THE ROLE OF OXYGEN-METABOLISM FOR THE PATHOLOGICAL PHENOTYPE OF FANCONI-ANEMIA

The molecular defect of the hereditary disease Fanconi anemia (FA) rem ains unknown. The two theoretical possibilities are (1) an impaired DN A crosslink-repair system or (2) a disturbed oxygen metabolism either by overproduction of reactive oxygen intermediates (ROI) or by diminis hed detoxification of ROI. In order to gain further insight into the m olecular mechanism of this disease, we have determined the repair capa city of FA cells challenged by crosslinking agents and have analyzed d iverse biological systems that are involved in oxygen metabolism. We h ave tested normal and FA cells for oxygen consumption and for the acti vity of the antioxidant phospholipid-hydroperoxide-glutathione-peroxid ase (PHGPx). FA cells show a reduced oxygen consumption and an increas ed PHGPx activity. Since spontaneous and induced chromosomal instabili ty is a main cellular feature of FA, we have analyzed the redox state of cells and the effect of cytochrome P-450 (Cyt P-450) inhibitors and inducers on chromosomal breaks and micronuclei production. Our result s indicate that Cyt P-450 enzymes, especially Cyt P450 1A2, play a cru cial role in radical metabolism in FA cells. Furthermore, we have dete rmined NF-kappa B activity in untransformed cells and in SV40-transfor med cells by gel shift experiments. NF-kappa B is a multiunit transcri ption factor that is known to be induced by ROI and that activates the expression of various genes involved in cellular responses to stress. NF-kappa B is constitutively induced in SV40-transformed FA cells pro bably as a consequence of an increased ROI level. Our results suggest that enzymatic defects in oxygen metabolism mediate the FA phenotype v ia impaired reactivity with ROI. Cyt P-450 1A2 appears to be a good ca ndidate for the defective enzyme, even though no differences have been measured in the activity of this enzyme in FA and control fibroblasts in pilot experiments.