The CYP4A isoforms hydroxylate epoxyeicosatrienoic acids to form high affinity peroxisome proliferator-activated receptor ligands.
Cytochromes P450 of the CYP2C and CYP4A gene subfamilies metabolize arachidonic acid to 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs) and to 19- and 20-hydroxyeicosatetraenoic acids (HETEs), respectively. Abundant functional studies indicate that EETs and HETEs display powerful and often opposing biological activities as mediators of ion channel activity and regulators of vascular tone and systemic blood pressures. Incubation of 8,9-, 11,12-, and 14,15-EETs with microsomal and purified forms of rat CYP4A isoforms led to rapid NADPH-dependent metabolism to the corresponding 19- and 20-hydroxylated EETs. Comparisons of reaction rates and catalytic efficiency with those of arachidonic and lauric acids showed that EETs are one of the best endogenous substrates so far described for rat CYP4A isoforms. CYP4A1 exhibited a preference for 8,9-EET, whereas CYP4A2, CYP4A3, and CYP4A8 preferred 11,12-EET. In general, the closer the oxido ring is to the carboxylic acid functionality, the higher the rate of EET metabolism and the lower the regiospecificity for the EET omega-carbon. Analysis of cis-parinaric acid displacement from the ligand-binding domain of the human peroxisome proliferator-activated receptor-alpha showed that omega-hydroxylated 14,15-EET bound to this receptor with high affinity (K(i) = 3 +/- 1 nm). Moreover, at 1 microm, the omega-alcohol of 14,15-EET or a 1:4 mixture of the omega-alcohols of 8,9- and 11,12-EETs activated human and mouse peroxisome proliferator-activated receptor-alpha in transient transfection assays, suggesting a role for them as endogenous ligands for these orphan nuclear receptors.
Department of Biochemistry, Vanderbilt University Medical School, Nashville, Tennessee 37232, USA.
L Ashley
LA
Cowart
Shouzuo
S
Wei
Mei-Hui
MH
Hsu
Eric F
EF
Johnson
Murali U
MU
Krishna
John R
JR
Falck
Jorge H
JH
Capdevila
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D002460:Cell Line; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006900:Hydroxylation; D007527:Isoenzymes / Q000378:metabolism*; D008024:Ligands; D008297:Male; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
D001095:Arachidonic Acids; D007527:Isoenzymes; D008024:Ligands; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D042926:Cytochrome P-450 CYP4A