Calcium, magnesium and aluminium ions as decontaminating agents against dermal fluoride absorption following hydrofluoric acid exposure.

The fluoride ions of the industrially largely irreplaceable, locally corrosive hydrofluoric acid (HF) can scavenge cations in biological tissues, which explains their high toxic potential, and also leads to local acidification through proton release. The influence of three complexing agents, calcium (Ca2+) gluconate (as 2.5% Ca2+gel and individually (2.84%) or commercially (10%) formulated Ca2+solution), magnesium (Mg2+) gluconate (2.84%) solution and aluminium (Al3+) solution (Hexafluorine®, pure and diluted) on the absorption of fluoride following HF exposure (1-3 min, 100 µl, 30%/0.64 cm2) through human skin was investigated in an ex-vivo diffusion cell model. Fluoride absorption was assessed over 6-24 h and analysed with a fluoride electrode. Decreasing the contamination time reduced the fluoride absorption distinctly which was further reduced by the application of fluoride-binding decontamination agents (Ca2+, Mg2+, Al3+) or water alone without being significantly different. Ca2+ appeared slightly more effective than Mg2+ in reducing fluoride absorption. Moreover, the addition of pH adjusting buffer promoted the decontamination efficacy. Fluoride-binding agents can facilitate the decontamination of dermal HF exposure. However, prompt decontamination appeared to be the key to successful limitation of fluoride absorption and pushes the choice of decontamination agent almost into the background.

Validity of different biomonitoring parameters for the assessment of occupational exposure to N,N-dimethylformamide (DMF).

This study was performed to assess the relation between occupational exposure to N,N-dimethylformamide after an 8 h work shift in the acrylic fibre industry and its three biological markers N-methylformamide (NMFtotal), N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), and N-methylcarbamoyl adduct at haemoglobin (MCVal). External DMF exposure of 220 workers was determined during the whole shift. A standardised questionnaire was used to obtain information about the worker's general health status, medical treatment, smoking habits, protective measures, and possible symptoms caused by DMF exposure. NMF and AMCC were analysed in post-shift urine samples and MCVal in blood. For longitudinal assessment the average AMCC concentration was determined over a period of 4 weeks (weekly sampling) in a sub-collective of 89 workers. The median of DMF concentration in air was 3.19 mg/m3 (range < 0.15-46.9 mg/m3). The biological markers showed a median of 4.80 mg/L (range 0.20-50.6 mg/L) for NMFtotal, 4.75 mg/g creatinine (range 0.06-49.6 mg/g creatinine) for AMCC, and 57.5 nmol/g globin (range 0.5-414 nmol/g) for MCVal. A significant linear relationship was observed between DMF in air and NMF as well as between DMF in air and AMCC in post-shift urine samples. The mean AMCC values measured weekly over a period of 4 weeks correlated significantly with MCVal adducts too. Excluding workers who had been using breathing masks on the day of the study led to even tighter correlations. The results of the present study demonstrate the applicability of the DMF biomonitoring parameters NMFtotal in post-shift urine for the present-day exposure assessment, AMCC in the post-shift urine after several shifts for assessment of the cumulative exposure of the previous working days, and MCVal for assessment of long-term exposure during previous weeks and months. The data of the present study enable now the estimation of valid equivalents of these biomonitoring parameters to the external DMF exposure. From the risk assessment point of view, the exposure limit values for AMCC and MCVal, which are directly linked to the presumed toxic intermediate MIC, exhibit a significant advance.

2A-DUB/Mysm1 Regulates Epidermal Development in Part by Suppressing p53-Mediated Programs.

Development and homeostasis of the epidermis are governed by a complex network of sequence-specific transcription factors and epigenetic modifiers cooperatively regulating the subtle balance of progenitor cell self-renewal and terminal differentiation. To investigate the role of histone H2A deubiquitinase 2A-DUB/Mysm1 in the skin, we systematically analyzed expression, developmental functions, and potential interactions of this epigenetic regulator using Mysm1-deficient mice and skin-derived epidermal cells. Morphologically, skin of newborn and young adult Mysm1-deficient mice was atrophic with reduced thickness and cellularity of epidermis, dermis, and subcutis, in context with altered barrier function. Skin atrophy correlated with reduced proliferation rates in Mysm1-/- epidermis and hair follicles, and increased apoptosis compared with wild-type controls, along with increases in DNA-damage marker γH2AX. In accordance with diminished α6-Integrinhigh+CD34⁺ epidermal stem cells, reduced colony formation of Mysm1-/- epidermal progenitors was detectable in vitro. On the molecular level, we identified p53 as potential mediator of the defective Mysm1-deficient epidermal compartment, resulting in increased pro-apoptotic and anti-proliferative gene expression. In Mysm1-/-p53-/- double-deficient mice, significant recovery of skin atrophy was observed. Functional properties of Mysm1-/- developing epidermis were assessed by quantifying the transepidermal water loss. In summary, this investigation uncovers a role for 2A-DUB/Mysm1 in suppression of p53-mediated inhibitory programs during epidermal development.

Dermal penetration and resorption of beta-naphthylamine and N-phenyl-beta-naphthylamine from lubricants in an ex vivo human skin model.

Dermal Penetration of aromatic amines (AA's), often suspected or known to be carcinogenic, can play an important role in the overall human exposure. However, information on penetration of certain AA's is poor and inconsistent. Penetration of the former lubricant additive N-phenyl-beta-naphthylamine (PBNA) and its contaminant beta-naphthylamine (BNA) a known carcinogen was investigated and the influence of formulation and co-application characterized. Percutaneous penetration of BNA and PBNA through freshly excised human skin (n = 8; 48 h) was investigated using an ex vivo diffusion cell model. Both AA's were applied in a technical-conform lubricant or dissolved in hexane. The amount of BNA and PBNA applied to skin was 0.52 and 259 µg/0.64 cm2. The analytical determination of AA's was performed by GC-MS. Both, BNA and PBNA penetrated through human skin (38 vs. 5% of applied dose). In contrast to BNA, the percutaneous penetration of PBNA continued beyond the end of exposure. Co-exposure of both AA's increased the intradermal uptake of BNA and PBNA (p < 0.05). Exposure in lubricant showed the least overall penetration (2.9 and 1.9% of applied dose). The results clearly reveal that dermal penetration of both AA's depends strongly on the mode of application. Co-application and formulation alters the penetration of the AA's.

Cross-sectional study on N,N-dimethylformamide (DMF); effects on liver and alcohol intolerance.

PURPOSE: There are still concerns regarding occupational exposure to hepatotoxic DMF. This study was designed to evaluate possible liver damaging effects of DMF under current workplace conditions in synthetic fibres industries. METHODS: Among other laboratory parameters, liver function parameters (alkaline phosphatase (ALP), aspartate aminotransferase, alanine aminotransferase and gamma-glutamyltransferase), the mean corpuscular erythrocyte volume (MCV) and carbohydrate-deficient transferrin (CDT) of the workforce of two companies present at the days of study were investigated. Internal exposure to DMF was assessed via three different biomarkers [sum of N-methylformamide and N-hydroxymethyl-N-methylformamide, N-acetyl-S-(N-carbamoyl)cysteine (AMCC) and 3-methyl-5-isopropylhydantoin (MIH)]. Alcohol consumption was assessed by means of direct ethanol metabolites (ethylglucuronide and ethylsulfate). RESULTS: None of the tested liver enzyme activities showed a positive association with any of the three exposure markers, nor did CDT and MCV. CDT was negatively associated with AMCC and the ALP activity negatively with all three exposure markers. Changes in liver function are seen mainly in conjunction with ethanol consumption but also with increasing body weight and age. MCV was associated with smoking. Almost half of the workers stated to experience alcohol flush reaction. CONCLUSION: The present study indicates that long-term exposure to DMF, which was specified by median urinary AMCC levels of 4.84 mg/g creatinine and DMF haemoglobin adduct levels of 60.5 nmol/MIH/g globin, respectively, does not result in any adverse liver effects. In contrast, these DMF exposure levels still elicit certain alcohol intolerance reactions.

Exposure of the German general population to platinum and rhodium - Urinary levels and determining factors.

In this study the exposure of the general population in Germany to platinum and rhodium and its determinants was investigated in 259 participants (subdivided in three groups) by urine analyses and assessment of the dental status. Complementary, an interview including questions characterising possible exposure to traffic exhaust was conducted. The median excretion was 2.42ng platinum/g creatinine and 7.27ng rhodium/g creatinine. The detailed analysis of the collected data showed significant higher platinum excretion values with increasing number of surfaces covered with restorations containing precious metals (R=0.389; p<0.001), but also higher values for habitants of urban areas (median=3.43ng/g creatinine; 95th percentile=25.2ng/g) compared with those of rural areas (median=2.06ng/g creatinine; 95th percentile=20.0ng/g). Also, participants working in urban areas showed higher platinum excretion values (median=3.27ng/g; 95th percentile=19.6ng/g). Male participants living and working next to highly frequented roads showed higher rhodium excretion values (median=7.27ng/g; 95th percentile=13.5 ng/g). In summary, the study showed that exhaust emissions have an influence on platinum and rhodium excretion, but for platinum this influence is rather low compared to the influence of precious metals containing restorations.

Evaluation of biomarkers assessing regular alcohol consumption in an occupational setting.

PURPOSE: An estimation of ethanol intake is frequently of importance in the frame work of studies, but not trivial to achieve. Problems are "underreporting", a very short time frame for the detection of ethanol as direct marker and interference of many in- and outside body factors with strain parameters. The aim of this study was to explore the suitability of the direct urinary biomarkers ethyl glucuronide (EtG) and ethyl sulphate (EtS) to assess moderate but regular alcohol consumption. MATERIALS AND METHODS: A total of 175 male workers without any known occupational contact to substances influencing liver functions or metabolism of ethanol were examined. Strain parameters of alcohol consumption, i.e. the liver function tests (LFTs: aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase), carbohydrate-deficient transferrin (CDT), mean corpuscular erythrocyte volume (MCV) and the markers of alcohol consumption (EtG and EtS) have been analysed and compared. RESULTS: Up to 14 % of workers had been outside reference range for strain parameters. 62.3 % of the workers had at least traceable amounts of EtG and 84.6 % of EtS. Values above cut-off (indicating voluntary ethanol intake) were found in 34.9 and 51.4 % of the workers for EtG and EtS, respectively. In multiple linear regression analyses, CDT and MCV but not the LFTs showed a dependency from the non-oxidative ethanol metabolites. The LFTs were influenced by BMI. CONCLUSION: Determination of EtG and EtS in urine is an adequate tool to assess moderate but regular alcohol consumption.

Dermal absorption and skin damage following hydrofluoric acid exposure in an ex vivo human skin model.

The wide industrial use of hydrofluoric acid (HF) poses a high risk for accidental dermal exposure. Despite local and systemic hazards associated with HF, information on percutaneous penetration and tissue damage is rare. In the present ex vivo study, the dermal absorption of HF (detected in terms of fluoride ions) was quantified and the skin damaging potential as a function of concentration and exposure duration was assessed. Percutaneous penetration of HF (c=5, 30, and 50%) at 3 exposure durations (3, 5, and 10 min) was investigated in a static diffusion cell model using freshly excised human skin. Alterations of skin were histologically evaluated. HF rapidly penetrated through skin under formation of a considerable intradermal reservoir (∼ 13-67% of total absorbed fluoride). Histologically, epidermal alterations were detected already after exposure to 5% HF for 3 min. The degree of skin damage increased with rising concentration and exposure duration leading to coagulation necrosis. For HF concentrations of ≥ 30%, skin damage progressed into deeper skin layers. Topically applied HF concentration was the principal parameter determining HF induced skin effects. The intradermal HF retention capacity associated with progression and prolongation of HF induced skin effects must be considered in the review of skin decontamination procedures.

Effect of Skin Protection and Skin Irritation on the Internal Exposure to Carbon Disulfide in Employees of the Viscose Industry.

INTRODUCTION: Occupational exposure to carbon disulfide (CS2) leads to inhalative and dermal uptake and thereby to internal exposure. In order to prevent occupational contact dermatitis, gloves and skin protection creams are used at the workplace. The aim of the study was the evaluation of the influence of personal skin protection and irritation on the internal exposure to CS2 of employees in the viscose industry. METHODS: One hundred and eighty-two male CS2-exposed employees were included in the study and were examined regarding working conditions, use of personal protective measures und skin status. Personal air monitoring and biological monitoring was performed and the 'relative internal exposure' (RIE, internal exposure in relation to external exposure) calculated. A multiple regression analysis calculated the influence of skin protection and irritation on CS2 uptake. RESULTS: Usage of skin protection creams and gloves (and both in combination) while working was associated with a significantly higher RIE indicating a higher dermal penetration of CS2. Equally, irritated skin and younger age was associated with a higher internal burden. CONCLUSIONS: Gloves and skin protection creams are useful for preventing occupational skin diseases. However, when handling skin-resorptive substances like CS2, they can increase internal exposure or skin irritation. Therefore, we recommend the careful consideration of benefits and risks of protective creams and gloves at the workplace.

Evaluation of the effect of skin cleaning procedures on the dermal absorption of chemicals.

To reduce the internal exposure, skin decontamination is the most important measure after dermal contact to chemicals. However, no harmonized skin cleaning procedure for experimental ex vivo studies is published. In our study, the impact of two skin cleaning techniques on dermal penetration kinetics and intradermal deposition of 1,4-dioxane, 5% hydrofluoric acid (HF, detected in terms of fluoride ions), and anisole was evaluated to develop a reliable ex vivo skin cleaning method using the diffusion cell technique. After exposure (duration: 3 min (HF); 1h (1,4-dioxane and anisole)) of excised human skin (n=6-8) decontamination was performed by (I) water-soaked cotton swabs or (II) direct application of water on the exposure area. The effect of skin cleaning was investigated by analysing the concentration time course of chemicals in the receptor fluid of diffusion cells and by determining the deposition in skin. Both skin cleaning procedures reduced the amount of fluoride in the skin compartments (p<0.05) and the receptor fluid (p<0.1). However, the effect of cleaning on the dermal absorption of the organic test compounds was not significant. The results demonstrate the suitability of the applied ex vivo protocol for investigating the effectiveness of skin cleaning measures following dermal exposure. In addition, data reveal that the determination of test compounds in both, skin compartments as well as receptor fluid as equivalent for the systemic uptake needs to be considered in studies assessing the effectiveness of skin decontamination procedures.

Differential impairment of the sudomotor and nociceptor axon-reflex in diabetic peripheral neuropathy.

It is not known whether C-fiber functional subclasses are differentially affected by diabetes mellitus or whether the patterns of C-fiber dysfunction are different between type 1 and type 2 diabetes. We therefore examined efferent sympathetic sudomotor and primary afferent nociceptor C-fiber function in diabetic patients. Acetylcholine (10%) was used to evoke C-fiber (axon-reflex)-mediated responses. The nociceptor (flare) response was measured using a laser Doppler device. The sudomotor response was quantified with silastic imprints. The nociceptor C-fiber-mediated flare response was reduced in type 2 diabetic patients (P < 0.008) but was similar to controls in type 1 diabetic patients. The sympathetic C-fiber-mediated responses, including sweat volume (P < 0.05) and the number of activated sweat glands (P = 0.003), were increased in patients with type 1 diabetes. There also was a trend toward a larger axon-reflex sweat area in patients with type 1 diabetes (P = 0.09). No differences in these sweat responses were found in patients with type 2 diabetes compared to controls. These findings suggest that the functional abnormalities in diabetic peripheral neuropathy are not homogeneous and that C-fiber subclasses are differentially affected in type 1 and 2 diabetes mellitus.

Potentiation of evoked calcitonin gene-related peptide release from oral mucosa: a potential basis for the pro-inflammatory effects of nicotine.

Inflammation of the buccal mucosa, gingiva and periodontal tissues is a significant problem in users of nicotine-containing tobacco products; however, the potential role of nicotine in the development of this inflammation is unclear. In many tissues, nicotine, acting through nicotinic acetylcholine receptors (nAChRs), has been shown to increase the release of the pro-inflammatory mediator calcitonin gene-related peptide (CGRP) thereby potentially contributing to neurogenic inflammation. The purpose of the present studies was to determine the effects of nicotine and other nAChR agonists on capsaicin-evoked immunoreactive CGRP (iCGRP) release from rat buccal mucosa and to identify a potential cellular basis for these effects. Using a previously validated model of in vitro superfusion, we show that the nAChR agonists nicotine (EC50 557 micro m), epibatidine (EC50 317 pm) and cytisine (EC50 4.83 nm) potentiated capsaicin-evoked iCGRP release in a concentration-dependent manner by 123, 70 and 76%, respectively. The expression and distribution patterns of the mRNA transcripts encoding the alpha3, alpha4 and alpha6 nAChR subunits and their colocalization with CGRP and the capsaicin receptor VR1 were examined in rat trigeminal ganglion using combined in situ hybridization and immunohistofluorescence. Of all trigeminal neurons counted, mRNA encoding the alpha3, alpha4 and alpha6 subunits was found, respectively, in 14.45, 9.2 and 19.21% of neurons. The cell body diameter of most neurons containing any nAChR subunit was in the 30-40 micro m range with slightly fewer in the 20-30 micro m range. Co-localization of these alpha subunit transcripts with either CGRP or VR1 immunoreactivity ranged from approximately 5 to 7% for alpha4 and over 8% for alpha3 to 18% for alpha6. These data support the hypothesis that nicotinic agents, acting at nAChRs contained on primary sensory neurons, are capable of directly modulating the stimulated release of iCGRP. In the case of users of nicotine-containing tobacco products, this modulation could contribute to inflammatory processes within the oral cavity.

Vascular and neural mechanisms of ACh-mediated vasodilation in the forearm cutaneous microcirculation.

The relative contribution of endothelial vasodilating factors to acetylcholine (ACh)-mediated vasodilation in the forearm cutaneous microcirculation is unclear. The aims of this study were to investigate the contributions of prostanoids and cutaneous C fibers to basal cutaneous blood flow (CuBF) and ACh-mediated vasodilation. ACh was iontophoresed into the forearm, and cutaneous perfusion was measured by laser-Doppler flowmetry. To inhibit the production of prostanoids, four doses of acetylsalicylic acid (ASA; 81, 648, 972, and 1,944 mg) were administered orally. Cutaneous nerve fibers were blocked with topical anesthesia. Cyclooxygenase inhibition did not change basal CuBF or endothelium-mediated vasodilation to ACh. In contrast, ASA (972 and 1,944 mg) significantly reduced the C-fiber-mediated axon reflex in a dose-dependent fashion. Blockade of C-fiber function significantly reduced axon reflex-mediated vasodilation but did not affect basal CuBF or endothelium-dependent vasodilation. The findings suggest that prostanoids do not contribute significantly to basal CuBF or endothelium-dependent vasodilation in the forearm microcirculation. In contrast, prostanoids are mediators of the ACh-provoked axon reflex.

Cannabinoids reduce hyperalgesia and inflammation via interaction with peripheral CB1 receptors.

Central antinociceptive effects of cannabinoids have been well documented. However, relatively little is known about the peripheral effects of the cannabinoids on inflammation. In the present study, we evaluated the effects of peripherally administered cannabinoids on three indices of inflammation: carrageenan-induced thermal hyperalgesia, carrageenan-induced edema, and capsaicin-induced plasma extravasation. In addition, we determined the effect of cannabinoids on capsaicin-evoked neuropeptide release from isolated rat hindpaw skin. Our results indicate that cannabinoids produce antihyperalgesia via interaction with a peripheral CB1 receptor. Peripheral, but not systemic, administration of 0.01 ng anandamide inhibited the induction of hyperalgesia. Peripheral administration of anandamide also attenuated hyperalgesia after its development via interaction with the CB1 cannabinoid receptor subtype as indicated by its reversal with the CB1 receptor antagonist SR 141716A. Additionally, peripheral, but not systemic, administration of 0.01 ng anandamide inhibited edema. Peripherally administered cannabinoids also interacted with CB1 receptors to inhibit capsaicin-evoked plasma extravasation into the hindpaw. One potential mechanism for the anti-inflammatory actions of the cannabinoids is the inhibition of neurosecretion from the peripheral terminals of nociceptive primary afferent fibers. This hypothesis is supported by the finding that anandamide inhibited capsaicin-evoked release of calcitonin gene-related peptide from isolated hindpaw skin. Collectively, these results indicate that cannabinoids reduce inflammation via interaction with a peripheral CB1 receptor. A potential mechanism for this effect is the inhibition of neurosecretion from capsaicin-sensitive primary afferent fibers.

Peripheral CGRP release as a marker for neurogenic inflammation: a model system for the study of neuropeptide secretion in rat paw skin.

The local release of pro-inflammatory neuropeptides in the periphery has been associated with the development of neurogenic inflammation. However, there is an increasing number of reports demonstrating tissue-dependent differences regarding the mechanisms engaged by these neuropeptides to initiate and maintain the inflammatory response in the target tissue. Since skin is often involved in tissue injury, the present studies were designed to develop a model for assessing cutaneous peptide secretion as a marker for neurogenic inflammation in skin tissue. Calcitonin gene-related peptide (CGRP), as one of several neuropeptides known to be involved in neurogenic inflammation, was chosen to study capsaicin-induced effects on peripheral neurosecretion. The corial surface of the hairy skin of a rat hindlimb was superfused in vitro, and the basal and capsaicin-evoked peripheral release of immunoreactive CGRP (iCGRP) was measured using a radioimmunoassay. The main objectives of these studies were to characterize the various properties of this release including dose-dependency, exocytosis and receptor-mediation as well as the effects of acute and long-term capsaicin desensitization. Capsaicin significantly and dose-dependently increased the release of iCGRP at concentrations ranging from 3 to 300 microM. Omission of calcium ions or treatment with the competitive capsaicin receptor antagonist capsazepine completely inhibited the capsaicin-induced iCGRP release. Superfusion of the skin with 100 microM capsaicin following a conditioning stimulation with capsaicin at concentrations ranging from 0.3 to 100 microM led to an acute, dose-dependent desensitization of the CGRP response. In addition, chronic desensitization following the neonatal injection of capsaicin completely abolished the acute iCGRP response to capsaicin. The method described here should prove to be a valuable tool for the evaluation of the processes regulating the peripheral, cutaneous release of pro-inflammatory neuropeptides. This strategy, therefore, may lead to a better understanding of the mechanisms involved in the development and maintenance of neurogenic inflammation, particularly in the skin.