Altered expression profile of superoxide dismutase isoforms in nasal polyps from nonallergic patients

Abstract

Objective/hypothesis: Nasal polyposis (NP) is a chronic inflammatory disease of the upper respiratory tract. The pathophysiology is unknown but has been shown to be multifactorial. Free radical-mediated damage has been implicated in the pathogenesis of NP. Superoxide dismutases (SODs) are the first and the most important line of antioxidant enzyme defense against reactive oxygen species. Moreover, isozymes of the SOD family are critical for modulating the activity of nitric oxide, a gaseous free radical that is believed to play roles in the physiology and pathology of respiratory tracts. However, the expression profile of SOD isoforms in NP remains unclear. We aimed to investigate the expression profile of the SOD isoforms in nasal polyps from nonallergic patients.

Study design: Prospective study.

Methods: Nasal polyp tissues were obtained from eight nonallergic patients who underwent elective polypectomy; mucosal specimens from the middle turbinates were acquired from eight subjects without NP as control tissues. The expression profile of SOD isoenzymes, SOD1, SOD2, and SOD3, in the nasal tissues was determined by reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and Western blotting (WB).

Results: NP in all eight of the NP patients manifested as severe or recurrent sinonasal polyposis clinically. The expression pattern of SOD isoenzymes evaluated by RT-PCR analysis indicated that the mean levels of SOD1 mRNA and, to a greater extent, SOD3 mRNA were higher in polyp tissues than in control tissues. There was no significant difference in the expression levels of SOD2 mRNA between the two groups. The data from ELISA and WB analysis showed that there were increased expressions of SOD1 and SOD3 protein in polyp tissues compared with the control tissues, but there was no difference in the expression of SOD2 protein between the two groups. The results from RT-PCR, ELISA, and WB were paralleled and revealed that the expressions of SOD1 and, to a greater extent, SOD3 were higher in polyp tissues than in the control group.

Conclusions: The expressions of SOD3 and SOD1 were higher in polyp tissues. These results are consistent with previously reported data and support the hypothesis that there is increased oxidative stress in NP. Our data also suggest that the SODs might be important in the pathogenesis of NP; however, the roles these SOD isoforms, especially SOD3, play in both normal nasal mucosa and NP require further clarification.