Ultraviolet B radiation increases steady-state mRNA levels for cytokines and integrins in hairless mouse skin: Modulation by topical tretinoin

Chronically sun-damaged human skin has a wrinkled, aged appearance as a result of alterations in the dermal extracellular matrix. Secondary effecters such as cytokines and integrins may mediate the effects of UV radiation on the skin by regulating the synthesis of metalloproteinases and structural proteins including collagen. The aim of this study was to semiquantify the steady-state mRNA levels of interleukin-1α, tumor necrosis factor α, transforming growth factor β, collagenase, stromelysin, collagen, and integrins (α₁ and α₂) in the skin of hairless mice that were either treated with UV or concurrently treated with UV and topical tretinoin for 5 weeks. Total RNA was extracted from the skin of the mice, reverse transcribed to cDNA, and amplified by the polymerase chain reaction in the presence of ³²P-dCTP using gene-specific primers. Results were normalized relative to glyceraldehyde-3-phosphate dehydrogenase levels. Steady-state mRNA levels of the cytokines and integrins were increased by UV radiation. Concurrent UV and topical tretinoin treatment superinduced the expression of interleukin-1, increased α₁ and decreased α₂ integrin expression. Immunofluorescence analysis showed increased dermal localization of β₁ integrin in UV and tretinoin treated skin. These results suggest that cytokines and integrins may be involved in the mechanism of photodamage.