Acrolein is a highly electrophilic alpha, beta-unsaturated aldehyde to which humans are exposed in a variety of environmental situations. At low doses, acrolein inhibits cell proliferation without causing cell death and can enhance apoptosis from secondary toxins. The overall goals of this project are to determine the molecular mechanism(s) by which acrolein enhances apoptosis and inhibits proliferation. The hypothesis to be studied is that acrolein enhances apoptosis from secondary stressors including cell-cycle-non-specific anti-cancer drugs and that this is due to changes in genes or transcription factors regulating this process. Since acrolein is a metabolite of cyclophosphamide, this hypothesis leads to the conclusion that the unique effectiveness of this anti-cancer drug is a feature of both acrolein and the phosphoramide mustard metabolite. A related hypothesis is that the acrolein-mediated decrease in cell proliferation is caused by effecting changes in the expression of one or more growth- or stress-related genes or transcription factors secondary to a reduction in GSH which is rapidly depleted following acrolein treatment.
The specific aims of this project to address these hypotheses are: 1) to assess in detail the ability of acrolein to enhance the susceptibility of cells to apoptosis form a secondary pro-apoptotic treatment; and 2) to determine the mechanism of the enhanced apoptosis and decreased proliferation following acrolein treatment. Since acrolein transiently depletes GSH, experiments will be run to differentiate effects directly related to a loss of antioxidant capacity to those related to changes in transcription factors or gene expression (even in those are secondary to the loss of GSH which may allow secondary agents better access to molecular targets). Preliminary data have implicated NF-kappaB as a target for acrolein. This will be further studied by determining the ability of diethyl maleate (DEM) (which blocks NF-kappaB activation at doses that do not deplete GSH) to affect apoptosis and by examining the effects of acrolein on NF-kappaB activation at doses that do not deplete GSH) to affect apoptosis and by examining the effects of acrolein on NF-kappaB and apoptosis in a second cell line. A role for other selected genes in the effects of acrolein will be determined. Specifically, the activation of AP-1 will be measured as well as any changes in mRNA levels and protein products of p53, c-jun, c-fos, c-myc, bcl-2, bcl-x, and bax at various times following acrolein insult. The results of these studies will provide important new information on pathways regulating cell proliferation and apoptosis, as well as provide data on the risk associated with low-level exposure to reactive species such as acrolein.
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