Bcl-2 overexpression in the HaCaT cell line is associated with a different membrane fatty acid composition and sensitivity to oxidative stress.
Different mechanisms have been proposed for the activity of the Bcl-2 proto-oncogene product. A bona fide antioxidant activity and a pro-oxidant setting up of the cell have been suggested using different experimental models, yet many uncertainties exist about the biochemical mechanism of Bcl-2 action. In the present paper, we report the characterization of the cellular response to mild oxidative stress of a cultured cell line of immortalized keratinocytes (HaCaT), overexpressing the Bcl-2 oncogene product. A sublethal oxidative stress was induced by 1 h treatment with 200 microM tert-butyl-hydroperoxide (t-BOOH). Following peroxide treatment, the formation of reactive oxygen species was lower in Bcl-2 expressing cells, suggesting a better capacity to counter oxidative stress. Total Superoxide Dismutase activity was induced by oxidative t-BOOH treatment in bcl-2 transfected cells, which also accumulated less damage to membrane lipids and proteins, as assessed by TBA-RS and carbonyl formation respectively. On the other hand, the formation of 4-hydroxy-nonenal, a more specific marker of peroxidative damage to polyunsaturated fatty acids, was higher in bcl-2 transfected cells than in control cells. Bcl-2 over-expression was also associated with significant changes in the fatty acid composition of cell membranes. Transfected cells presented a higher proportion of mono-unsaturated fatty acids and omega6 poly unsaturated fatty acids and a lower proportion of penta-enoic PUFA, thus resulting in a higher unsaturation index with respect to control cells. Changes in protein kinase C activity were also associated to bcl-2 expression, possibly resulting from the differences in membrane fatty acid composition. These data may be an important background for the understanding of Bcl-2 involvement in the control of apoptotic response as well as in the induction of antioxidant cell defenses against oxidative stress.
Virgili
F
F
Instituto Nazionale della Nutrizione, Rome, Italy.
Santini
M P
MP
Canali
R
R
Polakowska
R R
RR
Haake
A
A
Perozzi
G
G
D000975:Antioxidants / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D005227:Fatty Acids / Q000032:analysis*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D008563:Membrane Lipids / Q000032:analysis*; D018384:Oxidative Stress / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D005227:Fatty Acids; C000715470:MAS1 protein, human; D008563:Membrane Lipids; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D011493:Protein Kinase C