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Vol. 299, Issue 2, 691-697, November 2001
Activation on Leukotriene B4 Metabolism in Isolated Rat
Hepatocytes
Division of Cell Biology, National Jewish Medical and Research
Center, Denver, Colorado (J.F., R.C.M.); and Division of
Gastroenterology, University of Colorado Health Sciences Center and
Denver Veterans Affairs Medical Center, Denver, Colorado (F.R.S., M.I.)
Leukotriene B4 (LTB4) is a potent mediator of
inflammation that recruits granulocytes to the site of injury during
the inflammatory response. The biological activity of
LTB4 is terminated by its metabolism into inactive
metabolites. Recent studies have suggested that LTB4 may
have additional activity as an endogenous ligand for the transcription
factor peroxisome proliferator-activated receptor
(PPAR
).
Based on the data presented, a model was proposed in which
LTB4 acts in a negative feedback manner by inducing the transcription of genes involved its own metabolism. In the present study the effect of PPAR
activation on LTB4 metabolism
was directly investigated. Primary cultures of rat hepatocytes were
treated with LTB4 or the PPAR
agonist WY-14,643, and
LTB4 metabolism was assessed by measuring levels of
LTB4 and the formation of LTB4 metabolites. In
addition, the effect of PPAR
activation on levels of acyl-CoA
oxidase mRNA and expression of CYP4F proteins, which are specific
-hydroxylases for LTB4, was determined. Treatment of
hepatocytes with WY-14,643, but not LTB4, was found to
increase acyl-CoA oxidase mRNA and enhance expression of rat hepatic
CYP4F proteins and CYP4A1. Neither WY-14,643 nor LTB4
caused an increase of the basal levels of LTB4 metabolism,
and no novel metabolites were observed. These results do not support
the hypothesis that a pathway of negative feedback regulation of
LTB4 metabolism involving PPAR
exists in hepatocytes,
because activation of PPAR
by LTB4 or other PPAR
agonists did not correlate with an increase in LTB4 metabolism.
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