A cell-based high-throughput screen identifies drugs that cause bleeding disorders by off-targeting the vitamin K cycle

Oscillatory shear stress promotes endothelial senescence and atherosclerosis via STING activation

Endothelial dysfunction is an initiating factor in atherosclerosis. Endothelial cells (ECs) are constantly subject to blood flow shear stress, and atherosclerotic plaques tend to occur in aortic bends or bifurcations impaired by low oscillatory shear stress (OSS). However, the mechanism that how OSS affects the initiation and progression of atherosclerosis remains to be explored. Here, we first reported that OSS can promote endothelial dysfunction and atherogenesis in vivo and in vitro by activating STING pathway. Mechanistically, at atherosclerosis-prone areas, OSS caused mitochondria damage in ECs, leading to the leakage of mitochondrial DNA (mtDNA) into the cytoplasm. The cytoplasmic mtDNA was recognized by cGAS to produce cGAMP, activating the STING pathway and leading to endothelial senescence, which resulted in endothelial dysfunction and atherosclerosis. We found that STING was activated in plaques of atherosclerotic patients and in aortic arch ECs of high-fat diet (HFD)-fed ApoeKO mice, as well as in ECs exposed to OSS. STING-specific deficiency in ECs attenuates endothelial senescence and resulted in a significant reduction in aortic arch plaque area in HFD-fed ApoeKO mice. Consistently, specific deficiency or pharmacological inhibition of STING attenuated OSS-induced senescence and endothelial dysfunction. Pharmacological depletion of mtDNA ameliorated OSS-induced senescence and endothelial dysfunction. Taken together, our study linked hemodynamics and endothelial senescence, and revealed a novel mechanism by which OSS leads to endothelial dysfunction. Our study provided new insights into the development of therapeutic strategies for endothelial senescence and atherosclerosis.

The mechanism of blood coagulation induced by sodium dehydroacetate via the regulation of the mTOR/ERK pathway in rats

Sodium dehydroacetate (DHA-S), a potent antifungal and antibacterial agent, is widely used in food, feed and cosmetics. However, recent studies have shown that DHA-S could pose a risk for human and animal health. We had previously reported that DHA-S could cause coagulation disorders in rats and chicken. In the present study, we further confirmed that DHA-S induced blood coagulation via VKORC1 and VKORC1L1 in rats, and elucidated the role played by mTOR/ERK signaling. The in vivo studies demonstrated that PT, APTT, and DHA-S content and relative protein expressions in tissues rebounded after drug withdrawal. In BRL-3A cells, 1.0 mM DHA-S increased the expression levels of mTOR, p-mTOR and p-ERK and decreased the levels of VKORC1, VKORC1L1 and Vitamin K. Rapamycin significantly decreased the expression levels of p-mTOR and p-ERK, while FR180204 (p-ERK Inhibition) lead to a decrease in p-ERK level. Rapamycin and FR180202 attenuated the inhibitory effect of DHA-S on VKORC1, VKORC1L1 and vitamin K levels. In addition, DHA-S increased the expression levels of mTOR, p-mTOR and p-ERK in male and female rat livers and prolonged PT and APTT. In summary, this study indicated that DHA-S induced blood coagulation via the modulation of the mTOR/ERK pathway in rats.

Elevated INR in a COVID-19 patient after concomitant administration of azvudine and anticoagulants

Background: Azvudine (FNC) is a promising treatment candidate for managing coronavirus disease 2019 (COVID-19). However, drug interactions with azvudine have been poorly studied, especially with no reported cases of azvudine with anticoagulants such as warfarin and rivaroxaban. Case summary: The patient was diagnosed with lower limb venous thrombosis and took warfarin regularly. The international normalized ratio (INR) was stable (2.0-3.0). However, the INR increased to 7.52 after administering azvudine. The patient had no other factors justifying this change. This increase in INR occurred again with the administration of azvudine in combination with rivaroxaban, and the INR increased to 18.91. After azvudine administration was stopped, the INR did not increase when rivaroxaban was used alone. Conclusion: Azvudine, warfarin, and rivaroxaban might have previously unidentified drug interactions that increased the INR. Therefore, the INR must be closely monitored when they are concomitantly administered in COVID-19 patients.

Integrated metabolomics and molecular docking reveal berberrubine inhibits thrombosis by regulating the vitamin K catalytic cycle in mice

OBJECTIVE

Natural product berberine was reported to inhibit platelet activation and thrombosis by suppressing the class Ⅰ PI3Kβ/Rasa3/Rap1 pathway. This study aims to investigate the effects and mechanisms of berberrubine, a main metabolite of berberine, to inhibit thrombus formation.

METHODS

Carrageenan-induced mouse tail thrombosis model was used to evaluate the effects of berberrubine hydrochloride (BBB) on thrombus formation in vivo. Non-targeted metabolomics was performed with UPLC-Q-TOF/MS to explore the potential mechanisms of BBB in inhibiting thrombosis. The effects of BBB on bleeding risk and prothrombin time were determined. And molecular docking was used to identify the possible target of BBB.

RESULTS

After oral administration, BBB significantly inhibited carrageenan-induced thrombosis in mice without prolonging bleeding time. The results of non-targeted metabolomics showed that oral BBB could regulate 'Phenylalanine, tyrosine and tryptophan biosynthesis' and 'Ubiquinone and other terpenoid-quinone biosynthesis', which is closely related to the vitamin K catalytic cycle. Molecular docking revealed BBB could combine and interact with vitamin K epoxide reductase (VKOR) and γ-Glutamyl carboxylase (GGCX), which was mutually confirmed with the experimental results that oral BBB could significantly prolong prothrombin time.

CONCLUSIONS

Integrated metabolomics and molecular docking reveal BBB inhibited thrombosis by regulating the vitamin K catalytic cycle. Our research is helpful in deeply understanding the antithrombotic material basis of oral berberine, and also could provide scientific evidence for developing new antithrombotic drugs based on BBB in the future.

A novel vitamin K derived anticoagulant tolerant to genetic variations of vitamin K epoxide reductase

BACKGROUND

Vitamin K antagonists (VKAs), such as warfarin, have remained the cornerstone of oral anticoagulation therapy in the prevention and treatment of thromboembolism for more than half a century. They function by impairing the biosynthesis of vitamin K-dependent (VKD) clotting factors through the inhibition of vitamin K epoxide reductase (VKOR). The challenge of VKAs therapy is their narrow therapeutic index and highly variable dosing requirements, which are partially the result of genetic variations of VKOR.

OBJECTIVES

The goal of this study was to search for an improved VKA that is tolerant to the genetic variations of its target enzyme.

METHODS

A series of vitamin K derivatives with benzyl and related side-chain substitutions at the 3-position of 1,4-naphthoquinone were synthesized. The role of these compounds in VKD carboxylation was evaluated by mammalian cell-based assays and conventional in vitro activity assays.

RESULTS

Our results showed that replacing the phytyl side-chain with a methylene cyclooctatetraene (COT) moiety at the 3-position of vitamin K1 converted it from a substrate to an inhibitor for VKD carboxylation. Strikingly, this COT-vitamin K derivative displayed a similar inhibition potency in warfarin-resistant VKOR mutations whose warfarin resistance varied more than 400-fold. Further characterization of COT-vitamin K for the inhibition of VKD carboxylation suggested that this compound targets multiple enzymes in the vitamin K redox cycle. Importantly, the anticoagulation effect of COT-vitamin K can be rescued with high doses of vitamin K1 .

CONCLUSION

We discovered a vitamin K analogue that functions as a VKA and is tolerant to genetic variations in the target enzyme.

γ-Glutamyl carboxylase mutations differentially affect the biological function of vitamin K-dependent proteins

γ-Glutamyl carboxylase (GGCX) is an integral membrane protein that catalyzes posttranslational carboxylation of a number of vitamin K-dependent (VKD) proteins involved in a wide variety of physiologic processes, including blood coagulation, vascular calcification, and bone metabolism. Naturally occurring GGCX mutations are associated with multiple distinct clinical phenotypes. However, the genotype-phenotype correlation of GGCX remains elusive. Here, we systematically examined the effect of all naturally occurring GGCX mutations on the carboxylation of 3 structure-function distinct VKD proteins in a cellular environment. GGCX mutations were transiently introduced into GGCX-deficient human embryonic kidney 293 cells stably expressing chimeric coagulation factor, matrix Gla protein (MGP), or osteocalcin as VKD reporter proteins, and then the carboxylation efficiency of these reporter proteins was evaluated. Our results show that GGCX mutations differentially affect the carboxylation of these reporter proteins and the efficiency of using vitamin K as a cofactor. Carboxylation of these reporter proteins by a C-terminal truncation mutation (R704X) implies that GGCX's C terminus plays a critical role in the binding of osteocalcin but not in the binding of coagulation factors and MGP. This has been confirmed by probing the protein-protein interaction between GGCX and its protein substrates in live cells using bimolecular fluorescence complementation and chemical cross-linking assays. Additionally, using a minigene splicing assay, we demonstrated that several GGCX missense mutations affect GGCX's pre-messenger RNA splicing rather than altering the corresponding amino acid residues. Results from this study interpreted the correlation of GGCX's genotype and its clinical phenotypes and clarified why vitamin K administration rectified bleeding disorders but not nonbleeding disorders.

The catalytic mechanism of vitamin K epoxide reduction in a cellular environment

Vitamin K epoxide reductases (VKORs) constitute a major family of integral membrane thiol oxidoreductases. In humans, VKOR sustains blood coagulation and bone mineralization through the vitamin K cycle. Previous chemical models assumed that the catalysis of human VKOR (hVKOR) starts from a fully reduced active site. This state, however, constitutes only a minor cellular fraction (5.6%). Thus, the mechanism whereby hVKOR catalysis is carried out in the cellular environment remains largely unknown. Here we use quantitative mass spectrometry (MS) and electrophoretic mobility analyses to show that KO likely forms a covalent complex with a cysteine mutant mimicking hVKOR in a partially oxidized state. Trapping of this potential reaction intermediate suggests that the partially oxidized state is catalytically active in cells. To investigate this activity, we analyze the correlation between the cellular activity and the cellular cysteine status of hVKOR. We find that the partially oxidized hVKOR has considerably lower activity than hVKOR with a fully reduced active site. Although there are more partially oxidized hVKOR than fully reduced hVKOR in cells, these two reactive states contribute about equally to the overall hVKOR activity, and hVKOR catalysis can initiate from either of these states. Overall, the combination of MS quantification and biochemical analyses reveals the catalytic mechanism of this integral membrane enzyme in a cellular environment. Furthermore, these results implicate how hVKOR is inhibited by warfarin, one of the most commonly prescribed drugs.