Downregulation of peroxisome proliferator-activated receptors (PPARs) in nasal polyposis -: art. no. 132

Background: Peroxisome proliferator-activated receptor (PPAR) alpha, beta delta and gamma are nuclear receptors activated by fatty acid metabolites. An anti-inflammatory role for these receptors in airway inflammation has been suggested. Methods: Nasal biopsies were obtained from 10 healthy volunteers and 10 patients with symptomatic allergic rhinitis. Nasal polyps were obtained from 22 patients, before and after 4 weeks of local steroid treatment (fluticasone). Real-time RT-PCR was used for mRNA quantification and immunohistochemistry for protein localization and quantification. Results: mRNA expression of PPAR alpha, PPAR beta delta, PPAR gamma was found in all specimens. No differences in the expression of PPARs were obtained in nasal biopsies from patients with allergic rhinitis and healthy volunteers. Nasal polyps exhibited lower levels of PPAR alpha and PPAR gamma than normal nasal mucosa and these levels were, for PPAR gamma, further reduced following steroid treatment. PPAR gamma immunoreactivity was detected in the epithelium, but also found in smooth muscle of blood vessels, glandular acini and inflammatory cells. Quantitative evaluation of the epithelial immunostaining revealed no differences between nasal biopsies from patients with allergic rhinitis and healthy volunteers. In polyps, the PPAR gamma immunoreactivity was lower than in nasal mucosa and further decreased after steroid treatment. Conclusion: The down-regulation of PPAR gamma, in nasal polyposis but not in turbinates during symptomatic seasonal rhinitis, suggests that PPAR gamma might be of importance in long standing inflammations.