SARS-CoV-2 viroporin encoded by ORF3a triggers the NLRP3 inflammatory pathway.

Heightened inflammatory response is a prominent feature of severe COVID-19 disease. We report that the SARS-CoV-2 ORF3a viroporin activates the NLRP3 inflammasome, the most promiscuous of known inflammasomes. Ectopically expressed ORF3a triggers IL-1ß expression via NFκB, thus priming the inflammasome. ORF3a also activates the NLRP3 inflammasome but not NLRP1 or NLRC4, resulting in maturation of IL-1ß and cleavage/activation of Gasdermin. Notably, ORF3a activates the NLRP3 inflammasome via both ASC-dependent and -independent modes. This inflammasome activation requires efflux of potassium ions and oligomerization between the kinase NEK7 and NLRP3. Importantly, infection of epithelial cells with SARS-CoV-2 similarly activates the NLRP3 inflammasome. With the NLRP3 inhibitor MCC950 and select FDA-approved oral drugs able to block ORF3a-mediated inflammasome activation, as well as key ORF3a amino acid residues needed for virus release and inflammasome activation conserved in the new variants of SARS-CoV-2 isolates across continents, ORF3a and NLRP3 present prime targets for intervention.

How SARS-CoV-2 might affect potassium balance via impairing epithelial sodium channels?

Severe acute respiratory syndrome coronaviruses 2 (SARS-CoV-2) is the causative agent of current coronavirus disease 2019 (COVID-19) pandemic. Electrolyte disorders particularly potassium abnormalities have been repeatedly reported as common clinical manifestations of COVID-19. Here, we discuss how SARS-CoV-2 may affect potassium balance by impairing the activity of epithelial sodium channels (ENaC). The first hypothesis could justify the incidence of hypokalemia. SARS-CoV-2 cell entry through angiotensin-converting enzyme 2 (ACE2) may enhance the activity of renin-angiotensin-aldosterone system (RAAS) classical axis and further leading to over production of aldosterone. Aldosterone is capable of enhancing the activity of ENaC and resulting in potassium loss from epithelial cells. However, type II transmembrane serine protease (TMPRSS2) is able to inhibit the ENaC, but it is utilized in the case of SARS-CoV-2 cell entry, therefore the ENaC remains activated. The second hypothesis describe the incidence of hyperkalemia based on the key role of furin. Furin is necessary for cleaving both SARS-CoV-2 spike protein and ENaC subunits. While the furin is hijacked by the virus, the decreased activity of ENaC would be expected, which causes retention of potassium ions and hyperkalemia. Given that the occurrence of hypokalemia is higher than hyperkalemia in COVID-19 patients, the first hypothesis may have greater impact on potassium levels. Further investigations are warranted to determine the exact role of ENaC in SARS-CoV-2 pathogenesis.

Combating COVID-19 and Building Immune Resilience: A Potential Role for Magnesium Nutrition?

Background: In December 2019, the viral pandemic of respiratory illness caused by COVID-19 began sweeping its way across the globe. Several aspects of this infectious disease mimic metabolic events shown to occur during latent subclinical magnesium deficiency. Hypomagnesemia is a relatively common clinical occurrence that often goes unrecognized since magnesium levels are rarely monitored in the clinical setting. Magnesium is the second most abundant intracellular cation after potassium. It is involved in >600 enzymatic reactions in the body, including those contributing to the exaggerated immune and inflammatory responses exhibited by COVID-19 patients.Methods: A summary of experimental findings and knowledge of the biochemical role magnesium may play in the pathogenesis of COVID-19 is presented in this perspective. The National Academy of Medicine's Standards for Systematic Reviews were independently employed to identify clinical and prospective cohort studies assessing the relationship of magnesium with interleukin-6, a prominent drug target for treating COVID-19.Results: Clinical recommendations are given for prevention and treatment of COVID-19. Constant monitoring of ionized magnesium status with subsequent repletion, when appropriate, may be an effective strategy to influence disease contraction and progression. The peer-reviewed literature supports that several aspects of magnesium nutrition warrant clinical consideration. Mechanisms include its "calcium-channel blocking" effects that lead to downstream suppression of nuclear factor-Kß, interleukin-6, c-reactive protein, and other related endocrine disrupters; its role in regulating renal potassium loss; and its ability to activate and enhance the functionality of vitamin D, among others.Conclusion: As the world awaits an effective vaccine, nutrition plays an important and safe role in helping mitigate patient morbidity and mortality. Our group is working with the Academy of Nutrition and Dietetics to collect patient-level data from intensive care units across the United States to better understand nutrition care practices that lead to better outcomes.

Effective block by pirfenidone, an antifibrotic pyridone compound (5-methyl-1-phenylpyridin-2[H-1]-one), on hyperpolarization-activated cation current: An additional but distinctive target.

Pirfenidone (PFD), a pyridone compound, is well recognized as an antifibrotic agent tailored for the treatment of idiopathic pulmonary fibrosis. Recently, through its anti-inflammatory and anti-oxidant effects, PFD based clinical trial has also been launched for the treatment of coronavirus disease (COVID-19). To what extent this drug can perturb membrane ion currents remains largely unknown. Herein, the exposure to PFD was observed to depress the amplitude of hyperpolarization-activated cation current (Ih) in combination with a considerable slowing in the activation time of the current in pituitary GH3 cells. In the continued presence of ivabradine or zatebradine, subsequent application of PFD decreased Ih amplitude further. The presence of PFD resulted in a leftward shift in Ih activation curve without changes in the gating charge. The addition of this compound also led to a reduction in area of voltage-dependent hysteresis evoked by long-lasting inverted triangular (downsloping and upsloping) ramp pulse. Neither the amplitude of M-type nor erg-mediated K+ current was altered by its presence. In whole-cell potential recordings, addition of PFD reduced the firing frequency, and this effect was accompanied by the depression in the amplitude of sag voltage elicited by hyperpolarizing current stimulus. Overall, this study highlights evidence that PFD is capable of perturbing specific ionic currents, revealing a potential additional impact on functional activities of different excitable cells.