Formaldehyde-induced gene expression in F344 rat nasal respiratory epithelium.

Formaldehyde (FA), an occupational and environmental toxicant used extensively in the manufacturing of many household and personal use products, is known to induce squamous cell carcinomas in the nasal turbinates of rats and mice and squamous metaplasia in monkey noses. Tissue responses to FA include a dose dependent epithelial degeneration, respiratory cell hypertrophy, and squamous metaplasia. The primary target for FA-induced toxicity in both rodents and monkeys is the respiratory nasal epithelium. FA increases nasal epithelial cell proliferation and DNA-protein crosslinks (DPX) that are associated with subsequent nasal cancer development. To address the acute effects of FA exposure that might contribute to known pathological changes, cDNA gene expression analysis was used. Two groups of male F344 rats received either 40 ul of distilled water or FA (400 mM) instilled into each nostril. Twenty-four hours following treatment, nasal epithelium was recovered from which total RNA was used to generate cDNA probes. Significance analysis of microarrays (SAM) hybridization data using Clontech Rat Atlas 1.2 arrays revealed that 24 of the 1185 genes queried were significantly up-regulated and 22 genes were significantly downregulated. Results for ten of the differentially expressed genes were confirmed by quantitative real time RT PCR. The identified genes with FA-induced change in expression belong to the functional gene categories xenobiotic metabolism, cell cycle, apoptosis, and DNA repair. These data suggest that multiple pathways are dysregulated by FA exposure, including those involved in DNA synthesis/repair and regulation of cell proliferation. Differential gene expression profiles may provide clues that could be used to define mechanisms involved in FA-induced nasal cancer.

Normal gene expression in male F344 rat nasal transitional and respiratory epithelium.

The nasal epithelium is an important target site for chemically-induced toxicity and carcinogenicity in rodents. Gene expression profiles were determined in order to provide normal baseline data for nasal transitional/respiratory epithelium from healthy rats. Cells lining the rat nasal passages were collected and gene expression analysis was performed using Clontech cDNA Rat Atlas 1.2 arrays (1185 genes). The percentages of genes within specific average expression ranges were 4.2% at 45,000-1000, 14.8% at 1000-200, 25.0% at 200-68, and 56.0% below 68. Nine out of a subset of ten genes were confirmed for relative signal intensity using quantitative real-time RT-PCR. The most highly expressed genes included those involved in phase I (e.g. cytochrome P450s) and phase II (e.g. glutathione S-transferases) xenobiotic metabolism, bioenergetics (e.g. cytochrome oxidase), osmotic balance (e.g. Na(+)/K(+) ATPase) and epithelial ionic homeostasis (e.g. ion channels). Such baseline data will contribute to further understanding the normal physiology of these cells and facilitate the interpretation of responses by the nasal epithelial cells to xenobiotic treatment or disease.