Protein kinase C alpha and beta are positive regulators of thrombus formation in vivo in a zebrafish (Danio rerio) model of thrombosis

Qilong capsule alleviates ponatinib-induced ischemic stroke in a zebrafish model by regulating coagulation, inflammation and apoptosis

ETHOPHARMACOLOGICAL RELEVANCE

Qilong capsule (QLC) is a compound traditional Chinese medicine commonly used to treat ischemic stroke (IS). QLC is made of eight kinds of medicinal materials. It has two kinds of monarch medicine and six kinds of minister medicine. However, the pharmacodynamic mechanism of QLC is still unknown.

AIM OF THE STUDY

The aim of this paper was to evaluate the pharmacology mechanism of QLC against ischemic stroke through coagulation, inflammation and apoptosis.

MATERIALS AND METHODS

We used an existing zebrafish model to explore the protective mechanism of QLC on IS. We treated normally-developing zebrafish larvae with QLC and ponatinib 2 days post fertilization (dpf), and used the area of cerebral vascular thrombosis, red blood cell staining intensity, and brain cell apoptosis to quantitate QLC efficacy against IS. Evaluation of brain inflammation in zebrafish by observing macrophage aggregation and migration. In addition, we also explored the effect of QLC on zebrafish angiogenesis. Quantitative polymerase chain reaction (qPCR) was used to detect changes in the expression of genes involved in coagulation, inflammation, vascular endothelium, and apoptosis.

RESULTS

We found that QLC reduced the area affected by ponatinib-induced cerebral vascular embolism, erythrocyte staining intensity, and the number of apoptotic brain cells. For inflammation, QLC can improve the aggregation and migration of macrophages. QLC can significantly promote the formation of blood vessels in zebrafish. qPCR showed that QLC inhibited the expression of genes related to coagulation, inflammation, and apoptosis.

CONCLUSION

Qilong capsule had a significant protective efficacy in ponatinib-induced IS.

Identification of the Antithrombotic Mechanism of Leonurine in Adrenalin Hydrochloride-Induced Thrombosis in Zebrafish via Regulating Oxidative Stress and Coagulation Cascade

Thrombosis is a general pathological phenomenon during severe disturbances to homeostasis, which plays an essential role in cardiovascular and cerebrovascular diseases. Leonurine (LEO), isolated from Leonurus japonicus Houtt, showes a crucial role in anticoagulation and vasodilatation. However, the properties and therapeutic mechanisms of this effect have not yet been systematically elucidated. Therefore, the antithrombotic effect of LEO was investigated in this study. Hematoxylin-Eosin staining was used to detect the thrombosis of zebrafish tail. Fluorescence probe was used to detect the reactive oxygen species. The biochemical indexes related to oxidative stress (lactate dehydrogenase, malondialdehyde, superoxide dismutase and glutathione) and vasodilator factor (endothelin-1 and nitric oxide) were analyzed by specific commercial assay kits. Besides, we detected the expression of related genes (fga, fgb, fgg, pkcα, pkcβ, vwf, f2) and proteins (PI3K, phospho-PI3K, Akt, phospho-Akt, ERK, phospho-ERK FIB) related to the anticoagulation and fibrinolytic system by quantitative reverse transcription and western blot. Beyond that, metabolomic analyses were carried out to identify the expressions of metabolites associated with the anti-thrombosis mechanism of LEO. Our in vivo experimental results showed that LEO could improve the oxidative stress injury, abnormal platelet aggregation and coagulation dysfunction induced by adrenalin hydrochloride. Moreover, LEO restored the modulation of amino acids and inositol metabolites which are reported to alleviate the thrombus formation. Collectively, LEO attenuates adrenalin hydrochloride-induced thrombosis partly via modulating oxidative stress, coagulation cascade and platelet activation and amino acid and inositol metabolites.

Antithrombotic effect and action mechanism of Salvia miltiorrhiza and Panax notoginseng herbal pair on the zebrafish

Background

Salvia miltiorrhiza (Danshen, DS) and Panax notoginseng (Sanqi, SQ) are famous traditional Chinese herbs, and their herbal pair (DS–SQ) has been popular used as anti-thrombotic medicines. However, there is still a lack of sufficient scientific evidence to illustrate the optimum combination ratio of these two herbs as well as its action mechanisms. The purpose of this study is to investigate the anti-thrombotic effects of DS–SQ on zebrafish and explore its possible action mechanism.

Methods

Firstly, the chemical components in DS–SQ extract were analyzed by LC–ESI–MS/MS. Then, a phenylhydrazine (PHZ)-induced zebrafish thrombosis model was developed for evaluating the anti-thrombotic effects of DS–SQ extracts with different combination ratios and their nine pure compounds. Followed, Real-time quantitative PCR (RT-qPCR) assays were performed to investigate the potential antithrombotic mechanisms of DS–SQ.

Results

Thirty-three components were tentatively identified by LC–MS analysis. DS–SQ at the ratio of 10:1 presented the best anti-thrombotic effect, and rosmarinic acid, lithospermic acid and salvianolic acid B of DS showed good anti-thrombotic activity on zebrafish thrombosis model. The RT-qPCR assays indicated that DS–SQ (10:1) could cure the PHZ-induced thrombosis by downregulating the expression of PKCα, PKCβ, fga, fgb, fgg and vWF in zebrafish.

Conclusions

DS–SQ with the combination ratio of 10:1 showed optimum anti-thrombotic effect on PHZ-induced zebrafish thrombosis model, which provided a reference for reasonable clinical applications of DS–SQ herbal pair.

Functional Genomics for the Identification of Modulators of Platelet-Dependent Thrombus Formation

Despite the absence of the genome in platelets, transcription profiling provides important insights into platelet function and can help clarify abnormalities in platelet disorders. The Bloodomics Consortium performed whole-genome expression analysis comparing in vitro–differentiated megakaryocytes (MKs) with in vitro–differentiated erythroblasts and different blood cell types. This allowed the identification of genes with upregulated expression in MKs compared with all other cell lineages, among the receptors BAMBI, LRRC32, ESAM, and DCBLD2. In a later correlative analysis of genome-wide platelet RNA expression with interindividual human platelet reactivity, LLRFIP and COMMD7 were additionally identified. A functional genomics approach using morpholino-based silencing in zebrafish identified various roles for all of these selected genes in thrombus formation. In this review, we summarize the role of the six identified genes in zebrafish and discuss how they correlate with subsequently performed mouse experiments.

PKC-epsilon deficiency alters progenitor cell populations in favor of megakaryopoiesis

BACKGROUND

It has long been postulated that Protein Kinase C (PKC) is an important regulator of megakaryopoiesis. Recent contributions to the literature have outlined the functions of several individual PKC isoforms with regard to megakaryocyte differentiation and platelet production. However, the exact role of PKCε remains elusive.

OBJECTIVE

To delineate the role of PKCε in megakaryopoiesis.

APPROACH AND RESULTS

We used a PKCε knockout mouse model to examine the effect of PKCε deficiency on platelet mass, megakaryocyte mass, and bone marrow progenitor cell distribution. We also investigated platelet recovery in PKCε null mice and TPO-mediated signaling in PKCε null megakaryocytes. PKCε null mice have higher platelet counts due to increased platelet production compared to WT littermate controls (p<0.05, n = 8). Furthermore, PKCε null mice have more bone marrow megakaryocyte progenitor cells than WT littermate control mice. Additionally, thrombopoietin-mediated signaling is perturbed in PKCε null mice as Akt and ERK1/2 phosphorylation are enhanced in PKCε null megakaryocytes stimulated with thrombopoietin. Finally, in response to immune-induced thrombocytopenia, PKCε null mice recovered faster and had higher rebound thrombocytosis than WT littermate control mice.

CONCLUSIONS

Enhanced platelet recovery could be due to an increase in megakaryocyte progenitor cells found in PKCε null mice as well as enhanced thrombopoietin-mediated signaling observed in PKCε deficient megakaryocytes. These data suggest that PKCε is a negative regulator of megakaryopoiesis.

Animal Models of Thrombosis From Zebrafish to Nonhuman Primates: Use in the Elucidation of New Pathologic Pathways and the Development of Antithrombotic Drugs

Thrombosis is a leading cause of morbidity and mortality worldwide. Animal models are used to understand the pathological pathways involved in thrombosis and to test the efficacy and safety of new antithrombotic drugs. In this review, we will first describe the central role a variety of animal models of thrombosis and hemostasis has played in the development of new antiplatelet and anticoagulant drugs. These include the widely used P2Y12 antagonists and the recently developed orally available anticoagulants that directly target factor Xa or thrombin. Next, we will describe the new players, such as polyphosphate, neutrophil extracellular traps, and microparticles, which have been shown to contribute to thrombosis in mouse models, particularly venous thrombosis models. Other mouse studies have demonstrated roles for the factor XIIa and factor XIa in thrombosis. This has spurred the development of strategies to reduce their levels or activities as a new approach for preventing thrombosis. Finally, we will discuss the emergence of zebrafish as a model to study thrombosis and its potential use in the discovery of novel factors involved in thrombosis and hemostasis. Animal models of thrombosis from zebrafish to nonhuman primates are vital in identifying pathological pathways of thrombosis that can be safely targeted with a minimal effect on hemostasis. Future studies should focus on understanding the different triggers of thrombosis and the best drugs to prevent each type of thrombotic event.

Targeted laser ablation of the zebrafish larval heart induces models of heart block, valvular regurgitation, and outflow tract obstruction

Mammalian models of cardiac disease have provided unique and important insights into human disease but have become increasingly challenging to produce. The zebrafish could provide inexpensive high-throughput models of cardiac injury and repair. We used a highly targeted laser, synchronized to fire at specific phases of the cardiac cycle, to induce regional injury to the ventricle, atrioventricular (AV) cushion, and bulbus arteriosus (BA). We assessed the impact of laser injury on hearts of zebrafish early larvae at 72 h postfertilization, to different regions, recording the effects on ejection fraction (EF), heart rate (HR), and blood flow at 2 and 24 h postinjury (hpi). Laser injury to the apex, midzone, and outflow regions of the ventricle resulted in reductions of the ventricle EF at 2 hpi with full recovery of function by 24 hpi. Laser injury to the ventricle, close to the AV cushion, was more likely to cause bradycardia and atrial-ventricular dysfunction, suggestive of an electrical conduction block. At 2 hpi, direct injury to the AV cushion resulted in marked regurgitation of blood from the ventricle to the atrium. Laser injury to the BA caused temporary outflow tract obstruction with cessation of ventricle contraction and circulation. Despite such damage, 80% of embryos showed complete recovery of the HR and function within 24 h of laser injury. Precision laser injury to key structures in the zebrafish developing heart provides a range of potentially useful models of hemodynamic overload, injury, and repair.

Cytohesin-2 phosphorylation by protein kinase C relieves the constitutive suppression of platelet dense granule secretion by ADP-ribosylation factor 6

BACKGROUND

Protein kinase C (PKC) is a major regulator of platelet function and secretion. The underlying molecular pathway from PKC to secretion, however, is poorly understood. By a proteomics screen we identified the guanine nucleotide exchange factor cytohesin-2 as a candidate PKC substrate.

OBJECTIVES

We aimed to validate cytohesin-2 as a PKC substrate in platelets and to determine its role in granule secretion and other platelet responses.

METHODS AND RESULTS

Immunoprecipitation was performed with a phosphoserine PKC substrate antibody followed by mass spectrometry, leading to the identification of cytohesin-2. By western blotting we showed that different agonists induced cytohesin-2 phosphorylation by PKC. Protein function was investigated using a pharmacological approach. The cytohesin inhibitor SecinH3 significantly enhanced platelet dense granule secretion and aggregation, as measured by lumi-aggregometry. Flow cytometry data indicate that α-granule release and integrin αII b β3 activation were not affected by cytohesin-2 inhibition. Lysosome secretion was assessed by a colorimetric assay and was also unchanged. As shown by western blotting, ARF6 interacted with cytohesin-2 and was present in an active GTP-bound form under basal conditions. Upon platelet stimulation, this interaction was largely lost and ARF6 activation decreased, both of which could be rescued by PKC inhibition.

CONCLUSIONS

Cytohesin-2 constitutively suppresses platelet dense granule secretion and aggregation by keeping ARF6 in a GTP-bound state. PKC-mediated phosphorylation of cytohesin-2 relieves this inhibitory effect, thereby promoting platelet secretion and aggregation.

Zebrafish thrombocytes: functions and origins

Platelets play an important role in mammalian hemostasis. Thrombocytes of early vertebrates are functionally equivalent to mammalian platelets. A substantial amount of research has been done to study platelet function in humans as well as in animal models. However, to date only limited functional genomic studies of platelets have been performed but are low throughput and are not cost-effective. Keeping this in mind we introduced zebrafish, a vertebrate genetic model to study platelet function. We characterized zebrafish thrombocytes and established functional assays study not only their hemostatic function but to also their production. We identified a few genes which play a role in their function and production. Since we introduced the zebrafish model for the study of hemostasis and thrombosis, other groups have adapted this model to study genes that are associated with thrombocyte function and a few novel genes have also been identified. Furthermore, transgenic zebrafish with GFP-tagged thrombocytes have been developed which helped to study the production of thrombocytes and their precursors as well as their functional roles not only in hemostasis but also hematopoiesis. This paper integrates the information available on zebrafish thrombocyte function and its formation.