Abstract
Acrolein, which is a highly reactive formaldehyde generated by lipid peroxidation, can affect skin and cause various disorders. The effect of exposure of human keratinocytes to acrolein on cell surface‐oriented signal transduction into cells was examined. Incubation of human keratinocytes with a relatively low concentration (50 μM) of acrolein caused a prompt and selective induction of tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) as a 180‐kDa molecule during the period from 5–30 min after the start of incubation. This early event was followed by an increase in the density and number of phosphotyrosine‐containing proteins during the period from 60–120 min after the start of incubation. The catalytic activity of EGFR as measured by the levels of autophorphorylation and phosphorylation of an exogenously added substrate, casein, in in vitro kinase assay, greatly increased as early as 1 min after the start of incubation and then decreased gradually 30 min later. MAP family kinases, including ERK, JNK, and p38 kinase, and the potentially downstream transcription factor c‐Jun were all promoted for phosphorylation/activation during a period of 5–30 min. Selective prompt phosphorylation/activation of EGFR followed by phosphorylation of MAP family kinases and c‐Jun and their blockade by a specific EGFR inhibitor, AG1478, suggested that activation of EGFR is the major, and possibly single, cell surface element for intracellular signal transduction in acrolein‐treated cells. Incubation of human keratinocytes with 50 μM of acrolein induced atypical apoptosis with morphologic apoptotic features with low‐grade oligonucleoside‐sized DNA fragmentation. Partial inhibition of such a cytopathic effect of acrolein on human keratinocytes by preincubation with AG1478 suggests the involvement of an EGFR‐mediated signal pathway for atypical apoptosis. These results provide new information on acrolein‐induced cell surface‐oriented signal transduction to human keratinocytes, and this information may be useful for understanding the pathogenesis of a number of skin diseases in response to environmental acrolein and acrolein‐generating ultraviolet irradiation. J. Cell. Biochem. 81: 679–688, 2001. © 2001 Wiley‐Liss, Inc.