Platelets and Immunity: Going Viral

Comparative Analysis of Hematological and Biochemical Changes in Neonates among Women with and without COVID-19 Infection during Pregnancy

The aim of this study is to evaluate the test results of neonates delivered by COVID-19-positive mothers during pregnancy with those of neonates born to unvaccinated mothers who are COVID-19-free. A cohort study was conducted on 367 pregnant women who gave birth at Premiere Hospital, Timisoara, Romania, between May 2021 and February 2022. Two groups were established: Group 1, with 167 pregnant women infected with COVID-19, and Group 2, with 200 pregnant women who were not affected by COVID-19 during pregnancy. Maternal laboratory examination did not exhibit significant variations except for platelet count. In neonatal blood tests, WBC had a significantly lower median value in the group born to COVID-19-free mothers. Neonatal anemia and leukocytosis showed slightly higher prevalence in Group 1, but the differences were not statistically significant. This study suggests that maternal COVID-19 infection during pregnancy does not have significant associations with most maternal and neonatal characteristics.

Toll-Like Receptor 4-Dependent Platelet-Related Thrombosis in SARS-CoV-2 Infection

BACKGROUND

SARS-CoV-2 is associated with an increased risk of venous and arterial thrombosis, but the underlying mechanism is still unclear.

METHODS

We performed a cross-sectional analysis of platelet function in 25 SARS-CoV-2 and 10 healthy subjects by measuring Nox2 (NADPH oxidase 2)-derived oxidative stress and thromboxane B₂, and investigated if administration of monoclonal antibodies against the S protein (Spike protein) of SARS-CoV-2 affects platelet activation. Furthermore, we investigated in vitro if the S protein of SARS-CoV-2 or plasma from SARS-CoV-2 enhanced platelet activation.

RESULTS

Ex vivo studies showed enhanced platelet Nox2-derived oxidative stress and thromboxane B₂ biosynthesis and under laminar flow platelet-dependent thrombus growth in SARS-CoV-2 compared with controls; both effects were lowered by Nox2 and TLR4 (Toll-like receptor 4) inhibitors. Two hours after administration of monoclonal antibodies, a significant inhibition of platelet activation was observed in patients with SARS-CoV-2 compared with untreated ones. In vitro study showed that S protein per se did not elicit platelet activation but amplified the platelet response to subthreshold concentrations of agonists and functionally interacted with platelet TLR4. A docking simulation analysis suggested that TLR4 binds to S protein via three receptor-binding domains; furthermore, immunoprecipitation and immunofluorescence showed S protein-TLR4 colocalization in platelets from SARS-CoV-2. Plasma from patients with SARS-CoV-2 enhanced platelet activation and Nox2-related oxidative stress, an effect blunted by TNF (tumor necrosis factor) α inhibitor; this effect was recapitulated by an in vitro study documenting that TNFα alone promoted platelet activation and amplified the platelet response to S protein via p47phox (phagocyte oxidase) upregulation.

CONCLUSIONS

The study identifies 2 TLR4-dependent and independent pathways promoting platelet-dependent thrombus growth and suggests inhibition of TLR4. or p47phox as a tool to counteract thrombosis in SARS-CoV-2.

Antiplatelet Activity of Riamilovir under Conditions of Lipopolysaccharide Intoxication

We studied the effect of antiviral agent riamilovir on ADP-induced platelet aggregation in the absence and presence of LPS. Unlike acetylsalicylic acid (reference drug), riamilovir did not exhibit antiplatelet effect in vitro. However, it markedly suppressed platelet reactivity in LPS-treated blood samples and was 2.2-fold superior to acetylsalicylic acid in terms of IC50 value. In in vivo experiments, riamilovir under conditions of hypercytokinemia blocked platelet aggregation in rats by 64%.

Janus Kinase Signaling Pathway and Its Role in COVID-19 Inflammatory, Vascular, and Thrombotic Manifestations

Acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection continues to be a worldwide public health crisis. Among the several severe manifestations of this disease, thrombotic processes drive the catastrophic organ failure and mortality in these patients. In addition to a well-established cytokine storm associated with the disease, perturbations in platelets, endothelial cells, and the coagulation system are key in triggering systemic coagulopathy, involving both the macro- and microvasculatures of different organs. Of the several mechanisms that might contribute to dysregulation of these cells following SARS-CoV-2 infection, the current review focuses on the role of activated Janus kinase (JAK) signaling in augmenting thrombotic processes and organ dysfunction. The review concludes with presenting the current understanding and emerging controversies concerning the potential therapeutic applications of JAK inhibitors for ameliorating the inflammation-thrombosis phenotype in COVID-19 patients.

What Function Do Platelets Play in Inflammation and Bacterial and Viral Infections?

The article presents the function of platelets in inflammation as well as in bacterial and viral infections, which are the result of their reaction with the endovascular environment, including cells of damaged vascular endothelium and cells of the immune system. This role of platelets is conditioned by biologically active substances present in their granules and in their specific structures - EV (extracellular vesicles).

Pathogenic Basis of Thromboinflammation and Endothelial Injury in COVID-19: Current Findings and Therapeutic Implications

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic with a great impact on social and economic activities, as well as public health. In most patients, the symptoms of COVID-19 are a high-grade fever and a dry cough, and spontaneously resolve within ten days. However, in severe cases, COVID-19 leads to atypical bilateral interstitial pneumonia, acute respiratory distress syndrome, and systemic thromboembolism, resulting in multiple organ failure with high mortality and morbidity. SARS-CoV-2 has immune evasion mechanisms, including inhibition of interferon signaling and suppression of T cell and B cell responses. SARS-CoV-2 infection directly and indirectly causes dysregulated immune responses, platelet hyperactivation, and endothelial dysfunction, which interact with each other and are exacerbated by cardiovascular risk factors. In this review, we summarize current knowledge on the pathogenic basis of thromboinflammation and endothelial injury in COVID-19. We highlight the distinct contributions of dysregulated immune responses, platelet hyperactivation, and endothelial dysfunction to the pathogenesis of COVID-19. In addition, we discuss potential therapeutic strategies targeting these mechanisms.

COVID-19 in Pregnancy: Implication on Platelets and Blood Indices

OBJECTIVE

 To describe the hematological changes, the platelet indices in particular, in pregnant women with coronavirus disease 2019 (COVID-19) compared to healthy pregnant women.

METHODS

 A retrospective case-control study conducted at the Al Yarmouk Teaching Hospital, in Baghdad, Iraq, involving 100 pregnant women, 50 with positive viral DNA for COVID-19 (case group), and 50 with negative results (control group); both groups were subjected to a thorough hematological evaluation.

RESULTS

 Among the main hematological variables analyzed, the platelet indices, namely the mean platelet volume (MPV) and the platelet distribution width (PDW), showed statistically significant differences (MPV: 10.87 ± 66.92 fL for the case group versus 9.84 ± 1.2 fL for the control group; PDW: 14.82 ± 3.18 fL for the case group versus 13.3 ± 2.16 fL for the controls). The criterion value of the receiver operating characteristic (ROC) curve for PDW at a cutoff point of > 11.8 fL showed a weak diagnostic marker, while the MPV at a cutoff value of > 10.17 fL showed a good diagnostic marker.

CONCLUSION

 The MPV and PDW are significantly affected by the this viral infection, even in asymptomatic confirmed cases, and we recommend that both parameters be included in the diagnostic panel of this infection.

Nebulization with alkaline hipertonic ibuprofen induces a rapid increase in platelets circulating in COVID-19 patients but not in healthy subjects

We analyze changes in circulating platelets in COVID-19 positive patients who received conventional treatment Dexamethasone and Enoxaparin (Dexa-Enoxa) compared to patients treated with conventional therapy plus nebulization with alkaline hypertonic ibuprofenate (AHI). Results show that after 24 h of nebulization with AHI, circulating platelets shows an increase about 40% at 24 h and reach 65% at 96 h. In patients with platelets content below 200,000 by microliter the increase was 49% and 79% at 24 and 96 h respectively. In patients with platelets above 200,000 by microliter the increase was 24% and 31% at 24 and 96 h, respectively. The increase of platelets via AHI was similar in both, men and women.To evaluate whether this action of AHI was related to platelets from COVID-19 positive patients or also for healthy people, two controls were included: one of them with 10 healthy volunteers and another one with COVID-19 positive patients hospitalized and treated only with Dexa-Enoxa. Results show that, in healthy volunteers, the number of circulating platelets remains unchanged even after 7 days of treatment with AHI. In COVID-19 positive patients treated only with Dexa-Enoxa for 4 days, platelets increased only 16%.

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

Platelet hyperactivity in COVID-19: Can the tomato extract Fruitflow® be used as an antiplatelet regime?

The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the SARS-CoV-2 virus is now considered a global public health threat. The primary focus has been on reducing the viral spread and treating respiratory symptoms; as time goes on, the impact of COVID-19 on neurological and haemostatic systems becomes more evident. The clinical data suggest that platelet hyperactivity plays a role in the pathology of COVID-19 from its onset and that platelets may serve critical functions during COVID‐19 progression. Hyperactivation of blood platelets and the coagulation system are emerging as important drivers of inflammation and may be linked to the severity of the ‘cytokine storm’ induced in severe cases of COVID-19, in which disseminated intravascular coagulation, and platelet hyperactivity are associated with poor prognosis and increased risk of mortality.

We propose that targeting platelet hyperactivity in the early stages of COVID-19 infection may reduce the immunothrombotic complications of COVID-19 and subdue the systemic inflammatory response. Lowering baseline platelet activity may be of particular importance for higher-risk groups. As an alternative to antiplatelet drugs, an inappropriate intervention in public health, we propose that the dietary antiplatelet agent Fruitflow®, derived from tomatoes, may be considered a suitable therapy. Fruitflow® contains antiplatelet and anti-inflammatory compounds that target the mechanisms of platelet activation specific to COVID-19 and can be considered a safe and natural antiplatelet regime.