Oxidative Versus Thrombotic Stimulation of Platelets Differentially activates Signalling Pathways

The use of platelet indices, plateletcrit, mean platelet volume and platelet distribution width in emergency non-traumatic abdominal surgery: a systematic review

Platelet indices (PI) -- plateletcrit, mean platelet volume (MPV) and platelet distribution width (PDW) -- are a group of derived platelet parameters obtained as a part of the automatic complete blood count. Emerging evidence suggests that PIs may have diagnostic and prognostic value in certain diseases. This study aimed to summarize the current scientific knowledge on the potential role of PIs as a diagnostic and prognostic marker in patients having emergency, non-traumatic abdominal surgery. In December 2015, we searched Medline/PubMed, Scopus and Google Scholar to identify all articles on PIs. Overall, considerable evidence suggests that PIs are altered with acute appendicitis. Although the role of PI in the differential diagnosis of acute abdomen remains uncertain, low MPV might be useful in acute appendicitis and acute mesenteric ischemia, with high MPV predicting poor prognosis in acute mesenteric ischemia. The current lack of consistency and technical standards in studies involving PIs should be regarded as a serious limitation to comparing these studies. Further large, multicentre prospective studies concurrently collecting data from different ethnicities and genders are needed before they can be used in routine clinical practice.

In vitro Incubation of Platelets with oxLDL Does Not Induce Microvesicle Release When Measured by Sensitive Flow Cytometry

Microvesicles (MVs) are submicron vesicles with sizes of 0.1–1.0 μm in diameter, released from various cell types upon activation or apoptosis. Their involvement in a variety of diseases has been intensively investigated. In blood, platelets are potent MV secretors, and oxidized low-density lipoprotein (oxLDL), a platelet ligand, induces platelet activation and thus potentially MV secretion. This interaction occurs through binding of oxLDL with CD36, located on the platelet membrane. In this study, we investigated the effect of in vitro incubation of platelets with oxLDL on MV release. Furthermore, we compared the results obtained when separating MVs larger than 0.5 μm as a measure of results obtained from less sensitive conventional flow cytometers with MVs below the 0.5 μm limit. MV size distribution was analyzed in plasma from 11 healthy volunteers (four females and seven males). MVs were identified as <1 μm and positive for lactadherin binding and cell-specific markers. Platelet-rich plasma (PRP) was incubated without and with oxLDL or LDL (as control) to investigate the impact on platelet activation, evident by release of MVs. Size-calibrated fluorescent beads were used to establish the MV gate, and separate small- and large-size vesicles. CD41⁺ and CD41⁺CD36⁺ MVs increased by six to eightfold in PRP, when left at room temperature, and the presence of cell-specific markers increased. Total MV count was unaffected. Incubations with oxLDL did not increase the MV release or affect the distribution of small- and large-size MVs. We found a large interindividual variation in the fraction of small- and large-size MVs of 73%. In conclusion, we propose that procoagulant activity and activation of platelets induced by interaction of platelet CD36 with oxLDL may not involve release of MVs. Furthermore, our results demonstrate great interindividual variability in size distribution of platelet-derived MVs and thereby stress the importance for generation of standardized protocols for MV quantification by flow cytometry.

Effects of Selenium in the MAPK Signaling Cascade

Introduction: This study aimed to discover by which mechanism selenium (Se) suppresses stimulated platelets stimulation in oxidative stress underlying diseases.

Methods: Human platelets pretreated with Se and stimulated by Cu²⁺-oxidized low density of lipoprotein (OxLDL) or thrombin before assessment of P-selectin and phosphorylated p38 mitogen-activated protein kinase (p-p38MAPK), phosphorylated Jun N-terminal kinase (p– JNK), and phosphorylated extracellular signal-regulated kinases (p-ERK1/2). All variables were measured by solid phase sandwich enzyme-linked immunosorbent assay (ELISA).

Results: Se significantly decreased Cu²⁺-OxLDL induced P-selectin expression, as well as p38 and JNK phosphorylation in platelets, but could not significantly reduce ERK1/2 phosphorylation.

Conclusion: Se suppresses inflamed platelets. This effect maybe partly mediated by the p38 or c-JNK signaling pathways. These results create possibility of new co-anti-inflammatory insight for Se in atherosclerosis.

Antioxidant and lipid-regulating effects of probucol combined with atorvastatin in patients with acute coronary syndrome

OBJECTIVE

To investigate the effects of probucol combined with atorvastatin on the serum oxidation index and lipid levels in patients diagnosed with acute coronary syndrome (ACS).

METHODS

We randomly assigned 126 ACS patients (77 males and 49 females) to the control group (atorvastatin 20 mg/day, n=62) or the treatment group (atorvastatin 20 mg/day and probucol 750 mg/day, n=64). All the patients were followed up for 12 weeks. As oxidization indices, we measured the serum levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), oxidized LDL (ox-LDL), and paraoxonase-1 (PON1) before and after treatment. We also monitored the adverse effects of the drugs during the treatment.

RESULTS

At baseline, there were no obvious differences (P>0.05) between the two groups (including age, gender, etc.). After 12 weeks of treatment, the ox-LDL levels in the treatment group were significantly lower while PON1 levels were significantly higher than those in the control group. There were no statistically significant difference between the two groups with respect to the side effects (P<0.05).

CONCLUSIONS

The combined use of atorvastatin and probucol in ACS patients could reduce ox-LDL expression and increase PON1 expression more effectively than use atorvastatin alone.