Inhibition of nitric oxide synthase abrogates lipopolysaccharides-induced up-regulation of L-arginine uptake in rat alveolar macrophages.
It was tested whether the inducible nitric oxide synthase (iNOS) pathway might be involved in lipopolysaccharides-(LPS)-induced up-regulation of L-arginine transport in rat alveolar macrophages (AM). AM were cultured in absence or presence of LPS. Nitrite accumulation was determined in culture media and cells were used to study [3H]-L-arginine uptake or to isolate RNA for RT - PCR. Culture in presence of LPS (1 microg ml(-1), 20 h) caused 11 fold increase of nitrite accumulation and 2.5 fold increase of [3H]-L-arginine uptake. The inducible NO synthase (iNOS) inhibitor 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT) present alone during culture had only marginal effects on [3H]-L-arginine uptake. However, AMT present during culture additionally to LPS, suppressed LPS-induced nitrite accumulation and LPS-stimulated [3H]-L-arginine uptake in the same concentration-dependent manner. AMT present only for the last 30 min of the culture period had similar effects on [3H]-L-arginine uptake. AMT present only during the uptake period also inhibited LPS-stimulated [3H]-L-arginine uptake, but with lower potency. The inhibitory effect of AMT could not be opposed by the NO releasing compound DETA NONOate. LPS caused an up-regulation of the mRNA for the cationic amino acid transporter CAT-2B, and this effect was not affected by AMT. AMT (100 microM) did not affect L-arginine transport studied by electrophysiological techniques in Xenopus laevis oocytes expressing either the human cationic amino acid transporter hCAT-1 or hCAT-2B. In conclusion, iNOS inhibition in rat AM abolished LPS-activated L-arginine uptake. This effect appears to be caused by reduced flow of L-arginine through the iNOS pathway.
Hammermann
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Institute of Pharmacology and Toxicology, University of Bonn, Reuterstr. 2b, D-53113 Bonn, Germany.
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D026923:Amino Acid Transport Systems, Basic; D000818:Animals; D001120:Arginine / Q000378:metabolism* / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013843:Thiazines / Q000494:pharmacology; D014982:Xenopus laevis
C093124:2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine; D026923:Amino Acid Transport Systems, Basic; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009573:Nitrites; D012333:RNA, Messenger; D013843:Thiazines; C087435:Slc7a2 protein, mouse; D001120:Arginine; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat