Aurintricarboxylic acid increases yield of HSV-1 vectors

Dexamethasone disrupts intracellular pH homeostasis to delay coronavirus infectious bronchitis virus cell entry via sodium hydrogen exchanger 3 activation

Coronavirus entry into host cells enables the virus to initiate its replication cycle efficiently while evading host immune response. Cell entry is intricately associated with pH levels in the cytoplasm or endosomes. In this study, we observed that the sodium hydrogen exchanger 3 (Na+/H+ exchanger 3 or NHE3), which is strongly activated by dexamethasone (Dex) to promote cell membrane Na+/H+ exchange, was critical for cytoplasmic and endosomal acidification. Dex activates NHE3, which increases intracellular pH and blocks the initiation of coronavirus infectious bronchitis virus (IBV) negative-stranded genomic RNA synthesis. Also, Dex antiviral effects are relieved by the glucocorticoid receptor (GR) antagonist RU486 and the NHE3 selective inhibitor tenapanor. These results show that Dex antiviral effects depend on GR and NHE3 activities. Furthermore, Dex exhibits remarkable dose-dependent inhibition of IBV replication, although its antiviral effects are constrained by specific virus and cell types. To our knowledge, this is the first report to show that Dex helps suppress the entry of coronavirus IBV into cells by promoting proton leak pathways, as well as by precisely tuning luminal pH levels mediated by NHE3. Disrupted cytoplasmic pH homeostasis, triggered by Dex and NHE3, plays a crucial role in impeding coronavirus IBV replication. Therefore, cytoplasmic pH plays an essential role during IBV cell entry, probably assisting viruses at the fusion and/or uncoating stages. The strategic modulation of NHE3 activity to regulate intracellular pH could provide a compelling mechanism when developing potent anti-coronavirus drugs.IMPORTANCESince the outbreak of coronavirus disease 2019, dexamethasone (Dex) has been proven to be the first drug that can reduce the mortality rate of coronavirus patients to a certain extent, but its antiviral effect is limited and its underlying mechanism has not been fully clarified. Here, we comprehensively evaluated the effect of Dex on coronavirus infectious bronchitis virus (IBV) replication and found that the antiviral effect of Dex is achieved by regulating sodium hydrogen exchanger 3 (NHE3) activity through the influence of glucocorticoid receptor on cytoplasmic pH or endosome pH. Dex activates NHE3, leading to an increase in intracellular pH and blocking the initiation of negative-stranded genomic RNA synthesis of coronavirus IBV. In this study, we identified the mechanism by which glucocorticoids counteract coronaviruses in cell models, laying the foundation for the development of novel antiviral drugs.

Non-Targeted Metabolomic Analysis of Chicken Kidneys in Response to Coronavirus IBV Infection Under Stress Induced by Dexamethasone

Stress in poultry can lead to changes in body metabolism and immunity, which can increase susceptibility to infectious diseases. However, knowledge regarding chicken responses to viral infection under stress is limited. Dexamethasone (Dex) is a synthetic glucocorticoid similar to that secreted by animals under stress conditions, and has been widely used to induce stress in chickens. Herein, we established a stress model in 7-day-old chickens injected with Dex to elucidate the effects of stress on IBV replication in the kidneys. The metabolic changes, immune status and growth of the chickens under stress conditions were comprehensively evaluated. Furthermore, the metabolic profile, weight gain, viral load, serum cholesterol levels, cytokines and peripheral blood lymphocyte ratio were compared in chickens treated with Dex and infected with IBV. An LC-MS/MS-based metabolomics method was used to examine differentially enriched metabolites in the kidneys. A total of 113 metabolites whose abundance was altered after Dex treatment were identified, most of which were lipids and lipid-like molecules. The principal metabolic alterations in chicken kidneys caused by IBV infection included fatty acid, valine, leucine and isoleucine metabolism. Dex treatment before and after IBV infection mainly affected the host’s tryptophan, phenylalanine, amino sugar and nucleotide sugar metabolism. In addition, Dex led to up-regulation of serum cholesterol levels and renal viral load in chickens, and to the inhibition of weight gain, peripheral blood lymphocytes and IL-6 production. We also confirmed that the exogenous cholesterol in DF-1 cells promoted the replication of IBV. However, whether the increase in viral load in kidney tissue is associated with the up-regulation of cholesterol levels induced by Dex must be demonstrated in future experiments. In conclusion, chick growth and immune function were significantly inhibited by Dex. Host cholesterol metabolism and the response to IBV infection are regulated by Dex. This study provides valuable insights into the molecular regulatory mechanisms in poultry stress, and should support further research on the intrinsic link between cholesterol metabolism and IBV replication under stress conditions.