Contamination with retinoic acid receptor agonists in two rivers in the Kinki region of Japan

Abstract

RARa agonistic activityRiver Surface water Yeast two-hybrid assay a b s t r a c t This study was conducted to investigate the agonistic activity against human retinoic acid receptor (RAR) a in the Lake Biwa-Yodo River and the Ina River in the Kinki region of Japan.To accomplish this, a yeast two-hybrid assay was used to elucidate the spatial and temporal variations and potential sources of RARa agonist contamination in the river basins. RARa agonistic activity was commonly detected in the surface water samples collected along two rivers at different periods, with maximum all-trans retinoic acid (atRA) equivalents of 47.6 ng-atRA/L and 23.5 ng-atRA/L being observed in Lake Biwa-Yodo River and Ina River, respectively. The results indicated that RARa agonists are always present and widespread in the rivers. Comparative investigation of RARa and estrogen receptor a agonistic activities at 20 stations along each river revealed that the spatial variation pattern of RARa agonist contamination was entirely different from that of the estrogenic compound contamination.This suggests that the effluent from municipal wastewater treatment plants, a primary source of estrogenic compounds, seemed not to be the cause of RARa agonist contamination in the rivers. Fractionation using high performance liquid chromatography (HPLC) directed by the bioassay found two bioactive fractions from river water samples, suggesting the presence of at least two RARa agonists in the rivers. Although a trial conducted to identify RARa agonists in the major bioactive fraction was not completed as part of this study, comparison of retention times in HPLC analysis and quantification with liquid chromatography-mass spectrometry analysis revealed that the major causative contaminants responsible for the RARa agonistic activity were not RAs (natural RAR ligands) and 4-oxoRAs, while 4-oxo-RAs were identified as the major RAR agonists in sewage in Beijing, China.These findings suggest that there are unknown RARa agonists with high activity in the rivers. A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s w a t e r r e s e a r c h 4 4 ( 2 0 1 0 ) 2 4 0 9 -2 4 1 80043-1354/$ -see front matter ª

Disruption of Retinoic Acid Receptor Signaling by Environmental Pollutants

“…Our recent studies in 4 rivers in the Kinki region and in several WWTPs in Osaka and Toyama Prefectures detected statistically significant RARα agonistic activity commonly in surface waters in all of the investigated rivers 56,57) and influents and effluents from the WWTPs. 58,59) River water pollution by RAR agonists occurs irrespective of the pollution level of the rivers, and surprisingly even in the upstream suburban areas with little human activity.…”

“…58,59) River water pollution by RAR agonists occurs irrespective of the pollution level of the rivers, and surprisingly even in the upstream suburban areas with little human activity. 56,57) In addition, strong RARα agonistic activity unaccountable by the activity of WWTP effluents was detected in river water samples. 56,57,59) Therefore, WWTPs do not seem to be the major source of RAR agonists in our study areas in Japan, which is different from the RAR agonist pollution found in Beijing, China as described above.…”

“…56,57) In addition, strong RARα agonistic activity unaccountable by the activity of WWTP effluents was detected in river water samples. 56,57,59) Therefore, WWTPs do not seem to be the major source of RAR agonists in our study areas in Japan, which is different from the RAR agonist pollution found in Beijing, China as described above. Also, simultaneous investigation of the agonistic activities at RARα and estrogen receptor α suggests that the variation along the watercourse of RAR agonist pollution in Japanese rivers is completely dissimilar to that of the estrogenic contamination, a widely known EDCs problem.…”

“…Also, simultaneous investigation of the agonistic activities at RARα and estrogen receptor α suggests that the variation along the watercourse of RAR agonist pollution in Japanese rivers is completely dissimilar to that of the estrogenic contamination, a widely known EDCs problem. 56,57) Although the RAR agonists present in aquatic samples in Japan are not yet identified (Table 3), the river pollution level in the Kinki region of Japan appears to be greater than that in Beijing, China. 40,57) However, the maximal atRA-EQ in river water was estimated to be 47.6 ng/l, 57) which was more than 10-fold lower than the atRA level leading to the abnormal morphological developments in vertebrates (Table 1).…”

“…56,57) Although the RAR agonists present in aquatic samples in Japan are not yet identified (Table 3), the river pollution level in the Kinki region of Japan appears to be greater than that in Beijing, China. 40,57) However, the maximal atRA-EQ in river water was estimated to be 47.6 ng/l, 57) which was more than 10-fold lower than the atRA level leading to the abnormal morphological developments in vertebrates (Table 1). Therefore, the level of RAR agonist pollution is not likely to cause RAR-mediated deleterious biological effects at present.…”