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 transcription mediated by activating protein-1 (AP-1). The effects of ethanol on AP-1 activity and on the signaling cascades in this process were investigated 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 activity in SH-SY5Y cells. Shorter exposure periods with ethanol did not influence AP-1 transcriptional activity compared with findings for control cells. Inhibition of protein kinase C (PKC) dramatically decreased AP-1 activity in both control and ethanol-exposed cells and abolished the ethanol enhancement. This finding suggests a pivotal role for PKC-coupled signaling in AP-1 transcriptional activity. Phorbol ester stimulation of AP-1 transcriptional activity was not influenced by long-term ethanol exposure. This finding indicates that signaling events upstream of PKC are the targets for ethanol. Mitogen-activated protein kinases ERK and p38 may play a role in ethanol-enhanced AP-1 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 protein kinases downstream of PKC.

Ethanol exposure potentiates fosB and junB expression induced by muscarinic receptor stimulation in neuroblastoma SH-SY5Y cells.

Muscarinic receptor stimulation and activation of protein kinase C cause an increase in fosB and junB transcripts in human neuroblastoma SH-SY5Y cells. In this study, the effect of long-term ethanol exposure on these events was investigated. Carbachol-stimulated fosB and junB expression was elevated in ethanol-exposed cells compared with control cells. The potentiation was time- and dose-dependent on ethanol. Preincubation with muscarinic antagonists or protein kinase C inhibitor demonstrated that the carbachol-stimulated increase in fosB and junB mRNA levels was primarily mediated via M1 receptors and dependent on the activity of protein kinase C in both control and ethanol-exposed cells. Long-term ethanol exposure did not influence the expression of fosB and junB induced by activation of protein kinase C with phorbol ester. These results demonstrate that the muscarinic receptor-stimulated fosB and junB expression is sensitive to ethanol exposure in SH-SY5Y cells, suggesting that these genes participate in the regulation of neuronal function in response to chronic ethanol treatment.

Acute ethanol exposure attenuates expression of junD in human neuroblastoma cells.

This study describes the effects of acute ethanol exposure on the mRNA levels of c-jun,junB and junD in the human neuroblastoma SH-SY5Y cell line. An acute exposure to 100 mM ethanol did not influence the basal and phorbol ester-induced expression of c-jun and junB, whereas the basal mRNA level of junD was attenuated by 30%. This effect was dose- and time-dependent with maximal inhibition being detected 2 h after 100 mM ethanol treatment and the mRNA levels gradually returned towards normal afterwards. Ethanol also inhibited phorbol ester-induced expression of junD. The fact that ethanol did not influence degradation of the junD mRNA suggests that acute ethanol suppresses the transcription of the gene. These results indicate that acute ethanol exerts different effects on expression of Jun transcription factors, suggesting that as compared to c-jun and junB, the junD gene may be more sensitive to acute ethanol treatment in neuronal cells.