Background:PM(aerodynamic diameter ≤ 2.5 μm) is a dominant and ubiquitous air pollutant that has become a global concern as PMexposure has been linked to many adverse health effects including cardiovascular and pulmonary diseases. Emerging evidence supports a correlation between increased air PMlevels and skin disorders although reports on the underlying pathophysiological mechanisms are limited. Oxidative stress is the most common mechanism of PM-induced adverse health effects. This study aimed to investigate PM-induced oxidative damage and apoptosis in immortalized human keratinocyte (HaCaT) cells.

Methods:HaCaT cells were exposed to 0, 25, 50, 100, or 200 μg/ml PMfor 24 h. Reactive oxygen species (ROS) generation, lipid peroxidation products, antioxidant activity, DNA damage, apoptotic protein expression, and cell apoptosis were measured.

Results:PMexposure (0-200 μg/ml) for 24 h resulted in increased ROS levels (arbitrary unit: 201.00 ± 19.28, 264.50 ± 17.91, 305.05 ± 19.57, 427.95 ± 18.32, and 436.70 ± 17.77) and malondialdehyde production (0.54 ± 0.05 nmol/mg prot, 0.61 ± 0.06 nmol/mg prot, 0.68 ± 0.05 nmol/mg prot, 0.70 ± 0.05 nmol/mg prot, and 0.76 ± 0.05 nmol/mg prot), diminished superoxide dismutase activity (6.47 ± 0.28 NU/mg prot, 5.97 ± 0.30 NU/mg prot, 5.15 ± 0.42 NU/mg prot, 4.08 ± 0.20 NU/mg prot, and 3.76 ± 0.37 NU/mg prot), and increased DNA damage and apoptosis in a dose-dependent manner in HaCaT cells. Moreover, cytochrome-c, caspase-3, and caspase-9 expression also increased proportionately with PMdosing.

Conclusion:PMmight elicit oxidative stress and mitochondria-dependent apoptosis that likely manifests as skin irritation and damage.