ABSTRACT
Local immune activation at mucosal surfaces, mediated by mucosal lymphoid tissues, is vital for effective immune responses against pathogens. While pathogens like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can spread to multiple organs, patients with coronavirus disease 2019 (COVID-19) primarily experience inflammation and damage in their lungs. To investigate this apparent organ-specific immune response, we develop an analytical framework that recognizes the significance of mucosal lymphoid tissues. This framework combines histology, immunofluorescence, spatial transcript profiling, and mathematical modeling to identify cellular and gene expression differences between the lymphoid tissues of the lung and the gut and predict the determinants of those differences. Our findings indicate that mucosal lymphoid tissues are pivotal in organ-specific immune response to SARS-CoV-2, mediating local inflammation and tissue damage and contributing to immune dysfunction. The framework developed here has potential utility in the study of long COVID and may streamline biomarker discovery and treatment design for diseases with differential pathologies at the organ level.
Subject(s)
COVID-19 , SARS-CoV-2 , Humans , Post-Acute COVID-19 Syndrome , Inflammation , ImmunityABSTRACT
Urokinase plasminogen activator receptor-associated protein (uPARAP, or Endo180) is a transmembrane endocytic receptor that mediates collagen internalization and degradation. uPARAP may be a novel pathway for collagen turnover and matrix remodeling in the lung. The function of uPARAP in lung injury has not been described. We analyzed the pulmonary mechanics of uPARAP(-/-) and wild-type mice at baseline and examined their response after bleomycin instillation. We compared collagen internalization in primary mouse lung fibroblasts (MLFs) from wild-type and uPARAP(-/-) mice using flow cytometry and fluorescent microscopy, and we examined the role of cytokines in regulating uPARAP expression and collagen internalization. We show that uPARAP is highly expressed in the lung, and that uPARAP(-/-) mice have increased lung elastance at baseline and after injury. uPARAP(-/-) mice are protected from changes in lung permeability after acute lung injury and have increased collagen content after bleomycin injury. uPARAP is the primary pathway for internalization of collagens in MLFs. Furthermore, collagen internalization through uPARAP does not require matrix metalloproteinase digestion and is independent of integrins. Mediators of lung injury, including transforming growth factor-ß, TNF-α, and IL-1, down-regulate both uPARAP expression and collagen internalization. uPARAP is highly expressed in the murine lung, and loss of uPARAP leads to differences in lung mechanics, lung permeability, and collagen content after injury. uPARAP is required for collagen internalization by MLFs. Thus, uPARAP is a novel pathway that regulates matrix remodeling in the lung after injury.
Subject(s)
Lung/physiology , Receptors, Urokinase Plasminogen Activator/physiology , Animals , Cytokines/physiology , Down-Regulation , Flow Cytometry , Inflammation Mediators/physiology , Mice , Mice, Knockout , Microscopy, Fluorescence , Receptors, Urokinase Plasminogen Activator/geneticsABSTRACT
Fibroblast growth factor-10 (FGF-10), an alveolar epithelial cell (AEC) mitogen that is critical for lung development, may promote AEC repair. We determined whether FGF-10 attenuates H2O2-induced, A549 and rat alveolar type II cell DNA damage. We show that FGF-10 prevents H2O2-induced DNA damage assessed by an alkaline elution, ethidium bromide fluorescence as well as by a comet assay. Mitogen-activated protein kinase inhibitors abolished the protective effect of FGF-10 against H2O2-induced DNA damage yet had no effect on H2O2-induced DNA damage. A Grb2-SOS inhibitor (SH3 binding peptide), an Ras inhibitor (farnesyl transferase inhibitor 277), and an Raf-1 inhibitor (forskolin) each prevented FGF-10- and H2O2-induced A549 cell ERK1/2 phosphorylation. Also, FGF-10 and H2O2 each induced negligible ERK1/2 phosphorylation in Ras dominant-negative (N17) cells. Inhibitors of Ras and Raf-1 blocked the protective effect of FGF-10 against H2O2-induced DNA damage but had no effect on H2O2-induced DNA damage. Furthermore, cold conditions and aphidicolin, an inhibitor of DNA polymerase-alpha, -delta, and -epsilon, each blocked the protective effects of FGF-10, suggesting a role for DNA repair. We conclude that FGF-10 attenuates H2O2-induced AEC DNA damage by mechanisms that involve activation of Grb2-SOS/Ras/RAF-1/ERK1/2 pathway and DNA repair.
Subject(s)
Adaptor Proteins, Signal Transducing , DNA Damage/genetics , Fibroblast Growth Factors/metabolism , Oxidative Stress/genetics , Pulmonary Alveoli/metabolism , Pulmonary Fibrosis/metabolism , Respiratory Mucosa/metabolism , Animals , Cell Line , DNA Damage/drug effects , DNA Repair/drug effects , DNA Repair/genetics , DNA-Directed DNA Polymerase/metabolism , Enzyme Inhibitors/pharmacology , Fibroblast Growth Factor 10 , Fibroblast Growth Factors/pharmacology , GRB2 Adaptor Protein , Humans , Hydrogen Peroxide/antagonists & inhibitors , Hydrogen Peroxide/toxicity , MAP Kinase Signaling System/drug effects , MAP Kinase Signaling System/physiology , Mitogen-Activated Protein Kinase 3 , Mitogen-Activated Protein Kinases/drug effects , Mitogen-Activated Protein Kinases/metabolism , Nucleic Acid Synthesis Inhibitors , Oxidants/antagonists & inhibitors , Oxidants/toxicity , Oxidative Stress/drug effects , Proteins/antagonists & inhibitors , Proteins/metabolism , Proto-Oncogene Proteins c-raf/antagonists & inhibitors , Proto-Oncogene Proteins c-raf/metabolism , Pulmonary Alveoli/drug effects , Pulmonary Alveoli/physiopathology , Pulmonary Fibrosis/chemically induced , Pulmonary Fibrosis/genetics , Rats , Respiratory Mucosa/drug effects , ras Proteins/antagonists & inhibitors , ras Proteins/metabolismABSTRACT
About 10% of the nalidixic acid-resistant (Nal(r)) mutants in a transposition-induced library exhibited a growth factor requirement as the result of cysH, icdA, metE, or purB mutation. Resistance in all of these mutants required a functional AcrAB-TolC efflux pump, but the EmrAB-TolC pump played no obvious role. Transcription of acrAB was increased in each type of Nal(r) mutant. In the icdA and purB mutants, each of the known signaling pathways appeared to be used in activating the AcrAB-TolC pump. The metabolites that accumulate upstream of the blocks caused by the mutations are hypothesized to increase the levels of the AcrAB-TolC pump, thereby removing nalidixic acid from the organism.
