Understanding COVID-19 susceptibility and presentation based on its underlying physiology

The SARS-CoV-2 spike S1 protein induces global proteomic changes in ATII-like rat L2 cells that are attenuated by hyaluronan

The COVID-19 pandemic continues to impose a major impact on global health and economy since its identification in early 2020, causing significant morbidity and mortality worldwide. Caused by the SARS-CoV-2 virus, along with a growing number of variants, COVID-19 has led to 651,918,402 confirmed cases and 6,656,601 deaths worldwide (as of December 27, 2022; https://covid19.who.int/). Despite advances in our understanding of COVID-19 pathogenesis, the precise mechanism by which SARS-CoV2 causes epithelial injury is incompletely understood. In this current study, robust application of global-discovery proteomics identified highly significant induced changes by the Spike S1 protein of SARS-CoV-2 in the proteome of alveolar type II (ATII)-like rat L2 cells that lack ACE2 receptors. Systems biology analysis revealed that the S1-induced proteomics changes were associated with three significant network hubs: E2F1, CREB1/RelA, and ROCK2/RhoA. We also found that pretreatment of L2 cells with high molecular weight hyaluronan (HMW-HA) greatly attenuated the S1 effects on the proteome. Western blotting analysis and cell cycle measurements confirmed the S1 upregulation of E2F1 and ROCK2/RhoA in L2 cells and the protective effects of HMW-HA. Taken as a whole, our studies revealed profound and novel biological changes that contribute to our current understanding of both S1 and hyaluronan biology. These data show that the S1 protein may contribute to epithelial injury induced by SARS-CoV-2. In addition, our work supports the potential benefit of HMW-HA in ameliorating SARS CoV-2-induced cell injury.

The oxygen dissociation curve of blood in COVID-19-An update

An impressive effect of the infection with SARS-Co-19 is the impairment of oxygen uptake due to lung injury. The reduced oxygen diffusion may potentially be counteracted by an increase in oxygen affinity of hemoglobin. However, hypoxia and anemia associated with COVID-19 usually decrease oxygen affinity due to a rise in [2,3-bisphosphoglycerate]. As such, COVID-19 related changes in the oxygen dissociation curve may be critical for oxygen uptake and supply, but are hard to predict. A Pubmed search lists 14 publications on oxygen affinity in COVID-19. While some investigations show no changes, three large studies found an increased affinity that was related to a good prognosis. Exact causes remain unknown. The cause of the associated anemia in COVID-19 is under discussion. Erythrocytes with structural alterations of membrane and cytoskeleton have been observed, and virus binding to Band 3 and also to ACE2 receptors in erythroblasts has been proposed. COVID-19 presentation is moderate in many subjects suffering from sickle cell disease. A possible explanation is that COVID-19 counteracts the unfavorable large right shift of the oxygen dissociation curve in these patients. Under discussion for therapy are mainly affinity-increasing drugs.

Increased circulating microparticles contribute to severe infection and adverse outcomes of COVID-19 in patients with diabetes

Patients with diabetes infected with COVID-19 have greater mortality than those without comorbidities, but the underlying mechanisms remain unknown. This study aims to identify the mechanistic interactions between diabetes and severe COVID-19. Microparticles (MPs), the cell membrane-derived vesicles released on cell activation, are largely increased in patients with diabetes. To date, many mechanisms have been postulated for increased severity of COVID-19 in patients with underlying conditions, but the contributions of excessive MPs in patients with diabetes have been overlooked. This study characterizes plasma MPs from normal human subjects and patients with type 2 diabetes in terms of amount, cell origins, surface adhesive properties, ACE2 expression, spike protein binding capacity, and their roles in SARS-CoV-2 infection. Results showed that over 90% of plasma MPs express ACE2 that binds the spike protein of SARS-CoV-2. MPs in patients with diabetes increase 13-fold in quantity and 11-fold in adhesiveness when compared with normal subjects. Perfusion of human plasma with pseudo-typed SARS-CoV-2 virus or spike protein-bound MPs into human endothelial cell-formed microvessels-on-a chip demonstrated that MPs from patients with diabetes, not normal subjects, interact with endothelium and carry SARS-CoV-2 into cells through endocytosis, providing additional virus entry pathways and enhanced infection. Results also showed a large percentage of platelet-derived tissue factor-bearing MPs in diabetic plasma, which could contribute to thrombotic complications with SARS-CoV-2 infection. This study reveals a dual role of diabetic MPs in promoting SARS-CoV-2 entry and propagating vascular inflammation. These findings provide novel mechanistic insight into the high prevalence of COVID-19 in patients with diabetes and their propensity to develop severe vascular complications.NEW & NOTEWORTHY This study provides the first evidence that over 90% of human plasma microparticles express ACE2 that binds SARS-CoV-2 S protein with high affinity. Thus, the highly elevated adhesive circulating microparticles identified in patients with diabetes not only have greater SARS-CoV-2 binding capacity but also enable additional viral entry through virus-bound microparticle-endothelium interactions and enhanced infection. These findings reveal a novel mechanistic insight into the adverse outcomes of COVID-19 in patients with diabetes.

ARDS in the Time of Corona: Context and Perspective

For more than 2 years, COVID-19 has been holding the world at awe with new waves of infections, novel mutants, and still limited (albeit improved) means to combat SARS-CoV-2-induced respiratory failure, the most common and fatal presentation of severe COVID-19. In the present perspective, we draw from the successes and—mostly—failures in previous acute respiratory distress syndrome (ARDS) work and the experiences from COVID-19 to define conceptual barriers that have so far hindered therapeutic breakthroughs in this deadly disease, and to open up new avenues of thinking and thus, ultimately of therapy.