Baccharis dracunculifolia extract modulates murine antigen-presenting cells and attenuates the Th2 immune response in an ovalbumin-induced asthma model

Baccharis dracunculifolia DC. (Asteraceae) is the source plant of Brazilian green propolis, whose protection in allergic asthma models has been attributed to the expansion of regulatory and myeloid-derived suppressor cells. Despite this, the activity of the plant extract itself in allergic asthma remains poorly explored, and its action on antigen-presenting cells (APCs), particularly dendritic cells (DCs), is poorly characterized. This study evaluated the influence of B. dracunculifolia extract (BdE) on murine APCs and on a murine asthma model. J774A.1 macrophages and bone marrow-derived DCs were treated with BdE (25–100 µg/mL) and stimulated with lipopolysaccharide, alone or with IFN-γ. Viability (MTT), nitric oxide (NO, Griess) and cytokines (ELISA) were measured. BALB/c mice (n≥5/group) were sensitized with ovalbumin (OVA) and alum on days 0 and 14, challenged with aerosolized OVA on days 21, 23, 25, 27 and 29, and treated daily by gavage with BdE (150 mg/kg) from day 21 to 29. Bronchoalveolar lavage fluid was used for cell counts, and lung tissue for histology, cytokines and peroxidases. Ethics approval: CEUA/UFJF 017/2018; SisGen #AE32DB3. Results showed that BdE did not affect cell viability. In stimulated macrophages, all BdE concentrations reduced NO, TNF-α, IL-6 and IL-12p40 (almost abolished) and increased IL-10. In DCs, however, the response occurred only at 100 µg/mL, and selectively. While TNF-α and IL-12p40 were reduced, IL-10 increased about 2.7-fold and IL-6 was unchanged. In vivo, BdE reduced total leukocytes, eosinophils and neutrophils, the inflammatory score (4.2 to 2.1), the corresponding peroxidase activities, and levels of IL-4, IL-5, IL-9, IL-13, IL-25, IL-33, TSLP and CCL11 (p<0.05). In conclusion, BdE acts on APCs, redirecting their cytokine profile towards a regulatory pattern rather than suppressing them broadly. It also attenuates an established allergic response, supporting its potential as a therapeutic agent for asthma.