Characterization of a novel synthetic constitutive-active glucocorticoid receptor

Glucocorticoids (GCs), acting via the glucocorticoid receptor (GR), are the only available drugs for severe alcoholic hepatitis (AH). Additionally, GCs are important drugs for various lung diseases. However, GCs lack long-term benefits and are avoided in AH with active infection or gastrointestinal bleeding. Recently, we engineered "superGR", a constitutive-active synthetic GR fragment with modifications. The purpose of this study was to characterize this "superGR" using human hepatoma and lung epithelial cells. Results of dual-luciferase reporter assays showed that in human hepatoma HepG2 cells, "superGR" potently and ligand-independently, activated the promoter of many human genes markedly down-regulated in AH including those important for cytoprotection, lipid catabolism, and anti-inflammation. Interestingly, some of these genes are not usually activated by wildtype GR, with "superGR" even activating protective genes down-regulated by the wildtype GR. Moreover, "superGR" exhibited strong repressive effects on key proinflammatory genes induced in AH. Deletion and mutation analyses indicated that inhibitory regions in the N- and C-terminal domains contribute to the inability of wildtype GR to activate certain genes. qPCR analysis revealed that lipid nanoparticle-mediated delivery of "superGR" mRNAs to human hepatoma HepG2 cells and lung epithelial H441 cells potently upregulated these cytoprotective genes and down-regulated pro-inflammatory genes, with better efficacy than Dexamethasone treatment. Additionally, "superGR" synergized with interleukin-22 to induce cytoprotective and immunomodulatory genes in HepG2 cells. Future in vivo studies on tissue-specific delivery of "superGR" on expression of key genes for cytoprotection, lipid catabolism, and anti-inflammation in models of liver and lung diseases are warranted for further evaluation.