Quantification of the mRNA encoding Tumor Necrosis Factor alpha (TNFalpha) and its receptors in human nasal polyps

The object of the study was to assess the expression of the genes encoding TNFalpha and its receptors (TNF-R1 and TNF-R2) in patients with nasal polyps (NP).

The number of the mRNA copies was assessed by QRT-PCR in RNA extracts from 16 eosinophilic (ENP) and 5 neutrophilic nasal polyps (NNP), and 9 normal mucosa (NM) samples. The expression of corresponding proteins was demonstrated using immunohistochemistry.

The mean level of mRNA copies for TNFalpha in ENP (82229c/microg) was not significantly higher when compared with controls (74869c/microg). NNP demonstrated significantly lower mean TNFalpha gene expression (7021c/microg) than the controls (p<0.05). A statistically higher mRNA TNFalpha copy number in ENP than in NNP was also revealed (p<0.01). A noticeably lower mRNA expression of TNF-R1 in ENP and NNP was seen as compared to the control group (10198c/microg vs. 30749c/microg, p<0.05 and 3440c/microg vs. 30749c/microg; p<0.05 respectively). In ENP the mean TNF-R2 mRNA copy number was markedly higher than in NNP (185c/microg vs. 7.6c/microg, p<0.05). TNF-R2 mRNA level did not differ significantly between ENP and the control group (185c/microg vs. 469c/microg). TNF-R1 expression was significantly higher than TNF-R2 at the mRNA (p<0.01) and protein (p<0.05) level both in ENP and NNP. No significant correlations in proteins expression were detected between ENP and NNP.

TNF-R1 has been identified to be a prevalent form of the TNFalpha receptor in nasal polyps which may reflect the apparent dominance of this form in TNFalpha signalling. The findings raise the possibility that the eosinophils from NP may influence biological responses through TNFalpha-dependent mechanisms. The differences between ENP and NNP relating to TNFalpha and the expression of its receptors may reflect the distinct character of those diseases.