.