Enhanced Platelet Response to Clopidogrel in Abcc3-deficient Mice Due to Its Increased Bioactivation

The metabolic activation of and platelet response to vicagrel vary with P-glycoprotein deficiency, rather than P-glycoprotein inhibition, in mice

This study aimed to determine changes in the hydrolysis of vicagrel, a substrate drug of arylacetamide deacetylase (Aadac) and carboxylesterase 2 (Ces2), in P-glycoprotein (P-gp)-deficient or P-gp-inhibited mice and to elucidate the mechanisms involved.Male wild-type (WT) and P-gp knock-out (KO) mice were used to investigate the systemic exposure of vicagrel thiol active metabolite H4 and platelet response to vicagrel, and the mRNA and protein expression levels of intestinal Aadac and Ces2. Moreover, WT mice were administered vicagrel alone or in combination with elacridar (a potent P-gp inhibitor) to determine drug-drug interactions.Compared with WT mice, P-gp KO mice exhibited significant increases in the systemic exposure of H4, the protein expression levels of intestinal Aadac and Ces2, and inhibition of ADP-induced platelet aggregation by vicagrel. Further, the H4 exposure was positively correlated with intestinal Aadac protein expression levels but did not vary with short-term inhibition of P-gp efflux activity by elacridar.P-gp-deficient mice, rather than elacridar-treated mice, exhibited significant upregulation of intestinal Aadac and Ces2 and thus, enhanced metabolic activation of and platelet response to vicagrel, suggesting that the metabolic activation of vicagrel may vary with P-gp deficiency, not P-gp inhibition, in mice.

Is platelet responsiveness to clopidogrel attenuated in overweight or obese patients and why? A reverse translational study in mice

BACKGROUND AND PURPOSE

Overweight or obese patients exhibit poorer platelet responses to clopidogrel. However, the mechanisms behind this phenotype remain to be elucidated. Here, we sought to discover whether and why obesity could affect the metabolic activation of and/or platelet response to clopidogrel in obese patients and high-fat diet-induced obese mice.

EXPERIMENTAL APPROACH

A post hoc stratified analysis of an observational clinical study was performed to investigate changes in residual platelet reactivity with increasing body weight in patients taking clopidogrel. Furthermore, high-fat diet-induced obese mice were used to reveal alterations in systemic exposure of clopidogrel thiol active metabolite H4, ADP-induced platelet activation and aggregation, the expression of genes involved in the metabolic activation of clopidogrel, count of circulating reticulated and mature platelets, and proliferation profiles of megakaryocytes in bone marrow. The relevant genes and potential signalling pathways were predicted and enriched according to the GEO datasets available from obese patients.

KEY RESULTS

Obese patients exhibited significantly attenuated antiplatelet effects of clopidogrel. In diet-induced obese mice, systemic exposure of clopidogrel active metabolite H4 was reduced but that of its hydrolytic metabolite was increased due to down-regulation of certain P450s but up-regulation of carboxylesterase-1 in the liver. Moreover, enhanced proliferation of megakaryocytes and elevated platelet count also contributed.

CONCLUSION AND IMPLICATIONS

Obesity attenuated metabolic activation of clopidogrel and increased counts of circulating reticulated and mature platelets, leading to impaired platelet responsiveness to the drug in mice, suggesting that clopidogrel dosage may need to be adjusted adequately in overweight or obese patients.

Short-term standard alcohol consumption enhances platelet response to clopidogrel through inhibition of Nrf2/Ces1 pathway and induction of Cyp2c in mice

AIMS

Drinking alcohol is prevalent worldwide; however, it is unknown whether alcohol could affect the antiplatelet effects of clopidogrel in patients when taking both concomitantly. This study was designed to investigate the influence of short-term standard alcohol consumption on the metabolic activation of and platelet response to clopidogrel in mice as well as the mechanisms involved.

MAIN METHODS

Male C57BL/6J mice were administered with normal saline (vehicle control) or alcohol at 2 g/kg/day for 7 days, and then gavaged with vehicle control or a single dose of clopidogrel at 10 mg/kg. Inhibition of ADP-induced platelet aggregation and activation by clopidogrel, plasma concentrations of clopidogrel and its active metabolite H4, and changes in mRNA and protein expression of genes related to clopidogrel metabolism and its regulation were measured in mice pretreated with or without alcohol.

KEY FINDINGS

Compared with vehicle control, alcohol pretreatment significantly reduced hydrolysis of clopidogrel as a result of significant down-regulation of Nrf2-mediated Ces1 expression (responsible for the formation of clopidogrel carboxylate), increased metabolic activation of clopidogrel due to significant up-regulation of Cyp2c (for the formation of active thiol metabolite H4), and consequently enhanced inhibition of ADP-induced platelet aggregation and activation by clopidogrel.

SIGNIFICANCE

Short-term standard alcohol consumption would significantly enhance suppression of ADP-induced platelet aggregation and activation by clopidogrel through significant inhibition of Nrf2/Ces1 signaling pathway and induction of Cyp2c, suggesting that alcohol may interact with drugs that are predominantly metabolized by CES1 or CYP2C in patient care, including clopidogrel.

P-glycoprotein deficiency enhances metabolic activation of and platelet response to clopidogrel through marked up-regulation of Cyp3a11 in mice: Direct evidence for the interplay between P-glycoprotein and Cyp3a

Variability in P-glycoprotein (P-gp) efflux transporting activity was supposed to be involved in altered intestinal absorption and bioavailability of clopidogrel in patients; however, reliable evidence is still lacking. In this study, we sought to determine whether P-gp could play an important role in the metabolic activation of and platelet response to clopidogrel in mice. Abcb1a/1b knock-out (KO) and wild-type (WT) mice were used to evaluate differences in the intracellular accumulation of clopidogrel in the intestine, liver, and brain tissues and in systemic exposure of clopidogrel and its main metabolites as well as the mechanisms involved. Results indicated that, compared with WT mice, KO mice exhibited an 84% increase in systemic exposure of clopidogrel active thiol metabolite H4 and a 14.5% rise of suppression of ADP-induced platelet integrin αIIbβ3 activation, paralleled by a 41% decrease in systemic exposure of clopidogrel due to enhanced systemic clearance. Furthermore, KO mice displayed a 45% increase in Cyp3a11 but a 23% decrease in Ces1 at their protein levels compared with WT mice. Concurrently, intracellular clopidogrel concentrations in the tissues examined did not differ significantly between KO and WT mice. We conclude that although P-gp does not transport clopidogrel and its major metabolites in mice, P-gp-deficient mice exhibit elevated formation of the active metabolite H4 and enhanced antiplatelet effect of clopidogrel through up-regulation of Cyp3a11 and down-regulation of Ces1, suggesting that P-gp activity may correlate inversely with the formation of H4 and antiplatelet efficacy of clopidogrel in clinical settings due to P-gp and CYP3A4 interplay.

Multidrug Resistance-Associated Protein 3 Is Responsible for the Efflux Transport of Curcumin Glucuronide from Hepatocytes to the Blood

Curcumin, a major polyphenol present in turmeric, is predominantly converted to curcumin-O-glucuronide (COG) in enterocytes and hepatocytes via glucuronidation. COG is a principal metabolite of curcumin in plasma and feces. It appears that the efflux transport of the glucuronide conjugates of many compounds is mediated largely by multidrug resistance-associated protein (MRP) 3, the gene product of the ATP-binding cassette, subfamily C, member 3. However, it is currently unknown whether this was the case with COG. In this study, Mrp3 knockout (KO) and wild-type (WT) mice were used to evaluate the pharmacokinetics profiles of COG, the liver-to-plasma ratio of COG, and the COG-to-curcumin ratio in plasma, respectively. The ATP-dependent uptake of COG into recombinant human MRP3 inside-out membrane vesicles was measured for further identification, with estradiol-17β-d-glucuronide used in parallel as the positive control. Results showed that plasma COG concentrations were extremely low in KO mice compared with WT mice, that the liver-to-plasma ratios of COG were 8-fold greater in KO mice than in WT mice, and that the ATP-dependent uptake of COG at 1 or 10 μM was 5.0- and 3.1-fold greater in the presence of ATP than in the presence of AMP, respectively. No significant differences in the Abcc2 and Abcg2 mRNA expression levels were seen between Mrp3 KO and WT mice. We conclude that Mrp3 is identified to be the main efflux transporter responsible for the transport of COG from hepatocytes into the blood. SIGNIFICANCE STATEMENT: This study was designed to determine whether multidrug resistance-associated protein (Mrp) 3 could be responsible for the efflux transport of curcumin-O-glucuronide (COG), a major metabolite of curcumin present in plasma and feces, from hepatocytes into the blood using Mrp3 knockout mice. In this study, COG was identified as a typical Mrp3 substrate. Results suggest that herb-drug interactions would occur in patients concomitantly taking curcumin and either an MRP3 substrate/inhibitor or a drug that is predominantly glucuronidated by UDP-glucuronosyltransferases.

Clopidogrel Resistance in a Murine Model of Diet-Induced Obesity Is Mediated by the Interleukin-1 Receptor and Overcome With DT-678

OBJECTIVE

Clopidogrel is a commonly used P2Y₁₂ inhibitor to treat and prevent arterial thrombotic events. Clopidogrel is a prodrug that requires bioactivation by CYP (cytochrome P450) enzymes to exert antiplatelet activity. Diabetes mellitus is associated with an increased risk of ischemic events, and impaired ability to generate the active metabolite (AM) from clopidogrel. The objective of this study is to identify the mechanism of clopidogrel resistance in a murine model of diet-induced obesity (DIO). Approach and Results: C57BL/6J mice and IL-1R^-/- mice were given high-fat diet for 10 weeks to generate a murine model of diet-induced obesity. Platelet aggregation and carotid arterial thrombosis were assessed in response to clopidogrel treatment. Wild-type DIO mice exhibited resistance to antiplatelet and antithrombotic effects of clopidogrel that was associated with reduced hepatic expression of CYP genes and reduced generation of the AM. IL (Interleukin)-1 receptor-deficient DIO (IL1R^-/- DIO) mice showed no resistance to clopidogrel. Lack of resistance was accompanied by increased exposure of the clopidogrel AM. This resistance was also absent when wild-type DIO mice were treated with the conjugate of the clopidogrel AM, DT-678.

CONCLUSIONS

These findings indicate that antiplatelet effects of clopidogrel may be impaired in the setting of diabetes mellitus due to reduced prodrug bioactivation related to IL-1 receptor signaling. Therapeutic targeting of P2Y₁₂ in patients with diabetes mellitus using the conjugate of clopidogrel AM may lead to improved outcomes.

Development and validation of a UPLC-MS/MS method for simultaneous determination of vicagrel and its major metabolites in rat or human plasma: An optimized novel strategy for the stabilization of vicagrel

Vicagrel is a promising novel antiplatelet drug. However, the quantification of vicagrel in plasma is currently unavailable since it is liable to be hydrolyzed in plasma by esterases. In this study, an optimized strategy was developed and validated to stabilize vicagrel, 2-oxo-clopidogrel (thiolactone metabolite), and H4 (active thiol metabolite) before quantification of the analytes, such as addition of citric acid (for plasma acidification) and NaF (a non-specific esterase inhibitor) to inhibit esterase activity, immediate addition of a thiol-alkylating reagent MPB into blood samples to derivatize H4 for the formation of stable H4 derivative (i.e., MP-H4), use of the anticoagulant K₂EDTA to minimize the conversion of 2-oxo-clopidogrel to H-endo, and keeping the analytes at 4 °C or on wet ice to minimize degradation of the analytes when processed and analyzed. The stability was measured as percent of each analyte remained in plasma samples after their storage for 4 h at 4 °C or in blood samples after 1 h at 4 °C. The results indicated that stability of vicagrel was increased significantly in stabilized plasma or blood samples compared with non-stabilized controls for rats and humans, respectively, and that the stability of 2-oxo-clopidogrel was increased to a certain extent. In contrast, MP-H4 formed was stable in plasma immediately after thorough mixture of MPB with blood. We conclude that the above strategy is useful for improving the stability of vicagrel, 2-oxo-clopidogrel, and H4 in rat or human plasma, and that vicagrel and its two major metabolites can be quantified accurately and simultaneously.

Enhanced responsiveness of platelets to vicagrel in IL-10-deficient mice through STAT3-dependent up-regulation of the hydrolase arylacetamide deacetylase in the intestine

BACKGROUND AND PURPOSE

Vicagrel is a novel promising antiplatelet drug designed for overcoming clopidogrel resistance. There is limited evidence indicating that exogenous IL-10 suppresses CYP3A4 activity in healthy subjects and that IL-10 knockout (KO) mice exhibit increased clopidogrel bioactivation compared with wild-type (WT) mice. In this study, we sought to determine whether IL-10 could play an important role in the metabolism of and platelet response to vicagrel in mice.

EXPERIMENTAL APPROACH

IL-10 KO and WT mice were administered vicagrel, then their plasma H4 (active metabolite of vicagrel) concentrations were determined by LC-MS/MS, and inhibition of ADP-induced whole-blood platelet aggregation by vicagrel was assessed with an aggregometer. The mRNA and protein levels of several relevant genes between IL-10 KO and WT mice were measured by qRT-PCR and Western blots, respectively. Intestinal Aadac protein levels were measured in IL-10 WT mice injected i.p. with vehicle control, Stattic, or BAY 11-7082.

KEY RESULTS

Compared with WT mice, IL-10 KO mice exhibited significantly increased plasma levels of H4 and enhanced platelet responses to vicagrel, as well as significantly higher mRNA and protein levels of arylacetamide deacetylase (Aadac) in the intestine. In WT mice, STAT3, not NF-κB, mediated Aadac expression in the intestine.

CONCLUSIONS AND IMPLICATIONS

IL-10 suppresses metabolic activation of vicagrel through down-regulation of Aadac in mouse intestine in a STAT3-dependent manner and, consequently, attenuates platelet responses to vicagrel, suggesting that the antiplatelet effect of vicagrel may be modulated by changes in plasma IL-10 levels in relevant clinical settings.

Overcoming Clopidogrel Resistance: Three Promising Novel Antiplatelet Drugs Developed in China

Clopidogrel is one of the most frequently prescribed drugs worldwide; however, the presence of clopidogrel resistance and high susceptibility to genetic variations and drug interactions are facilitating the development of other antiplatelet drugs. To overcome clopidogrel resistance, several promising clopidogrel analogues have been developed in China, such as vicagrel (and its deuterated analogues), PLD-301, and W1. These novel chemical analogues are all characterized by much faster and more efficient bioconversion to clopidogrel thiolactone (or 2-oxo-clopidogrel, the precursor of clopidogrel active metabolite) in the intestine than clopidogrel itself through bypassing the first-step P450-mediated oxidation of clopidogrel in the liver. Of them, metabolic conversion of vicagrel and PLD-301 to 2-oxo-clopidogrel is catalyzed by intestinal carboxylesterase 2 and alkaline phosphatase, respectively. In this review article, we summarized all evidence on highly efficient bioconversion to their shared precursor of clopidogrel active metabolite and the mechanisms underlying such a pronounced improvement. These drugs in the pipeline would be promising antiplatelet drugs that could be superior to clopidogrel in future patient care.

Mrp3 Transports Clopidogrel Acyl Glucuronide from the Hepatocytes into Blood

Clopidogrel acyl glucuronide (CLP-G) is a major phase II metabolite of clopidogrel generated in the liver for further excretion into urine; however, it is unclear whether CLP-G transports from hepatocytes into blood. Because multidrug resistance-associated protein 3 (MRP3) is predominantly expressed in the sinusoidal side of hepatocytes and preferentially transports glucuronide conjugates of drug metabolites from hepatocytes into bloodstream, we hypothesized that MRP3 could be such an efflux transporter for CLP-G. In this study, we compared the liver-to-plasma ratios of clopidogrel and its metabolites (including CLP-G) between Abcc3 (ATP-binding cassette, subfamily C, member 3) knockout (KO) and wild-type (WT) mice. We also evaluated the ATP-dependent uptake of clopidogrel and CLP-G as well as estradiol-17β-d-glucuronide into human recombinant MRP3 inside-out membrane vesicles in the presence or absence of ATP. The results indicated that the liver-to-plasma ratio of CLP-G was 11-fold higher in KO mice than in WT mice, and that uptake of CLP-G (1 or 10 μM each) into the membrane vesicles was 11.8- and 3.8-fold higher in the presence of ATP than in the presence of AMP, respectively. We conclude that Mrp3 transports CLP-G from the hepatocytes into blood in an ATP-dependent manner.