THE EFFECT OF ACUTE AND CHRONIC PHOTODAMAGE ON GENE-EXPRESSION IN HUMAN KERATINOCYTES

We identified genes involved in the normal response to acute UV damage, as they were modulated in cultured newborn keratinocytes by a single sublethal UV dose, appropriately filtered to mimic solar radiation. Their gene products encode proteins involved in the regulation of cell growth (proto-oncogenes c-myc and c-fos), a gene inducible by growth arrest and DNA damage (GADD153), the cytokine interleukin (LL) 1 alpha and beta and finally a differentiation-associated small proline-rich gene (SPR2). Because chronically sun-exposed skin is known to have altered immune responsiveness and a statistical predisposition to skin cancer, we then examined UV induction of these genes in cultured keratinocytes derived from habitually sun-exposed adult skin, and for the older donors in paired cultures derived from sun-protected site of the same donors. Aging alone increased the baseline expression of two differentiation-associated genes (SPR2 and IL-1 receptor antagonist) in cultures from sun-protected skin. In contrast, photoaging increased the UV inducibility of c-Sos but decreased the baseline expression of the differentiation-associated genes IL-1 receptor antagonist and SPR2.