Makrofág polarizációs szignálok által indukált transzkripciós és poszt-transzkripciós szintű represszió mechanizmusai

A komplex molekuláris mikrokörnyezet szigorúan szabályozza a mkrofágok fenotípusos és funkcinális sajátosságait különböző fiziológiás és patológiás körülmények között. A makrofágok stimulációja különböző polarizációs szignálokkal, köztük citokinekkel és patogén eredetű molekulákkal, a szignálok által aktivált transzkripciós faktorokon keresztül a szignálokra specifikus génexpressziós program bekapcsolásához vezet. Szisztematikus teljes genom szintű analízis segítségével kimutattuk, az alternatív makrofág polarizációs szignálok közé tartozó IL-4 egy nagy géncsoport kifejeződését gátolja a transzkripció szintjén. Az IL-4 által aktivált STAT6 transzkripciós faktor kötődik a gátolt génekhez tartozó ehanszerekhez. Ezeken a helyeken a STAT6 kötődés együtt jár a csökkent kromatin nyitottsággal, kisebb LDTF, p300 és RNS Polimeráz II kötődéssel, valamint alacsonyabb eRNS kifejeződéssel. Ezek az eredmények azt mutatják, hogy az IL-4 által aktivált STAT6 transzkripciós faktor képes represszorként működni a makrofágokban. Továbbá megfigyeltük, hogy az IL-4/STAT6 szignálútvonal által kiváltott represszió képes csökkenteni a makrofágok gyulladásos válaszkészségét, köztük az NLRP3 inflammaszóma aktivációt, az IL-1βtermelődést és a piroptózist. Összességében ezek az eredmények felvetik egy kétirányú kölcsönhatás lehetőségét az alternatív makrofág polarizáció és a gyulladásos szignálok között, amely jelentősen befolyásolhatja a makrofágok különböző mikrobiális, stressz és sérülés eredetű szignálokkal szembeni érzékenységét és válaszkészségét. A miRNS-ek által kiváltott poszt-transzkripciós gátlás szintén hozzájárul a makrofágok funkciójának szabályozásához. A munkánk során azonosítottuk, a miR-342-3p-nek és EVL gazdagénjének IL-4/STAT6 szignálútvonal által kiváltott közvetlen indukcióját. Érdekes módon a miR-342-3p csökkenti a makrofág életképességet közvetlenül szabályozva egy a Bcl2l1 gént is magában foglaló antiapoptotikus génhálózatot. Ezek az eredmények azt mutatják, hogy IL-4/STAT6 szignálútvonal által indukált miR-342-3p részt vesz az IL-4 által kiváltott sejtosztódás szabályozásában a folyamat negatív regulátoraként. Végül feltérképeztük a gyulladásos miRNS-ek, köztük a miR-155, miR-147 és miR-223 transzkripciós szabályozását egy integrált új-generációs szekvenálás alapú megközelítés alkalmazásával. Kimutattuk, hogy a miR-155 kifejeződésének LPS által kiváltott aktiválása a pri-miR-155 transzkripciós starthelye és távoli enhenszerei közötti intenzív kommunikáción alapszik, amely együtt jár a miR-155-öt kódoló genomi régió gyulladásos szignál által kiváltott átrendeződésével. The complex molecular microenvironment tightly determines the phenotypic and functional features of macrophages in different physiological and pathological conditions. The macrophage exposure to different polarization signals including cytokines and pathogen-derived molecules leads to the activation of signal specific gene expression program via SRTFs. Our systematic genome-wide analysis revealed that the alternative macrophage polarization signal IL-4 represses large gene set at the transcriptional level. IL-4-activated STAT6 binds the repressed genes-linked distal regulatory elements. The STAT6-binding was associated with reduced chromatin openess, LDTF, p300 and RNAPII binding as well as decreased eRNA expression. These results suggest the IL-4-activated STAT6 transcriptional factor can act as a transcriptional repressor in macrophages. In addition, we found that the IL-4/STAT6 signaling pathway-mediated transcriptional repression diminishes the inflammatory responsiveness of macrophages including NLRP3 inflammasome activation, IL-1β production and pyroptosis. Taken together, these results suggest that complex bidirectional interactions exist between alternative macrophage polarization and inflammatory signals that influence the responsiveness and sensitivity of macrophages toward microbial-, stress-, and damage-associated endogenous signals. The miRNA-mediated post-transcriptional repression also contributes in the regulation of macrophage function. Here, we identified that miR-342-3p and their host gene EVL are directly induced in human and mice by IL-4/STAT6 signaling pathway. Interestingly, miR-342-3p can reduce macrophage survival via direct targeting of anti-apoptotic gene pathway including Bcl2l1. These results suggest that IL-4/STAT6 signaling pathway-induced miR-342-3p potentially participate in the negative feed-back regulation of IL-4-mediated macrophage proliferation. Finally, we characterized the transcriptional regulation of the inflammation responsive miRNome including miR-155, miR-147 and miR-223 using an integrated NGS-based approach. Here we show that LPS-dependent transcriptional induction of miR-155 expression is based on an intensive communication between the distal anhancers and the pri-miR-155-linked TSS and associated with the reorganization of the pri-miR-155-coding genomic locus.d

Epigenomic regulation of macrophage polarization: Where do the nuclear receptors belong?

Our laboratory has a long-standing research interest in understanding how lipid-activated transcription factors, nuclear hormone receptors, contribute to dendritic cell and macrophage gene expression regulation, subtype specification, and responses to a changing extra and intracellular milieu. This journey in the last more than two decades took us from identifying target genes for various RXR heterodimers to systematically mapping nuclear receptor-mediated pathways in dendritic cells to identifying hierarchies of transcription factors in alternative polarization in macrophages to broaden the role of nuclear receptors beyond strictly ligand-regulated gene expression. We detail here the milestones of the road traveled and draw conclusions regarding the unexpectedly broad role of nuclear hormone receptors as epigenomic components of dendritic cell and macrophage gene regulation as we are getting ready for the next challenges

The IL-4/STAT6/PPARgamma signaling axis is driving the expansion of the RXR heterodimer cistrome, providing complex ligand responsiveness in macrophages

Retinoid X receptor (RXR) is an obligate heterodimeric partner of several nuclear receptors (NRs), and as such a central component of NR signaling regulating the immune and metabolic phenotype of macrophages. Importantly, the binding motifs of RXR heterodimers are enriched in the tissue-selective open chromatin regions of resident macrophages, suggesting roles in subtype specification. Recent genome-wide studies revealed that RXR binds to thousands of sites in the genome, but the mechanistic details how the cistrome is established and serves ligand-induced transcriptional activity remained elusive. Here we show that IL-4-mediated macrophage plasticity results in a greatly extended RXR cistrome via both direct and indirect actions of the transcription factor STAT6. Activation of STAT6 leads to chromatin remodeling and RXR recruitment to de novo enhancers. In addition, STAT6 triggers a secondary transcription factor wave, including PPARgamma. PPARgamma appears to be indispensable for the development of RXR-bound de novo enhancers, whose activities can be modulated by the ligands of the PPARgamma:RXR heterodimer conferring ligand selective cellular responses. Collectively, these data reveal the mechanisms leading to the dynamic extension of the RXR cistrome and identify the lipid-sensing enhancer sets responsible for the appearance of ligand-preferred gene signatures in alternatively polarized macrophages

Recent Progress in the Diagnosis and Management of Type 2 Diabetes Mellitus in the Era of COVID-19 and Single Cell Multi-Omics Technologies

Type 2 diabetes mellitus (T2DM) is one of the world’s leading causes of death and life-threatening conditions. Therefore, we review the complex vicious circle of causes responsible for T2DM and risk factors such as the western diet, obesity, genetic predisposition, environmental factors, and SARS-CoV-2 infection. The prevalence and economic burden of T2DM on societal and healthcare systems are dissected. Recent progress on the diagnosis and clinical management of T2DM, including both non-pharmacological and latest pharmacological treatment regimens, are summarized. The treatment of T2DM is becoming more complex as new medications are approved. This review is focused on the non-insulin treatments of T2DM to reach optimal therapy beyond glycemic management. We review experimental and clinical findings of SARS-CoV-2 risks that are attributable to T2DM patients. Finally, we shed light on the recent single-cell-based technologies and multi-omics approaches that have reached breakthroughs in the understanding of the pathomechanism of T2DM

The Transcription Factor STAT6 Mediates Direct Repression of Inflammatory Enhancers and Limits Activation of Alternatively Polarized Macrophages

The molecular basis of signal-dependent transcriptional activation has been extensively studied in macrophage polarization, but our understanding remains limited regarding the molecular determinants of repression. Here we show that IL-4-activated STAT6 transcription factor is required for the direct transcriptional repression of a large number of genes during in vitro and in vivo alternative macrophage polarization. Repression results in decreased lineage-determining transcription factor, p300, and RNA polymerase II binding followed by reduced enhancer RNA expression, H3K27 acetylation, and chromatin accessibility. The repressor function of STAT6 is HDAC3 dependent on a subset of IL-4-repressed genes. In addition, STAT6-repressed enhancers show extensive overlap with the NF-kappaB p65 cistrome and exhibit decreased responsiveness to lipopolysaccharide after IL-4 stimulus on a subset of genes. As a consequence, macrophages exhibit diminished inflammasome activation, decreased IL-1beta production, and pyroptosis. Thus, the IL-4-STAT6 signaling pathway establishes an alternative polarization-specific epigenenomic signature resulting in dampened macrophage responsiveness to inflammatory stimuli

Transglutaminase 2 associated with PI3K and PTEN in a membrane-bound signalosome platform blunts cell death

Atypically expressed transglutaminase 2 (TG2) has been identified as a poor prognostic factor in a variety of cancers. In this study, we evaluated the contribution of TG2 to the prolonged cell survival of differentiated acute promyelocytic leukaemia (APL) cells in response to the standard treatment with combined retinoic acid (ATRA) and arsenic trioxide (ATO). We report that one advantage of ATRA + ATO treatment compared to ATRA alone diminishes the amount of activated and non-activated CD11b/CD18 and CD11c/CD18 cell surface integrin receptors. These changes suppress ATRA-induced TG2 docking on the cytosolic part of CD18 β2-integrin subunits and reduce cell survival. In addition, TG2 overexpresses and hyperactivates the phosphatidylinositol-3-kinase (PI3K), phospho-AKT S473, and phospho-mTOR S2481 signalling axis. mTORC2 acts as a functional switch between cell survival and death by promoting the full activation of AKT. We show that TG2 presumably triggers the formation of a signalosome platform, hyperactivates downstream mTORC2-AKT signalling, which in turn phosphorylates and inhibits the activity of FOXO3, a key pro-apoptotic transcription factor. In contrast, the absence of TG2 restores basic phospho-mTOR S2481, phospho-AKT S473, PI3K, and PTEN expression and activity, thereby sensitising APL cells to ATO-induced cell death. We conclude, that atypically expressed TG2 may serve as a hub, facilitating signal transduction via signalosome formation by the CD18 subunit with both PI3K hyperactivation and PTEN inactivation through the PI3K-PTEN cycle in ATRA-treated APL cells

Reduced miR-26b Expression in Megakaryocytes and Platelets Contributes to Elevated Level of Platelet Activation Status in Sepsis

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Dynamic transcriptional control of macrophage miRNA signature via inflammation responsive enhancers revealed using a combination of next generation sequencing-based approaches

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