Steady-state mRNA levels of interleukin-1, integrins, cJun, and cFos in hairless mouse skin during short-term chronic UV exposure and the effect of topical tretinoin

We have proposed that UV activation of cytokine and integrin signaling path ways may initiate the photoaging process and that one of the effects of tre tinoin treatment may be to alter the cytokine and integrin patterns. In pre vious results, steady-state mRNA levels of interleukin-1 alpha, tumor necro sis factor ct, transforming growth factor beta, collagenase, stromelysin, c ollagen, and integrins (alpha(1) and alpha(2)) were increased in the skin o f hairless mice that were either UV treated or concurrently treated with UV followed by topical tretinoin for 5 weeks. The aim of this study was to fo cus on the expression of alpha(1), alpha(2) and alpha(5), integrins, IL-1 a lpha, IL-1 beta, cJun, and cFos at an earlier time paint (3 weeks). Animals were UV irradiated thrice weekly For 3 weeks and were treated topically wi th. either 0.05% tretinoin err the vehicle immediately after each exposure. Total RNA was prepared and used in RT-PCR with radiolabeled dCTP and speci fic primers. UV slightly increased steady-state mRNA levels for alpha(1), a lpha(2) and alpha(5) integrins whereas UV+tretinoin increased their express ion (3-, 2- and 7-fold respectively). Steady-state mRNA levels for IL-1 alp ha, IL-1 beta and cJun were increased with UV (3-, 12- and 6-fold respectiv ely) and with UV+tretinoin (6-, 7- and 9-fold respectively). In contrast, c Fos expression was unchanged. In situ staining for IL-1 alpha. mRNA was sli ghtly more abundant in mice treated for 3 weeks with UV and UV+tretinoin th an in controls whereas 5 weeks of UV+tretinoin treatment gave strongly posi tive staining. Results are consistent with cytokines and integrins mediatin g the effects of UV on the skin, with modulation of these effects by tretin oin.