Down-Regulation of Carbonic Anhydrase Isoenzymes in Nasal Polyps

Abstract

Objectives/Hypothesis: Carbonic anhydrase (CA) is a zinc metalloenzyme that participate in the biological processes of various fluid transporting epithelia, including ion and water transport. CA may thus play a role in the pathophysiology of normal nasal mucosa and nasal polyp. We evaluated the expression and pattern of distribution of mRNAs and proteins for CA isoenzymes in normal nasal mucosa and polyps. Study Design: This was a controlled, prospective study. Methods: The expression levels of 11 isoenzyme genes (I, II, III, IV, VA, VB, VI, VII, IX, XII, XIV) were evaluated in normal mucosa and polyps using semiquantitative reverse-transcriptase polymerase chain reaction. The expression and pattern of distiibution of CA I, II, and IX were also investigated using immunohistochemistry and Western blot. Results: mRNAs for the 11 CA isoenzymes were detected in all normal nasal mucosa and polyps tested. Their expression levels were decreased in nasal polyp in comparison with normal nasal mucosa. CA I was detected in the epithelial cells, endothelial cells, and submucosal gland of normal nasal mucosa, but only in the endothelial cells in nasal polyp. CA II in normal mucosa was intensely expressed in the submucosal gland cells and CA IX was noted in the cytoplasm and plasma membrane of epithelial cells and submucosal glands. However, these findings were not found in nasal polyp. Western blot also showed differences in their expression levels. Conclusions: These results indicate that CA may participate in the physiology of normal nasal mucosa, but also suggest that altered their expression in nasal polyps may cause impaired electrolyte and water transport across the epithelial cells.