Gene expression in rat skin induced by irritating chemicals

Occupational skin disease is the second most significant cause of occupational disease, after accidents. Irritation from occupational chemicals such as solvents, hydrocarbons, and surfactants are one cause of this disease. Gene expression studies provide useful information about normal processes in the skin and responses of the skin to exogenous chemicals. We exposed rats, cutaneously, to sodium lauryl sulfate (SLS, 1% and 10% aqueous solution), m-xylene (pure liquid), and d-limonene (pure liquid) for 1 h and measured transcriptional responses at the end of the exposure and 3 h later for comparison with untreated skin samples. Total skin RNA was isolated and analyzed using the Affymetrix RatTox U34 array. Using the Affymetrix software, we found that 234 of approximately 850 genes were detected as present in at least 80% of the normal skin samples. The largest number of these genes was related to metabolism, oxidative/cellular stress, and signal transduction. Limonene caused the largest change in mRNA levels with a total of 34 increased transcripts and 4 decreased transcripts. Xylene treatment resulted in 6 increased transcripts and 14 decreased transcripts, while 10% SLS caused 5 transcripts to increase and 17 to decrease. Only two transcripts were observed to change in skin following a 1% SLS exposure. Sodium lauryl sulfate transcript changes increased with dose and were maximum at 4 h. Limonene transcript changes were more numerous at 1 h than at 4 h. The observed differences may reflect different mechanisms of irritation.