Screening the binding affinity of bile acid derivatives for the glucocorticoid receptor ligand-binding domain

The necessity of anti-inflammatory drugs such as glucocorticoids has been evident during the COVID-19 pandemic. Glucocorticoids, are the standard therapy for the treatment of moderate and severe COVID-19 patients. However, serious side effects limit the use of these drugs, and anti-inflammatory drugs with better pharmacological properties are urgently required. Bile acids are of interest, because of their anti-inflammatory and immunomodulatory properties, facilitated through an unclear mechanism involving trans membrane and nuclear receptors. In this work, we screened the binding activity of a number of bile acid derivatives, for the ligand-binding domain of glucocorticoid receptor (GR-LBD), the most important receptor for anti-inflammatory processes. Tested compounds include oximes, lactones, lactams, tetrazoles, dienones, C-24 alcohols and cholic acid amides. Cholic acid oxime, deoxycholic acid dienone, 3-keto-24-cholic alcohol and cholic acid amide showed best binding affinities for GR-LBD among tested compounds. The in silico molecular docking explanation is provided. SAR analysis showed that expansion of B and C steroid rings or attachment of heterocycle to C ring is not beneficial for binding;side chain should contain hydrogen donor group;the GR-LBD tolerate well different functionalities on C-3 position. These results provide valuable information toward synthesis of the new glucocorticoids based on bile acids.

Aberrant Cholesterol Metabolic Genes Regulation in a Negative Feedback Loop Induced by an Alphacoronavirus.

Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that causes acute inflammation and severe diarrhea in newborn piglets with a high mortality rate. Given that cholesterol is required for coronavirus infection in vitro, the role of endogenous cholesterol metabolism in regulating coronavirus infection and the mechanism behind it ought to be elucidated. In this study, we found that the levels of cholesterol and bile acids were both elevated in the livers of PEDV-infected piglets compared to those of the control group. Consistently, in the livers of PEDV-infected piglets, the expression of key genes involved in cholesterol metabolism was significantly increased. Transcriptomic analysis indicated that the cholesterol homeostasis pathway was among the most enriched pathways in the livers of PEDV-infected piglets. Unexpectedly, the expression of key genes in the cholesterol metabolic pathway was downregulated at the messenger RNA (mRNA) level, but upregulated at the protein level. While the primary transcriptional factors (TFs) of cholesterol metabolism, including SREBP2 and FXR, were upregulated at both mRNA and protein levels in response to PEDV infection. Further Chromatin Immunoprecipitation Quantitative Real-time PCR (ChIP-qPCR) analysis demonstrated that the binding of these TFs to the locus of key genes in the cholesterol metabolic pathway was remarkably inhibited by PEDV infection. It was also observed that the occupancies of histone H3K27ac and H3K4me1, at the locus of the cholesterol metabolic genes HMGCR and HMGCS1, in the livers of PEDV-infected piglets, were suppressed. Together, the PEDV triggers an aberrant regulation of cholesterol metabolic genes via epigenetic inhibition of SREBP2/FXR-mediated transcription, which provides a novel antiviral target against PEDV and other coronaviruses.