Research Article
Abstract
Successful transplantation requires the prevention of allograft rejection and, in the case of transplantation to treat autoimmune disease, the suppression of autoimmune responses. The standard immunosuppressive treatment regimen given to patients with autoimmune type 1 diabetes who have received an islet transplant results in the loss of T cells. In many other situations, the immune system responds to T cell loss through cytokine-dependant homeostatic proliferation of any remaining T cells. Here we show that T cell loss after islet transplantation in patients with autoimmune type 1 diabetes was associated with both increased serum concentrations of IL-7 and IL-15 and in vivo proliferation of memory CD45RO+ T cells, highly enriched in autoreactive glutamic acid decarboxylase 65–specific T cell clones. Immunosuppression with FK506 and rapamycin after transplantation resulted in a chronic homeostatic expansion of T cells, which acquired effector function after immunosuppression was removed. In contrast, the cytostatic drug mycophenolate mofetil efficiently blocked homeostatic T cell expansion. We propose that the increased production of cytokines that induce homeostatic expansion could contribute to recurrent autoimmunity in transplanted patients with autoimmune disease and that therapy that prevents the expansion of autoreactive T cells will improve the outcome of islet transplantation.
Authors
Paolo Monti, Miriam Scirpoli, Paola Maffi, Nadia Ghidoli, Francesca De Taddeo, Federico Bertuzzi, Lorenzo Piemonti, Marika Falcone, Antonio Secchi, Ezio Bonifacio
Abstract
CD36 is a scavenger receptor that binds multiple ligands, including phosphatidyl serine (PS). Although CD36– mice do not have a bleeding diathesis, we show here that they do have significantly prolonged thrombotic occlusion times in response to FeCl3-induced vascular injury. Because cell-derived microparticles (MPs) are generated in response to vascular injury and circulate in patients with prothrombotic diseases, we hypothesized that PS exposed on their surfaces could be an endogenous CD36 ligand that transmits an activating signal to platelets. We found that MPs prepared from human ECs, monocytes, or platelets or isolated from blood of normal subjects bound to platelets. Binding was not observed with platelets from CD36– donors and was inhibited by an anti-CD36 antibody or by blockade of exposed PS by annexin V or anti-PS IgM. Preincubation of platelets with MPs led to CD36-dependent augmentation of platelet activation in response to low doses of ADP, as assessed by measuring α2bβ3 activation, P-selectin expression, and aggregation. Immunofluorescence confocal microscopy of murine carotid thrombi from CD36– mice showed a significant decrement in endothelial antigen accumulation, which suggests that CD36 plays a role in MP recruitment into thrombi. These results provide what we believe to be a novel role for CD36 in thrombosis.
Authors
Arunima Ghosh, Wei Li, Maria Febbraio, Ricardo G. Espinola, Keith R. McCrae, Erin Cockrell, Roy L. Silverstein
Abstract
Knockout and transgenic studies in mice demonstrate that normal somatic tissues redundantly express 3 cyclin D proteins, whereas tumor cells seem dependent on a single overexpressed cyclin D. Thus, selective suppression of the individual cyclin D deregulated in a tumor represents a biologically valid approach to targeted cancer therapy. In multiple myeloma, overexpression of 1 of the cyclin D proteins is a ubiquitous feature, unifying at least 7 different initiating genetic events. We demonstrate here that RNAi of genes encoding cyclin D1 and cyclin D2 (CCND1 and CCND2, respectively) inhibits proliferation and is progressively cytotoxic in human myeloma cells. By screening a chemical library using a cell-based assay for inhibition of CCND2 trans-activation, we identified the plant cytokinin kinetin riboside as an inhibitor of CCND2 trans-activation. Kinetin riboside induced marked suppression of CCND2 transcription and rapidly suppressed cyclin D1 and D2 protein expression in primary myeloma cells and tumor lines, causing cell-cycle arrest, tumor cell–selective apoptosis, and inhibition of myeloma growth in xenografted mice. Mechanistically, kinetin riboside upregulated expression of transcription repressor isoforms of cAMP-response element modulator (CREM) and blocked both trans-activation of CCND2 by various myeloma oncogenes and cis-activation of translocated CCND1, suggesting induction of an overriding repressor activity that blocks multiple oncogenic pathways targeting cyclin D genes. These data support targeted repression of cyclin D genes as a therapeutic strategy for human malignancies.
Authors
Rodger E. Tiedemann, Xinliang Mao, Chang-Xin Shi, Yuan Xiao Zhu, Stephen E. Palmer, Michael Sebag, Ron Marler, Marta Chesi, Rafael Fonseca, P. Leif Bergsagel, Aaron D. Schimmer, A. Keith Stewart
Abstract
Deregulated activation of STAT3 is frequently associated with many human hematological and epithelial malignancies, including gastric cancer. While exaggerated STAT3 signaling facilitates an antiapoptotic, proangiogenic, and proproliferative environment for neoplastic cells, the molecular mechanisms leading to STAT3 hyperactivation remain poorly understood. Using the gp130Y757F/Y757F mouse model of gastric cancer, which carries a mutated gp130 cytokine receptor signaling subunit that cannot bind the negative regulator of cytokine signaling SOCS3 and is characterized by hyperactivation of the signaling molecules STAT1 and STAT3, we have provided genetic evidence that IL-11 promotes chronic gastric inflammation and associated tumorigenesis. Expression of IL-11 was increased in gastric tumors in gp130Y757F/Y757F mice, when compared with unaffected gastric tissue in wild-type mice, while gp130Y757F/Y757F mice lacking the IL-11 ligand–binding receptor subunit (IL-11Rα) showed normal gastric STAT3 activation and IL-11 expression and failed to develop gastric tumors. Furthermore, reducing STAT3 activity in gp130Y757F/Y757F mice, either genetically or by therapeutic administration of STAT3 antisense oligonucleotides, normalized gastric IL-11 expression and alleviated gastric tumor burden. Surprisingly, the genetic reduction of STAT1 expression also reduced gastric tumorigenesis in gp130Y757F/Y757F mice and coincided with reduced gastric inflammation and IL-11 expression. Collectively, our data have identified IL-11 as a crucial cytokine promoting chronic gastric inflammation and associated tumorigenesis mediated by excessive activation of STAT3 and STAT1.
Authors
Matthias Ernst, Meri Najdovska, Dianne Grail, Therese Lundgren-May, Michael Buchert, Hazel Tye, Vance B. Matthews, Jane Armes, Prithi S. Bhathal, Norman R. Hughes, Eric G. Marcusson, James G. Karras, Songqing Na, Jonathon D. Sedgwick, Paul J. Hertzog, Brendan J. Jenkins
Abstract
Increased albuminuria is associated with obesity and diabetes and is a risk factor for cardiovascular and renal disease. However, the link between early albuminuria and adiposity remains unclear. To determine whether adiponectin, an adipocyte-derived hormone, is a communication signal between adipocytes and the kidney, we performed studies in a cohort of patients at high risk for diabetes and kidney disease as well as in adiponectin-knockout (Ad–/–) mice. Albuminuria had a negative correlation with plasma adiponectin in obese patients, and Ad–/– mice exhibited increased albuminuria and fusion of podocyte foot processes. In cultured podocytes, adiponectin administration was associated with increased activity of AMPK, and both adiponectin and AMPK activation reduced podocyte permeability to albumin and podocyte dysfunction, as evidenced by zona occludens–1 translocation to the membrane. These effects seemed to be caused by reduction of oxidative stress, as adiponectin and AMPK activation both reduced protein levels of the NADPH oxidase Nox4 in podocytes. Ad–/– mice treated with adiponectin exhibited normalization of albuminuria, improvement of podocyte foot process effacement, increased glomerular AMPK activation, and reduced urinary and glomerular markers of oxidant stress. These results suggest that adiponectin is a key regulator of albuminuria, likely acting through the AMPK pathway to modulate oxidant stress in podocytes.
Authors
Kumar Sharma, Satish RamachandraRao, Gang Qiu, Hitomi Kataoka Usui, Yanqing Zhu, Stephen R. Dunn, Raogo Ouedraogo, Kelly Hough, Peter McCue, Lawrence Chan, Bonita Falkner, Barry J. Goldstein
Abstract
Infection of primates by HIV-1 and SIV induces multiple hematological abnormalities of central hematopoietic origin. Although these defects greatly contribute to the pathophysiology of HIV-1 infection, the molecular basis for altered BM function remains unknown. Here we show that when cynomolgus macaques were infected with SIV, the multipotent potential of their hematopoietic progenitor cells was lost, and this correlated with downregulation of STAT5A and STAT5B expression. However, forced expression of STAT5B entirely rescued the multipotent potential of the hematopoietic progenitor cells. In addition, an accessory viral protein required for efficient SIV and HIV replication and pathogenicity, “Negative factor” (Nef), was essential for SIV-mediated impairment of the multipotent potential of hematopoietic progenitors ex vivo and in vivo. This newly uncovered property of Nef was both conserved between HIV-1 and SIV strains and entirely dependent upon the presence of PPARγ in targeted cells. Further, PPARγ agonists mimicked Nef activity by inhibiting STAT5A and STAT5B expression and hampering the functionality of hematopoietic progenitors both ex vivo and in vivo. These findings have extended the role of Nef in the pathogenicity of HIV-1 and SIV and reveal a pivotal role for the PPARγ/STAT5 pathway in the regulation of early hematopoiesis. This study may provide a basis for investigating the potential therapeutic benefits of PPARγ antagonists in both patients with AIDS and individuals with hematopoietic disorders.
Authors
Stéphane Prost, Mikael Le Dantec, Sylvie Augé, Roger Le Grand, Sonia Derdouch, Gwenaelle Auregan, Nicole Déglon, Francis Relouzat, Anne-Marie Aubertin, Bernard Maillere, Isabelle Dusanter-Fourt, Marek Kirszenbaum
Abstract
Mutations in the RET gene are the primary cause of Hirschsprung disease (HSCR), or congenital intestinal aganglionosis. However, how RET malfunction leads to HSCR is not known. It has recently been shown that the binding of glial cell line–derived neurotrophic factor (GDNF) to GDNF family receptor α1 (GFRα1) activates RET and is essential for the survival of enteric neurons. In this study, we investigated Ret regulation of enteric neuron survival and its potential involvement in HSCR. Conditional ablation of Ret in postmigratory enteric neurons caused widespread neuronal death in the colon, which led to colonic aganglionosis. To further examine this finding, we generated a mouse model for HSCR by reducing Ret expression levels. These mice recapitulated the genetic and phenotypic features of HSCR and developed colonic aganglionosis due to impaired migration and successive death of enteric neural crest–derived cells. Death of enteric neurons was also induced in the colon, where reduction of Ret expression was induced after the period of enteric neural crest cell migration, indicating that diminished Ret expression directly affected the survival of colonic neurons. Thus, enteric neuron survival is sensitive to RET dosage, and cell death is potentially involved in the etiology of HSCR.
Authors
Toshihiro Uesaka, Mayumi Nagashimada, Shigenobu Yonemura, Hideki Enomoto
Abstract
Following injury, the clearance of apoptotic and necrotic cells is necessary for mitigation and resolution of inflammation and tissue repair. In addition to macrophages, which are traditionally assigned to this task, neighboring epithelial cells in the affected tissue are postulated to contribute to this process. Kidney injury molecule–1 (KIM-1 or TIM-1) is an immunoglobulin superfamily cell-surface protein not expressed by cells of the myeloid lineage but highly upregulated on the surface of injured kidney epithelial cells. Here we demonstrate that injured kidney epithelial cells assumed attributes of endogenous phagocytes. Confocal images confirm internalization of apoptotic bodies within KIM-1–expressing epithelial cells after injury in rat kidney tubules in vivo. KIM-1 was directly responsible for phagocytosis in cultured primary rat tubule epithelial cells and also porcine and canine epithelial cell lines. KIM-1 was able to specifically recognize apoptotic cell surface-specific epitopes phosphatidylserine, and oxidized lipoproteins, expressed by apoptotic tubular epithelial cells. Thus, KIM-1 is the first nonmyeloid phosphatidylserine receptor identified to our knowledge that transforms epithelial cells into semiprofessional phagocytes.
Authors
Takaharu Ichimura, Edwin J.P.v. Asseldonk, Benjamin D. Humphreys, Lakshman Gunaratnam, Jeremy S. Duffield, Joseph V. Bonventre
Abstract
Homozygous loss-of-function mutations in AIRE cause autoimmune polyglandular syndrome type 1 (APS 1), which manifests in a classic triad of hypoparathyroidism, adrenal insufficiency, and candidiasis. Interestingly, a kindred with a specific G228W AIRE variant presented with an autosomal dominant autoimmune phenotype distinct from APS 1. We utilized a novel G228W-knockin mouse model to show that this variant acted in a dominant-negative manner to cause a unique autoimmunity syndrome. In addition, the expression of a large number of Aire-regulated thymic antigens was partially inhibited in these animals, demonstrating the importance of quantitative changes in thymic antigen expression in determining organ-specific autoimmunity. Furthermore, the dominant-negative effect of the G228W variant was exerted through recruitment of WT Aire away from active sites of transcription in the nucleus of medullary thymic epithelial cells in vivo. Together, these results may demonstrate a mechanism by which autoimmune predisposition to phenotypes distinct from APS 1 can be mediated in a dominant-negative fashion by Aire.
Authors
Maureen A. Su, Karen Giang, Kristina Žumer, Huimin Jiang, Irena Oven, John L. Rinn, Jason J. DeVoss, Kellsey P.A. Johannes, Wen Lu, James Gardner, Angela Chang, Paula Bubulya, Howard Y. Chang, B. Matija Peterlin, Mark S. Anderson
Abstract
Although Rho-associated kinase (ROCK) activity has been implicated in cardiovascular diseases, the tissue- and isoform-specific roles of ROCKs in the vascular response to injury are not known. To address the role of ROCKs in this process, we generated haploinsufficient Rock1 (Rock1+/–) and Rock2 (Rock2+/–) mice and performed carotid artery ligations. Following this intervention, we found reduced neointima formation in Rock1+/– mice compared with that of WT or Rock2+/– mice. This correlated with decreased vascular smooth muscle cell proliferation and survival, decreased levels proinflammatory adhesion molecule expression, and reduced leukocyte infiltration. In addition, thioglycollate-induced peritoneal leukocyte recruitment and accumulation were substantially reduced in Rock1+/– mice compared with those of WT and Rock2+/– mice. To determine the role of leukocyte-derived ROCK1 in neointima formation, we performed reciprocal bone marrow transplantation (BMT) in WT and Rock1+/– mice. Rock1+/– to WT BMT led to reduced neointima formation and leukocyte infiltration following carotid ligation compared with those of WT to WT BMT. In contrast, WT to Rock1+/– BMT resulted in increased neointima formation. These findings indicate that ROCK1 in BM-derived cells mediates neointima formation following vascular injury and suggest that ROCK1 may represent a promising therapeutic target in vascular inflammatory diseases.
Authors
Kensuke Noma, Yoshiyuki Rikitake, Naotsugu Oyama, Guijun Yan, Pilar Alcaide, Ping-Yen Liu, Hongwei Wang, Daniela Ahl, Naoki Sawada, Ryuji Okamoto, Yukio Hiroi, Koichi Shimizu, Francis W. Luscinskas, Jianxin Sun, James K. Liao
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ISSN: 0021-9738 (print), 1558-8238 (online)