Analysis of interleukin-8 release from normal human epidermal keratinocytes exposed to aliphatic hydrocarbons: delivery of hydrocarbons to cell cultures via complexation with a-cyclodextrin D.G. Allen, J.E. Riviere, N.A. Monteiro-Riviere* Center for Cutaneous Toxicology and Residue Pharmacology, North Carolina State University, Raleigh, NC 27606, USA Accepted 23 March 2001 Abstract While inhalation exposures represent the predominant route for jet fuel toxicity, increased concern has been placed on topical exposures due to reports of severe contact dermatitis among military personnel. All three of the predominant aviation fuels cur- rently used by the commercial and military sectors have been demonstrated experimentally to induce the production of interleukin- 8 (IL-8), a proinflammatory cytokine, in normal human epidermal keratinocytes (NHEK). The objective of this study was to examine the effects of individual hydrocarbon components found in these fuels on IL-8 production by NHEK. In order to cir- cumvent the extreme hydrophobicity of these compounds, inclusion complexes were formed between a-cyclodextrin/aliphatic hydrocarbons by adding 2 mm hydrocarbons to 4 mm a-cyclodextrin. NHEK were exposed to four aliphatic hydrocarbons (unde- cane, dodecane, tridecane, hexadecane) for 24 h at concentrations of 7.8–500 mm. These hydrocarbons caused a peak in IL-8 release at a concentration of 31.2 mm, with the exception of dodecane which peaked at 62.5 mm. Subtoxic concentrations of the aliphatic hydrocarbons were those < 62.5 mm. These studies demonstrate that the etiology of proinflammatory cytokine expression due to jet fuel exposure may be due in large part to the aliphatic hydrocarbon components. Furthermore, these studies provide additional evidence that hydrocarbons can be successfully delivered to cells in culture by encapsulating them in cyclodextrin inclusion com- plexes. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Keratinocyte; Cytokine; Jet fuel; Hydrocarbon; Cyclodextrin 1. Introduction Jet A, JP-8 and JP-8+100 are the three predominant jet fuels used today. Jet A is the commercial fuel while JP-8 and JP-8+100 are military fuels used by both US and NATO forces. Most jet fuel toxicology studies have focused on their capacity for pulmonary toxicity. How- ever, recent emphasis on the dermal toxicity of jet fuels has uncovered that they have the capacity for traversing the stratum corneum barrier, and that they can incite a biological response (Riviere et al., 1999; Ulrich, 1999; Monteiro-Riviere et al., 2000). Furthermore, the indivi- dual components of the fuels may traverse the epidermis at varying rates, or become sequestered within the epi- dermis to increase their exposure time to the viable ker- atinocytes (Riviere et al., 1999; McDougal et al., 2000; Baynes et al., 2001). Much of the toxicological concern for jet fuels has focused on the recent addition of per- formance additives. Jet A is a kerosene-cut jet fuel base composed of a complex mixture of 228 aliphatic and aromatic hydrocarbon compounds. JP-8 is a mixture of Jet A plus three additives, an icing inhibitor (diethylene glycol monomethyl ether), an antistatic compound (Stadis 450) and a corrosion inhibitor (DC1-4A/8Q21). JP-8+100 contains JP-8 and an additional additive package (an antioxidant, chelator, detergent and dis- persant). Recent studies in our laboratory have revealed that jet fuels induce the production and release of interleukin-8 by normal human epidermal keratinocytes 0887-2333/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0887-2333(01)00075-3 Toxicology in Vitro 15 (2001) 663–669 www.elsevier.com/locate/toxinvit Abbreviation: NHEK, normal human epidermal keratinocytes. * Corresponding author. Tel.: +1-919-513-6426; fax: +1-919-513- 6358. E-mailaddress: nancy_monteiro@ncsu.edu(N.A.Monteiro-Riviere).