Sialic acid residues play a pivotal role in alpha(1)-acid glycoprotein (AGP)-induced generation of reactive oxygen species in chemotactic peptide pre-activated neutrophil granulocytes.
OBJECTIVE
We have recently shown that terminal sialic acid residues are essential for alpha(1)-acid glycoprotein (AGP)-induced Ca(2+) mobilization in neutrophils. The aim of the present study was to establish the importance of sialic acid residues on AGP in modulating human neutrophil functions, with emphasis on the generation of reactive oxygen species (ROS).


METHODS
ROS were measured by luminol-enhanced chemiluminescence in isolated human neutrophils.


RESULTS
We found that AGP did not provoke ROS generation in resting or L-selectin presensitized neutrophils. Moreover, AGP did not affect the N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced ROS generation, but it slightly suppressed opsonized zymosan-induced responses. However, when the neutrophils were prestimulated with fMLP, the subsequent addition of AGP provoked a marked ROS response. Dose-response studies and time studies revealed that the ROS generating capacity of AGP was highest at a concentration of 0.05 mg/ml and when given 3-10 min after addition of fMLP. A desialylated form of AGP or pretreatment of neutrophils with 3'- and 6'-sialyllactose caused a substantially lower ROS response in neutrophils prestimulated with fMLP.


CONCLUSIONS
Our data show that AGP can stimulate a second ROS response in fMLP preactivated neutrophils and that terminal sialic acid residues on AGP play a crucial role in this regard.
Gunnarsson
Peter
P
Division of Drug Research, Department of Medical and Health Sciences, Linköping University, 581 85 Linköping, Sweden. peter.gunnarsson@liu.se
Fornander
Louise
L
Påhlsson
Peter
P
Grenegård
Magnus
M
D004305:Dose-Response Relationship, Drug; D006098:Granulocytes / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D019041:L-Selectin / Q000494:pharmacology; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009961:Orosomucoid / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015054:Zymosan / Q000494:pharmacology
D009961:Orosomucoid; D017382:Reactive Oxygen Species; D019041:L-Selectin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015054:Zymosan; D019158:N-Acetylneuraminic Acid