Chlorin e6 Prevents ADP-Induced Platelet Aggregation by Decreasing PI3K-Akt Phosphorylation and Promoting cAMP Production

Influence of rose bengal on platelet aggregation activity

The goal of the study is to comparatively examine the effect of photoactivated rose bengal on platelet aggregation in vitro and in circulating blood of male Wistar rats. Platelet-rich plasma (PRP) was obtained from venous blood. The aggregation activity of platelets was determined by the turbidimetric method, the aggregation inducer was ADP at a final concentration of 1.25 μM. Rose bengal (RB) (Acros Organics, USA) was used as a photosensitizer (PS). PRP samples containing the PS were irradiated using ALOD-Izumrud laser (OOO “Alcom Medica”, Russia), λ = 532 nm, power density 0.05 W/cm2 , energy density of 6, 12 and 24 J/cm2 . The effect of photoactivated RB on the aggregation of circulating PLT was studied after laser irradiation of the femoral artery of the rats: 30 mW laser power, 2 mm spot diameter and 30 min exposure. RB at concentrations of 0.5 and 1 μg/ml was found to stimulate, and 5-10 μg/ml—to inhibit platelet aggregation. Photoactivation of RB weakens the stimulating effect of laser irradiation on the aggregation of platelets. Photodynamic modification of blood led to an increase in the in[1]tensity of platelet aggregation by 24% in comparison to the control group, and by 39.6% compared to the group without photoactivation of RB (p<0.01). The data obtained indicate that under the influence of RB photoactivation, the aggregation activity of platelets changes, the severity and direction of the effect depend on the RB concentration. Change in functional activity of platelets is one of the manifestations of photodynamic modification of blood.

Visualization of platelet recruitment to tumor lesions using highly sensitive and stable radioiodine studded gold nanoprobes

In vivo imaging of platelets will provide a better understanding of their critical roles in arterial cardiovascular disease, hemostasis, inflammation, and cancer. Here, we demonstrate the feasibility of using radioiodine studded gold nanoprobes (RIS-GNPs) as a platelet tracker for nuclear medicine imaging in tumor-bearing mice using positron emission tomography and computed tomography (PET/CT). Platelet labeling with RIS-GNPs did not alter the platelet functions, such as cellular proliferation and aggregation. PET/CT imaging clearly revealed the migration of platelets into tumor sites at 1 to 5 h post-transfer of RIS-GNP-labeled platelets, which was consistent with the biodistribution data. Our findings suggest that the imaging approach using RIS-GNPs makes it feasible to visualize the biological behavior of platelets in living organisms with cancer.

The effect of chlorin e₆ drug on platelet aggregation activity

The goal of the study is to evaluate the effect of Radachlorin (OOO “RADA-PHARMA”, Russia) (RC) on platelet aggregation in ex vivo and in vivo experiments. The experiments were conducted on male Wistar rats. Platelet aggregation activity was determined in platelet-rich plasma (PRP) using a turbidimetric method and the aggregation inducer was ADP at a final concentration of 1.25 μM. PRP samples containing RC were irradiated with ALOD-Granat laser device (OOO “Alkom Medika”, Russia) at 662 nm wavelength with 0.05 W/cm2 power density. After a 5-minute incubation of PRP with RC in the dark, dose-dependent inhibition of platelet aggregation was observed. Laser irradiation (12.5 J/cm2 and, especially, 25 J/cm2) increased the inhibitory effect of RC. 3 hours after intravenous administration of RC, the rate and intensity of platelets aggregation did not change, while disaggregation slowed down significantly. Irradiation at a dose of 5 J/cm2 did not affect the platelets aggregation kinetics, and disaggregation slowed down even more at 10 J/cm2, and at 20 J/cm2 the rate and intensity of platelets aggregation decreased, and no disaggregation occurred.

In vitro, RC inhibited the ADP-induced platelet aggregation in rats in a dose-dependent manner; after laser irradiation, this effect was enhanced significantly. The effect of RC on circulating platelets leads to a change in their functional state, which manifests in slowing down the disaggregation after exposure to ADP. After laser irradiation (10 J/cm2 and, especially, 20 J/cm2), the severity of the functional changes increases. The role of decreasing the disaggregation activity of platelets in the mechanism of vascular thrombosis in the affected area of photodynamic therapy (PDT) is discussed.

Luteolin Partially Inhibits LFA-1 Expression in Neutrophils Through the ERK Pathway

Luteolin inhibits the adhesion of neutrophils to microvascular endothelial cells and plays an important anti-inflammatory role, owing to its mechanism of suppressing the expression of lymphocyte function-associated antigen-1 (LFA-1) in the neutrophils. Our study deals with the different signaling pathways participating in LFA-1 expression in neutrophils along with the regulation of luteolin in order to elucidate new anti-inflammatory targets of luteolin, thus providing a basis for clinical applications. In our study, neutrophils were separated using density gradient centrifugation and the cAMP levels were determined using ELISA. Additionally, phosphorylation levels of p38 mitogen-activated protein kinase (MAPK), extracellular regulated protein kinase (ERK), phosphatidylinositol-3-kinase (PI3K), and Janus kinase (JAK) were also detected by Western blotting. LFA-1 expression was estimated using flow cytometry. The results showed that inhibiting agents used against p38 MAPK, ERK, PI3K, and JAK could significantly inhibit LFA-1 expression on neutrophils (p < 0.05, p < 0.01). Luteolin also induced a noteworthy elevation of cAMP in neutrophil supernatants (p < 0.01). It could also significantly inhibit ERK phosphorylation (p < 0.05, p < 0.01), and had no obvious effect on p38 MAPK phosphorylation in neutrophils (p > 0.05). However, phosphorylation of PI3K and JAK was not detected in neutrophils. To conclude, the p38 MAPK, ERK, PI3K, and JAK pathways are involved in the regulation of LFA-1 expression in neutrophils, and luteolin partially inhibits LFA-1 expression by increasing cAMP levels and suppressing ERK phosphorylation.

Schizonepeta tenuifolia inhibits collagen stimulated platelet function via suppressing MAPK and Akt signaling

The prevalence of cardiovascular diseases (CVDs) is increasing at a rapid pace in developed countries, and CVDs are the leading cause of morbidity and mortality. Natural products and ethnomedicine have been shown to reduce the risk of CVDs. Schizonepeta (S.) tenuifolia is a medicinal plant widely used in China, Korea, and Japan and is known to exhibit anti-inflammatory, antioxidant, and immunomodulatory activities. We hypothesized that given herbal plant exhibit pharmacological activities against CVDs, we specifically explored its effects on platelet function. Platelet aggregation was evaluated using standard light transmission aggregometry. Intracellular calcium mobilization was assessed using Fura-2/AM, and granule secretion (ATP release) was measured in a luminometer. Fibrinogen binding to integrin αⅡbβ3, was assessed using flow cytometry. Phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules and activation of the protein kinase B (Akt) was assessed using Western blot assays. S. tenuifolia, extract potently and significantly inhibited platelet aggregation, calcium mobilization, granule secretion, and fibrinogen binding to integrin αⅡbβ3. Moreover, all extracts significantly inhibited MAPK and Akt phosphorylation. S. tenuifolia extract inhibited platelet aggregation and granule secretion, and attenuated collagen mediated GPVI downstream signaling, indicating the potential therapeutic effects of these plant extracts on the cardiovascular system and platelet function. We suggest that S. tenuifolia extract may be a potent candidate to treat platelet-related CVDs and to be used as an antiplatelet and antithrombotic agent.

Astilbe chinensis Modulates Platelet Function via Impaired MAPK and PLCγ2 Expression

Background

Platelets play major role in maintaining hemostasis while hyperactivation of platelets may lead to arterial thrombosis. Natural products and ethnomedicine have been shown to reduce the risk of cardiovascular diseases (CVDs). Astilbe chinensis is a perennial herb found in China, Korea, Russia, and Japan, which is also known for its medicinal effects, and has been used in Korean traditional medicine to treat inflammation, cancer, chronic bronchitis, and headache. We hypothesized that given herbal plant exhibits pharmacological activities against CVDs, and we specifically explored their effects on platelet function.

Methodology

Platelet aggregation was evaluated using standard light-transmission aggregometry. Intracellular calcium mobilization was assessed using Fura-2/AM, and granule secretion (ATP release) was measured in a luminometer. Fibrinogen binding to integrin α_IIbβ₃ was assessed using flow cytometry. Phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules and activation of the phosphoinositide 3-kinase (PI3K)/Akt were assessed using western blots, and further, glycoprotein VI (GPVI) signaling components were studied using immunoprecipitation.

Key Results

A. chinensis extracts potently and significantly inhibited platelet aggregation, calcium mobilization, granule secretion, and fibrinogen binding to integrin α_IIbβ₃. Moreover, it significantly inhibited MAPK phosphorylation and expression of GPVI downstream signaling molecules.

Conclusion

A. chinensis extract inhibited platelet aggregation and granule secretion and attenuated GPVI downstream signaling, indicating the potential therapeutic effects of this plant extract on the cardiovascular system and platelet function. We suggest that given plant extract may be a potent candidate to treat platelet-related CVDs and to be used as antiplatelet agent.

The inhibitory activity of ginsenoside Rp4 in adenosine diphosphate-induced platelet aggregation

BACKGROUND

Korean ginseng, Panax ginseng Meyer, has been used as a traditional oriental medicine to treat illness and promote health for several thousand years. Ginsenosides are the main constituents for the pharmacological effects of P. ginseng. Since several ginsenosides, including ginsenoside (G)-Rg3 and G-Rp1, have reported antiplatelet activity, here we investigate the ability of G-Rp4 to modulate adenosine diphosphate (ADP)-induced platelet aggregation. The ginsenoside Rp4, a similar chemical structure of G-Rp1, was prepared from G-Rg1 by chemical modification.

METHODS

To examine the effects of G-Rp4 on platelet activation, we performed several experiments, including antiplatelet ability, the modulation of intracellular calcium concentration, and P-selectin expression. In addition, we examined the activation of integrin αIIbβ₃ and the phosphorylation of signaling molecules using fibrinogen binding assay and immunoblotting in rat washed platelets.

RESULTS

G-Rp4 inhibited ADP-induced platelet aggregation in a dose-dependent manner. We found that G-Rp4 decreased calcium mobilization and P-selectin expression in ADP-activated platelets. Moreover, fibrinogen binding to integrin αIIbβ₃ by ADP was attenuated in G-Rp4-treated platelets. G-Rp4 significantly attenuated phosphorylation of extracellular signal-regulated protein kinases 1 and 2, p38, and c-Jun N-terminal kinase, as well as protein kinase B, phosphatidylinositol 3-kinase, and phospholipase C-γ phosphorylations.

CONCLUSION

G-Rp4 significantly inhibited ADP-induced platelet aggregation and this is mediated via modulating the intracellular signaling molecules. These results indicate that G-Rp4 could be a potential candidate as a therapeutic agent against platelet-related cardiovascular diseases.

Increased prostacyclin levels inhibit the aggregation and activation of platelets via the PI3K-AKT pathway in prolonged isolated thrombocytopenia after allogeneic hematopoietic stem cell transplantation

OBJECTIVES

The aim of this study was to investigate the role of prostacyclin (PGI2) in prolonged isolated thrombocytopenia (PT) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the effect of PGI2 on the activation and aggregation of platelets in PT.

METHODS

We enrolled 37 patients with PT and 36 controls following allo-HSCT in this study. Platelet aggregation and activation and PGI2 levels were measured. Endothelial progenitor cells (EPCs) from either PT or control patients were cultured ex vivo with serum from either PT or control patients. PGI2 secretions were then measured. PGI2 was added to the platelets ex vivo, and platelet aggregation and activation and PI3K/Akt phosphorylation were analyzed.

RESULTS

A higher PGI2 level was observed in the PT patients. The activation and aggregation of platelets were significantly lower in the PT patients. EPCs from PT patients cultured in PT serum secreted higher levels of PGI2, and PGI2 inhibited platelet activation and aggregation in a concentration-dependent manner ex vivo. PI3K/Akt phosphorylation of platelets was regulated by PGI2 after allo-HSCT. Disease status, serum PGI2 level and platelet aggregation were independent risk factors in patients with PT after allo-HSCT.

CONCLUSIONS

Higher PGI2 levels and lower platelet activation and aggregation occurred simultaneously in PT patients. PGI2 inhibited platelet activation and aggregation, probably by regulating the phosphorylation of PI3K/Akt.

Anti-thrombotic effects of α-linolenic acid isolated from Zanthoxylum bungeanum Maxim seeds

Background

The current study was to evaluate the anti-thrombotic effect of alpha-linolenic acid (ALA) which was isolated and purified from Jiaomu in vivo.

Methods

The seeds were crushed and subsequently subjected to saponification, acid hydrolysis, gradient freezing, urea inclusion and complexation of silver nitrate to obtain the unsaturated fatty acids. The chemical characteristics of isolated ALA were validated by ¹HNMR, ¹³CNMR and mass spectrometry, and then the anti-thrombotic effect of ALA and its mixture with linoleic acid (1:1) were evaluated in the following experiments.

Results

The alpha-linolenic acid was isolated and purified from Jiaomu through our newly established methods. ALA and its mixture with linoleic acid can prolong the hemorrhage and coagulation time as well as enhanced the survival rate of mice subjected to collagen-adrenaline induced thrombosis. In addition, the thrombosis on A-V bypass and platelet aggregation of rats will be reduced after treated with ALA or its mixture, and the expression level of Akt and PI3K protein decreased 26% and 31%, respectively.

Conclusions

We designed and optimized a very simple and high-yield procedure to isolate ALA and linoleic acid mixture from seeds of Zanthoxylum bungeanum Maxim and demonstrated that such mixture can obtain a good anti-thrombotic effect through the modulation of PI3K/Akt signaling.