Quantitative evaluation of gene expression of IL-1 beta and IL-1 receptor antagonist (IL-1ra) from alveolar macrophages in idiopathic pulmonary fibrosis (IPF) and sarcoidosis

Abstract

Our previous studies demonstrated the concomitant release of IL-1 and IL-1ra in the culture supernatants of alveolar macrophages in both healthy subjects and patients with interstitial lung diseases. IL-1ra was decreased in healthy smokers (HS), IPF, and sarcoidosis, compared to healthy nonsmokers (HNS), although an increase in IL-1 release could not be detected. In this study, we examined whether such findings could be found at the gene level, or reflect posttranscriptional regulation in patients with IPF (n = 8), sarcoidosis (n = 7), healthy smokers (n = 6) and healthy nonsmokers (n = 5). The expression of IL-1 beta, IL-1ra and a house keeping gene (glucose 6 phosphate dehydrogenase: G6PD) was investigated using reverse transcription polymerase chain reaction (RT-PCR). After RT-PCR, analysis and quantification of PCR products were performed by high-performance liquid chromatography. We used 26 cycle for IL-1 beta and IL-ra mRNA and 29 for G6PD, because amplification of mRNA was in the exponential phase on that cycles, respectively. The results were expressed as the ratio of each mRNA to G6PD mRNA. IL-1ra/G6PD ratio in patients with IPF and sarcoidosis, was lower than that in HNS. On the other hand, IL-1 beta/G6PD ratio was similar in all groups. IL-1ra/IL-1 beta ratio was decreased in patients with IPF and sarcoidosis, compared to HNS. These results suggest that decreased expression of IL-1ra gene may contribute to the development of chronic low grade inflammation of the lung.