From science to policy: How European HBM indicators help to answer policy questions related to phthalates and DINCH exposure

Within the European Human Biomonitoring (HBM) Initiative HBM4EU we derived HBM indicators that were designed to help answering key policy questions and support chemical policies. The result indicators convey information on chemicals exposure of different age groups, sexes, geographical regions and time points by comparing median exposure values. If differences are observed for one group or the other, policy measures or risk management options can be implemented. Impact indicators support health risk assessment by comparing exposure values with health-based guidance values, such as human biomonitoring guidance values (HBM-GVs). In general, the indicators should be designed to translate complex scientific information into short and clear messages and make it accessible to policy makers but also to a broader audience such as stakeholders (e.g. NGO's), other scientists and the general public. Based on harmonized data from the HBM4EU Aligned Studies (2014-2021), the usefulness of our indicators was demonstrated for the age group children (6-11 years), using two case examples: one phthalate (Diisobutyl phthalate: DiBP) and one non-phthalate substitute (Di-isononyl cyclohexane-1,2- dicarboxylate: DINCH). For the comparison of age groups, these were compared to data for teenagers (12-18 years), and time periods were compared using data from the DEMOCOPHES project (2011-2012). Our result indicators proved to be suitable for demonstrating the effectiveness of policy measures for DiBP and the need of continuous monitoring for DINCH. They showed similar exposure for boys and girls, indicating that there is no need for gender focused interventions and/or no indication of sex-specific exposure patterns. They created a basis for a targeted approach by highlighting relevant geographical differences in internal exposure. An adequate data basis is essential for revealing differences for all indicators. This was particularly evident in our studies on the indicators on age differences. The impact indicator revealed that health risks based on exposure to DiBP cannot be excluded. This is an indication or flag for risk managers and policy makers that exposure to DiBP still is a relevant health issue. HBM indicators derived within HBM4EU are a valuable and important complement to existing indicator lists in the context of environment and health. Their applicability, current shortcomings and solution strategies are outlined.

Effect of inhibitors of myeloperoxidase on the development of aortic atherosclerosis in an animal model

Our earlier studies have shown that some steroids increase myeloperoxidase enzyme (MPO) release from human granulocytes, and that MPO plasma levels are significantly lower in postclimacteric people. Moreover, we have proven that MPO inhibits production of atherogenic free radical superoxide anion and MPO-inhibitors increase superoxide release. The aim of the present study was to investigate the effect of MPO-inhibitors on the early phase of aortic atherosclerosis, namely the extent of intimal plaques and the thickening of the medial layer. Adult male rabbits were fed with lipid rich food (cholesterol: 1.3%, peanut oil: 8%) for 8 weeks. During this period MPO-inhibitors were also given (4-aminobenzoicacid-hydrazide/ABAH/-13.3 mg/kg/day or indometacin-5 mg/kg/day). All animals developed intimal lipid plaques (raised fatty streaks). The relative plaque-covered areas of the aortas were compared and the media thickness of the aorta was measured on plaque-free as well as plaque-containing areas. The medial smooth muscle density and peroxidase activity of the aortic media were also determined. The media thickness increased (p<0.05) in the cholesterol+ABAH as well as in the cholesterol+indometacin groups up to 375.7 (+/-60.5) and 442.5 (+/-123.4) microm, respectively, compared to the control group (cholesterol feeding alone) where it measured only 308.4 (+/-51.67) microm. The medial peroxidase activity decreased significantly in the indometacin treated group and showed a decreasing tendency using ABAH. In parallel to this there was a tendency of increase in the relative plaque covered areas. The smooth muscle density showed no significant modifications, while inhibitors of the MPO seemed to enhance aortic medial thickness, i.e. the grade of a pre-atherosclerotic lesion, in our animal model. Collectively, the anti-atherogenic effect of certain steroid hormones might be realized through the impact on MPO activity.

Systematic investigation of different steroid precursors with respect to their effect on superoxide anion production by human neutrophil granulocytes

Free radicals are involved in several pathological processes in living organisms, for example in athero- and oncogenesis. Some steroids are known to be effective antioxidants, while others do not play any such role. The aim of our study was to examine the antioxidant capability of different metabolites in the synthesis of steroid hormones. As a model, we chose human neutrophils producing superoxide anion, which is the source of many other radicals. Neutrophils were separated from healthy volunteers. Isolated cells were incubated with varying concentrations of steroid compounds and stimulated with N-formyl-Met-Leu-Phe. Superoxide anion production was determined by photometry. Neutrophils incubated with corticosterone and 18-hydroxy-deoxycorticosterone showed a significant reduction in superoxide production, whereas we found a significant enhancement in the presence of 11beta-hydroxyprogesterone. Furthermore, we observed a non-significant decreasing trend after incubation with cholesterol 3-sulphate and an increasing tendency using 11-hydroxyandrostenedione. We were also able to produce newer morphological and functional evidence of the role of myeloperoxidase enzyme in the steroidal antioxidant effect by electronic microscopy and use of sodium hypochlorite in our incubation model. Based on these results, we conclude that not only steroid end products but also their intermediate metabolites, most of which are also present in human plasma, partly influence free radical metabolism. Thus, this study provides further argument for the search for the molecular basis responsible for the antioxidant effect of steroid structures. This may lead to new opportunities for finding really efficient antioxidants, which might perhaps be used in a combined manner with other agents in the fight against certain life-threatening diseases.

Plasma concentration of myeloperoxidase enzyme in pre- and post-climacterial people: related superoxide anion generation

Neutrophil granulocytes are involved in the pathogenesis of atherosclerosis also through their free radical generation. The aim of the study was to test how extracellular levels of myeloperoxidase (MPO; a granulocyte enzyme playing role in free radical production) change by age and what effect this change has on the production of the free radical superoxide anion by neutrophils. We also wanted to examine whether the antioxidant effect of different steroid hormones is realized through the MPO. Plasma myeloperoxidase concentrations of healthy blood donors were quantified by ELISA. Superoxide anion production was measured by photometry. Myeloperoxidase concentration was significantly lower in plasmas obtained from older women and men than in those from younger subjects. Adding the MPO inhibitors 4-aminobenzoic acid hydrazide (ABAH) and indomethacin to the granulocytes, the generation of superoxide anion increased and the decreasing effect of the steroids on superoxide production was inhibited. Incubating the neutrophils with the product of the reaction catalyzed by MPO itself (hypochlorite anion), we found significant decrease in superoxide generation. According to our results MPO seems to diminish the production of superoxide anion and so probably has an antioxidant ability. Therefore, its lower plasma levels may contribute to the increasing incidence of atherosclerosis and other free radical mediated disorders in old people. Thus, after further studies MPO might become one of the indicators of cardiovascular risk and the scavenger capacity in general.

Induced myeloperoxidase activity and related superoxide inhibition during hormone replacement therapy

OBJECTIVE

To test whether the menopause entails any changes in the myeloperoxidase activity of neutrophil granulocytes. The effects of hormone replacement therapy on myeloperoxidase activity and related changes in free radical production were also investigated.

DESIGN

Laboratory investigation of the effect of oestrogen on intracellular myeloperoxidase activity and release from human neutrophil granulocytes. Analysis of related changes in superoxide anion generation.

SETTING

2nd Department of Medicine and 1st Department of Obstetrics and Gynaecology, Semmelweis University, Budapest.

SAMPLES

Intracellular myeloperoxidase activity (mean peroxidase index) was measured automatically in blood samples obtained for general laboratory work-up from 135 randomly selected patients in our department. Blood samples from 11 postmenopausal women were analysed before and during hormone replacement therapy. Blood samples from 20 healthy volunteers were obtained and neutrophil granulocytes separated for in vitro measurement of superoxide anion production after adding myeloperoxidase to the incubation media.

METHODS

The mean peroxidase index was measured using a Technicon H-3 instrument. myeloperoxidase release from neutrophils was quantified by ELISA technique. Superoxide production of isolated neutrophil granulocytes was measured by photometry.

MAIN OUTCOME MEASURES

Intracellular activity of myeloperoxidase, concentration of myeloperoxidase-protein in supernatant of neutrophils, release of superoxide anion from neutrophil granulocytes.

RESULTS

1. Intracellular myeloperoxidase activity in neutrophils was lower in postmenopausal women, than in females with regular cycles (-1.84 +/- 3.06 versus 1.59 +/- 3.55, P < 0,001). 2. In postmenopausal women intracellular myeloperoxidase activity and myeloperoxidase release increased during hormone replacement therapy (-5.54 +/- 6.63 versus -0.2 +/- 6.05; P < 0.001 and 52.74 mU/ml +/- 25.73 versus 251.4 +/-234.1 mU/ml; P < 0.05). 3. Adding myeloperoxidase to neutrophil granulocyte suspensions, the production of superoxide anion fell (e.g. adding 280 ng/ml myeloperoxidase: 77.9 +/- 14.04 % of control production, P < 0.001).

CONCLUSION

Hormone replacement restores the reduced myeloperoxidase activity in menopausal women. Adding myeloperoxidase to neutrophil granulocytes, the production of free radicals decreases.

Acute, nongenomic vasodilatory action of estradiol is attenuated by chronic estradiol treatment

Deficiency of estradiol or chronic estrogen treatment may alter the responses to this hormone in many tissues. A possible interaction between the acute nongenomic and the chronic effects of estradiol on microvessels have not been investigated yet. In the present study we have investigated whether acute in vitro vasodilatory action of estradiol on a small artery is altered by chronic estradiol pretreatment. Female rats were surgically ovariectomized and subjected to either estradiol replacement therapy (estradiol propionate, 450 micrograms/kg/week) or vehicle administration for 5 weeks. Cylindrical segments of the saphenous artery were studied using videocomputerized microarteriography in vitro. Estradiol, in concentrations of 10(-6) to 10(-4) M relaxed norepinephrine precontracted vessel segments in a dose-dependent manner. Magnitude of relaxation observed in arteries of estradiol replaced animals was significantly smaller at all concentrations than that of nonreplaced ovariectomized rats; maximal relaxation in the control ovariectomized group was 64.5% +/- 3.6%, while it was 34.3% +/- 4.2% only in the ovariectomized and estradiol replaced group (P < 0.001). Comparison of acute relaxations in response to papaverine and nifedipine failed to prove a reduced activity of the general relaxation machinery in estradiol replaced animals. We conclude that chronic estradiol replacement can downregulate the acute nongenomic vasorelaxation effect of this hormone in small arteries of ovariectomized rats.

In vitro effects of different steroid hormones on superoxide anion production of human neutrophil granulocytes

Neutrophil granulocytes play an important role in atherogenesis also through their free radical generation. According to recent studies, a point of action by which estrogens can provide protection against atherosclerosis is their inhibiting effect on superoxide anion production. The aim of our study was to test whether this means a common effect of steroids on superoxide production, or whether various steroid hormones have different action on superoxide generation of human granulocytes. Neutrophils were separated from the blood samples of twelve healthy volunteers. Isolated cells were incubated with different concentrations (10(-9), 10(-8), 10(-7) M) of hydrocortisone, aldosterone, cortexolone, 17-beta-estradiol, progesterone, and testosterone. Superoxide anion production was determined by photometry using the reduction of ferricytochrome-C. Compared to that of control cells neutrophils incubated with 17-beta-estradiol, progesterone, testosterone and hydrocortisone showed significantly reduced superoxide production. No significant alteration of superoxide anion production was found after the incubation of cells with aldosterone and cortexolone. It is concluded that similarly to estradiol other sex steroids and cortisol can inhibit the free radical production of human granulocytes, but mineralocorticoid aldosterone and Reichstein's substance S do not show such activity. Our results provide new evidence supporting the theory that certain types of steroid hormones have antioxidant capacity. This may give further reasons for investigating the molecular background of the existence or absence of this property and thus might lead to the development of new free radical scavengers.

Postmenopausal hormone replacement improves proteinuria and impaired creatinine clearance in type 2 diabetes mellitus and hypertension

OBJECTIVE

To determine whether hormone replacement therapy can reverse established renal microvascular damage in type 2 diabetes and hypertension.

DESIGN

Prospective, single centre clinical trial.

SETTING

Outpatient clinics.

PARTICIPANTS

Sixteen diabetic and hypertensive postmenopausal women (age 47-57 years)

METHODS

Administration of a cyclic combination of oestradiol and norgestrel orally for 3.5 monthly cycles.

RESULTS

Comparing the baseline values, mean (SD) 24-hour urine protein excretion was reduced from 0.452 g (0039) to 0.370 g (0.047) (P < 0.01) and creatinine clearance was increased from 1.68 mL/sec (0.11) to 1.77 mL/sec (0.08) (P < 0.05). Fasting plasma glucose also improved from 6.92 mmol/L (0.47) to 6.51 mmol/L (0.28) (P < 0.05), as did serum total cholesterol from 7.26 mmol/L (0.28) to 6.65 mmol/L (0.14) (P < 0.05). Blood pressure did not change significantly. Univariate linear regression analysis showed no significant correlation between the individual changes in blood pressure, fasting plasma glucose or serum cholesterol and the individual changes in proteinuria or creatinine clearance.

CONCLUSIONS

This study shows that hormone replacement therapy may reduce proteinuria, and even improve creatinine clearance, in diabetic and hypertensive postmenopausal women. These effects are additive to nephroprotective therapy, and the mechanisms appear unrelated to conventional risk factors for vascular complications, such as high blood pressure, elevated plasma glucose or serum cholesterol.

[Changes in the myeloperoxidase activity of human neutrophilic granulocytes and the amount of enzyme deriving from them under the effect of estrogen]

Free radicals which are produced constantly in the human body have a significant role in the development of atherosclerosis. The responsibility of leukocytes for vascular disease has been proved in several ways. Hormonally active women are protected much more against myocardial infarction than men, which fact can be explained partly by endocrinological reasons, too. The authors have set the aim to investigate whether estrogen therapy effects on the one hand the intracellular activity of the granulocyte-enzyme, myeloperoxidase (MPO), which takes place in free radical reactions and on the other hand the amount of MPO released from neutrophils. In the case of women having menopause and being treated with hormone replacement (n = 11) the intracellular activity and the amount of MPO-release increased significantly as compared to the level at the time of starting taking the medicine (p < 0.001). Based on the results it can be supposed that the vasoprotective effect of estrogens is fulfilled through their influence on the MPO enzyme, too. Besides the fact that intensified MPO activity through enhanced consumption might induce the decreased accumulation of H2O2 (a reactive oxygen species, substrate of MPO), MPO also has a role in the termination of the whole process of free radical production in granulocytes by the inactivation of the NADPH-oxidase system. This means that the growing intracellular MPO activity and the increased amount of enzyme released induce the decrease of the amount of free radicals produced during the "respiratory burst" and this is advantageous from the point of view of vasoprotection. The increased MPO activity and the NADPH-oxidase inactivation supposed to be elicited by it, might have further positive consequences since MPO has an effect on HDL-metabolism and the outflow of cholesterol from "foam cells", NADPH-oxidase has a suspected role in LDL-oxidation and NADPH is one of the cofactors of NO-synthase (NOS). The decreased superoxide anion level on the other hand may mitigate the chance of the neutralizing of nitric oxide (NO) by it. The superoxide anion is a potent vasoconstrictor and therefore, its diminished production may be beneficial, i.e. decreases the risk of coronary spasm. The new conceptual synthesis worked out by the authors may provide a possible explanation of the increased susceptibility to infections during steroid treatment, too.

The effect of ovariectomy and oestrogen replacement on small artery biomechanics in the rat

OBJECTIVE

To determine the effects of oestrogen deficiency and hormone replacement therapy on the biomechanical properties of a small artery.

SAMPLE

Thirty non-pregnant female Sprague-Dawley rats.

METHODS

Twenty animals were pharmacologically ovariectomised by triptorelin and received either oestradiol propionate or its vehicle. Ten other animals received only the vehicle for the same period of time (control group). After 12 weeks of treatment, cylindrical segments of the saphenous artery were isolated and cannulated at both ends. Pressure-diameter curves were recorded from segments in normal Krebs-Ringer, using norepinephrine, and then with papaverine. The vessel segment close to the examined one was histologically evaluated. Serum levels of oestradiol and cortisol were determined.

MAIN OUTCOME MEASURES

Biomechanical parameters based on the pressure-diameter curves.

RESULTS

Pharmacological ovariectomy decreased the passive diameter of the arteries and oestrogen replacement therapy prevented this. Decreased reactivity to norepinephrine was also restored by oestrogen treatment. Pressure induced myogenic tone was decreased significantly by oophorectomy and increased after oestradiol treatment. No significant changes were found in wall thickness, distensibility, elastic modulus or tangential stress. No significant histological alterations were seen in the vessel wall. Oestradiol levels were significantly decreased in the castrated animals compared with the other two groups.

CONCLUSIONS

These results suggest that oestrogen deficiency decreases and oestrogen replacement increases the passive diameter of small peripheral arteries, and that oestrogen enhances the reactivity of vascular smooth muscle. These responses may provide the background mechanisms for the increased incidence of arterial hypertension and hot flushes during the menopause and the ability of oestrogen substitution to prevent them.

Direct relaxing effect of estradiol-17beta and progesterone on rat saphenous artery

Although estrogen has been reported to relax large coronary arteries immediately, its direct acute effect on small vessel tone has not been fully defined. In this study, we investigated the effect of estradiol-17beta and progesterone on isolated rat saphenous artery segments-with an internal radius of 250 microm-by measuring the outer diameter of the vessels using in vitro angiometry. Estradiol and progesterone at concentrations of 1-100 and 8.6-86 microM induced a rapid, dose-dependent relaxation of the arterial segments precontracted with norepinephrine. Maximal changes of diameters were 85.8 +/- 10 and 90.9 +/- 8%. Clomiphene citrate, a cytoplasmic receptor antagonist, did not diminish this action of estradiol, with the exception of the highest concentrations of the hormone. Thus a nongenomic pathway for this effect can be suspected. Dexamethasone did not induce similar vasodilation. It is concluded that estradiol and progesterone have similar rapid vasorelaxing effects on small muscular arteries as found previously on coronary arteries.