title: The effect of occlusive and unocclusive exposure to xylene and benzene on skin irritation and molecular responses in hairless rats.
abstract: Aromatic hydrocarbons readily penetrate the skin on dermal exposure, leading to irritation, inflammation and cytotoxicity. The effects of short-term occlusive and long-term unocclusive dermal exposure to benzene and xylene on the skin irritation response (transepidermal water loss (TEWL), skin moisture content and erythema) and cytokine/chemokine expression (interleukin-1alpha (IL-1alpha), tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1)) were investigated in hairless rats. Occlusive dermal exposure was carried out with 230 microL of the chemicals for 1 h using Hill top chambers. In unocclusive dermal exposure, 15 microL of the chemicals were applied to the skin every 2 h, for 8 h a day, for 4 days. The occlusive dermal exposure revealed a clear difference in the TEWL and erythema response of these chemicals (xylene>benzene) whereas unocclusive exposure revealed similar TEWL and erythema scores for both benzene and xylene. The expression of IL-1alpha was elevated 2.5- and 3.8-fold in response to occlusive and unocclusive exposure, respectively, vs control (P<0.01) for both the chemicals (benzene and xylene). Similarly, TNF-alpha levels were elevated about 2.4- and 6.0-fold as a result of occlusive and unocclusive exposure, respectively, vs control (P<0.01). These results show that unocclusive exposure induced significantly higher TNF-alpha expression than occlusive exposure (P<0.05). The MCP-1 expression in blood was slightly elevated compared with the control group, but this increase was not statistically significant (P>0.05). Similarly, MCP levels in skin were increased approximately 1.7- and 1.8-fold by occlusive and unocclusive exposure, respectively, compared with the control group (P<0.05). Our study demonstrates that the skin irritation profiles of benzene and xylene are similar and unocclusive long-term exposure to small amounts of these chemicals can induce more skin irritation and cytokine response than occlusive exposure.
authors.affiliation: College of Pharmacy and Pharmaceutical Sciences, Florida A & M University, Tallahassee, FL 32307, USA.
authors.forename: A
authors.initials: A
authors.lastname: Chatterjee
authors.forename: R J
authors.initials: RJ
authors.lastname: Babu
authors.forename: E
authors.initials: E
authors.lastname: Ahaghotu
authors.forename: M
authors.initials: M
authors.lastname: Singh
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D001554:Benzene / Q000633:toxicity*; D016207:Cytokines / Q000378:metabolism; D017453:Dermatitis, Irritant / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D005260:Female; D008297:Male; D009779:Occlusive Dressings; D016273:Occupational Exposure / Q000009:adverse effects*; D051381:Rats; D011923:Rats, Nude; D012867:Skin / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D012869:Skin Absorption; D023422:Skin Irritancy Tests; D014867:Water / Q000378:metabolism; D014870:Water Loss, Insensible / Q000187:drug effects; D014992:Xylenes / Q000633:toxicity*
chemical_list: D016207:Cytokines; D014992:Xylenes; D014867:Water; D001554:Benzene