The link between met-enkephalin-induced down-regulation of APN activity and the release of superoxide anion.
We have previously shown that methionine-enkephalin (MENK) differentially alters the production of superoxide anion (O(2)(-)) from neutrophils of different donors. This effect could be due to variable activity of proteolytic enzymes involved in the degradation of this neuropeptide. In this study, we investigated the possible association between the effect of MENK on O(2)(-)release and the two neutrophil associated hydrolytic enzymes that participate in enkephalin degradation; aminopeptidase N (APN) and neutral endopeptidase (NEP). We have demonstrated that APN but not NEP activity was down-regulated by MENK. This might be due to internalization, since APN down-regulation was observed only with intact neutrophils and not with the respective membranes. Preincubation of neutrophils with inhibitory anti CD13 MoAb (WM15) abbrogated the suppressive effect of MENK (10(-12), 10(-10)and 10(-8)M). These facts, show that in the periphery (as well as the brain) the dominant role in MENK hydrolysis can be attributed to APN. Also, they further support the idea of the link between the membrane associated CD13 and binding of the ligand to the opioid receptor.
Marotti
T
T
Department of Molecular Medicine, Institute Rud-er Boksković, Bijenicka 54, 1000 Zagreb, Croatia.
Balog
T
T
Munić
V
V
Sobocanec
S
S
Abramić
M
M
D000328:Adult; D000469:Alkaline Phosphatase / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018826:CD13 Antigens / Q000276:immunology / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D015536:Down-Regulation; D004744:Enkephalin, Methionine / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D015260:Neprilysin / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013481:Superoxides / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D013481:Superoxides; D004744:Enkephalin, Methionine; D000469:Alkaline Phosphatase; D018826:CD13 Antigens; D015260:Neprilysin