Reduced Treg suppressive function and HIF-1α expression in hypoxia
ABSTRACT: Recently, hypoxia via the transcription factor HIF-1a has been implicated to play an important role for the fate of the adaptive immune response by regulatory T cells (Treg) and T helper 17 cells (TH17) in the mouse model. However, the reports on the effect of HIF-1a are conflicting and so far no functional data in the human system are available. Therefore, we analyzed the effect of hypoxia and HIF-1a on Treg and TH17 in the human system. FACS, western blot and reporter assays clearly demonstrated that hypoxia does not up-regulate the level of HIF-1a in CD4+ T cells (THC) and microarray analysis revealed no change of the transcriptome comparing normoxia vs. hypoxia. Furthermore, we could show that HIF-1a is almost exclusively regulated via NF-kB and NFAT, whereas hydroxylation and subsequent degradation of HIF-1a had little to no effect. In addition, we showed that HIF-1a is essential for nTreg mediated suppression and for IL-17A secretion of TH17, but not for TH17 lineage commitment measured by RORγt expression. In conclusion, our results demonstrated that THC have a distinct regulation of HIF-1a protein levels, which was absolutely essential for Treg and TH17 function. 3 patients, 2 cell type, 2 treatments = 12 arrays
Project description:HIF-1a activates genes under hypoxia and was hypothesized to regulate bone regeneration. Surprisingly, HET HIF-1a fracture calluses are larger, stronger and stiffer than WT HIF-1a calluses due to decreased apoptosis. These data identify apoptosis inhibition as a means to enhance bone regeneration. Introduction: Bone regeneration subsequent to fracture involves the synergistic activation of multiple signaling pathways. Localized hypoxia following fracture activates hypoxia-inducible factor 1 alpha (HIF-1a) leading to increased expression of HIF-1 target genes. We therefore hypothesized that HIF-1a is a key regulator of bone regeneration Materials and Methods: Fixed femoral fractures were generated in mice with partial HIF-1a deficiency (HET HIF-1a) and wild type littermates (WT HIF-1a). Fracture calluses and intact contralateral femurs from post fracture day (PFD) 21 and 28 (N=5-10) were subjected to MicroCT evaluation and 4-point bending in order to assess morphometric and mechanical properties. Molecular analyses were carried out on PFD 7, 10 and 14 samples (N=3) to determine differential gene expression at both mRNA and protein levels. Finally, TUNEL staining was performed on PFD 14 samples (N=2) to elucidate differential apoptosis. Results: Surprisingly, fracture calluses from HET HIF-1a mice exhibit greater mineralization and are larger, stronger and stiffer. Microarray analyses focused on hypoxia-induced genes revealed differential expression (between genotypes) of several genes associated with the apoptotic pathway. Real-time PCR confirmed these results, demonstrating higher expression of pro-apoptotic PP2A and lower expression of anti-apoptotic BCL2 in WT HIF-1a calluses. Subsequent TUNEL staining demonstrates that WT HIF-1a calluses contain larger numbers of TUNEL positive chondrocytes and osteoblasts than HET HIF-1a calluses. Conclusions: We conclude that partial HIF-1a deficiency results in decreased chondrocytic and osteoblastic apoptosis; thereby allowing the development of larger, stiffer calluses and enhancing bone regeneration. Furthermore, apoptosis inhibition may be a promising target for developing new treatments to accelerate bone regeneration. Keywords: Bone, Fracture, Apoptosis, Hypoxia, Microarray Overall design: Unilateral femoral fractures were induced in WT HIF-1a and HET HIF-1a mice. Total RNA from fracture calluses corresponding to post fracture day (PFD) 7, 10 and 14 was analyzed. Comparisons were made between genotypes at each time point. Focused microarrays for hypoxia-induced and angiogenesis related genes were utilized.
Project description:HIF-1A and HIF-2A regulate both overlapping and unique target genes in response to hypoxia. In this dataset, we identify specific HIF-1A and HIF-2A target genes in glioblastoma cells. Overall design: 12 samples were analysed comprising 4 experimental conditions (normoxia scr, hypoxia scr, hypoxia siHIF1, hypoxia siHIF2) in triplicate. We made pairwise comparisons between the averages of each triplicate set to normoxia scr using the Partek suite.
Project description:Mitochondria fulfill vital metabolic functions and act as crucial cellular signaling hubs integrating their metabolic status into the cellular context. Here, we show that defective cardiolipin-remodeling, upon loss of the cardiolipin acyl transferase Tafazzin, mutes HIF-1a signaling in hypoxia. Tafazzin-deficiency does not affect posttranslational HIF-1a regulation but rather HIF-1a gene-expression, a dysfunction recapitulated in iPSCs-derived cardiomyocytes from Barth Syndrome patients with Tafazzin-deficiency. RNAseq analyses confirmed drastically altered signaling in Tafazzin mutant cells. In hypoxia, Tafazzin-deficient cells display reduced production of reactive oxygen species (ROS) perturbing NF-kB activation and concomitantly HIF-1a gene-expression. In agreement, Tafazzin-deficient mice hearts display reduced HIF-1a levels and undergo maladaptive hypertrophy with heart failure in response to pressure overload challenge. We conclude that defective mitochondrial cardiolipin-remodeling dampens HIF-1a signaling through inactivation of a non-canonical signaling pathway: Lack of NF-kB activation through reduced mitochondrial ROS production diminishes HIF-1a transcription. Overall design: Cells lacking tafazzin were subjected to hypoxia and compared to the ones at normoxia or isogenic WT cells either at hypoxia or nomoxia
Project description:HIF-1A and HIF-2A regulate both overlapping and unique target genes in response to hypoxia. In this dataset, we identify specific HIF-1A and HIF-2A target genes in glioblastoma cells. 12 samples were analysed comprising 4 experimental conditions (normoxia scr, hypoxia scr, hypoxia siHIF1, hypoxia siHIF2) in triplicate. We made pairwise comparisons between the averages of each triplicate set to normoxia scr using the Partek suite.
Project description:Alternative RNA splicing analysis in Hep3B cell cultured under 21% (N1,3,5) or 1.2% (H2,4,6) oxygen Hypoxia is a common characteristic of many solid tumors. The hypoxic microenvironment stabilizes hypoxia-inducible transcription factor 1α (HIF1α) and 2α (HIF2α) to activate gene transcription, which promotes tumor cell survival. 95% of human genes are alternatively spliced, producing RNA isoforms that code functionally distinct proteins. Thus, effective hypoxia response requires increased HIF target gene transcription as well as proper RNA splicing of these HIF target genes. However, it is unclear if and how hypoxia regulates RNA splicing of HIF target genes. This study determined the effects of hypoxia on alternative splicing (AS) of HIF and non-HIF target genes in Hep3B cells and characterized the role of HIF in regulating AS of HIF induced genes. The results indicated that hypoxia generally promotes exon inclusion for hypoxia-induced, but reduces exon inclusion for hypoxia reduced genes. Mechanistically, HIF activity, but not hypoxia per se is found to be necessary and sufficient to increase exon inclusion of several HIF target genes including pyruvate dehydrogenase kinase 1 (PDK1). PDK1 splicing reporters confirmed that transcriptional activation by HIF is sufficient to increase exon inclusion of PDK1 splicing reporter. In contrast, transcriptional activation of the PDK1 minigene by other transcription factor in the absence of endogenous HIF target gene activation fails to alter PDK1 RNA splicing, demonstrating a novel role of HIF target gene(s) in regulating RNA splicing of HIF target genes. Implications:This study demonstrates a novel function of HIF in regulating RNA splicing of HIF target genes. We analyzed total RNA from Hep3B cells cultured under 21% (N1,3,5) or 1.2% (H2,4,6) oxygen using the Affymetrix Human Exon 1.0 ST platform. Array data was processed by Altanalyze software version 2.0.7. Techinical replicates were performed for Nx and Hx treated Hep3B cells
Project description:Upon antigen stimulation, the bioenergetic demands of T cells increase dramatically over the resting state. Although a role for the metabolic switch to glycolysis has been suggested to support increased anabolic activities and facilitate T cell growth and proliferation, whether cellular metabolism controls T cell lineage choices remains poorly understood. Here we report that the glycolytic pathway is actively regulated during the differentiation of inflammatory TH17 and Foxp3-expressing regulatory T cells (Treg), and controls cell fate determination. TH17 but not Treg-inducing conditions resulted in strong upregulation of the glycolytic activity and induction of glycolytic enzymes. Blocking glycolysis inhibited TH17 development while promoting Treg cell generation. Moreover, the transcription factor hypoxia-inducible factor 1a (HIF1a) was selectively expressed in TH17 cells and its induction required signaling through mTOR, a central regulator of cellular metabolism. HIF1a-dependent transcriptional program was important for mediating glycolytic activity, thereby contributing to the lineage choices between TH17 and Treg cells. Lack of HIF1a resulted in diminished TH17 development but enhanced Treg differentiation, and protected mice from autoimmune CNS inflammation. Our studies demonstrate that HIF1a-dependent glycolytic pathway orchestrates a metabolic checkpoint for the differentiation of TH17 and Treg cells. Naïve CD4 T cells from wild-type and HIF1a-deficient mice (in triplicates each group) were differentiated under TH17 conditions for 2.5 days, and RNA was analyzed by microarrays.
Project description:This is a mathematical model comprised of non-linear ordinary differential equations describing the dynamic relationship between hypoxia-inducible factor-1 alpha (HIF-1a) mRNA, HIF-1a protein, and interleukin-15-mediated upstream signalling events in natural killer cells from human blood. Regulatory expressions are also included for mammalian target of rapamycin (mTOR), nuclear factor-kappa beta, and signal transducer and activator of transcription 3 (STAT3).
Project description:Analysis of the transcriptional correlates of FOXP3 expression in suppressive and non-suppressive primary human Treg cell clones. Individual CD4+CD25High or Cd4+CD25- T cells were isolated from human PBMCs and expanded in vitro. After 3 weeks of expansion, individual clones were analysed for FOXP3 expression and in vitro suppressive activity against freshly sorted allogeneic effector T cells. This study analyses the total RNA isolated from FOXP3+ clones with suppressive potency to their non-suppressive counterparts. The resutls of this study should provide insights into the molecular pathways linking FOXP3 expression to distinct aspects of Treg phenotype and function. Total RNA obtained from individual clones of primary human regulatory and effector CD4+T cells.
Project description:Fumarate hydratase (FH) mutations predispose to renal cysts cancer. These cancers overexpress hypoxia-inducible factor-alpha (Hif-1a). We have generated a conditional Fh1 (mouse FH) knockout mice that develop renal cysts and overexpress Hif-1a. In order to identify the contribution of Hif-1a to cyst formation we have intercrossed our mice with conditional HIf-1a KO mice. We intercrossed Fh1/Hif1a mice with kidney specific cre recombinase (Ksp-Cre) and analysed kidney cyst formation. RNA was extracted from cysts from 4xFh1 KO, 4xFh1/Hif-1a KO and 4 control mice. For each comparison littermates were used and the animals were aged 15 weeks i.e. early cystic disease.
Project description:Based on the results of numerous clinical and preclinical analyses, the transcription factor HIF-1a has been identified as an important tumor-promoting factor and is considered to be an attractive target for cancer therapy. To further deconstruct the molecular nature of HIF-1a’s role in tumorigenesis, we have applied lentiviral shRNA transduction to establish HIF-1a-deficient gastric cancer cells. Interestingly, functional analyses failed to show a significant growth defect of HIF-1a-deficient gastric cancer cells in vitro and in vivo. These observations led us to propose that stable inactivation of HIF-1a resulted in efficient compensation enabling cell growth and, ultimately, tumor progression in a HIF-1a-independent manner. To better understand the mechanisms that control this compensation, we performed transcriptomics of control (“scrambled” (SCR)) and HIF-1a-deficient (HIF) gastric cancer cells. Analysis of hypoxia-inducible factor-1alpha (HIF-1a)-deficient gastric cancer cells under normoxia. The transcription factor HIF-1a is a key regulator of oxygen homeostasis and has been identified as an important tumor-promoting factor. Results provide insight into the role of HIF-1a in gastric carcinogenesis. Overall design: Gastric cancer AGS cells were lentiviral and stably transduced with a small hairpin RNA targeting human HIF-1a or a control shRNA. RNA was extracted from control and HIF-1a-deficient cells. Each cell line was analyzed in triplicate for a total of six samples.