Factors Influencing the Yield of Mutations Induced by Polycyclic Aromatic Hydrocarbons in Mammalian Cells

Abstract: Environmental contaminants are ubiquitously present in the urban environment, this has the implication that humans are exposed to toxic and carcinogenic chemicals. Polycyclic aromatic hydrocarbons (PAH) are one type of environmental contaminants, which are produced by combustion of organic compounds. A wide variety of different PAH areformed of which most need metabolic activation to be transformed into the ultimate carcinogenic metabolite, a reactive diol epoxide (PAH-DE) that binds to DNA. PAH induced DNA damage is occasionally removed by different repair processes.This thesis focuses on four PAH-DE(benzo(a)pyrene-diol-epoxide (BPDE), dibenzo(a,l)pyrene-diol-epoxide (DBPDE), dibenzo(a,h)-anthracene-diol-epoxide (DBADE) and benzo(c)phenanthrene-diol-epoxide (BPhDE)) and the role of repair of the induced adducts and their efficiency to induce mutations. The highest level of adducts per µMh was found for the two PAH-DE with fjord region conformation (DBPDE and BPhDE). The highest mutation frequency was exerted by DBPDE followed by BPDE, DBADE and BPhDE explained by differences in both nucleotide excision repair (NER) and replication fidelity. When investigating the repair efficiencies and the effect on replication fork (RF) progression we found that NER enhanced the RF progression whereas HR delayed this process. Inhibition of translesion synthesis was found to delay the RF progression in both wild-type, NER and HR deficient cells. BPDE-induced adducts were most efficiently repaired by NER, whereas DBPDE adducts were not repaired. Antioxidants were tested against PAH-DE mutagenicity and their effects were not dependent on the fjord or bay region structures but on some other property of in the individual compounds.All together, the results indicate that it is not possible to categorize the mutagenic potency of PAH-DE according to common structural features (bay/fjord), why these compounds need to be evaluated individually.