Effects of oxo and dihydro metabolites of 12-hydroxy-5,8,10,14-eicosatetraenoic acid on chemotaxis and cytosolic calcium levels in human neutrophils.
One of the pathways of metabolism of leukotriene B4 (LTB4) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) in leukocytes is oxidation of the 12-hydroxyl group, followed by reduction of the 10,11-double bond. In the case of 12R-HETE and 12S-HETE, this results in the formation of 12-oxo-ETE, 10,11-dihydro-12-oxo-ETE, and the 12R and 12S isomers of 10,11-dihydro-12-HETE (i.e., 12R-HETrE and 12S-HETrE). We investigated the effects of metabolites of 12-HETE formed by this pathway on cytosolic calcium levels and chemotaxis in human neutrophils. Of the above series of metabolites, 12S-HETrE (which has the same absolute stereochemistry at C-12 as 12R-HETE) was the most potent in stimulating both cytosolic calcium levels and chemotaxis. It was slightly less potent than 12R-HETE, consistent with the concept that reduction of the 10,11-double bond results in a loss of biological activity on neutrophils. The effect of 12S-HETrE on calcium levels was blocked by preincubation of these cells with LTB4, suggesting that it acted by stimulating the LTB4 receptor. 12R-HETrE was about 20 times less potent than its 12S isomer in stimulating cytosolic calcium in neutrophils and was also less active as a chemotactic agent. Oxidation of the 12-hydroxyl group to an oxo group resulted in a further loss of biological activity. 12-Oxo-ETE, 8-trans-12-oxo-ETE, and 12-oxo-ETrE had only modest effects on cytosolic calcium levels at concentrations as high as 10 microM and did not display detectable chemotactic activity. However, 12-oxo-ETE and its 8-trans isomer inhibited calcium responses to LTB4 by about 40%. It is concluded that reduction of the 10,11-double bond of 12-HETE results in a slight loss of biological activity on neutrophils, whereas oxidation of the 12-hydroxyl group results in a considerably greater loss of activity.
Powell
W S
WS
Meakins-Christie Laboratory, Department of Medicine, McGill University, Montreal, Quebec, Canada.
Hashefi
M
M
Falck
J R
JR
Chauhan
K
K
Rokach
J
J
Wang
S S
SS
Mills
E
E
MacLeod
R J
RJ
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D002118:Calcium / Q000097:blood*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D003600:Cytosol / Q000737:chemistry; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism* / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism*; D013237:Stereoisomerism
D006893:Hydroxyeicosatetraenoic Acids; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D002118:Calcium