NLR inflammasomes, caspase 1 activation platforms critical for processing key pro-inflammatory cytokines, have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). As the ...direct role of the NLRP3 inflammasome remains unclear, we tested effects of persistent NLRP3 activation as a contributor to NAFLD development and, in particular, as a modulator of progression from benign hepatic steatosis to steatohepatitis during diet-induced NAFLD. Gain of function tamoxifen-inducible
Nlrp3
knock-in mice allowing for in vivo temporal control of NLRP3 activation and loss of function
Nlrp3
knockout mice were placed on short-term choline-deficient amino acid-defined (CDAA) diet, to induce isolated hepatic steatosis or long-term CDAA exposure, to induce severe steatohepatitis and fibrosis, respectively. Expression of NLRP3 associated proteins was assessed in liver biopsies of a well-characterized group of patients with the full spectrum of NAFLD.
Nlrp3
−/−
mice were protected from long-term feeding CDAA-induced hepatomegaly, liver injury, and infiltration of activated macrophages. More importantly,
Nlrp3
−/−
mice showed marked protection from CDAA-induced liver fibrosis. After 4 weeks on CDAA diet, wild-type (WT) animals showed isolated hepatic steatosis while
Nlrp3
knock-in mice showed severe liver inflammation, with increased infiltration of activated macrophages and early signs of liver fibrosis. In the liver samples of patients with NAFLD, inflammasome components were significantly increased in those patients with nonalcoholic steatohepatitis (NASH) when compared to those with non-NASH NAFLD with mRNA levels of pro-IL1 beta correlated to levels of COL1A1. Our study uncovers a crucial role for the NLRP3 inflammasome in the development of NAFLD. These findings may lead to novel therapeutic strategies aimed at halting the progression of hepatic steatosis to the more severe forms of this disease.
Key message
Mice with NLRP3 inflammasome loss of function are protected from diet-induced steatohepatitis.
NLRP3 inflammasome gain of function leads to early and severe onset of diet-induced steatohepatitis in mice.
Patients with severe NAFLD exhibit increased levels of NLRP3 inflammasome components and levels of pro-IL1β mRNA correlate with the expression of COL1A1.
Autoinflammatory diseases are monogenic and polygenic disorders due to dysregulation of the innate immune system. The inherited conditions have been clustered with primary immunodeficiencies in the ...latest practice parameters; however, these diseases have unique clinical presentations, genetics, and available therapies. Given the presentation of fevers, rashes, and mucosal symptoms observed in many of these syndromes, patients are likely to present to an allergist/immunologist. Although there has been attention in the literature to diagnosis and treatment of rare, genetically defined autoinflammatory disorders, physicians are challenged by increasing numbers of patients with intermittent or periodic fevers who face unnecessary morbidities due to a lack of a diagnosis. The broad differential of diseases presenting with fever includes autoinflammatory syndromes, infections associated with immunodeficiency and/or allergies complicated by infection, and less commonly, autoimmune disorders or malignancy. To address this challenge, we review the history of the medical approach to fever, current diagnostic paradigms, and controversies in management. We describe the spectrum of disorders referred to a recurrent fever disorders clinic established in an Allergy/Immunology division at a tertiary pediatric care center. Finally, we provide practical recommendations including historical features and initial laboratory investigations that can help clinicians appropriately manage these patients.
NAFLD has evolved as a serious public health problem in the USA and around the world. In fact, NASH-the most serious form of NAFLD-is predicted to become the leading cause of liver transplantation in ...the USA by the year 2020. The pathogenesis of NAFLD and NASH, in particular the mechanisms responsible for liver injury and fibrosis, is the result of a complex interplay between host and environmental factors, and is at the centre of intense investigation. In this Review, we focus on recently uncovered aspects of the genetic, biochemical, immunological and molecular events that are responsible for the development and progression of this highly prevalent and potentially serious disease. These studies bring new insight into this complex disorder and have led to the development of novel therapeutic and diagnostic strategies that might enable a personalized approach in the management of this disease.
The NLR family pyrin domain‐containing 3 (NLRP3) inflammasome plays an important role in liver fibrosis (LF) development. However, the mechanisms involved in NLRP3‐induced fibrosis are unclear. Our ...aim was to test the hypothesis that the NLRP3 inflammasome in hepatic stellate cells (HSCs) can directly regulate their activation and contribute to LF. Primary HSCs isolated from wild‐type (WT), Nlrp3–/–, or Nlrp3L351PneoR knock‐in crossed to inducible (estrogen receptor Cre‐CreT) mice were incubated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP), or 4OH‐tamoxifen, respectively. HSC‐specific Nlrp3L351P knock‐in mice were generated by crossing transgenic mice expressing lecithin retinol acyltransferase (Lrat)‐driven Cre and maintained on standard rodent chow for 6 months. Mice were then sacrificed; liver tissue and serum were harvested. Nlrp3 inflammasome activation along with HSC phenotype and fibrosis were assessed by RT‐PCR, western blotting, fluorescence‐activated cell sorting (FACS), enzyme‐linked immunosorbent assay, immunofluorescence (IF), and immunohistochemistry (IHC). Stimulated WT HSCs displayed increased levels of NLRP3 inflammasome‐induced reactive oxygen species (ROS) production and cathepsin B activity, accompanied by an up‐regulation of mRNA and protein levels of fibrotic makers, an effect abrogated in Nlrp3–/– HSCs. Nlrp3L351P CreT HSCs also showed elevated mRNA and protein expression of fibrotic markers 24 hours after inflammasome activation induced with 4‐hydroxytamoxifen (4OHT). Protein and mRNA expression levels of fibrotic markers were also found to be increased in isolated HSCs and whole liver tissue from Nlrp3L351P Lrat Cre mice compared to WT. Liver sections from 24‐week‐old NlrpL351P Lrat Cre mice showed fibrotic changes with increased alpha smooth muscle actin (αSMA) and desmin‐positive cells and collagen deposition, independent of inflammatory infiltrates; these changes were also observed after LPS challenge in 8‐week‐old NlrpL351P Lrat Cre mice. Conclusion: Our results highlight a direct role for the NLRP3 inflammasome in the activation of HSCs directly triggering LF.
Neutrophils are the first line of defense against bacteria and fungi and help combat parasites and viruses. They are necessary for mammalian life, and their failure to recover after myeloablation is ...fatal. Neutrophils are short-lived, effective killing machines. Their life span is significantly extended under infectious and inflammatory conditions. Neutrophils take their cues directly from the infectious organism, from tissue macrophages and other elements of the immune system. Here, we review how neutrophils traffic to sites of infection or tissue injury, how they trap and kill bacteria, how they shape innate and adaptive immune responses, and the pathophysiology of monogenic neutrophil disorders.
The NLRP3 inflammasome, a caspase‐1 activation platform, plays a key role in the modulation of liver inflammation and fibrosis. Here, we tested the hypothesis that interleukin 17 (IL‐17) and tumor ...necrosis factor (TNF) are key cytokines involved in amplifying and perpetuating the liver damage and fibrosis resulting from NLRP3 activation. To address this hypothesis, gain‐of‐function Nlrp3A350V knock‐in mice were bred onto il17a and Tnf knockout backgrounds allowing for constitutive Nlrp3 activation in myeloid derived cells in mice deficient in IL‐17 or TNF. Livers of Nlrp3A350V knock‐in mice exhibited severe liver inflammatory changes characterized by infiltration with neutrophils, increased expression of chemokine (C‐X‐C motif) ligand (CXCL) 1 and CXCL2 chemokines, activated inflammatory macrophages, and elevated levels of IL‐17 and TNF. Mutants with ablation of il17a signal showed fewer neutrophils when compared to intact Nlrp3A350V mutants, but still significant inflammatory changes when compared to the nonmutant il17a knockout littermates. The severe inflammatory changes associated with mutant Nlrp3 were almost completely rescued by Tnf knockout in association with a marked decrease in circulating IL‐1β levels. Intact Nlrp3A350Vmutants showed changes in liver fibrosis, as evidenced by morphometric quantitation of Sirius Red staining and increased mRNA levels of profibrotic genes, including connective tissue growth factor and tissue inhibitor of matrix metalloproteinase 1. Il17a lacking mutants exhibited amelioration of the aforementioned fibrosis, whereas Tnf‐deficient mutants showed no signs of fibrosis when compared to littermate controls. Conclusion: Our study uncovers key roles for TNF and, to a lesser extent, IL‐17 as mediators of liver inflammation and fibrosis induced by constitutive NLRP3 inflammasome activation in myeloid‐derived cells. These findings may lead to therapeutic strategies aimed at halting the progression of liver injury and fibrogenesis in various liver pathogeneses driven by NLRP3 activation. (Hepatology 2018;67:736‐749).
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