Pharmacokinetic optimization of four soluble epoxide hydrolase inhibitors for use in a murine model of inflammation

Abstract

Background and purpose: Early soluble epoxide hydrolase inhibitors (sEHIs) such as 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) are effective anti-hypertensive and anti-inflammatory agents in various animal models. However, their poor metabolic stability and limited water solubility make them difficult to use pharmacologically. Here we present the evaluation of four sEHIs for improved pharmacokinetic properties and the anti-inflammatory effects of one sEHI.

Experimental approach: The pharmacokinetic profiles of inhibitors were determined following p.o. (oral) administration and serial bleeding in mice. Subsequently the pharmacokinetics of trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), the most promising inhibitor, was further studied following s.c. (subcutaneous), i.v. (intravenous) injections and administration in drinking water. Finally, the anti-inflammatory effect of t-AUCB was evaluated by using a lipopolysaccharide (LPS)-treated murine model.

Key results: Better pharmacokinetic parameters (higher C(max), longer t(1/2) and greater AUC) were obtained from the tested inhibitors, compared with AUDA. Oral bioavailability of t-AUCB (0.1 mg.kg(-1)) was 68 +/- 22% (n = 4), and giving t-AUCB in drinking water is recommended as a feasible, effective and easy route of administration for chronic studies. Finally, t-AUCB (p.o.) reversed the decrease in plasma ratio of lipid epoxides to corresponding diols (a biomarker of soluble epoxide hydrolase inhibition) in lipopolysaccharide-treated mice. The in vivo potency of 1 mg.kg(-1) of t-AUCB (p.o.) was better in this inflammatory model than that of 10 mg.kg(-1) of AUDA-butyl ester (p.o) at 6 h after treatment.

Conclusions and implications: t-AUCB is a potent sEHI with improved pharmacokinetic properties. This compound will be a useful tool for pharmacological research and a promising starting point for drug development.

Figure 1

The structures of the inhibitors tested. Chemical names and synonyms of the four compounds are provided in the abbreviations. APAU, 1-(1-acetypiperidin-4-yl)-3-adamantanylurea; c-AUCB, cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid; t-AUCB, trans-AUCB; TPAU, 1-trifluoromethoxyphenyl-3-(1-acetylpiperidin-4-yl) urea.

Figure 2

Blood concentration–time course of four inhibitors after administration by oral gavage to mice. (A) t-AUCB, (B) c-AUCB, (C) APAU and (D) TPAU. Each point represents the mean ± s.d. of four mice plotted in a log/linear scale. Blood was collected from the tail vein of mice at 0, 30, 60, 90, 120, 240, 360, 480 and 1440 min after dosing with the inhibitors respectively. The dotted line represents the IC₅₀ of the respective inhibitor with the murine soluble epoxide hydrolase. APAU, 1-(1-acetypiperidin-4-yl)-3-adamantanylurea; c-AUCB, cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid; t-AUCB, trans-AUCB; TPAU, 1-trifluoromethoxyphenyl-3-(1-acetylpiperidin-4-yl) urea.

Figure 3

Blood concentration–time course of t-AUCB (Trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid) after s.c. administration to mice. Each point represents the mean ± s.d. of three mice. Insert: dependence of the AUC_i (area under the concentration–time curve extrapolated to infinity) on dose given to the animal for p.o. (data from Figure 2, R² = 0.9825) and s.c. administrations (R² = 0.9989). Blood was collected from the mice through the tail vein at 0, 30, 60, 90, 120, 240, 360, 480 and 1440 min after dosing with the inhibitors respectively.

Figure 4

Blood concentration–time course of Trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB) with i.v. administration to mice. Insert: blood concentration–time course of t-AUCB with i.v. administration to mice plotted in a log/linear scale. Each point represents the mean ± s.d. of three animals. Blood was collected from the tail vein of mice at 0, 30, 60, 90, 120, 240, 360, 480 and 1440 min after dosing with the inhibitor respectively.

Figure 5

t-AUCB administration increases the systolic blood pressure of LPS-treated mice. This is a hypotensive model. Successful therapy is shown by a reversal to the normotensive state. Each bar represents the mean ± s.d. (n = 4).The blood pressure reported here was determined 4 h post treatment. In the group receiving LPS and AUDA-BE, the blood pressure of two mice was under the limit of detection, so we recorded the data as the limit of detection (40 mm Hg). *Significantly different from the control group receiving vehicle only (P < 0.05); #significantly different from the group receiving LPS only (P < 0.05); $significantly different from the group receiving LPS and t-AUCB (1 mg·kg⁻¹). Significant differences were determined by anova followed by Tukey's test. AUDA-BE, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid butyl ester; LPS, lipopolysaccharide; t-AUCB, Trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid.