Orally administered nicotine effects on rat urinary bladder proliferation and carcinogenesis. (1st April 2018)

• Record Type: Journal Article
• Authors: Suzuki, Shugo; Cohen, Samuel M.; Arnold, Lora L.; Kato, Hiroyuki; Fuji, Satoshi; Pennington, Karen L.; Nagayasu, Yuko; Naiki-Ito, Aya; Yamashita, Yoriko; Takahashi, Satoru
• Is Part Of: Toxicology. Volume 389/399(2018)
• Page Start: 31
• Page End: 40
• Publication Date: 2018-04-01
• Subjects: Nicotine -- Urinary bladder carcinogenesis -- N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) -- Nicotinic acetylcholine receptor -- Rat; Toxicology -- Periodicals; Chemicals -- Physiological effect -- Periodicals; 615.9005
• DOI: 10.1016/j.tox.2018.02.008
• Languages: English
• ISSNs: 0300-483X

Abstract

Highlights: Nicotine induced urothelial cytotoxicity with regenerative proliferation. Nicotine promoted BBN-induced rat urothelial carcinogenesis. nAChR inhibitors inhibited proliferation and simple hyperplasia induced by nicotine. nAChR inhibitors didn't inhibit cytotoxicity of nicotine. The cytotoxic concentration of nicotine was > 1 mM in vitro . Abstract: Tobacco smoking is a major risk factor for human cancers including urinary bladder carcinoma. Cigarette smoke inhalation in mice and orally administered nicotine in rats and mice increased urothelial cell proliferation. Nicotine, a major component of smoke, induced cell proliferation in multiple cell types in vitro . In the present study, the enhancing effects of nicotine on F344 rat bladder carcinogenesis induced by N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) were examined. Nicotine administered in drinking water for 32 weeks following 4 weeks of BBN treatment significantly increased the incidence and number of urothelial carcinomas dose-dependently. Ki67 and pSTAT3 labeling indices and expression of nicotinic acetylcholine receptor alpha 7 (nAChRα7) in non-tumor bladder urothelial lesions were significantly increased by nicotine, but the TUNEL assay for apoptosis showed no increase. In a 4 week study, inhibitors of nicotinic acetylcholine receptor decreased nicotine-induced urothelial simple hyperplasia and Ki67 labeling index in the bladder and kidney pelvis at a single cytotoxic dose of nicotine (40 ppm). Urothelial cytotoxicity with regenerative proliferation was observed by light and scanning electron microscopy. In vitro, nicotine was not cytotoxic to rat or human immortalized urothelial cells (do not express nicotine receptors) below millimolar concentrations, nor in human RT4, T24 or UMUC3 urothelial carcinoma cells (express nicotine receptors). However, nicotine slightly, but statistically significantly, increased cell proliferation at micromolar concentrations in human urothelial carcinoma cells. These data suggest that nicotine enhances urinary bladder carcinogenesis by inducing cytotoxicity with regenerative proliferation. The possible role of direct mitogenesis, involving nAChR and STAT3 signaling and of nicotine receptors requires further investigation at non-cytotoxic doses of nicotine.