Protective Effects of Titanium Dioxide-based Emulsion after Short-term and Long-term Infrared-A Ray Irradiation on Skin Cells

Chronic infrared‐A irradiation‐induced photoaging of human dermal fibroblasts from different donors at physiological temperature

“…11,34,35 In our previous study, the level of PIP in CCD cells did not change after 3 IRA exposures at 34°C. 5 However, chronic IRA irradiation significantly reduced the level of PIP in this study (Figure 7). This result indicates that repeated IRA exposure is needed to decrease the extent of collagen protein expression.…”

“…However, we observed harmful effects by acute IRA irradiation in the presence of heat stresses in our previous study. 5 While acute IRA irradiation elicited negligible cellular damages at 34°C, acute IRA with heat stress at 43°C induced decrease in collagen level and attenuated cell proliferation. In addition, chronic IRA irradiation also elicited morphological changes in nucleus to elongated shape.…”

“…Infrared‐A (IRA, 700–1400 nm) radiation constitutes approximately 30% of solar infrared radiation, which can penetrate down to the hypodermis and affect various types of cells in the skin 3,4 . However, the effects of IRA irradiation on skin cells are controversial, probably because of differences in IRA exposure conditions, such as the intensity of irradiation, exposure period, and temperature 5,6 . In addition, heat stresses during IRA irradiation on skin can induce various harmful effects, including the generation of reactive oxygen species (ROS) and apoptotic signals, making it difficult to understand the biological effects of IRA irradiation alone 7,8 .…”

“…3,4 However, the effects of IRA irradiation on skin cells are controversial, probably because of differences in IRA exposure conditions, such as the intensity of irradiation, exposure period, and temperature. 5,6 In addition, heat stresses during IRA irradiation on skin can induce various harmful effects, including the generation of reactive oxygen species (ROS) and apoptotic signals, making it difficult to understand the biological effects of IRA irradiation alone. 7,8 Hence, it is necessary to study the cellular effects of IRA irradiation alone under defined conditions of duration, frequency, and dose of IRA irradiation, as well as…”

“…5 2.2 | Growth curve of CCD and NHDF cellsHuman dermal fibroblast cell lines, namely CCD-1059SK (CCD; donor age: 20 years, female) and normal human dermal fibroblast (NHDF; donor age: 50 years, female), were purchased from American Type Culture Collection (ATCC, Manassas, VA, USA) and Lonza (Basel, Switzerland), respectively. The fibroblasts were maintained in DMEM supplemented with 10% FBS, 100 U/ml penicillin, and 100 μg/mL streptomycin at 37°C under a humidified atmosphere of 5% CO 2 .…”