Primary and secondary pyrrolic metabolites of pyrrolizidine alkaloids form DNA adducts in human A549 cells. (February 2019)

• Record Type: Journal Article
• Authors: He, Xiaobo; Xia, Qingsu; Wu, Qiangen; Tolleson, William H.; Lin, Ge; Fu, Peter P.
• Is Part Of: Toxicology in vitro. Volume 54(2019)
• Page Start: 286
• Page End: 294
• Publication Date: 2019-02
• Subjects: Pyrrolizidine alkaloid -- DHP -- 7-GS-DHP -- 7-Cysteine-DHP -- DNA adducts; DHR dehydroretronecine or (-)-R-6, 7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine -- DHP (+/-)-6, 7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine -- 7-GS-DHP 7-glutathione-DHP -- 7, 9-di-GS-DHP 7, 9-diglutathione-DHP -- dG 2′-deoxyguanosine -- dA 2′-deoxyadenosine -- DHP-dG-1 and DHP-dG-2 a pair of epimers of 7-(deoxyguanosin-N2-yl)dehydrosupinidine adducts -- DHP-dG-3 and DHP-dG-4 a pair of epimers of 7-hydroxy-9-(deoxyguanosin-N2-yl)dehydrosupinidine adducts -- DHP-dA-1 and DHP-dA-2 a pair of epimers of 7-(deoxyadenosin-N6-yl)dehydrosupinidine adducts -- DHP-dA-3 and DHP-dA-4 a pair of epimers of 7-hydroxy-9-(deoxyadenosin-N6-yl)dehydrosupinidine adducts -- LC-ES-MS/MS high-performance liquid chromatography electrospray ionization tandem mass spectrometry -- SRM selected reaction monitoring -- LOD limit of detection -- NCTR National Center for Toxicological Research; Toxicity testing -- In vitro -- Periodicals; Toxicology -- Periodicals; 615.9
• DOI: 10.1016/j.tiv.2018.10.009
• Languages: English
• ISSNs: 0887-2333

Abstract

Abstract: Humans and animals can be exposed to carcinogenic pyrrolizidine alkaloids (PAs) through consumption of plants commonly found in many parts of the world. Although the liver is the primary target organ for carcinogenic PAs, they have also induced lung tumors in rodents. Hepatic cytochrome P450 activity converts PAs into dehydro-PAs that can be hydrolyzed to dehydropyrrolizidine (DHP); these reactive pyrrolic metabolites can produce four characteristic DNA adducts associated with PA-induced liver tumor initiation in laboratory animals. We reported recently that these four DNA adducts are also formed when 7-glutathione-DHP (7-GS-DHP) or 7-cysteine-DHP is incubated with calf thymus DNA. Here we showed that the four characteristic DNA adducts were formed when human A549 brochoalveolar carcinoma cells were treated with three dehydro-PAs (dehydroriddelliine, dehydromonocrotaline, or dehydroretronecine) or with 7-GS-DHP or 7-cysteine-DHP. For comparison, two parent PAs (riddelliine and monocrotaline) and 7, 9-di-glutathionine-DHP were studied. No DHP-DNA adducts were detected with these incubations, confirming that A549 lung carcinoma cells do not express cytochrome P450 enzymes required for metabolic activation of PAs. Our results show that primary and secondary pyrrolic metabolites of carcinogenic PAs produce characteristic DHP-containing DNA adducts in A549 lung cancer cells, suggesting that they are DNA reactive metabolites. Highlights: Carcinogenic pyrrolizidine alkaloids (PAs) induce liver and lung tumors in rats. Metabolism of PA generates primary and secondary pyrrolic metabolites in the liver. These reactive pyrrolic metabolites can form DNA adducts in A549 human lung cells. These metabolites include dehydro-PAs, DHP, 7-glutathione-DHP, and 7-cysteine-DHP. The DNA adducts formed in A549 are DHP-dG-3, DHP-dG-4, DHP-dA-3, and DHP-dA-4.