Genomic analysis reveals a cryptic pangolin species.

Eight extant species of pangolins are currently recognized. Recent studies found that two mitochondrial haplotypes identified in confiscations in Hong Kong could not be assigned to any known pangolin species, implying the existence of a species. Here, we report that two additional mitochondrial haplotypes identified in independent confiscations from Yunnan align with the putative species haplotypes supporting the existence of this mysterious species/population. To verify the new species scenario we performed a comprehensive analysis of scale characteristics and 138 whole genomes representing all recognized pangolin species and the cryptic new species, 98 of which were generated here. Our morphometric results clearly attributed this cryptic species to Asian pangolins (Manis sp.) and the genomic data provide robust and compelling evidence that it is a pangolin species distinct from those recognized previously, which separated from the Philippine pangolin and Malayan pangolin over 5 Mya. Our study provides a solid genomic basis for its formal recognition as the ninth pangolin species or the fifth Asian one, supporting a new taxonomic classification of pangolins. The effects of glacial climate changes and recent anthropogenic activities driven by illegal trade are inferred to have caused its population decline with the genomic signatures showing low genetic diversity, a high level of inbreeding, and high genetic load. Our finding greatly expands current knowledge of pangolin diversity and evolution and has vital implications for conservation efforts to prevent the extinction of this enigmatic and endangered species from the wild.

Vicagrel enhances aspirin-induced inhibition of both platelet aggregation and thrombus formation in rodents due to its decreased metabolic inactivation.

Both aspirin and vicagrel are effective antiplatelet drugs, with the potential for concomitant use as another dual-antiplatelet therapy for the prevention of recurrent thrombotic or ischemic events. Because they both are the substrates of carboxylesterase 2 (CES2), aspirin attenuated the metabolic activation of and platelet response to vicagrel in mice treated with the two drugs concomitantly. In this study, we sought to clarify whether vicagrel could affect platelet responses to aspirin and their underlying mechanisms. Plasma levels of aspirin and salicylic acid were determined by liquid chromatography-tandem mass spectrometry, inhibition of arachidonic acid (AA)-induced whole-blood platelet aggregation by aspirin was assessed with an aggregometer, and their antithrombotic effects were evaluated by arteriovenous shunt thrombosis model. The results showed that concomitant use of vicagrel (5, 10, or 20 mg/kg) led to an average of 55% and 77% increases in systemic exposure of aspirin (Cmax and AUC0-t) and 2.8-fold increase in suppression of AA-induced platelet aggregation in mice when compared with use of aspirin alone. In the rat thrombus formation model, vicagrel (1 mg/kg) enhanced inhibition of thrombosis formation by aspirin (5 mg/kg), but not vice versa. We conclude that vicagrel increases platelet responses to aspirin and also enhances inhibition of thrombus formation of aspirin due to decreased CES2-catalyzed aspirin inactivation in rodents, and that an integrated net effect on thrombus formation in vivo is superior to inhibition of AA- or ADP-induced platelet aggregation ex vivo by either of the two drugs if taken concomitantly.

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.

Aspirin Attenuates the Bioactivation of and Platelet Response to Vicagrel in Mice.

Vicagrel, a novel acetate analogue of clopidogrel, exerts more potent antiplatelet effect than clopidogrel in rodents. Relevant evidence indicated that aspirin and vicagrel are the drug substrate for carboxylesterase 2. Accordingly, it is deduced that concomitant use of aspirin could attenuate the bioactivation of and platelet response to vicagrel. To clarify whether there could be such an important drug-drug interaction, the differences in both the formation of vicagrel active metabolite H4 and the inhibition of adenosine diphosphate-induced platelet aggregation by vicagrel were measured and compared between mice treated with vicagrel alone or in combination with aspirin. The plasma H4 concentration was determined by liquid chromatography-tandem mass spectrometry, and the inhibition of platelet aggregation by vicagrel was assessed by whole-blood platelet aggregation. Compared with vicagrel (2.5 mg·kg) alone, concurrent use of aspirin (5, 10, or 20 mg·kg) significantly decreased systemic exposure of H4, an average of 38% and 41% decrease in Cmax and AUC0-∞ in mice when in combination with aspirin at 10 mg·kg, respectively. Furthermore, concomitant use of aspirin (10 mg·kg) and vicagrel (2.5 mg·kg) resulted in an average of 66% reduction in the inhibition of adenosine diphosphate-induced platelet aggregation by vicagrel. We conclude that aspirin significantly attenuates the formation of vicagrel active metabolite H4 and platelet response to vicagrel in mice, and that such an important drug-drug interaction would appear in clinical settings if vicagrel is taken with aspirin concomitantly when marketed in the future.

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-17ß-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.

Human UGT2B7 is the major isoform responsible for the glucuronidation of clopidogrel carboxylate.

Clopidogrel is predominantly hydrolyzed to clopidogrel carboxylic acid (CCA) by carboxylesterase 1, and subsequently CCA is glucuronidated to clopidogrel acyl glucuronide (CAG) by uridine diphosphate-glucuronosyltransferases (UGTs); however, the UGT isoenzymes glucuronidating CCA remain unidentified to date. In this study, the glucuronidation of CCA was screened with pooled human liver microsomes (HLMs) and 7 human recombinant UGT (rUGT) isoforms. Results indicated that rUGT2B7 exhibited the highest catalytical activity for the CCA glucuronidation as measured with a mean Vmax value of 120.9 pmol/min/mg protein, 3- to 12-fold higher than that of the other rUGT isoforms tested. According to relative activity factor approach, the relative contribution of rUGT2B7 to CCA glucuronidation was estimated to be 58.6%, with the minor contributions (3%) from rUGT1A9. Moreover, the glucuronidation of CCA followed Michaelis-Menten kinetics with a mean Km value of 372.9 µM and 296.4 µM for pooled HLMs and rUGT2B7, respectively, showing similar affinity for both. The formation of CAG was significantly inhibited by azidothymidine and gemfibrozil (well-characterized UGT2B7 substrates) in a concentration-dependent manner, or by fluconazole (a typical UGT2B7-selective inhibitor) in a time-dependent manner, for both HLMs and rUGT2B7, respectively. In addition, CCA inhibited azidothymidine glucuronidation (catalyzed almost exclusively by UGT2B7) by HLMs and rUGT2B7 in a concentration-dependent manner, indicating that CCA is a substrate of UGT2B7. These results reveal that UGT2B7 is the major enzyme catalyzing clopidogrel glucuronidation in the human liver, and that there is the potential for drug-drug interactions between clopidogrel and the other substrate drugs of UGT2B7.