Chronic ethanol exposure enhances activating protein-1 transcriptional activity in human neuroblastoma cells

This study demonstrates a method for studying the effects of ethanol on tra nscription mediated by activating protein-1 (AP-1). The effects of ethanol on AP-1 activity and on the signaling cascades in this process were investi gated by using a reporter gene technique with secreted alkaline phosphatase as the reporter gene coupled to nine DNA AP-1-binding elements. Long-term ethanol exposure (48-72 h) dose dependently enhanced AP-1 transcriptional a ctivity in SH-SY5Y cells. Shorter exposure periods with ethanol did not inf luence AP-1 transcriptional activity compared with findings for control cel ls. Inhibition of protein kinase C (PKC) dramatically decreased AP-1 activi ty in both control and ethanol-exposed cells and abolished the ethanol enha ncement. This finding suggests a pivotal role for PKC-coupled signaling in AP-1 transcriptional activity. Phorbol ester stimulation of AP-1 transcript ional activity was not influenced by long-term ethanol exposure. This findi ng indicates that signaling events upstream of PKC are the targets for etha nol. Mitogen-activated protein kinases ERK and p38 may play a role in ethan ol-enhanced AP-I activity because inhibitors of both enzymes partly reduced the enhancement. The inhibitors also partly blocked phorbol ester-induced AP-1 activation, which demonstrates a function of these mitogen-activated p rotein kinases downstream of PKC. (C) 2001 Elsevier Science Inc. All rights reserved.