Role Of UVB Research Articles

Activation of p38 MAP kinase and ERK are required for ultraviolet-B induced c-fos gene expression in human keratinocytes.

The effects of p38 MAP kinase and ERK on UVB induced c-fos gene expression were studied in a human keratinocyte cell line, FL30. UVB significantly increased c-fos gene expression at both the transcriptional and protein levels. p38 and ERK were also significantly activated after UVB irradiation. Treating the cells with p38 inhibitor SB202190 inhibited p38 activation, but not ERK; treating the cells with MEK-1 inhibitor PD98059 inhibited ERK activation without suppressing p38 activation. The kinase activation was determined by Western blots using phospho-p38 or ERK antibodies, or an in vivo p38 activity assay. Further studies demonstrated that blocking p38 almost completely abrogated UVB induced c-fos gene transcription and c-Fos protein synthesis. Inhibiting ERK partially abrogated UVB induced c-fos transcriptional and protein levels. Suppression of both p38 and ERK not only completely blocked UVB induced c-fos expression, but also decreased c-fos gene basal expression. Our data indicated that p38 may play a more important role than ERK in UVB induced c-fos expression in human keratinocytes. Since c-fos expression may play an important role in UVB induced AP-1 activation, and AP-1 activation is known to play a role in tumor promotion, both p38 and ERK could be potential targets for chemoprevention of skin cancer.

Photoageing: the role of UVB, solar-simulated UVB, visible and psoralen UVA radiation.

We have studied the morphological and histological effects of chronic exposure of two strains of haired mice (albino Balb/c and pigmented C3H-) to various types of radiation. UVB (280-320 nm) radiation from unfiltered sunlamp bulbs for 20 and 30 weeks produced marked epidermal acanthosis and dyskeratosis which was reversible in mice exposed for 20 weeks followed by a 20-week rest. In the dermis the elastic fibres were altered and in the pigmented mice these changes had almost completely reversed 29 weeks after cessation of exposure. Cellulose acetate-filtered sunlamp bulbs (greater than 289 nm) produced similar but less marked changes. Chronic exposure to UVA (320-400 nm) radiation produced minimal alterations in the dermis while the epidermis was normal. Visible (greater than 400 nm) radiation in large doses produced no degenerative changes. Methoxsalen/UVA radiation produced epidermal acanthosis, dermal sclerosis, and alteration of elastic fibres, which was prominent in both strains at 40 weeks. These findings suggest that the UVB component of sunlight is largely responsible for photoageing of the skin. Furthermore, chronic exposure to methoxsalen/UVA therapy is likely to potentiate solar-induced photoageing.