Reactive oxygen species in endothelial signaling in COVID-19: Protective role of the novel peptide PIP-2.

INTRODUCTION: Recent research suggests that endothelial activation plays a role in coronavirus disease 2019 (COVID-19) pathogenesis by promoting a pro-inflammatory state. However, the mechanism by which the endothelium is activated in COVID-19 remains unclear. OBJECTIVE: To investigate the mechanism by which COVID-19 activates the pulmonary endothelium and drives pro-inflammatory phenotypes. HYPOTHESIS: The "inflammatory load or burden" (cytokine storm) of the systemic circulation activates endothelial NADPH oxidase 2 (NOX2) which leads to the production of reactive oxygen species (ROS) by the pulmonary endothelium. Endothelial ROS subsequently activates pro-inflammatory pathways. METHODS: The inflammatory burden of COVID-19 on the endothelial network, was recreated in vitro, by exposing human pulmonary microvascular endothelial cells (HPMVEC) to media supplemented with serum from COVID-19 affected individuals (sera were acquired from patients with COVID-19 infection that eventually died. Sera was isolated from blood collected at admission to the Intensive Care Unit of the Hospital of the University of Pennsylvania). Endothelial activation, inflammation and cell death were assessed in HPMVEC treated with serum either from patients with COVID-19 or from healthy individuals. Activation was monitored by measuring NOX2 activation (Rac1 translocation) and ROS production; inflammation (or appearance of a pro-inflammatory phenotype) was monitored by measuring the induction of moieties such as intercellular adhesion molecule (ICAM-1), P-selectin and the NLRP3 inflammasome; cell death was measured via SYTOX™ Green assays. RESULTS: Endothelial activation (i.e., NOX2 activation and subsequent ROS production) and cell death were significantly higher in the COVID-19 model than in healthy samples. When HPMVEC were pre-treated with the novel peptide PIP-2, which blocks NOX2 activation (via inhibition of Ca2+-independent phospholipase A2, aiPLA2), significant abrogation of ROS was observed. Endothelial inflammation and cell death were also significantly blunted. CONCLUSIONS: The endothelium is activated during COVID-19 via cytokine storm-driven NOX2-ROS activation, which causes a pro-inflammatory phenotype. The concept of endothelial NOX2-ROS production as a unifying pathophysiological axis in COVID-19 raises the possibility of using PIP-2 to maintain vascular health.

Microbiota-derived inosine programs protective CD8+ T cell responses against influenza in newborns.

The immunological defects causing susceptibility to severe viral respiratory infections due to early-life dysbiosis remain ill-defined. Here, we show that influenza virus susceptibility in dysbiotic infant mice is caused by CD8+ T cell hyporesponsiveness and diminished persistence as tissue-resident memory cells. We describe a previously unknown role for nuclear factor interleukin 3 (NFIL3) in repression of memory differentiation of CD8+ T cells in dysbiotic mice involving epigenetic regulation of T cell factor 1 (TCF 1) expression. Pulmonary CD8+ T cells from dysbiotic human infants share these transcriptional signatures and functional phenotypes. Mechanistically, intestinal inosine was reduced in dysbiotic human infants and newborn mice, and inosine replacement reversed epigenetic dysregulation of Tcf7 and increased memory differentiation and responsiveness of pulmonary CD8+ T cells. Our data unveils new developmental layers controlling immune cell activation and identifies microbial metabolites that may be used therapeutically in the future to protect at-risk newborns.

Circadian regulation of lung repair and regeneration.

Optimal lung repair and regeneration are essential for recovery from viral infections, including influenza A virus (IAV). We have previously demonstrated that acute inflammation and mortality induced by IAV is under circadian control. However, it is not known whether the influence of the circadian clock persists beyond the acute outcomes. Here, we utilize the UK Biobank to demonstrate an association between poor circadian rhythms and morbidity from lower respiratory tract infections, including the need for hospitalization and mortality after discharge; this persists even after adjusting for common confounding factors. Furthermore, we use a combination of lung organoid assays, single-cell RNA sequencing, and IAV infection in different models of clock disruption to investigate the role of the circadian clock in lung repair and regeneration. We show that lung organoids have a functional circadian clock and the disruption of this clock impairs regenerative capacity. Finally, we find that the circadian clock acts through distinct pathways in mediating lung regeneration - in tracheal cells via the Wnt/ß-catenin pathway and through IL-1ß in alveolar epithelial cells. We speculate that adding a circadian dimension to the critical process of lung repair and regeneration will lead to novel therapies and improve outcomes.

Pulmonary vascular inflammation with fatal coronavirus disease 2019 (COVID-19): possible role for the NLRP3 inflammasome.

BACKGROUND: Pulmonary hyperinflammation is a key event with SARS-CoV-2 infection. Acute respiratory distress syndrome (ARDS) that often accompanies COVID-19 appears to have worse outcomes than ARDS from other causes. To date, numerous lung histological studies in cases of COVID-19 have shown extensive inflammation and injury, but the extent to which these are a COVID-19 specific, or are an ARDS and/or mechanical ventilation (MV) related phenomenon is not clear. Furthermore, while lung hyperinflammation with ARDS (COVID-19 or from other causes) has been well studied, there is scarce documentation of vascular inflammation in COVID-19 lungs. METHODS: Lung sections from 8 COVID-19 affected and 11 non-COVID-19 subjects, of which 8 were acute respiratory disease syndrome (ARDS) affected (non-COVID-19 ARDS) and 3 were from subjects with non-respiratory diseases (non-COVID-19 non-ARDS) were H&E stained to ascertain histopathological features. Inflammation along the vessel wall was also monitored by expression of NLRP3 and caspase 1. RESULTS: In lungs from COVID-19 affected subjects, vascular changes in the form of microthrombi in small vessels, arterial thrombosis, and organization were extensive as compared to lungs from non-COVID-19 (i.e., non-COVID-19 ARDS and non-COVID-19 non-ARDS) affected subjects. The expression of NLRP3 pathway components was higher in lungs from COVID-19 ARDS subjects as compared to non-COVID-19 non-ARDS cases. No differences were observed between COVID-19 ARDS and non-COVID-19 ARDS lungs. CONCLUSION: Vascular changes as well as NLRP3 inflammasome pathway activation were not different between COVID-19 and non-COVID-19 ARDS suggesting that these responses are not a COVID-19 specific phenomenon and are possibly more related to respiratory distress and associated strategies (such as MV) for treatment.

Vascular Inflammation in Lungs of Patients with Fatal Coronavirus Disease 2019 (COVID-19): Possible Role for the NLRP3 Inflammasome.

Background: Hyperinflammation is a key event that occurs with SARS-CoV-2 infection. In the lung, hyperinflammation leads to structural damage to tissue. To date, numerous lung histological studies have shown extensive alveolar damage, but there is scarce documentation of vascular inflammation in postmortem lung tissue. Methods: Lung sections from 8 COVID-19 affected and 11 non-COVID-19 subjects [of which 8 were acute respiratory disease syndrome (ARDS) affected and 3 were from subjects with non-respiratory diseases] were stained for H & E to ascertain histopathological features including presence of thrombi/microthrombi. Inflammation along the vessel wall was also monitored by quantification of the expression of moieties of the NLRP3 inflammasome pathway (NLRP3 and caspase-1). Results: In lungs from "fatal COVID-19", vascular changes in the form of microthrombi in small vessels, arterial thrombosis, and organization were extensive as compared to lungs from "non-COVID-19 non respiratory disease" affected subjects. The NLRP3 pathway components were significantly higher in lungs from COVID-19 subjects as compared to non-COVID-19 fatal cases without respiratory disease. No significant differences were observed between COVID-19 lungs and non-COVID-19 ARDS lungs. Conclusion: We posit that inflammasome formation along the vessel wall is a characteristic of lung inflammation that accompanies COVID-19. Thus, the NLRP3 inflammasome pathway seems to be probable candidate that drives amplification of inflammation post SARS-CoV-2 infection.

Vascular Inflammation in Lungs of Patients with Fatal Coronavirus Disease 2019 (COVID-19) Infection: Possible role for the NLRP3 inflammasome.

Hyperinflammation is a key event that occurs with SARS-CoV-2 infection. In the lung, hyperinflammation leads to structural damage to tissue. To date, numerous lung histological studies have shown extensive alveolar damage, but there is scarce documentation of vascular inflammation in postmortem lung tissue. Here we document histopathological features and monitor the NLRP3 inflammasome in fatal cases of disease caused by SARS Cov2 (COVID-19). We posit that inflammasome formation along the vessel wall is a characteristic of lung inflammation that accompanies COVID-19 and that it is a probable candidate that drives amplification of inflammation post infection.

Inflammation in Periodontal Disease: Possible Link to Vascular Disease.

Inflammation is a well-organized protective response to pathogens and consists of immune cell recruitment into areas of infection. Inflammation either clears pathogens and gets resolved leading to tissue healing or remains predominantly unresolved triggering pathological processes in organs. Periodontal disease (PD) that is initiated by specific bacteria also triggers production of inflammatory mediators. These processes lead to loss of tissue structure and function. Reactive oxygen species and oxidative stress play a role in susceptibility to periodontal pathogenic bacterial infections. Periodontal inflammation is a risk factor for systemic inflammation and eventually cardiovascular disease (CVD). This review discusses the role of inflammation in PD and its two way association with other health conditions such as diabetes and CVD. Some of the mechanisms underpinning the links between inflammation, diabetes, CVD and PD are also discussed. Finally, we review available epidemiological data and other reports to assess possible links between oral health and CVD.

Transposon Mutagenesis of Listeria monocytogenes.

Listeria monocytogenes is a Gram-positive, facultative intracellular foodborne pathogen that enters the human digestive tract after the consumption of contaminated food. Much research has been done to understand the virulence factors of Listeria monocytogenes. One useful tool to study these virulence factors has been transposon mutagenesis. Many mutants can be generated at a time by performing high-throughput mutagenesis using transposons and later screening these mutants to identify features related to particular functions in the bacteria. Many transposon delivery systems are not ideal for transposon studies in Listeria monocytogenes, as the transposon system is too large, has lower transposition efficiency, and a high rate of plasmid retention. Therefore, a new mariner-based transposition system has been developed for Listeria monocytogenes. This system is an ideal high-throughput transposon mutagenesis as the rate of transposition is high and random, along with very low plasmid retention capacity.

Clostridium scindens ATCC 35704: Integration of Nutritional Requirements, the Complete Genome Sequence, and Global Transcriptional Responses to Bile Acids.

In the human gut, Clostridium scindens ATCC 35704 is a predominant bacterium and one of the major bile acid 7α-dehydroxylating anaerobes. While this organism is well-studied relative to bile acid metabolism, little is known about the basic nutrition and physiology of C. scindens ATCC 35704. To determine the amino acid and vitamin requirements of C. scindens, the leave-one-out (one amino acid group or vitamin) technique was used to eliminate the nonessential amino acids and vitamins. With this approach, the amino acid tryptophan and three vitamins (riboflavin, pantothenate, and pyridoxal) were found to be required for the growth of C. scindens In the newly developed defined medium, C. scindens fermented glucose mainly to ethanol, acetate, formate, and H2. The genome of C. scindens ATCC 35704 was completed through PacBio sequencing. Pathway analysis of the genome sequence coupled with transcriptome sequencing (RNA-Seq) under defined culture conditions revealed consistency with the growth requirements and end products of glucose metabolism. Induction with bile acids revealed complex and differential responses to cholic acid and deoxycholic acid, including the expression of potentially novel bile acid-inducible genes involved in cholic acid metabolism. Responses to toxic deoxycholic acid included expression of genes predicted to be involved in DNA repair, oxidative stress, cell wall maintenance/metabolism, chaperone synthesis, and downregulation of one-third of the genome. These analyses provide valuable insight into the overall biology of C. scindens which may be important in treatment of disease associated with increased colonic secondary bile acids.IMPORTANCEC. scindens is one of a few identified gut bacterial species capable of converting host cholic acid into disease-associated secondary bile acids such as deoxycholic acid. The current work represents an important advance in understanding the nutritional requirements and response to bile acids of the medically important human gut bacterium, C. scindens ATCC 35704. A defined medium has been developed which will further the understanding of bile acid metabolism in the context of growth substrates, cofactors, and other metabolites in the vertebrate gut. Analysis of the complete genome supports the nutritional requirements reported here. Genome-wide transcriptomic analysis of gene expression in the presence of cholic acid and deoxycholic acid provides a unique insight into the complex response of C. scindens ATCC 35704 to primary and secondary bile acids. Also revealed are genes with the potential to function in bile acid transport and metabolism.

Oxygen deprivation influences the survival of Listeria monocytogenes in gerbils.

Listeria monocytogenes is a facultative anaerobic foodborne pathogen capable of surviving harsh environments. Recent work has indicated that anaerobic conditions increase the resistance capability of certain strains to environmental stressors. The goal of the study was to conduct a preliminary study to determine whether exposure to anaerobic conditions prior to infection increases the ability to survive in vivo. Gerbils were inoculated with one of five doses of the L. monocytogenes strain F2365 by oral gavage: phosphate-buffered saline (control), 5 × 106 colony forming units aerobic culture (low aerobic), 5 × 108 aerobic culture (high aerobic), 5 × 106 anaerobic culture (low anaerobic), or 5 × 108 anaerobic culture (high anaerobic) dose of F2365. Gerbils inoculated with a high aerobic or anaerobic dose exhibited significant weight loss. Gerbils administered either the low or high anaerobic dose had at least 3 log10 of L. monocytogenes present in fecal samples, which contrasted with gerbils that received the low aerobic dose. Animals that received the high anaerobic dose had a significant increase in bacterial loads within the liver. Histologic examination of the L. monocytogenes positive livers exhibited locally extensive areas of hepatocellular necrosis, though the extent of this damage differed between treatment groups. Microbial community analysis of the cecum from gerbils infected with L. monocytogenes indicated that the abundance of Bacteroidales and Clostridiales increased and there was a decrease in the abundance of Spirochaetales. This study suggests that anaerobic conditions alter the localization pattern of L. monocytogenes within the gastrointestinal tract. These findings could relate to how different populations are more susceptible to listeriosis, as oxygen availability may differ within the gastrointestinal tract.

The Effect of Oxygen on Bile Resistance in Listeria monocytogenes.

Listeria monocytogenes is a Gram-positive facultative anaerobe that is the causative agent of the disease listeriosis. The infectious ability of this bacterium is dependent upon resistance to stressors encountered within the gastrointestinal tract, including bile. Previous studies have indicated bile salt hydrolase activity increases under anaerobic conditions, suggesting anaerobic conditions influence stress responses. Therefore, the goal of this study was to determine if reduced oxygen availability increased bile resistance of L. monocytogenes. Four strains representing three serovars were evaluated for changes in viability and proteome expression following exposure to bile in aerobic or anaerobic conditions. Viability for F2365 (serovar 4b), EGD-e (serovar 1/2a), and 10403S (serovar 1/2a) increased following exposure to 10% porcine bile under anaerobic conditions (P < 0.05). However, HCC23 (serovar 4a) exhibited no difference (P > 0.05) in bile resistance between aerobic and anaerobic conditions, indicating that oxygen availability does not influence resistance in this strain. The proteomic analysis indicated F2365 and EGD-e had an increased expression of proteins associated with cell envelope and membrane bioenergetics under anaerobic conditions, including thioredoxin-disulfide reductase and cell division proteins. Interestingly, HCC23 had an increase in several dehydrogenases following exposure to bile under aerobic conditions, suggesting that the NADH:NAD+ is altered and may impact bile resistance. Variations were observed in the expression of the cell shape proteins between strains, which corresponded to morphological differences observed by scanning electron microscopy. These data indicate that oxygen availability influences bile resistance. Further research is needed to decipher how these changes in metabolism impact pathogenicity in vivo and also the impact that this has on susceptibility of a host to listeriosis.