Formation of 8-hydroxydeoxyguanosine and cell-cycle arrest in the rat liver via generation of oxidative stress by phenobarbital: association with expression profiles of p21(WAF1/Cip1), cyclin D1 and Ogg1.

Abstract

To evaluate the risk of exposure to so-called non-genotoxic chemicals and elucidate mechanisms underlying their promoting activity on rat liver carcinogenesis the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG), cytochrome P-450 (P-450) and hydroxyl radicals induction, DNA repair and alteration to cellular proliferation and apoptosis in the rat liver were investigated during 2 weeks of phenobarbital (PB) administration at a dose of 0.05%. Significant increase of hydroxyl radical levels by day 4 of PB exposure accompanied the accumulation of 8-OHdG in the nucleus and P-450 isoenzymes CYP2B1/2 and CYP3A2 in the cytoplasm of hepatocytes. Conspicuous elevation of 8-OHdG and apoptosis in the liver tissue were associated with reduction of the proliferating cell nuclear antigen (PCNA) index after 8 days of PB application. Thereafter, 8-OHdG levels decreased with an increase in mRNA expression for the 8-OHdG repair enzyme, DNA glycosylase 1 (Ogg1). Analysis with LightCycler quantitative 2-step RT-PCR demonstrated induction of cyclin D1 (CD1) and p21(WAF1/Cip1) mRNA expression on days 4 and 6, respectively, preceding marked elevation of PCNA and apoptotic indices. These results suggest that similar to genotoxic, non-genotoxic chemicals might induce reversible alteration to nuclear 8-OHdG in the rat liver after several days of continuous application; however, by a different mechanism. Increased 8-OHdG formation is caused by developing oxidative stress or apoptotic degradation of DNA and coordinated with enhanced expression of CD1 mRNA and cell proliferation, subsequent increase of p21(WAF1/Cip1) mRNA expression, cell-cycle arrest and apoptosis, while activation of 8-OHdG repair mechanisms contributes to protection of tissue against reactive oxygen species-induced cell death.

• Authors: Anna Kinoshita, Hideki Wanibuchi, Susumu Imaoka, Motome Ogawa, Chikayoshi Masuda, Keiichirou Morimura, Yoshihiko Funae, Shoji Fukushima
• Journal: Carcinogenesis (Carcinogenesis) Vol. 23 Issue 2 Pg. 341-9 (Feb 2002) ISSN: 0143-3334 [Print] England
• PMID: 11872643 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Carcinogens
• Cdkn1a protein, rat
• Cyclin-Dependent Kinase Inhibitor p21
• Cyclins
• DNA, Single-Stranded
• Excitatory Amino Acid Antagonists
• RNA, Messenger
• Cyclin D1
• Hydroxyl Radical
• 8-Hydroxy-2'-Deoxyguanosine
• Cytochrome P-450 Enzyme System
• Steroid Hydroxylases
• Aryl Hydrocarbon Hydroxylases
• Cytochrome P-450 CYP2B1
• steroid 16-beta-hydroxylase
• steroid hormone 6-beta-hydroxylase
• N-Glycosyl Hydrolases
• DNA-Formamidopyrimidine Glycosylase
• Deoxyguanosine
• Phenobarbital

Topics

• 8-Hydroxy-2'-Deoxyguanosine
• Animals
• Apoptosis
• Aryl Hydrocarbon Hydroxylases
• Carcinogens
• Cell Cycle
• Cell Division
• Cell Nucleus (drug effects, enzymology)
• Cyclin D1 (biosynthesis)
• Cyclin-Dependent Kinase Inhibitor p21
• Cyclins (biosynthesis)
• Cytochrome P-450 CYP2B1 (biosynthesis)
• Cytochrome P-450 Enzyme System (biosynthesis)
• Cytoplasm (drug effects, enzymology)
• DNA Damage
• DNA Repair
• DNA, Single-Stranded (metabolism)
• DNA-Formamidopyrimidine Glycosylase
• Deoxyguanosine (analogs & derivatives, chemistry)
• Dose-Response Relationship, Drug
• Excitatory Amino Acid Antagonists (pharmacology)
• Hepatocytes (drug effects, enzymology)
• Hydroxyl Radical
• Immunohistochemistry
• Liver (drug effects, physiology)
• Male
• Microsomes, Liver (drug effects, enzymology)
• N-Glycosyl Hydrolases (biosynthesis)
• Oligonucleotide Array Sequence Analysis
• Oxidative Stress
• Phenobarbital
• RNA, Messenger (metabolism)
• Rats
• Rats, Inbred F344
• Reverse Transcriptase Polymerase Chain Reaction
• Steroid Hydroxylases (biosynthesis)
• Time Factors