Liver tumor promoting effect of orphenadrine in rats and its possible mechanism of action including CAR activation and oxidative stress.

Abstract

Orphenadrine (ORPH), an anticholinergic agent, is a cytochrome P450 (CYP) 2B inducer. CYP2B inducers are known to have liver tumor-promoting effects in rats. In this study, we performed a rat two-stage liver carcinogenesis bioassay to examine the tumor-promoting effect of ORPH and to clarify its possible mechanism of action. Male rats were given a single intraperitoneal injection of N-diethylnitrosamine (DEN) as an initiation treatment. Two weeks after DEN administration, rats were fed a diet containing ORPH (0, 750, or 1,500 ppm) for 6 weeks. One week after the ORPH-administration rats were subjected to two-thirds partial hepatectomy for the acceleration of hepatocellular proliferation. The number and area of glutathione S-transferase placental form-positive foci significantly increased in the DEN-ORPH groups. Real-time RT-PCR revealed increased mRNA expression levels of Cyp2b1/2, Mrp2 and Cyclin D1 in the DEN-ORPH groups and of Gpx2 and Gstm3 in the DEN-High ORPH group. Microsomal reactive oxygen species (ROS) production and oxidative stress markers such as thiobarbituric acid-reactive substances and 8-hydroxydeoxyguanosine were increased in the DEN-High ORPH group. Immunohistochemically, constitutively active/androstane receptor (CAR) were clearly localized in the nuclei of hepatocytes in the DEN-ORPH groups. These results suggest that ORPH causes nuclear translocation of CAR resulting in the induction of the liver tumor-promoting activity. Furthermore, oxidative stress resulting from ROS production is also involved in the liver tumor-promoting activity of ORPH.

• Authors: Reiko Morita, Atsunori Yafune, Ayako Shiraki, Megu Itahashi, Yuji Ishii, Hirotoshi Akane, Fumiyuki Nakane, Kazuhiko Suzuki, Makoto Shibutani, Kunitoshi Mitsumori
• Journal: The Journal of toxicological sciences (J Toxicol Sci) Vol. 38 Issue 3 Pg. 403-13 ( 2013) ISSN: 1880-3989 [Electronic] Japan
• PMID: 23665939 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cholinergic Antagonists
• Constitutive Androstane Receptor
• Muscarinic Antagonists
• Reactive Oxygen Species
• Receptors, Cytoplasmic and Nuclear
• Diethylnitrosamine
• Orphenadrine

Topics

• Animals
• Cell Nucleus (metabolism)
• Cholinergic Antagonists (administration & dosage, toxicity)
• Constitutive Androstane Receptor
• Diethylnitrosamine (administration & dosage, toxicity)
• Hepatocytes (cytology, metabolism)
• Liver Neoplasms (chemically induced)
• Male
• Muscarinic Antagonists (administration & dosage, toxicity)
• Orphenadrine (administration & dosage, toxicity)
• Oxidative Stress (drug effects)
• Rats
• Rats, Inbred F344
• Reactive Oxygen Species (metabolism)
• Receptors, Cytoplasmic and Nuclear (metabolism)