Targeting Thymidine Phosphorylase With Tipiracil Hydrochloride Attenuates Thrombosis Without Increasing Risk of Bleeding in Mice.

OBJECTIVE: Current antiplatelet medications increase the risk of bleeding, which leads to a clear clinical need in developing novel mechanism-based antiplatelet drugs. TYMP (Thymidine phosphorylase), a cytoplasm protein that is highly expressed in platelets, facilitates multiple agonist-induced platelet activation, and enhances thrombosis. Tipiracil hydrochloride (TPI), a selective TYMP inhibitor, has been approved by the Food and Drug Administration for clinical use. We tested the hypothesis that TPI is a safe antithrombotic medication. Approach and Results: By coexpression of TYMP and Lyn, GST (glutathione S-transferase) tagged Lyn-SH3 domain or Lyn-SH2 domain, we showed the direct evidence that TYMP binds to Lyn through both SH3 and SH2 domains, and TPI diminished the binding. TYMP deficiency significantly inhibits thrombosis in vivo in both sexes. Pretreatment of platelets with TPI rapidly inhibited collagen- and ADP-induced platelet aggregation. Under either normal or hyperlipidemic conditions, treating wild-type mice with TPI via intraperitoneal injection, intravenous injection, or gavage feeding dramatically inhibited thrombosis without inducing significant bleeding. Even at high doses, TPI has a lower bleeding side effect compared with aspirin and clopidogrel. Intravenous delivery of TPI alone or combined with tissue plasminogen activator dramatically inhibited thrombosis. Dual administration of a very low dose of aspirin and TPI, which had no antithrombotic effects when used alone, significantly inhibited thrombosis without disturbing hemostasis. CONCLUSIONS: This study demonstrated that inhibition of TYMP, a cytoplasmic protein, attenuated multiple signaling pathways that mediate platelet activation, aggregation, and thrombosis. TPI can be used as a novel antithrombotic medication without the increase in risk of bleeding.

CD36 Enhances Vascular Smooth Muscle Cell Proliferation and Development of Neointimal Hyperplasia.

Objective- Dysregulated proliferation of vascular smooth muscle cells (VSMC) plays an essential role in neointimal hyperplasia. CD36 functions critically in atherogenesis and thrombosis. We hypothesize that CD36 regulates VSMC proliferation and contributes to the development of obstructive vascular diseases. Approach and Results- We found by immunofluorescent staining that CD36 was highly expressed in human vessels with obstructive diseases. Using guidewire-induced carotid artery injury and shear stress-induced intima thickening models, we compared neointimal hyperplasia in Apoe-/-, Cd36-/- /Apoe-/-, and CD36 specifically deleted in VSMC (VSMC cd36-/-) mice. CD36 deficiency, either global or VSMC-specific, dramatically reduced injury-induced neointimal thickening. Correspondingly, carotid artery blood flow was significantly increased in Cd36-/- /Apoe-/- compared with Apoe-/- mice. In cultured VSMCs from thoracic aorta of wild-type and Cd36-/- mice, we found that loss of CD36 significantly decreased serum-stimulated proliferation and increased cell populations in S phase, suggesting that CD36 is necessary for VSMC S/G2-M-phase transition. Treatment of VSMCs with a TSR (thrombospondin type 1 repeat) peptide significantly increased wild-type, but not Cd36-/- VSMC proliferation. TSR or serum treatment significantly increased cyclin A expression in wild-type, but not in Cd36-/- VSMCs. STAT3 (signal transducer and activator of transcription), which reportedly enhances both VSMC differentiation and maturation, was higher in Cd36-/- VSMCs. CD36 deficiency significantly decreased expression of Col1A1 (type 1 collagen A1 chain) and TGF-ß1 (transforming growth factor beta 1), and increased expression of contractile proteins, including calponin 1 and smooth muscle α actin, and dramatically increased cell contraction. Conclusions- CD36 promotes VSMC proliferation via upregulation of cyclin A expression that contributes to the development of neointimal hyperplasia, collagen deposition, and obstructive vascular diseases.

Sodium/Potassium ATPase Alpha 1 Subunit Fine-tunes Platelet GPCR Signaling Function and is Essential for Thrombosis.

Background: Thrombosis is a major cause of myocardial infarction and ischemic stroke. The sodium/potassium ATPase (NKA), comprising α and ß subunits, is crucial in maintaining intracellular sodium and potassium gradients. However, the role of NKA in platelet function and thrombosis remains unclear. Methods: We utilized wild-type (WT, α1+/+) and NKA α1 heterozygous (α1+/-) mice, aged 8 to 16 weeks, of both sexes. An intravital microscopy-based, FeCl3-induced carotid artery injury thrombosis model was employed for in vivo thrombosis assessment. Platelet transfusion assays were used to evaluate platelet NKA α1 function on thrombosis. Human platelets isolated from healthy donors and heart failure patients treated with/without digoxin were used for platelet function and signaling assay. Complementary molecular approaches were used for mechanistic studies. Results: NKA α1 haplodeficiency significantly reduced its expression on platelets without affecting sodium homeostasis. It significantly inhibited 7.5% FeCl3-induced thrombosis in male but not female mice without disturbing hemostasis. Transfusion of α1+/-, but not α1+/+, platelets to thrombocytopenic WT mice substantially prolonged thrombosis. Treating WT mice with low-dose ouabain or marinobufagenin, both binding NKA α1 and inhibiting its ion-transporting function, markedly inhibited thrombosis in vivo. NKA α1 formed complexes with leucine-glycine-leucine (LGL)-containing platelet receptors, including P2Y12, PAR4, and thromboxane A2 receptor. This binding was significantly attenuated by LGL>SFT mutation or LGL peptide. Haplodeficiency of NKA α1 in mice or ouabain treatment of human platelets notably inhibited ADP-induced platelet aggregation. While not affecting 10% FeCl3-induced thrombosis, NKA α1 haplodeficiency significantly prolonged thrombosis time in mice treated with an ineffective dose of clopidogrel. Conclusion: NKA α1 plays an essential role in enhancing platelet activation through binding to LGL-containing platelet GPCRs. NKA α1 haplodeficiency or inhibition with low-dose ouabain and marinobufagenin significantly inhibited thrombosis and sensitized clopidogrel's anti-thrombotic effect. Targeting NKA α1 emerges as a promising antiplatelet and antithrombotic therapeutic strategy.

Inferring China's excess mortality during the COVID-19 pandemic using online mourning and funeral search volume.

We construct a mourning and funeral index, using online search volume for "wreath and elegiac couplet", "obituary", "mortuary house", "cinerary casket", "cremation" and "pass away", to infer excess cases of mortality in China during the COVID-19 pandemic. During the 3-month period (December 2022-February 2023) after China ended its Zero-COVID policy, there were around 712 thousand excess cases of mortality. These excess cases of mortality, bench marked against the 2-year period preceding the pandemic, could be directly or indirectly related to COVID-19. During the 35-month Zero-COVID regime (January 2020-November 2022), the excess death toll was a negative 1480 thousand. Overall, by delaying the surge in infections, China might have saved 767 thousand lives. While these estimates are based on various assumptions and can be imprecise, China's COVID-19 experience could reasonably be characterized by a sharp surge in deaths after its departure from Zero-COVID and a steady pattern of lives saved during the Zero-COVID regime.

Thymidine Phosphorylase Deficiency or Inhibition Preserves Cardiac Function in Mice With Acute Myocardial Infarction.

Background Ischemic cardiovascular disease is the leading cause of death worldwide. Current pharmacologic therapy has multiple limitations, and patients remain symptomatic despite maximal medical therapies. Deficiency or inhibition of thymidine phosphorylase (TYMP) in mice reduces thrombosis, suggesting that TYMP could be a novel therapeutic target for patients with acute myocardial infarction (AMI). Methods and Results A mouse AMI model was established by ligation of the left anterior descending coronary artery in C57BL/6J wild-type and TYMP-deficient (Tymp-/-) mice. Cardiac function was monitored by echocardiography or Langendorff assay. TYMP-deficient hearts had lower baseline contractility. However, cardiac function, systolic left ventricle anterior wall thickness, and diastolic wall strain were significantly greater 4 weeks after AMI compared with wild-type hearts. TYMP deficiency reduced microthrombus formation after AMI. TYMP deficiency did not affect angiogenesis in either normal or infarcted myocardium but increased arteriogenesis post-AMI. TYMP deficiency enhanced the mobilization of bone marrow stem cells and promoted mesenchymal stem cell (MSC) proliferation, migration, and resistance to inflammation and hypoxia. TYMP deficiency increased the number of larger MSCs and decreased matrix metalloproteinase-2 expression, resulting in a high homing capability. TYMP deficiency induced constitutive AKT phosphorylation in MSCs but reduced expression of genes associated with retinoid-interferon-induced mortality-19, a molecule that enhances cell death. Inhibition of TYMP with its selective inhibitor, tipiracil, phenocopied TYMP deficiency, improved post-AMI cardiac function and systolic left ventricle anterior wall thickness, attenuated diastolic stiffness, and reduced infarct size. Conclusions This study demonstrated that TYMP plays an adverse role after AMI. Targeting TYMP may be a novel therapy for patients with AMI.

Predicting Drug Blood-Brain Barrier Penetration with Adverse Event Report Embeddings.

Adverse event reports (AER) are widely used for post-market drug safety surveillance and drug repurposing, with the assumption that drugs with similar side-effects may have similar therapeutic effects also. In this study, we used distributed representations of drugs derived from the Food and Drug Administration (FDA) AER system using aer2vec, a method of representing AER, with drug embeddings emerging from a neural network trained to predict the probability of adverse drug effects given observed drugs. We combined these representations with molecular features to predict permeability of the blood-brain barrier to drugs, a prerequisite to their application to treat conditions of the central nervous system. Across multiple machine learning classifiers, the addition of distributed representations improved performance over prior methods using drug-drug similarity estimates derived from discrete representations of AER system data. Embedding-based approaches outperformed those using discrete statistics, with improvements in absolute AUC of 5% and 9%, corresponding to improvements of 9% and 13% over performance with molecular features only. Performance was retained when reducing embedding dimensions from 500 to 6, indicating that they are neither attributable to overfitting, nor to a difference in the number of trainable parameters. These results indicate that aer2vec distributed representations carry information that is valuable for drug repurposing.

Combination targeting of 'platelets + fibrin' enhances clot anchorage efficiency of nanoparticles for vascular drug delivery.

Occlusive thrombosis is a central pathological event in heart attack, stroke, thromboembolism, etc. Therefore, pharmacological thrombolysis or anticoagulation is used for treating these diseases. However, systemic administration of such drugs causes hemorrhagic side-effects. Therefore, there is significant clinical interest in strategies for enhanced drug delivery to clots while minimizing systemic effects. One such strategy is by using drug-carrying nanoparticles surface-decorated with clot-binding ligands. Efforts in this area have focused on binding to singular targets in clots, e.g. platelets, fibrin, collagen, vWF or endothelium. Targeting vWF, collagen or endothelium maybe sub-optimal since in vivo these entities will be rapidly covered by platelets and leukocytes, and thus inaccessible for sufficient nanoparticle binding. In contrast, activated platelets and fibrin are majorly accessible for particle-binding, but their relative distribution in clots is highly heterogeneous. We hypothesized that combination-targeting of 'platelets + fibrin' will render higher clot-binding efficacy of nanoparticles, compared to targeting platelets or fibrin singularly. To test this, we utilized liposomes as model nanoparticles, decorated their surface with platelet-binding peptides (PBP) or fibrin-binding peptides (FBP) or combination (PBP + FBP) at controlled compositions, and evaluated their binding to human blood clots in vitro and in a mouse thrombosis model in vivo. In parallel, we developed a computational model of nanoparticle binding to single versus combination entities in clots. Our studies indicate that combination targeting of 'platelets + fibrin' enhances the clot-anchorage efficacy of nanoparticles while utilizing lower ligand densities, compared to targeting platelets or fibrin only. These findings provide important insights for vascular nanomedicine design.