Possible involvement of oxidative stress in piperonyl butoxide induced hepatocarcinogenesis in rats

• DOI: 10.1016/j.tox.2007.03.025
• Publication Date: 2007-04-07T11:17:04Z
• Authors: Masako Muguruma; Akira Unami; Masayuki Kanki; Yuichi Kuroiwa; Jihei Nishimura; Yasuaki Dewa; Takashi Umemura; Yuji Oishi; Kunitoshi Mitsumori
• Keywords: Male; 0301 basic medicine; Deoxyadenosines; Piperonyl Butoxide; Reverse Transcriptase Polymerase Chain Reaction; Gene Expression Profiling; Pesticide Synergists; Gene Expression; DNA; Rats, Inbred F344; Rats; Oxidative Stress; 03 medical and health sciences; Liver Neoplasms, Experimental; Liver; Microsomes, Liver; Animals; RNA, Messenger; Reactive Oxygen Species; Oligonucleotide Array Sequence Analysis

To clarify the possible mechanism of non-genotoxic hepatocarcinogenesis induced by piperonyl butoxide (PBO), male F344 rats were administered an i.p. injection of N-diethylnitrosamine (DEN) to initiate hepatocarcinogenesis. Two weeks later, the rats were administered a PBO-containing (0, 1, or 2%) diet for 6 weeks and subjected to a two-third partial hepatectomy 1 week later. After sacrificing them on week 8, their livers were histopathologically examined and analyzed for gene expression using a microarray and real-time RT-PCR. Reactive oxygen species (ROS) products were also measured using liver microsomes. Hepatocytes exhibited centrilobular hypertrophy and increased glutathione S-transferase placental form (GST-P) positive foci formation. ROS products increased significantly in liver microsomes. In the microarray analysis, the expressions of genes related to metabolism and oxidative stress - NAD(P)H dehydrogenase, quinone 1 (Nqo1), UDP-glucuronosyltransferase (UDPGTR-2), glutathione peroxidase 2 (Gpx2), glutathione reductase (GRx) - multidrug resistance associated protein 3 (Abcc3), and solute carrier family 7 (cationic amino acid transporter, y+ system) member 5 (Slc7a5) were up-regulated in the PBO group in comparison to the 0% PBO group; this was confirmed by real-time RT-PCR. Additionally, a significant up-regulation of stress response related genes such as CYP1A1 was observed in PBO-treated groups in real-time RT-PCR. HPLC analysis revealed that the level of 8-OHdG in the 2% PBO group was significantly higher than that in the 0% PBO group. This suggests that PBO has the potential to generate ROS via metabolic pathways and induce oxidative stress, including oxidative DNA damage, resulting in the induction of hepatocellular tumors in rats.