ABSTRACT
<p><b>Background:</b>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.</p><p><b>Methods:</b>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.</p><p><b>Results:</b>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.</p><p><b>Conclusion:</b>PMmight elicit oxidative stress and mitochondria-dependent apoptosis that likely manifests as skin irritation and damage.</p>
ABSTRACT
<p><b>BACKGROUND</b>Cathepsin B plays an important role in cell cycle, extracellular matrix changes and cutaneous tumorigenesis: whether it plays a role in photoaged skin remains unknown. This study aimed to investigate the role of cathepsin B in skin photoaging in vivo and in vitro.</p><p><b>METHODS</b>The expressions of cathepsin B were compared with immunohistochemical methods in solar exposed skin and solar protected skin of six healthy Chinese volunteers. The mRNA and protein expression of cathepsin B in ultraviolet light A (UVA) induced premature senescence fibroblasts in vitro were detected by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting technique.</p><p><b>RESULTS</b>Decreased expression of cathepsin B was observed in photoaged skin compared with that of the solar protected skin. In the UVA induced, premature senescence fibroblasts, a lower expression of cathepsin B was detected by Western blotting and a decreased synthesis of cathepsin B mRNA in the same cells was revealed by real-time RT-PCR.</p><p><b>CONCLUSIONS</b>The results demonstrated a significant negative correlation between skin photoaging and cathepsin B in vitro and in vivo. We propose that cathepsin B, besides matrix metalloproteinases and antioxidant enzymes, is involved in the process of skin photoaging in that it contributes to extracellular matrix remodelling and is a dominant protease in cellular apoptosis and senescence.</p>