Long-Term Effects of COVID-19 on the Cardiopulmonary System in Adults and Children: Current Status and Questions to be Resolved by the National Institutes of Health Researching COVID to Enhance Recovery Initiative

TOPIC IMPORTANCE

Long COVID may occur in at least 10% of patients recovering from SARS-CoV-2 infection and often is associated with debilitating symptoms. Among the organ systems that might be involved in its pathogenesis, the respiratory and cardiovascular systems may be central to common symptoms seen in survivors of COVID-19, including fatigue, dyspnea, chest pain, cough, and exercise intolerance. Understand the exact symptomatology, causes, and effects of long COVID on the heart and lungs may help us to discover new therapies. To that end, the National Institutes of Health is sponsoring a national study population of diverse volunteers to support large-scale studies on the long-term effects of COVID-19.

REVIEW FINDINGS

The National Institutes of Health Researching COVID to Enhance Recovery (RECOVER) initiative currently is recruiting participants in the United States to answer critical questions about long COVID. The study comprises adult and pediatric cohorts as well as an electronic health record cohort. Based on symptoms, individuals undergo prespecified medical testing to understand whether abnormalities can be detected and are followed up longitudinally. Herein, we outline current understanding of the clinical symptoms and pathophysiologic features of long COVID with respect to the cardiopulmonary system in adults and children and then determine how the clinical, electronic health record, and autopsy cohorts of the RECOVER initiative will attempt to answer the most pressing questions surrounding the long-term effects of COVID-19.

SUMMARY

Data generated from the RECOVER initiative will provide guidance about missing gaps in our knowledge about long COVID and how they might be filled by data gathered through the RECOVER initiative.

Volcanically extruded phosphides as an abiotic source of Venusian phosphine

We hypothesize that trace amounts of phosphides formed in the mantle are a plausible abiotic source of the Venusian phosphine observed by Greaves et al. [Nat. Astron., https://doi.org/10.1038/s41550-020-1174-4 (2020)]. In this hypothesis, small amounts of phosphides (P3- bound in metals such as iron), sourced from a deep mantle, are brought to the surface by volcanism. They are then ejected into the atmosphere in the form of volcanic dust by explosive volcanic eruptions, which were invoked by others to explain the episodic changes of sulfur dioxide seen in the atmosphere [Esposito, Science 223, 1072-1074 (1984)]. There they react with sulfuric acid in the aerosol layer to form phosphine (2 P3- + 3H2SO4 = 2PH3 + 3SO42-). We take issue with the conclusion of Bains et al. [arXiv:2009.06499 (2020)] that the volcanic rates for such a mechanism would have to be implausibly high. We consider a mantle with the redox state similar to the Earth, magma originating deep in the mantle-a likely scenario for the origin of plume volcanism on Venus-and episodically high but plausible rates of volcanism on a Venus bereft of plate tectonics. We conclude that volcanism could supply an adequate amount of phosphide to produce phosphine. Our conclusion is supported by remote sensing observations of the Venusian atmosphere and surface that have been interpreted as indicative of currently active volcanism.

Pancreatic cancer cell-derived vascular endothelial growth factor is biologically active in vitro and enhances tumorigenicity in vivo

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulator that acts by binding to high-affinity transmembrane receptors. Although both VEGF and its receptors are overexpressed in human pancreatic ductal adenocarcinoma (PDAC), this malignancy is not generally considered to be highly vascular. It is not known, therefore, whether the abundance of VEGF in PDAC is biologically relevant. To address this issue, we measured the angiogenic effects of pancreatic cancer cell-derived VEGF in an in vitro endothelial cell proliferation assay and characterized the consequences of suppressing VEGF expression on pancreatic tumor growth in an athymic nude mouse model. We found that human pancreatic cancer cell lines secrete large quantities of biologically active VEGF into conditioned medium (CM). Stable transfection of an anti-sense VEGF(189) (AS-VEGF(189)) expression construct into PANC-1 pancreatic cancer cells resulted in decreased VEGF expression and secretion, a decreased capacity of the resultant CM to enhance endothelial cell proliferation and a significant attenuation of tumor cell proliferation in vitro. Furthermore, when injected into athymic nude mice, AS-VEGF(189)-expressing cells exhibited an 80% decrease in tumor growth compared with control cells. These results support the hypothesis that VEGF promotes pancreatic cancer growth in vivo and suggest that anti-VEGF therapy may be useful in the treatment of this disease.

Nitric oxide production by coelomocytes of Asterias forbesi

Vertebrate mononuclear phagocytes produce a plethora of molecules involved in host defense. Among the most potent are the reactive oxygen and nitrogen intermediates. Coelomocytes from invertebrates subserve many of the same functions. In order to determine whether invertebrate phagocytes employ reactive nitrogen intermediates, we investigated the effect of various nonspecific stimulators and invertebrate interleukin (IL)-1alpha- and beta-like molecules on nitric oxide (NO) production. Elevated NO release by stimulated coelomocytes was seen after 24 h. Incubation of stimulated coelomocytes in the presence of arginine analogs inhibited NO release. When invertebrate IL-1-like molecules were added to the coelomocytes, they stimulated the release of NO. Western blot analysis using a polyclonal rabbit antiserum to murine NO synthase detected a band at approximately 125 kDa. These data indicate that coelomocytes are capable of producing and releasing NO and that NO is a chemical mediator that has been conserved as a host defense weapon of phagocytes through evolutionary time.

Characterization of an IL-1 receptor from Asterias forbesi coelomocytes

The tremendous importance of cytokines to immune defensive systems suggests that they have been conserved through evolution. The existence of interleukin (IL)-1-like molecules in several invertebrate groups substantiates this hypothesis. To characterize further the relationship of invertebrate IL-1-like molecules, we have used competitive binding assays to show that invertebrate coelomocytes of the starfish Asterias forbesi possess an IL-1-specific binding protein. Competitive binding experiments used radiolabeled human IL-1alpha. IL-1 bound specifically to the coelomocytes by a single high-affinity binding site (K(d) = 8.72 x 10(-10)/M). There are approximately 6000 binding sites per cell. The specificity of the receptor was confirmed by demonstrating that, among a group of cytokines and lymphokines tested, only vertebrate IL-1- or echinoderm IL-1-like molecules and the vertebrate IL-1 receptor antagonist inhibit IL-1 binding. Treatment of coelomocytes (labeled with IL-1alpha) with bivalent water-soluble crosslinkers identified a membrane protein of approximately 70 kDa to which IL-1 is specifically crosslinked.