Effects of TLR Agonists on the Hypoxia-Regulated Transcription Factor HIF-1α and Dendritic Cell Maturation under Normoxic Conditions

Dendritic cells (DC) are professional antigen presenting cells that represent an important link between innate and adaptive immunity. Danger signals such as toll-like receptor (TLR) agonists induce maturation of DC leading to a T-cell mediated adaptive immune response. In this study, we show that exogenous as well as endogenous inflammatory stimuli for TLR4 and TLR2 induce the expression of HIF-1α in human monocyte-derived DC under normoxic conditions. On the functional level, inhibition of HIF-1α using chetomin (CTM), YC-1 and digoxin lead to no consistent effect on MoDC maturation, or cytokine secretion despite having the common effect of blocking HIF-1α stabilization or activity through different mechanisms. Stabilization of HIF-1α protein by hypoxia or CoCl2 did not result in maturation of human DC. In addition, we could show that TLR stimulation resulted in an increase of HIF-1α controlled VEGF secretion. These results show that stimulation of human MoDC with exogenous as well as endogenous TLR agonists induces the expression of HIF-1α in a time-dependent manner. Hypoxia alone does not induce maturation of DC, but is able to augment maturation after TLR ligation. Current evidence suggests that different target genes may be affected by HIF-1α under normoxic conditions with physiological roles that differ from those induced by hypoxia.

[1]  Jun O. Liu,et al.  Digoxin and other cardiac glycosides inhibit HIF-1α synthesis and block tumor growth , 2008, Proceedings of the National Academy of Sciences.

[2]  A. Elia,et al.  Human dendritic cells differentiated in hypoxia down‐modulate antigen uptake and change their chemokine expression profile , 2008, Journal of leukocyte biology.

[3]  A. Sica,et al.  Divergent effects of hypoxia on dendritic cell functions. , 2008, Blood.

[4]  J. Kalbfleisch,et al.  Preconditioning with a TLR2 specific ligand increases resistance to cerebral ischemia/reperfusion injury , 2008, Journal of Neuroimmunology.

[5]  G. Cairo,et al.  Role of HIF-1 and NF-κB Transcription Factors in the Modulation of Transferrin Receptor by Inflammatory and Anti-inflammatory Signals* , 2008, Journal of Biological Chemistry.

[6]  M. Daha,et al.  The Complement Inhibitor Low Molecular Weight Dextran Sulfate Prevents TLR4-Induced Phenotypic and Functional Maturation of Human Dendritic Cells1 , 2008, The Journal of Immunology.

[7]  Katerina Akassoglou,et al.  NF-κB links innate immunity to the hypoxic response through transcriptional regulation of HIF-1α , 2008, Nature.

[8]  M. Hensel,et al.  Hypoxia and Hypoxia-Inducible Factor-1α Modulate Lipopolysaccharide-Induced Dendritic Cell Activation and Function1 , 2008, The Journal of Immunology.

[9]  P. Lepper.  Faculty Opinions recommendation of Cutting edge: Essential role of hypoxia inducible factor-1alpha in development of lipopolysaccharide-induced sepsis. , 2007 .

[10]  T. Billiar,et al.  Toll-Like Receptor 4 Mediates the Early Inflammatory Response After Cold Ischemia/Reperfusion , 2007, Transplantation.

[11]  K. Peter,et al.  Shedding of the Endothelial Glycocalyx in Patients Undergoing Major Vascular Surgery With Global and Regional Ischemia , 2007, Circulation.

[12]  J. Kalbfleisch,et al.  Activation of Toll-like receptor 4 signaling contributes to hippocampal neuronal death following global cerebral ischemia/reperfusion , 2007, Journal of Neuroimmunology.

[13]  S. Chadban,et al.  TLR4 activation mediates kidney ischemia/reperfusion injury. , 2007, The Journal of clinical investigation.

[14]  Kenshi Yamasaki,et al.  Recognition of Hyaluronan Released in Sterile Injury Involves a Unique Receptor Complex Dependent on Toll-like Receptor 4, CD44, and MD-2* , 2007, Journal of Biological Chemistry.

[15]  F. Lee,et al.  YC-1 inhibits HIF-1 expression in prostate cancer cells: contribution of Akt/NF-κB signaling to HIF-1α accumulation during hypoxia , 2007, Oncogene.

[16]  M. Słupski,et al.  Guanylate cyclase activators influence reactivity of human mesenteric superior arteries retrieved and preserved in the same conditions as transplanted kidneys. , 2007, Transplantation proceedings.

[17]  Marc Chanson,et al.  Airway epithelial IL-15 transforms monocytes into dendritic cells. , 2007, American journal of respiratory cell and molecular biology.

[18]  B. Rothen‐Rutishauser,et al.  Exovesicles from human activated dendritic cells fuse with resting dendritic cells, allowing them to present alloantigens. , 2006, The American journal of pathology.

[19]  H. Abboud,et al.  Angiotensin II stimulation of VEGF mRNA translation requires production of reactive oxygen species. , 2006, American journal of physiology. Renal physiology.

[20]  J. Kastelein,et al.  Loss of endothelial glycocalyx during acute hyperglycemia coincides with endothelial dysfunction and coagulation activation in vivo. , 2006, Diabetes.

[21]  S. Akira,et al.  Renal-associated TLR2 mediates ischemia/reperfusion injury in the kidney. , 2005, The Journal of clinical investigation.

[22]  S. Kuo,et al.  YC-1 suppresses constitutive nuclear factor-κB activation and induces apoptosis in human prostate cancer cells , 2005, Molecular Cancer Therapeutics.

[23]  V. Nizet,et al.  HIF-1alpha expression regulates the bactericidal capacity of phagocytes. , 2005, The Journal of clinical investigation.

[24]  E. Van Obberghen,et al.  Regulation of hypoxia-inducible factor (HIF)-1 activity and expression of HIF hydroxylases in response to insulin-like growth factor I. , 2005, Molecular endocrinology.

[25]  M. Simon,et al.  Hypoxic reduction in cellular glutathione levels requires mitochondrial reactive oxygen species. , 2004, Journal of applied physiology.

[26]  H. Gałkowska.  Dendritic cells as regulators of immune reactivity: implications for skin transplantation. , 2004, Annals of transplantation.

[27]  D. Livingston,et al.  Small molecule blockade of transcriptional coactivation of the hypoxia-inducible factor pathway. , 2004, Cancer cell.

[28]  J. Simon,et al.  Hyaluronan Fragments Stimulate Endothelial Recognition of Injury through TLR4* , 2004, Journal of Biological Chemistry.

[29]  C. Hughes,et al.  Of Mice and Not Men: Differences between Mouse and Human Immunology , 2004, The Journal of Immunology.

[30]  Caroline C. Blouin,et al.  Hypoxic gene activation by lipopolysaccharide in macrophages: implication of hypoxia-inducible factor 1alpha. , 2004, Blood.

[31]  R. Jaenisch,et al.  HIF-1α Is Essential for Myeloid Cell-Mediated Inflammation , 2003, Cell.

[32]  A. Beg,et al.  Endogenous ligands of Toll-like receptors: implications for regulating inflammatory and immune responses. , 2002, Trends in immunology.

[33]  J. Platt,et al.  Receptor-Mediated Monitoring of Tissue Well-Being Via Detection of Soluble Heparan Sulfate by Toll-Like Receptor 41 , 2002, The Journal of Immunology.

[34]  T. Ahrens,et al.  Oligosaccharides of Hyaluronan Activate Dendritic Cells via Toll-like Receptor 4 , 2002, The Journal of experimental medicine.

[35]  F. Re,et al.  Toll-like Receptor 2 (TLR2) and TLR4 Differentially Activate Human Dendritic Cells* , 2001, The Journal of Biological Chemistry.

[36]  G. Semenza,et al.  Hypoxia-inducible factor 1: oxygen homeostasis and disease pathophysiology. , 2001, Trends in molecular medicine.

[37]  N. Chandel,et al.  Reactive Oxygen Species Generated at Mitochondrial Complex III Stabilize Hypoxia-inducible Factor-1α during Hypoxia , 2000, The Journal of Biological Chemistry.

[38]  P. Prehm,et al.  Synthesis and shedding of hyaluronan from plasma membranes of human fibroblasts and metastatic and non-metastatic melanoma cells. , 1999, The Biochemical journal.

[39]  M. Shlomchik,et al.  Prevention of graft versus host disease by inactivation of host antigen-presenting cells. , 1999, Science.

[40]  L. Lu,et al.  Dendritic cells as regulators of immune reactivity: implications for transplantation. , 1999, Transplantation.

[41]  M. Rothe,et al.  Peptidoglycan- and Lipoteichoic Acid-induced Cell Activation Is Mediated by Toll-like Receptor 2* , 1999, The Journal of Biological Chemistry.

[42]  R. Steinman,et al.  Dendritic cells and the control of immunity , 1998, Nature.

[43]  H. Tajiri,et al.  Induction of vascular endothelial growth factor by nitric oxide in human glioblastoma and hepatocellular carcinoma cells , 1997, Oncogene.

[44]  M. Nagao,et al.  Activation of Hypoxia-inducible Factor-1; Definition of Regulatory Domains within the α Subunit* , 1997, The Journal of Biological Chemistry.

[45]  J. Platt,et al.  Shedding of heparan sulfate proteoglycan by stimulated endothelial cells: Evidence for proteolysis of cell‐surface molecules , 1996, Journal of cellular physiology.

[46]  G. Semenza,et al.  Hypoxia-inducible factor 1 is a basic-helix-loop-helix-PAS heterodimer regulated by cellular O2 tension. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[47]  F. Sallusto,et al.  Efficient presentation of soluble antigen by cultured human dendritic cells is maintained by granulocyte/macrophage colony-stimulating factor plus interleukin 4 and downregulated by tumor necrosis factor alpha , 1994, The Journal of experimental medicine.

[48]  J. Platt,et al.  The role of C5a and antibody in the release of heparan sulfate from endothelial cells , 1991, European journal of immunology.

[49]  T. Oegema,et al.  Release of heparan sulfate from endothelial cells. Implications for pathogenesis of hyperacute rejection , 1990, The Journal of experimental medicine.

[50]  D. Faller,et al.  Spontaneous aggregation as a mechanism for human monocyte purification. , 1986, Cellular immunology.

[51]  F. Lee,et al.  YC-1 inhibits HIF-1 expression in prostate cancer cells: contribution of Akt/NF-kappaB signaling to HIF-1alpha accumulation during hypoxia. , 2007, Oncogene.

[52]  S. Chadban,et al.  TLR 4 activation mediates kidney ischemia / reperfusion injury , 2007 .

[53]  Yang Pc,et al.  (Am. J. Respir. Cell Mol. Biol., 32:540-547)Autocrine and Paracrine Regulation of IL-8 Expression in Lung Cancer Cells , 2005 .

[54]  R. Jaenisch,et al.  HIF-1alpha is essential for myeloid cell-mediated inflammation. , 2003, Cell.