ABSTRACT
Activation of the NLRP3 inflammasome and subsequent maturation of IL-1ß have been implicated in acute lung injury (ALI), resulting in inflammation and fibrosis. We investigated the role of vimentin, a type III intermediate filament, in this process using three well-characterized murine models of ALI known to require NLRP3 inflammasome activation. We demonstrate that central pathophysiologic events in ALI (inflammation, IL-1ß levels, endothelial and alveolar epithelial barrier permeability, remodelling and fibrosis) are attenuated in the lungs of Vim(-/-) mice challenged with LPS, bleomycin and asbestos. Bone marrow chimeric mice lacking vimentin have reduced IL-1ß levels and attenuated lung injury and fibrosis following bleomycin exposure. Furthermore, decreased active caspase-1 and IL-1ß levels are observed in vitro in Vim(-/-) and vimentin-knockdown macrophages. Importantly, we show direct protein-protein interaction between NLRP3 and vimentin. This study provides insights into lung inflammation and fibrosis and suggests that vimentin may be a key regulator of the NLRP3 inflammasome.
Subject(s)
Carrier Proteins/metabolism , Inflammasomes/metabolism , Inflammation/metabolism , Vimentin/metabolism , Acute Lung Injury/metabolism , Animals , Bleomycin/chemistry , Bone Marrow Cells/cytology , Bronchoalveolar Lavage Fluid , Cell Line , Cell Proliferation , Female , Fibrosis , Interleukin-1beta/metabolism , Lung/metabolism , Lung/pathology , Macrophages/metabolism , Male , Mice , Mice, Knockout , Microscopy, Atomic Force , NLR Family, Pyrin Domain-Containing 3 Protein , Protein Interaction MappingABSTRACT
Inflammation is essential for host defense but can cause tissue damage and organ failure if unchecked. How the inflammation is resolved remains elusive. Here we report that the transcription factor Miz1 was required for terminating lipopolysaccharide (LPS)-induced inflammation. Genetic disruption of the Miz1 POZ domain, which is essential for the transactivation or repression activity of Miz1, resulted in hyperinflammation, lung injury and greater mortality in LPS-treated mice but a lower bacterial load and mortality in mice with Pseudomonas aeruginosa pneumonia. Loss of the Miz1 POZ domain prolonged the expression of proinflammatory cytokines. After stimulation, Miz1 was phosphorylated at Ser178, which was required for recruitment of the histone deacetylase HDAC1 to repress transcription of the gene encoding C/EBP-δ, an amplifier of inflammation. Our data provide a long-sought mechanism underlying the resolution of LPS-induced inflammation.
Subject(s)
Acute Lung Injury/immunology , CCAAT-Enhancer-Binding Protein-delta/metabolism , Nuclear Proteins/metabolism , Protein Inhibitors of Activated STAT/metabolism , Pseudomonas Infections/immunology , Pseudomonas aeruginosa/immunology , Acute Lung Injury/genetics , Animals , Cytokines/metabolism , Enzyme Repression/genetics , Histone Deacetylase 1/metabolism , Immune Tolerance , Inflammation/genetics , Inflammation Mediators/metabolism , Lipopolysaccharides/immunology , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Mutagenesis, Site-Directed , Neoplasm Proteins/genetics , Nuclear Proteins/genetics , Phosphorylation , Protein Inhibitors of Activated STAT/genetics , Pseudomonas Infections/genetics , Repressor Proteins/genetics , Transcriptional Activation/genetics , Ubiquitin-Protein LigasesABSTRACT
Elevated concentrations of CO2 (hypercapnia) lead to alveolar epithelial dysfunction by promoting Na,K-ATPase endocytosis. In the present report, we investigated whether the CO2/HCO3(-) activated soluble adenylyl cyclase (sAC) regulates this process. We found that hypercapnia increased the production of cyclic adenosine monophosphate (cAMP) and stimulated protein kinase A (PKA) activity via sAC, which was necessary for Na,K-ATPase endocytosis. During hypercapnia, cAMP was mainly produced in specific microdomains in the proximity of the plasma membrane, leading to PKA Type Iα activation. In alveolar epithelial cells exposed to high CO2 concentrations, PKA Type Iα regulated the time-dependent phosphorylation of the actin cytoskeleton component α-adducin at serine 726. Cells expressing small hairpin RNA for PKAc, dominant-negative PKA Type Iα, small interfering RNA for α-adducin, and α-adducin with serine 726 mutated to alanine prevented Na,K-ATPase endocytosis. In conclusion, we provide evidence for a new mechanism by which hypercapnia via sAC, cAMP, PKA Type Iα, and α-adducin regulates Na,K-ATPase endocytosis in alveolar epithelial cells.
