L-2-Hydroxy acid oxidase (Hao2) is a peroxisomal enzyme with predominant expression in the liver and kidney. Hao2 was recently identified as a candidate gene for blood pressure quantitative trait locus in rats. To investigate a pharmacological role of Hao2 in the management of blood pressure, selective Hao2 inhibitors were developed. Optimization of screening hits 1 and 2 led to the discovery of compounds 3 and 4 as potent and selective rat Hao2 inhibitors with pharmacokinetic properties suitable for in vivo studies in rats. Treatment with compound 3 or 4 resulted in a significant reduction or attenuation of blood pressure in an established or developing model of hypertension, deoxycorticosterone acetatetreated rats. This is the first report demonstrating a pharmacological benefit of selective Hao2 inhibitors in a relevant model of hypertension. KEYWORDS: Hao2, hypertension, pyrazolecarboxylic acid, DOCA rat H uman hypertension is a complex, multifactorial disorder resulting from the interplay of multiple environmental and genetic factors, and this common disorder can lead to an increased risk of heart attack, stroke, and renal failure. The mechanisms underlying the initiation and maintenance of the hypertensive process remain unclear. 1 Almost one-third of the U.S. adult population has high blood pressure (BP), which increases the risk of cardiovascular and renal disease and shortened life expectancy. 2−4 Various antihypertensive drugs have been developed, including diuretics, beta blockers, calcium channel blockers (CCBs), renin inhibitors, 5 angiotensinconverting enzyme (ACE) inhibitors, and angiotensin II receptor blockers (ARBs). 6,7 However, these drugs either lack sufficient efficacy or are associated with significant adverse effects. In a search for a novel antihypertensive target, we have identified L-2-hydroxy acid oxidase (Hao2) 8 as a potential target for pharmacological intervention.L-2-Hydroxy acid oxidases are flavin mononucleotide (FMN)-dependent peroxisomal enzymes, which are members of the flavoenzyme family that are responsible for the oxidation of a number of L-2-hydroxy acids to ketoacids at the expense of molecular oxygen, resulting in the formation of hydrogen peroxide. Several examples of such enzymes have been identified in different organisms, e.g., glycolate oxidase from plants, lactate oxidase from Mycobacterium (L-lactate 2-monooxygenase), flavocytochrome b 2 from yeasts (L-lactate cytochrome c oxidoreductase), and mandelate dehydrogenase from Pseudomonas putida. 9 In mammals, this family of enzymes was first identified as an L-amino acid oxidase in the kidney and the liver of rats and later found to have activity similar to that of L-2-hydroxy acid. 10,11 Two α-hydroxy acid oxidases were also reported from hog renal cortex, named long chain L-α-hydroxy acid oxidase (Hao2) and short chain L-α-hydroxy acid oxidase (Hao1), because of their substrate specificity toward long and short carbon chain L-α-hydroxy acids, respectively. In both prokaryotes and eukaryotes, all the memb...
