In vitro effects of nitric oxide donors on apoptosis and oxidative/nitrative protein modifications in ADP-activated platelets

Paricalcitol protects against hydrogen peroxide-induced injury in endothelial cells through suppression of apoptosis

The vascular endothelium is one of the main targets of oxidative stress which plays an important role in the pathophysiology of vascular damage. Recent studies show that vitamin D can positively regulate endothelial functions in various chronic diseases and in cases of increased oxidative stress. In our study, we investigated the restorative and protective potentials of paricalcitol which is frequently used in patients with chronic renal failure, a vitamin D analogue, in human umbilical vein endothelial cells (HUVEC) before and after H₂O₂-induced oxidative stress. Paricalcitol treatment after the oxidative stress induced by H₂O₂ increased cell viability in endothelial cells depending on the dose that was used. While paricalcitol (500 nM) decreased caspase-3 activity and mitochondrial membrane potential loss, it increased nitric oxide (NO) production and reduced glutathione (GSH) levels. Paricalcitol treatment before oxidative stress increased cell viability. It increased NO production and mitochondrial membrane potential while significantly reducing caspase-3 activity. While paricalcitol caused a significant inhibition of protein disulfide isomerase (PDI) reductase activity in healthy endothelial cells, it did not cause a significant change on the PDI reductase activity under oxidative stress conditions. Present study showed that paricalcitol has restorative and protective effects on endothelial cells against oxidative injury, but these effects occur at high concentrations of paricalcitol.

The antioxidant, anti-inflammatory, and antiplatelet effects of Ribes rubrum L. fruit extract in the diabetic rats

The prothrombotic and inflammatory state plays a significant role in the occurrence of cardiovascular complications in type 2 diabetes mellitus. In this study, the antidiabetic, anti-inflammatory, and antiplatelet potentials of the extracts obtained from Ribes rubrum were investigated. The antidiabetic, anti-inflammatory, and antioxidant activities of the ethanol and water extracts of R. rubrum were evaluated by in vitro methods. The total phenolic and flavonoid contents were also determined. The experimental diabetes model in rats was induced with streptozotocin (STZ). After hyperglycemia occurred, the ethanol extracts of R. rubrum (RRE, at 100 mg/kg and 500 mg/kg doses) were administered to the treatment groups for 14 days. Blood glucose, lipid profile, plasma, and pancreas tumor necrosis factor-α (TNF-α) levels were determined and compared at the end of the experiments. P-selectin levels and mitochondrial membrane polarization (MMP) of platelets were also measured. In vitro study, the RRE showed potent anti-inflammatory activity. Administration of RRE (at 100 mg/kg doses) to diabetic rats lowered blood glucose level insignificantly. The results showed that there was an increment in levels of TNF-α in plasma and pancreas tissue of the diabetic group compared to the control group. R. rubrum extract regulated and normalized their levels in plasma and pancreatic tissue. RRE at both doses significantly decreased platelet P-selectin levels and prevented STZ-induced loss of MMP in platelets. The results of current research indicate that RRE extract has potent anti-platelet and anti-inflammatory effects and may be beneficial in preventing diabetic complications. PRACTICAL APPLICATIONS: Hyperglycemia causes dyslipidemia, advanced oxidative stress, platelet activation, and inflammation in diabetes mellitus. Plants with various medicinal properties are of worldwide interest for the treatment of diseases due to their biological activities. In this study, the antidiabetic, anti-inflammatory, and antioxidant effects of extracts of Ribes rubrum (%100 ethanol, 50% ethanol, water) were evaluated by in vitro and in vivo methods. The diabetes model was induced with streptozotocin (STZ). The rats were divided into control, diabetic control, R. rubrum-100 mg/kg, and R. rubrum-500 mg/kg doses groups. Blood glucose levels, tumor necrosis factor-α (TNF-α), platelet P-selectin levels, mitochondrial membrane polarization of platelets were examined. The present study has shown that R. rubrum has anti-inflammatory and antiplatelet activity. R. rubrum may be beneficial in the prevention and treatment of DM complications due to its anti-inflammatory and antithrombotic effects.

Immune-relevant thrombocytes of common carp undergo parasite-induced nitric oxide-mediated apoptosis

Common carp thrombocytes account for 30-40% of peripheral blood leukocytes and are abundant in the healthy animals' spleen, the thrombopoietic organ. We show that, ex vivo, thrombocytes from healthy carp express a large number of immune-relevant genes, among which several cytokines and Toll-like receptors, clearly pointing at immune functions of carp thrombocytes. Few studies have described the role of fish thrombocytes during infection. Carp are natural host to two different but related protozoan parasites, Trypanoplasma borreli and Trypanosoma carassii, which reside in the blood and tissue fluids. We used the two parasites to undertake controlled studies on the role of fish thrombocytes during these infections. In vivo, but only during infection with T. borreli, thrombocytes were massively depleted from the blood and spleen leading to severe thrombocytopenia. Ex vivo, addition of nitric oxide induced a clear and rapid apoptosis of thrombocytes from healthy carp, supporting a role for nitric oxide-mediated control of immune-relevant thrombocytes during infection with T. borreli. The potential advantage for parasites to selectively deplete the host of thrombocytes via nitric oxide-induced apoptosis is discussed.

Activating stimuli induce platelet microRNA modulation and proteome reorganisation

Platelets carry megakaryocyte-derived mRNAs whose translation efficiency before and during activation is not known, although this can greatly affect platelet functions, both under basal conditions and in response to physiological and pathological stimuli, such as those involved in acute coronary syndromes. Aim of the present study was to determine whether changes in microRNA (miRNA) expression occur in response to activating stimuli and whether this affects activity and composition of platelet transcriptome and proteome. Purified platelet-rich plasmas from healthy volunteers were collected and activated with ADP, collagen, or thrombin receptor activating peptide. Transcriptome analysis by RNA-Seq revealed that platelet transcriptome remained largely unaffected within the first 2 hours of stimulation. In contrast, quantitative proteomics showed that almost half of > 700 proteins quantified were modulated under the same conditions. Global miRNA analysis indicated that reorganisation of platelet proteome occurring during activation reflected changes in mature miRNA expression, which therefore, appears to be the main driver of the observed discrepancy between transcriptome and proteome changes. Platelet functions significantly affected by modulated miRNAs include, among others, the integrin/cytoskeletal, coagulation and inflammatory-immune response pathways. These results demonstrate a significant reprogramming of the platelet miRNome during activation, with consequent significant changes in platelet proteome and provide for the first time substantial evidence that fine-tuning of resident mRNA translation by miRNAs is a key event in platelet pathophysiology.