Alveolar macrophage reaction to PM of hazy day in vitro: Evaluation methods and mitochondrial screening to determine mechanisms of biological effect.

Hazy weather in China has recently become a major public health concern due to high levels of atmospheric fine particulate matter (PM) with a large amount of polycyclic aromatic hydrocarbon (PAHs). In this study, the mass concentration of PAHs in hazy PM in urban Taiyuan city, China was determined and toxicities of different dosage of the hazy PM on rat alveolar macrophages (AMs) were examined. It was found that the hazy PM, bounded with many species of PAHs (CHR, BbF, BaP, BaA, and etc.), significantly increased cellular malondialdehyde (MDA) content followed by the decreasing in superoxide (SOD) and glutathione peroxidase (GPx) in AMs. They induced mitochondrial changes in ultrastructure as evidenced by mitochondrial swelling and cristae disorganization, and a dose-dependent decrease in mitochondrial profile density. Also, the mRNA expression levels of mitochondrial fusion-related genes were modified. The Mfn1 and Mfn2 which are essential for mitochondrial fusion increased significantly in hazy PM-treated group compared to the control in a dose-dependent manner, OPA1 was significantly increased at the highest PM dose delivered. These findings suggested that exposure to hazy PM could activate oxidative stress pathways in AMs, resulting in abnormal mitochondrial morphology and fusion/fission frequency. Possibly, the toxic effects were mostly attributed to the high burden of varied PAHs in hazy PM.