Prolonged NHE Activation may be both Cause and Outcome of Cytokine Release Syndrome in COVID-19

COVID-19 Causes Ferroptosis and Oxidative Stress in Human Endothelial Cells

Oxidative stress and endothelial dysfunction have been shown to play crucial roles in the pathophysiology of COVID-19 (coronavirus disease 2019). On these grounds, we sought to investigate the impact of COVID-19 on lipid peroxidation and ferroptosis in human endothelial cells. We hypothesized that oxidative stress and lipid peroxidation induced by COVID-19 in endothelial cells could be linked to the disease outcome. Thus, we collected serum from COVID-19 patients on hospital admission, and we incubated these sera with human endothelial cells, comparing the effects on the generation of reactive oxygen species (ROS) and lipid peroxidation between patients who survived and patients who did not survive. We found that the serum from non-survivors significantly increased lipid peroxidation. Moreover, serum from non-survivors markedly regulated the expression levels of the main markers of ferroptosis, including GPX4, SLC7A11, FTH1, and SAT1, a response that was rescued by silencing TNFR1 on endothelial cells. Taken together, our data indicate that serum from patients who did not survive COVID-19 triggers lipid peroxidation in human endothelial cells.

Severe acute respiratory syndrome coronavirus 2 may cause liver injury via Na+/H+ exchanger

The liver has many significant functions, such as detoxification, the urea cycle, gluconeogenesis, and protein synthesis. Systemic diseases, hypoxia, infections, drugs, and toxins can easily affect the liver, which is extremely sensitive to injury. Systemic infection of severe acute respiratory syndrome coronavirus 2 can cause liver damage. The primary regulator of intracellular pH in the liver is the Na⁺/H⁺ exchanger (NHE). Physiologically, NHE protects hepatocytes from apoptosis by making the intracellular pH alkaline. Severe acute respiratory syndrome coronavirus 2 increases local angiotensin II levels by binding to angiotensin-converting enzyme 2. In severe cases of coronavirus disease 2019, high angi-otensin II levels may cause NHE overstimulation and lipid accumulation in the liver. NHE overstimulation can lead to hepatocyte death. NHE overstimulation may trigger a cytokine storm by increasing proinflammatory cytokines in the liver. Since the release of proinflammatory cytokines such as interleukin-6 increases with NHE activation, the virus may indirectly cause an increase in fibrinogen and D-dimer levels. NHE overstimulation may cause thrombotic events and systemic damage by increasing fibrinogen levels and cytokine release. Also, NHE overstimulation causes an increase in the urea cycle while inhibiting vitamin D synthesis and gluconeogenesis in the liver. Increasing NHE3 activity leads to Na⁺ loading, which impairs the containment and fluidity of bile acid. NHE overstimulation can change the gut microbiota composition by disrupting the structure and fluidity of bile acid, thus triggering systemic damage. Unlike other tissues, tumor necrosis factor-alpha and angiotensin II decrease NHE3 activity in the intestine. Thus, increased luminal Na⁺ leads to diarrhea and cytokine release. Severe acute respiratory syndrome coronavirus 2-induced local and systemic damage can be improved by preventing virus-induced NHE overstimulation in the liver.

Schizophyllum commune Reduces Expression of the SARS-CoV-2 Receptors ACE2 and TMPRSS2

The current global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) of COVID-19 has infected hundreds of millions of people, killed millions, and continues to pose a threat. It has become one of the largest epidemics in human history, causing enormous damage to people's lives and economies in the whole world. However, there are still many uncertainties and continued attention to the impact of SARS-CoV-2 on human health. The entry of SARS-CoV-2 into host cells is facilitated by the binding of the spike protein on the virus surface to the cell surface receptor angiotensin-converting enzyme 2 (ACE2). Furthermore, transmembrane protease serine 2 (TMPRSS2) is a host surface protease that cleaves and proteolytically activates its S protein, which is necessary for viral infection. Thus, SARS-CoV-2 uses the ACE2 receptor for cell entry and initiates the S protein using the protease TMPRSS2. Schizophyllum commune (SC) is one of the most widely distributed fungi, often found on the rotten wood of trees that has been found to have various health benefits, including anticancer, antimicrobial activity, antiparasitic, and immunomodulatory function. In this article, SC significantly diminished the expression ACE2 and TMPRSS2 protein in vitro and in vivo without cell damage. In addition, adenosine from SC was also proven in this experiment to reduce the ACE2 and TMPRSS2 expression. Thus, our findings suggest that SC and adenosine exhibit potential for the repression of SARS-CoV-2 infection via the ACE2 and TMPRSS2 axis.