Trimucrin, an Arg-Gly-Asp containing disintegrin, attenuates myocardial ischemia-reperfusion injury in murine by inhibiting platelet function

Platelets, a Key Cell in Inflammation and Atherosclerosis Progression

Platelets play important roles in thrombosis-dependent obstructive cardiovascular diseases. In addition, it has now become evident that platelets also participate in the earliest stages of atherosclerosis, including the genesis of the atherosclerotic lesion. Moreover, while the link between platelet activity and hemostasis has been well established, the role of platelets as modulators of inflammation has only recently been recognized. Thus, through their secretory activities, platelets can chemically attract a diverse repertoire of cells to inflammatory foci. Although monocytes and lymphocytes act as key cells in the progression of an inflammatory event and play a central role in plaque formation and progression, there is also evidence that platelets can traverse the endothelium, and therefore be a direct mediator in the progression of atherosclerotic plaque. This review provides an overview of platelet interactions and regulation in atherosclerosis.

Non-hematopoietic erythropoietin-derived peptides for atheroprotection and treatment of cardiovascular diseases

Relevance: Cardiovascular diseases continue to be the leading cause of premature adult death.

Lipid profile and atherogenesis: Dislipidaemia leads to subsequent lipid accumulation and migration of immunocompetent cells into the vessel intima. Macrophages accumulate cholesterol forming foam cells – the morphological substrate of atherosclerosis in its initial stage.

Inflammation and atherogenesis: Pro-inflammatory factors provoke oxidative stress, vascular wall damage and foam cells formation.

Endothelial and mitochondrial dysfunction in the development of atherosclerosis: Endothelial mitochondria are some of the organelles most sensitive to oxidative stress. Damaged mitochondria produce excess superoxide and H2O2, which are the main factors of intracellular damage, further increasing endothelial dysfunction.

Short non-hematopoietic erythropoietin-based peptides as innovative atheroprotectors: Research in recent decades has shown that erythropoietin has a high cytoprotective activity, which is mainly associated with exposure to the mitochondrial link and has been confirmed in various experimental models. There is also a short-chain derivative, the 11-amino acid pyroglutamate helix B surface peptide (PHBSP), which selectively binds to the erythropoietin heterodymic receptor and reproduces its cytoprotective properties. This indicates the promising use of short-chain derivatives of erythropoietin for the treatment and prevention of atherosclerotic vascular injury. In the future, it is planned to study the PHBSP derivatives, the modification of which consists in adding RGD and PGP tripeptides with antiaggregant properties to the original 11-member peptide.

Erythropoietin Mimetic Peptide (pHBSP) Corrects Endothelial Dysfunction in a Rat Model of Preeclampsia

Preeclampsia is a severe disease of late pregnancy. Etiological factors and a pathogenetic pattern of events still require significant clarification, but it is now recognized that a large role is played by placentation disorders and emerging endothelial dysfunction. The administration of short-chain peptides mimicking the spatial structure of the B erythropoietin chain may become one of the directions of searching for new drugs for preeclampsia prevention and therapy. Simulation of ADMA-like preeclampsia in Wistar rats was performed by the administration of a non-selective NOS blocker L-NAME from the 14th to 20th day of pregnancy. The administration of the pHBSP at the doses of 10 µg/kg and 250 µg/kg corrected the established morphofunctional disorders. The greatest effect was observed at a dose of 250 µg/kg. There was a decrease in systolic and diastolic blood pressure by 31.2 and 32.8%, respectively (p < 0.0001), a decrease in the coefficient of endothelial dysfunction by 48.6% (p = 0.0006), placental microcirculation increased by 82.8% (p < 0.0001), the NOx concentration was increased by 42,6% (p = 0.0003), the greater omentum edema decreased by 11.7% (p = 0.0005) and proteinuria decreased by 76.1% (p < 0.0002). In addition, there was an improvement in the morphological pattern of the fetoplacental complex and the ratio of BAX to Bcl-2 expression which characterizes the apoptotic orientation of the cells.

Effect of down-regulated miR-15b-5p expression on arrhythmia and myocardial apoptosis after myocardial ischemia reperfusion injury in mice

In this study, the regulation of miR-15b-5p on myocardial ischemia reperfusion (I/R) injury-induced arrhythmia and myocardial apoptosis was investigated in mice. We observed the change in miR-15b-5p expression after mice suffered from myocardial I/R injury and the change in myocardial injury, infarct size, apoptosis, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD) and malondialdehyde (MDA) after down-regulation of miR-15b-5p expression. The negative regulation of miR-15b-5p to KCNJ2 as well as whether cardioprotective effect formed by miR-15b-5p down-regulation relied on the increase of KNCJ2 expression were measured by dual-luciferase reporter assay system. miR-15b-5p expression increased and KCNJ2 mRNA and protein expressions decreased after myocardial ischemia reperfusion (all P < 0.05). miR-15b-5p negatively regulated KCNJ2 in a targeted way. Down-regulating miR-15b-5p expression or increasing KCNJ2 expression significantly decreased the incidence of arrhythmia, infarct size and apoptosis after myocardial I/R and lowered MDA content in the myocardial tissue as well as IL-6 and TNF-α content in the blood (all P < 0.05). KCNJ2 gene knockout reversed the above cardioprotective effect formed by miR-15b-5p down-regulation (P < 0.05). Down-regulating miR-15b-5p expression or up-regulating KCNJ2 expression improves arrhythmia after mice suffered from myocardial I/R injury and inhibits myocardial apoptosis.

Improved Antithrombotic Activity and Diminished Bleeding Side Effect of a PEGylated αIIbβ3 Antagonist, Disintegrin

Polymer polyethylene glycol (PEG), or PEGylation of polypeptides improves protein drug stability by decreasing degradation and reducing renal clearance. To produce a pharmaceutical disintegrin derivative, the N-terminal PEGylation technique was used to modify the disintegrin derivative [KGDRR]trimucrin for favorable safety, pharmacokinetic profiles, and antithrombotic efficacy. We compared intact [KGDRR]trimucrin (RR) and PEGylated KGDRR (PEG-RR) by in vitro and in vivo systems for their antithrombotic activities. The activity of platelet aggregation inhibition and the bleeding tendency side effect were also investigated. PEG-RR exhibited optimal potency in inhibiting platelet aggregation of human/mouse platelet-rich plasma activated by collagen or ADP with a lower IC₅₀ than the intact derivative RR. In the illumination-induced mesenteric venous thrombosis model, RR and PEG-RR efficaciously prevented occlusive thrombosis in a dose-dependent manner. In rotational thromboelastometry assay, PEG-RR did not induce hypocoagulation in human whole blood even given at a higher concentration (30 μg/mL), while RR slightly prolonged clotting time. However, RR and PEG-RR were not associated with severe thrombocytopenia or bleeding in FcγRIIa-transgenic mice at equally efficacious antithrombotic dosages. We also found the in vivo half-life of PEGylation was longer than RR (RR: 15.65 h vs. PEG-RR: 20.45 h). In conclusion, injectable PEG-RR with prolonged half-life and decreased bleeding risk is a safer anti-thrombotic agent for long-acting treatment of thrombus diseases.

11-amino acid peptide imitating the structure of erythropoietin α-helix b improves endothelial function, but stimulates thrombosis in rats

The aim of the study was to test whether P-αB can be positioned as a preventing and treating agent for cardiovascular diseases.

Materials and methods. The study was performed on sexually mature male Wistar rats. Endothelial dysfunction was modulated by a 7-days intraperitoneal administration of L-NAME at the dose of 2.5 mg/100 g. P-αB, or erythropoietin (EPO), was used for therapy at the dose of 2.5 µg/100 g × 3 times for 7 days, the total dose was 7.5 µg/100 g. The function of endothelium was estimated by an endothelium-dependent and endothelium-independent vasodilation. In addition, a histological assessment of the abdominal aortic wall state and the analysis of eNos, Tnf and Il-1β genes expression were performed. To estimate prothrombotic properties, P-αB and EPO were administered, at the doses of 2.5 and 5 µg/100 g (3 times a day for 7 days, the total doses were 7.5 µg/100 g and 15 µg/100 g, respectively) and on the 8th day, the time of ferric (III) chloride-induced carotid artery thrombosis was estimated.

Results. Theresults of the functional tests for endothelium-dependent and endothelium-independent vasodilatation, as well as the histological picture of the aorta have evidenced that P-αB and EPO do not affect L-NAME-induced hypertension but improve the endothelium function. At the same time, P-αB shows a significantly higher endothelial-protective activity, reducing the coefficient of endothelial dysfunction from 5.1±0.15 to 2.72±0.12. In addition, P-αB has significantly increased the expression of eNos and reduced the expression level of Tnf and Il-1β mRNA genes. Carrying out Ferric (III) chloride-induced carotid artery thrombosis has revealed that P-αB (5 µg/100 g × 3 times a day for 7 days, total dose was 15 µg/100 g) has a lower but statistically significant prothrombotic activity than EPO.

Conclusion. P-αB can be positioned as an atheroprotector because of its ability to prevent the death of endothelial cells, as well as to reduce remodeling and proinflammatory activation of the vascular wall. However, the prothrombotic properties of P-αB limit its use as a preventing and treating agent for atherosclerosis-associated diseases.

Shuxuening injection protects against myocardial ischemia-reperfusion injury through reducing oxidative stress, inflammation and thrombosis

Background

Shuxuening injection (SXNI) has a good effect on cardiovascular and cerebrovascular diseases. Here, our study aims to investigate whether SXNI have the protective effect on myocardial ischemia-reperfusion injury (MIRI) and elucidate the mechanism of SXNI's cardiac protection.

Methods

In this experiment, the coronary arteries of Sprague-Dawley (SD) rats were ligated for the induction of a MIRI model. TTC staining and haematoxylin-eosin (HE), as well as troponin I (TnI), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatine kinase (CK) and CK-MB levels, were used to detect the protective effect of SXNI. In rat cardiac tissue, superoxide dismutase, catalase, glutathione and malondialdehyde (MDA) activities and glucose-regulated protein 78 (GRP78), calreticulin (CRT), CCAAT/enhancer binding protein homologous protein (CHOP) and caspase-12 expression levels were detected. In rat serum, the levels of inflammatory factors, including high-sensitivity C-reactive protein, monocyte chemoattractant protein-1, tumour necrosis factor-α, interleukin-6 (IL-6) and IL-1β, were measured by Elisa. In the rat arterial tissue, Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) expression was measured by western blot. In the rat plasma, ELISA was used to assay the levels of coagulation and plasmin system indicators, including platelet activating factor, endothelin, tissue factor (TF), plasminogen inhibitor, thromboxane B2, plasma fibrinogen.

Results

The results showed that SXNI can reduce the infarct size of myocardial tissue, decrease the myocardial enzyme and TnI levels and decrease the degree of myocardial damage compared with the model group. Additionally, SXNI can increase the activity of antioxidant enzymes, reduce the MDA level and decrease the GRP78, CRT, CHOP and caspase-12 expression levels. SXNI also decreased the levels of inflammatory cytokines in rat serum, lowered the level of procoagulant molecules in plasma and reduced the TLR4/NF-κB expression.

Conclusions

SXNI has protective effect on MIRI mainly by inhibiting oxidative stress and endoplasmic reticulum stress (ERS), thereby regulating TLR4/NF-κB pathway to reduce inflammation, and lowing procoagulant-related factors levels to reduce the risk of thrombosis.

From Discovery of Snake Venom Disintegrins to A Safer Therapeutic Antithrombotic Agent

Snake venoms affect blood coagulation and platelet function in diverse ways. Some venom components inhibit platelet function, while other components induce platelet aggregation. Among the platelet aggregation inhibitors, disintegrins have been recognized as unique and potentially valuable tools for examining cell–matrix and cell–cell interactions and for the development of antithrombotic and antiangiogenic agents according to their anti-adhesive and anti-migration effect on tumor cells and antiangiogenesis activities. Disintegrins represent a family of low molecular weight, cysteine-rich, Arg-Gly-Asp(RGD)/Lys-Gly-Asp(KGD)-containing polypeptides, which inhibit fibrinogen binding to integrin αIIbβ3 (i.e., platelet glycoprotein IIb/IIIa), as well as ligand binding to integrins αvβ3, and α5β1 expressed on cells (i.e., fibroblasts, tumor cells, and endothelial cells). This review focuses on the current efforts attained from studies using disintegrins as a tool in the field of arterial thrombosis, angiogenesis, inflammation, and tumor metastasis, and briefly describes their potential therapeutic applications and side effects in integrin-related diseases. Additionally, novel R(K)GD-containing disintegrin TMV-7 mutants are being designed as safer antithrombotics without causing thrombocytopenia and bleeding.

Platelet Contributions to Myocardial Ischemia/Reperfusion Injury

Obstruction of a coronary artery causes ischemia of heart tissue leading to myocardial infarction. Prolonged oxygen deficiency provokes tissue necrosis, which can result in heart failure and death of the patient. Therefore, restoration of coronary blood flow (reperfusion of the ischemic area) by re-canalizing the affected vessel is essential for a better patient outcome. Paradoxically, sudden reperfusion also causes tissue injury, thereby increasing the initial ischemic damage despite restoration of blood flow (=ischemia/reperfusion injury, IRI). Myocardial IRI is a complex event that involves various harmful mechanisms (e.g., production of reactive oxygen species and local increase in calcium ions) as well as inflammatory cells and signals like chemokines and cytokines. An involvement of platelets in the inflammatory reaction associated with IRI was discovered several years ago, but the underlying mechanisms are not yet fully understood. This mini review focusses on platelet contributions to the intricate picture of myocardial IRI. We summarize how upregulation of platelet surface receptors and release of immunomodulatory mediators lead to aggravation of myocardial IRI and subsequent cardiac damage by different mechanisms such as recruitment and activation of immune cells or modification of the cardiac vascular endothelium. In addition, evidence for cardioprotective roles of distinct platelet factors during IRI will be discussed.