Cationic proteins inhibit L-arginine uptake in rat alveolar macrophages and tracheal epithelial cells. Implications for nitric oxide synthesis.
Eosinophil-derived cationic proteins play an essential role in the pathogenesis of bronchial asthma. We tested whether cationic proteins interfere with the cationic amino-acid transport in alveolar macrophages (AMPhi) and tracheal epithelial cells, and whether L-arginine-dependent pathways were affected. The effect of cationic polypeptides on cellular uptake of [(3)H]-L-arginine, nitrite accumulation, and the turnover of [(3)H]-L-arginine by nitric oxide (NO) synthase and arginase (formation of [(3)H]-L-citrulline and [(3)H]-L-ornithine, respectively) were studied. Poly-L-arginine reduced [(3)H]-L-arginine uptake in rat AMPhi and tracheal epithelial cells in a concentration-dependent manner (at 300 microgram/ml by 70%). Poly-L-lysine, protamine, and major basic protein (each up to 300 microgram/ml) tested in rat AMPhi inhibited [(3)H]-L-arginine uptake by 35 to 50%. During 6 h incubation in amino acid-free Krebs solution, rat AMPhi, precultured in the absence or presence of LPS (1 microgram/ml), accumulated 1.4 and 3.5 nmol/10(6) cells nitrite, respectively. Addition of 100 microM L-arginine increased nitrite accumulation by 70 and 400% in control and lipopolysaccharide-treated AMPhi, respectively. Nitrite accumulation in the presence of L-arginine was reduced by poly-L-arginine and poly-L-lysine (100 and 300 microgram/ml) by 60 to 85% and 20 to 30%, respectively. Poly-L-arginine, but not poly-L-lysine, inhibited nitrite accumulation already in the absence of extracellular L-arginine. Poly-L-arginine (300 microgram/ml) inhibited [(3)H]-L-citrulline formation by AMPhi stronger than that of [(3)H]-L-ornithine. We conclude that cationic proteins can inhibit cellular transport of L-arginine and this can limit NO synthesis. Poly-L-arginine inhibits L-arginine uptake more effectively than other cationic proteins and exerts additional direct inhibitory effects on NO synthesis.
Hammermann
R
R
Institute of Pharmacology and Toxicology, University of Bonn, Bonn; Department of Pharmacology, University of Mainz, Mainz, Germany.
Hirschmann
J
J
Hey
C
C
Mössner
J
J
Folkerts
G
G
Nijkamp
F P
FP
Wessler
I
I
Racké
K
K
D000818:Animals; D001119:Arginase / Q000494:pharmacology; D001120:Arginine / Q000493:pharmacokinetics*; D001798:Blood Proteins / Q000494:pharmacology; D002956:Citrulline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D047091:Eosinophil Granule Proteins; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology; D015870:Gene Expression; D006493:Heparin / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012260:Ribonucleases; D013997:Time Factors; D014132:Trachea / Q000378:metabolism*
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D005343:Fibrinolytic Agents; D008070:Lipopolysaccharides; D009573:Nitrites; D002956:Citrulline; D009569:Nitric Oxide; D006493:Heparin; D001120:Arginine; D012260:Ribonucleases; D001119:Arginase; D008239:Lysine