Fibroproliferative diseases are driven by dysregulated tissue repair responses and are a major cause of morbidity and mortality because they affect nearly every organ system. Type 2 cytokine ...responses are critically involved in tissue repair; however, the mechanisms that regulate beneficial regeneration versus pathological fibrosis are not well understood. Here, we have shown that the type 2 effector cytokine interleukin-13 simultaneously, yet independently, directed hepatic fibrosis and the compensatory proliferation of hepatocytes and biliary cells in progressive models of liver disease induced by interleukin-13 overexpression or after infection with Schistosoma mansoni. Using transgenic mice with interleukin-13 signaling genetically disrupted in hepatocytes, cholangiocytes, or resident tissue fibroblasts, we have revealed direct and distinct roles for interleukin-13 in fibrosis, steatosis, cholestasis, and ductular reaction. Together, these studies show that these mechanisms are simultaneously controlled but distinctly regulated by interleukin-13 signaling. Thus, it may be possible to promote interleukin-13-dependent hepatobiliary expansion without generating pathological fibrosis.
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•Type 2 cell-mediated fibrosis and regeneration are independently regulated by IL-13•Pathological fibrosis is driven by direct IL-13 signaling in PDGFRB+ fibroblasts•IL-13 stimulates hepatobiliary progenitor cells and cholangiocytes to proliferate•IL-13 regulates lipogenesis, bile acid synthesis, and biliary-dependent steatosis
Fibroproliferative diseases will affect nearly half of the global population and result in significant loss of quality of life due to comorbidities. In this work, Wynn and colleagues demonstrate that the type 2 cytokine interleukin-13 signals through distinct cellular pathways to simultaneously drive hepatic regeneration, fibrosis, ductular reaction, cholestasis, and steatosis.
Thymic stromal lymphopoietin (TSLP), interleukin-25 (IL-25), and IL-33 are important initiators of type 2-associated mucosal inflammation and immunity. However, their role in the maintenance of ...progressive type 2 inflammation and fibrosis is much less clear. Using chronic models of helminth infection and allergic lung inflammation, we show that collective disruption of TSLP, IL-25, and IL-33 signaling suppresses chronic and progressive type 2 cytokine-driven inflammation and fibrosis. In a schistosome lung granuloma model or during chronic Schistosoma mansoni infection in the liver, individual ablation of TSLP, IL-25, or IL-33/ST2 had no impact on the development of IL-4/IL-13-dependent inflammation or fibrosis. However, significant reductions in granuloma-associated eosinophils, hepatic fibrosis, and IL-13-producing type 2 innate lymphoid cells (ILC2s) were observed when signaling of all three mediators was simultaneously disrupted. Combined blockade through monoclonal antibody (mAb) treatment also reduced IL-5 and IL-13 expression during primary and secondary granuloma formation in the lungs. In a model of chronic house dust mite-induced allergic lung inflammation, combined mAb treatment did not decrease established inflammation or fibrosis. TSLP/IL-33 double-knockout mice treated with anti-IL-25 mAb during priming, however, displayed decreased inflammation, mucus production, and lung remodeling in the chronic phase. Together, these studies reveal partially redundant roles for TSLP, IL-25, and IL-33 in the maintenance of type 2 pathology and suggest that in some settings, early combined targeting of these mediators is necessary to ameliorate progressive type 2-driven disease.
Mice expressing a Cre recombinase from the lysozyme M-encoding locus (Lyz2) have been widely used to dissect gene function in macrophages and neutrophils. Here, we show that while naïve resident ...tissue macrophages from IL-4Rαf(lox/delta)LysM(Cre) mice almost completely lose IL-4Rα function, a large fraction of macrophages elicited by sterile inflammatory stimuli, Schistosoma mansoni eggs, or S. mansoni infection, fail to excise Il4rα. These F4/80(hi)CD11b(hi) macrophages, in contrast to resident tissue macrophages, express lower levels of Lyz2 explaining why this population resists LysM(Cre)-mediated deletion. We show that in response to IL-4 and IL-13, Lyz2(lo)IL-4Rα(+) macrophages differentiate into an arginase 1-expressing alternatively-activated macrophage (AAM) population, which slows the development of lethal fibrosis in schistosomiasis. In contrast, we identified Lyz2(hi)IL-4Rα(+) macrophages as the key subset of AAMs mediating the downmodulation of granulomatous inflammation in chronic schistosomiasis. Our observations reveal a limitation on using a LysMCre mouse model to study gene function in inflammatory settings, but we utilize this limitation as a means to demonstrate that distinct populations of alternatively activated macrophages control inflammation and fibrosis in chronic schistosomiasis.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Acidic mammalian chitinase (AMCase) is known to be induced by allergens and helminths, yet its role in immunity is unclear. Using AMCase-deficient mice, we show that AMCase deficiency reduced the ...number of group 2 innate lymphoid cells during allergen challenge but was not required for establishment of type 2 inflammation in the lung in response to allergens or helminths. In contrast, AMCase-deficient mice showed a profound defect in type 2 immunity following infection with the chitin-containing gastrointestinal nematodes Nippostrongylus brasiliensis and Heligmosomoides polygyrus bakeri. The impaired immunity was associated with reduced mucus production and decreased intestinal expression of the signature type 2 response genes Il13, Chil3, Retnlb, and Clca1. CD103(+) dendritic cells, which regulate T cell homing, were also reduced in mesenteric lymph nodes of infected AMCase-deficient mice. Thus, AMCase functions as a critical initiator of protective type 2 responses to intestinal nematodes but is largely dispensable for allergic responses in the lung.
Increasing evidence suggests that asthma is a heterogeneous disorder regulated by distinct molecular mechanisms. In a cross-sectional study of asthmatics of varying severity (n = 51), endobronchial ...tissue gene expression analysis revealed three major patient clusters: TH2-high, TH17-high, and TH2/17-low. TH2-high and TH17-high patterns were mutually exclusive in individual patient samples, and their gene signatures were inversely correlated and differentially regulated by interleukin-13 (IL-13) and IL-17A. To understand this dichotomous pattern of T helper 2 (TH2) and TH17 signatures, we investigated the potential of type 2 cytokine suppression in promoting TH17 responses in a preclinical model of allergen-induced asthma. Neutralization of IL-4 and/or IL-13 resulted in increased TH17 cells and neutrophilic inflammation in the lung. However, neutralization of IL-13 and IL-17 protected mice from eosinophilia, mucus hyperplasia, and airway hyperreactivity and abolished the neutrophilic inflammation, suggesting that combination therapies targeting both pathways may maximize therapeutic efficacy across a patient population comprising both TH2 and TH17 endotypes.
Evaluating the pathogenicity of a variant is challenging given the plethora of types of genetic evidence that laboratories consider. Deciding how to weigh each type of evidence is difficult, and ...standards have been needed. In 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published guidelines for the assessment of variants in genes associated with Mendelian diseases. Nine molecular diagnostic laboratories involved in the Clinical Sequencing Exploratory Research (CSER) consortium piloted these guidelines on 99 variants spanning all categories (pathogenic, likely pathogenic, uncertain significance, likely benign, and benign). Nine variants were distributed to all laboratories, and the remaining 90 were evaluated by three laboratories. The laboratories classified each variant by using both the laboratory’s own method and the ACMG-AMP criteria. The agreement between the two methods used within laboratories was high (K-alpha = 0.91) with 79% concordance. However, there was only 34% concordance for either classification system across laboratories. After consensus discussions and detailed review of the ACMG-AMP criteria, concordance increased to 71%. Causes of initial discordance in ACMG-AMP classifications were identified, and recommendations on clarification and increased specification of the ACMG-AMP criteria were made. In summary, although an initial pilot of the ACMG-AMP guidelines did not lead to increased concordance in variant interpretation, comparing variant interpretations to identify differences and having a common framework to facilitate resolution of those differences were beneficial for improving agreement, allowing iterative movement toward increased reporting consistency for variants in genes associated with monogenic disease.
Nonalcoholic fatty liver disease (NAFLD) is now the most common progressive liver disease in developed countries and is the second leading indication for liver transplantation due to the extensive ...fibrosis it causes. NAFLD progression is thought to be tied to chronic low-level type 1 inflammation originating in the adipose tissue during obesity; however, the specific immunological mechanisms regulating the progression of NAFLD-associated fibrosis in the liver are unclear. To investigate the immunopathogenesis of NAFLD more completely, we investigated adipose dysfunction, nonalcoholic steatohepatitis (NASH), and fibrosis in mice that develop polarized type 1 or type 2 immune responses. Unexpectedly, obese interleukin-10 (IL-10)/IL-4-deficient mice (type 1-polarized) were highly resistant to NASH. This protection was associated with an increased hepatic interferon-γ (IFN-γ) signature. Conversely, IFN-γ-deficient mice progressed rapidly to NASH with evidence of fibrosis dependent on transforming growth factor-β (TGF-β) and IL-13 signaling. Unlike increasing type 1 inflammation and the marked loss of eosinophils seen in expanding adipose tissue, progression of NASH was associated with increasing eosinophilic type 2 liver inflammation in mice and human patient biopsies. Finally, simultaneous inhibition of TGF-β and IL-13 signaling attenuated the fibrotic machinery more completely than TGF-β alone in NAFLD-associated fibrosis. Thus, although type 2 immunity maintains healthy metabolic signaling in adipose tissues, it exacerbates the progression of NAFLD collaboratively with TGF-β in the liver.
Persistent or dysregulated IL‐13 responses are key drivers of fibrosis in multiple organ systems, and this identifies this cytokine as an important therapeutic target. Nevertheless, the mechanisms by ...which IL‐13 blockade leads to the amelioration of fibrosis remain unclear. Because IFN‐γ exhibits potent anti‐fibrotic activity, and IL‐4Rα signalling antagonizes IFN‐γ effector function, compensatory increases in IFN‐γ activity following IL‐13/IL‐4Rα blockade might contribute to the reduction in fibrosis. To investigate the role of IFN‐γ, we developed novel IL‐13−/−/IFN‐γ−/− double cytokine‐deficient mice and examined disease progression in models of type 2‐driven fibrosis. As predicted, we showed that fibrosis in the lung and liver are both highly dependent on IL‐13. We also observed increased IFN‐γ production and inflammatory activity in the tissues of IL‐13‐deficient mice. Surprisingly, however, an even greater reduction in fibrosis was observed in IL‐13/IFN‐γ double deficient mice, most notably in the livers of mice chronically infected with Schistosoma mansoni. The increased protection was associated with marked decreases in Tgfb1, Mmp12, and Timp1 mRNA expression in the tissues; reduced inflammation; and decreased expression of important pro‐inflammatory mediators such as TNF‐α. Experiments conducted with neutralizing monoclonal antibodies to IL‐13 and IFN‐γ validated the findings with the genetically deficient mice. Together, these studies demonstrate that the reduction in fibrosis observed when IL‐13 signalling is suppressed is not dependent on increased IFN‐γ activity. Instead, by reducing compensatory increases in type 1‐associated inflammation, therapeutic strategies that block IFN‐γ and IL‐13 activity simultaneously can confer greater protection from progressive fibrosis than IL‐13 blockade alone. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
The primary muscle disorders are a diverse group of diseases caused by various defective structural proteins, abnormal signaling molecules, enzymes and proteins involved in posttranslational ...modifications, and other mechanisms. Although there is increasing clarification of the primary aberrant cellular processes responsible for these conditions, the decisive factors involved in the secondary pathogenic cascades are still mainly obscure. Given the emerging roles of microRNAs (miRNAs) in modulation of cellular phenotypes, we searched for miRNAs regulated during the degenerative process of muscle to gain insight into the specific regulation of genes that are disrupted in pathological muscle conditions. We describe 185 miRNAs that are up- or down-regulated in 10 major muscular disorders in humans Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, facioscapulohumeral muscular dystrophy, limb-girdle muscular dystrophies types 2A and 2B, Miyoshi myopathy, nemaline myopathy, polymyositis, dermatomyositis, and inclusion body myositis. Although five miRNAs were found to be consistently regulated in almost all samples analyzed, pointing to possible involvement of a common regulatory mechanism, others were dysregulated only in one disease and not at all in the other disorders. Functional correlation between the predicted targets of these miRNAs and mRNA expression demonstrated tight posttranscriptional regulation at the mRNA level in DMD and Miyoshi myopathy. Together with direct mRNA-miRNA predicted interactions demonstrated in DMD, some of which are involved in known secondary response functions and others that are involved in muscle regeneration, these findings suggest an important role of miRNAs in specific physiological pathways underlying the disease pathology.
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