Interleukin 21 Drives a Hypermetabolic State and CD4+ T-Cell-Associated Pathogenicity in Chronic Intestinal Inflammation

BACKGROUND & AIMS

Incapacitated regulatory T cells (Tregs) contribute to immune-mediated diseases. Inflammatory Tregs are evident during human inflammatory bowel disease; however, mechanisms driving the development of these cells and their function are not well understood. Therefore, we investigated the role of cellular metabolism in Tregs relevant to gut homeostasis.

METHODS

Using human Tregs, we performed mitochondrial ultrastructural studies via electron microscopy and confocal imaging, biochemical and protein analyses using proximity ligation assay, immunoblotting, mass cytometry and fluorescence-activated cell sorting, metabolomics, gene expression analysis, and real-time metabolic profiling utilizing the Seahorse XF analyzer. We used a Crohn's disease single-cell RNA sequencing dataset to infer the therapeutic relevance of targeting metabolic pathways in inflammatory Tregs. We examined the superior functionality of genetically modified Tregs in CD4+ T-cell-induced murine colitis models.

RESULTS

Mitochondria-endoplasmic reticulum appositions, known to mediate pyruvate entry into mitochondria via voltage-dependent anion channel 1 (VDAC1), are abundant in Tregs. VDAC1 inhibition perturbed pyruvate metabolism, eliciting sensitization to other inflammatory signals reversible by membrane-permeable methyl pyruvate supplementation. Notably, interleukin (IL) 21 diminished mitochondria-endoplasmic reticulum appositions, resulting in enhanced enzymatic function of glycogen synthase kinase 3 β, a putative negative regulator of VDAC1, and a hypermetabolic state that amplified Treg inflammatory response. Methyl pyruvate and glycogen synthase kinase 3 β pharmacologic inhibitor (LY2090314) reversed IL21-induced metabolic rewiring and inflammatory state. Moreover, IL21-induced metabolic genes in Tregs in vitro were enriched in human Crohn's disease intestinal Tregs. Adoptively transferred Il21r-/- Tregs efficiently rescued murine colitis in contrast to wild-type Tregs.

CONCLUSIONS

IL21 triggers metabolic dysfunction associated with Treg inflammatory response. Inhibiting IL21-induced metabolism in Tregs may mitigate CD4+ T-cell-driven chronic intestinal inflammation.

The FOXP3+ Pro-Inflammatory T Cell: A Potential Therapeutic Target in Crohn's Disease

BACKGROUND & AIMS

The incidence of Crohn's disease (CD) continues to increase worldwide. The contribution of CD4+ cell populations remains to be elucidated. We aimed to provide an in-depth transcriptional assessment of CD4+ T cells driving chronic inflammation in CD.

METHODS

We performed single-cell RNA-sequencing in CD4+ T cells isolated from ileal biopsies of patients with CD compared with healthy individuals. Cells underwent clustering analysis, followed by analysis of gene signaling networks. We overlapped our differentially expressed genes with publicly available microarray data sets and performed functional in vitro studies, including an in vitro suppression assay and organoid systems, to model gene expression changes observed in CD regulatory T (Treg) cells and to test predicted therapeutics.

RESULTS

We identified 5 distinct FOXP3+ regulatory Treg subpopulations. Tregs isolated from healthy controls represent the origin of pseudotemporal development into inflammation-associated subtypes. These proinflammatory Tregs displayed a unique responsiveness to tumor necrosis factor-α signaling with impaired suppressive activity in vitro and an elevated cytokine response in an organoid coculture system. As predicted in silico, the histone deacetylase inhibitor vorinostat normalized gene expression patterns, rescuing the suppressive function of FOXP3+ cells in vitro.

CONCLUSIONS

We identified a novel, proinflammatory FOXP3+ T cell subpopulation in patients with CD and developed a pipeline to specifically target these cells using the US Food and Drug Administration-approved drug vorinostat.

Treg donation of sIL-6R to promote intestinal integrity and repair

IBD affects roughly 1.6 million US adults, with its prevalence increasing since the late 1990s. Characterized by unchecked intestinal inflammation, multiple proinflammatory cytokines including IL6 have been implicated as critical factors in this pathology. It has been established that EZH2 is a gene involved in the production of specific histone methyltransferase enzymes, as well as in the differentiation of Treg cells. The association between the Treg master transcription factor, Foxp3 and EZH2 results in the suppressive function of Tregs, with our previous work revealing impairment of this interaction under the influence of IL6 signaling in an inflamed intestinal setting. We investigated this further in a murine preventative T cell transfer model of colitis that involved injecting donor Treg cells that lacked IL6Ra, into immunocompromised mice. Histological scoring of the mice receiving the IL6Rko Tregs revealed a resolved inflammatory milieu and flow cytometric analysis of cells isolated from the spleens and MLNs showed increased Foxp3+ expression when compared to mice that received WT Tregs. Foxp3IL6Rako mice were subjected to a DSS model of colitis to further characterize the absence of the IL6R on Treg function in the intestinal milieu. Exacerbated signs of colitis were observed through histology and colon shortening of the conditional knockout mice when compared to their WT counterparts. We postulate that Tregs could be acting as a donor of sILR to promote intestinal integrity and healing. Further experiments will be conducted to define a role for the IL6R in the development of Foxp3+ cells, along with outlining the instrumental process of sIL6R donation in the intestinal milieu.

Supported by Mayo Clinic Graduate School for Biomedical Sciences

BMI1 maintains the Treg epigenomic landscape to prevent inflammatory bowel disease

FOXP3+ Tregs are expanded within the inflamed intestine of human Crohn's disease, yet FOXP3-mediated gene repression within these cells is lost. The polycomb repressive complexes play a role in FOXP3 target gene regulation, but deeper mechanistic insight is incomplete. We have now specifically identified the polycomb-repressive complex 1 (PRC1) family member, BMI1 in the regulation of a proinflammatory enhancer network in both human and murine Tregs. Using human Tregs and lamina propria T cells, we inferred PRC1 to regulate Crohn's associated gene networks through assays of chromatin accessibility. Conditional deletion of BMI1 in murine FOXP3+ cells led to systemic inflammation. BMI1-deficient Tregs beared a TH1/TH17-like phenotype as assessed by assays of genome wide transcription, chromatin accessibility and proteomic techniques. Finally, BMI1 mutant FOXP3+ cells did not suppress colitis in the adoptive transfer model of human inflammatory bowel disease. We propose that BMI1 plays an important role in enforcing Treg identity in vitro and in vivo. Loss of Treg identity via genetic or transient BMI1 depletion perturbs the epigenome and converts Tregs into Th1/Th17-like proinflammatory cells, a transition relevant to human Crohn's disease associated CD4+ T cells.

The Role of Histone Methyltransferases and Long Non-coding RNAs in the Regulation of T Cell Fate Decisions

T cell lineage decisions are critical for the development of proper immune responses to pathogens as well as important for the resolution of inflammatory responses. This differentiation process relies on a combination of intrinsic and extrinsic factors converging upon epigenetic regulation of transcriptional networks relevant to specific T cell lineages. As these biochemical modifications represent therapeutic opportunities in cancer biology and autoimmunity, implications of writers and readers of epigenetic marks to immune cell differentiation and function are highly relevant. Given the ready adoption of histone methyltransferase inhibitors in the clinic, we focus this review on the role of three histone modifying complexes: PRC-1, PRC-2, and G9A in modulating T cell fate decisions. Furthermore, we explore the role of long non-coding RNAs in regulating these processes, and discuss recent advances and challenges of implementing epigenetic therapies into clinical practice.

The Role of the Histone Methyltransferase Enhancer of Zeste Homolog 2 (EZH2) in the Pathobiological Mechanisms Underlying Inflammatory Bowel Disease (IBD)

Regulatory T (Treg) cells expressing the transcription factor FOXP3 play a pivotal role in maintaining immunologic self-tolerance. We and others have shown previously that EZH2 is recruited to the FOXP3 promoter and its targets in Treg cells. To further address the role for EZH2 in Treg cellular function, we have now generated mice that lack EZH2 specifically in Treg cells (EZH2^Δ/ΔFOXP3⁺). We find that EZH2 deficiency in FOXP3⁺ T cells results in lethal multiorgan autoimmunity. We further demonstrate that EZH2^Δ/ΔFOXP3⁺ T cells lack a regulatory phenotype in vitro and secrete proinflammatory cytokines. Of special interest, EZH2^Δ/ΔFOXP3⁺ mice develop spontaneous inflammatory bowel disease. Guided by these results, we assessed the FOXP3 and EZH2 gene networks by RNA sequencing in isolated intestinal CD4⁺ T cells from patients with Crohn's disease. Gene network analysis demonstrates that these CD4⁺ T cells display a Th1/Th17-like phenotype with an enrichment of gene targets shared by FOXP3 and EZH2. Combined, these results suggest that the inflammatory milieu found in Crohn's disease could lead to or result from deregulation of FOXP3/EZH2-enforced T cell gene networks contributing to the underlying intestinal inflammation.

Discovery of localized regions of excess 10-TeV cosmic rays

The 7 year data set of the Milagro TeV observatory contains 2.2 x 10(11) events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of approximately 10 degrees has been found in two localized regions of unknown origin with greater than 12sigma significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6sigma, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at approximately 10 TeV. Potential causes of these excesses are explored, but no compelling explanations are found.

Evidence for TeV gamma-ray emission from a region of the galactic plane

Gamma-ray emission from a narrow band at the galactic equator has previously been detected up to 30 GeV. We report evidence for a TeV gamma-ray signal from a region of the galactic plane by Milagro, a large-field-of-view water Cherenkov detector for extensive air showers. An excess with a significance of 4.5 standard deviations has been observed from the region of galactic longitude l E (40 degrees, 100 degrees) and latitude /b/ < 5 degrees. Under the assumption of a simple power law spectrum, with no cutoff in the EGRET-Milagro energy range, the measured integral flux is phi gamma(>3.5 TeV) = (6.4 +/- 1.4 +/- 2.1) x 10(-11) cm(-2) s(-1) sr(-1). This flux is consistent with an extrapolation of the EGRET spectrum between 1 and 30 GeV in this galactic region.

Different Molecular Mechanisms of Vitamin D3 Receptor Antagonists

Two structurally different antagonists of the nuclear hormone 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], the 25-carboxylic ester ZK159222 and the 26,23-lactone TEI-9647, have recently been described. In this study, the molecular mechanisms and the efficacy of both antagonists were compared. ZK159222 showed similar potency and sensitivity to 1alpha,25(OH)(2)D(3) in ligand-dependent gel shift assays using the vitamin D receptor (VDR), the retinoid X receptor, and specific DNA binding sites, whereas TEI-9647 displayed reduced potency and >10-fold lower sensitivity in this assay system. Limited protease digestion and gel shift clipping assays showed that the two antagonists stabilized individual patterns of VDR conformations. Both antagonists prevented the interaction of the VDR with coactivator proteins, as demonstrated by GST-pull-down and supershift assays; like the natural hormone, however, they were able to induce a dissociation of corepressor proteins. Interestingly, ZK159222 demonstrated functional antagonism in reporter gene assays both in HeLa and MCF-7 cells, whereas TEI-9647 functioned as a less sensitive antagonist only in MCF-7 cells. In conclusion, the two 1alpha,25(OH)(2)D(3) analogs act in part via different molecular mechanisms, which allows us to speculate that ZK159222 is a more complete antagonist and TEI-9647 a more selective antagonist.

Sleep increase after immobilization stress: role of the noradrenergic locus coeruleus system in the rat

In a preliminary study we showed that the sleep rebound occurring after sleep deprivation is decreased in rats treated with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), a neurotoxic agent specific for the noradrenergic cells of the locus coeruleus (LC). Sleep deprivation methods not only involve sleep loss, but also stress, which per se may induce an increase in sleep duration. Extensive research showed that the locus coeruleus is involved in stress. To evaluate the participation of LC in this mechanism, the effect of DSP-4 treatment was studied on sleep duration following a short intense stress in the absence of sleep loss. The results showed that the augmentation of sleep after 1 h of immobilization stress is lower in DSP-4-treated rats (slow-wave sleep duration, -24%; paradoxical sleep duration, -52%). These findings suggest that the increase in sleep induced by such a stressor is mediated, at least in part, by the noradrenergic LC.

Physiological changes in antioxidant defences in fetal and neonatal rat liver

This study describes the physiological changes in the activities of the hepatic antioxidant enzymes superoxide dismutase isoenzymes (Cu/Zn-and Mn-superoxide dismutase) and catalase, in the glutathione content and in the lipid peroxidation levels in fetal (20 and 21 days of gestation) and neonatal rat liver (Days 1, 8, 15, and 22 post partum). The catalase and superoxide dismutase activities decreased before birth and increased after birth. The oxidized:reduced glutathione (GSSG:GSH) ratio declined before birth, but it increased between Days 1 and 15 post partum and then remained stable. Finally, newborn rat liver from the 1st day of life shows the highest susceptibility to lipid peroxidation. These results suggest that the changes in antioxidant defences could be related mainly to the beginning of diet intake after birth, which entails a higher hepatic metabolism rate, as well as a higher oxygen consumption.

Acquired immunodeficiency syndrome associated with Acanthamoeba infection and other opportunistic organisms

A 29-year-old Haitian man with acquired immunodeficiency syndrome presented with nasal obstruction and epistaxis. A computed tomogram of the head showed thickened nasal and paranasal sinus mucosa. A biopsy specimen of the turbinate disclosed inflammatory tissue containing amoebic trophozoites. The patient was empirically treated with rifampin and ketoconazole. He died four months after biopsy of other complications of acquired immunodeficiency syndrome. At autopsy, the amoebic infection was found only in the paranasal sinuses, a calf nodule, and in an intradermal abscess in the left leg. Pneumocystitis carinii pneumonia, Mycobacterium avium-cellulare in the liver and retroperitoneal lymph nodes, cytomegalovirus infection of the adrenal glands, and Kaposi's sarcoma in the spleen were additionally present. The organism was cultured and studied by electron microscopy, dark-field microscopy, and immunofluorescence.