The Role of Natural Antioxidants in the Attenuation of Mycolactone Toxicity in Buruli Ulcer Disease

Abstract

Mycobacterium ulcerans’ mycolactone, is reported to mediate the production of ROS in keratinocytes; cells that play critical role in wound healing. The key stimulatory function of macrophages in the production of keratinocytes and fibroblasts during wound healing may also be impaired by mycolactone-mediated ROS. To ensure regeneration of tissues with proper and timely healing of the wounds, antioxidants that can combat the effects of ROS ought to be investigated. This study was therefore aimed at determining ROS activity in RAW 264.7 macrophages in the presence of mycolactone using fluorescein probe (DCF-DA) and nitroblue tetrazolium (NBT) solution. It also assessed the protective effect of the antioxidants (ascorbic acid, gallic acid and green tea Kombucha) to the cells upon treatment with mycolactone using cell viability assays. The mechanism of cell death induced by the mycolactone was investigated using fluorescence microscopy.The expression levels of endogenous antioxidant enzyme genes (catalase, superoxide dismutase and glutathione peroxidase) in response to mycolactone-mediated ROS were determined using RT-qPCR. Mycolactone induced the production of ROS in RAW 264.7 macrophages, whilst the ROS were scavenged by the antioxidants. The presence of some antioxidants enhanced the viability of the cells based on the model of treatment, hence the attenuation of the cytotoxic effects of mycolactone. The endogenous antioxidant enzymes were up-regulated in the presence of the antioxidants. The results provide insights into alternative therapeutic approaches in Buruli ulcer treatment, which could prevent or delay ulcer formation and possibly enhance wound healing.