Enhanced glucocorticoid-induced leucine zipper in dendritic cells induces allergen-specific regulatory CD4(+) T-cells in respiratory allergies

GILZ as a Regulator of Cell Fate and Inflammation

One of the human body’s initial responses to stress is the adrenal response, involving the release of mediators that include adrenaline and glucocorticoids (GC). GC are involved in controlling the inflammatory and immune response mechanisms. Of these, the molecular mechanisms that contribute to anti-inflammatory effects warrant more investigation. Previously, we found that GC induced GILZ (glucocorticoid-induced leucine zipper) quickly and widely in thymocytes, T lymphocytes, and other leukocytes. GILZ regulates the activation of cells and is an essential mediator of endogenous GC and the majority of GC anti-inflammatory effects. Further research in this regard could lead to the development of an anti-inflammatory treatment that yields the therapeutic outcomes of GC but without their characteristic adverse effects. Here, we examine the mechanisms of GILZ in the context of GC. Specifically, we review its role in the proliferation and differentiation of cells and in apoptosis. We also examine its involvement in immune cells (macrophages, neutrophils, dendritic cells, T and B lymphocytes), and in non-immune cells, including cancer cells. In conclusion, GILZ is an anti-inflammatory molecule that could mediate the immunomodulatory activities of GC, with less adverse effects, and could be a target molecule for designing new therapies to treat inflammatory diseases.

Multi-Tissue Characterization of GILZ Expression in Dendritic Cell Subsets at Steady State and in Inflammatory Contexts

Dendritic cells (DCs) are key players in the control of tolerance and immunity. Glucocorticoids (GCs) are known to regulate DC function by promoting their tolerogenic differentiation through the induction of inhibitory ligands, cytokines, and enzymes. The GC-induced effects in DCs were shown to critically depend on increased expression of the Glucocorticoid-Induced Leucine Zipper protein (GILZ). GILZ expression levels were further shown to control antigen-presenting cell function, as well as T-cell priming capacity of DCs. However, the pattern of GILZ expression in DC subsets across tissues remains poorly described, as well as the modulation of its expression levels in different pathological settings. To fill in this knowledge gap, we conducted an exhaustive analysis of GILZ relative expression levels in DC subsets from various tissues using multiparametric flow cytometry. This study was performed at steady state, in the context of acute as well as chronic skin inflammation, and in a model of cancer. Our results show the heterogeneity of GILZ expression among DC subsets as well as the complexity of its modulation, that varies in a cell subset- and context-specific manner. Considering the contribution of GILZ in the control of DC functions and its potential as an immune checkpoint in cancer settings, these results are of high relevance for optimal GILZ targeting in therapeutic strategies.

Overexpression of GILZ in macrophages limits systemic inflammation while increasing bacterial clearance in sepsis in mice

Studies support the beneficial effects of glucocorticoids (GCs) during septic shock, steering research toward the potential role of GC-induced proteins in controlling excessive inflammatory responses. GILZ is a glucocorticoid-induced protein involved in the anti-inflammatory effects of GCs. We investigated whether the overexpression of GILZ specifically limited to monocytes and macrophages (M/M) alone could control inflammation, thus improving the outcome of septic shock in animal models. We also monitored the expression of GILZ in M/M from septic mice and septic-shock patients. M/M from patients and septic mice displayed significantly lower expression of GILZ than those isolated from controls. Furthermore, transgenic mice (Tg-mice) experiencing sepsis, with increased expression of GILZ restricted to M/M, showed lower frequencies of inflammatory monocytes than their littermates and lower plasma levels of inflammatory cytokines. Tg-mice also had lower blood bacterial counts. We further established that the upregulation of GILZ in M/M enhanced their phagocytic capacity in in vivo assays. The increase of GILZ in M/M was also sufficient to improve the survival rates of septic mice. These results provide evidence for a central role of both GILZ and M/M in the pathophysiology of septic shock and a possible clue for the modulation of inflammation in this disease.

Comparative Expression Analysis of Stress-Inducible Genes in Murine Immune Cells

Background: Psychological stress affects the immune system. Upon stress occurrence, glucocorticoid is released that binds to the glucocorticoid receptor and regulates gene expression. Thus, we aimed to examine the stress-induced immunomodulatory mechanisms by investigating the expression patterns of stress-inducible genes in murine immune cells. Methods: BALB/c, C57BL/6, glucocorticoid-receptor congenic mice, and corticotropin-releasing hormone (CRH)-deficient mice were exposed to synthetic glucocorticoid, dexamethasone, or placed under a restraint condition. The expression level of stress-related genes, such as Rtp801, Gilz, Mkp-1, Bnip3, and Trp53inp1 was measured in the immune cells in these mice. Results: Short restraint stress induced Rtp801 and Gilz expressions that were higher in the spleen of BALB/c mice than those in C57BL/6 mice. Mkp-1 expression increased equally in these two strains, despite the difference in the glucocorticoid level. These three genes induced by short restraint stress were not induced in the CRH-deficient mice. In contrast, Bnip3 and Trp53inp1 were only upregulated upon longer restraint events. In the thymus, Trp53inp1 expression was induced upon short restraint stress, whereas Gilz expression constantly increased upon short and repetitive restraint stresses. Conclusion: These results suggest that singular and repetitive bouts of stress lead to differential gene expression in mice and stress-induced gene expression in thymocytes is distinct from that observed in splenocytes. Gilz, Rtp801, and Mkp-1 genes induced by short restraint stress are dependent on CRH in the spleen.

Synthetic Glucocorticoid-Induced Leucine Zipper Peptide Inhibits Lipopolysaccharide-Induced Ocular Inflammation in Rats

PURPOSE

To demonstrate the anti-inflammatory action of a synthetic glucocorticoid-induced leucine zipper (GILZ98-134) peptide (GILZ-p) in a model of endotoxin-induced uveitis (EIU) in rats.

METHODS

The EIU model was induced in Sprague Dawley rats with an intravitreal injection of lipopolysaccharide (LPS). Synthetic GILZ-p was injected intravitreally 6 h after the LPS injection. To evaluate the anti-inflammatory effects of GILZ-p, the inflammatory response in the anterior chamber and iris of the rat eyes was evaluated with a slitlamp microscope on days 0, 1, 2, 3, and 4 after GILZ-p injection. The retinal expression of inflammatory cytokines was measured on days 0, 1, 2, 3, and 4 after GILZ-p injection. Müller cell gliosis was also detected at planned time points after GILZ-p injection.

RESULTS

Anterior segment inflammation peaked at 24 h after LPS injection in the EIU model. Compared with the controls, intravitreal GILZ-p significantly suppressed LPS-induced anterior segment inflammation in the EIU rats. The levels of retinal inflammatory factors IL-1β, TNF-α, MCP-1, and ICAM-1 were simultaneously reduced by the intravitreal GILZ-p injection. The expression of vimentin in the EIU retina was significantly reduced by GILZ-p, and the downregulated aquaporin 4 in the EIU retina was significantly restored by GILZ-p.

CONCLUSION

The synthetic GILZ-p inhibited the inflammatory reaction in the EIU model and may have utility in the treatment of inflammatory ocular disease.

Mechanisms of Subcutaneous and Sublingual Aeroallergen Immunotherapy: What Is New?

Allergen immunotherapy (AIT) is considered to be the only treatment option with the promise of healing and induction of long-lasting allergen tolerance, persisting even after discontinuation of therapy. Despite a more than 100-year-long history, still only a minority of patients are being treated with AIT. Substantial developments took place in the last decade to overcome problems in standardization, efficacy, safety, high costs, long duration of treatment; and new guidelines have also been implemented. Major advancements in the understanding of AIT mechanisms with the focus on recent findings of subcutaneous and sublingual AIT have been summarized.

Glucocorticoid-Induced Leucine Zipper: Fine-Tuning of Dendritic Cells Function

Dendritic cells (DCs) are key antigen-presenting cells that control the induction of both tolerance and immunity. Understanding the molecular mechanisms regulating DCs commitment toward a regulatory- or effector-inducing profile is critical for better designing prophylactic and therapeutic approaches. Initially identified in dexamethasone-treated thymocytes, the glucocorticoid-induced leucine zipper (GILZ) protein has emerged as a critical factor mediating most, but not all, glucocorticoids effects in both non-immune and immune cells. This intracellular protein exerts pleiotropic effects through interactions with transcription factors and signaling proteins, thus modulating signal transduction and gene expression. GILZ has been reported to control the proliferation, survival, and differentiation of lymphocytes, while its expression confers anti-inflammatory phenotype to monocytes and macrophages. In the past twelve years, a growing set of data has also established that GILZ expression in DCs is a molecular switch controlling their T-cell-priming capacity. Here, after a brief presentation of GILZ isoforms and functions, we summarize current knowledge regarding GILZ expression and regulation in DCs, in both health and disease. We further present the functional consequences of GILZ expression on DCs capacity to prime effector or regulatory T-cell responses and highlight recent findings pointing to a broader role of GILZ in the fine tuning of antigen capture, processing, and presentation by DCs. Finally, we discuss future prospects regarding the possible roles for GILZ in the control of DCs function in the steady state and in the context of infections and chronic pathologies.

Altered expression of circadian clock genes in polyglandular autoimmune syndrome type III

PURPOSE

Circadian timing system is a highly conserved, ubiquitous molecular "clock" which creates internal circadian rhythmicity. Dysregulation of clock genes expression is associated with various diseases including immune dysregulation. In this study we investigated the circadian pattern of Clock-related genes in patients with polyglandular autoimmune syndrome type III (PAS type III).

METHODS

Nineteen patients diagnosed with PAS type III and 12 healthy controls were enrolled. mRNA and protein expression of Clock-related genes (CLOCK, BMAL1, ROR and Per-1,-2,-3), as well as the GR-a and the GILZ genes were determined by real-time quantitative PCR and western blot analysis from blood samples drawn at 8 pm and 8am. Serum cortisol and TSH, as well as plasma ACTH, were measured by chemiluminescence.

RESULTS

There were no statistical significant differences in the metabolic profile, cortisol, ACTH and TSH levels between patients and controls. Patients with PAS type III expressed higher transcript levels of CLOCK, BMAL1 and Per-1 in the evening than in the morning (p = 0.03, p = 0.029, p = 0.013, respectively), while the ratios (R_pm/am) of GR-a, CLOCK, BMAL1, and Per-3 mRNA levels were statistically different between patients and controls. Cortisol circadian variation (F_pm/am) was positively correlated with GILZ mRNA circadian pattern (R_pm/am) in the patient group and with the GR-a mRNA (R_pm/am) in the control group.

CONCLUCIONS

Our findings suggest that there is an aberrant circadian rhythm of Clock-related genes in patients with PAS type III. The disruption of the expression of 4 circadian Clock-related genes could indicate a possible association with the pathogenesis of the disease.

Whole Transcriptome Sequencing Analyses Reveal Molecular Markers of Blood Pressure Response to Thiazide Diuretics

Thiazide diuretics (TD) are commonly prescribed anti-hypertensives worldwide. However, <40% of patients treated with thiazide monotherapy achieve BP control. This study uses whole transcriptome sequencing to identify novel molecular markers associated with BP response to TD. We assessed global RNA expression levels in whole blood samples from 150 participants, representing patients in the upper and lower quartile of BP response to TD from the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) (50 whites) and from PEAR-2 (50 whites and 50 blacks). In each study cohort, we performed poly-A RNA-sequencing in baseline samples from 25 responders and 25 non-responders to hydrochlorothiazide (HCTZ) or chlorthalidone. At FDR adjusted p-value < 0.05, 29 genes were differentially expressed in relation to HCTZ or chlorthalidone BP response in whites. For each differentially expressed gene, replication was attempted in the alternate white group and PEAR-2 blacks. CEBPD (meta-analysis p = 1.8 × 10⁻¹¹) and TSC22D3 (p = 1.9 × 10⁻⁹) were differentially expressed in all 3 cohorts, and explain, in aggregate, 21.9% of response variability to TD. This is the first report of the use of transcriptome-wide sequencing data to identify molecular markers of antihypertensive drug response. These findings support CEBPD and TSC22D3 as potential biomarkers of BP response to TD.

Glucocorticoid-induced leucine zipper expression is associated with response to treatment and immunoregulation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder in which cytokine balance is disturbed. Glucocorticoids (GCs) are shown to balance immune response by transcriptional regulation of glucocorticoid receptor target genes such as Glucocorticoid-induced leucine zipper (GILZ) which has been introduced as an endogenous anti-inflammatory mediator. In the present study, we assessed the expression of GILZ in association with interferon-γ (IFN-γ), interleukine-10 (IL-10), and B lymphocyte stimulator (BLyS) plasma levels in SLE patients. A total of 40 female patients (18 under treatment and 22 newly diagnosed) were recruited in this study. Real-time RT PCR was conducted to quantify the mRNA expression of GILZ. The plasma levels of IFN-γ, IL-10, and BLyS were evaluated using ELISA method. GILZ was overexpressed among under treatment SLE patients. The mRNA expression of GILZ was significantly correlated with Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score. IFN-γ and BLyS were downregulated in response to therapies with negative correlations to GILZ. Moreover, IL-10 was upregulated among treated patients. The levels of IFN-γ and BLyS were correlated with the severity of disease, while IL-10 was negatively correlated with SLEDAI score. GILZ could be introduced as one of the acting molecules in mediating the regulatory effects of GCs on producing pro- and anti-inflammatory cytokines in SLE.

Glucocorticoid-Induced Leucine Zipper Protein Controls Macropinocytosis in Dendritic Cells

Ag sampling is a key process in dendritic cell (DC) biology. DCs use constitutive macropinocytosis, receptor-mediated endocytosis, and phagocytosis to capture exogenous Ags for presentation to T cells. We investigated the mechanisms that regulate Ag uptake by DCs in the steady-state and after a short-term LPS exposure in vitro and in vivo. We show that the glucocorticoid-induced leucine zipper protein (GILZ), already known to regulate effector versus regulatory T cell activation by DCs, selectively limits macropinocytosis, but not receptor-mediated phagocytosis, in immature and recently activated DCs. In vivo, the GILZ-mediated inhibition of Ag uptake is restricted to the CD8α⁺ DC subset, which expresses the highest GILZ level among splenic DC subsets. In recently activated DCs, we further establish that GILZ limits p38 MAPK phosphorylation, providing a possible mechanism for GILZ-mediated macropinocytosis control. Finally, our results demonstrate that the modulation of Ag uptake by GILZ does not result in altered Ag presentation to CD4 T cells but impacts the efficiency of cross-presentation to CD8 T cells. Altogether, our results identify GILZ as an endogenous inhibitor of macropinocytosis in DCs, the action of which contributes to the fine-tuning of Ag cross-presentation.

A focused Real Time PCR strategy to determine GILZ expression in mouse tissues

Glucocorticoid-Induced Leucine Zipper (GILZ) is a glucocorticoid-inducible gene that mediates glucocorticoid anti-inflammatory effects. GILZ and the isoform L-GILZ are expressed in a variety of cell types, especially of hematopoietic origin, including macrophages, lymphocytes and epithelial cells, and strongly upregulated upon glucocorticoid treatment.

A quantitative analysis of GILZ expression in mouse tissues is technically difficult to perform because of the presence of a pseudogene and the high homology of GILZ gene with other genes of TSC22 family. We here propose specific primer pairs to be used in Real Time PCR to avoid unwanted amplification of GILZ pseudogene and TSC-22 family member d1iso3. These primer pairs were used to determine GILZ and L-GILZ expression, in either untreated or in vivo and in vitro dexamethasone-treated tissues. Results indicate that GILZ and L-GILZ are upregulated by glucocorticoids, being GILZ more sensitive to glucocorticoid induction than L-GILZ, but they are differently expressed in all examined tissues, confirming a different role in specific cells. An inappropriate primer pair amplified also GILZ pseudogene and TSC22d1iso3, thus producing misleading results. This quantitative evaluation may be used to better characterize the role of GILZ and L-GILZ in mice and may be translated to humans.

GILZ as a Mediator of the Anti-Inflammatory Effects of Glucocorticoids

Glucocorticoid-induced leucine zipper (GILZ) is a dexamethasone-inducible gene that mediates glucocorticoid (GC) actions in a variety of cell types, including many cells of immune system. In particular, GILZ can control T cell activities, such as activation and differentiation, mainly through its ability to homo- and hetero-dimerize with partner proteins, such as NF-κB, Ras, and C/EBP. These protein-protein interactions control the regulation of pro-inflammatory target genes. A number of in vitro and in vivo studies using mouse models of inflammatory diseases demonstrate an anti-inflammatory role for GILZ. Here, authors summarize the studies that make GILZ eligible as an anti-inflammatory protein through which GCs can act. These findings permit the future development of pharmacological tools that mimic the therapeutic effects of GCs while avoiding the detrimental ones.

Circulating conventional and plasmacytoid dendritic cell subsets display distinct kinetics during in vivo repeated allergen skin challenges in atopic subjects

Upon allergen challenge, DC subsets are recruited to target sites under the influence of chemotactic agents; however, details pertinent to their trafficking remain largely unknown. We investigated the kinetic profiles of blood and skin-infiltrating DC subsets in twelve atopic subjects receiving six weekly intradermal allergen and diluent injections. The role of activin-A, a cytokine induced in allergic and tissue repair processes, on the chemotactic profiles of DC subsets was also examined. Plasmacytoid (pDCs) and conventional DCs (cDCs) were evaluated at various time-points in the blood and skin. In situ activin-A expression was assessed in the skin and its effects on chemokine receptor expression of isolated cDCs were investigated. Blood pDCs were reduced 1 h after challenge, while cDCs decreased gradually within 24 h. Skin cDCs increased significantly 24 h after the first challenge, inversely correlating with blood cDCs. Activin-A in the skin increased 24 h after the first allergen challenge and correlated with infiltrating cDCs. Activin-A increased the CCR10/CCR4 expression ratio in cultured human cDCs. DC subsets demonstrate distinct kinetic profiles in the blood and skin especially during acute allergic inflammation, pointing to disparate roles depending on each phase of the inflammatory response. The effects of activin-A on modulating the chemotactic profile of cDCs suggest it may be a plausible therapeutic target for allergic diseases.