Overconsumption of lipid-rich diets, in conjunction with physical inactivity, disables and kills staggering numbers of people worldwide. Recent advances in our molecular understanding of cholesterol and triglyceride transport from the small intestine to the rest of the body provide a detailed picture of the fed/fasted and active/sedentary states. Key surprises include the unexpected nature of many pivotal molecular mediators, as well as their dysregulation — but possible reversibility — in obesity, diabetes, inactivity, and related conditions. These mechanistic insights provide new opportunities to correct dyslipoproteinemia, accelerated atherosclerosis, insulin resistance, and other deadly sequelae of overnutrition and underexertion.
Kevin Jon Williams
The use of antibodies against the human B cell surface protein CD20 represents the most advanced therapeutic approach among the B cell–depleting armamentarium for the treatment of autoimmune disorders. However, recent evidence indicates that B cells can also be essential for suppressing unwanted autoaggressive T cell responses, and therefore, a more careful evaluation of which types of autoimmune disorders this therapy should be utilized for, and at which phases of disease this therapy should be applied, is necessary. In this issue of the JCI, Matsushita et al. report that the timing of this therapy is critical for the management of EAE, a mouse model of human MS (see the related article beginning on page 3420). The results suggest the existence of two opposite actions executed by B cells during the course of autoimmune pathology; CD1dhiCD5+ regulatory B cells suppress EAE induction, whereas B cells are required for the expansion of autoantigen-specific T cells during disease progression. Given the existence of such regulatory B cells in humans, these findings not only resolve previously unexplained contradictions with respect to the outcome of B cell–depleting therapy but also provide insight into the best regimen for this treatment approach.
Congenital and acquired diseases of the biliary tree, or cholangiopathies, represent a significant source of morbidity and mortality in both children and adults. In late stages of the disease, cholangiocytes can no longer proliferate, resulting in loss of bile ducts, increased fibrosis, and ultimately cirrhosis and liver failure. Epithelial-mesenchymal transition has been proposed as a potential mechanism underlying both cholangiocyte proliferation and fibrogenesis in biliary diseases. In this issue of the JCI, using a myofibroblast-cholangiocyte coculture system and genetically modified mice, Omenetti and colleagues present evidence supporting the importance of paracrine hedgehog signaling between the two cell types and increased expression of mesenchymal markers in cholangiocytes (see the related article beginning on page 3331). These findings set the stage for future studies to further investigate the contribution of hedgehog signaling in both cholangiocyte repair and fibrogenesis in biliary diseases.
Linda E. Greenbaum
Recently, epigenetic-mediated mechanisms — which involve heritable changes in gene expression in the absence of alterations in DNA sequences — have been proposed as contributing to asthma. In this issue of the JCI, Hollingsworth and colleagues report on the effect of prenatal maternal dietary intake of methyl donors on the risk of allergic airway disease in offspring in mice and show that these effects involve epigenetic regulation (see the related article beginning on page 3462). Supplementation of the maternal diet with methyl donors was associated with greater airway allergic inflammation and IgE production in F1 and, to some extent, F2 progeny. Site-specific differences in DNA methylation and reduced transcriptional activity were detected. If these findings are confirmed, a new paradigm for asthma pathogenesis may be emerging.
Rachel L. Miller
While CD8+ T cells are critical to diabetogenesis in NOD mice, evidence of their involvement in human type 1 diabetes (T1D) has been circumstantial. The existence of CD8+ T cells specific for β cell peptides has been demonstrated, but functional data regarding the role of these cells in T1D have been lacking. In this issue of the JCI, Skowera et al. describe an unusual self-peptide epitope derived from the leader sequence of preproinsulin (PPI) and show that 50% of HLA-A2+ patients with new-onset T1D possessed circulating CD8+ T cells specific for this epitope, suggesting that PPI plays a critical role in the development of T1D (see the related article beginning on page 3390). They also report that β cells upregulate PPI expression in the presence of high glucose levels, rendering these cells more susceptible to lysis and potentially accelerating disease. This suggests that interventions aimed at decreasing the PPI-specific CD8+ T cell response early after T1D diagnosis may be efficacious in ameliorating the disease process.
Jeffrey A. Frelinger
The liver has several unique immunological properties that affect T cell activation and immune regulation. Recent studies have uncovered opportunities for the treatment of genetic disease by directing expression of the functional therapeutic protein to hepatocytes. In a new study in this issue of the JCI, Lüth and colleagues demonstrate that hepatic expression of a brain protein is protective against neuroinflammatory disease in a mouse model of human MS (see the related article beginning on page 3403). Suppression of autoimmunity was dependent on transgene expression in the liver and was mediated by induction of antigen-specific CD4+CD25+Foxp3+ Tregs. These findings suggest that the introduction of antigens to the liver may have potential as a preventative or therapeutic intervention for autoimmune disease.
Brad E. Hoffman, Roland W. Herzog
The current inactivated influenza virus vaccines induce antibodies that protect against closely related virus strains. They do not, however, protect against antibody-escape variants of seasonal influenza A viruses or new pandemic influenza A viruses emerging from non-human reservoirs. Might boosting influenza A virus–specific CD8+ T cell memory diminish the danger posed by these variant viruses? Pre-existing CD8+ T cell–mediated immunity directed at peptides from conserved internal proteins of the influenza A virus does not prevent infection, but it can promote early virus clearance and decrease morbidity in mice. In this issue of the JCI, Lee et al. show that people who have not been exposed to avian influenza A (H5N1) viruses have cross-reactive CD8+ T cell memory to a wide range of H5N1 peptides (see the related article beginning on page 3478). These peptides could be used to add a CD8+ T cell component to current antibody-focused vaccine strategies with a view to reducing the impact of infection with novel influenza A viruses.
Peter C. Doherty, Anne Kelso
Fetal loss induced by antiphospholipid antibodies (aPLs) in mice is a complement-driven inflammatory condition. Engagement of the complement receptor C5aR on neutrophils induces expression of the principal initiator of the blood clotting mechanism, tissue factor (TF), and blocking this downstream event of complement activation prevents antibody-induced fetal loss. In this issue of the JCI, the study by Redecha et al. clarifies that in mice, the contribution of TF to this pathogenic mechanism is independent of its role in coagulation and thrombosis, but involves inflammatory signaling through the receptor PAR2 (see the related article beginning on page 3453). The study not only sheds light on a critical effector mechanism of aPL-induced fetal loss, but also suggests that treatment with statins, which decrease TF and PAR2 expression, may hold promise as a therapeutic approach to antiphospholipid syndrome–associated pregnancy complications.
Glycogen synthase kinase–3 (GSK-3) is a widely expressed and highly conserved serine/threonine protein kinase encoded by 2 genes, GSK3A and GSK3B. GSK-3 is thought to be involved in tissue repair and fibrogenesis, but its role in these processes is currently unknown. To investigate the function of GSK-3β in fibroblasts, we generated mice harboring a fibroblast-specific deletion of Gsk3b and evaluated their wound-healing and fibrogenic responses. We have shown that Gsk3b-conditional-KO mice (Gsk3b-CKO mice) exhibited accelerated wound closure, increased fibrogenesis, and excessive scarring compared with control mice. In addition, Gsk3b-CKO mice showed elevated collagen production, decreased cell apoptosis, elevated levels of profibrotic α-SMA, and increased myofibroblast formation during wound healing. In cultured Gsk3b-CKO fibroblasts, adhesion, spreading, migration, and contraction were enhanced. Both Gsk3b-CKO mice and fibroblasts showed elevated expression and production of endothelin-1 (ET-1) compared with control mice and cells. Antagonizing ET-1 reversed the phenotype of Gsk3b-CKO fibroblasts and mice. Thus, GSK-3β appears to control the progression of wound healing and fibrosis by modulating ET-1 levels. These results suggest that targeting the GSK-3β pathway or ET-1 may be of benefit in controlling tissue repair and fibrogenic responses in vivo.
Mohit Kapoor, Shangxi Liu, Xu Shi-wen, Kun Huh, Matthew McCann, Christopher P. Denton, James R. Woodgett, David J. Abraham, Andrew Leask
Hutchinson-Gilford progeria syndrome (HGPS), a rare disease that results in what appears to be premature aging, is caused by the production of a mutant form of prelamin A known as progerin. Progerin retains a farnesyl lipid anchor at its carboxyl terminus, a modification that is thought to be important in disease pathogenesis. Inhibition of protein farnesylation improves the hallmark nuclear shape abnormalities in HGPS cells and ameliorates disease phenotypes in mice harboring a knockin HGPS mutation (LmnaHG/+). The amelioration of disease, however, is incomplete, leading us to hypothesize that nonfarnesylated progerin also might be capable of eliciting disease. To test this hypothesis, we created knockin mice expressing nonfarnesylated progerin (LmnanHG/+). LmnanHG/+ mice developed the same disease phenotypes observed in LmnaHG/+ mice, although the phenotypes were milder, and mouse embryonic fibroblasts (MEFs) derived from these mice contained fewer misshapen nuclei. The steady-state levels of progerin in LmnanHG/+ MEFs and tissues were lower, suggesting a possible explanation for the milder phenotypes. These data support the concept that inhibition of protein farnesylation in progeria could be therapeutically useful but also suggest that this approach may be limited, as progerin elicits disease phenotypes whether or not it is farnesylated.
Shao H. Yang, Douglas A. Andres, H. Peter Spielmann, Stephen G. Young, Loren G. Fong
Although acute lung injury contributes significantly to critical illness, resolution often occurs spontaneously via activation of incompletely understood pathways. We recently found that mechanical ventilation of mice increases the level of pulmonary adenosine, and that mice deficient for extracellular adenosine generation show increased pulmonary edema and inflammation after ventilator-induced lung injury (VILI). Here, we profiled the response to VILI in mice with genetic deletions of each of the 4 adenosine receptors (ARs) and found that deletion of the A2BAR gene was specifically associated with reduced survival time and increased pulmonary albumin leakage after injury. In WT mice, treatment with an A2BAR-selective antagonist resulted in enhanced pulmonary inflammation, edema, and attenuated gas exchange, while an A2BAR agonist attenuated VILI. In bone marrow–chimeric A2BAR mice, although the pulmonary inflammatory response involved A2BAR signaling from bone marrow–derived cells, A2BARs located on the lung tissue attenuated VILI-induced albumin leakage and pulmonary edema. Furthermore, measurement of alveolar fluid clearance (AFC) demonstrated that A2BAR signaling enhanced amiloride-sensitive fluid transport and elevation of pulmonary cAMP levels following VILI, suggesting that A2BAR agonist treatment protects by drying out the lungs. Similar enhancement of pulmonary cAMP and AFC were also observed after β-adrenergic stimulation, a pathway known to promote AFC. Taken together, these studies reveal a role for A2BAR signaling in attenuating VILI and implicate this receptor as a potential therapeutic target during acute lung injury.
Tobias Eckle, Almut Grenz, Stefanie Laucher, Holger K. Eltzschig
Spinal muscular atrophy (SMA), a motor neuron disease (MND) and one of the most common genetic causes of infant mortality, currently has no cure. Patients with SMA exhibit muscle weakness and hypotonia. Stem cell transplantation is a potential therapeutic strategy for SMA and other MNDs. In this study, we isolated spinal cord neural stem cells (NSCs) from mice expressing green fluorescent protein only in motor neurons and assessed their therapeutic effects on the phenotype of SMA mice. Intrathecally grafted NSCs migrated into the parenchyma and generated a small proportion of motor neurons. Treated SMA mice exhibited improved neuromuscular function, increased life span, and improved motor unit pathology. Global gene expression analysis of laser-capture-microdissected motor neurons from treated mice showed that the major effect of NSC transplantation was modification of the SMA phenotype toward the wild-type pattern, including changes in RNA metabolism proteins, cell cycle proteins, and actin-binding proteins. NSC transplantation positively affected the SMA disease phenotype, indicating that transplantation of NSCs may be a possible treatment for SMA.
Stefania Corti, Monica Nizzardo, Martina Nardini, Chiara Donadoni, Sabrina Salani, Dario Ronchi, Francesca Saladino, Andreina Bordoni, Francesco Fortunato, Roberto Del Bo, Dimitra Papadimitriou, Federica Locatelli, Giorgia Menozzi, Sandra Strazzer, Nereo Bresolin, Giacomo P. Comi
Epithelial-mesenchymal transitions (EMTs) play an important role in tissue construction during embryogenesis, and evidence suggests that this process may also help to remodel some adult tissues after injury. Activation of the hedgehog (Hh) signaling pathway regulates EMT during development. This pathway is also induced by chronic biliary injury, a condition in which EMT has been suggested to have a role. We evaluated the hypothesis that Hh signaling promotes EMT in adult bile ductular cells (cholangiocytes). In liver sections from patients with chronic biliary injury and in primary cholangiocytes isolated from rats that had undergone bile duct ligation (BDL), an experimental model of biliary fibrosis, EMT was localized to cholangiocytes with Hh pathway activity. Relief of ductal obstruction in BDL rats reduced Hh pathway activity, EMT, and biliary fibrosis. In mouse cholangiocytes, coculture with myofibroblastic hepatic stellate cells, a source of soluble Hh ligands, promoted EMT and cell migration. Addition of Hh-neutralizing antibodies to cocultures blocked these effects. Finally, we found that EMT responses to BDL were enhanced in patched-deficient mice, which display excessive activation of the Hh pathway. Together, these data suggest that activation of Hh signaling promotes EMT and contributes to the evolution of biliary fibrosis during chronic cholestasis.
Alessia Omenetti, Alessandro Porrello, Youngmi Jung, Liu Yang, Yury Popov, Steve S. Choi, Rafal P. Witek, Gianfranco Alpini, Juliet Venter, Hendrika M. Vandongen, Wing-Kin Syn, Gianluca Svegliati Baroni, Antonio Benedetti, Detlef Schuppan, Anna Mae Diehl
Apelin and its cognate G protein–coupled receptor APJ constitute a signaling pathway with a positive inotropic effect on cardiac function and a vasodepressor function in the systemic circulation. The apelin-APJ pathway appears to have opposing physiological roles to the renin-angiotensin system. Here we investigated whether the apelin-APJ pathway can directly antagonize vascular disease-related Ang II actions. In ApoE-KO mice, exogenous Ang II induced atherosclerosis and abdominal aortic aneurysm formation; we found that coinfusion of apelin abrogated these effects. Similarly, apelin treatment rescued Ang II–mediated increases in neointimal formation and vascular remodeling in a vein graft model. NO has previously been implicated in the vasodepressor function of apelin; we found that apelin treatment increased NO bioavailability in ApoE-KO mice. Furthermore, infusion of an NO synthase inhibitor blocked the apelin-mediated decrease in atherosclerosis and aneurysm formation. In rat primary aortic smooth muscle cells, apelin inhibited Ang II–mediated transcriptional regulation of multiple targets as measured by reporter assays. In addition, we demonstrated by coimmunoprecipitation and fluorescence resonance energy transfer analysis that the Ang II and apelin receptors interacted physically. Taken together, these findings indicate that apelin signaling can block Ang II actions in vascular disease by increasing NO production and inhibiting Ang II cellular signaling.
Hyung J. Chun, Ziad A. Ali, Yoko Kojima, Ramendra K. Kundu, Ahmad Y. Sheikh, Rani Agrawal, Lixin Zheng, Nicholas J. Leeper, Nathan E. Pearl, Andrew J. Patterson, Joshua P. Anderson, Philip S. Tsao, Michael J. Lenardo, Euan A. Ashley, Thomas Quertermous
The integrity of the endothelial monolayer is essential to blood vessel homeostasis and active regulation of endothelial permeability. The FGF system plays important roles in a wide variety of physiologic and pathologic conditions; however, its role in the adult vasculature has not been defined. To assess the role of the FGF system in the adult endothelial monolayer, we disrupted FGF signaling in bovine aortic endothelial cells and human saphenous vein endothelial cells in vitro and in adult mouse and rat endothelial cells in vivo using soluble FGF traps or a dominant inhibitor of all FGF receptors. The inhibition of FGF signaling using these approaches resulted in dissociation of the VE-cadherin/p120-catenin complex and disassembly of adherens and tight junctions, which progressed to loss of endothelial cells, severe impairment of the endothelial barrier function, and finally, disintegration of the vasculature. Thus, FGF signaling plays a key role in the maintenance of vascular integrity.
Masahiro Murakami, Loc T. Nguyen, Zhen W. Zhang, Karen L. Moodie, Peter Carmeliet, Radu V. Stan, Michael Simons
The underlying molecular mechanisms that cause immune cells, mediators of our defense system, to promote tumor invasion and angiogenesis remain incompletely understood. Constitutively activated Stat3 in tumor cells has been shown to promote tumor invasion and angiogenesis. Therefore, we sought to determine whether Stat3 activation in tumor-associated inflammatory cells has a similar function. We found that Stat3 signaling mediates multidirectional crosstalk among tumor cells, myeloid cells in the tumor stroma, and ECs that contributes to tumor angiogenesis in mice. Myeloid-derived suppressor cells and macrophages isolated from mouse tumors displayed activated Stat3 and induced angiogenesis in an in vitro tube formation assay via Stat3 induction of angiogenic factors, including VEGF and bFGF. Stat3-regulated factors produced by both tumor cells and tumor-derived myeloid cells also induced constitutive activation of Stat3 in tumor endothelium, and inhibiting Stat3 in ECs substantially reduced in vitro tumor factor–induced endothelial migration and tube formation. In vivo assays demonstrated the requirement for Stat3 signaling in tumor-associated myeloid cells for tumor angiogenesis. Our results indicate that, by virtue of the ability of Stat3 in tumor cells and tumor-derived myeloid cells to upregulate expression of factors that activate Stat3 in ECs, Stat3 mediates multidirectional crosstalk among tumor cells, tumor-associated myeloid cells, and ECs that contributes to tumor angiogenesis.
Maciej Kujawski, Marcin Kortylewski, Heehyoung Lee, Andreas Herrmann, Heidi Kay, Hua Yu
The progression from insulin resistance to type 2 diabetes is caused by the failure of pancreatic β cells to produce sufficient levels of insulin to meet the metabolic demand. Recent studies indicate that nutrient fluctuations and insulin resistance increase proinsulin synthesis in β cells beyond the capacity for folding of nascent polypeptides within the endoplasmic reticulum (ER) lumen, thereby disrupting ER homeostasis and triggering the unfolded protein response (UPR). Chronic ER stress promotes apoptosis, at least in part through the UPR-induced transcription factor C/EBP homologous protein (CHOP). We assessed the effect of Chop deletion in multiple mouse models of type 2 diabetes and found that Chop–/– mice had improved glycemic control and expanded β cell mass in all conditions analyzed. In both genetic and diet-induced models of insulin resistance, CHOP deficiency improved β cell ultrastructure and promoted cell survival. In addition, we found that isolated islets from Chop–/– mice displayed increased expression of UPR and oxidative stress response genes and reduced levels of oxidative damage. These findings suggest that CHOP is a fundamental factor that links protein misfolding in the ER to oxidative stress and apoptosis in β cells under conditions of increased insulin demand.
Benbo Song, Donalyn Scheuner, David Ron, Subramaniam Pennathur, Randal J. Kaufman
The final pathway of β cell destruction leading to insulin deficiency, hyperglycemia, and clinical type 1 diabetes is unknown. Here we show that circulating CTLs can kill β cells via recognition of a glucose-regulated epitope. First, we identified 2 naturally processed epitopes from the human preproinsulin signal peptide by elution from HLA-A2 (specifically, the protein encoded by the A*0201 allele) molecules. Processing of these was unconventional, requiring neither the proteasome nor transporter associated with processing (TAP). However, both epitopes were major targets for circulating effector CD8+ T cells from HLA-A2+ patients with type 1 diabetes. Moreover, cloned preproinsulin signal peptide–specific CD8+ T cells killed human β cells in vitro. Critically, at high glucose concentration, β cell presentation of preproinsulin signal epitope increased, as did CTL killing. This study provides direct evidence that autoreactive CTLs are present in the circulation of patients with type 1 diabetes and that they can kill human β cells. These results also identify a mechanism of self-antigen presentation that is under pathophysiological regulation and could expose insulin-producing β cells to increasing cytotoxicity at the later stages of the development of clinical diabetes. Our findings suggest that autoreactive CTLs are important targets for immune-based interventions in type 1 diabetes and argue for early, aggressive insulin therapy to preserve remaining β cells.
Ania Skowera, Richard J. Ellis, Ruben Varela-Calviño, Sefina Arif, Guo Cai Huang, Cassie Van-Krinks, Anna Zaremba, Chloe Rackham, Jennifer S. Allen, Timothy I.M. Tree, Min Zhao, Colin M. Dayan, Andrew K. Sewell, Wendy Unger, Jan W. Drijfhout, Ferry Ossendorp, Bart O. Roep, Mark Peakman
Tregs are important mediators of immune tolerance to self antigens, and it has been suggested that Treg inactivation may cause autoimmune disease. Therefore, immunotherapy approaches that aim to restore or expand autoantigen-specific Treg activity might be beneficial for the treatment of autoimmune disease. Here we report that Treg-mediated suppression of autoimmune disease can be achieved in vivo by taking advantage of the ability of the liver to promote immune tolerance. Expression of the neural autoantigen myelin basic protein (MBP) in the liver was accomplished stably in liver-specific MBP transgenic mice and transiently using gene transfer to liver cells in vivo. Such ectopic MBP expression induced protection from autoimmune neuroinflammation in a mouse model of multiple sclerosis. Protection from autoimmunity was mediated by MBP-specific CD4+CD25+Foxp3+ Tregs, as demonstrated by the ability of these cells to prevent disease when adoptively transferred into nontransgenic mice and to suppress conventional CD4+CD25– T cell proliferation after antigen-specific stimulation with MBP in vitro. The generation of MBP-specific CD4+CD25+Foxp3+ Tregs in vivo depended on expression of MBP in the liver, but not in skin, and occurred by TGF-β–dependent peripheral conversion from conventional non-Tregs. Our findings indicate that autoantigen expression in the liver may generate autoantigen-specific Tregs. Thus, targeting of autoantigens to hepatocytes may be a novel approach to prevention or treatment of autoimmune diseases.
Stefan Lüth, Samuel Huber, Christoph Schramm, Thorsten Buch, Stefan Zander, Christine Stadelmann, Wolfgang Brück, David C. Wraith, Johannes Herkel, Ansgar W. Lohse
Multiple sclerosis (MS) is a chronic inflammatory disease that results in demyelination in the central nervous system, and a defect in the regulatory function of CD4+CD25high T cells has been implicated in the pathogenesis of the disease. Here, we reanalyzed the function of this T cell subset in patients with MS, but we depleted cells expressing IL-7 receptor α-chain (CD127), a marker recently described as present on activated T cells but not Tregs. Similar to other studies, we observed a marked defect in the suppressive function of unseparated CD4+CD25high T cells isolated from MS patients. However, when CD127high cells were removed from the CD4+CD25high population, patient and control cells inhibited T cell proliferation and cytokine production equally. Likewise, when the CD25 gate used to sort the cells was stringent enough to eliminate CD127high cells, CD4+CD25high T cells from patients with MS and healthy individuals had similar regulatory function. Additional analysis indicated that the CD127high cells within the CD4+CD25high T cell population from patients with MS appeared more proliferative and secreted more IFN-γ and IL-2 than the same cells from healthy individuals. Taken together, we conclude that CD4+CD25highCD127low Tregs from MS patients and healthy individuals exhibit similar suppressive functions. The decreased inhibitory function of unfractioned CD4+CD25high cells previously observed might be due to abnormal activation of CD127high T cells in patients with MS.
Laure Michel, Laureline Berthelot, Ségolène Pettré, Sandrine Wiertlewski, Fabienne Lefrère, Cécile Braudeau, Sophie Brouard, Jean-Paul Soulillou, David-Axel Laplaud
EAE is a mouse T cell–mediated autoimmune disease of the CNS used to model the human condition MS. The contributions of B cells to EAE initiation and progression are unclear. In this study, we have shown that EAE disease initiation and progression are differentially influenced by the depletion of B cells from mice with otherwise intact immune systems. CD20 antibody–mediated B cell depletion before EAE induction substantially exacerbated disease symptoms and increased encephalitogenic T cell influx into the CNS. Increased symptom severity resulted from the depletion of a rare IL-10–producing CD1dhiCD5+ regulatory B cell subset (B10 cells), since the adoptive transfer of splenic B10 cells before EAE induction normalized EAE in B cell–depleted mice. While transfer of regulatory B10 cells was maximally effective during early EAE initiation, they had no obvious role during disease progression. Rather, B cell depletion during EAE disease progression dramatically suppressed symptoms. Specifically, B cells were required for the generation of CD4+ T cells specific for CNS autoantigen and the entry of encephalitogenic T cells into the CNS during disease progression. These results demonstrate reciprocal regulatory roles for B cells during EAE immunopathogenesis. The therapeutic effect of B cell depletion for the treatment of autoimmunity may therefore depend on the relative contributions and the timing of these opposing B cell activities during the course of disease initiation and pathogenesis.
Takashi Matsushita, Koichi Yanaba, Jean-David Bouaziz, Manabu Fujimoto, Thomas F. Tedder
Plasmacytoid DCs (pDCs) have been implicated as crucial cells in antiviral immune responses. On recognizing HIV, they become activated, secreting large amounts of IFN-α and inflammatory cytokines, thereby potentiating innate and adaptive antiviral immune responses. Here, we have shown that HIV-stimulated human pDCs can also induce the differentiation of naive CD4+ T cells into Tregs with suppressive function. This differentiation was independent of pDC production of IFN-α and primarily dependent on pDC expression of indoleamine 2,3-dioxygenase, which was induced through the TLR/MyD88 pathway, following binding of HIV to CD4 and triggering of TLR7 by HIV genomic RNA. Functionally, the Tregs induced by pDCs were shown to inhibit the maturation of bystander conventional DCs. This study therefore reveals what we believe to be a novel mechanism by which pDC may regulate and potentially limit anti-HIV immune responses.
Olivier Manches, David Munn, Anahita Fallahi, Jeffrey Lifson, Laurence Chaperot, Joel Plumas, Nina Bhardwaj
Genital coinfections increase an individual’s risk of becoming infected with HIV-1 by sexual contact. Several mechanisms have been proposed to explain this, such as the presence of ulceration and bleeding caused by the coinfecting pathogen. Here we demonstrate that Langerhans cells (LCs) are involved in the increased susceptibility to HIV-1 in the presence of genital coinfections. Although LCs are a target for HIV-1 infection in genital tissues, we found that immature LCs did not efficiently mediate HIV-1 transmission in an ex vivo human skin explant model. However, the inflammatory stimuli TNF-α and Pam3CysSerLys4 (Pam3CSK4), the ligand for the TLR1/TLR2 heterodimer, strongly increased HIV-1 transmission by LCs through distinct mechanisms. TNF-α enhanced transmission by increasing HIV-1 replication in LCs, whereas Pam3CSK4 acted by increasing LC capture of HIV-1 and subsequent trans-infection of T cells. Genital infections such as Candida albicans and Neisseria gonorrhea not only triggered TLRs but also induced TNF-α production in vaginal and skin explants. Thus, during coinfection, LCs could be directly activated by pathogenic structures and indirectly activated by inflammatory factors, thereby increasing the risk of acquiring HIV-1. Our data demonstrate a decisive role for LCs in HIV-1 transmission during genital coinfections and suggest antiinflammatory therapies as potential strategies to prevent HIV-1 transmission.
Marein A.W.P. de Jong, Lot de Witte, Menno J. Oudhoff, Sonja I. Gringhuis, Philippe Gallay, Teunis B.H. Geijtenbeek
Women with antiphospholipid syndrome (APS), a condition characterized by the presence of antiphospholipid antibodies (aPL), often suffer pregnancy-related complications, including miscarriage. We have previously shown that C5a induction of tissue factor (TF) expression in neutrophils contributes to respiratory burst, trophoblast injury, and pregnancy loss in mice treated with aPL. Here we analyzed how TF contributes to neutrophil activation and trophoblast injury in this model. Neutrophils from aPL-treated mice expressed protease-activated receptor 2 (PAR2), and stimulation of this receptor led to neutrophil activation, trophoblast injury, and fetal death. An antibody specific for human TF that has little impact on coagulation, but potently inhibits TF/Factor VIIa (FVIIa) signaling through PAR2, inhibited aPL-induced neutrophil activation in mice that expressed human TF. Genetic deletion of the TF cytoplasmic domain, which allows interaction between TF and PAR2, reduced aPL-induced neutrophil activation in aPL-treated mice. Par2–/– mice treated with aPL exhibited reduced neutrophil activation and normal pregnancies, which indicates that PAR2 plays an important role in the pathogenesis of aPL-induced fetal injury. We also demonstrated that simvastatin and pravastatin decreased TF and PAR2 expression on neutrophils and prevented pregnancy loss. Our results suggest that TF/FVIIa/PAR2 signaling mediates neutrophil activation and fetal death in APS and that statins may be a good treatment for women with aPL-induced pregnancy complications.
Patricia Redecha, Claus-Werner Franzke, Wolfram Ruf, Nigel Mackman, Guillermina Girardi
Asthma is a complex heritable disease that is increasing in prevalence and severity, particularly in developed countries such as the United States, where 11% of the population is affected. The contribution of environmental and genetic factors to this growing epidemic is currently not well understood. We developed the hypothesis, based on previous literature, that changes in DNA methylation resulting in aberrant gene transcription may enhance the risk of developing allergic airway disease. Our findings indicate that in mice, a maternal diet supplemented with methyl donors enhanced the severity of allergic airway disease that was inherited transgenerationally. Using a genomic approach, we discovered 82 gene-associated loci that were differentially methylated after in utero supplementation with a methyl-rich diet. These methylation changes were associated with decreased transcriptional activity and increased disease severity. Runt-related transcription factor 3 (Runx3), a gene known to negatively regulate allergic airway disease, was found to be excessively methylated, and Runx3 mRNA and protein levels were suppressed in progeny exposed in utero to a high-methylation diet. Moreover, treatment with a demethylating agent increased Runx3 gene transcription, further supporting our claim that a methyl-rich diet can affect methylation status and consequent transcriptional regulation. Our findings indicate that dietary factors can modify the heritable risk of allergic airway disease through epigenetic mechanisms during a vulnerable period of fetal development in mice.
John W. Hollingsworth, Shuichiro Maruoka, Kathy Boon, Stavros Garantziotis, Zhuowei Li, John Tomfohr, Nathaniel Bailey, Erin N. Potts, Gregory Whitehead, David M. Brass, David A. Schwartz
Herpes simplex virus type 1 (HSV-1) infection is the most common cause of sporadic, fatal encephalitis, but current understanding of how the virus interacts with cellular factors to regulate disease progression is limited. Here, we show that HSV-1 infection induced the expression of the cellular transcription factor early growth response 1 (Egr-1) in a human neuronal cell line. Egr-1 increased viral replication by activating promoters of viral productive cycle genes through binding to its corresponding sequences in the viral promoters. Mouse studies confirmed that Egr-1 expression was enhanced in HSV-1–infected brains and that Egr-1 functions to promote viral replication in embryonic fibroblasts. Furthermore, Egr-1 deficiency or knockdown of Egr-1 by a DNA-based enzyme greatly reduced the mortality of HSV-1–infected mice by decreasing viral loads in tissues. This study provides what we believe is the first evidence that Egr-1 increases the mortality of HSV-1 encephalitis by enhancing viral replication. Moreover, blocking this cellular machinery exploited by the virus could prevent host mortality.
Shih-Heng Chen, Hui-Wen Yao, I-Te Chen, Biehuoy Shieh, Ching Li, Shun-Hua Chen
The threat of avian influenza A (H5N1) infection in humans remains a global health concern. Current influenza vaccines stimulate antibody responses against the surface glycoproteins but are ineffective against strains that have undergone significant antigenic variation. An alternative approach is to stimulate pre-existing memory T cells established by seasonal human influenza A infection that could cross-react with H5N1 by targeting highly conserved internal proteins. To determine how common cross-reactive T cells are, we performed a comprehensive ex vivo analysis of cross-reactive CD4+ and CD8+ memory T cell responses to overlapping peptides spanning the full proteome of influenza A/Viet Nam/CL26/2005 (H5N1) and influenza A/New York/232/2004 (H3N2) in healthy individuals from the United Kingdom and Viet Nam. Memory CD4+ and CD8+ T cells isolated from the majority of participants exhibited human influenza–specific responses and showed cross-recognition of at least one H5N1 internal protein. Participant CD4+ and CD8+ T cells recognized multiple synthesized influenza peptides, including peptides from the H5N1 strain. Matrix protein 1 (M1) and nucleoprotein (NP) were the immunodominant targets of cross-recognition. In addition, cross-reactive CD4+ and CD8+ T cells recognized target cells infected with recombinant vaccinia viruses expressing either H5N1 M1 or NP. Thus, vaccine formulas inducing heterosubtypic T cell–mediated immunity may confer broad protection against avian and human influenza A viruses.
Laurel Yong-Hwa Lee, Do Lien Anh Ha, Cameron Simmons, Menno D. de Jong, Nguyen Van Vinh Chau, Reto Schumacher, Yan Chun Peng, Andrew J. McMichael, Jeremy J. Farrar, Geoffrey L. Smith, Alain R.M. Townsend, Brigitte A. Askonas, Sarah Rowland-Jones, Tao Dong
In acute inflammation, infiltrating polymorphonuclear leukocytes (also known as PMNs) release preformed granule proteins having multitudinous effects on the surrounding environment. Here we present what we believe to be a novel role for PMN-derived proteins in bacterial phagocytosis by both human and murine macrophages. Exposure of macrophages to PMN secretion markedly enhanced phagocytosis of IgG-opsonized Staphylococcus aureus both in vitro and in murine models in vivo. PMN secretion activated macrophages, resulting in upregulation of the Fcγ receptors CD32 and CD64, which then mediated the enhanced phagocytosis of IgG-opsonized bacteria. The phagocytosis-stimulating activity within the PMN secretion was found to be due to proteins released from PMN primary granules; thorough investigation revealed heparin-binding protein (HBP) and human neutrophil peptides 1–3 (HNP1–3) as the mediators of the macrophage response to PMN secretion. The use of blocking antibodies and knockout mice revealed that HBP acts via β2 integrins, but the receptor for HNP1–3 remained unclear. Mechanistically, HBP and HNP1–3 triggered macrophage release of TNF-α and IFN-γ, which acted in an autocrine loop to enhance expression of CD32 and CD64 and thereby enhance phagocytosis. Thus, we attribute what may be a novel role for PMN granule proteins in regulating the immune response to bacterial infections.
Oliver Soehnlein, Ylva Kai-Larsen, Robert Frithiof, Ole E. Sorensen, Ellinor Kenne, Karin Scharffetter-Kochanek, Einar E. Eriksson, Heiko Herwald, Birgitta Agerberth, Lennart Lindbom
Emerging metabolomic tools have created the opportunity to establish metabolic signatures of myocardial injury. We applied a mass spectrometry–based metabolite profiling platform to 36 patients undergoing alcohol septal ablation treatment for hypertrophic obstructive cardiomyopathy, a human model of planned myocardial infarction (PMI). Serial blood samples were obtained before and at various intervals after PMI, with patients undergoing elective diagnostic coronary angiography and patients with spontaneous myocardial infarction (SMI) serving as negative and positive controls, respectively. We identified changes in circulating levels of metabolites participating in pyrimidine metabolism, the tricarboxylic acid cycle and its upstream contributors, and the pentose phosphate pathway. Alterations in levels of multiple metabolites were detected as early as 10 minutes after PMI in an initial derivation group and were validated in a second, independent group of PMI patients. A PMI-derived metabolic signature consisting of aconitic acid, hypoxanthine, trimethylamine N-oxide, and threonine differentiated patients with SMI from those undergoing diagnostic coronary angiography with high accuracy, and coronary sinus sampling distinguished cardiac-derived from peripheral metabolic changes. Our results identify a role for metabolic profiling in the early detection of myocardial injury and suggest that similar approaches may be used for detection or prediction of other disease states.
Gregory D. Lewis, Ru Wei, Emerson Liu, Elaine Yang, Xu Shi, Maryann Martinovic, Laurie Farrell, Aarti Asnani, Marcoli Cyrille, Arvind Ramanathan, Oded Shaham, Gabriel Berriz, Patricia A. Lowry, Igor F. Palacios, Murat Taşan, Frederick P. Roth, Jiangyong Min, Christian Baumgartner, Hasmik Keshishian, Terri Addona, Vamsi K. Mootha, Anthony Rosenzweig, Steven A. Carr, Michael A. Fifer, Marc S. Sabatine, Robert E. Gerszten