L. Manmohan Reddy

Cytochrome P450 Eicosanoids are Activators of Peroxisome Proliferator-Activated Receptor α

Cytochrome P450 (P450) eicosanoids regulate vascular tone, renal tubular transport, cellular proliferation, and inflammation. Both the CYP4A ω-hydroxylases, which catalyze 20-hydroxyeicosatetraenoic acid (20-HETE) formation, and soluble epoxide hydrolase (sEH), which catalyzes epoxyeicosatrienoic acid (EET) degradation to the dihydroxyeicosatrienoic acids (DHETs), are induced upon activation of peroxisome proliferator-activated receptor α (PPARα) by fatty acids and fibrates. In contrast, the CYP2C epoxygenases, which are responsible for EET formation, are repressed after fibrate treatment. We show here that P450 eicosanoids can bind to and activate PPARα and result in the modulation of PPARα target gene expression. In transactivation assays, 14,15-DHET, 11,2-EET, and 20-HETE were potent activators of PPARα. Gel shift assays showed that EETs, DHETs, and 20-HETE induced PPARα-specific binding to its cognate response element. Expression of apolipoprotein A-I was decreased 70% by 20-HETE, whereas apolipoprotein A-II expression was increased up to 3-fold by 11,12-EET, 14,15-DHET, and 20-HETE. In addition, P450 eicosanoids induced CYP4A1, sEH, and CYP2C11 expression, suggesting that they can regulate their own levels. Given that P450 eicosanoids have multiple cardiovascular effects, pharmacological modulation of their formation and/or degradation may yield therapeutic benefits.

Stable 5,6-Epoxyeicosatrienoic Acid Analog Relaxes Coronary Arteries Through Potassium Channel Activation

5,6-Epoxyeicosatrienoic acid (5,6-EET) is a cytochrome P450 epoxygenase metabolite of arachidonic acid that causes vasorelaxation. However, investigations of its role in biological systems have been limited by its chemical instability. We developed a stable agonist of 5,6-EET, 5-(pentadeca-3(Z),6(Z),9(Z)-trienyloxy)pentanoic acid (PTPA), in which the 5,6-epoxide was replaced with a 5-ether. PTPA obviates chemical and enzymatic hydrolysis. In bovine coronary artery rings precontracted with U46619, PTPA (1 nmol/L to 10 &mgr;mol/L) induced concentration-dependent relaxations, with maximal relaxation of 86±5% and EC50 of 1 &mgr;mol/L. The relaxations were inhibited by the cyclooxygenase inhibitor indomethacin (10 &mgr;mol/L; max relaxation 43±9%); the ATP-sensitive K+ channel inhibitor glybenclamide (10 &mgr;mol/L; max relaxation 49±6%); and the large conductance calcium-activated K+ channel inhibitor iberiotoxin (100 nmol/L; max relaxation 38±6%) and abolished by the combination of iberiotoxin with indomethacin or glybenclamide or increasing extracellular K+ to 20 mmol/L. Whole-cell outward K+ current was increased nearly 6-fold by PTPA (10 &mgr;mol/L), which was also blocked by iberiotoxin. Additionally, we synthesized 5-(pentadeca-6(Z),9(Z)-dienyloxy)pentanoic acid and 5-(pentadeca-3(Z),9(Z)-dienyloxy)pentanoic acid (PDPA), PTPA analogs that lack the 8,9 or 11,12 double bonds of arachidonic acid and therefore are not substrates for cyclooxygenase. The PDPAs caused concentration-dependent relaxations (max relaxations 46±13% and 52±7%, respectively; EC50 1&mgr;mol/L), which were not altered by glybenclamide but blocked by iberiotoxin. These studies suggested that PTPA induces relaxation through 2 mechanisms: (1) cyclooxygenase-dependent metabolism to 5-ether–containing prostaglandins that activate ATP-sensitive K+ channels and (2) activation of smooth muscle large conductance calcium-activated K+ channels. PDPAs only activate large conductance calcium-activated K+ channels.

Chiral cyclopropanes: asymmetric synthesis of constanolactones A and B

Abstract The title marine eicosanoids were prepared using a novel, stereoselective bis-annulation to create the characteristic cyclopropane-δ-lactone motif.

Cascade Synthesis of (E)-2-Alkylidenecyclobutanols

A facile, one-pot reaction cascade condenses 1,1,1-trichloroalkanes with alpha,beta-unsaturated ketones to unexpectedly furnish moderate to good yields of (E)-2-alkylidenecyclobutanols.