Di(2‐ethylhexyl)phthalate Induces Hepatic Tumorigenesis through a Peroxisome Proliferator‐activated Receptor α‐independent Pathway: Yuki Ito, et al. Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine—Di(2ethylhexyl)phthalate (DEHP), a commonly used industrial plasticizer, causes liver tumorigenesis presumably via activation of peroxisome proliferator‐activated receptor alpha (PPARα). The mechanism of DEHP tumorigenesis has not been fully elucidated, and to clarify whether DEHP tumorigenesis is induced via PPARα, we compared DEHP‐induced tumorigenesis in wild‐type and Pparα‐null mice. Mice of each genotype were divided into three groups, and treated for 22 months with diets containing 0, 0.01 or 0.05% DEHP. Surprisingly, the incidence of liver tumors was higher in Pparα‐null mice exposed to 0.05% DEHP (25.8%) than in similarly exposed wild‐type mice (10.0%). These results suggest the existence of pathways for DEHP‐induced hepatic tumorigenesis that are independent of PPARα. The levels of 8‐OHdG increased dose‐dependently in mice of both genotypes, but the degree of increase was higher in Pparα‐null than in wild‐type mice. NFκB levels also significantly increased in a dose‐dependent manner in Pparα‐null mice. The protooncogene c‐jun‐mRNA was induced, and c‐fos‐mRNA tended to be induced only in Pparα‐null mice fed a 0.05% DEHP‐containing diet. These results suggest that increases in oxidative stress induced by DEHP exposure may lead to the induction of inflammation and/or the expression of protooncogenes, resulting in a high incidence of tumorigenesis in Pparα‐null mice.

Biological Monitoring Method for Urinary Neonicotinoid Insecticides Using LC‐MS/MS and Its Application to Japanese Adults: Jun UEYAMA, et al. Department of Pathophysiological Laboratory Sciences, Field of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine—Objectives: Agricultural use of neonicotinoid (NEO) insecticides has been increasing in recent years, but their biological monitoring methods have been scarcely reported. In this study, we developed and validated a rapid and sensitive method for quantifying urinary NEO concentrations using high‐performance liquid chromatography‐tandem mass spectrometry (LC‐MS/MS).Methods: After phosphate‐induced acidification of a urine sample, urinary NEOs were trapped by a solid‐phase extraction column and eluted with methanol for acetamiprid, imidacloprid, thiacloprid, thiamethoxam, clothianidin and dinotefuran and with an acetonitrile and methanol solution (1:1, v/v) containing 5% NH₃ for nitenpyram. Aseparation analysis was performed by LC‐MS/MS within 10 minutes for the sample. This method was applied to first morning urine obtained from 52 Japanese (40.9 ± 10.5 years old, mean ± standard deviation) without occupational NEO exposure.Results: The linear dynamic ranges and their limit of quantification (LOQ, signal to noise ratio=10) levels were 0.3−20 or 50 μg/l (r=0.998−0.999) and 0.05−0.36 μg/l, respectively. The absolute recovery was 64−95%, and the intra‐ and inter‐day precisions were less than 16.4% (relative standard deviation, %RSD). This method was successfully applied for analysis of NEOs in human urine samples obtained from 52 adults. The frequencies of individuals who showed more than LOD levels was above 90% for imidacloprid, thiamethoxam, clothianidin and dinotefuran, more than 50% for acetamiprid and thiacloprid and 29% for nitenpyram.Conclusions: These results indicated that our new method could be applied to biological monitoring of NEO exposure even at environmental exposure levels in Japanese adults without occupational spraying histories.