Oral Delivery of 1,3‐Dicyclohexylurea Nanosuspension Enhances Exposure and Lowers Blood Pressure in Hypertensive Rats

Abstract

Cytochrome P450-derived epoxyeicosatrienoic acids (EET) are biologically active metabolites of arachidonic acid that have potent effects on renal vascular reactivity and tubular ion transport and have been implicated in the control of blood pressure. EETs are hydrolyzed to their less active diols, dihydroxyeicosatrienoic acids (DHET), by the enzyme soluble epoxide hydrolase (sEH). 1,3-Dicyclohexylurea (DCU), a potent sEH inhibitor, lowers systemic blood pressure in spontaneously hypertensive rats when dosed intraperitoneally. However, DCU has poor aqueous solubility, posing a challenge for in vivo oral delivery. To overcome this limitation, we formulated DCU in a nanosuspension using wet milling. Milling reduced particle size, increasing the total surface area by approximately 40-fold. In rats chronically infused with angiotensin II, the DCU nanosuspension administered orally twice daily for 4 days produced plasma exposures an order of magnitude greater than unmilled DCU and lowered blood pressure by nearly 30 mmHg. Consistent with the mechanism of sEH inhibition, DCU increased plasma 14,15-EET and decreased plasma 14,15-DHET levels. These data confirm the antihypertensive effect of sEH inhibition and demonstrate that greatly enhanced exposure of a low-solubility compound is achievable by oral delivery using a nanoparticle drug delivery system.It is now well established that cytochrome P450 metabolites are major regulators of cardiovascular and renal functions particularly in the maintenance of vascular tone and ion transport [1]. Recently, these metabolites have also been implicated in anti-inflammatory roles [2][3][4][5]. Epoxyeicosatrienoic acids (EETs) and hydroxyeicosatrienoic acids, chiefly 20-HETE, are metabolites of arachidonic acid catalysed by the enzymes P450 epoxygenases and P450 ω -hydoxylases. Researchers have reported that decreased renal epoxygenases levels are associated with the development of hypertension [1,[6][7][8].Epoxyeicosatrienoic acids are considered as endothelialderived hyperpolarizing factors (EDHF) [9][10][11][12] possessing vasodilatory properties in some vascular beds [9,10,[13][14][15][16] independent of the nitric oxide or PGI2 driven vasorelaxation. EETs are released from the endothelial cells that activates the vascular smooth muscle cell G s α leading to the opening of Ca 2 + -activated K + channels. This effect may or may not involve cAMP or PKA in some cell types, but may involve ADP ribosylation [17][18][19] hyperpolarizing the vascular smooth muscle cells leading to vasorelaxation particularly in the resistant arteries such as the renal [19], coronary [16] and mesenteric arteries [20].Epoxyeicosatrienoic acid formed by the P450 epoxygenases enzyme from arachidonic acid is hydrolyzed to its less active diol, dihydroxyeicosatrienoic acids (DHET) by the enzyme soluble epoxide hydrolase [21,22]. The role of soluble epoxide hydrolase in the long-term control of arterial blood pressure and the pathogenesis of experimental hypertension has already been proposed [6,15,...

Hydrolysis ofcis- andtrans-Epoxyeicosatrienoic Acids by Rat Red Blood Cells

“…The IC 50 of DCU is comparable with the reported IC 50 of 160 nM on recombinant human sEH and 90 nM on recombinant murine sEH (McElroy et al, 2003). However, nanosuspension of DCU greatly enhanced the potency of DCU (Ghosh et al, 2008).…”

“…Angiotensin II up-regulates sEH expression in the vascular endothelium (Ai et al, 2007); sEH inhibition greatly lowered systolic blood pressure in angiotensin II-induced hypertensive rats (Imig et al, 2002;Ghosh et al, 2008). Consistent with the positive effects of EETs on the circulation, sEH has been proposed as a novel therapeutic target for control of blood pressure (Sinal et al, 2000), prevention of renal damage (Imig, 2005) and stroke (Zhang et al, 2007), as well as amelioration of inflammation .…”

Nanomedicines for kidney diseases

“…Nano-suspensions containing 1,3-Dicyclohexyl urea (DCU), a potent inhibitor of the degradation of the vasodilatory eicosanoid epoxyeicosatrienoic acid, were shown to be orally bioavailable and effective in reducing blood pressure in animal models of hypertension(40). Nanoparticles loaded with siRNA against angiotensinogen were also shown to effectively reduce blood pressure in rat models of hypertension(41, 42), and nano-formulated superoxide dismutase has been shown to attenuate angiotensin II-induced hypertension(43).…”

Increases in plasmatrans-EETs and blood pressure reduction in spontaneously hypertensive rats

“…Increased sEH activity has been associated with hypertension (1,18,24,55). Inhibition of EET hydrolysis by sEH inhibitors reduced BP by 20 to 30 mmHg in rats with angiotensin II (ANG II)-/salt-induced hypertension (21,24,37), as well as in the SHR (55) and the stroke-prone SHR (34). Deletion of the sEH gene reduced BP by 16 mmHg compared with wild-type DOCA-salt hypertensive mice (39).…”