The Glucocorticoid Receptor Regulates the ANGPTL4 Gene in a CTCF-Mediated Chromatin Context in Human Hepatic Cells

Acetylation-induced proteasomal degradation of the activated glucocorticoid receptor limits hormonal signaling

Glucocorticoid (GC) signaling is essential for mounting a stress response, however, chronic stress or prolonged GC therapy downregulates the GC receptor (GR), leading to GC resistance. Regulatory mechanisms that refine this equilibrium are not well understood. Here, we identify seven lysine acetylation sites in the amino terminal domain of GR, with lysine 154 (Lys154) in the AF-1 region being the dominant acetyl-acceptor. GR-Lys154 acetylation is mediated by p300/CBP in the nucleus in an agonist-dependent manner and correlates with transcriptional activity. Deacetylation by NAD+-dependent SIRT1 facilitates dynamic regulation of this mark. Notably, agonist-binding to both wild-type GR and an acetylation-deficient mutant elicits similar short-term target gene expression. In contrast, upon extended treatment, the polyubiquitination of the acetylation-deficient GR mutant is impaired resulting in higher protein stability, increased chromatin association and prolonged transactivation. Taken together, reversible acetylation fine-tunes duration of the GC response by regulating proteasomal degradation of activated GR.

ANGPTL4 is a potential driver of HCV-induced peripheral insulin resistance

Chronic hepatitis C (CHC) is associated with the development of metabolic disorders, including both hepatic and extra-hepatic insulin resistance (IR). Here, we aimed at identifying liver-derived factor(s) potentially inducing peripheral IR and uncovering the mechanisms whereby HCV can regulate the action of these factors. We found ANGPTL4 (Angiopoietin Like 4) mRNA expression levels to positively correlate with HCV RNA (r = 0.46, p < 0.03) and HOMA-IR score (r = 0.51, p = 0.01) in liver biopsies of lean CHC patients. Moreover, we observed an upregulation of ANGPTL4 expression in two models recapitulating HCV-induced peripheral IR, i.e. mice expressing core protein of HCV genotype 3a (HCV-3a core) in hepatocytes and hepatoma cells transduced with HCV-3a core. Treatment of differentiated myocytes with recombinant ANGPTL4 reduced insulin-induced Akt-Ser473 phosphorylation. In contrast, conditioned medium from ANGPTL4-KO hepatoma cells prevented muscle cells from HCV-3a core induced IR. Treatment of HCV-3a core expressing HepG2 cells with PPARγ antagonist resulted in a decrease of HCV-core induced ANGPTL4 upregulation. Together, our data identified ANGPTL4 as a potential driver of HCV-induced IR and may provide working hypotheses aimed at understanding the pathogenesis of IR in the setting of other chronic liver disorders.

Network analysis between neuron dysfunction and neuroimmune response based on neural single-cell transcriptome of COVID-19 patients

Despite global vaccination efforts, COVID-19 breakthrough infections caused by variant virus continue to occur frequently, long-term sequelae of COVID-19 infection like neuronal dysfunction emerge as a noteworthy issue. Neuroimmune disorder induced by Inflammatory factor storm was considered as a possible reason, however, little was known about the functional factors affecting neuroimmune response to this virus. Here, using medial prefrontal cortex single cell data of COVID-19 patients, expression pattern analysis indicated that some immune-related pathway genes expressed specifically, including genes associated with T cell receptor, TNF signaling in microglia and Cytokine-cytokine receptor interaction and HIF-1 signaling pathway genes in astrocytes. Besides the well-known immune-related cell type microglia, we also observed immune-related factors like IL17D, TNFRSF1A and TLR4 expressed in Astrocytes. Based on the ligand-receptor relationship of immune-related factors, crosstalk landscape among cell clusters were analyzed. The findings indicated that astrocytes collaborated with microglia and affect excitatory neurons, participating in the process of immune response and neuronal dysfunction. Moreover, subset of astrocytes specific immune factors (hinged neuroimmune genes) were proved to correlate with Covid-19 infection and ventilator-associated pneumonia using multi-tissue RNA-seq and scRNA-seq data. Function characterization clarified that hinged neuroimmune genes were involved in activation of inflammation and hypoxia signaling pathways, which could lead to hyper-responses related neurological sequelae. Finally, a risk model was constructed and testified in RNA-seq and scRNA data of peripheral blood.

α1-Antitrypsin Binds to the Glucocorticoid Receptor with Anti-Inflammatory and Antimycobacterial Significance in Macrophages

α1-Antitrypsin (AAT), a serine protease inhibitor, is the third most abundant protein in plasma. Although the best-known function of AAT is irreversible inhibition of elastase, AAT is an acute-phase reactant and is increasingly recognized to have a panoply of other functions, including as an anti-inflammatory mediator and a host-protective molecule against various pathogens. Although a canonical receptor for AAT has not been identified, AAT can be internalized into the cytoplasm and is known to affect gene regulation. Because AAT has anti-inflammatory properties, we examined whether AAT binds the cytoplasmic glucocorticoid receptor (GR) in human macrophages. We report the finding that AAT binds to GR using several approaches, including coimmunoprecipitation, mass spectrometry, and microscale thermophoresis. We also performed in silico molecular modeling and found that binding between AAT and GR has a plausible stereochemical basis. The significance of this interaction in macrophages is evinced by AAT inhibition of LPS-induced NF-κB activation and IL-8 production as well as AAT induction of angiopoietin-like 4 protein, which are, in part, dependent on GR. Furthermore, this AAT-GR interaction contributes to a host-protective role against mycobacteria in macrophages. In summary, this study identifies a new mechanism for the gene regulation, anti-inflammatory, and host-defense properties of AAT.

Activation function 1 of progesterone receptor is required for progesterone antagonism of oestrogen action in the uterus

BACKGROUND

Progesterone receptor (PGR) is a master regulator of uterine function through antagonistic and synergistic interplays with oestrogen receptors. PGR action is primarily mediated by activation functions AF1 and AF2, but their physiological significance is unknown.

RESULTS

We report the first study of AF1 function in mice. The AF1 mutant mice are infertile with impaired implantation and decidualization. This is associated with a delay in the cessation of epithelial proliferation and in the initiation of stromal proliferation at preimplantation. Despite tissue selective effect on PGR target genes, AF1 mutations caused global loss of the antioestrogenic activity of progesterone in both pregnant and ovariectomized models. Importantly, the study provides evidence that PGR can exert an antioestrogenic effect by genomic inhibition of Esr1 and Greb1 expression. ChIP-Seq data mining reveals intermingled PGR and ESR1 binding on Esr1 and Greb1 gene enhancers. Chromatin conformation analysis shows reduced interactions in these genes' loci in the mutant, coinciding with their upregulations.

CONCLUSION

AF1 mediates genomic inhibition of ESR1 action globally whilst it also has tissue-selective effect on PGR target genes.

H19/let-7 axis mediates caffeine exposure during pregnancy induced adrenal dysfunction and its multi-generation inheritance

Previously, we systemically confirmed that prenatal caffeine exposure (PCE) could cause intrauterine growth retardation (IUGR) and adrenal steroid synthesis dysfunction in offspring rats. However, the multi-generation inheritance of adrenal dysfunction and its epigenetic mechanism has not been reported. In this study, the PCE rat model was established, part of the pregnant rats were executed on gestational day 20, while the others were delivered normally and the fetal rats were reared into adulthood. The PCE female rats of filial generation 1 (F1) were mated with wild males to produce F2 offspring, and the same way to produce F3 offspring. All the adult female rats of three generations were sacrificed for the related detection. Results showed that PCE could decrease fetal weight, increase IUGR rate, and elevate serum corticosterone level. Meanwhile, the expression of fetal adrenal GR, DNMT3a/3b, miRNA let-7c increased while those of CTCF, H19, and StAR decreased, and the total methylation rate of the H19 promoter region was enhanced. We used SW-13 cells to clarify the molecular mechanism and found that cortisol-induced in vitro changes of these indexes were consistent with those in vivo. We confirmed that high level of cortisol through activating GR, on the one hand, promoted let-7 expression and inhibited StAR expression; on the other hand, caused high methylation and low expression of H19 by down-regulating CTCF and up-regulating DNMT3a/3b, then enhanced let-7 inhibitory effect on StAR by "molecular sponge" effect. Finally, in vivo experiments showed that the adrenal steroid synthesis function and H19/let-7 axis presented the glucocorticoid-dependent changes in the adult female F1, F2, and F3. In conclusion, PCE can cause female adrenal dysfunction with matrilineal multi-generation inheritance, which is related to the programming alteration of the H19/let-7 axis. This study provides a novel perspective to explain the multi-generation inheritance of fetal-originated disease in IUGR offspring.

Glucocorticoids regulate AKR1D1 activity in human liver in vitro and in vivo

Steroid 5β-reductase (AKR1D1) is highly expressed in human liver where it inactivates endogenous glucocorticoids and catalyses an important step in bile acid synthesis. Endogenous and synthetic glucocorticoids are potent regulators of metabolic phenotype and play a crucial role in hepatic glucose metabolism. However, the potential of synthetic glucocorticoids to be metabolised by AKR1D1 as well as to regulate its expression and activity has not been investigated. The impact of glucocorticoids on AKR1D1 activity was assessed in human liver HepG2 and Huh7 cells; AKR1D1 expression was assessed by qPCR and Western blotting. Genetic manipulation of AKR1D1 expression was conducted in HepG2 and Huh7 cells and metabolic assessments were made using qPCR. Urinary steroid metabolite profiling in healthy volunteers was performed pre- and post-dexamethasone treatment, using gas chromatography-mass spectrometry. AKR1D1 metabolised endogenous cortisol, but cleared prednisolone and dexamethasone less efficiently. In vitro and in vivo, dexamethasone decreased AKR1D1 expression and activity, further limiting glucocorticoid clearance and augmenting action. Dexamethasone enhanced gluconeogenic and glycogen synthesis gene expression in liver cell models and these changes were mirrored by genetic knockdown of AKR1D1 expression. The effects of AKR1D1 knockdown were mediated through multiple nuclear hormone receptors, including the glucocorticoid, pregnane X and farnesoid X receptors. Glucocorticoids down-regulate AKR1D1 expression and activity and thereby reduce glucocorticoid clearance. In addition, AKR1D1 down-regulation alters the activation of multiple nuclear hormone receptors to drive changes in gluconeogenic and glycogen synthesis gene expression profiles, which may exacerbate the adverse impact of exogenous glucocorticoids.

ANGPTL4 Promotes the Proliferation of Papillary Thyroid Cancer via AKT Pathway

Purpose

Although papillary thyroid carcinoma (PTC) is associated with a generally favorable prognosis, about 15% of patients present recurrence and distant metastasis in the next decade leading to death. Angiopoietin-like 4 (ANGPTL4) is secreted to circulation and belongs to the angiopoietin-like proteins. The expression of ANGPTL4 was increased in several solid tumor tissues compared to corresponding paracancerous tissues. ANGPTL4 was identified as pro-tumorigenic protein, including stimulating tumor cell growth, promoting tumor metastasis. However, the clinical significance and biological function of ANGPTL4 in PTC is still unclear. Hence, the purpose of this study was to evaluate the role of ANGPTL4 in PTC, investigating the possibility of whether ANGPTL4 could become a novel target for PTC therapy.

Methods

We investigated the expression level of ANGPTL4 and pAKT in PTC and paracancerous tissue by immunohistochemistry. We determined the effect of ANGPTL4 in PTC cell proliferation through cell counting kit-8 (CCK-8) and cell cycle by flow cytometry analysis. Furthermore, the correlation between ANGPTL4 expression levels and PTC cell proliferation from the TCGA data set was analyzed by GSEA. We explored the role of ANGPTL4 on the phosphorylation of AKT and proliferation in PTC cells via overexpression or knockdown assays and AKT inhibitor assay.

Results

In the present study, we found that ANGPTL4 was highly expressed in both protein and mRNA level in PTC compared with adjacent noncancerous tissues or benign nodule. ANGPTL4 expression increased according to thyroid tumor progression. ANGPTL4 level was positively correlated with the size of PTC. ANGPTL4 increased cell proliferation and decreased cell cycle arrest of PTC. Knockdown of ANGPTL4 inhibited the phosphorylation of AKT. ANGPTL4 regulated PTC cell proliferation through AKT signaling pathway.

Conclusion

Our findings suggested that ANGPTL4 was increased in PTC compared with adjacent noncancerous tissues, and ANGPTL4 increased cell proliferation and inhibited cell cycle arrest in PTC cells via promoting AKT phosphorylation. The study may provide fundamental information to suggest its suitability as a target for the treatment of PTC.

Endothelial cell-glucocorticoid receptor interactions and regulation of Wnt signaling

Vascular inflammation is present in many cardiovascular diseases, and exogenous glucocorticoids have traditionally been used as a therapy to suppress inflammation. However, recent data have shown that endogenous glucocorticoids, acting through the endothelial glucocorticoid receptor, act as negative regulators of inflammation. Here, we performed ChIP for the glucocorticoid receptor, followed by next-generation sequencing in mouse endothelial cells to investigate how the endothelial glucocorticoid receptor regulates vascular inflammation. We identified a role of the Wnt signaling pathway in this setting and show that loss of the endothelial glucocorticoid receptor results in upregulation of Wnt signaling both in vitro and in vivo using our validated mouse model. Furthermore, we demonstrate glucocorticoid receptor regulation of a key gene in the Wnt pathway, Frzb, via a glucocorticoid response element gleaned from our genomic data. These results suggest a role for endothelial Wnt signaling modulation in states of vascular inflammation.

MCF-7 as a Model for Functional Analysis of Breast Cancer Risk Variants

BACKGROUND

Breast cancer genetic predisposition is governed by more than 142 loci as revealed by genome-wide association studies (GWAS). The functional contribution of these risk loci to breast cancer remains unclear, and additional post-GWAS analyses are required.

METHODS

We identified active regulatory elements (enhancers, promoters, and chromatin organizing elements) by histone H3K27 acetylation and CTCF occupancy and determined the enrichment of risk variants at these sites. We compared these results with previously published data and for other cell lines, including human mammary epithelial cells, and related these data to gene expression.

RESULTS

In terms of mapping accuracy and resolution, our data augment previous annotations of the MCF-7 epigenome. After intersection with GWAS risk variants, we found 39 enhancers and 15 CTCF occupancy sites that, between them, overlapped 96 breast cancer credible risk variants at 42 loci. These risk enhancers likely regulate the expression of dozens of genes, which are enriched for GO categories, including estrogen and prolactin signaling.

CONCLUSIONS

Ten (of 142) breast cancer risk loci likely function via enhancers that are active in MCF-7 and are well suited to targeted manipulation in this system. In contrast, risk loci cannot be mapped to specific CTCF-binding sites, and the genes linked to risk CTCF sites did not show functional enrichment. The identity of risk enhancers and their associated genes suggests that some risk may function during later processes in cancer progression.

IMPACT

Here, we report how the ER⁺ cell line MCF-7 can be used to dissect risk mechanisms for breast cancer.

Tissue-specific epigenetics of atherosclerosis-related ANGPT and ANGPTL genes

Aim:

To understand tissue-specific regulation of angiopoietin/angiopoietin-like (ANGPT/ANGPTL) genes (especially the five genes embedded in introns of host genes) and their association with atherosclerosis.

Methods:

Transcription and epigenomic databases from various normal tissues were examined in the vicinity of ANGPT1, ANGPT2, ANGPTL1, ANGPTL2, ANGPTL3, ANGPTL4 and ANGPTL8.

Results:

We identified tissue-specific enhancer chromatin regions that are likely to regulate transcription of ANGPT/ANGPTL genes and were intragenic, intergenic or host gene-linked. In addition, we found atherosclerosis-linked differentially methylated regions associated with ANGPT2 and with sequences encoding miR-145, a microRNA that targets ANGPT2 mRNA in cancers.

Conclusion:

Our findings implicate enhancers as major contributors to tissue-specific expression of ANGPT/ANGPTL genes, which play critical roles in angiogenesis, atherosclerosis, cancer, and inflammatory and metabolic diseases.

Functional roles of CTCF in breast cancer

CTCF, Zinc-finger protein, has been identified as a multifunctional transcription factor that regulates gene expression through various mechanisms, including recruitment of other co-activators and binding to promoter regions of target genes. Furthermore, it has been proposed to be an insulator protein that contributes to the establishment of functional three-dimensional chromatin structures. It can disrupt transcription through blocking the connection between an enhancer and a promoter. Previous studies revealed that the onset of various diseases, including breast cancer, could be attributed to the aberrant expression of CTCF itself or one or more of its target genes. In this review, we will describe molecular dysfunction involving CTCF that induces tumorigenesis and summarize the functional roles of CTCF in breast cancer.