DT-13 attenuates inflammation by inhibiting NLRP3-inflammasome related genes in RAW264.7 macrophages.

Plant derived saponins or other glycosides are widely used for their anti-inflammatory, antioxidant, and anti-viral properties in therapeutic medicine. In this study, we focus on understanding the function of the less known steroidal saponin from the roots of Liriope muscari L. H. Bailey - saponin C (also known as DT-13) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in comparison to the well-known saponin ginsenoside Rk1 and anti-inflammatory drug dexamethasone. We proved that DT-13 reduces LPS-induced inflammation by inhibiting nitric oxide (NO) production, interleukin-6 (IL-6) release, cycloxygenase-2 (COX-2), tumour necrosis factor-alpha (TNF-α) gene expression, and nuclear factor kappa-B (NFκB) translocation into the nucleus. It also inhibits the inflammasome component NOD-like receptor family pyrin domain containing protein 3 (NLRP3) regulating the inflammasome activation. This was supported by the significant inhibition of caspase-1 and interleukin-1 beta (IL-1ß) expression and release. This study demonstrates the anti-inflammatory effect of saponins on LPS-stimulated macrophages. For the first time, an in vitro study shows the attenuating effect of DT-13 on NLRP3-inflammasome activation. In comparison to the existing anti-inflammatory drug, dexamethasone, and triterpenoid saponin Rk1, DT-13 more efficiently inhibits inflammation in the applied cell culture model. Therefore, DT-13 may serve as a lead compound for the development of new more effective anti-inflammatory drugs with minimised side effects.

The Effect of Akkermansia muciniphila and Its Outer Membrane Vesicles on MicroRNAs Expression of Inflammatory and Anti-inflammatory Pathways in Human Dendritic Cells.

Probiotics play a crucial role in immunomodulation by regulating dendritic cell (DC) maturation and inducing tolerogenic DCs. Akkermansia muciniphila affects inflammatory response by elevating inhibitory cytokines. We aimed to evaluate whether Akkermansia muciniphila and its outer membrane vesicles (OMVs) affect microRNA-155, microRNA-146a, microRNA-34a, and let-7i expression of inflammatory and anti-inflammatory pathways. Peripheral blood mononuclear cells (PBMCs) were isolated from the healthy volunteers. To produce DCs, monocytes were cultivated with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). DCs were allocated into six subgroups: DC + Lipopolysaccharide (LPS), DC + dexamethasone, DC + A. muciniphila (MOI 100, 50), DC + OMVs (50 µg/ml), and DC + PBS. The surface expression of human leukocyte antigen-antigen D related (HLA-DR), CD86, CD80, CD83, CD11c, and CD14 was examined using flow cytometry, and the expression of microRNAs was assessed using qRT-PCR, and the levels of IL-12 and IL-10 were measured using ELISA. A. muciniphila (MOIs 50, 100) could significantly decrease IL-12 levels relative to the LPS group. The IL-10 levels were decreased in the DC + LPS group than the DC + dexamethasone group. Treatment with A. muciniphila (MOI 100) and OMVs could elevate the concentrations of IL-10. DC treatment with LPS led to a significant increment in the expression of microRNA-155, microRNA-34a, and microRNA-146a. The expression of these microRNAs was reversed by A. muciniphilia and its OMVs treatment. Let-7i increased in treatment groups compared to the DC + LPS group. A. muciniphilia (MOI 50) had a substantial effect on the expression of HLA-DR, CD80, and CD83 on DCs. Therefore, DCs treatment with A. muciniphila led to induce tolerogenic DCs and the production of anti-inflammatory IL-10.

Comparison of the Glucocorticoid Receptor Binding and Agonist Activities of Typical Glucocorticoids: Insights into Their Endocrine Disrupting Effects.

Over the past decades, the synthetic glucocorticoids (GCs) have been widely used in clinical practice and animal husbandry. Given the health hazard of these toxic residues in food, it is necessary to explore the detailed interaction mechanisms of typical GCs and their main target glucocorticoid receptor (GR). Hence, this work compared the GR binding and agonist activities of typical GCs. Fluorescence polarization assay showed that these GCs were potent ligands of GR. Their GR binding affinities were in the order of methylprednisolone>betamethasone≈prednisolone>dexamethasone, with IC50 values of 1.67, 2.94, 2.95, and 5.58 nM. Additionally, the limits of detection of dexamethasone, betamethasone, prednisolone, and methylprednisolone were 0.32, 0.14, 0.19, and 0.09 µg/kg in fluorescence polarization assay. Reporter gene assay showed that these GCs induced GR transactivation in a dose-dependent manner, confirming their GR agonist activities. Among which, dexamethasone at the concentration of 100 nM produced a maximal induction of more than 11-fold over the blank control. Molecular docking and molecular dynamics simulations suggested that hydrogen-bonding and hydrophobic interactions played an important role in stabilizing the GC-GR-LBD complexes. In summary, this work might help to understand the GR-mediated endocrine disrupting effects of typical GCs.

CXCR2-Blocking Has Context-Sensitive Effects on Rat Glioblastoma Cell Line Outgrowth (S635) in an Organotypic Rat Brain Slice Culture Depending on Microglia-Depletion (PLX5622) and Dexamethasone Treatment.

In glioblastoma (GBM), the interplay of different immune cell subtypes, cytokines, and/or drugs shows high context-dependencies. Interrelations between the routinely applied dexamethasone (Dex) and microglia remain elusive. Here, we exploited rat organotypic brain slice co-cultures (OBSC) to examine the effects on a rat GBM cell line (S635) outgrowth resulting from the presence of Dex and pretreatment with the colony-stimulating factor receptor 1 (CSF1-R) inhibitor PLX5622: in native OBSC (without PLX5622-pretreatment), a diminished S635 spheroid outgrowth was observable, whereas Dex-treatment enhanced outgrowth in this condition compared to PLX5622-pretreated OBSC. Screening the supernatants of our model with a proteome profiler, we found that CXCL2 was differentially secreted in a Dex- and PLX5622-dependent fashion. To analyze causal interrelations, we interrupted the CXCL2/CXCR2-axis: in the native OBSC condition, CXCR2-blocking resulted in increased outgrowth, in combination with Dex, we found potentiated outgrowth. No effect was found in the PLX5622-pretreated. Our method allowed us to study the influence of three different factors-dexamethasone, PLX5622, and CXCL2-in a well-controlled, simplified, and straight-forward mechanistic manner, and at the same time in a more realistic ex vivo scenario compared to in vitro studies. In our model, we showed a GBM outgrowth enhancing synergism between CXCR2-blocking and Dex-treatment in the native condition, which was levelled by PLX5622-pretreatment.

Examining the Potential of Vitamin C Supplementation in Tissue-Engineered Equine Superficial Digital Flexor Tendon Constructs.

Because equine tendinopathies are slow to heal and often recur, therapeutic strategies are being considered that aid tendon repair. Given the success of utilizing vitamin C to promote tenogenesis in other species, we hypothesized that vitamin C supplementation would produce dose-dependent improvements in the tenogenic properties of tendon proper (TP) and peritenon (PERI) cells of the equine superficial digital flexor tendon (SDFT). Equine TP- and PERI-progenitor-cell-seeded fibrin three-dimensional constructs were supplemented with four concentrations of vitamin C. The gene expression profiles of the constructs were assessed with 3'-Tag-Seq and real-time quantitative polymerase chain reaction (RT-qPCR); collagen content and fibril ultrastructure were also analyzed. Moreover, cells were challenged with dexamethasone to determine the levels of cytoprotection afforded by vitamin C. Expression profiling demonstrated that vitamin C had an anti-inflammatory effect on TP and PERI cell constructs. Moreover, vitamin C supplementation mitigated the degenerative pathways seen in tendinopathy and increased collagen content in tendon constructs. When challenged with dexamethasone in two-dimensional culture, vitamin C had a cytoprotective effect for TP cells but not necessarily for PERI cells. Future studies will explore the effects of vitamin C on these cells during inflammation and within the tendon niche in vivo.

The Tolerogenic Influence of Dexamethasone on Dendritic Cells Is Accompanied by the Induction of Efferocytosis, Promoted by MERTK.

Many treatments for autoimmune diseases, caused by the loss of immune self-tolerance, are broadly immunosuppressive. Dendritic cells (DCs) can be induced to develop anti-inflammatory/tolerogenic properties to suppress aberrant self-directed immunity by promoting immune tolerance in an antigen-specific manner. Dexamethasone can generate tolerogenic DCs and upregulates MERTK expression. As MERTK can inhibit inflammation, we investigated whether dexamethasone's tolerogenic effects are mediated via MERTK, potentially providing a novel therapeutic approach. Monocyte-derived DCs were treated with dexamethasone, and with and without MERTK ligands or MERTK inhibitors. Flow cytometry was used to assess effects of MERTK modulation on co-stimulatory molecule expression, efferocytosis, cytokine secretion and T cell proliferation. The influence on expression of Rab17, which coordinates the diversion of efferocytosed material away from cell surface presentation, was assessed. Dexamethasone-treated DCs had upregulated MERTK expression, decreased expression of co-stimulatory molecules, maturation and proliferation of co-cultured T cells and increased uptake of myelin debris. MERTK ligands did not potentiate these properties, whilst specific MERTK inhibition only reversed dexamethasone's effect on myelin uptake. Cells undergoing efferocytosis had higher Rab17 expression. Dexamethasone-enhanced efferocytosis in DCs is MERTK-dependent and could exert its tolerogenic effects by increasing Rab17 expression to prevent the presentation of efferocytosed material on the cell surface to activate adaptive immune responses.

All-trans retinoic acid and dexamethasone regulate phagocytosis-related gene expression and enhance dead cell uptake in C2C12 myoblast cells.

Extensive mechanical stress frequently causes micro-traumas in skeletal muscle, followed by a regeneration period. The effective removal of dead myofibers is a prerequisite for proper regeneration, and several cell types, including professional phagocytes, were reported to be active in this process. Myoblasts express several molecules of the phagocytic machinery, such as BAI1, stabilin-2, and TAM (Tyro3, Axl, Mertk) tyrosine kinase receptors, but these molecules were reported to serve primarily cell fusion and survival, and their role in the phagocytosis was not investigated. Therefore, we aimed to investigate the in vitro phagocytic capacity of the C2C12 mouse myoblast cell line. RNA sequencing data were analyzed to determine the level and changes of phagocytosis-related gene expression during the differentiation process of C2C12 cells. To study the phagocytic capacity of myoblasts and the effect of dexamethasone, all-trans retinoic acid, hemin, and TAM kinase inhibitor treatments on phagocytosis, C2C12 cells were fed dead thymocytes, and their phagocytic capacity was determined by flow cytometry. The effect of dexamethasone and all-trans retinoic acid on phagocytosis-related gene expression was determined by quantitative PCR. Both undifferentiated and differentiated cells engulfed dead cells being the undifferentiated cells more effective. In line with this, we observed that the expression of several phagocytosis-related genes was downregulated during the differentiation process. The phagocytosis could be increased by dexamethasone and all-trans retinoic acid and decreased by hemin and TAM kinase inhibitor treatments. Our results indicate that myoblasts not only express phagocytic machinery genes but are capable of efficient dead cell clearance as well, and this is regulated similarly, as reported in professional phagocytes.

The role of dexamethasone in mediating the contradictory effects of Wnt antagonists SFRP2 and SFRP3 on human hair follicle growth.

Stress can be one of the leading causes of hair loss. Stress related hormones, glucocorticoids (GCs), secretion by hair follicle have been mentioned in literature and proven to exert an inhibitory effect on hair follicle cells growth by modulating the expression of target genes related to cell proliferation and cycling. The gene modulating effect of the synthetic GC, dexamethasone (DEX), in human dermal papilla (DP) cells has been outlined in this study by mediating a contradictory effect on the expression of secreted frizzled related protein 2 (SFRP2) and SFRP3. The SFRP2 and SFRP3 possess a regulating effect on wnt signaling pathway. Their structural similarities to the cysteine-rich-domain of the frizzled receptors (FZD) allow their binding to the wnt ligands causing the blocking of the wnt ligands-receptors complex. The SFRP family members have been known as inhibitors of the wnt signaling modulating the proliferation and development of various cells. In hair follicle cells, SFRP2 activity has been reported positively on the proliferation of keratinocytes. However, the SFRP3 effect hasn't been well addressed. Under stress, the investigation of the mRNA and protein expressions of SFRP members in human DP cells revealed opposite expressions where SFRP2 decreased while SFRP3 increased by DEX. The proliferation rate of hair keratinocytes outer root sheath was detected via immunofluorescence highlighting the stimulatory effect of SFRP2 and the inhibitory effect of SFRP3. Here, we sought to determine the effect of GC agonist on SFRPs expression and their effect on hair follicle growth.

Mfat-1 ameliorates cachexia after hypoxic-ischemic brain damage in mice by protecting the hypothalamus-pituitary-adrenal axis.

AIMS: Cachexia, a metabolic syndrome, affects 21 % of patients suffering from ischemic encephalopathy. However, the specific mechanism and prevention measures are still unclear. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been proven to reduce inflammatory cytokine levels during ischemic events, but whether they have a protective effect against cachexia after hypoxic-ischemic brain damage (HIBD) remains unclear. MAIN METHODS: C57BL/6J wild-type and mfat-1 transgenic male mice were treated with and without HIBD. One day after HIBD, the epididymal white fat, gastrocnemius muscle and hypothalamus were weighed and analyzed the phenotypic changes. RNA sequencing was applied to gastrocnemius muscle to identify differential genes and pathways in HIBD groups. The effect of HPA axis on cachexia post-HIBD was examined via adrenalectomy, dexamethasone (0.1 mg/kg), and corticosterone injection (100 mg/kg). KEY FINDINGS: The results showed that the incidence of cachexia in mfat-1 mice, which produce high proportion of n-3 PUFAs, was significantly lower than that in wild-type mice post-HIBD. Cachexia-related factors, such as inflammation, muscle atrophy and lipid metabolism were significantly improved in mfat-1 HIBD. RNA sequencing revealed that catabolic and proteasome pathways were significantly downregulated. In hypothalamus, inflammatory cytokines, lipid peroxidation levels were reduced. Corticosterone, glucocorticoid receptor, and dexamethasone suppression test all showed that mfat-1 improved the dysfunction of the HPA axis post-HIBD. The present study elucidated for the first time that mfat-1 reduced HIBD-induced hyperactivation of the HPA axis in mice by reducing inflammation and oxidative stress and contributed to the reduction of metabolic imbalance in peripheral tissues. SIGNIFICANCE: Our study provides mechanistic information for the development of intervention strategies to prevent cachexia.

Cyasterone has a protective effect on steroid-induced Osteonecrosis of the femoral head.

CONTEXT: Cyasterone alleviated the apoptosis of BMSCs induced by Dexamethasone via the PI3K/AKT signaling pathway. In addition, Cyasterone had a protective effect on SIONFH model rats by reducing the percentage of empty bone lacunae. OBJECTIVE: To study the effect of Cyasterone on apoptosis of rat BMSCs and its function on the SIONFH rat model. METHODS: Rat BMSCs were cultured and divided into Control, DXM and Cyasterone (DXM+Cyasterone) groups. The apoptosis of each group was detected by flow cytometry, the expressions of Caspase-3 and Caspase-9 were detected by immunofluorescence staining, and the mRNA and protein expressions of AKT, BAX, P53, P85, Bcl-2 and Cytochrome C were detected by qPCR and WB. In animal experiments, the femoral head of rats were subjected to HE staining and Micro-CT to observe the necrosis and repair conditions. RESULTS: The apoptosis rate of DXM and Cyasterone groups increased compared with Control group, and the apoptosis rate of Cyasterone group decreased compared with DXM group. Compared with DXM group, the mRNA expression of BAX, P53, P85 and Cytochrome C in Cyasterone group were increased, while the protein expression of AKT and Bcl-2 decreased. The histopathological and morphological analysis showed that Cyasterone promoted the trabecular bone structure in rat, which evenly benefit for the repair of SIONFH. CONCLUSION: Cyasterone can reduce the apoptosis of rat BMSCs induced by Dexamethasone, and help promoting the bone repair in SIONFH rats.

Apocynin exerts cytoprotective effects on dexamethasone-induced osteoblasts by inhibiting oxidative stress through the Nrf2 signalling pathway.

Steroid-induced femoral head necrosis (SIFHN) is a serious clinical complication that is caused by prolonged or excessive use of glucocorticoids (GCs). Osteoblast apoptosis and osteogenic differentiation dysfunction caused by GC-induced oxidative stress and mitochondrial impairment are strongly implicated in SIFHN. Apocynin (APO) is a kind of acetophenone extracted from an herb. In recent years, APO has received much attention for its antiapoptotic and antioxidant properties. This study aimed to investigate whether APO could protect against SIFHN and explore the mechanism. In our study, low-dose APO had no toxic effects on osteoblasts and restored dexamethasone (Dex)-treated osteoblasts by improving survival, inhibiting OS and restoring mitochondrial dysfunction. Mechanistically, APO alleviated Dex-induced osteoblast injury by activating the Nrf2 pathway, and the use of ML385 to block Nrf2 significantly eliminated the protective effect of APO. In addition, APO could reduce the formation of empty lacunae, restore bone mass and promote the expression of Nrf2 in SIFHN rats. In conclusion, APO protects osteoblasts from Dex-induced oxidative stress and mitochondrial dysfunction through activation of the Nrf2 pathway and may be a beneficial drug for the treatment of SIFHN.

Overactivated Epithelial NF-κB Disrupts Lung Development in Congenital Diaphragmatic Hernia.

Abnormal lung development is the main cause of morbidity and mortality in neonates with congenital diaphragmatic hernia (CDH), a common birth defect (1:2,500) of largely unknown pathobiology. Recent studies discovered that inflammatory processes, and specifically NF-κB-associated pathways, are enriched in human and experimental CDH. However, the molecular signaling of NF-κB in abnormal CDH lung development and its potential as a therapeutic target require further investigation. Using sections and hypoplastic lung explant cultures from the nitrofen rat model of CDH and human fetal CDH lungs, we demonstrate that NF-κB and its downstream transcriptional targets are hyperactive during abnormal lung formation in CDH. NF-κB activity was especially elevated in the airway epithelium of nitrofen and human CDH lungs at different developmental stages. Fetal rat lung explants had impaired pseudoglandular airway branching after exposure to nitrofen, together with increased phosphorylation and transcriptional activity of NF-κB. Dexamethasone, the broad and clinically applicable antiinflammatory NF-κB antagonist, rescued lung branching and normalized NF-κB signaling in hypoplastic lung explants. Moreover, specific NF-κB inhibition with curcumenol similarly rescued ex vivo lung hypoplasia and restored NF-κB signaling. Last, we showed that prenatal intraperitoneal dexamethasone administration to pregnant rat dams carrying fetuses with hypoplastic lungs significantly improves lung branching and normalizes NF-κB in vivo. Our results indicate that NF-κB is aberrantly activated in human and nitrofen CDH lungs. Antiinflammatory treatment with dexamethasone and/or specific NF-κB inhibition should be investigated further as a therapeutic avenue to target lung hypoplasia in CDH.

Crosstalk between glucocorticoid and mineralocorticoid receptors boosts glucocorticoid-induced killing of multiple myeloma cells.

The glucocorticoid receptor (GR) is a crucial drug target in multiple myeloma as its activation with glucocorticoids effectively triggers myeloma cell death. However, as high-dose glucocorticoids are also associated with deleterious side effects, novel approaches are urgently needed to improve GR action in myeloma. Here, we reveal a functional crosstalk between GR and the mineralocorticoid receptor (MR) that plays a role in improved myeloma cell killing. We show that the GR agonist dexamethasone (Dex) downregulates MR levels in a GR-dependent way in myeloma cells. Co-treatment of Dex with the MR antagonist spironolactone (Spi) enhances Dex-induced cell killing in primary, newly diagnosed GC-sensitive myeloma cells. In a relapsed GC-resistant setting, Spi alone induces distinct myeloma cell killing. On a mechanistic level, we find that a GR-MR crosstalk likely arises from an endogenous interaction between GR and MR in myeloma cells. Quantitative dimerization assays show that Spi reduces Dex-induced GR-MR heterodimerization and completely abolishes Dex-induced MR-MR homodimerization, while leaving GR-GR homodimerization intact. Unbiased transcriptomics analyses reveal that c-myc and many of its target genes are downregulated most by combined Dex-Spi treatment. Proteomics analyses further identify that several metabolic hallmarks are modulated most by this combination treatment. Finally, we identified a subset of Dex-Spi downregulated genes and proteins that may predict prognosis in the CoMMpass myeloma patient cohort. Our study demonstrates that GR-MR crosstalk is therapeutically relevant in myeloma as it provides novel strategies for glucocorticoid-based dose-reduction.

Oral cortisol and dexamethasone intake: Differential physiology and transcriptional responses in the marine juvenile Sparus aurata.

This study approached the long-term oral administration of cortisol (F) and dexamethasone (DEX), two synthetic glucocorticoids, compared to a control group (CT) in the juveniles of a marine teleost, the gilthead seabream (Sparus aurata). Physiologically, DEX treatment impaired growth, which appears to be linked to carbohydrate allocation in muscle and liver, hepatic triglycerides depletion, and reduced hematocrit. Hypophyseal gh mRNA expression was 2-fold higher in DEX than in CT or F groups. Similarly, hypothalamic trh and hypophyseal pomcb followed this pattern. Plasma cortisol levels were significantly lower in DEX than in CT, while F presented intermediate levels. In the posterior intestine, measured short circuit-current (Isc) was more anion absorptive in CT and F compared to the DEX group, whereas Isc remained unaffected in the anterior intestine. The derived transepithelial electric resistance (TEER) significantly differed between intestinal regions in the DEX group. These results provide new insights to understand better potential targeted biomarkers indicative of the differential glucocorticoid or mineralocorticoid-receptors activation in fish.

The Effect of Dexamethasone on Lipopolysaccharide-induced Inflammation of Endothelial Cells of the Blood-brain Barrier/Brain Capillaries.

BACKGROUND: A protective and regulatory barrier between the blood and the brain is constituted by the blood-brain barrier (BBB), which comprises microvascular endothelial cells providing homeostatic regulation of the central nervous system (CNS). Inflammation compromises the BBB and contributes to many CNS disorders. Anti-inflammatory effects are exerted by glucocorticoids (GCs) on a variety of cells. These GCs include dexamethasone (Dex), which is used for the treatment of inflammatory diseases and recently for the treatment of COVID-19. AIM: The purpose of this study was to determine whether low or high concentrations of Dex can attenuate the inflammatory response induced by lipopolysaccharide (LPS) in the in vitro BBB model. METHODS: Brain endothelial cells (bEnd.5) were cultured and exposed to LPS (100ng/ml) and subsequently co-treated with Dex to investigate whether selected concentrations of Dex (0.1, 5, 10, 20µM) can modulate the inflammatory effects of LPS on bEnd.5 cells. Cell viability, cell toxicity, and cell proliferation were investigated, as well as the monitoring of membrane permeability (Trans Endothelial Electrical Resistance-TEER), and Enzyme-Linked Immune Assay (ELISA) kits were used to identify and quantify the presence of inflammatory cytokines (TNF-α and IL-1ß). RESULTS: Dex, at a lower dosage (0.1µM, but not higher doses), was able to attenuate the inflammatory effects of LPS on bEnd.5 cells. Lower doses of Dex (0.1µM) had no detrimental effects on bEnd.5 cells, while higher Dex doses (5-20µM) decreased bEnd.5 viability, increased bEnd.5 cell toxicity, increased bEnd.5 cell monolayer permeability, and increased proinflammatory cytokine secretion. CONCLUSION: These results indicate that treatment of brain vascular inflammation with low doses of Dex should be advocated, while higher doses promote vascular inflammation.

Nucleic acid sensor STING drives remodeling and its inhibition enhances steroid responsiveness in chronic obstructive pulmonary disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is progressive and irreversible chronic lung inflammatory disease. Cigarette smoke, the main cause of COPD, is often associated with double-stranded DNA release which potentially activates DNA-sensing pathways, such as STING. This study, therefore, analyzed the role of STING pathway in inducing pulmonary inflammation, steroid resistance, and remodeling in COPD. METHODS: Primary cultured lung fibroblasts were isolated from healthy non-smoker, healthy smoker, and smoker COPD individuals. The expression of STING pathway, remodeling, and steroid resistance signatures were investigated in these fibroblasts upon LPS stimulation and treatment with dexamethasone and/or STING inhibitor, at both mRNA and protein levels using qRT-PCR, western blot, and ELISA. RESULTS: At baseline, STING was elevated in healthy smoker fibroblasts and to a higher extent in smoker COPD fibroblasts when compared to healthy non-smoker fibroblasts. Upon using dexamethasone as monotherapy, STING activity was significantly inhibited in healthy non-smoker fibroblasts but showed resistance in COPD fibroblasts. Treating both healthy and COPD fibroblasts with STING inhibitor in combination with dexamethasone additively inhibited STING pathway in both groups. Moreover, STING stimulation triggered a significant increase in remodeling markers and a reduction in HDAC2 expression. Interestingly, treating COPD fibroblasts with the combination of STING inhibitor and dexamethasone alleviated remodeling and reversed steroid hyporesponsiveness through an upregulation of HDAC2. CONCLUSION: These findings support that STING pathway plays an important role in COPD pathogenesis, via inducing pulmonary inflammation, steroid resistance, and remodeling. This raises the possibility of using STING inhibitor as a potential therapeutic adjuvant in combination with common steroid treatment.

Ambiguous Contribution of Glucocorticosteroids to Acute Neuroinflammation in the Hippocampus of Rat.

Effects of modulation of glucocorticoid and mineralocorticoid receptors (GR and MR, respectively) on acute neuroinflammatory response were studied in the dorsal (DH) and ventral (VH) parts of the hippocampus of male Wistar rats. Local neuroinflammatory response was induced by administration of bacterial lipopolysaccharide (LPS) to the DH. The modulation of GR and MR was performed by dexamethasone (GR activation), mifepristone, and spironolactone (GR and MR inhibition, respectively). Experimental drugs were delivered to the dentate gyrus of the DH bilaterally by stereotaxic injections. Dexamethasone, mifepristone, and spironolactone were administered either alone (basal conditions) or in combination with LPS (neuroinflammatory conditions). Changes in expression levels of neuroinflammation-related genes and morphology of microglia 3 days after intrahippocampal administration of above substances were assessed. Dexamethasone alone induced a weak proinflammatory response in the hippocampal tissue, while neither mifepristone nor spironolactone showed significant effects. During LPS-induced neuroinflammation, GR activation suppressed expression of selected inflammatory genes, though it did not prevent appearance of activated forms of microglia. In contrast to GR activation, GR or MR inhibition had virtually no influence on LPS-induced inflammatory response. The results suggest glucocorticosteroids ambiguously modulate specific aspects of neuroinflammatory response in the hippocampus of rats at molecular and cellular levels.

Class I HDAC inhibitors attenuate dexamethasone-induced muscle atrophy via increased protein kinase C (PKC) delta phosphorylation.

Skeletal muscle atrophy is defined by wasting or decrease in muscle mass owing to injury, aging, malnutrition, chronic disuse, or physical consequences of chronic illness. Under normal physiological conditions, a network of signal transduction pathways serves to balance muscle protein synthesis and proteolysis; however, metabolic shifts occur from protein synthesis to protein degradation that leads to a reduction in cross-sectional myofibers and can result in loss of skeletal muscle mass (atrophy) over time. Recent evidence highlights posttranslational modifications (PTMs) such as acetylation and phosphorylation in contractile dysfunction and muscle wasting. Indeed, histone deacetylase (HDAC) inhibitors have been shown to attenuate muscle atrophy and delay muscle damage in response to nutrient deprivation, in models of metabolic dysfunction and genetic models of muscle disease (e.g., muscle dystrophy). Despite our current understanding of lysine acetylation in muscle physiology, a role for HDACs in the regulation of muscle signal transduction remains a 'black box.' Using C2C12 myotubes stimulated with dexamethasone (Dex) as a model of muscle atrophy, we report that protein kinase C delta (PKCδ) phosphorylation decreased at threonine 505 (T505) and serine 643 (S643) in myotubes in response to muscle atrophy; these residues are important for PKCδ activity. Interestingly, PKCδ phosphorylation was restored/increased in myotubes treated with a pan-HDAC inhibitor or a class I selective HDAC inhibitor targeting HDACs1, -2, and - 3 in response to Dex. Moreover, we observed that Dex induced atrophy in skeletal muscle tissue in mice; this reduction in atrophy occurred rapidly, with weight loss noted by day 3 post-Dex and muscle weight loss noted by day 7. Similar to our findings in C2C12 myotubes, Dex attenuated phosphorylation of PKCδ at S643, while HDAC inhibition restored or increased PKCδ phosphorylation at both T505 and S643 in the tibialis anterior. Consistent with this hypothesis, we report that HDAC inhibition could not restore myotube size in response to Dex in the presence of a PKCδ inhibitor or when overexpressing a dominant negative PKCδ. Additionally, the overexpression of a constitutively active PKCδ prevented Dex-induced myotube atrophy. Combined, these data suggest that HDACs regulate muscle physiology via changes in intracellular signaling, namely PKCδ phosphorylation. Whether HDACs regulate PKCδ through canonical (e.g. gene-mediated regulation of phosphatases) or non-canonical (e.g. direct deacetylation of PKCδ to change phosphorylation states) mechanisms remain unclear and future research is needed to clarify this point.

Differential regulation of BIRC2 and BIRC3 expression by inflammatory cytokines and glucocorticoids in pulmonary epithelial cells.

Roles for the baculoviral inhibitor of apoptosis repeat-containing (BIRC) genes, BIRC2 and BIRC3, may include signaling to the inflammatory transcription factor, nuclear factor-κB (NF-κB) and protection from cell death. However, distinct functions for each BIRC are not well-delineated. Given roles for the epithelium in barrier function and host defence, BIRC2 and BIRC3 expression was characterized in pulmonary epithelial cell lines and primary human bronchial epithelial cells (pHBECs) grown as undifferentiated cells in submersion culture (SC) or as highly differentiated cells at air-liquid interface (ALI). In A549 cells, interleukin-1ß (IL1B) and tumor necrosis factor α (TNF) induced BIRC3 mRNA (~20-50-fold), with maximal protein expression from 6-24 h. Similar effects occurred in BEAS-2B and Calu-3 cells, as well as SC and ALI pHBECs. BIRC2 protein was readily detected in unstimulated cells, but was not markedly modulated by IL1B or TNF. Glucocorticoids (dexamethasone, budesonide) modestly increased BIRC3 mRNA and protein, but showed little effect on BIRC2 expression. In A549 cells, BIRC3 mRNA induced by IL1B was unchanged by glucocorticoids and showed supra-additivity with TNF-plus-glucocorticoid. Supra-additivity was also evident for IL1B-plus-budesonide induced-BIRC3 in SC and ALI pHBECs. Using A549 cells, IL1B- and TNF-induced BIRC3 expression, and to a lesser extent, BIRC2, was prevented by NF-κB inhibition. Glucocorticoid-induced BIRC3 expression was prevented by silencing and antagonism of the glucocorticoid receptor. Whereas TNF, but not IL1B, induced degradation of basal BIRC2 and BIRC3 protein, IL1B- and TNF-induced BIRC3 protein remained stable. Differential regulation by cytokines and glucocorticoids shows BIRC2 protein expression to be consistent with roles in rapid signaling events, whereas cytokine-induced BIRC3 may be more important in later effects. While TNF-induced degradation of both BIRCs may restrict their activity, cytokine-enhanced BIRC3 expression could prime for its function. Finally, shielding from glucocorticoid repression, or further enhancement by glucocorticoid, may indicate a key protective role for BIRC3.

RNA binding by the glucocorticoid receptor attenuates dexamethasone-induced gene activation.

The glucocorticoid receptor (GR) is a ligand-activated transcription factor that regulates a suite of genes through direct binding of GR to specific DNA promoter elements. GR also interacts with RNA, but the function of this RNA-binding activity remains elusive. Current models speculate that RNA could repress the transcriptional activity of GR. To investigate the function of the GR-RNA interaction on GR's transcriptional activity, we generated cells that stably express a mutant of GR with reduced RNA binding affinity and treated the cells with the GR agonist dexamethasone. Changes in the dexamethasone-driven transcriptome were quantified using 4-thiouridine labeling of RNAs followed by high-throughput sequencing. We find that while many genes are unaffected, GR-RNA binding is repressive for specific subsets of genes in both dexamethasone-dependent and independent contexts. Genes that are dexamethasone-dependent are activated directly by chromatin-bound GR, suggesting a competition-based repression mechanism in which increasing local concentrations of RNA may compete with DNA for binding to GR at sites of transcription. Unexpectedly, genes that are dexamethasone-independent instead display a localization to specific chromosomal regions, which points to changes in chromatin accessibility or architecture. These results show that RNA binding plays a fundamental role in regulating GR function and highlights potential functions for transcription factor-RNA interactions.