Skin toxicity of jet fuels: ultrastructural studies and the effects of substance P

Massive Gasoline Ingestion in a 64-Year-Old Female: An Explosive Situation

Hydrocarbons from gasoline are toxins that can affect a multitude of organ systems based on the route of chemical intoxication exposure, with a majority involving oral ingestion or inhalation. Data is still incomplete concerning the systemic complications of gasoline ingestion due in part to variability in the chemical composition of various gasoline products.

A 64-year-old female presented to her local emergency department following the ingestion of gasoline in a suicide attempt with altered mental status, hypotension, shortness of breath, tachypnea, sinus tachycardia, coarse rhonchi bilaterally, and hyperactive bowel sounds. Treatment upon admission included intravenous ampicillin/sulbactam, intubation, an intravenous fluid bolus, and ketamine to address the developing hypotension. The patient developed multiorgan failure and acute toxic encephalopathy despite medical interventions and hemodialysis. After four days, comfort care measures were initiated, and the patient passed away.

Gasoline toxicity can have a profound effect on multiple organs based on the chemical properties and the route of exposure. These sequelae can be monitored through patient symptoms as well as radiologic imaging. Early supportive therapy and decontamination are vital in decreasing the morbidity and mortality associated with gasoline ingestion.

A Case Series of Chemical Dermal Injury Requiring Operative Intervention after Prolonged Dermal Methylene Chloride Exposure

INTRODUCTION

Methylene chloride, also known as dichloromethane, is a volatile hydrocarbon used in paint strippers and removers. Toxicity from methylene chloride may include narcosis and elevated carbon monoxide (CO) levels. Significant injury to the skin can occur after prolonged exposure to methylene chloride and other hydrocarbon-based solvents causing a chemical dermal injury.

CASE REPORT

This case series describes three male patients with prolonged exposure to a methylene chloride-containing paint remover to the bilateral hands with two of the three patients requiring transfer to a tertiary burn center and operative intervention. The clinical significance and impressive resolution of dermal injury from prolonged methylene chloride exposure are highlighted with detailed images and a literature review.

DISCUSSION

Chemical dermal injury secondary to methylene chloride exposure likely results from destruction of lipids within the epidermis and dermis and direct chemical injury. Prolonged exposure to skin can result in clinically important injury that requires management by a burn specialist and may necessitate operative intervention. The severity of the dermal injury can range from severe to mild and should be considered by a clinician after skin exposure to hydrocarbons.

Effects and mechanisms of kerosene use-related toxicity

Kerosene is a heterogeneous hydrocarbon substance that continues to find many uses worldwide due to its economic viability and ease of availability. In spite of kerosene's many uses, it is known to cause harm to various body organs and systems. Major affected body organs/systems are the pulmonary system, central nervous system, cardiovascular system, the skin, immune system and liver. This review discusses the various kerosene-mediated adverse health effects and possible mechanisms by which kerosene is likely to inflict such effects. These mechanisms are quite varied and include induction of inflammation, loss of effectiveness of pulmonary surfactants, hypoxia, production of highly reactive oxidative metabolites, extraction of endogenous epidermal and membrane lipids, necrosis, hormonal and enzymatic levels changes, and immunosuppression. Understanding of the above will allow for proper relevant policy formulation and targeted kerosene-mediated morbidity and mortality preventive and management initiatives.

In Vitro Pro-inflammatory Regulatory role of Substance P in Alveolar Macrophages and Type II Pneumocytes after JP-8 Exposure

The effects of JP-8 on pro-inflammatory cytokine interleukin (IL)-1alpha,beta and nitric oxide (NO) secretion as well as the role of substance P (SP) in these processes were examined in cultured alveolar macrophages (AM), type II epithelial cells (AIIE), and AM/AIIE co-cultures. Exposure of AM to JP-8 for 24 hr exhibited release of IL-1alpha,beta, whereas exposure to AIIE showed a concentration-dependent NO overproduction. Data indicate that there are cell-dependent inflammatory mechanisms responsible for the actual level of JP-8 exposure in alveoli. However, treatment with substance P significantly attenuated JP-8 induced the IL-1alpha,beta secretion. This finding was confirmed by using [Sar(9) Met (O(2))(11)] SP (10(- 10) M), an agonist of substance P, suggesting that substance P may have signal pathway(s) to AM in the inflammatory response mediated by IL-1. Moreover, AM/AIIE co-culture obviously reduced NO overproduction observed in AIIE alone, suggesting that there may be cell interactions or communications between AM and AIIE in response to the JP-8 exposure.

Langendorff heart: a model system to study cardiovascular effects of engineered nanoparticles

Engineered nanoparticles (ENPs) are produced and used in increasing quantities for industrial products, food, and drugs. The fate of ENPs after usage and impact on health is less known. Especially as air pollution, suspended nanoparticles have raised some attention, causing diseases of the lung and cardiovascular system. Human health risks may arise from inhalation of ENPs with associated inflammation, dispersion in the body, and exposure of vulnerable organs (e.g., heart, brain) and tissues with associated toxicity. However, underlying mechanisms are largely unknown. Furthermore future use of ENPs in therapeutic applications is being researched. Therefore knowledge about potential cardiovascular risks due to exposure to ENPs is highly demanded, but there are no established biological testing models yet. Therefore, we established the isolated beating heart (Langendorff heart) as a model system to study cardiovascular effects of ENPs. This model enables observation and analysis of electrophysiological parameters over a minimal time period of 4 h without influence by systemic effects and allows the determination of stimulated release of substances under influence of ENPs. We found a significant dose and material dependent increase in heart rate accompanied by arrhythmia evoked by ENPs made of flame soot (Printex 90), spark discharge generated soot, anatas (TiO(2)), and silicon dioxide (SiO(2)). However, flame derived SiO(2) (Aerosil) and monodisperse polystyrene lattices exhibited no effects. The increase in heart rate is assigned to catecholamine release from adrenergic nerve endings within the heart. We propose the isolated Langendorff heart and its electrophysiological characterization as a suitable test model for studying cardiovascular ENP toxicity.

Jet fuel toxicity: skin damage measured by 900-MHz MRI skin microscopy and visualization by 3D MR image processing

The toxicity of jet fuels was measured using noninvasive magnetic resonance microimaging (MRM) at 900-MHz magnetic field. The hypothesis was that MRM can visualize and measure the epidermis exfoliation and hair follicle size of rat skin tissue due to toxic skin irritation after skin exposure to jet fuels. High-resolution 900-MHz MRM was used to measure the change in size of hair follicle, epidermis thickening and dermis in the skin after jet fuel exposure. A number of imaging techniques utilized included magnetization transfer contrast (MTC), spin-lattice relaxation constant (T1-weighting), combination of T2-weighting with magnetic field inhomogeneity (T2*-weighting), magnetization transfer weighting, diffusion tensor weighting and chemical shift weighting. These techniques were used to obtain 2D slices and 3D multislice-multiecho images with high-contrast resolution and high magnetic resonance signal with better skin details. The segmented color-coded feature spaces after image processing of the epidermis and hair follicle structures were used to compare the toxic exposure to tetradecane, dodecane, hexadecane and JP-8 jet fuels. Jet fuel exposure caused skin damage (erythema) at high temperature in addition to chemical intoxication. Erythema scores of the skin were distinct for jet fuels. The multicontrast enhancement at optimized TE and TR parameters generated high MRM signal of different skin structures. The multiple contrast approach made visible details of skin structures by combining specific information achieved from each of the microimaging techniques. At short echo time, MRM images and digitized histological sections confirmed exfoliated epidermis, dermis thickening and hair follicle atrophy after exposure to jet fuels. MRM data showed correlation with the histopathology data for epidermis thickness (R(2)=0.9052, P<.0002) and hair root area (R(2)=0.88, P<.0002). The toxicity of jet fuels on skin structures was in the order of tetradecane>hexadecane>dodecane. The method showed a sensitivity of 87.5% and a specificity of 75%. By MR image processing, different color-coded skin structures were extracted and 3D shapes of the epidermis and hair follicle size were compared. In conclusion, high-resolution MRM measured the change in skin epidermis and hair follicle size due to toxicity of jet fuels. MRM offers a three-dimensional spatial visualization of the change in skin structures as a method of toxicity evaluation and for comparison of jet fuels.

Asian dust storm particles induce a broad toxicological transcriptional program in human epidermal keratinocytes

Exposure to airborne dust particles originated from seasonal Asian dust storms in Chinese and Mongolian deserts results in increased incidence of a range of diseases including asthma, contact dermatitis and conjunctivitis. The areas affected by Asian dust particles extend from East China to the west coast of North America. In order to study toxicological mechanisms in human skin, we evaluated the effects of dust particles collected during Asian dust storms (Asian dust particles) on gene expression in human epidermal keratinocytes (HEK). In HEK, exposure to Asian dust particles significantly increased gene expressions of cytochrome P450 1A1 (CYP1A1), CYP1A2, and CYP1B1, which is an indication of aryl hydrocarbon receptor (AHR) activation. In addition, Asian dust particles increased gene transcription of the cytokines IL-6, IL-8, and GM-CSF, which have broad pro-inflammatory and immunomodulatory properties. Asian dust particles significantly up-regulated expression of caspase 14 in HEK, suggesting that Asian dust particles directly affect keratinocyte differentiation. We also demonstrated that protein extract of pollen, a material frequently adsorbed onto Asian dust particles, potentially contributes to the increased transcription of IL-6, CYP1A1, CYP1A2, and CYP1B1. Taken together, these studies suggest that Asian dust particles can exert toxicological effects on human skin through the activation of the cellular detoxification system, the production of pro-inflammatory and immunomodulatory cytokines, and changes in the expression of proteins essential in normal epidermal differentiation.

Evaluation of silver nanoparticle toxicity in skin in vivo and keratinocytes in vitro

INTRODUCTION

Products using the antimicrobial properties of silver nanoparticles (Ag-nps) may be found in health and consumer products that routinely contact skin.

OBJECTIVES

This study was designed to assess the potential cytotoxicity of Ag-nps in human epidermal keratinocytes (HEKs) and their inflammatory and penetrating potential into porcine skin in vivo.

MATERIALS AND METHODS

We used eight different Ag-nps in this study [unwashed/uncoated (20, 50, and 80 nm particle diameter), washed/uncoated (20, 50, and 80 nm), and carbon-coated (25 and 35 nm)]. Skin was dosed topically for 14 consecutive days. HEK viability was assessed by MTT, alamarBlue (aB), and CellTiter 96 AQueous One (96AQ). Release of the proinflammatory mediators interleukin (IL)-1beta, IL-6, IL-8, IL-10, and tumor necrosis factor-alpha (TNF-alpha) were measured.

RESULTS

The effect of the unwashed Ag-nps on HEK viability after a 24-hr exposure indicated a significant dose-dependent decrease (p < 0.05) at 0.34 microg/mL with aB and 96AQ and at 1.7 microg/mL with MTT. However, both the washed Ag-nps and carbon-coated Ag-nps showed no significant decrease in viability at any concentration assessed by any of the three assays. For each of the unwashed Ag-nps, we noted a significant increase (p < 0.05) in IL-1beta, IL-6, IL-8, and TNF-alpha concentrations. We observed localization of all Ag-nps in cytoplasmic vacuoles of HEKs. Macroscopic observations showed no gross irritation in porcine skin, whereas microscopic and ultrastructural observations showed areas of focal inflammation and localization of Ag-nps on the surface and in the upper stratum corneum layers of the skin.

CONCLUSION

This study provides a better understanding Ag-nps safety in vitro as well as in vivo and a basis for occupational and risk assessment. Ag-nps are nontoxic when dosed in washed Ag-nps solutions or carbon coated.

Evaluation of EpiDerm full thickness-300 (EFT-300) as an in vitro model for skin irritation: studies on aliphatic hydrocarbons

The aim of this study was to understand the skin irritation effects of saturated aliphatic hydrocarbons (HCs), C9-C16, found jet fuels using in vitro 3-dimensional EpiDerm full thickness-300 (EFT-300) skin cultures. The EFT-300 cultures were treated with 2.5microl of HCs and the culture medium and skin samples were collected at 24 and 48h to measure the release of various inflammatory biomarkers (IL-1alpha, IL-6 and IL-8). To validate the in vitro results, in vivo skin irritation studies were carried out in hairless rats by measuring trans epidermal water loss (TEWL) and erythema following un-occlusive dermal exposure of HCs for 72h. The MTT tissue viability assay results with the EFT-300 tissue show that 2.5microl/tissue ( approximately 4.1microl/cm(2)) of the HCs did not induce any significant changes in the tissue viability for exposure times up to 48h of exposure. Microscopic observation of the EFT-300 cross-sections indicated that there were no obvious changes in the tissue morphology of the samples at 24h, but after 48h of exposure, tridecane, tetradecane and hexadecane produced a slight thickening and disruption of stratum corneum. Dermal exposures of C12-C16 HCs for 24h significantly increased the expression of IL-1alpha in the skin as well as in the culture medium. Similarly, dermal exposure of all HCs for 24h significantly increased the expression of interleukin-6 (IL-6) and IL-8 in the skin as well as in the culture medium in proportion to the HC chain length. As the exposure time increased to 48h, IL-6 concentrations increased 2-fold compared to the IL-6 values at 24h. The in vivo skin irritation data also showed that both TEWL and erythema scores increased with increased HCs chain length (C9-C16). In conclusion, the EFT-300 showed that the skin irritation profile of HCs was in the order of C9C10C11C12<C13 approximately C14 approximately C16 and that the tissue was an excellent in vitro model to predict in vivo irritation and to understand the structural activity relationship of HCs.

Expression Profiling of Human Epidermal Keratinocyte Response Following 1-Minute JP-8 Exposure

The cDNA microarray analysis of 9600 expressed sequence tags was performed to examine the gene expression changes in human epidermal keratinocytes after 1-minute JP-8 exposure; 151 genes were identified as JP-8 responsive and classified into 8 clusters by self organization map. Genes involved in basal transcription and translations were up-regulated, whereas genes related to DNA repair, metabolism, and keratin were mostly down-regulated. Genes encoded for growth factors, apoptosis, signal transduction, and adhesion were also altered. These results indicated that human keratinocyte responds to a single dose of JP-8 insult and revealed several cellular processes previously not associated with jet fuel exposure.

Inhibition of jet fuel aliphatic hydrocarbon induced toxicity in human epidermal keratinocytes

Jet propellant (JP)-8, the primary jet fuel used by the U.S. military, consists of hydrocarbon-rich kerosene base commercial jet fuel (Jet-A) plus additives DC1-4A, Stadis 450 and diethylene glycol monomethyl ether. Human epidermal keratinocytes (HEK) were exposed to JP-8, aliphatic hydrocarbon (HC) fuel S-8 and aliphatic HC pentadecane (penta), tetradecane (tetra), tridecane (tri) and undecane (un) for 5 min. Additional studies were conducted with signal transduction pathway blockers parthenolide (P; 3.0 microm), isohelenin (I; 3.0 microm), SB 203580 (SB; 13.3 microm), substance P (SP; 3.0 microm) and recombinant human IL-10 (rHIL-10; 10 ng ml(-1)). In the absence of inhibitors, JP-8 and to a lesser extent un and S-8, had the greatest toxic effect on cell viability and inflammation suggesting, as least in vitro, that synthetic S-8 fuel is less irritating than the currently used JP-8. Each inhibitor significantly (P < 0.05) decreased HEK viability. DMSO, the vehicle for P, I and SB, had a minimal effect on viability. Overall, IL-8 production was suppressed at least 30% after treatment with each inhibitor. Normalizing data relative to control indicate which inhibitors suppress HC-mediated IL-8 to control levels. P was the most effective inhibitor of IL-8 release; IL-8 was significantly decreased after exposure to un, tri, tetra and penta but significantly increased after JP-8 exposure compared with controls. Inhibitors were not effective in suppressing IL-8 release in JP-8 exposures to control levels. This study shows that inhibiting NF-kappa B, which appears to play a role in cytokine production in HC-exposed HEK in vitro, may reduce the inflammatory effect of HC in vivo.

Pathogenesis of permeability barrier abnormalities in the ichthyoses: inherited disorders of lipid metabolism

Many of the ichthyoses are associated with inherited disorders of lipid metabolism. These disorders have provided unique models to dissect physiologic processes in normal epidermis and the pathophysiology of more common scaling conditions. In most of these disorders, a permeability barrier abnormality "drives" pathophysiology through stimulation of epidermal hyperplasia. Among primary abnormalities of nonpolar lipid metabolism, triglyceride accumulation in neutral lipid storage disease as a result of a lipase mutation provokes a barrier abnormality via lamellar/nonlamellar phase separation within the extracellular matrix of the stratum corneum (SC). Similar mechanisms account for the barrier abnormalities (and subsequent ichthyosis) in inherited disorders of polar lipid metabolism. For example, in recessive X-linked ichthyosis (RXLI), cholesterol sulfate (CSO(4)) accumulation also produces a permeability barrier defect through lamellar/nonlamellar phase separation. However, in RXLI, the desquamation abnormality is in part attributable to the plurifunctional roles of CSO(4) as a regulator of both epidermal differentiation and corneodesmosome degradation. Phase separation also occurs in type II Gaucher disease (GD; from accumulation of glucosylceramides as a result of to beta-glucocerebrosidase deficiency). Finally, failure to assemble both lipids and desquamatory enzymes into nascent epidermal lamellar bodies (LBs) accounts for both the permeability barrier and desquamation abnormalities in Harlequin ichthyosis (HI). The barrier abnormality provokes the clinical phenotype in these disorders not only by stimulating epidermal proliferation, but also by inducing inflammation.

Partitioning behavior of aromatic components in jet fuel into diverse membrane-coated fibers

Jet fuel components are known to partition into skin and produce occupational irritant contact dermatitis (OICD) and potentially adverse systemic effects. The purpose of this study was to determine how jet fuel components partition (1) from solvent mixtures into diverse membrane-coated fibers (MCFs) and (2) from biological media into MCFs to predict tissue distribution. Three diverse MCFs, polydimethylsiloxane (PDMS, lipophilic), polyacrylate (PA, polarizable), and carbowax (CAR, polar), were selected to simulate the physicochemical properties of skin in vivo. Following an appropriate equilibrium time between the MCF and dosing solutions, the MCF was injected directly into a gas chromatograph/mass spectrometer (GC-MS) to quantify the amount that partitioned into the membrane. Three vehicles (water, 50% ethanol-water, and albumin-containing media solution) were studied for selected jet fuel components. The more hydrophobic the component, the greater was the partitioning into the membranes across all MCF types, especially from water. The presence of ethanol as a surrogate solvent resulted in significantly reduced partitioning into the MCFs with discernible differences across the three fibers based on their chemistries. The presence of a plasma substitute (media) also reduced partitioning into the MCF, with the CAR MCF system being better correlated to the predicted partitioning of aromatic components into skin. This study demonstrated that a single or multiple set of MCF fibers may be used as a surrogate for octanol/water systems and skin to assess partitioning behavior of nine aromatic components frequently formulated with jet fuels. These diverse inert fibers were able to assess solute partitioning from a blood substitute such as media into a membrane possessing physicochemical properties similar to human skin. This information may be incorporated into physiologically based pharmacokinetic (PBPK) models to provide a more accurate assessment of tissue dosimetry of related toxicants.

Cyclic tensile strain increases interactions between human epidermal keratinocytes and quantum dot nanoparticles

The effects of quantum dots (QD) on cell viability have gained increasing interest due to many recent developments utilizing QD for pharmaceutical and biomedical applications. The potential use of QD nanoparticles as diagnostic, imaging, and drug delivery agents has raised questions about their potential for cytotoxicity. The objective of this study was to investigate the effects of applied strain on QD uptake by human epidermal keratinocytes (HEK). It was hypothesized that introduction of a 10% average strain to cell cultures would increase QD uptake. HEK were seeded at a density of 150,000 cells/mL on collagen-coated Flexcell culture plates (Flexcell Intl.). QD were introduced at a concentration of 3 nM and a 10% average strain was applied to the cells. After 4h of cyclic strain, the cells were examined for cell viability, QD uptake, and cytokine production. The results indicate that addition of strain results in an increase in cytokine production and QD uptake, resulting in irritation and a negative impact on cell viability. Application of physiological load conditions can increase cell membrane permeability, thereby increasing the concentration of QD nanoparticles in cells.

Gene expression and target tissue dose in the rat epidermis after brief JP-8 and JP-8 aromatic and aliphatic component exposures

Exposures of jet propulsion fuel 8 (JP-8) to human and laboratory animal skin have resulted in skin irritation. JP-8 is a mixture of aromatic and aliphatic hydrocarbons, which in some cases have also been shown to be irritating to the skin. In an attempt to determine if aromatic or aliphatic components could mimic the JP-8-induced gene expression response, we exposed rats to JP-8, undecane (UND), tetradecane (TET), trimethylbenzene (TMB), and dimethylnaphthalene (DMN) for 1 h and examined the epidermis to characterize the gene expression response. We also measured the concentrations of the JP-8 components in the epidermis with gas chromatography/mass spectrometry after 1-h exposures to JP-8 and pure components to determine if differences in potency could be identified. Changes in gene expression, compared to sham treatment, were studied with microarray techniques and analyzed for changes in gene ontology categories. UND and TMB exposures caused the greatest number of changes in transcript levels compared to DMN and TET. When only the specific functional and signaling pathways that were changed by JP-8 were considered, these pathways were nearly all activated by the components, but to different extents. After pure component exposures, the epidermal concentrations of the components showed no significant differences, although the differences in magnitude of either total or pathway-specific gene expression differed by a factor of 10-fold. We conclude that no single component that we studied mimicked the gene expression resulting from the JP-8 exposure but that UND had the most similar responses. These data suggest that there are differences in potency between the four components studied.

Dermal lesions after post mortem petrol-exposure

The effect of post mortem contact of the skin with petrol was investigated in 18 corpses with exposure times between 10 min and 24 h. The earliest onset of skin changes was observed within 2 h of exposure. They consisted of swelling and wrinkling with detachment of the upper layers of the skin (positive Nikolski's sign). Histologically the lesions appeared as non-vital acantholyses located in the prickle-cell layer with formation of intra-epidermal bullae. An influence of age and sex could be excluded, the earlier onset of lesions at 22 degrees C than at 4 degrees C was not statistically significant. These findings prove that post mortem petrol exposure may lead to dermal lesions.

Effects of brief cutaneous JP-8 jet fuel exposures on time course of gene expression in the epidermis

The jet fuel jet propulsion fuel 8 (JP-8) has been shown to cause an inflammatory response in the skin, which is characterized histologically by erythema, edema, and hyperplasia. Studies in laboratory animal skin and cultured keratinocytes have identified a variety of changes in protein levels related to inflammation, oxidative damage, apoptosis, and cellular growth. Most of these studies have focused on prolonged exposures and subsequent effects. In an attempt to understand the earliest responses of the skin to JP-8, we have investigated changes in gene expression in the epidermis for up to 8 h after a 1-h cutaneous exposure in rats. After exposure, we separated the epidermis from the rest of the skin with a cryotome and isolated total mRNA. Gene expression was studied with microarray techniques, and changes from sham treatments were analyzed and characterized. We found consistent twofold increases in gene expression of 27 transcripts at 1, 4, and 8 h after the beginning of the 1-h exposure that were related primarily to structural proteins, cell signaling, inflammatory mediators, growth factors, and enzymes. Analysis of pathways changed showed that several signaling pathways were increased at 1 h and that the most significant changes at 8 h were in metabolic pathways, many of which were downregulated. These results confirm and expand many of the previous molecular studies with JP-8. Based on the 1-h changes in gene expression, we hypothesize that the trigger of the JP-8-induced, epidermal stress response is a physical disruption of osmotic, oxidative, and membrane stability which activates gene expression in the signaling pathways and results in the inflammatory, apoptotic, and growth responses that have been previously identified.

Barrier dysfunction and pathogenesis of neutral lipid storage disease with ichthyosis (Chanarin-Dorfman syndrome)

Neutral lipid storage disease with ichthyosis (NLSDI; Chanarin-Dorfman syndrome) is an ichthyosiform syndrome, often associated with mutations in a lipid hydrolase, CGI-58. The presence of oil red O-positive, neutral lipid droplets in tissue biopsies, and/or in leukocytes on blood smears, coupled with a constellation of multisystem abnormalities and a pruritic ichthyosiform erythroderma, are together diagnostic of NLSDI. We investigated the pathogenesis of the ichthyosiform erythroderma in patients from three unrelated kindreds with a clinical diagnosis of NLSDI. Basal permeability barrier function and stratum corneum (SC) integrity were abnormal, but barrier recovery rates were faster than normal, as in atopic dermatitis. The basal barrier abnormality was linked to the secretion of lipid micro-inclusions, first segregated within lamellar bodies (LB), which then form a non-lamellar phase within the SC interstices, shown by combined ruthenium tetroxide post-fixation and lipid-retaining resin-white embedding. With colloidal lanthanum nitrate perfusion, excess water/solute movement was restricted to the SC interstices, and further localized to non-lamellar domains. Phase separation of excess stored lipid provides a unifying pathogenic mechanism not only for NLSDI, but also in several other inherited ichthyosiform disorders of lipid metabolism, such as recessive X-linked ichthyosis and type 2 Gaucher's disease.

Toxicity of jet fuel aliphatic and aromatic hydrocarbon mixtures on human epidermal Keratinocytes: evaluation based on in vitro cytotoxicity and interleukin-8 release

Jet fuels are complex mixtures of aliphatic (ALI) and aromatic (ARO) hydrocarbons that vary significantly in individual cytotoxicity and proinflammatory activity in human epidermal keratinocytes (HEK). In order to delineate the toxicological interactions among individual hydrocarbons in a mixture and their contributions to cutaneous toxicity, nine ALI and five ARO hydrocarbons were each divided into five (high/medium/low cytotoxic and strong/weak IL-8 induction) groups and intra/inter-mixed to assess for their mixture effects on HEK mortality and IL-8 release. Addition of single hydrocarbon to JP-8 fuel was also evaluated for their changes in fuel dermatotoxicity. The results indicated that when hydrocarbons were mixed, HEK mortality and IL-8 release were not all predictable by their individual ability affecting these two parameters. The lowest HEK mortality (7%) and the highest IL-8 production were induced with mixtures including high cytotoxic and weak IL-8 inductive ARO hydrocarbons. Antagonistic reactions not consistently correlated with ALI carbon chain length and ARO structure were evident and carried different weight in the overall mixture toxicities. Single addition of benzene, toluene, xylene or ethylbenzene for up to tenfold in JP-8 did not increase HEK mortality while single addition of ALI hydrocarbons exhibited dose-related differential response in IL-8. In an all ALI environment, no single hydrocarbon is the dominating factor in the determination of HEK cytotoxicity while deletion of hexadecane resulted in a 2.5-fold increase in IL-8 production. Overall, decane, undecane and dodecane were the major hydrocarbons associated with high cytotoxicity while tetradecane, pentadecane and hexadecane were those which had the greatest buffering effect attenuating dermatotoxicity. The mixture effects must be considered when evaluating jet fuel toxicity to HEK.

Topical exposure to carbon disulfide induces epidermal permeability alterations in physiological and pathological changes

Carbon disulfide (CS2) has been suggested its possible skin toxicity. Neither a dose-response relationship nor any mechanism of CS2-exposure regarding epidermal permeability alterations has been postulated. The objectives of this study were to evaluate the dose-dependent association and the pathological changes with CS2 topically applied to mouse epidermis. Four concentrations of CS2 (0% (controls), 10%, 15%, and 20% in ethanol) were topically applied to a 1.8 cm2 area of the lateral abdomen of female nude mice for 10 min. Time-series transepidermal water loss (TEWL) profile, morphological examinations by both light microscopy (hematoxylin/eosin stain and Nile Red stain) and electronic microscopy, and lipid analysis by high performance thin-layer chromatography (HPTLC) were used to evaluate the epidermal impairment. We found no recovery occurred within 72 h exposure to 20% CS2 in contrast to substantial recovery found in 10% and 15% CS2-exposure. Clear dose-dependent fashions were shown in TEWL elevations, recovery retardation, and lipid extraction across the ethanol (control), 10%, 15%, and 20% CS2 exposures. Two mechanistic pathways were raised to account for CS2-induced epidermal alterations: intercellular lipid depletion and keratinocyte damage. A study with different test animal species is warranted owing to the discrepancies in epidermis between nude mice and other species.

Effect of JP-8 jet fuel exposure on protein expression in human keratinocyte cells in culture

Dermal exposure to jet fuel is a significant occupational hazard. Previous studies have investigated its absorption and disposition in skin, and the systemic biochemical and immunotoxicological sequelae to exposure. Despite studies of JP-8 jet fuel components in murine, porcine or human keratinocyte cell cultures, proteomic analysis of JP-8 exposure has not been investigated. This study was conducted to examine the effect of JP-8 administration on the human epidermal keratinocyte (HEK) proteome. Using a two-dimensional electrophoretic approach combined with mass spectrometric-based protein identification, we analyzed protein expression in HEK exposed to 0.1% JP-8 in culture medium for 24 h. JP-8 exposure resulted in significant expression differences (p<0.02) in 35 of the 929 proteins matched and analyzed. Approximately, a third of these alterations were increased in protein expression, two-thirds declined with JP-8 exposure. Peptide mass fingerprint identification of effected proteins revealed a variety of functional implications. In general, altered proteins involved endocytotic/exocytotic mechanisms and their cytoskeletal components, cell stress, and those involved in vesicular function.

Pre-treatment effects of trichloroethylene on the dermal absorption of the biocide, triazine

Triazine is often added to cutting-fluid formulations in the metal-machining industry as a preservative. Trichloroethylene (TCE) is a solvent used for cleaning the cutting fluid or oil from the metal product. The purpose of this study was to examine the effect of TCE on the dermal absorption of triazine in an in vitro flow-through diffusion cell system. Skin sections were dosed topically with aqueous mixtures containing mineral oil or polyethylene glycol (PEG) spiked with (14)C-triazine. Some skin sections were simultaneously exposed to TCE while other skin sections were pre-treated with TCE daily for 4 days in vivo and then exposed to these mixtures in vitro. TCE pre-treatment almost doubled triazine permeability, but this pre-treatment had no effect on triazine diffusivity. The pre-treatment effects of TCE on triazine permeability appear to be more important in PEG-based mixtures than in the mineral oil-based mixtures. Simultaneous single exposure to TCE had little or no effect on triazine absorption. TCE absorption was significantly less than triazine absorption; however, cutting fluid additives had a more significant effect on TCE absorption than on triazine absorption. In summary, this study demonstrated that TCE pre-treatment can significantly alter the dermal permeability to triazine, and workers who are chronically exposed to this or similar cleansers may be at increased risk of absorbing related skin irritants.

Comparative in vivo toxicity of topical JP-8 jet fuel and its individual hydrocarbon components: identification of tridecane and tetradecane as key constituents responsible for dermal irritation

Despite widespread exposure to military jet fuels, there remains a knowledge gap concerning the actual toxic entities responsible for irritation observed after topical fuel exposure. The present studies with individual hydrocarbon (HC) constituents of JP-8 jet fuel shed light on this issue. To mimic occupational scenarios, JP-8, 8 aliphatic HC (nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane) and 6 aromatic HC (ethyl benzene, o-xylene, trimethyl benzene, cyclohexyl benzene, naphthalene, dimethyl naphthalene) soaked cotton fabrics were topically exposed to pigs for 1 day and with repeated daily exposures for 4 days. Erythema, epidermal thickness, and epidermal cell layers were quantitated. No erythema was noted in 1-day in vivo HC exposures but significant erythema was observed in 4-day tridecane, tetradecane, pentadecane, and JP-8 exposed sites. The aromatic HCs did not produce any macroscopic lesions in 1 or 4 days of in vivo exposures. Morphological observations revealed slight intercellular and intracellular epidermal edema in 4-day exposures with the aliphatic HCs. Epidermal thickness and number of cell layers significantly increased (p < 0.05) in tridecane, tetradecane, pentadecane, and JP-8-treated sites. No significant differences were observed in the aromatic HC-exposed sites. Subcorneal microabscesses containing inflammatory cells were observed with most of the long-chain aliphatic HCs and JP-8 in 4-day exposures. Ultrastructural studies depicted that jet fuel HC-induced cleft formation within intercellular lipid lamellar bilayers of the stratum corneum. The degree of damage to the skin was proportional to the length of in vivo HC exposures. These data coupled with absorption and toxicity studies of jet fuel HC revealed that specific HCs (tridecane and tetradecane) might be the key constituents responsible for jet fuel-induced skin irritation.

Effect of in vivo jet fuel exposure on subsequent in vitro dermal absorption of individual aromatic and aliphatic hydrocarbon fuel constituents

The percutaneous absorption of topically applied jet fuel hydrocarbons (HC) through skin previously exposed to jet fuel has not been investigated, although this exposure scenario is the occupational norm. Pigs were exposed to JP-8 jet fuel-soaked cotton fabrics for 1 and 4 d with repeated daily exposures. Preexposed and unexposed skin was then dermatomed and placed in flow-through in vitro diffusion cells. Five cells with exposed skin and four cells with unexposed skin were dosed with a mixture of 14 different HC consisting of nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, ethyl benzene, o-xylene, trimethyl benzene (TMB), cyclohexyl benzene (CHB), naphthalene, and dimethyl naphthalene (DMN) in water + ethanol (50:50) as diluent. Another five cells containing only JP-8-exposed skin were dosed solely with diluent in order to determine the skin retention of jet fuel HC. The absorption parameters of flux, diffusivity, and permeability were calculated for the studied HC. The data indicated that there was a two-fold and four-fold increase in absorption of specific aromatic HC like ethyl benzene, o-xylene, and TMB through 1- and 4-dJP-8 preexposed skin, respectively. Similarly, dodecane and tridecane were absorbed more in 4-d than 1-dJP-8 preexposed skin experiments. The absorption of naphthalene and DMN was 1.5 times greater than the controls in both 1- and 4-d preexposures. CHB, naphthalene, and DMN had significant persistent skin retention in 4-d preexposures as compared to 1-d exposures that might leave skin capable of further absorption several days postexposure. The possible mechanism of an increase in HC absorption in fuel preexposed skin may be via lipid extraction from the stratum corneum as indicated by Fourier transform infrared (FTIR) spectroscopy. This study suggests that the preexposure of skin to jet fuel enhances the subsequent in vitro percutaneous absorption of HC, so single-dose absorption data for jet fuel HC from naive skin may not be optimal to predict the toxic potential for repeated exposures. For certain compounds, persistent absorption may occur days after the initial exposure.