We report a novel method for the transient expression of SARS-CoV-2 envelope (E) protein in intracellular organelles and the plasma membrane of mammalian cells and Xenopus oocytes.r Intracellular expression of SARS-CoV-2 E protein increases intra-Golgi pH. r By targeting the SARS-CoV-2 E protein to the plasma membrane, we show that it forms a cation channel, viroporin, that is modulated by changes of pH.r This method for studying the activity of viroporins may facilitate screening for new antiviral drugs to identify novel treatments for COVID-19.

Synchronization and bursting activity are intrinsic electrophysiological properties of in vivo and in vitro neural networks. During early development, cortical cultures exhibit a wide repertoire of synchronous bursting dynamics whose characterization may help to understand the parameters governing the transition from immature to mature networks. Here we used machine learning techniques to characterize and predict the developing spontaneous activity in mouse cortical neurons on microelectrode arrays (MEAs) during the first three weeks in vitro. Network activity at three stages of early development was defined by 18 electrophysiological features of spikes, bursts, synchrony, and connectivity. The variability of neuronal network activity during early development was investigated by applying k-means and self-organizing map (SOM) clustering analysis to features of bursts and synchrony. These electrophysiological features were predicted at the third week in vitro with high accuracy from those at earlier times using three machine learning models: Multivariate Adaptive Regression Splines, Support Vector Machines, and Random Forest. Our results indicate that initial patterns of electrical activity during the first week in vitro may already predetermine the final development of the neuronal network activity. The methodological approach used here may be applied to explore the biological mechanisms underlying the complex dynamics of spontaneous activity in developing neuronal cultures.

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We measured plasma levels of fibrinogen, plasminogen, tissue plasminogen activator (t-PA) and plasminogen activation inhibitor 1 (PAI-1) in blood from 37 patients with severe coronavirus disease-19 (COVID-19) and 23 controls. PAI-1, t-PA and fibrinogen levels were significantly higher in the COVID-19 group. Increased levels of PAI-1 likely result in lower plasmin activity and hence decreased fibrinolysis. These observations provide a partial explanation for the fibrin-mediated increase in blood viscosity and hypercoagulability that has previously been observed in COVID-19. Our data suggest that t-PA administration may be problematic, but that other interventions designed to enhance fibrinolysis might prove useful in the treatment of the coagulopathy that is often associated with severe COVID-19.

Severe coronavirus disease-19 (COVID-19) has been associated with fibrin-mediated hypercoagulability and thromboembolic complications. To evaluate potential biomarkers of coagulopathy and disease severity in COVID-19, we measured plasma levels of eight biomarkers potentially associated with coagulation, fibrinolysis, and platelet function in 43 controls and 63 COVID-19 patients, including 47 patients admitted to the intensive care unit (ICU) and 16 non-ICU patients. COVID-19 patients showed significantly elevated levels of fibrinogen, tissue plasminogen activator (t-PA), and its inhibitor plasminogen activation inhibitor 1 (PAI-1), as well as ST2 (the receptor for interleukin-33) and von Willebrand factor (vWF) compared to the control group. We found that higher levels of t-PA, ST2, and vWF at the time of admission were associated with lower survival rates, and that thrombotic events were more frequent in patients with initial higher levels of vWF. These results support a predictive role of specific biomarkers such as t-PA and vWF in the pathophysiology of COVID-19. The data provide support for the case that hypercoagulability in COVID-19 is fibrin-mediated, but also highlights the important role that vWF may play in the genesis of thromboses in the pathophysiology of COVID-19. Interventions designed to enhance fibrinolysis might prove to be useful adjuncts in the treatment of coagulopathy in a subset of COVID-19 patients. Supplementary Information The online version contains supplementary material available at 10.1007/s12185-022-03437-2.

Coronavirus disease-2019 (COVID-19) is associated with hypercoagulability that may cause thromobembolic complications. We describe our recent studies investigating the mechanisms of hypercoagulability in patients with severe COVID-19 requiring mechanical ventilation during the COVID-19 crisis in New York City in spring 2020. Using rotational thombelastometry we found that almost all patients with severe COVID-19 had signs of hypercoagulability compared with non-COVID-19 controls. Specifically, the maximal clot firmness in the fibrin-based extrinsically activated test was almost twice the upper limit of normal in COVID patients, indicating a fibrin-mediated cause for hypercoagulability. To better understand the mechanism of this hypercoagulability we measured the components of the fibrinolytic pathways. Fibrinogen, tissue plasminogen activator and plasminogen activator inhibitor-1, but not plasminogen levels were elevated in patients with severe COVID-19. Our studies indicate that hypercoagulability in COV-ID-19 may be because of decreased fibrinolysis resulting from inhibition of plasmin through high levels of plasminogen activator inhibitor-1. Clinicians creating treatment protocols for anticoagulation in critically ill COVID-19 patients should consider these potential mechanisms of hypercoaguability.

ᮀ Synaptic function is critical for the brain to process experiences dictated by the environment requiring change over the lifetime of the organism. Experience-driven adaptation requires that receptors, signal transduction pathways, transcription and translational mechanisms within neurons respond rapidly over its lifetime. Adaptive responses communicated through the rapid firing of neurons are dependent upon the integrity and function of synapses. These rapid responses via adaptation underlie the organism's ability to perceive, learn, remember, calculate and plan. Glutamate, the endogenous neurotransmitter required for physiological excitation in the brain, is critically involved in neuronal adaptive responses and in the pathophysiology of neurodegenerative disorders. Using neuronal experimental systems, we will discuss how compounds with low dose effects mediated via glutamate receptors can result either in a neuroprotective or neurotoxic response. Because the brain has evolved to respond rapidly to environmental cues, exposure of neurons to stressful stimuli can result in a pivotal response toward either synaptic adaptation or dysfunction and neuronal cell death. Understanding how neurons adapt to stressful stimuli will provide important clues toward the development of strategies to protect the brain against neurodegeneration.

Severe coronavirus disease-19 (COVID-19) has been associated with fibrin-mediated hypercoagulability and thromboembolic complications. To evaluate potential biomarkers of coagulopathy and disease severity in COVID-19, we measured plasma levels of eight biomarkers potentially associated with coagulation, fibrinolysis, and platelet function in 43 controls and 63 COVID-19 patients, including 47 patients admitted to the intensive care unit (ICU) and 16 non-ICU patients. COVID-19 patients showed significantly elevated levels of fibrinogen, tissue plasminogen activator (t-PA), and its inhibitor plasminogen activation inhibitor 1 (PAI-1), as well as ST2 (the receptor for interleukin 33) and von Willebrand factor (vWF) compared to the control group. We found that higher levels of t-PA, ST2, and vWF at the time of admission were associated with lower survival rates, and that thrombotic events were more frequent in patients with initial higher levels of vWF. These results support a predictive role of specific biomarkers such as t-PA and vWF in the pathophysiology of COVID-19. The data provide support for the case that hypercoagulability in COVID-19 is fibrin-mediated, but also highlights the important role that vWF may play in the genesis of thromboses in the pathophysiology of COVID-19. Interventions designed to enhance fibrinolysis and reduce platelet aggregation might prove to be useful adjuncts in the treatment of coagulopathy in a subset of COVID-19 patients.