Lipopolysaccharide Stress Induces Cryptic Exon Splice Variants of the Human Glucocorticoid Receptor

BACTERIAL PATHOGEN-ASSOCIATED MOLECULAR PATTERNS UPREGULATE HUMAN GLUCOCORTICOID RECEPTOR EXPRESSION IN PERIPHERAL BLOOD MONONUCLEAR CELLS

ABSTRACT

It is well known that bacterial components (pathogen-associated molecular patterns [PAMPs]) induce a proinflammatory response through pattern recognition receptor signaling. What is not known, however, is how the inflammatory response is downregulated. We hypothesize that bacterial products initiate compensatory anti-inflammatory responses by inducing expression of the human glucocorticoid receptor (hGR). Peripheral blood mononuclear cells (PBMCs) were isolated from leukocytes concentrated from single human donors (Leukopaks). PBMCs were treated with a gram-negative bacterial component, LPS, or gram-positive bacterial components, lipoteichoic acid (LTA) or peptidoglycan (PGN), for 1, 3, or 13 h. Protein expression of hGR was evaluated by Western blot analysis. RNA was extracted from similarly treated cells for reverse transcription-polymerase chain reaction analysis of hGR and cytokine expression. At 13 h after LPS treatment, there was an increase in the reference hGR protein (hGRα) expressed within some but not all PBMCs isolated from Leukopaks. There was also a dose-dependent increase in hGRα expression with increasing concentrations of PGN (10 and 50 μg/mL). LTA, however, did not affect hGRα expression. PGN also increased the mRNA expression of an hGR splice variant, hGR-B(54). The mRNA expression changes for the inflammatory cytokines were Leukopak specific. We found that cell wall components of both gram-positive and gram-negative bacteria can increase the expression of hGRα. Although these PAMPs augment the inflammatory response, it seems that there is a simultaneous upregulation of hGRα expression. Because binding of cortisol to hGRα typically induces anti-inflammatory proteins, the same PAMPs that induce an inflammatory response seem to also initiate a negative feedback system by inducing hGRα expression in PBMCs.

Plasma Exosomes Transfer miR-885-3p Targeting the AKT/NFκB Signaling Pathway to Improve the Sensitivity of Intravenous Glucocorticoid Therapy Against Graves Ophthalmopathy

Graves ophthalmopathy (GO), a manifestation of Graves' disease, is an organ-specific autoimmune disease. Intravenous glucocorticoid therapy (ivGCs) is the first-line treatment for moderate-to-severe and active GO. However, ivGCs is only effective in 70%-80% of GO patients. Insensitive patients who choose 12-week ivGCs not only were delayed in treatment but also took the risk of adverse reactions of glucocorticoids. At present, there is still a lack of effective indicators to predict the therapeutic effect of ivGCs. Therefore, the purpose of this study is to find biomarkers that can determine the sensitivity of ivGCs before the formulation of treatment, and to clarify the mechanism of its regulation of ivGCs sensitivity. This study first characterized the miRNA profiles of plasma exosomes by miRNA sequencing to identify miRNAs differentially expressed between GO patients with significant improvement (SI) and non-significant improvement (NSI) after ivGCs treatment. Subsequently, we analyzed the function of the predicted target genes of differential miRNAs. According to the function of the target genes, we screened 10 differentially expressed miRNAs. An expanded cohort verification showed that compared with NSI patients, mir-885-3p was upregulated and mir-4474-3p and mir-615-3p were downregulated in the exosomes of SI patients. Based on statistical difference and miRNA function, mir-885-3p was selected for follow-up study. The in vitro functional analysis of exosomes mir-885-3p showed that exosomes from SI patients (SI-exo) could transfer mir-885-3p to orbital fibroblasts (OFs), upregulate the GRE luciferase reporter gene plasmid activity and the level of glucocorticoid receptor (GR), downregulate the level of inflammatory factors, and improve the glucocorticoid sensitivity of OFs. Moreover, these effects can be inhibited by the corresponding miR inhibitor. In addition, we found that high levels of mir-885-3p could inhibit the AKT/NFκB signaling pathway, upregulate the GRE plasmid activity and GR level, and downregulate the level of inflammatory factors of OFs. Moreover, the improvement of glucocorticoid sensitivity by mir-885-3p transmitted by SI-exo can also be inhibited by the AKT/NFκB agonist. Finally, through the in vivo experiment of the GO mouse model, we further determined the relationship between exosomes' mir-885-3p sequence, AKT/NFκB signaling pathway, and glucocorticoid sensitivity. As a conclusion, plasma exosomes deliver mir-885-3p and inhibit the AKT/NFκB signaling pathway to improve the glucocorticoid sensitivity of OFs. Exosome mir-885-3p can be used as a biomarker to determine the sensitivity of ivGCs in GO patients.

Generalized and tissue specific glucocorticoid resistance

Glucocorticoids (GCs) are steroid hormones that influence several physiologic functions and are among the most frequently prescribed drugs worldwide. Resistance to GCs has been observed in the context of the familial generalized GC resistance (Chrousos' syndrome) or tissue specific GC resistance in chronic inflammatory states. In this review, we have summarized the major factors that influence individual glucocorticoid sensitivity/resistance. The fine-tuning of GC action is determined in a tissue-specific fashion that includes the combination of different GC receptor promoters, translation initiation sites, splice isoforms, interacting proteins, post-translational modifications, and alternative mechanisms of signal transduction.

A Novel Human Glucocorticoid Receptor Variant, G459V, is Hyperactive in Response to Steroids

ABSTRACT

A potential cause of the variable response to injury and sepsis is the variability of a patient's human glucocorticoid receptor (hGR) profile. To identify hGR variants, blood samples were collected on admission and biweekly thereafter from hospitalized patients who sustained at least a 20% total body surface area burn injury. A hyperactive G1376T single-nucleotide polymorphism (SNP) isoform was identified. This SNP led to a single amino acid change of glutamine to valine at site 459, "G459V," in the DNA-binding domain. The isoform's activity was tested in a reporter assay after treatment with steroids, the hGR antagonist RU486 (mifepristone) alone, or RU486 followed by steroids. When treated with hydrocortisone, the hGR G459V isoform had a hyperactive response; its activity was over 30 times greater than the reference hGRα. Unexpectedly, G459V had significantly increased activity when treated with the hGR antagonist RU486. With the combination of both RU486 and hydrocortisone, G459V activity was repressed, but greater than that of RU486 alone. Finally, when hGRα was cotransfected with G459V to simulate isoform interaction, the activity was closer to that of the hGRα profile than the G459V isoform. The unique activity of the G459V isoform shows that some variants of hGR have the potential to alter a person's response to stress and steroid treatment and may be a factor as to why mitigating the clinical response to sepsis and other stressors has been so elusive.