Vol. 58, Issue 6, 1294-1302, December 2000

Nuclear Factor-B Mediates Simultaneous Induction of Inducible Nitric-Oxide Synthase and Up-Regulation of the Cationic Amino Acid Transporter CAT-2B in Rat Alveolar Macrophages

Rainer Hammermann, Maria Donata Messeri Dreißig, Jutta Mössner, Margarita Fuhrmann, Liberato Berrino,¹ Manfred Göthert, and Kurt Racké

Institute of Pharmacology and Toxicology, Rheinische Friedrich Wilhelms University, Bonn, Germany

The connection between the regulation of L-arginine transport and nitric oxide (NO) synthesis was studied in rat alveolar macrophages. Lipopolysaccharides (LPSs) and interferon- stimulated in the same concentration- and time-dependent manner NO synthesis (measured by nitrite accumulation) and L-[³H]arginine uptake. This correlated with an increased mRNA expression for iNOS and the cationic amino acid transporter CAT-2B (analyzed by reverse transcription-polymerase chain reaction), with the same kinetics observed for the up-regulation of both mRNAs. Because nuclear factor-B (NF-B) is essential for induction of iNOS its role for the regulation of CAT-2B expression and L-arginine transport was investigated. The NF-B inhibitors pyrrolidine dithiocarbamate and N-p-tosyl-L-lysine chloromethyl ketone abrogated LPS- and interferon--induced increase of nitrite accumulation and L-[³H]arginine uptake as well as up-regulation of iNOS and CAT-2B mRNA. LPS-induced increase in iNOS and CAT-2B mRNA was also suppressed by specific NF-B decoy oligodesoxynucleotides, confirming the essential role of NF-B for iNOS and CAT-2B expression. Dexamethasone did not affect the initial (5 h) LPS-induced increase of iNOS and CAT-2B mRNA, but down-regulated both mRNAs after prolonged (20 h) exposure and this was accompanied by partial inhibition of LPS-stimulated nitrite accumulation and L-[³H]arginine uptake. These findings demonstrate parallel regulation of the expression of iNOS and CAT-2B, and of NO synthesis and L-arginine uptake in rat alveolar macrophages. NF-B is an essential transcription factor not only for the induction of iNOS, but also for the up-regulation of CAT-2B. The simultaneous up-regulation of CAT-2B with iNOS is considered as a mechanism to ensure a high substrate supply for iNOS.