Deficiency in mouse hyaluronidase 2: a new mechanism of chronic thrombotic microangiopathy.
; ; et al
in Haematologica (2015)
Hyaluronan is a major component of the extracellular matrix and glycocalyx. Its main somatic degrading enzymes are the hyaluronidases 1 and 2, none of which is active in the bloodstream. We generated ... [more ▼]
Hyaluronan is a major component of the extracellular matrix and glycocalyx. Its main somatic degrading enzymes are the hyaluronidases 1 and 2, none of which is active in the bloodstream. We generated hyaluronidase 2 deficient mice. They suffer from mild chronic anemia and thrombocytopenia, in parallel with a 10-fold increase in plasma hyaluronan concentration. The current study explores the mechanism of these hematological anomalies. The decreased erythrocyte and platelet counts were assigned to peripheral consumption. The erythrocyte half-life was reduced from 25 to 8 days without signs of premature aging. Hyaluronidase 2 deficient platelets were functional. Major intrinsic defects in erythrocyte membrane or stability, as well as detrimental effects of high hyaluronan levels on erythrocytes, were ruled out in vitro. Normal erythrocytes transfused into hyaluronidase 2 deficient mice were quickly destroyed but neither splenectomy nor anti-C5 administration prevented from chronic hemolysis. Schistocytes were present in hyaluronidase 2 deficient smears at a level of 1 to 6%, while virtually absent in control mice. Hyaluronidase 2 deficient mice had increased markers of endothelial damage and microvascular fibrin deposition, without renal failure, accumulation of ultra-large multimers of von Willebrand factor, deficiency of A Disintegrin And Metalloproteinase with ThromboSpondin type 1 motifs, member 13 (ADAMTS13), or hypertension. There was no sign of structural damage in hepatic or splenic sinusoids, or in any other microvessels. We conclude that hyaluronidase 2 deficiency induces chronic thrombotic microangiopathy with hemolytic anemia in mice. The link between this uncommon condition and hyaluronidase 2 remains to be explored in man. [less ▲]Detailed reference viewed: 25 (8 ULg)
Antigen presenting cell-derived IL-6 restricts Th2-cell differentiation.
; ; et al
in European Journal of Immunology (2014), 44(11), 3252-62
The identification of DC-derived signals orchestrating activation of Th1 and Th17 immune responses has advanced our understanding on how these inflammatory responses develop. However, whether specific ... [more ▼]
The identification of DC-derived signals orchestrating activation of Th1 and Th17 immune responses has advanced our understanding on how these inflammatory responses develop. However, whether specific signals delivered by DCs also participate in the regulation of Th2 immune responses remains largely unknown. In this study, we show that administration of antigen-loaded, IL-6-deficient DCs to naive mice induced an exacerbated Th2 response, characterized by the differentiation of GATA-3-expressing T lymphocytes secreting high levels of IL-4, IL-5, and IL-13. Coinjection of wild type and IL-6-deficient bone marrow-derived dendritic cells (BMDCs) confirmed that IL-6 exerted a dominant, negative influence on Th2-cell development. This finding was confirmed in vitro, where exogenously added IL-6 was found to limit IL-4-induced Th2-cell differentiation. iNKT cells were required for optimal Th2-cell differentiation in vivo although their activation occurred independently of IL-6 secretion by the BMDCs. Collectively, these observations identify IL-6 secretion as a major, unsuspected, mechanism whereby DCs control the magnitude of Th2 immunity. [less ▲]Detailed reference viewed: 11 (1 ULg)
Sirtuin 1 Promotes Th2 Responses and Airway Allergy by Repressing Peroxisome Proliferator-Activated Receptor-γ Activity in Dendritic Cells
; Marichal, Thomas ; Fievez, Laurence et al
in Journal of Immunology (2011), 187(9), 4517-4529
Sirtuins are a unique class of NAD+-dependent deacetylases that regulate diverse biological functions such as aging, metabolism, and stress resistance. Recently, it has been shown that sirtuins may have ... [more ▼]
Sirtuins are a unique class of NAD+-dependent deacetylases that regulate diverse biological functions such as aging, metabolism, and stress resistance. Recently, it has been shown that sirtuins may have anti-inflammatory activities by inhibiting proinflammatory transcription factors such as NF-κB. In contrast, we report in this study that pharmacological inhibition of sirtuins dampens adaptive Th2 responses and subsequent allergic inflammation by interfering with lung dendritic cell (DC) function in a mouse model of airway allergy. Using genetic engineering, we demonstrate that sirtuin 1 represses the activity of the nuclear receptor peroxisome proliferator-activated receptor-γ in DCs, thereby favoring their maturation toward a pro-Th2 phenotype. This study reveals a previously unappreciated function of sirtuin 1 in the regulation of DC function and Th2 responses, thus shedding new light on our current knowledge on the regulation of inflammatory processes by sirtuins. [less ▲]Detailed reference viewed: 54 (21 ULg)
C-terminal mutants of apolipoprotein L-I efficiently kill both Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense.
; ; et al
in PLoS Pathogens (2009), 5(12), 1000685
Apolipoprotein L-I (apoL1) is a human-specific serum protein that kills Trypanosoma brucei through ionic pore formation in endosomal membranes of the parasite. The T. brucei subspecies rhodesiense and ... [more ▼]
Apolipoprotein L-I (apoL1) is a human-specific serum protein that kills Trypanosoma brucei through ionic pore formation in endosomal membranes of the parasite. The T. brucei subspecies rhodesiense and gambiense resist this lytic activity and can infect humans, causing sleeping sickness. In the case of T. b. rhodesiense, resistance to lysis involves interaction of the Serum Resistance-Associated (SRA) protein with the C-terminal helix of apoL1. We undertook a mutational and deletional analysis of the C-terminal helix of apoL1 to investigate the linkage between interaction with SRA and lytic potential for different T. brucei subspecies. We confirm that the C-terminal helix is the SRA-interacting domain. Although in E. coli this domain was dispensable for ionic pore-forming activity, its interaction with SRA resulted in inhibition of this activity. Different mutations affecting the C-terminal helix reduced the interaction of apoL1 with SRA. However, mutants in the L370-L392 leucine zipper also lost in vitro trypanolytic activity. Truncating and/or mutating the C-terminal sequence of human apoL1 like that of apoL1-like sequences of Papio anubis resulted in both loss of interaction with SRA and acquired ability to efficiently kill human serum-resistant T. b. rhodesiense parasites, in vitro as well as in transgenic mice. These findings demonstrate that SRA interaction with the C-terminal helix of apoL1 inhibits its pore-forming activity and determines resistance of T. b. rhodesiense to human serum. In addition, they provide a possible explanation for the ability of Papio serum to kill T. b. rhodesiense, and offer a perspective to generate transgenic cattle resistant to both T. b. brucei and T. b. rhodesiense. [less ▲]Detailed reference viewed: 44 (4 ULg)
Essential role of sirtuins in the pathogenesis of allergic airway inflammation
Legutko, Agnieszka ; Marichal, Thomas ; Fievez, Laurence et al
in Short book of the Annual Congress of the European Respiratory Society (ERS), Vienne (2009)Detailed reference viewed: 32 (7 ULg)
Interleukin-6/STAT3 signaling regulates the ability of naive T cells to acquire B-cell help capacities
; ; Bureau, Fabrice et al
in Blood (2009), 113(11), 2426-2433
The conditions leading to the activation/differentiation of T-helper (Th) cells dedicated for B-cell antibody production are still poorly characterized. We now demonstrate that interleukin-6 (IL-6 ... [more ▼]
The conditions leading to the activation/differentiation of T-helper (Th) cells dedicated for B-cell antibody production are still poorly characterized. We now demonstrate that interleukin-6 (IL-6) promotes the differentiation of naive T lymphocytes into helper cells able to promote B-cell activation and antibody secretion. IL-6-driven acquisition of B-cell help capacity requires expression of the signal transducer and activator of transcription 3 (STAT3), but not STAT4 or STAT6 transcription factors, suggesting that the ability to provide help to B cells is not restricted to a well-defined Th1 or Th2 effector population. T cell-specific STAT3-deficient mice displayed reduced humoral responses in vivo that could not be related to an altered expansion of CXCR5-expressing helper T cells. IL-6 was shown to promote IL-21 secretion, a cytokine that was similarly found to promote the differentiation of naive T cells into potent B-cell helper cells. Collectively, these data indicate that the ability to provide B-cell help is regulated by IL-6/IL-21 through STAT3 activation, independently of Th1, Th2, Th17, or follicular helper T cell (T(FH)) differentiation [less ▲]Detailed reference viewed: 63 (7 ULg)
Nicotinamide phosphoribosyl transferase/pre-B cell colony-enhancing factor/visfatin is required for lymphocyte development and cellular resistance to genotoxic stress.
; ; et al
in Journal of Immunology (2008), 181(7), 4685-4695
Nicotinamide phosphoribosyl transferase (Nampt)/pre-B cell colony-enhancing factor (PBEF)/visfatin is a protein displaying multiple functional properties. Originally described as a cytokine-like protein ... [more ▼]
Nicotinamide phosphoribosyl transferase (Nampt)/pre-B cell colony-enhancing factor (PBEF)/visfatin is a protein displaying multiple functional properties. Originally described as a cytokine-like protein able to regulate B cell development, apoptosis, and glucose metabolism, this protein also plays an important role in NAD biosynthesis. To gain insight into its physiological role, we have generated a mouse strain expressing a conditional Nampt allele. Lack of Nampt expression strongly affects development of both T and B lymphocytes. Analysis of hemizygous cells and in vitro cell lines expressing distinct levels of Nampt illustrates the critical role of this protein in regulating intracellular NAD levels. Consequently, a clear relationship was found between intracellular Nampt levels and cell death in response to the genotoxic agent MNNG (N-methyl-N'-nitro-N-nitrosoguanidine), confirming that this enzyme represents a key regulator of cell sensitivity to NAD-consuming stress secondary to poly(ADP-ribose) polymerases overactivation. By using mutant forms of this protein and a well-characterized pharmacological inhibitor (FK866), we unequivocally demonstrate that the ability of the Nampt to regulate cell viability during genotoxic stress requires its enzymatic activity. Collectively, these data demonstrate that Nampt participates in cellular resistance to genotoxic/oxidative stress, and it may confer to cells of the immune system the ability to survive during stressful situations such as inflammation. [less ▲]Detailed reference viewed: 66 (9 ULg)