Mechanistic studies have been suggested that toxic effects of bleomycin are generally attributed to formation of free radicals, mitochondria damages, oxidative stress and inflammation. For this purpose, we explored the direct exposure of bleomycin and protective effects of the betanin and vanillic acid separately against its possible toxicity in rat lung isolated mitochondria. Various mitochondrial toxicity parameters were evaluated including; succinate dehydrogenases (SDH) activity, reactive oxygen species (ROS) formation, mitochondrial swelling, mitochondrial membrane potential (MMP) collapse, malondialdehyde (MDA) and glutathione disulfide (GSSG) levels. It was found that the direct exposure of isolated mitochondria with bleomycin (500 μM) resulted in a significant decrease of SDH activity (p < 0.001), a significant increase of ROS formation (p < 0.001), MDA content (p < 0.01), mitochondrial swelling (p < 0.001) and collapse of MMP (p < 0.05). Except MMP collapse and GSSG level, betanin treatment had strong protection attenuating the SDH activity (p < 0.001), ROS formation (p < 0.001), mitochondrial swelling (p < 0.001) and MDA production (p < 0.05) in presence of toxic concentration of bleomycin. Additionally, vanillic acid treatment had the same protective effect, but at higher concentrations. However, according to our observations, it seems vanillic acid can be toxic in rat lung isolated mitochondria at concentrations of 100 μM and higher. It was concluded that betanin and vanillic acid could be considered as potential mitochondrial-targeted agents in the reduction of bleomycin-induced toxicity via inhibition of mitochondrial swelling, ROS formation and improvement SDH activity in rat lung isolated mitochondria.
Keywords: Lung toxicity; antioxidants; lung diseases; natural compounds; pulmonary fibrosis.