Center for Chemical Toxicology Research and Pharmacokinetics (CCTRP), North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27606
Received February 26, 2002; accepted April 29, 2002
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ABSTRACT |
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Key Words: keratinocytes; aliphatic hydrocarbons; cytotoxicity; interleukin-8; jet fuels.
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INTRODUCTION |
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Aliphatic hydrocarbons are the primary hydrocarbon components (81%) of jet fuels, and exhibit a broad range of carbon chain length (9% C8C9, 65% C10C14, and 7% C15C17). Some studies suggest that they are also more likely to be sequestered in the epidermis than aromatic hydrocarbons (Baynes et al., 2000; McDougal et al., 2000
; Riviere et al., 1999
). Previous studies in our laboratory have suggested that the hydrocarbons common to Jet A, JP-8, and JP8-100 fuels may be responsible for the proinflammatory responses seen in the skin (Allen et al., 2000
; Monteiro-Riviere et al., 2001
).
Skin irritation usually has an inflammatory component. Different chemical irritants can trigger different inflammatory processes initiated by different proinflammatory cytokines (Nickoloff, 1991). Among them, IL-8 has been shown to increase significantly in response to a variety of chemical irritants (Effendy et al., 2000
) and osmotic and oxidative stressors (Terunuma et al., 2001
) and UV irradiation (Clydesdale et al., 2001
), following the activation of primary proinflammatory cytokines interleukin-1 (IL-1a, IL-1b) and tumor necrosis factor-
(TNF-
); (Corsini and Galli, 2000
). The nonspecific nature of IL-8 as a general mediator, inducible by various external stimuli, makes it an ideal biomarker to assess chemical irritants that possess an inflammatory component. We have previously demonstrated IL-8 and TNF-
responses by low levels (0.01%) of jet fuels (Allen et al., 2000
, 2001b
) and jet fuel components (Allen et al., 2001a
) in an in vitro model. In these studies, IL-8 was more consistently released than TNF-
by human epidermal keratinocytes (HEK; Allen et al., 2001b
). The release of other secondary cytokines (IL-4, IL-6, and granulocyte-macrophage colony-stimulating factor, GM-CSF) in response to jet fuel exposure have not been well studied. IL-8 was selected as the biomarker of choice, over the other secondary cytokines, for the assessment of early inflammatory responses in HEK cells exposed directly to aliphatic hydrocarbons.
Although the primary concerns regarding the skin toxicity of jet fuels is for extended and repeated exposures, such exposures occur typically at concentrations well below the permissible exposure limits. It is not well documented whether high concentrations and acute exposure would result in similar or unexpected skin toxicity (Harris et al., 2000). In addition, in vitro dermatological studies usually use vehicles such as DMSO (Dudley et al., 2001
), ethanol (Allen et al., 2001b
; Grant et al., 2000
; Rosenthal et al., 2001
), and cyclodextrin (Allen et al., 2001a
) in order to solubilize the lipophilic hydrocarbons into the media or dosing solution. The irritant nature of these vehicles often confounds the interpretation of direct cellular toxicity in the skin.
The objective of this study was to examine the effects of neat aliphatic hydrocarbon exposure on HEK cytotoxicity and IL-8 production as a biomarker of cutaneous irritation. The elimination of the vehicle allows for the intrinsic toxicity of these aliphatic hydrocarbons to be evaluated independently. In order to further elucidate which specific jet fuel hydrocarbon(s) are responsible for the dermatotoxicity, and whether carbon chain length is a contributing factor to which the type of toxicity and/or the degree of toxicity are exhibited, 10 aliphatic hydrocarbons in the carbon range of 6 to 16 (Table 1), representing the major aliphatic hydrocarbon clusters found in jet fuels (Basak et al., 2000
), were investigated for their proinflammatory and cytotoxic effects to HEK.
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MATERIALS AND METHODS |
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Cell culture and dosing regimen.
Cryopreserved adult normal human epidermal keratinocytes (approximately 260K cells/vial) were purchased from Clonetics Corp. (San Diego, CA) and passage on to three 75-cm2 culture flasks, each containing 15 ml of serum-free keratinocyte growth medium (KGM-2; from keratinocytes basal media supplemented with 0.1 ng/ml human epidermal growth factor, 5 µg/ml insulin, 0.4% bovine pituitary extract, 0.1% hydrocortisone, 0.1% transferrin, 0.1% epinephrine, and 50 µg/ml gentamicin/50 ng/ml amphotericin-B). The culture flasks were maintained in a humidified incubator at 37°C with a 95% O2/5% CO2 atmosphere. After reaching 7080% confluency, the keratinocytes were harvested and plated immediately in 96-well tissue culture-treated plastic ware (Corning, Acton, MA) at a density of 68 K cells/well. Once HEK were grown to 80% confluency in the plates, the media was aspirated from each well and the cells were dosed (in triplicate) with 40 µl/well of designated test compound for various lengths of predetermined exposure times (1, 5, or 15 min). The three exposure times were chosen based on a pilot study to evaluate the cell mortality as a function of exposure times. For the purpose of the study, the exposure times were determined (1) to simulate acute exposure where an accidental spill occurs (1 min), (2) to find the longest exposure time without significantly causing cell death (15 min), and (3) to find an optimal exposure time where the cells would maintain approximately 50% viability after exposure to most aliphatic hydrocarbons, so that cytokine production could be reliably evaluated (5 min). The exposure was terminated by aspirating the test compounds with a vacuum. This was immediately followed with a rinse of 100 µl/well KGM-2 medium. After replacing the rinse medium with 200 µl of fresh KGM-2, the plates were returned to the incubator for subsequent sampling. At scheduled time points (see below), the cell media were collected and frozen immediately at 80°C for later IL-8 determination. After sample collection, the cells in each well were evaluated for mortality. In order to evaluate whether the cytotoxicity by hydrocarbons was an acute event or a continuous process, HEK mortality was determined at 4 (n = 7) and 24 (n = 3) h after dosing treatments. For cytokine release, IL-8 concentrations were measured at 0, 1, 4, 8, and 24 h after a 1-min (n = 3) or 5-min (n = 3) exposure of HEK to the test hydrocarbons. IL-8 concentration after a 15-min exposure was not evaluated in light of high cell mortality under this condition.
Cytotoxicity assays.
Cytotoxicity was assessed by determining the percentage mortality of HEK cells after aliphatic hydrocarbon exposure. Cell mortality was determined by the neutral red (NR) uptake method, as described by Borenfreund and Puerner (1985). Briefly, 50 µg/ml NR in KGM-2 (NR medium) was preincubated at 37°C overnight and 200 µl was added to the treated wells after sample collection. Following a 3-h incubation at 37°C in a 95% O2/5% CO2 environment, the medium was replaced by 200 µl of wash/fix solution (1% CaCl2 in 0.5% formaldehyde) for 2 min and NR was extracted with 100 µl of 1% acetic acid/49% H2O/50% ethanol. Color formation after 20 min was evaluated by measuring absorption at 550 nm in an ELISA reader (Multiskan RC, Labsystem, Helsinki, Finland). Absorbance values were then normalized against KGM-2 control wells and expressed as percentage mortality relative to control wells (0% mortality), which is proportional to the cytotoxicity.
Analysis of IL-8.
Cell medium was thawed and assayed in triplicate for IL-8 concentration, using an enzyme-linked immunosorbent assay (ELISA) cytoset kit (Biosource International, Camarillo, CA). Briefly, human anti-IL-8 monoclonal antibody at 1 µg/ml in phosphate-buffered solution (PBS) (pH 7.4) was coated overnight onto 96-well immunoassay plates (Greiner, Germany) at 4°C. Nonspecific binding was blocked with 0.5% bovine serum albumin in PBS for 2 h at room temperature. After washing 3 times with normal saline, 100 µl of samples or standards were added to each well, followed immediately by the addition of a biotinylated mouse antihuman monoclonal anti-IL-8 antibody (0.5 µg/ml) and incubated for 2 h at room temperature. Following another wash, a streptavidin/horseradish peroxidase conjugate (1:2500) was then added to each well and the plates incubated for 30 min at room temperature. In the final step, plates were washed and developed in the dark for 30 min with o-phenylenediamine dihydrochloride plus urea hydrogen peroxide (Sigma Fast, Sigma Chemical Co., St. Louis, MO) at room temperature. Sample IL-8 concentrations were first determined by comparing the absorbance value at 450 nm to a standard curve on a Multiskan RC plate reader. The final IL-8 concentration (pg/ml) for each treatment and time was calculated using Genesis Lite, Ver. 3 for Windows software (Labsystems, Helsinki, Finland) with data normalized by viability in corresponding wells.
Statistics.
The HEK percent cell mortality and total IL-8 concentration from each treatment and time were statistically compared with its own media controls, using ANOVA (SAS 6.12 for Windows; SAS Institute, Cary, NC). Multiple comparisons among different hydrocarbons and jet fuels were also conducted within each exposure length and sampling time by Duncan's multiple comparison procedure. Statistical differences were set at the p < 0.05 level.
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RESULTS |
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DISCUSSION |
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In view of the large numbers of hydrocarbons that are components of jet fuels, only one cytokine was evaluated as a biomarker of the irritation response to complement the cytotoxicity assay (manifested by cell mortality). The choice of IL-8 was based on the assumption that it provided broad recognition of irritation and has high reproducibility in response to jet fuel exposure in HEK cells, as discussed earlier. Although the inflammatory cytokine network has been extensively studied (Cavaillon, 2001; Feghali and Wright, 1997
; Takashima and Bergstresser, 1996
), to our knowledge IL-10 was the only other secondary proinflammatory cytokine that has been investigated in regard to jet fuel toxicity (Ullrich, 1999
; Ullrich and Lyons, 2000
). The specific mechanisms by which the IL-8 response is triggered cannot be discerned by monitoring IL-8 alone; however, changes in IL-8 release serve as a robust biomarker for cutaneous irritation.
The most important findings of this study were that there were significant differences among aliphatic hydrocarbon chain lengths with respect to their effects on HEK mortality versus IL-8 release. Rather than a general increase corresponding to decreased carbon chain length, as was seen in the HEK mortality, the increase in IL-8 production showed a peak in response around C9C13. The greater effect on cytotoxicity did not necessarily correlate to a higher potential to increase IL-8 release (Fig. 3), suggesting that the mechanisms by which each hydrocarbon causes dermal toxicity are different. The increase in short chain cytotoxicity could be the result of the enhanced hydrocarbon penetration in the cell as seen in the isolated perfusion skin flap and diffusion cell model (Baynes et al., 2001
; McDougal et al., 2000
; Riviere et al., 1999
). Cytotoxicity of this nature could be related to the ability of short-chain hydrocarbons to disrupt membrane function.
The higher cytokine release with intermediate carbon chain lengths might be associated with an enhanced membrane residence time, which enable them to interact with IL-8 receptors, (Aggarwal and Puri, 1995; Kemeny et al., 1994
), mimicking an increased dosing time. This was supported by several dermal absorption studies (Baynes et al., 2000
; McDougal et al., 2000
; Riviere et al., 1999
) assessing the dermal disposition of hydrocarbons, and it was found that dodecane (C12) had a significantly greater residual surface concentration than octane (C8). However, in a monolayer the differences in the absorption rate and residence time due to membrane barriers would be less important than for intact skin models. It is therefore feasible that the intrinsic toxicity of each hydrocarbon contributes to the differences in expression of cytotoxicity of complete fuels. It is unfortunate that intrinsic potency and the delivery of the chemical will always be confounded when using a cell culture model. The ability of detecting intracellular concentration of individual hydrocarbons would be imperative to the differentiation of these two factors.
The maximal biological effects peaked with the middle-length carbon chain (C12C14) have been reported earlier. The n-alkanes have been shown to exhibit maximal skin tumor-promotion activity at chain lengths of C12C14 (Baxter and Miller, 1987; Sice, 1966
). Earlier investigators had also demonstrated that skin irritation peaked at C14 (Brown and Box, 1970
). The underlying mechanism was not clear. The maximal IL-8 release peaking at C9 to C13 in this study might be the result of a balance between membrane and/or intracellular availability of the hydrocarbons characterized by a wide range of partition coefficients (5.18 for C8 and 8.46 for C16). In addition to IL-8 receptors, certain membrane components could also selectively facilitate the retention and/or transportation of hydrocarbons through the membrane. For instance, the CD1 family (CD1a, CD1b, CD1c and CD1d) proteins, which are responsible for the T-cell recognition of lipophilic antigens (Moody et al., 1999
), have a specific affinity for aliphatic hydrocarbons through their long-chain aliphatic tails. Whichever mechanism(s) are involved, the results have implications for safety measures since the middle-range aliphatic hydrocarbons (C1014) are the most abundant hydrocarbons, which constitute 65% of the total base jet fuel. One should also realize that the artificial conditions of cell culture preclude a direct correlation of chemical contact time in culture to an accidental occupational exposure. The results indicated that a noncytotoxic increase in exposure time (1 to 5 min) could result in a significant increase in the release of the proinflammatory cytokine IL-8. Therefore, reducing total hydrocarbon exposure is very important.
In addition to carbon chain length, the structural or electron configuration of the chain could also affect the chemical properties and hence the toxicological effects it can elicit (Dugard and Scott, 1984; Flynn, 1990
; Scheuplein and Blank, 1971
). Earlier studies using structure-activity relationships on approximately 800 ring and nonring chemicals did not clearly elucidate whether one type of functional group is more likely to cause skin irritation (Enslein et al., 1987
). In this study, ring-shaped cyclohexane, while clearly was the most cytotoxic to HEK, induced only a minimal IL-8 response, smaller than the control level. The preliminary investigation on the dermatotoxicity of ring-configured aromatic hydrocarbons to HEK cells noted that some, but not all, tested aromatic hydrocarbons cause a significant decrease in IL-8 (unpublished data), suggesting the opposing effect in IL-8 production involved more than the difference in ring-versus-chain configurations. Furthermore, despite the higher toxicities of decane, undecane, and tridecane (C10C13 group), dodecane (C12) tends to stimulate less IL-8 release compared to the other hydrocarbons in the same group, once more implicating a higher level structural element correlate to toxicity than simple chain length. Therefore, the two responses seen after jet fuel exposure (acute cytotoxicity versus irritation) may be due to different components exerting different mechanisms, where shorter chain aliphatics (C6C9) cause cytotoxicity and others (C10C13) modulate immune response. To complicate this scenario further, topical hydrocarbons may also extract intercellular skin lipids, which potentially could increase dermal absorption, and thus toxicity, in an intact animal.
Finding the specific mechanisms by which hydrocarbons cause dermatotoxicity warrants further study. The current results suggest that pathways involved in the regulation of IL-8 expression might be related to the underlying mechanisms for hydrocarbon toxicity. Bear in mind that the regulation of inflammatory cytokines is an interactive network rather than separated pathways. IL-10 (Farkas et al., 2001; Oberholzer et al., 2001; Reich et al., 2001
), nuclear factor kappa B (NF-
B) (Cruz et al., 2001
; Takizawa et al., 2000
; Valacchi et al., 2001
) and p38 (Arbabi and Maier, 2002
) pathways are the most feasible targets worth further investigations in view of their direct regulatory relationship to IL-8 and connections to other proinflammatory mediators such as nitric oxide (Bruch-Gerharz et al., 1996
; Senftleben and Karin, 2002
). IL-1b and TNF-
will likely parallel IL-8 response based on earlier findings (Allen et al., 2000
, 2001a
,b
).
Finally, it is important to note that the toxicological effects of individual hydrocarbons carried different weight in the overall mixture toxicities, because aliphatic hydrocarbons are not all present in equal fractions in jet fuels. This issue is even more complicated by possible synergistic effects among coexisting hydrocarbon components. Therefore, it is equally as important to interpret the toxicities of hydrocarbons by clusters with respect to their compositional presence in the fuels or by different clusters with which different toxicological endpoints are indicated. The statistical analysis in this study has led us to a meaningful reclustering of hydrocarbons by their carbon chain length, which is similar to their fractional presence in the base fuel. In conclusion, we have characterized 10 aliphatic hydrocarbons in their ability to induce proinflammatory cytokine IL-8 release and cytotoxicity to HEK cells. Significant differences in individual dermatotoxicity, with regard to the carbon chain length, were detected. Specifically, the relationship of aliphatic hydrocarbon chain length to cell mortality is different than to the induction of IL-8 release in human epidermal keratinocytes.
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ACKNOWLEDGMENTS |
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NOTES |
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REFERENCES |
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Allen, D. G., Riviere, J. E., and Monteiro-Riviere, N. A. (2000). Identification of early biomarkers of inflammation produced by keratinocytes exposed to jet fuels Jet A, JP-8, and JP-8(100). J. Biochem. Mol. Toxicol. 14, 231237.[ISI][Medline]
Allen, D. G., Riviere, J. E., and Monteiro-Riviere, N. A. (2001a). Analysis of interleukin-8 release from normal human epidermal keratinocytes exposed to aliphatic hydrocarbons: Delivery of hydrocarbons to cell cultures via complexation with -cyclodextrin. Toxicol. In Vitro 15, 663669.[ISI][Medline]
Allen, D. G., Riviere, J. E., and Monteiro-Riviere, N. A. (2001b). Cytokine induction as a measure of cutaneous toxicity in primary and immortalized porcine keratinocytes exposed to jet fuels, and their relationship to normal human epidermal keratinocytes. Toxicol. Lett. 119, 209217.[ISI][Medline]
Arbabi S., and Maier R. V. (2002). Mitogen-activated protein kinases. Crit. Care Med. 30, S7479.[ISI]
Basak, S. C., Gute, B. D., Grunweld, D., Mills, D., and Riviere, J. E. (2000). Clustering of JP-8 Chemicals Using Sturture Spaces and Property Spaces. A Computational Approach. JP-8 Toxicology Workshop, Tucson, AZ.
Baxter, C. S., and Miller, M. L. (1987). Mechanism of mouse skin tumor promotion by n-dodecane. Carcinogenesis 8, 17871790.[Abstract]
Baynes, R. E., Brooks, J. D., Budsaba, K., Smith, C. E., and Riviere, J. E. (2001). Mixture effects of JP-8 additives on the dermal disposition of jet fuel components. Toxicol. Appl. Pharmacol. 175, 269281.[ISI][Medline]
Baynes, R. E., Brooks, J. D., and Riviere, J. E. (2000). Membrane transport of naphthalene and dodecane in jet fuel mixtures. Toxicol. Indust. Health 16, 225238.[ISI]
Borenfreund, E., and Puerner, J. A. (1985). Toxicity determined in vitro by morphological alterations and neutral red absorption. Toxicol. Lett. 24, 119124.[ISI][Medline]
Broddle, W. D., Dennis, M. W., Kitchen, D. N., and Vernot, E. H. (1996). Chronic dermal studies of petroleum streams in mice. Fundam. Appl. Toxicol. 30, 4754.[ISI][Medline]
Brown, V. K., and Box, V. L. (1970). Skin arginase activity as a measure of skin change under the influence of some alkanes and alkenes. Br. J. Dermatol. 82, 606612.[ISI][Medline]
Bruch-Gerharz D., Fehsel K., Suschek C., Michel G., Ruzicka T., and Kolb-Bachofen V. (1996). A proinflammatory activity of interleukin 8 in human skin: Expression of the inducible nitric oxide synthase in psoriatic lesions and cultured keratinocytes. J. Exp. Med. 184, 20072012.[Abstract]
Cavaillon, J. M. (2001). Pro-versus anti-inflammatory cytokines: Myth or reality. Cell. Mol. Biol. 47, 695702.[ISI]
Clydesdale, G. J., Dandie, G. W., and Muller, H. K. (2001). Ultraviolet light induced injury: Immunological and inflammatory effects. Immunol. Cell Biol. 79, 547568.[Medline]
Committee on Toxicology. (1996). Permissible Exposure Levels for Selected Military Fuel Vapors. National Academy Press, Washington, DC.
Corsini E., and Galli, C. L. (2000). Epidermal cytokines in experimental contact dermatitis. Toxicology 142, 203211.[ISI][Medline]
Cruz, M. T., Duarte, C. B., Goncalo, M., Figueiredo, A., Carvalho, A. P., and Lopes, M. C. (2001). Granulocyte-macrophage colony-stimulating factor activates the transcription of nuclear factor kappa B and induces the expression of nitric oxide synthase in a skin dendritic cell line. Immunol. Cell Biol. 79, 590596.[Medline]
Dudley, A. C., Peden-Adams, M. M., EuDaly, J., Pollenz, R. S., and Keil, D. E. (2001). An aryl hydrocarbon receptor independent mechanism of JP-8 jet fuel immunotoxicity in Ah-responsive and Ah-nonresponsive mice. Toxicol. Sci. 59, 251259.
Dugard, P. H., and Scott, R. C. (1984). Absorption through the skin. In Chemotherapy of Psoriasis (H. P. Baden, Ed.), pp. 125144. Pergamon Press, Oxford, U.K.
Effendy, I., Loffler, H., and Maibach, H. I. (2000). Epidermal cytokines in murine cutaneous irritant responses. J. Appl. Toxicol. 20, 335341.[ISI][Medline]
Enslein, K., Borgstedt, H. H., Blake, B. W., and Hart, J. B. (1987). Prediction of rabbit skin irritation severity by structure-activity relationships. In Vitro Toxicol. 1, 129147.
Farkas, A., Kemeny, L., Szony, B. J., Bata-Csorgo, Z., Pivarcsi, A., Kiss, M., Szell, M., Koreck, A., and Dobozy, A. (2001). Dithranol upregulates IL-10 receptors on the cultured human keratinocyte cell line HaCaT. Inflamm. Res. 50, 4449.[ISI][Medline]
Feghali, C. A., and Wright, T. M. (1997). Cytokines in acute and chronic inflammation. Front. in Biosci. 2, d1226.
Flynn, G. L. (1990). Physicochemical determinants of skin absorption. In Principles of Route-to-Route Extrapolation for Risk Assessment (T. R. Gerrity and C. J. Henry, Eds.), pp. 93127. Elsevier Science Publishing, New York.
Freeman, J. J., Federici, T. M., and McKee, R. H. (1993). Evaluation of the contribution of chronic skin irritation and selected compositional parameters to the tumorigenicity of petroleum middle distillates in mouse skin. Toxicology 81, 103112.[ISI][Medline]
Freeman, J. J., McKee, R. H., Phillips, R. D., Plutnick, R. T., Scala, R. A., and Ackerman, L. J. (1990). A 90-day toxicity study of the effects of petroleum middle distillates on the skin of C3H mice. Toxicol. Ind. Health 6, 475491.[ISI][Medline]
Geiss, K. T., and Frazier, J. M. (2001). In vitro toxicities of experimental jet fuel system ice-inhibiting agents. Sci. Total Environ. 274, 209218.[ISI][Medline]
Grant, G. M., Shaffer, K. M., Kao, W. Y., Stenger, D. A., and Pancrazio, J. J. (2000). Investigation of in vitro toxicity of jet fuels JP-8 and Jet A. Drug Chem. Toxicol. 23, 279291.[ISI][Medline]
Harris, D. T., Sakiestewa, D., Robledo, R. F., Young, R. S., and Witten, M. (2000). Effects of short-term JP-8 jet fuel exposure on cell-mediated immunity. Toxicol. Ind. Health 16, 7884.[ISI][Medline]
Kabbur, M. B., Rogers, J. V., Gunasekar, P. G., Garrett, C. M., Geiss, K. T., Brinkley, W. W., and McDougal, J. N. (2001). Effect of JP-8 jet fuel on molecular and histological parameters related to acute skin irritation. Toxicol. Appl. Pharmacol. 175, 8388.[ISI][Medline]
Kemeny, L., Ruzicka, T., Dobozy, A., and Michel, G. (1994). Role of interleukin-8 receptor in skin. Int. Arch. Allerg. Immunol. 104, 317322.[ISI][Medline]
McDougal, J. N., Pollard, D. L., Weisman, W., Garrett, C. M., and Miller, T. E. (2000). Assessment of skin absorption and penetration of JP-8 jet fuel and its components. Toxicol. Sci. 55, 247255.
Monteiro-Riviere, N., Inman, A., and Riviere, J. (2001). Effects of short-term high-dose and low-dose dermal exposure to Jet A, JP-8 and JP-8 + 100 jet fuels. J. Appl. Toxicol. 21, 485494.[ISI][Medline]
Moody, D. B., Besra, G. S., Wilson, I. A., and Porcelli, S. A. (1999). The molecular basis of CD1-mediated presentation of lipid antigens. Immunol. Rev. 172, 285296.[ISI][Medline]
Nickoloff, B. J. (1991). The cytokine network in psoriasis. Arch Dermatol. 127, 871884.[ISI][Medline]
Oberholzer, A., Oberholzer, C., and Moldawer, L. L. (2002). Interleukin-10: A complex role in the pathogenesis of sepsis syndromes and its potential as an anti-inflammatory drug. Crit. Care Med. 30(Suppl. 1), S5863.[ISI]
Reich, K., Garbe, C., Blaschke, V., Maurer, C., Middel, P., Westphal, G., Lippert, U., and Neumann, C. (2001). Response of psoriasis to interleukin-10 is associated with suppression of cutaneous type 1 inflammation, downregulation of the epidermal interleukin-8/CXCR2 pathway, and normalization of keratinocyte maturation. J. Invest. Dermatol. 116, 319329.
Rhyne, B. N., Pirone, J. R., Riviere, J. E., and Monteiro-Riviere, N. A. (2002). The use of enzyme histochemistry in detecting cutaneous toxicity of three topically applied jet fuel mixtures. Toxicol. Mech. Methods 12, 1724.
Riviere, J. E., Brooks, J. D., Monteiro-Riviere, N. A., Budsaba, K., and Smith, C. E. (1999). Dermal absorption and distribution of topically dosed jet fuels Jet-A, JP-8, and JP-8(100). Toxicol. Appl. Pharmacol. 160, 6075.[ISI][Medline]
Rosenthal, D. S., Simbulan-Rosenthal, C. M., Liu, W. F., Stoica, B. A., and Smulson, M. E. (2001). Mechanisms of JP-8 jet fuel cell toxicity: II. Induction of necrosis in skin fibroblasts and keratinocytes and modulation of levels of Bcl-2 family members. Toxicol. Appl. Pharmacol. 171, 107116.[ISI][Medline]
Scheuplein, R. J., and Blank, I. H. (1971). Permeability of the skin. Physiol. Rev. 51, 702747.
Senftleben, U., and Karin, M. (2002). The INK/NF-B pathway. Crit. Care Med. 30(Suppl. 1), S1826.[ISI]
Sice, J. (1966). Tumor-promoting activity on n-alkanes and l-alkanols. Toxicol. Appl. Pharmacol. 9, 7074.[ISI]
Takashima, A., and Bergstresser, P. R. (1996). Cytokine-mediated communication by keratinocytes and Langerhans cells with dendritic epidermal T cells. Semin. Immunol. 8, 333339.[Medline]
Takizawa, H., Ohtoshi, T., Kawasaki, S., Abe, S., Sugawara, I., Nakahara, K., Matsushima, K., and Kudoh, S. (2000). Diesel exhaust particles activate human bronchial epithelial cells to express inflammatory mediators in the airways: A review. Respirology 5, 197203.[Medline]
Terunuma, A., Aiba, S., and Tagami, H. (2001). Cytokine mRNA profiles in cultured human skin component cells exposed to various chemicals: A simulation model of epicutaneous stimuli induced by skin barrier perturbation in comparison with that due to exposure to haptens or irritant. J. Dermatol. Sci. 26, 8593.[ISI][Medline]
Ullrich, S. E. (1999). Dermal application of JP-8 jet fuel induces immune suppression. Toxicol. Sci. 52, 6167.[Abstract]
Ullrich, S. E., and Lyons, H. J. (2000). Mechanisms involved in the immunotoxicity induced by dermal application of JP-8 jet fuel. Toxicol. Sci. 58, 290298.
Valacchi, G., Rimbach, G., Saliou, C., Weber, S. U., and Packer, L. (2001). Effect of benzoyl peroxide on antioxidant status, NF-B activity, and interleukin-1a gene expression in human keratinocytes. Toxicology 165, 225234.[ISI][Medline]