American Journal of Pharmacology and Toxicology 1 (3): 48-53, 2006 ISSN 1557-4962 © 2006 Science Publications Corresponding Author: Dr. Randle M. Gallucci, The University of Oklahoma Health Sciences Center, College of Pharmacy, Department of Pharmaceutical Sciences, P.O. Box 26901, Oklahoma City OK, 73190, Tel: 405-271-6593, Fax: 405-271-7477 48 Inflammatory Cytokine Expression Patterns in Rat Skin Exposed to JP-8 Jet Fuel Randle M. Gallucci and Bethany M. Mickle Department of Pharmaceutical Sciences, Health Sciences Center, College of Pharmacy The University of Oklahoma, Oklahoma City, OK, USA Abstract: One of the main complaints of personnel exposed to JP-8 jet fuel is irritant dermatitis. The purpose of this investigation is to describe the JP-8 induced inflammatory cytokine response in skin over various periods of exposure. JP-8 jet fuel or acetone control (300 µL) was applied to the denuded skin of rats once a day for up to seven days. Skin samples from the exposed area were collected after one, three, five and seven days of exposure. RT-PCR was performed utilizing total skin RNA to examine the expression of various inflammatory cytokines. The mRNA’s for the chemokines CXCL1, 2, 3 and 10, as well as CCL3, 5, 11 and 20 were variably modulated during the course of exposure, favoring the expression of those that attract PMN. IL-1β and IL-6 mRNA’s were significantly induced by five days, while IL-10 was not significantly different from control at any time point. Paradoxically, skin IL-6 protein content was found to decrease continually throughout the time course as determined by ELISA. Data from the present study indicates that repeated JP-8 exposure induces numerous proinflammatory cytokines in skin that tend to favor neutrophil accumulation. The increased expression of these cytokines and chemokines may lead to increased inflammatory infiltrate and injury of the skin, resulting in JP-8 induced irritant dermatitis. Key words: JP-8 jet fuel, dermatitis, cytokines, chemokines, inflammation INTRODUCTION JP-8 is a relatively new jet fuel that the U.S. Air force adopted for use in 1996, replacing JP-4 fuel. As documented on the DoD website, roughly sixty billion gallons of JP-8 are produced annually for various uses, including jets, heaters, stoves, tanks, etc. In addition, JP-8 is very similar to Jet A, which is a commercial jet fuel in common use. While considered safer than its predecessor, JP-8 has been found to adversely affect various tissues including pulmonary [1] , immune [2-4] and skin [5] . While the low volatility of JP-8 was one of the primary reasons for its adoption, this characteristic appears to enhance its toxic effects, perhaps by increasing the duration of dermal exposure [6] . Variable transport of JP-8 components occurs across a skin barrier, with aromatic components most rapidly transported [7] . Thirteen different components of JP-8 are known to penetrate rat skin, yet only aliphatic components persist long enough to be detected [7] . Performance additives contained in JP-8 enhance absorption and modulate retention of aliphatics in skin [8] , thus possibly increasing the irritating effects of these chemicals. A prominent route of human exposure to JP-8 is via transdermal absorption. One of the purported toxic effects associated with dermal exposure to JP-8 fuel has been immunosuppression. T cell responses such as delayed type hypersensitivity (DTH) reactions were greatly suppressed in mice by as little as a single application of JP-8 [3] . Suppression of T cell proliferation was noted three days post exposure and continued for up to three weeks [3] . These effects seem to be associated with IL-10 production and appear to be abrogated utilizing anti-inflammatory treatments [9] . While the immunosuppressive activity of JP-8 indicates that contact hypersensitivity might not result from exposure to this fuel, the DoD has identified that one of the main complaints of personnel exposed to the JP-8 fuel is “skin problems” (www.JP-8.org). While it suppresses DTH as stated above, JP-8 is well known to be proinflammatory, as it induces TNFα and IL-8 in normal human keratinocyte cultures [10] . JP-8 causes skin barrier disruption, which leads to moderate to severe edema and erythema [11] , characterized by neutrophil influx in laboratory animals [12-14] . Extensive study of the very early events following JP-8 exposure found that numerous chemokines including CCL2, CCL3, CCL4, CXCL1 and CXCL2, as well as the cytokines IL-1β and IL-6, were variably induced up to eight hours post exposure [15] . We previously described the modulation of multiple cytokines and chemokines following seven days of repeated dermal exposure to JP8 in rats [14] . Herein, we expand on the previous study to examine cytokine and chemokine expression after one, three, five and seven days of repeated exposure. We find variable induction of various CC and CXC chemokines,