Leukotriene C4 is an essential 5-lipoxygenase intermediate in A23187-induced macrophage cytostatic activity against P815 tumor cells.
Resident peritoneal macrophages incubated with 3.5 x 10(-7) M Calcium ionophore A23187 in tumor cell growth medium (TGM) release large amounts of leukotriene (LT)E4 and an unidentified 5-lipoxygenase product, whereas A23187-stimulated macrophages produce in serum free medium LTD4, predominately. LTC4 and 3H-LTC4 incubated for 20 min at 37 degree C in serum containing TGM, convert into LTE4 and 3H-LTE4, respectively. Thus, LTC4 released from A23187-stimulated macrophages is an intermediate in TGM which rapidly converts into LTE4, probably because of the presence of gamma-glutamyl transpeptidase and cystenylglycinase in TGM. Macrophages express antitumor cytostatic activity towards P815 cells (49-53%) in a cocultured ratio (macrophage: tumor cell) 2:1 when stimulated with 3.5 x 10(-7) M A23187 in TGM. The 5-lipoxygenase inhibitor AA861 reverses the cytostatic activity by 42-58% and it inhibits also the formation of A23187-induced 5-lipoxygenase products from macrophages. Restoration of 38% macrophage- antitumor cytostatic activity by exogenous LTC4 (10(-8) M) indicates that LTC4 is an essential 5-lipoxygenase intermediate in the pathway of required signals underlying A23187-induced macrophage antitumor cytostatic activity. Macrophages not stimulated by A23187 do not express cytostatic activity in the presence of LTC4. This implies that besides LTC4, increased cytosolic [Ca2+] is required for A23187 induction of macrophage cytostatic activity.
van Hilten
J A
JA
Institute of Pharmacology, Faculty of Medicine, Erasmus University, Rotterdam, The Netherlands.
Ben Efraim
S
S
Zijlstra
F J
FJ
Bonta
I L
IL
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001091:Arachidonate Lipoxygenases / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology*; D002455:Cell Division; D003470:Culture Media; D003600:Cytosol / Q000378:metabolism; D005260:Female; D008262:Macrophage Activation; D008264:Macrophages / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D013189:SRS-A / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000166:cytology*
D003470:Culture Media; D013189:SRS-A; D000001:Calcimycin; D001091:Arachidonate Lipoxygenases; D001094:Arachidonate 5-Lipoxygenase; D013936:Thymidine