[Show abstract][Hide abstract] ABSTRACT: Fulminant hepatic failure (FHF) is a clinical syndrome characterized by sudden and severe impairment of liver function. Mesenchymal stem cells (MSCs) have been proposed as a promising therapeutic approach for FHF. In this study, we have used Propionibacterium acnes (P. acnes)-primed, lipopolysaccharide (LPS)-induced liver injury in mice as an animal model of human FHF. We demonstrated that administration of MSCs significantly ameliorated liver injury and improved the survival rates of mice subjected to P. acnes plus LPS-induced FHF. Allogeneic MSCs showed similar treatment efficacy as autologous MSCs did in FHF. Treatment efficacy of MSCs could be attributed to decreased infiltration and activation of CD4(+) T cells in the liver, inhibition of T helper 1 cells, and induction of regulatory T cells (Tregs). Moreover, decreased DNA copies of P. acnes were detected in the liver of MSC-treated mice. Intriguingly, a distinct liver population of CD11c(+) MHCII(hi) CD80(lo) CD86(lo) regulatory dendritic cells (DCs) was induced by MSCs. Moreover, these DCs induced Treg differentiation through transforming growth factor-β production. Further mechanistic studies demonstrated that MSC-derived prostaglandin E2 and one of its receptors, EP4, played essential roles in the differentiation of CD11c(+) B220(-) DC precursors into regulatory DCs in a phosphoinositide 3-kinase-dependent manner. Conclusion: Our findings demonstrated, for the first time, critical regulatory properties of MSCs for induction of regulatory DCs from CD11c(+) B220(-) DC precursors. This study elucidates an immunoregulatory mechanism of MSCs and further lays a solid foundation for application of MSCs in FHF therapy. (Hepatology 2013;).
[Show abstract][Hide abstract] ABSTRACT: Heme oxygenase-1 (HO-1) has protective effects on liver damage induced by noxious stimuli. The mechanism of action of HO-1 is not well understood. In the present study, we investigate the effect of HO-1 in a model of fulminant hepatic failure induced by Propionibacterium acnes and lipopolysaccharide (LPS). The expression of HO-1 mRNA and protein in the liver was increased after repeated administration of the HO-1 inducer cobalt protoporphyrin IX. We found that HO-1 protected mice from acute liver damage induced by P. acnes/LPS and prolonged survival. On the contrary, administration of the HO-1 inhibitor zinc protoporphyrin IX increased liver damage induced by P. acnes/LPS. Subsequently, to investigate the underlying mechanisms of HO-1 in the acute liver injury model, we primed mice with P. acnes only. We found that the expression of HO-1 mRNA and protein in dendritic cells (DCs) was increased after the administration of cobalt protoporphyrin IX. HO-1 decreased the mature markers major histocompatibility complex II and CD80 on liver DCs. The expression of CCR7, CCL2, and CCL22 mRNA, which are expressed by mature DCs, was also reduced. These liver DCs could not efficiently stimulate CD4+ T cell activation and proliferation. Consequently, HO-1 inhibited the activation, proliferation, and T helper 1 polarization of liver-infiltrating CD4+ T cells and reduced the production of serum alanine aminotransferase and proinflammatory cytokines such as interferon-γ and tumor necrosis factor-α. Taken together, our data suggest that HO-1 alleviates P. acnes/LPS-induced fulminant hepatic failure, probably by inhibiting DC-induced adaptive responses.
Journal of Pharmacology and Experimental Therapeutics 09/2011; 340(1):2-10. · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Graft-versus-host disease (GVHD), a life-threatening complication after allogeneic hematopoietic stem cell transplantation, is caused by alloreactive donor T cells that trigger host tissue damage. The inflammatory environment inside recipients is critical for GVHD pathogenesis, but the underpinning mechanisms remain elusive. Using mouse model of human GVHD, we demonstrate osteopontin (OPN), a potent proinflammatory cytokine, plays an important role in regulating activation, migration, and survival of alloreactive T cells during GVHD. OPN was significantly elevated after irradiation and persisted throughout the course of GVHD. Blockade of OPN attenuated GVHD with reduced accumulation of donor T cells in recipient organs. Amelioration was the result of migration and survival suppression caused by anti-OPN treatment on donor-derived T cells for 2 reasons. First, OPN promoted the migration and infiltration of naive and alloreactive CD8(+) T cells into host organs. Second, it also facilitated activation and viability of donor-derived CD8(+) T cells via synergizing with T-cell receptor/CD3 signaling. Finally, anti-OPN treatment retained graft-versus-leukemia effect of alloreactive CD8(+) T cells. This study demonstrates, to our knowledge for the first time, the critical effect of OPN in the initiation and persistence of CD8(+) T cell-mediated GVHD and validates OPN as a potential target in GVHD prevention.
[Show abstract][Hide abstract] ABSTRACT: Interleukin 17 (IL-17) plays critical roles in the pathogenesis of various autoimmune diseases, including experimental autoimmune encephalomyelitis (EAE). How the signals triggered by this powerful inflammatory cytokine are controlled to avoid abnormal inflammatory responses is not well understood. In this study, we report that TRAF3 is a receptor proximal negative regulator of IL-17 receptor (IL-17R) signaling. TRAF3 greatly suppressed IL-17-induced NF-κB and mitogen-activated protein kinase activation and subsequent production of inflammatory cytokines and chemokines. Mechanistically, the binding of TRAF3 to IL-17R interfered with the formation of the receptor signaling activation complex IL-17R-Act1-TRAF6, resulting in suppression of downstream signaling. TRAF3 markedly inhibited IL-17-induced expression of inflammatory cytokine and chemokine genes in vivo and consequently delayed the onset and greatly reduced the incidence and severity of EAE. Thus, TRAF3 is a negative regulator of IL-17R proximal signaling.
Journal of Experimental Medicine 11/2010; 207(12):2647-62. · 13.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Allogeneic umbilical cord blood haematopoietic stem cells (UCB-HSCs) can be transplanted into a host with the intact innate immunity with limited immuno-reaction, although the mechanisms remain unclear. The present studies aimed at investigating potential mechanisms of allogeneic UCB-HSCs escape from the cytolysis of natural killer (NK) cells. We compared UCB-HSCs ability to protect from NK-mediated cytotoxicity with peripheral blood or bone marrow haematopoietic stem cells (PB-HSCs and BM-HSCs). HSCs expressed lower levels of natural cytotoxicity receptor ligands including NKp30L, NKp44L and NKp46L than monocytes. Blocking these ligands respectively or in combination could increase the resistance of HSCs against NK cell mediated cytotoxicity. High expression of HLA-G was noticed on UCB-HSCs, rather than PB-HSCs or BM-HSCs, whereas blockade of HLA-G significantly elevated NK cell mediated cytolysis to UCB-HSCs. Thus, we conclude that natural cytotoxicity receptors and HLA-G on HSCs may contribute to the escape from NK cells, and activate and inhibitory NK cell receptors and their ligands can be novel therapeutic targets in cell transplantation.
Journal of Cellular and Molecular Medicine 11/2010; 15(10):2040-5. · 3.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CD40, a member of the tumor necrosis factor receptor superfamily, is widely expressed on various cell types. Some studies show that CD40 expression is related to several carcinomas, where its function remains largely unknown. This study investigated the expression of CD40 on colon cancer, and evaluated the effect of recombinant soluble human CD40L (rshCD40L) on colon cell lines. CD40 expression on the primary colon cancer samples was detected by immunohistochemistry. The expression of CD40 on colon cell lines was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry. To examine the effects of rshCD40L, the growth-inhibitory activity of rshCD40L on colon cancer cell was examined by MTT assay and the proportion of apoptotic tumor cells was examined in the TUNEL assay. Results showed that CD40 is expressed in human colon primary tumor. Expression of CD40 was elevated in 3 out of 4 colon cell lines examined by RT-PCR and flow cytometry. CD40 expression could be induced by interferon-gamma (IFN-gamma). CD40 ligand, rshCD40L, significantly inhibited the proliferation of the CD40(+) colon cancer cell lines. The inhibition could also be enhanced by IFN-gamma in HCT116 and SW48 cell lines. In addition, rshCD40L induced apoptosis of the CD40(+) colon cancer cell lines. Theses results suggest that CD40 present in colon cancer, and rshCD40L may be of clinical use to inhibit human colon cancer growth.