Interspecies variation of clopidogrel hydrolysis in liver microsomes from various mammals

Characterization of the metabolism of eupalinolide A and B by carboxylesterase and cytochrome P450 in human liver microsomes

Eupalinolide A (EA; Z-configuration) and eupalinolide B (EB; E-configuration) are bioactive cis-trans isomers isolated from Eupatorii Lindleyani Herba that exert anti-inflammatory and antitumor effects. Although one pharmacokinetic study found that the metabolic parameters of the isomers were different in rats, metabolic processes relevant to EA and EB remain largely unknown. Our preliminary findings revealed that EA and EB are rapidly hydrolyzed by carboxylesterase. Here, we investigated the metabolic stability and enzyme kinetics of carboxylesterase-mediated hydrolysis and cytochrome P450 (CYP)-mediated oxidation of EA and EB in human liver microsomes (HLMs). We also explored differences in the hydrolytic stability of EA and EB in human liver microsomes and rat liver microsomes (RLMs). Moreover, cytochrome P450 reaction phenotyping of the isomers was performed via in silico methods (i.e., using a quantitative structure-activity relationship model and molecular docking) and confirmed using human recombinant enzymes. The total normalized rate approach was considered to assess the relative contributions of five major cytochrome P450s to EA and EB metabolism. We found that EA and EB were eliminated rapidly, mainly by carboxylesterase-mediated hydrolysis, as compared with cytochrome P450-mediated oxidation. An inter-species difference was observed as well, with faster rates of EA and EB hydrolysis in rat liver microsomes. Furthermore, our findings confirmed EA and EB were metabolized by multiple cytochrome P450s, among which CYP3A4 played a particularly important role.

In vitro differences in toddalolactone metabolism in various species and its effect on cytochrome P450 expression

CONTEXT

Toddalolactone, the main component of Toddalia asiatica (L.) Lam. (Rutaceae), has anticancer, antihypertension, anti-inflammatory, and antifungal activities.

OBJECTIVE

This study investigated the metabolic characteristics of toddalolactone.

MATERIALS AND METHODS

Toddalolactone metabolic stabilities were investigated by incubating toddalolactone (20 μM) with liver microsomes from humans, rabbits, mice, rats, dogs, minipigs, and monkeys for 0, 30, 60, and 90 min. The CYP isoforms involved in toddalolactone metabolism were characterized based on chemical inhibition studies and screening assays. The effects of toddalolactone (0, 10, and 50 µM) on CYP1A1 and CYP3A5 protein expression were investigated by immunoblotting. After injecting toddalolactone (10 mg/kg), in vivo pharmacokinetic profiles using six Sprague-Dawley rats were investigated by taking 9-time points, including 0, 0.25, 0.5, 0.75, 1, 2, 4, 6 and 8 h.

RESULTS

Monkeys showed the greatest metabolic capacity in CYP-mediated and UGT-mediated reaction systems with short half-lives (T_1/2) of 245 and 66 min, respectively, while T_1/2 of humans in two reaction systems were 673 and 83 min, respectively. CYP1A1 and CYP3A5 were the major CYP isoforms involved in toddalolactone biotransformation. Induction of CYP1A1 protein expression by 50 μM toddalolactone was approximately 50% greater than that of the control (0 μM). Peak plasma concentration (C_max) for toddalolactone was 0.42 μg/mL, and T_max occurred at 0.25 h post-dosing. The elimination t_1/2 was 1.05 h, and the AUC_0-t was 0.46 μg/mL/h.

CONCLUSIONS

These findings demonstrated the significant species differences of toddalolactone metabolic profiles, which will promote appropriate species selection in further toddalolactone studies.

Species Difference in the Metabolism of Mulberrin in Vitro and Its Inhibitory Effect on Cytochrome P450 and UDP-Glucuronosyltransferase Enzymes

This study aimed to evaluate the interspecies difference in metabolism of mulberrin and examine the interaction between mulberrin and CYP enzymes or recombinant human uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT) enzymes. Liver microsomes from human (HLMs), Beagle dog (DLMs), minipig (PLMs), monkey (MLMs), rabbit (RLMs), rat (RAMs), and mouse (MIMs) were used to investigate metabolic diversity among different species. Additionally, recombinant human supersomes were used to confirm that metabolic enzymes are involved in the biotransformation of mulberrin. We also evaluated the influence of mulberrin on protein expression by Western blot analysis. Mulberrin metabolism showed significant interspecies differences. We found four and two metabolites in phase I and II reaction systems, respectively. In phase I metabolism profiles of mulberrin for HLMs, PLMs and MLMs conformed to the classic Michaelis-Menten kinetics, RAMs and MIMs followed biphasic kinetics; phase II reaction of mulberrin in HLMs, DLMs, PLMs, MLMs, RLMs, RAMs and MIMs followed biphasic kinetics. UGT1A1 were the major CYP isoforms responsible for the metabolism of mulberrin. Mulberrin showed potent inhibitory effects against CYP3A4, CYP2C9, CYP2E1, UGT1A1, UGT1A3 and UGT2B7 with IC₅₀ values of 54.21, 9.93, 39.12, 3.84, 2.01, 16.36 µM, respectively. According to Western blot analysis, mulberrin can upregulate the protein expression of CYP2C19, and downregulate the expression levels of CYP3A5 and CYP2C9 in HepG2 cells as concentration increased. The interspecies comparisons can help find other species with metabolic pathways similar to those in humans for future in vivo studies.

Deciphering the species differences in CES1A-mediated hydrolytic metabolism by using a bioluminescence substrate

Carboxylesterases 1A (CES1A) is a key enzyme responsible for the hydrolytic metabolism of a great deal of endogenous and exogenous substrates bearing ester- or amide-bond(s). This study aimed to decipher the species difference in CES1A-mediated hydrolytic metabolism by using a newly developed bioluminescence CES1A sensor (termed NLMe) as the probe substrate, while the liver microsomes from six different mammalian species (human, cynomolgus monkey, dog, minipig, rat and mouse) were used as the enzyme sources. Metabolite profiling demonstrated that all tested liver microsomes from various species could catalyze NLMe hydrolysis, but significant difference in hydrolytic rate was observed. Kinetic plots of NLMe hydrolysis in liver microsomes from different species showed that the inherent clearance rates (C_lint) of NLMe in human liver microsomes (HLM), cynomolgus monkey liver microsomes (CyLM), and pig liver microsome (PLM) were comparable, while the C_lint values of NLMe in dog liver microsomes (DLM), mouse liver microsomes (MLM), and rat liver microsomes (RLM) were relatively small. Moreover, chemical inhibition assays showed that NLMe hydrolysis in all tested liver microsomes could be competently inhibited by BNPP (a potent broad-spectrum inhibitor of CES), but CUA (a selective inhibitor of human CES1A) only inhibited NLMe hydrolysis in human liver microsomes and dog liver microsomes. In summary, the species differences in CES1A-catalyzed NLMe hydrolysis were carefully investigated from the views of the similarities in metabolite profile, hydrolytic kinetics and inhibitor response. All these findings provide new insights into the species differences in CES1A-mediated hydrolytic metabolism and suggest that it is necessary for the pharmacologists to choose appropriate animal models to replace humans for evaluating the in vivo effects of CES1A inhibitors.

In Vitro Hepatic Metabolism of Curcumin Diethyl Disuccinate by Liver S9 from Different Animal Species

Liver S9 (LS9) is a nearly complete collection of all hepatic drug-metabolizing enzymes. It is a low-cost model for predicting drug metabolic activity. This study aimed to identify the suitability of using LS9 of different animal sources in drug metabolism profiling with respect to the possible translation of the in vitro outcomes to clinical studies. The in vitro hepatic metabolism of curcumin diethyl disuccinate (CDD) in LS9 of rats, dogs, monkeys, and humans was evaluated. The identity of CDD metabolites and the metabolism kinetic parameters, including degradation rate constant, in vitro/in vivo intrinsic clearance, and half-life, were determined. CDD was rapidly metabolized into monoethylsuccinyl curcumin and curcumin in LS9 of all tested species mainly by carboxylesterases (CESs), including CES1 and CES2, and butyrylcholinesterase. The in vitro intrinsic clearance of CDD was in the order of human > dog > monkey > rat, whereas that of monoethylsuccinyl curcumin in the order of dog > monkey > human > rat; this parameter was not correlated with their respective in vivo clearance, which followed the order of dog > monkey > rat > human. Therefore, in vitro drug metabolism data inferred from LS9 of nonhuman origin, especially from monkeys and dogs, cannot be used as preclinical data for human trials, as humans have a smaller liver-to-body weight ratio than monkeys, dogs, and rats. The in vivo drug metabolism is dictated by the anatomical factors of the test subject.

Using Esterase Selectivity to Determine the In Vivo Duration of Systemic Availability and Abolish Systemic Side Effects of Topical β-Blockers

For disorders of the skin, eyes, ears, and respiratory tract, topical drugs, delivered directly to the target organ, are a therapeutic option. Compared with systemic oral therapy, the benefits of topical treatments include a faster onset of action, circumventing the liver first pass drug metabolism, and reducing systemic side effects. Nevertheless, some systemic absorption still occurs for many topical agents resulting in systemic side effects. One way to prevent these would be to develop drugs that are instantly degraded upon entry into the bloodstream by serum esterases. Because topical β-blockers are used in glaucoma and infantile hemeangioma and cause systemic side effects, the β-adrenoceptor system was used to test this hypothesis. Purified liver esterase reduced the apparent affinity of esmolol, an ester-containing β-blocker used in clinical emergencies, for the human β-adrenoceptors in a concentration and time-dependent manner. However, purified serum esterase had no effect on esmolol. Novel ester-containing β-blockers were synthesized and several were sensitive to both liver and serum esterases. Despite good in vitro affinity, one such compound, methyl 2-(3-chloro-4-(3-((2-(3-(3-chlorophenyl)ureido)ethyl)amino)-2-hydroxypropoxy)phenyl)acetate, had no effect on heart rate when injected intravenously into rats, even at 10 times the equipotent dose of esmolol and betaxolol that caused short and sustained reductions in heart rate, respectively. Thus, ester-based drugs, sensitive to serum esterases, offer a mechanism for developing topical agents that are truly devoid of systemic side effects. Furthermore, differential susceptibility to liver and serum esterases degradation may also allow the duration of systemic availability for other drugs to be fine-tuned.

Rapid bioluminescence assay for monitoring rat CES1 activity and its alteration by traditional Chinese medicines

In traditional Chinese medicine herbs (TCM), including Radix Salviae Miltiorrhizae (Danshen), Radix Puerariae Lobatae (Gegen), Radix Angelicae Sinensis (Danggui), and Rhizoma Chuanxiong (Chuanxiong) are widely used for the prevention and treatment of cardiovascular diseases and also often co-administered with Western drugs as a part of integrative medicine practice. Carboxylesterase 1 (CES1) plays a pivotal role in the metabolisms of pro-drugs. Since (S)-2-(2-(6-dimethylamino)-benzothiazole)-4,5-dihydro-thiazole-4-carboxylate (NLMe) has recently been identified by us as a selective CES1 bioluminescent sensor, we developed a rapid method using this substrate for the direct measurement of CES1 activity in rats. This bioluminescence assay was applied to determine CES1 activity in rat tissues after a two-week oral administration of each of the four herbs noted above. The results demonstrated the presence of CES1 enzyme in rat blood and all tested tissues with much higher enzyme activity in the blood, liver, kidney and heart than that in the small intestine, spleen, lung, pancreas, brain and stomach. In addition, the four herbs showed tissue-specific effects on rat CES1 expression. Based on the CES1 biodistribution and its changes after treatment in rats, the possibility that Danshen, Gegen and Danggui might alter CES1 activities in human blood and kidney should be considered. In summary, a selective and sensitive bioluminescence assay was developed to rapidly evaluate CES1 activity and the effects of orally administered TCMs in rats.