Brazilian Red Propolis shows antifungal and immunomodulatory activities against Paracoccidioides brasiliensis

Abstract

Ethnopharmacological relevance: Paracoccidioidomycosis (PCM) is a systemic mycosis with high prevalence in South America and especially in Brazil with severe clinical consequences that need broadened therapeutic options. Propolis is a natural resin from bees used in folk medicine for centuries with the first report in the ancient history of Egypt by Eberly papyrus, in Middle-Ages used to wash the newborn's umbilical cord and World War II as antiseptic or antibiotics. Nowadays it is a natural product worldwide consumed as food and traditionally used for oral and systemic diseases as an anti-inflammatory, antimicrobial, antifungal, and other diseases. Brazilian red propolis (BRP) is a new type of propolis with a distinguished chemical profile and biological activities from propolis (green) with pharmacological properties such as antimicrobial, anti-inflammatory, antioxidant, and others.

Aim of study: Thus, the main purpose of this study was to investigate the direct in vitro and ex vivo effect of BRP on Paracoccidioides brasiliensis.

Material and methods: Antifungal activity of different concentrations of BRP on a virulent P. brasiliensis isolate (Pb18) was evaluated using the microdilution technique. Also, mice splenic cells co-cultured with Pb18 were treated with BRP at different times and concentrations (only Pb18 = negative control). Mice were inoculated with Pb18 and treated with different concentrations of BRP (50-500 mg/mL) in a subcutaneous air pouch. In this later experimental model, macroscopic characteristics of the air pouch were evaluated, and cellular exudate was collected and analyzed for cellular composition, mitochondrial activity, total protein reactive oxygen specimens (ROS), and nitric oxide production, as well as the number of viable fungal cells.

Results: The in vitro experiments showed remarkable direct antifungal activity of BRP, mainly with the highest concentration employed (500 mg/mL), reducing the number of viable cells to 10% of the original inoculum after 72 h incubation. The splenocytes co-cultivation assays showed that BRP had no cytotoxic effect on these cells, on the contrary, exerted a stimulatory effect. This stimulation was also observed on the PMNs at the air pouch, as verified by production of ROS and total proteins and mitochondrial activity. This activation resulted in enhanced fungicidal activity, mainly with the 500 mg/mL concentration of BRP. An anti-inflammatory effect was also detected, as verified by the smaller volume of the BRP-treated air pouch as well as by an earlier shift from neutrophils to mononuclear cells present in the infection site.

Conclusion: Our results strongly suggest, for the first time in the literature, that Brazilian Red propolis has four protective mechanisms in experimental paracoccidioidomycosis: activating neutrophils, exerting a direct antifungal effect, preventing fungal dissemination, and controlling excessive inflammation process.

Keywords: Anti-inflammatory activity; Antifungal activity; Natural products; Neutrophils activation; Paracoccidioidomycosis.