Contrasting effects of calyculin A and okadaic acid on the respiratory burst of human neutrophils.
The involvement of serine/threonine protein-phosphatases in the production of superoxide (respiratory burst) by human neutrophils was investigated using calyculin A, a potent inhibitor of both protein phosphatases type 1 and 2A, and okadaic acid, which preferentially inhibits protein phosphatase type 2A. Treatment of neutrophils with calyculin A (25-75 nM) or okadaic acid (1-4 microM) had no stimulatory effect but potently enhanced total superoxide production induced by an optimal fMLP (N-formyl-methionyl-leucyl-phenylalanine) concentration (0.1 microM). The maximum increase plateaued with 50-75 nM calyculin A and 2-4 microM okadaic acid, reaching approximately 120 and 200% of control values, respectively. Unlike calyculin A, okadaic acid also primed the initial rate of superoxide production, suggesting that protein phosphatases may down-regulate both initiation and termination of respiratory burst. Optimal stimulation of the respiratory burst by PMA (160 nM) was inhibited by calyculin A and okadaic acid, with an IC50 of 60 nM and 2 microM, respectively, although both drugs caused protein hyperphosphorylation. The inhibition was partially prevented by a nonstimulatory concentration of A23187, indicating a role of calcium in the inhibitory effects of the drugs. Unlike the optimal respiratory burst, suboptimal respiratory burst induced by PMA (1-7 nM) was enhanced by calyculin A and okadaic acid. Unprimed and primed respiratory bursts were depressed by a selective antagonist of protein kinase C (GF 109203X), indicating positive regulation of these responses by protein kinase C. Thus, the use of calyculin A and okadaic acid distinguishes two regulatory processes of superoxide production.(ABSTRACT TRUNCATED AT 250 WORDS)
Djerdjouri
B
B
Laboratoire d'Hématologie, INSERM Unité 294, Hôpital Bichat, Paris, France.
Combadière
C
C
Pedruzzi
E
E
Hakim
J
J
Périanin
A
A
D000595:Amino Acid Sequence; D000001:Calcimycin / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008387:Marine Toxins; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D019319:Okadaic Acid; D010080:Oxazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects*; D013481:Superoxides / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004988:Ethers, Cyclic; D008387:Marine Toxins; D010080:Oxazoles; D013481:Superoxides; D019319:Okadaic Acid; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; C059041:calyculin A; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate