Nagayama J

Determination of polychlorinated dibenzofurans in tissues of patients with 'yusho'.

Abstract Tissues of patients with ‘Yusho’ and of persons not suffering from this disease were analysed for polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs) by column chromatography, gas chromatography, and gas chromatography-mass spectrometry. Both PCBs and PCDFs were identified in the tissues of patients with Yusho, while only PCBs were detected in the tissues of the other persons studied. In contrast to the PCBs, which were found far more in the adipose tissue than in the liver, PCDFs occurred in very similar concentrations in these two types of tissue. The persisting PCDFs in the tissues of Yusho patients were almost exclusively penta and hexachloro derivatives.

A comparative study of polychlorinated dibenzofurans, polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin on aryl hydrocarbon hydroxylase inducing potency in rats

The aryl hydrocarbon hydroxylase (AHH) inducing potency of toxic chlorinated aromatic hydrocarbons such as polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied in the young male Wistar rats. Alternatively, a technical PCDF mixture, 15 individual PCDF isomers or TCDD were administered i.p. in doses of 5 μg/kg; a PCB mixture was given in a dose of 50 mg/kg. The order of AHH inducing ability was TCDD > PCDFs ≫ PCBs in kidney, lung, and liver. In the prostate, thymus, and spleen, only TCDD enhanced the AHH activity. The AHH inducibility in the lung and liver, induced by 15 pure PCDF isomers with varying chlorine substitutions was also examined. Only 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-tetra-CDF) and 2,3,4,7,8-pentachlorodibenzofurans (2,3,4,7,8-penta-CDF) significantly induced the hepatic AHH activity (4- and 2-fold, respectively), while eight PCDF isomers, including these two, significantly enhanced the pulmonary AHH activity (6- to 30-fold). Taking into account both the potent AHH inducibility and the high bioaccumulation of these compounds, 2,3,7,8-tetra- and 2,3,4,7,8-penta-CDF should be given due attention with regard to environmental-related factors and the possibility of involvement in the etiology of “Yusho” disease.

Transfer of polychlorinated dibenzofurans to the foetuses and offspring of mice.

Abstract A diet containing 0·6 ppm of a mixture of polychlorinated dibenzofurans (PCDFs) having 4, 5 or 6 chlorine atoms was fed to mice for 18 days after mating or for 14 days after delivery. Dams, foetuses and offspring were analysed for PCDFs by gas chromatography. PCDFs were transferred to the foetuses across the placenta and to the offspring through milk. The amounts of PCDFs transferred through milk were much larger than the amounts transferred across the placenta. A greater level of PCDFs was accumulated in the livers of the dams than in other tissues. There were differences between the PCDFs in their levels of accumulation in the tissues of the mice.

Genetically mediated induction of aryl hydrocarbon hydroxylase activity in human lymphoblastoid cells by polychlorinated dibenzofuran isomers and 2,3,7,8-tetrachlorodibenzo-p-dioxin

Aryl hydrocarbon hydroxylase(AHH)-inducing potency of toxic polychlorinated aromatic hydrocarbons such as polychlorinated dibenzofuran (PCDF) isomers, 3,4,5,3′,4′,5′-hexachlorobiphenyl (HCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated in human lymphoblastoid cell lines with different AHH inducibility for 3-methylcholanthrene (3-MC) obtained from healthy subjects. Each of the cell lines was treated with eitht individual PCDF isomers, TCDD, and HCB at doses of 1.9–15 ng/ml of culture medium, 1.9–7.5 ng/ml and 95 ng/ml, respectively. Lymphoblastoid cell lines were arbitrarily classified into three groups based on their AHH inducibilities with 3-MC (2.5 μM); low (3-MC/ control=I<3), middle (3<=I<6) and high (I>=6). Degrees of the enzyme inducibilities of the organochlorine compounds proportionally increased with those for 3-MC. AHH inducibilities with 2,3,4,7,8-pentachlorodibenzofuran(2,3,4,7,8-PCDF), 1,2,3,4,6,7-hexachlorodibenzofuran(1,2,3.4,6,7-HCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran(1,2,3,4,7,8-HCDF) were comparable to those of TCDD at doses of 7.5 ng/ ml, and about twice as high as those of 2,3,7,8-tetrachlorodibenzofuran (TCDF), at the same dose, HCB, at a dose of 95 ng/ ml, did not induce enzyme activity. The experimental evidence indicated that AHH inducibility by the organochlorine compounds reflected the genetic susceptibility of the cells to the phenomenon of induction, and PCDF isomers found at relatively high concentrations in tissues of mammals exerted the highest values of AHH induction.

PCDFs and related compounds in humans from Yusho and Yu-Cheng incidents

Abstract Mass food poisoning incidents, called Yusho and Yu-Cheng, were caused by the ingestion of rice oils which had been contaminated with polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs) and polychlorinated quaterphenyls (PCQs). This paper reviews the formation of toxic PCDFs in the rice oil from PCBs, intakes of PCBs, PCDFs and PCQs by the patients and the behavior of PCBs, PCDFs and PCQs in the human body.

Inducing Potency of Aryl Hydrocarbon Hydroxylase Activity in Human Lymphoblastoid Cells and Mice by Polychlorinated Dibenzofuran Congeners

Aryl hydrocarbon hydroxylase (AHH)-inducing potency of eight polychlorinated dibenzofuran (PCDF) isomers, 3,4,5,3,4,5-hexachlorobiphenyl (HCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxon (TCDD) in two inbred mouse strains (AHH responsive and nonresponsive mouse strains) and eight human lymphoblastoid cell lines (four males and four females) was investigated to evaluate their relative toxic potency. In AHH nonresponsive DBA mouse strain, only TCDD induced hepatic AHH activity at a dose of 30 micrograms/kg, while in AHH responsive C57 mouse strain, six PCDF isomers besides TCDD could enhance the enzyme activity significantly. 2,3,7,8-Tetrachlorodibenzofuran (2,3,7,8-TCDF), 1,2,3,7,8-pentachlorodibenzofuran (1,2,3,7,8-PCDF) and 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PCDF) showed the highest AHH inducing activity among the PCDF isomers tested. In contrast with the results obtained from the mouse experiments, in human lymphoblastoid cells, 2,3,4,7,8-PCDF, 1,2,3,4,6,7-hexachlorodibenzofuran (1,2,3,4,6,7-HCDF) and 1,2,3,7,8-hexachlorodibenzofuran (1,2,3,4,7,8-HCDF) elicited the highest AHH induction and were as potent AHH inducers as TCDD. These observations suggest that toxicities of 2,3,4,7,8-PCDF, 1,2,3,4,6,7-HCDF and 1,2,3,4,7,8-HCDF in human tissues may be comparable to that of TCDD. It was also observed that in both male and female human cell lines, the degree of AHH inducibilities of these compounds were roughly parallel to that of 3-methylcholanthrene, possibly indicating that genetic susceptibility among human population to the toxic compounds are also present similar to those reported among mouse strains.

Polychlorinated dibenzofurans as a causal agent of fetal Yusho.

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) are highly-toxic environmental pollutants that are still ubiquitous. About 40 years ago, a mass food poisoning, termed Yusho, occurred in western Japan, and the causal agent of Yusho was thought to be PCDFs. The preserved umbilical cords of babies who were born to mothers with Yusho 2-5 years after the outbreak of Yusho and diagnosed with fetal Yusho were recently obtained, and the concentrations of PCDDs, PCDFs, dioxin-like PCBs and polychlorinated biphenyls (PCBs) in these preserved umbilical cords were determined. Among babies with fetal Yusho, the pollutant concentrations in umbilical cords were compared between black babies, a term that describes the dermatologic abnormality that is classically seen in fetal Yusho, and non-black babies. There was almost no difference in the concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) toxic equivalents (TEQ) concentrations of PCDDs, PCDFs and dioxin-like PCBs found in these two groups of babies. Therefore, the Yusho infants with the dark brown skin pigmentation seemed to have a hypersensitive genetic predisposition to the production of melanin pigment in the skin after the exposure to these toxic compounds. The concentrations of PCDDs, PCDFs, dioxin-like PCBs and PCBs in the preserved umbilical cords of infants diagnosed with fetal Yusho and of healthy babies were also determined and compared. PCDDs, dioxin-like PCBs and PCBs were detected in both groups. PCDFs, however, were found at high concentration only in the babies with fetal Yusho. In 2,3,7,8-TCDD TEQ concentrations, 90% of the total TEQ concentrations were attributable to PCDFs after taking into account the baseline concentrations found in healthy babies. This evidence shows that fetal Yusho is caused by PCDF intoxication.

Genetically mediated induction of aryl hydrocarbon hydroxylase activity in mice by polychlorinated dibenzofuran isomers and 2,3,7,8-tetrachlorodibenzo-p-dioxin

Hepatic aryl hydrocarbon hydroxylase (AHH)-inducing potency of toxic polychlorinated aromatic hydrocarbons such as polychlorinated dibenzofurans (PCDFs), 3,4,5,3′,4′,5′-hexachlorobiphenyl (HCB) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied in four inbred strains of mice with different phenotypes of Ah locus, i.e., AHH-responsive strains: C57BL/6N and AKR/Ms Qdj, and AHH-nonresponsive strains: DBA/2Cr Slc and Qdj; DDD. Eight individual PCDF isomers or TCDD were administered IP in doses of 30 μg/kg; HCB was given in a dose of 120 μg/kg. In AHH-nonresponsive strains of mice, only TCDD significantly induced hepatic AHH activity, while in AHH-responsive strains, 2,3,7,8-tetrachlorodibenzofuran(2,3,7,8-TCDF), 1,2,3,7,8-pentachlorodibenzofuran(1,2,3,7,8-PCDF) 2, 3, 4, 7, 8-pentachlorodibenzofuran (2, 3,4, 7, 8-PCDF), and TCDD significantly enhanced the enzyme activity, and the induced AHH activities with the three PCDF isomers were about 30–65% of those of TCDD. These results indicate that AHH responsiveness in mice segregates with the induction of AHH activity by PCDF isomers and may also segregate with the toxic potency of the isomers; i.e., toxic potencies of 2,3,7,8-TCDF, 1,2,3,7,8-PCDF, and 2,3,4,7,8-PCDF in AHH-responsive strains of mice may be much greater than those in AHH-nonresponsive strains of mice. Taking into account both the potent AHH inducibility and the high bioaccumulation of 2,3,7,8-TCDF, 1,2,3,7,8-PCDF, and 2,3,4,7,8-PCDF, these three PCDF isomers should be given greater attention with regard to environmental contamination.

Comparative toxicity of 2,3,4,7,8-pentachlorodibenzofuran in inbred strains of mice

2,3,4,7,8-Pentachlorodibenzofuran(PenCDF) was one of the major components of PCDFs in Yusho and Yu-Cheng victims and environmental samples. Toxicity of PenCDF have not been well examined except its effects on hepatic enzyme inducing activity and binding to cytosolic receptor protein, although there have been many toxicological studies on PCDDs, PCDFs and especially 2,3,7,8-tetrachlorodibenzo-p-dioxin. The authors examined long-term effect of PenCDF on aromatic hydrocarbon hydroxylase (AHH) responsive and non-responsive strains of mice.

Correspondence to the Editor Re: Maternal exposure to high levels of dioxins in relation to birth weight in women affected by Yusho disease

Tsukimori et al. (2012) studied the relationship between the birth weights and the estimated concentrations of PCDDs PCDFs and nonortho PCBs in the blood of mothers affected by Yusho, as well as Tsukimori et al. (2013b) and the estimated mean concentrations of PCDDs, PCDFs and non-ortho PCBs were 328.5, 661.4 and 44.1 pgTEQ/g lipid, respectively, at the childbirth, which was about 20 to 40 years before the blood sampling. This estimation of concentrations of PCDDs is, however, nonsense, because at the time PCDDs were not detected in the rice bran oils which caused Yusho, i.e., Yusho oil (Kashimoto et al., 1985; Masuda et al., 1985; Miyata et al., 1985; Nagayama et al., 1975, 1976) and also in the tissues of patients with Yusho (Nagayama et al., 1977). In 2002, Yao et al. (2002) found PCDDs in Yusho oil and TEQ concentrations of PCDDs and PCDFs were 17 ppb and 470 ppb, respectively. The level of PCDFs was about 30 times higher than that of PCDDs. PCDFs have been considered as the true causative agent of Yusho and fetal Yusho (Kashimoto et al., 1981; Kunita et al., 1984, 1985; Nagayama et al., 2010). The present concentrations of PCDDs in the blood of Yusho mothers are derived mostly through food and not from Yusho oil. If we employ the same estimation method of PCDD concentration in their studies, the estimated mean concentration of PCDDs in the blood of control mothers is 218.7 pg-TEQ/g lipid, which is incredibly high and we have never determined such a high concentration of PCDDs in the blood of healthy people so far. If they were contaminated with such a high concentration of PCDDs, namely, 328.5 pg-TEQ/g lipid, the concentration of PCDDs in the umbilical cord of fetal Yusho should be comparable to that of PCDFs, because the placental transfer of PCDDs to the fetus was much easier than that of PCDFs (Tsukimori et al., 2013a). The mean concentration of PCDDs was, however, only about one tenth of PCDFs in the umbilical cord of fetal Yusho patients (Nagayama et al., 2010). Therefore, their studies are completely wrong. Yorifuji et al. (2014) have also raised an objection to their studies. Furthermore, concentrations of PCDDs and PCDFs in the blood are changed by countless factors. Hence, it is impossible to estimate their concentrations of