Abstract
UVA radiation induces multiple and complex changes in the skin, affecting epidermal cell behavior. This study reports the effects of UVA exposure on normal (HaCaT) and dysplastic (DOK) keratinocytes. The adherence, spreading and proliferation were investigated by time-lapse measurement of cell layer impedance on different matrix proteins. Prior to UVA exposure, the time required for adherence and spreading did not differ significantly for HaCaT and DOK cells, while spreading areas were larger for HaCaT cells. Under UVA exposure, HaCaT and DOK cells behavior differed in terms of movement and proliferation. The cells’ ability to cover the denuded surface and individual cell trajectories were recorded by time-lapse videomicroscopy, during wound healing experiments. Dysplastic keratinocytes showed more sensitivity to UVA, exhibiting transient deficiencies in directionality of movement and a delay in re-coating the denuded area. The actin cytoskeleton displayed a cortical organization immediately after irradiation, in both cell lines, similar to mock-irradiated cells. Post-irradiation, DOK cells displayed a better organization of stress fibers, persistent filopodia, and new, stronger focal contacts. In conclusion, after UVA exposure HaCaT and DOK cells showed a different behavior in terms of adherence, spreading, motility, proliferation, and actin cytoskeleton dynamics, with the dyplastic keratinocytes being more sensitive.
Highlights
Ultraviolet type A (UVA) radiation (320–400 nm) represents the main component of the ultraviolet (UV) solar spectrum reaching the Earth’s surface and acting as a stress factor on skin [1,2]
Our results proved that HaCaT and dysplastic oral keratinocytes (DOK) cells have behaved differently after UVA exposure, with the most notable change being the loss in the directionality of movement for the dysplastic cells, accompanied by altered dynamics of actin cytoskeleton and focal contacts
HaCaT and DOK cell behavior before and after UVA irradiation was assessed by time-lapse monitoring of the cell layer impedance, on surfaces coated with matrix proteins at three different concentrations (2.5, 5.0 and 10 μg/mL)
Summary
Ultraviolet type A (UVA) radiation (320–400 nm) represents the main component of the ultraviolet (UV) solar spectrum reaching the Earth’s surface and acting as a stress factor on skin [1,2]. UVA irradiation induces oxidative stress and activates complex signaling pathways which are involved in fundamental cellular events in the skin, including adhesion, proliferation, differentiation, senescence, malignant transformation and cell death [5,6,7,8]. UVA can disturb epidermal intercellular adhesion [10] and cell-to-cell communication mediated by gap junctions as shown in primary keratinocytes [11]. It may be presumed that UVA exposure affects the attachment of keratinocytes to the basement membrane, which might disturb their motility
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