Exposure to naphthalene induces naphthyl-keratin adducts in human epidermisin vitroandin vivo

Abstract

We observed naphthyl-keratin adducts and dose-related metabolic enzyme induction at the mRNA level in reconstructed human epidermis in vitro after exposure to naphthalene. Immunofluorescence detection of 2-naphthyl-keratin-1 adducts confirmed the metabolism of naphthalene and adduction of keratin. We also observed naphthyl-keratin adducts in dermal tapestrip samples collected from naphthalene-exposed workers at levels ranging from 0.004 to 6.104 pmole adduct/μg keratin. We have demonstrated the ability of the human skin to metabolize naphthalene and to form naphthyl-keratin adducts both in vitro and in vivo. The results indicate the potential use of keratin adducts as biomarkers of dermal exposure.

The utility of naphthyl-keratin adducts as biomarkers for jet-fuel exposure

“…The collection of dermal tape-strip samples and analysis for naphthalene (Chao et al 2005) and four NKA levels (Kang-Sickel et al 2008; Kang-Sickel et al 2010) have been described previously. Briefly, tape-strip samples were collected post-exposure using three sequential adhesive tape-strips in each site (2.5 cm × 4.0 cm, surface area 10 cm 2 ; Cover-Roll ™ tape, Beiersdorf AG, Germany) from three exposed body regions with potentially the greatest JP-8 exposure, as identified by the subject and confirmed via visual inspection by the investigators.…”

“…The only method for quantitation of dermal exposure to jet fuel (JP-8) reported to date measures the unmetabolized naphthalene (surrogate for JP-8) on the skin surface, which can only be attributed to recent exposure because of rapid absorption and biotransformation of naphthalene (Chao et al 2005; Chao et al 2006). Naphthalene metabolites bound to skin keratins would be appropriate as specific biomarkers for dermal exposure, as the bioactivation required for naphthalene metabolite adduction to keratin only occurs in the suprabasal layer of the epidermis (Kang-Sickel et al 2008; Kang-Sickel et al 2010), where keratin is synthesized de novo and the non-living squame is formed (Watt 1988). Approximately 20–28 days are required for differentiation and maturation of suprabasal keratinocytes (Junqueira & Carneiro 2005; Furukawa et al 2008) to migrate from the basal layer to the surface to form the stratum corneum , which requires continuous replacement.…”

“…We further established that dermal exposure to jet fuel, along with inhalation exposure, contributes significantly to the total body burden in the exposed USAF fuel-cell maintenance workers (Chao et al 2005; Chao et al 2006; Kim et al 2007). We have also shown that highly specific polyclonal antibodies to naphthalene metabolites can be used for a sensitive enzyme-linked immunosorbent assay (ELISA) for quantification of NKAs as biomarkers of dermal exposure to jet fuel (Kang-Sickel et al 2008; Kang-Sickel et al 2010). In dermal tape-strip samples collected from 105 individuals exposed to JP-8, naphthyl-conjugated keratin peptides were detected at levels from 0.004 to 6.104 pmol adduct/μg keratin, but were undetectable in unexposed volunteers (Kang-Sickel et al 2008; Kang-Sickel et al 2010).…”

Non-invasive proteomic analysis of human skin keratins: Screening of methionine oxidation in keratins by mass spectrometry

“…The formation of naphthylkeratin adducts has been observed in human epidermis in vitro after exposure to naphthalene (a marker for jet fuel exposure) [3]. These adducts have also been detected in intact human skin exposed to naphthalenecontaining jet fuel and the levels were quantified by ELISA [3,4]. Environmental stimuli not only mediate adduct formation with skin proteins, but also induce an increase in the production of reactive oxygen species (ROS), which can result in damage to skin constituents [5][6][7].…”

“…The detection of cinnamaldehyde-keratin adducts in skin treated with cinnamic compounds has provided important understanding of the early mechanisms of skin sensitization [2]. The formation of naphthylkeratin adducts has been observed in human epidermis in vitro after exposure to naphthalene (a marker for jet fuel exposure) [3]. These adducts have also been detected in intact human skin exposed to naphthalenecontaining jet fuel and the levels were quantified by ELISA [3,4].…”