Evaluation of CK2 inhibitor (E)-3-(2,3,4,5-tetrabromophenyl)acrylic acid (TBCA) in regulation of platelet function

Current concepts and novel targets for antiplatelet therapy

Platelets have a crucial role in haemostasis and atherothrombosis. Pharmacological control of platelet hyper-reactivity has become a cornerstone in the prevention of thrombo-ischaemic complications in atherosclerotic diseases. Current antiplatelet therapies substantially improve clinical outcomes in patients with coronary artery disease, but at the cost of increased risk of bleeding. Beyond their role in thrombosis, platelets are known to regulate inflammatory (thrombo-inflammatory) and microcirculatory pathways. Therefore, controlling platelet hyper-reactivity might have implications for both tissue inflammation (myocardial ischaemia) and vascular inflammation (vulnerable plaque formation) to prevent atherosclerosis. In this Review, we summarize the pathophysiological role of platelets in acute myocardial ischaemia, vascular inflammation and atherosclerotic progression. Furthermore, we highlight current clinical concepts of antiplatelet therapy that have contributed to improving patient care and have facilitated more individualized therapy. Finally, we discuss novel therapeutic targets and compounds for antiplatelet therapy that are currently in preclinical development, some of which have a more favourable safety profile than currently approved drugs with regard to bleeding risk. These novel antiplatelet targets might offer new strategies to treat cardiovascular disease.

Strategies of Targeting CK2 in Drug Discovery: Challenges, Opportunities, and Emerging Prospects

CK2 (casein kinase 2) is a serine/threonine protein kinase that is ubiquitous in eukaryotic cells and plays important roles in a variety of cellular functions, including cell growth, apoptosis, circadian rhythms, DNA damage repair, transcription, and translation. CK2 is involved in cancer pathogenesis and the occurrence of many diseases. Therefore, targeting CK2 is a promising therapeutic strategy. Although many CK2-specific small-molecule inhibitors have been developed, only CX-4945 has progressed to clinical trials. In recent years, novel CK2 inhibitors have gradually become a research hotspot, which is expected to overcome the limitations of traditional inhibitors. Herein, we summarize the structure, biological functions, and disease relevance of CK2 and emphatically analyze the structure-activity relationship (SAR) and binding modes of small-molecule CK2 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CK2 for clinical practice.

Adiponectin receptor agonist AdipoRon modulates human and mouse platelet function

Adiponectin, an adipokine secreted by adipocytes, has anti-atherosclerotic and antithrombotic activities. AdipoRon is synthetic small molecule adiponectin receptor agonist. In this study, we investigated the effect of AdipoRon on platelet activation and thrombus formation. Washed human platelets were prepared from the peripheral blood of healthy donors. In a series of in vitro platelet functional assays, pre-treatment with AdipoRon (10, 20, 40 µg/mL) dose-dependently inhibited the aggregation, granule secretion and spreading of washed human platelets. We showed that AdipoRon (20, 40 µg/mL) significantly inhibited AMPK, Syk, PLCγ2, PI3K, Akt, p38-MAPK and ERK1/2 signalling pathways in washed human platelets. In addition, we demonstrated that the phosphorylation of CKII at Tyr255 was an important mechanism of the integrin αIIbβ3-mediated platelet activation. Meanwhile, AdipoR1 deficiency impaired the inhibitory effect of AdipoRon on mouse platelets. In ferric chloride-induced carotid injury model, injection of AdipoRon (5 or 12.5 mg/kg, iv) significantly attenuated arterial thrombosis. In conclusion, AdipoRon attenuates platelet function via the AdipoR1/AMPK/CKII/PI3K/AKT signalling pathways, while exerting a protective effect against arterial thrombosis. This study offers new insights into the fields of cardiovascular disease and antiplatelet drug discovery.Schematic model of AdipoRon regulating platelet activation. (BioRender.com).

Molecular mapping of platelet hyperreactivity in diabetes: the stress proteins complex HSPA8/Hsp90/CSK2α and platelet aggregation in diabetic and normal platelets

The molecular understanding of the pathophysiological changes elicited by diabetes in platelets may help in further elucidating the involvement of this pseudo-cell in the increased risk of developing cardiovascular disease and thrombosis in diabetic subjects. We aimed to investigate the differential characteristics of platelets from diabetic patients and nondiabetic controls to unveil the molecular mechanisms behind the increased platelet reactivity in diabetes. We compared platelets from diabetic and control subjects by 2 dimensional-electrophoresis followed by mass spectrometry. Changes in selected differential proteins were validated by immunoprecipitation assays and western blot. Platelet aggregation was measured by light transmittance aggregometry induced by collagen and ADP, and dynamic coagulation analysis of whole blood was measured by thromboelastometry. We observed significant differences in proteins related to platelet aggregation, cell migration, and cell homeostasis. Subjects with diabetes showed higher platelet aggregation and thrombogenicity and higher contents of the stress-related protein complex HSPA8/Hsp90/CSK2α than nondiabetic subjects. Changes in the chaperones HSPA8 and Hsp90, and in CSK2α protein contents correlated with changes in platelet aggregation and blood coagulation activity. In conclusion, the complex HSPA8/Hsp90/CSK2α is involved in diabetes-related platelet hyperreactivity. The role of the HSPA8/Hsp90/CSK2α complex may become a molecular target for the development of future preventive and therapeutic strategies for platelet dysfunction associated with diabetes and its complications.

Ellagic acid, extracted from Sanguisorba officinalis, induces G1 arrest by modulating PTEN activity in B16F10 melanoma cells

In Chinese medicine, herbal medicine is commonly used to treat individuals suffering from many types of diseases. We thus expected that some herbal medicines would contain promising compounds for cancer chemotherapy. Indeed, we found that Sanguisorba officinalis extracts strongly inhibit the growth of B16F10 melanoma cells, and we identified ellagic acid (EA) as the responsible ingredient. B16F10 cells treated with EA exhibited strong G1 arrest accompanied by accumulation of p53, followed by inactivation of AKT. Addition of a PTEN inhibitor, but not a p53 inhibitor, abrogated the EA-induced AKT inactivation and G1 arrest. The PTEN inhibitor also diminished EA-induced p53 accumulation. Furthermore, EA apparently increased the protein phosphatase activity of PTEN, as demonstrated by the reduced phosphorylation level of FAK, a protein substrate of PTEN. Furthermore, an in vitro PTEN phosphatase assay on PIP3 showed the direct modulation of PTEN activity by EA. These results suggest that EA functions as an allosteric modulator of PTEN, enhancing its protein phosphatase activity while inhibiting its lipid phosphatase activity. It is notable that a combination of EA and cisplatin, a widely used chemotherapy agent, dramatically enhanced cell death in B16F10 cells, suggesting a promising strategy in chemotherapy.

Function of protein kinase CK2 in thrombus formation

Thrombus formation is dependent on the interaction of platelets, leukocytes and endothelial cells as well as proteins of the coagulation cascade. This interaction is tightly controlled by phospho-regulated pathways involving protein kinase CK2. A growing number of studies have demonstrated an important role of this kinase in the regulation of primary and secondary hemostasis. Inhibition of CK2 downregulates the expression of important adhesion molecules on platelets and endothelial cells, such as glycoprotein (GP)IIb/IIIa, P-selectin, von Willebrand factor and vascular cell adhesion molecule. Moreover, the reduced CK2-dependent phosphorylation of different coagulation factors prevents the conversion of fibrinogen to fibrin. Targeting these mechanisms may open the door for the development of novel anti-thrombotic therapies.

CK2β regulates thrombopoiesis and Ca2+-triggered platelet activation in arterial thrombosis

CK2β is critically required for thrombopoiesis by regulating tubulin polymerization, MK fragmentation, and proplatelet formation. CK2β facilitates inositol triphosphate–mediated increase of cytosolic Ca2+ and is essential for platelet activation in arterial thrombosis in vivo.

A Selective Biligand Inhibitor of CK2 Increases Caspase-3 Activity in Cancer Cells and Inhibits Platelet Aggregation

Cancer cells express high levels of CK2, and its inhibition leads to apoptosis. CK2 has therefore emerged as a new drug target for cancer therapy. A biligand inhibitor ARC-772 was constructed by conjugating 4-(2-amino-1,3-thiazol-5-yl)benzoic acid and a carboxylate-rich peptoid. ARC-772 was found to bind CK2 with a K_d value of 0.3 nm and showed remarkable CK2 inhibitory selectivity in a panel of 140 protein kinases (Gini coefficient: 0.75 at c=100 nm). ARC-775, the acetoxymethyl ester prodrug of ARC-772, was efficiently taken up by cells. Once internalized, the inhibitor is activated by cellular esterase activity. In HeLa cancer cells ARC-775 was found to activate caspase-3 (an apoptosis marker) at sub-micromolar concentrations (EC₅₀ =0.3 μm), a 20-fold lower extracellular concentration than CX-4945, the only CK2 inhibitor under clinical trials. At micromolar concentrations, ARC-775 was also found to inhibit ADP-induced aggregation of human platelets. The overall results of this study demonstrate that oligo-anionic biligand inhibitors have good potential for drug development.

New insights on thyroid hormone mediated regulation of herpesvirus infections

Thyroid hormone (T₃) has been suggested to participate in the regulation of herpesvirus replication during reactivation. Clinical observations and in vivo experiments suggest that T₃ are involved in the suppression of herpes virus replication. In vitro, differentiated LNCaP cells, a human neuron-like cells, further resisted HSV-1 replication upon addition of T₃. Previous studies indicate that T₃ controlled the expression of several key viral genes via its nuclear receptors in differentiated LNCaP cells. Additional observation showed that differentiated LNCaP cells have active PI3K signaling and inhibitor LY294002 can reverse T₃-mediated repression of viral replication. Active PI3K signaling has been linked to HSV-1 latency in neurons. The hypothesis is that, in addition to repressing viral gene transcription at the nuclear level, T₃ may influence PI3K signaling to control HSV-1 replication in human neuron-like cells. We review the genomic and non-genomic regulatory roles of T₃ by examining the phosphoinositide 3-kinase (PI3K) pathway gene expression profile changes in differentiated LNCaP cells under the influence of hormone. The results indicated that 15 genes were down-regulated and 22 genes were up-regulated in T₃-treated differentiated LNCaP cells in comparison to undifferentiated state. Of all these genes, casein kinase 2 (CK2), a key component to enhance PI3K signaling pathway, was significantly increased upon T₃ treatment only while the cells were differentiated. Further studies revealed that CK2 inhibitors tetrabrominated cinnamic acid (TBCA) and 4, 5, 6, 7-tetrabromo-2H-benzotriazole (TBB) both reversed the T₃-mediated repression of viral replication. Together these observations suggested a new approach to understanding the roles of T₃ in the complicated regulation of HSV-1 replication during latency and reactivation.

Casein kinases as potential therapeutic targets

INTRODUCTION

The conventional term 'casein kinase' (CK) denotes three classes of kinases - CK1, CK2 and Golgi-CK (G-CK)/Fam20C (family with sequence similarity 20, member C) - sharing the ability to phoshorylate casein in vitro, but otherwise unrelated to each other. All CKs have been reported to be implicated in human diseases, and reviews individually dealing with the druggability of CK1 and CK2 are available. Our aim is to provide a comparative analysis of the three classes of CKs as therapeutic targets.

AREAS COVERED

CK2 is the CK for which implication in neoplasia is best documented, with the survival of cancer cells often relying on its overexpression. An ample variety of cell-permeable CK2 inhibitors have been developed, with a couple of these now in clinical trials. Isoform-specific CK1 inhibitors that are expected to play a beneficial role in oncology and neurodegeneration have been also developed. In contrast, the pathogenic potential of G-CK/Fam20C is caused by its loss of function. Activators of Fam20C, notably sphingolipids and their analogs, may prove beneficial in this respect.

EXPERT OPINION

Optimization of CK2 and CK1 inhibitors will prove useful to develop new therapeutic strategies for treating cancer and neurodegenerative disorders, while the design of potent activators of G-CK/Fam20C will provide a new tool in the fields of bio-mineralization and hypophosphatemic diseases.

Luteolin inhibits behavioral sensitization by blocking methamphetamine-induced MAPK pathway activation in the caudate putamen in mice

Goal

To investigate the effect of luteolin on methamphetamine (MA)-induced behavioral sensitization and mitogen-activated protein kinase (MAPK) signal transduction pathway activation in mice.

Methods

Mice received a single dose of MA to induce hyperactivity or repeated intermittent intraperitoneal injections of MA to establish an MA-induced behavioral sensitization mouse model. The effect of luteolin on the development and expression of MA-induced hyperactivity and behavioral sensitization was examined. The expression and activity of ΔFosB and the levels of phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), phosphorylated c-Jun N-terminal kinase (pJNK), and phosphorylated p38 mitogen-activated protein kinase (pp38) in the caudate putamen (CPu) were measured by western blot.

Results

Luteolin significantly decreased hyperactivity as well as the development and expression of MA-induced behavioral sensitization in mice. ΔFosB, pERK1/2, and pJNK levels in the CPu were higher in MA-treated mice than in control mice, whereas the pp38 level did not change. Injection of luteolin inhibited the MA-induced increase in ΔFosB, pERK1/2, and pJNK levels, but did not affect the pp38 level.

Conclusions

Luteolin inhibits MA-induced hyperactivity and behavioral sensitization in mice through the ERK1/2/ΔFosB pathway. Furthermore, the JNK signaling pathway might be involved in MA-induced neurodegeneration in the CPu, and luteolin inhibits this process.