We found that the CES1A2 gene is a variant of the CES1A3 pseudogene. The findings presented here significantly increase our understanding about the gene structure and expression properties of human CES1A.

ABSTRACT:Phenacetin was withdrawn from the market because it caused renal failure in some patients. Many reports indicated that the nephrotoxicity of phenacetin is associated with the hydrolyzed metabolite, p-phenetidine. Acetaminophen (APAP), the major metabolite of phenacetin, is also hydrolyzed to p-aminophenol, which is a nephrotoxicant. However, APAP is safely prescribed if used in normal therapeutic doses. This background prompted us to investigate the difference between phenacetin and APAP hydrolase activities in human liver. In this study, we found that phenacetin is efficiently hydrolyzed in human liver microsomes (HLM) [CL int 1.08 ؎ 0.02 l/(min ⅐ mg)], whereas APAP is hardly hydrolyzed [0.02 ؎ 0.00 l/(min ⅐ mg)]. To identify the esterase involved in their hydrolysis, the activities were measured using recombinant human carboxylesterase (CES) 1A1, CES2, and arylacetamide deacetylase (AADAC). Among these, AADAC showed a K m value (1.82 ؎ 0.02 mM) similar to that of HLM (3.30 ؎ 0.16 mM) and the highest activity [V max 6.03 ؎ 0.14 nmol/(min ⅐ mg)]. In contrast, APAP was poorly hydrolyzed by the three esterases. The large contribution of AADAC to phenacetin hydrolysis was demonstrated by the prediction with a relative activity factor. In addition, the phenacetin hydrolase activity by AADAC was activated by flutamide (5-fold) as well as that in HLM (4-fold), and the activity in HLM was potently inhibited by eserine, a strong inhibitor of AADAC. In conclusion, we found that AADAC is the principal enzyme responsible for the phenacetin hydrolysis, and the difference of hydrolase activity between phenacetin and APAP is largely due to the substrate specificity of AADAC.

ABSTRACT:Human carboxylesterase (CES) 1A is responsible for the biotransformation of angiotensin-converting enzyme (ACE) inhibitors such as imidapril and temocapril. Because antidiabetic or antihyperlipidemic drugs are often coadministered with ACE inhibitors in clinical pharmacotherapy, the inhibitory effect of these drugs on CES1A1 enzyme activity was investigated. In addition, the inhibitory effect on CES2 enzyme activity was evaluated to compare it with that on CES1A1. The inhibitory effects were evaluated with 11 antidiabetic and 12 antihyperlipidemic drugs. The imidapril hydrolase activity by recombinant CES1A1 was substantially inhibited by lactone ring-containing statins such as simvastatin and lovastatin and thiazolidinediones such as troglitazone and rosiglitazone. The activity in human liver microsomes was also strongly inhibited by

ABSTRACT:In vitro inhibition studies on drug-metabolizing enzyme activity are useful for understanding drug-drug interactions and for drug development. However, the profile of the inhibitory effects of carboxylesterase (CES) activity has not been fully investigated concerning species and tissue differences. In the present study, we measured the inhibitory effects of 15 drugs and 1 compound on CES activity using liver and jejunum microsomes and cytosol in human and rat. In addition, the inhibition constant (K i values) and patterns were determined for the compounds exhibiting strong inhibition. Hydrolysis of imidapril and irinotecan hydrochloride (CPT-11) is catalyzed mainly by CES1 and CES2, respectively. In the inhibition study, imidaprilat formation from imidapril in human liver was strongly inhibited by nordihydroguaiaretic acid (NDGA) and procainamide. The inhibition profile and pattern were similar in human liver and rat liver. The compounds showing potent inhibition were similar between liver and jejunum. The K i value of NDGA (K i ‫؍‬ 13.3 ؎ 1.5 M) in human liver microsomes was 30-fold higher than that in rat liver microsomes (K i ‫؍‬ 0.4 ؎ 0.0 M). On the other hand, 7-ethyl-10-hydroxycamptothecin (SN-38) formation from CPT-11 was not inhibited except by carvedilol, manidipine, and physostigmine. The K i value of physostigmine (K i ‫؍‬ 0.3 ؎ 0.0 M) in human jejunum cytosol was 10-fold lower than that in rat jejunum cytosol (K i ‫؍‬ 3.1 ؎ 0.4 M) and was similar to that for manidipine. The present study clarified the species differences in CES inhibition. These results are useful for the development of prodrugs.

In the synthesis of technetium-99m (Tc) labeled target-specific ligands, the presence of a large excess of unlabeled ligands over Tc in the injectate hinders target accumulation ofTc-labeled ligands by competing for target molecules. To circumvent the problem, we recently developed a concept of the metal coordination-mediated multivalency, and proved the concept with a Tc-labeled trivalent compound [Tc(CO)(CN-RGD)]. In this study, D-penicillamine (Pen) was selected as a chelating molecule and a cyclic RGDfK peptide was conjugated to Pen via a hexanoic linkage (Pen-Ahx-c(RGDfK)). Tc complexation reaction, and the stability, integrin αβ binding affinity, and biodistribution of the Tc-labeled probe were investigated to evaluate the applicability of the concept to bivalent probes.Tc-[Pen-Ahx-c(RGDfK)] was obtained over 95% radiochemical yields under low Pen-Ahx-c(RGDfK) concentration (50 μM). Tc-[Pen-Ahx-c(RGDfK)] showed approximately 10-times higher integrin αβ binding affinity than the monovalent compounds, Pen-Ahx-c(RGDfK) and c(RGDyV). In biodistribution studies, the tumor accumulation of Tc-[Pen-Ahx-c(RGDfK)] was decreased to 77% and 43% of HPLC-purified (Pen-Ahx-c(RGDfK)-free) Tc-[Pen-Ahx-c(RGDfK)] by the presence of 5 nmol of unlabeled Pen-Ahx-c(RGDfK) and Re-[Pen-Ahx-c(RGDfK)], respectively. Tc-[Pen-Ahx-c(RGDfK)] provided tumor image without removing unlabeled ligand, while a Tc-labeled monovalent probe prepared from a monovalent ligand could not. These findings indicate the availability of the design concept to prepareTc-labeled bivalent probes with a variety of Tc core and other metallic radionuclides of clinical relevance.

Plasmas generated in contact with liquids have attracted considerable attention as a novel reactive field in nano-biomaterial creation because the brand-new chemical and biological reactions are yielded at the gas-liquid interface, which are induced by the physical actions of the non-equilibrium plasmas. Highly ordered periodic structures of gold nanoparticles (AuNPs) are formed by transcribing the plasma structure to the surface of the liquid, where the spatially selective synthesis of the AuNPs is realized. Furthermore, the plasma structure is controlled using a ring or disk electrode under strong magnetic fields up to 4 T. The ring structure of the nanoparticles is found to be formed in accordance with the shadow region of the ring electrode. It is found that the AuNPs are synthesized by the reduction effect of the hydrogen radical via irradiation of neutral radicals of the plasma and are destroyed by the oxidation effect of the fluorine radical via high-energy plasma-ion irradiation.

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