title: Elevation of cell proliferation via generation of reactive oxygen species by piperonyl butoxide contributes to its liver tumor-promoting effects in mice.
abstract: Piperonyl butoxide (PBO) is a pesticide synergist used with pyrethroids as a domestic insecticide, and it acts as a non-genotoxic hepatocarcinogen in rats and mice. To clarify whether oxidative stress is involved in the liver tumor-promoting effect of PBO in mice, male mice were subjected to two-thirds partial hepatectomy, followed by N-diethylnitrosamine (DEN) treatment, and given a diet containing 0.6% PBO for 25 weeks. The incidences of cytokeratin (CK) 8/18-positive foci, adenomas, and carcinomas significantly increased in the DEN + PBO group compared with the DEN-alone group. The PCNA-positive ratio significantly increased in non-tumor hepatocytes, CK8/18-positive foci and adenomas in the DEN + PBO group compared with the DEN-alone group. PBO increased reactive oxygen species (ROS) production in microsomes but did not change oxidative DNA damage as assessed by 8-hydroxydeoxyguanosine (8-OHdG). In real-time RT-PCR, PBO upregulated the expression of genes related to metabolism, such as Cytochrome P450 1a1, 2a5, and 2b10, and metabolic stress, such as Por and Nqo1, but downregulated Egfr and Ogg1. PBO also increased early response genes downstream of mitogen-activated protein kinase (MAPK), such as c-Myc that is induced by excessive ROS production, and G1/S transition-related genes, such as E2f1 and Ccnd1. Thus, PBO can generate ROS via the metabolic pathway without any induction of oxidative DNA damage, activate cell growth, increase c-Myc- and E2F1-related pathways, and act as a liver tumor promoter of DEN-induced hepatocarcinogenesis in mice.
authors.affiliation: Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan.
authors.forename: Masaomi
authors.initials: M
authors.lastname: Kawai
authors.forename: Yukie
authors.initials: Y
authors.lastname: Saegusa
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Dewa
authors.forename: Jihei
authors.initials: J
authors.lastname: Nishimura
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kemmochi
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Harada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ishii
authors.forename: Takashi
authors.initials: T
authors.lastname: Umemura
authors.forename: Makoto
authors.initials: M
authors.lastname: Shibutani
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Mitsumori
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D007150:Immunohistochemistry; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced* / Q000378:metabolism; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D010574:Pesticide Synergists / Q000494:pharmacology*; D010882:Piperonyl Butoxide / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D010574:Pesticide Synergists; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D010882:Piperonyl Butoxide