Jouko Tuomisto

Flame retardants in placenta and breast milk and cryptorchidism in newborn boys

Background Polybrominated diphenyl ethers (PBDEs) are widely used in Western countries. Objectives Because the prevalence of cryptorchidism appears to be increasing, we investigated whether exposure to PBDEs was associated with testicular maldescent. Methods In a prospective Danish–Finnish study, 1997–2001, all boys were examined for cryptorchidism. We analyzed whole placentas (for 95 cryptorchid/185 healthy boys) and individual breast milk samples (62/68) for 14 PBDEs and infant serum samples for gonadotropins, sex-hormone binding globulin, testosterone, and inhibin B. Results In 86 placenta–milk pairs, placenta PBDE concentrations in fat were lower than in breast milk, and a larger number of congeners were nondetectable. There was no significant difference between boys with and without cryptorchidism for individual congeners, the sum of 5 most prevalent, or all 14 congeners. The concentration of PBDEs in breast milk was significantly higher in boys with cryptorchidism than in controls (sum of BDEs 47, 153, 99, 100, 28, 66, and 154: median, 4.16 vs. 3.16 ng/g fat; p < 0.007). There was a positive correlation between the sum of PBDEs and serum luteinizing hormone (p < 0.033). The sum of PBDEs in breast milk did not differ between Denmark and Finland (median, 3.52 vs. 3.44 ng/g fat), but significant differences in some individual congeners were found. Conclusions Two different proxies were used for prenatal PBDE exposure, and levels in breast milk, but not in placenta, showed an association with congenital cryptorchidism. Other environmental factors may contribute to cryptorchidism. Our observations are of concern because human exposure to PBDEs is high in some geographic areas.

Aryl Hydrocarbon Receptor Regulates Distinct Dioxin-Dependent and Dioxin-Independent Gene Batteries

Conventional biochemical and molecular techniques identified previously several genes whose expression is regulated by the aryl hydrocarbon receptor (AHR). We sought to map the complete spectrum of AHR-dependent genes in male adult liver using expression arrays to contrast mRNA profiles in Ahr-null mice (Ahr–/–) with those in mice with wild-type AHR (Ahr+/+). Transcript profiles were determined both in untreated mice and in mice treated 19 h earlier with 1000 μg/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Expression of 456 ProbeSets was significantly altered by TCDD in an AHR-dependent manner, including members of the classic AHRE-I gene battery, such as Cyp1a1, Cyp1a2, Cyp1b1, and Nqo1. In the absence of exogenous ligand, AHR status alone affected expression of 392 ProbeSets, suggesting that the AHR has multiple functions in normal physiology. In Ahr–/– mice, only 32 ProbeSets exhibited responses to TCDD, indicating that the AHR is required for virtually all transcriptional responses to dioxin exposure in liver. The flavin-containing monooxygenases, Fmo2 and Fmo3, considered previously to be uninducible, were highly induced by TCDD in an AHR-dependent manner. The estrogen receptor α as well as two estrogen-receptor-related genes (α and γ) exhibit AHR-dependent expression, thereby extending cross-talk opportunities between the intensively studied AHR and estrogen receptor pathways. p53 binding sites are over-represented in genes down-regulated by TCDD, suggesting that TCDD inhibits p53 transcriptional activity. Overall, our study identifies a wide range of genes that depend on the AHR, either for constitutive expression or for response to TCDD.

Non-carcinogenic effects of TCDD in animals

Exposure to TCDD and related chemicals leads to a plethora of effects in multiple species, tissues, and stages of development. Responses range from relatively simple biochemical alterations through overtly toxic responses, including lethality. The spectrum of effects shows some species variability, but many effects are seen in multiple wildlife, domestic, and laboratory species, ranging from fish through birds and mammals. The same responses can be generated regardless of the route of exposure, although the administered dose may vary. The body burden appears to be the most appropriate dosimetric. Many of the effects often attributed to TCDD are associated with relatively high doses: lethality, wasting, lymphoid and gonadal atrophy, chloracne, hepatotoxicity, adult neurotoxicity, and cardiotoxicity. Changes in multiple endocrine and growth factor sytems have been reported in a manner which is tissue, sex, and age-dependent. The most sensitive adverse effects observed in multiple species appear to be developmental, including effects on the developing immune, nervous, and reproductive systems. Such effects have been observed at maternal body burdens in the range of 30–80 ng/kg in both non-human primates and rodents. Biochemical effects on cytokine expression and metabolizing enzymes occur at body burdens which are within a factor of ten of the clearly adverse developmental responses. Thus, effects on the immune system, learning, and the developing reproductive system of multiple animals occur at body burdens which are close to those present in the background human population.

Decreased uptake of 5-hydroxytryptamine in blood platelets from patients with endogenous depression

Abstract5-Hydroxytryptamine (5-HT) uptake was studied by using blood platelets from 13 patients with endogenous depression (Hamilton rating scale 33±7) and 13 healthy volunteers. An improved method with a short incubation time and low substrate concentration was used, and the incubation was performed in Krebs-Henscleit buffer (pH 7.4) at 37° C. A clear difference in 5-HT uptake by blood platelets was noted: The Vmax of the reaction in patients was 39, and in controls 71 pmol per 2×107 platelets in 5 min. There was no significant difference in the Km. After a 4-week treatment with imipramine, a competitive inhibition of 5-HT uptake with an increased Km was seen; after a similar treatment with amoxapine there was little change in 5-HT uptake. Amoxapine was inferior to imipramine as an inhibitor of 5-HT uptake, also in vitro. There was no difference in clinical recovery in these treatment groups. These results may be of importance so as to understand the potential biological differences between depressed patients and normal persons.

Impact of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls on human and environmental health, with special emphasis on application of the toxic equivalency factor concept

A scientific evaluation was made of the mechanisms of action of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls. Distinction is made between the aryl-hydrocarbon (Ah) receptor-mediated and non-Ah receptor-mediated toxic responses. Special attention is paid to the applicability of the toxic equivalency factor (TEF) concept.

A new modification for studying 5-HT uptake by blood platelets: a re-evaluation of tricyclic antidepressants as uptake inhibitors.

The effect of imipramine and other antidepressive drugs on 5‐HT uptake by rabbit platelets was re‐evaluated, since it had become obvious that, in previous studies, too high substrate concentrations and too long incubation times had been used. A Km of 1·8 times 10−7m was obtained for 5‐HT uptake when 1 min incubation in plasma was used. Imipramine caused a half‐maximal inhibition at 10−7m or lower concentration. When the platelet‐rich plasma was diluted with buffer solution, only about 2 times 10−8m imipramine was required for 50% inhibition. This concentration is only 1/500 to 1/100 of concentrations described in most earlier data. In this study, other tricyclic drugs and phenothiazine derivatives were also much more effective than previously demonstrated. Their rank of potency order was, however, very similar to that earlier described. The correlation of uptake inhibition in platelets with 5‐HT uptake inhibition in brain synaptosomes was found to be highly significant. It is concluded that the previous studies give valuable information on the relative potency of different drugs inhibiting 5‐HT uptake. When the technique is modified as suggested by the present results, the level of uptake‐inhibiting potency in an absolute sense is close to that described for other tissues, especially brain synaptosomes or slices. Therefore, platelets can more reliably be used as an easily obtainable model for nerve endings in uptake studies.

Polychlorinated dibenzo-p-dioxins and dibenzofurans via mother's milk may cause developmental defects in the child's teeth.

Previous studies have shown developmental dental defects in rhesus macaques and rats experimentally exposed to dioxin. Now it was investigated if dioxin exposure from mothers milk in a normal breast-fed child population correlated with enamel hypomineralization of teeth that mineralize during the first 2 years of life. We studied 102 6-7-year-old Finnish children breast-fed for an average of 10.5 months. Milk samples were collected when the child was 4 weeks old. The concentrations of 17 most toxic polychlorinated dibenzo-p-dioxin and furan congeners were determined. The total exposure to dioxins was calculated from the concentrations in milk and the duration of breast feeding. Hypomineralization of the target teeth was found in 17 children. Both the frequency and severity of the lesions correlated with the total exposure. The results suggest that at the prevailing levels in human milk, dioxin may be an important cause of hypomineralization in the developing teeth of children.

Drinking water mutagenicity and gastrointestinal and urinary tract cancers: an ecological study in Finland.

OBJECTIVES The purpose of this study was to investigate the relationship between exposure to mutagenic drinking water and cancers of the gastrointestinal and urinary tract. METHODS Past exposure to drinking water mutagenicity was assessed in 56 Finnish municipalities for the years 1955 and 1970. The cases of bladder, kidney, stomach, colon, and rectum cancers were derived from two periods (1967 to 1976 and 1977 to 1986). Age, sex, social class, urban living, and time period were taken into account in the Poisson regression analysis. RESULTS Statistically significant exposure-response association was observed between exposure and incidence of bladder, kidney, and stomach cancers. In an ordinary municipality using chlorinated surface water, this exposure would indicate a relative risk of 1.2 for bladder cancer and of 1.2 to 1.4 for kidney cancer compared with municipalities where nonmutagenic drinking water was consumed. CONCLUSIONS The acidic mutagenic compounds present in drinking water may play a role in the etiology of kidney and bladder cancers, but, because the results are based on aggregate data, they should be interpreted with caution.

Effects of 2,3,7,8‐Tetrachlorodibenzo‐p‐Dioxin on Bone in Two Rat Strains with Different Aryl Hydrocarbon Receptor Structures

Polychlorinated dibenzo‐p‐dioxins (PCDDs) are highly toxic environmental contaminants, and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) is the most potent dioxin. Here, we studied the effects of TCDD on bone. Two rat strains, Han/Wistar (H/W) and Long‐Evans (L‐E), were used because they exhibit a 1000‐fold sensitivity difference in acute lethality of TCDD, which difference is related to the aryl hydrocarbon receptor (AHR). TCDD inhibited the tibial growth dose dependently, the effect being manifested at lower doses in the more sensitive L‐E strain. In H/W rats the effect of TCDD was seen only at the high dose of 170 μg/kg (p < 0.05), whereas in the sensitive L‐E rats a significant reduction of bone growth was already seen at 1.7 μg/kg (p < 0.01). This reduction was caused by the smaller tibial size because the diaphyseal bone mineral density (BMD) did not change. The three‐point bending breaking force of the tibia was significantly reduced in H/W rats at 170 μg/kg (p < 0.05), but tibial stiffness was lower already at the dose of 17 μg/kg (p < 0.05). In the sensitive L‐E strain, both breaking force and stiffness were reduced at the dose of 17 μg/kg (p < 0.001). These results indicate that TCDD dose‐dependently interferes with bone growth, modeling, and mechanical strength. The altered transactivation domain of AHR is associated with a lower sensitivity of bone to TCDD in H/W rats, suggesting that AHR plays a role in modulating the effects of dioxins on bone.

Developmental dental aberrations after the dioxin accident in Seveso.

Children’s developing teeth may be sensitive to environmental dioxins, and in animal studies developing teeth are one of the most sensitive targets of toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Twenty-five years after the dioxin accident in Seveso, Italy, 48 subjects from the contaminated areas (zones A and B) and in patches lightly contaminated (zone R) were recruited for the examination of dental and oral aberrations. Subjects were randomly invited from those exposed in their childhood and for whom frozen serum samples were available. The subjects were frequency matched with 65 subjects from the surrounding non-ABR zone for age, sex, and education. Concentrations of TCDD in previously analyzed plasma samples (zone ABR subjects only) ranged from 23 to 26,000 ng/kg in serum lipid. Ninety-three percent (25 of 27) of the subjects who had developmental enamel defects had been < 5 years of age at the time of the accident. The prevalence of defects in this age group was 42% (15 of 36) in zone ABR subjects and 26% (10 of 39) in zone non-ABR subjects, correlating with serum TCDD levels (p = 0.016). Hypodontia was seen in 12.5% (6 of 48) and 4.6% (3 of 65) of the zone ABR and non-ABR subjects, respectively, also correlating with serum TCDD level (p = 0.05). In conclusion, developmental dental aberrations were associated with childhood exposure to TCDD. In contrast, dental caries and periodontal disease, both infectious in nature, and oral pigmentation and salivary flow rate were not related to the exposure. The results support our hypothesis that dioxins can interfere with human organogenesis.