Abstract
The transmembrane metalloproteases angiotensin-converting enzyme (ACE) and tumor necrosis factor-alpha (TNF-alpha)-converting enzyme (TACE/ADAM-17) have been associated with inflammation, cancer progression and angiogenesis. Few investigations into the regulation of these enzymes by physiological stimuli have been reported. In this study, we investigated the influence of interferons (IFNs) type I (alpha, beta) and II (gamma) on ACE and TACE expression of human leukemic NB4 cells and monocytes. We assessed the expression of proteases by reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay and immunofluorescence analyses. IFNgamma, but not type I IFNs, upregulated membrane ACE in a dose- and time-dependency and this was reflected by the increase of ACE enzymatic activity and ACE mRNA. ACE upregulation was dependent on protein synthesis. Treatment of the interferon responsive factor 1 (IRF1)-unresponsive HepG2 cell line with IFNgamma did not affect ACE expression, thus suggesting the participation of the IRF1 signaling pathway in IFNgamma-mediated ACE upregulation in myeloid cells. In contrast, both types of IFNs, in a dose- and time-dependent manner, downregulated surface TACE without affecting TACE transcript. Soluble TACE was not detected in the medium of IFN-treated cells. IFNgamma-mediated decrease of surface TACE in NB4 cells was reversible, and correlated with an increase in intracellular TACE, suggesting that cell surface TACE was internalized in response to IFNs. These findings, showing the presence of IFN-dependent controlled mechanisms by which ACE and TACE levels are regulated in human normal and leukemic myeloid cells, may have implications in the context of current investigations on the therapeutic potential of IFNs.