title: Regulation of renal CYP4A expression and 20-HETE synthesis by nitric oxide in pregnant rats.
abstract: 20-Hydroxyeicosatetraenoic acid (20-HETE), which promotes renal vasoconstriction, is formed in the rat kidney primarily by cytochrome P-450 (CYP) 4A isoforms (4A1, 4A2, 4A3, 4A8). Nitric oxide (NO) has been shown to bind to the heme moiety of the CYP4A2 protein and to inhibit 20-HETE synthesis in renal arterioles of male rats. However, it is not known whether NO interacts with and affects the activity of CYP4A1 and CYP4A3, the major renal CYP4A isoforms in female rats. Incubation of recombinant CYP4A1 and 4A3 proteins with sodium nitroprusside (SNP) shifted the absorbance at 440 nm, indicating the formation of a ferric-nitrosyl-CYP4A complex. The absorbance for CYP4A3 was about twofold higher than that of CYP4A1. Incubation of SNP or peroxynitrite (PN; 0.01-1 mM) with CYP4A recombinant membranes caused a concentration-dependent inhibition of 20-HETE synthesis, with both chemicals having a greater inhibitory effect on CYP4A3-catalyzed activity. Moreover, incubation of CYP4A1 and 4A3 proteins with PN (1 mM) resulted in nitration of tyrosine residues in both proteins. In addition, PN and SNP inhibited 20-HETE synthesis in renal microvessels from female rats by 65 and 59%, respectively. We previously showed that microvessel CYP4A1/CYP4A3 expression and 20-HETE synthesis are decreased in late pregnancy. Therefore, we investigated whether such a decrease is dependent on NO, the synthesis of which has been shown to increase in late pregnancy. Administration of NG-nitro-l-arginine methyl ester (l-NAME) to pregnant rats for 6 days (days 15-20 of pregnancy) caused a significant increase in systolic blood pressure, which was prevented by concurrent treatment with the CYP4A inhibitor 1-aminobenzotriazole (ABT). Urinary NO2/NO3 excretion decreased by 40 and 52% in l-NAME- and l-NAME + ABT-treated groups, respectively. Interestingly, renal microvessel 20-HETE synthesis showed a marked increase following l-NAME treatment, and this increase was diminished with coadministration of ABT. These results demonstrate that NO interacts with CYP4A proteins in a distinct manner and it interferes with renal microvessel 20-HETE synthesis, which may play an important role in the regulation of blood pressure and renal function during pregnancy.
authors.affiliation: Department of Physiology, Medical College of Georgia, Augusta, GA 30912, USA. mwang@mail.mcg.edu
authors.forename: Mong-Heng
authors.initials: MH
authors.lastname: Wang
authors.forename: Jishi
authors.initials: J
authors.lastname: Wang
authors.forename: Hsin-Hsin
authors.initials: HH
authors.lastname: Chang
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Zand
authors.forename: Miao
authors.initials: M
authors.lastname: Jiang
authors.forename: Alberto
authors.initials: A
authors.lastname: Nasjletti
authors.forename: Michal
authors.initials: M
authors.lastname: Laniado-Schwartzman
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001794:Blood Pressure / Q000502:physiology; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D000072470:Cytochrome P450 Family 4; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis*; D007668:Kidney / Q000098:blood supply / Q000201:enzymology*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C465387:Cyp4a1protein, rat; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D006893:Hydroxyeicosatetraenoic Acids; D020030:Nitric Oxide Donors; D011994:Recombinant Proteins; D030421:Peroxynitrous Acid; D009599:Nitroprusside; D009569:Nitric Oxide; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D003577:Cytochrome P-450 Enzyme System; D019001:Nitric Oxide Synthase; D000072470:Cytochrome P450 Family 4; C465389:Cyp4a3 protein, rat; D019331:NG-Nitroarginine Methyl Ester