Lactate production by thrombin-activated platelets of patients with primary thrombocythemia

Cardiovascular Dysfunction in COVID-19: Association Between Endothelial Cell Injury and Lactate

Coronavirus disease 2019 (COVID-19), an infectious respiratory disease propagated by a new virus known as Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), has resulted in global healthcare crises. Emerging evidence from patients with COVID-19 suggests that endothelial cell damage plays a central role in COVID-19 pathogenesis and could be a major contributor to the severity and mortality of COVID-19. Like other infectious diseases, the pathogenesis of COVID-19 is closely associated with metabolic processes. Lactate, a potential biomarker in COVID-19, has recently been shown to mediate endothelial barrier dysfunction. In this review, we provide an overview of cardiovascular injuries and metabolic alterations caused by SARS-CoV-2 infection. We also propose that lactate plays a potential role in COVID-19-driven endothelial cell injury.

Platelet Function and Turnover in Essential Thrombocythemia: A Systematic Review

Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by increased platelet counts. ET has an incidence of 0.6 to 2.5 per 100,000 per year in Europe and North America. The disease is characterized by an increased thromboembolic risk, possibly caused by increased platelet counts. Furthermore, increased platelet function and/or increased platelet turnover may play a role. We aimed to explore: (1) whether platelet function and platelet turnover are increased in ET patients compared with healthy controls, and (2) whether these parameters are associated with increased thromboembolic risk and, therefore, may support decision-making on treatment in ET patients. We performed a systematic literature search on March 20, 2020 in Embase and PubMed following the Preferred Reporting Items for Systematic and Meta-Analysis (PRISMA) guidelines. In total, 1,923 articles were identified, 38 of which were included according to prespecified inclusion and exclusion criteria. Among the 38 studies, platelet activation (CD36 and CD62P) was investigated in 18 studies and was found to be increased in 12 of these. Platelet aggregation was investigated in 21 studies and was reported to be reduced in 20 of them. Platelet turnover (immature platelet count and mean platelet volume) was investigated in five studies with inconclusive results. No parameters were reported to predict the risk of thromboembolic events. In conclusion, platelet activation was increased in ET patients, but platelet aggregation was reduced. Future studies exploring markers of thromboembolic risk in ET patients are warranted.

Proteome of platelets in patients with coronary artery disease

OBJECTIVE

This study aimed at investigating the protein patterns of platelets from patients with stable or acute coronary atherosclerosis (CAD), in which platelets play a key role.

MATERIALS AND METHODS

A proteomic approach was adopted to investigate specific protein patterns in platelets of patients with non-ST elevation acute coronary syndrome, stable angina, or of subjects with no history of CAD.

RESULTS

Six differentially expressed proteins were identified: two involved in energy metabolism (2-oxoglutarate dehydrogenase [OGDH], and lactate dehydrogenase [LDH]); three were associated with cytoskeleton-based processes (gamma-actin, coronin 1B, and pleckstrin); and one involved in protein degradation (proteasome subunit type 8). Expression levels of OGDH and a cleaved form of gamma-actin were significantly higher in the platelets of patients than in controls, whereas that of LDH was higher only in the platelets of patients with acute coronary disease. The increases in protein expression of OGDH and LDH are paralleled by changes in their functional activities. Coronin and proteasome subunit type 8 were less expressed in the platelets of patients, as were the basic isoforms of pleckstrin.

CONCLUSION

The platelet proteome is altered in CAD patients with stable or acute coronary syndrome possibly because of the ongoing atherosclerotic process. The identified protein changes not previously connected with CAD were an increase in the energy metabolism enzymes and alterations in the proteins associated with cytoskeleton-based processes, both of which indicate platelet activation.

Essential thrombocythemia: a review of diagnostic and pathologic features

CONTEXT

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder (CMPD) characterized predominately by thrombocytosis and abnormal megakaryocyte proliferation. The current diagnostic criteria require a combination of clinical, histologic, and cytogenetic data. The diagnosis relies largely on exclusion of other causes of thrombocytosis.

OBJECTIVE

Describe historical, clinical, and laboratory features of ET in order to understand, clarify, and more accurately diagnose this entity.

DATA SOURCES

Review contemporary and historical literature on ET and other causes of thrombocytosis.

CONCLUSIONS

ET is a relatively indolent and often asymptomatic CMPD that is characterized primarily by a sustained elevation in platelets > or = 600 x 10(3)/microL (> or = 600 x 10(9)/L), proliferating enlarged and hyperlobated megakaryocytes, and minimal to absent bone marrow fibrosis. Significant changes and revisions to the diagnostic requirements and criteria for ET have occurred during the last 30 years. Recently, a mutation in the Janus kinase 2 (JAK2) gene has been found in a significant number of cases of ET and other CMPDs. In up to 57% of ET cases, a mutation in the JAK2 gene can be detected. In the absence of a JAK2 mutation and features of another CMPD, the diagnosis of ET remains a diagnosis of exclusion after other causes of thrombocytosis have been excluded.