Effects of bone marrow‐derived mesenchymal stromal cells on gene expression in human alveolar type II cells exposed to TNF‐α, IL‐1β, and IFN‐γ

The acute respiratory distress syndrome (ARDS) is common in critically ill patients and has a high mortality rate. Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in animal models of ARDS, and their benefits occur in part through interactions with alveolar type II (ATII) cells. However, the effects that MSCs have on human ATII cells have not been well studied. Using previously published microarray data, we performed genome‐wide differential gene expression analyses of human ATII cells that were (1) unstimulated, (2) exposed to proinflammatory cytokines (CytoMix), or (3) exposed to proinflammatory cytokines plus MSCs. Findings were validated by qPCR. Alveolar type II cells differentially expressed hundreds of genes when exposed either to proinflammatory cytokines or to proinflammatory cytokines plus MSCs. Stimulation with proinflammatory cytokines increased expression of inflammatory genes and downregulated genes related to surfactant function and alveolar fluid clearance. Some of these changes, including expression of some cytokines and genes related to surfactant, were reversed by exposure to MSCs. In addition, MSCs induced upregulation of other potentially beneficial genes, such as those related to extracellular matrix remodeling. We confirmed several of these gene expression changes by qPCR. Thus, ATII cells downregulate genes associated with surfactant and alveolar fluid clearance when exposed to inflammatory cytokines, and mesenchymal stromal cells partially reverse many of these gene expression changes.Mesenchymal stromal cells (MSCs) have therapeutic potential for the acute respiratory distress syndrome, and their benefits occur in part through interactions with alveolar type II (ATII) cells. We performed genome‐wide differential gene expression analyses of human ATII cells that were (1) unstimulated, (2) exposed to proinflammatory cytokines (CytoMix), or (3) exposed to CytoMix plus MSCs. Stimulation with CytoMix increased expression of inflammatory genes and downregulated genes related to surfactant function and alveolar fluid clearance, and several gene expression changes were reversed by exposure to MSCs.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145579/1/phy213831_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145579/2/phy213831.pd

The association of plasma biomarkers with computed tomography-assessed emphysema phenotypes

Rationale: Chronic obstructive pulmonary disease (COPD) is a phenotypically heterogeneous disease. In COPD, the presence of emphysema is associated with increased mortality and risk of lung cancer. High resolution computed tomography (HRCT) scans are useful in quantifying emphysema but are associated with radiation exposure and high incidence of false positive findings (i.e., nodules). Using a comprehensive biomarker panel, we sought to determine if there was a peripheral blood biomarker signature of emphysema. Methods: 114 plasma biomarkers were measured using a custom assay in 588 individuals enrolled in the COPDGene study. Quantitative emphysema measurements included percent low lung attenuation (%LAA) ≤ −950 HU, ≤ − 910 HU and mean lung attenuation at the 15th percentile on lung attenuation curve (LP15A). Multiple regression analysis was performed to determine plasma biomarkers associated with emphysema independent of covariates age, gender, smoking status, body mass index and FEV1. The findings were subsequently validated using baseline blood samples from a separate cohort of 388 subjects enrolled in the Treatment of Emphysema with a Selective Retinoid Agonist (TESRA) study. Results: Regression analysis identified multiple biomarkers associated with CT-assessed emphysema in COPDGene, including advanced glycosylation end-products receptor (AGER or RAGE, p < 0.001), intercellular adhesion molecule 1 (ICAM, p < 0.001), and chemokine ligand 20 (CCL20, p < 0.001). Validation in the TESRA cohort revealed significant associations with RAGE, ICAM1, and CCL20 with radiologic emphysema (p < 0.001 after meta-analysis). Other biomarkers that were associated with emphysema include CDH1, CDH 13 and SERPINA7, but were not available for validation in the TESRA study. Receiver operating characteristics analysis demonstrated a benefit of adding a biomarker panel to clinical covariates for detecting emphysema, especially in those without severe airflow limitation (AUC 0.85). Conclusions: Our findings, suggest that a panel of blood biomarkers including sRAGE, ICAM1 and CCL20 may serve as a useful surrogate measure of emphysema, and when combined with clinical covariates, may be useful clinically in predicting the presence of emphysema compared to just using covariates alone, especially in those with less severe COPD. Ultimately biomarkers may shed light on disease pathogenesis, providing targets for new treatments. Electronic supplementary material The online version of this article (doi:10.1186/s12931-014-0127-9) contains supplementary material, which is available to authorized users

The association of plasma biomarkers with computed tomography-assessed emphysema phenotypes

Abstract Rationale Chronic obstructive pulmonary disease (COPD) is a phenotypically heterogeneous disease. In COPD, the presence of emphysema is associated with increased mortality and risk of lung cancer. High resolution computed tomography (HRCT) scans are useful in quantifying emphysema but are associated with radiation exposure and high incidence of false positive findings (i.e., nodules). Using a comprehensive biomarker panel, we sought to determine if there was a peripheral blood biomarker signature of emphysema. Methods 114 plasma biomarkers were measured using a custom assay in 588 individuals enrolled in the COPDGene study. Quantitative emphysema measurements included percent low lung attenuation (%LAA)≤ - 950 HU, ≤ -910 HU and mean lung attenuation at the 15th percentile on lung attenuation curve (LP15A). Multiple regression analysis was performed to determine plasma biomarkers associated with emphysema independent of covariates age, gender, smoking status, body mass index and FEV1. The findings were subsequently validated using baseline blood samples from a separate cohort of 388 subjects enrolled in the Treatment of Emphysema with a Selective Retinoid Agonist (TESRA) study. Results Regression analysis identified multiple biomarkers associated with CT-assessed emphysema in COPDGene, including advanced glycosylation end-products receptor (AGER or RAGE, p < 0.001), intercellular adhesion molecule 1 (ICAM, p < 0.001), and chemokine ligand 20 (CCL20, p < 0.001). Validation in the TESRA cohort revealed significant associations with RAGE, ICAM1, and CCL20 with radiologic emphysema (p < 0.001 after meta-analysis). Other biomarkers that were associated with emphysema include CDH1, CDH 13 and SERPINA7, but were not available for validation in the TESRA study. Receiver operating characteristics analysis demonstrated a benefit of adding a biomarker panel to clinical covariates for detecting emphysema, especially in those without severe airflow limitation (AUC 0.85). Conclusions Our findings, suggest that a panel of blood biomarkers including sRAGE, ICAM1 and CCL20 may serve as a useful surrogate measure of emphysema, and when combined with clinical covariates, may be useful clinically in predicting the presence of emphysema compared to just using covariates alone, especially in those with less severe COPD. Ultimately biomarkers may shed light on disease pathogenesis, providing targets for new treatments.http://deepblue.lib.umich.edu/bitstream/2027.42/134591/1/12931_2014_Article_127.pd

Mechanisms of ATII-to-ATI Cell Differentiation during Lung Regeneration

The alveolar epithelium consists of (ATI) and type II (ATII) cells. ATI cells cover the majority of the alveolar surface due to their thin, elongated shape and are largely responsible for barrier function and gas exchange. During lung injury, ATI cells are susceptible to injury, including cell death. Under some circumstances, ATII cells also die. To regenerate lost epithelial cells, ATII cells serve as progenitor cells. They proliferate to create new ATII cells and then differentiate into ATI cells. Regeneration of ATI cells is critical to restore normal barrier and gas exchange function. Although the signaling pathways by which ATII cells proliferate have been explored, the mechanisms of ATII-to-ATI cell differentiation have not been well studied until recently. New studies have uncovered signaling pathways that mediate ATII-to-ATI differentiation. Bone morphogenetic protein (BMP) signaling inhibits ATII proliferation and promotes differentiation. Wnt/&beta;-catenin and ETS variant transcription factor 5 (Etv5) signaling promote proliferation and inhibit differentiation. Delta-like 1 homolog (Dlk1) leads to a precisely timed inhibition of Notch signaling in later stages of alveolar repair, activating differentiation. Yes-associated protein/Transcriptional coactivator with PDZ-binding motif (YAP/TAZ) signaling appears to promote both proliferation and differentiation. We recently identified a novel transitional cell state through which ATII cells pass as they differentiate into ATI cells, and this has been validated by others in various models of lung injury. This intermediate cell state is characterized by the activation of Transforming growth factor beta (TGF&beta;) and other pathways, and some evidence suggests that TGF&beta; signaling induces and maintains this state. While the abovementioned signaling pathways have all been shown to be involved in ATII-to-ATI cell differentiation during lung regeneration, there is much that remains to be understood. The up- and down-stream signaling events by which these pathways are activated and by which they induce ATI cell differentiation are unknown. In addition, it is still unknown how the various mechanistic steps from each pathway interact with one another to control differentiation. Based on these recent studies that identified major signaling pathways driving ATII-to-ATI differentiation during alveolar regeneration, additional studies can be devised to understand the interaction between these pathways as they work in a coordinated manner to regulate differentiation. Moreover, the knowledge from these studies may eventually be used to develop new clinical treatments that accelerate epithelial cell regeneration in individuals with excessive lung damage, such as patients with the Acute Respiratory Distress Syndrome (ARDS), pulmonary fibrosis, and emphysema

Transepithelial Migration of Neutrophils: Mechanisms and Implications for Acute Lung Injury

The primary function of neutrophils in host defense is to contain and eradicate invading microbial pathogens. This is achieved through a series of swift and highly coordinated responses culminating in ingestion (phagocytosis) and killing of invading microbes. While these tasks are usually performed without injury to host tissues, in pathologic circumstances such as sepsis, potent antimicrobial compounds can be released extracellularly, inducing a spectrum of responses in host cells ranging from activation to injury and death. In the lung, such inflammatory damage is believed to contribute to the pathogenesis of diverse lung diseases, including acute lung injury and the acute respiratory distress syndrome, chronic obstructive lung disease, and cystic fibrosis. In these disorders, epithelial cells are targets of leukocyte-derived antimicrobial products, including proteinases and oxidants. Herein, we review the mechanisms involved in the physiologic process of neutrophil transepithelial migration, including the role of specific adhesion molecules on the leukocyte and epithelial cells. We examine the responses of the epithelial cells to the itinerant leukocytes and their cytotoxic products and the consequences of this for lung injury and repair. This paradigm has important clinical implications because of the potential for selective blockade of these pathways to prevent or attenuate lung injury

Investigating the role of nucleotide-binding oligomerization domain-like receptors in bacterial lung infection

Lower respiratory tract infections (LRTIs) are a persistent and pervasive public health problem worldwide. Pneumonia and other LRTIs will be among the leading causes of death in adults, and pneumonia is the single largest cause of death in children. LRTIs are also an important cause of acute lung injury and acute exacerbations of chronic obstructive pulmonary disease. Because innate immunity is the first line of defense against pathogens, understanding the role of innate immunity in the pulmonary system is of paramount importance. Pattern recognition molecules (PRMs) that recognize microbial-associated molecular patterns are an integral component of the innate immune system and are located in both cell membranes and cytosol. Toll-like receptors and nucleotide-binding oligomerization domain-like receptors (NLRs) are the major sensors at the forefront of pathogen recognition. Although Toll-like receptors have been extensively studied in host immunity, NLRs have diverse and important roles in immune and inflammatory responses, ranging from antimicrobial properties to adaptive immune responses. The lung contains NLR-expressing immune cells such as leukocytes and nonimmune cells such as epithelial cells that are in constant and close contact with invading microbes. This pulmonary perspective addresses our current understanding of the structure and function of NLR family members, highlighting advances and gaps in knowledge, with a specific focus on immune responses in the respiratory tract during bacterial infection. Further advances in exploring cellular and molecular responses to bacterial pathogens are critical to develop improved strategies to treat and prevent devastating infectious diseases of the lung

Myeloid Differentiation Protein-2–Dependent and –Independent Neutrophil Accumulation during Escherichia coli Pneumonia

Bacterial pneumonia remains a serious disease. Pattern recognition receptors play an integral role in neutrophil accumulation during pneumonia. Although myeloid differentiation protein (MD)-2 has been recognized as a key molecule for LPS signaling, the role of MD-2 in neutrophil accumulation in the lung during bacterial infection has not been explored. Here, we investigate the role of MD-2 in Escherichia coli LPS–induced lung inflammation and E. coli–induced pneumonia. LPS-induced CD14-independent neutrophil accumulation was abolished in CD14/MD-2−/− mice. MD-2−/− mice challenged with LPS displayed attenuated neutrophil influx, NF-κB activation, cytokine/chemokine expression, and lung histopathology. MD-2−/− mice transplanted with MD-2+/+ bone marrow demonstrated decreased neutrophil influx and cytokine/chemokine expression in the lungs when challenged by LPS. MD-2−/− mice infected with E. coli demonstrated reduced neutrophil influx and cytokine/chemokine expression in the lungs, whereas heat-killed E. coli did not induce either neutrophil accumulation or cytokine/chemokine expression in MD-2−/− mice infected with E. coli. Furthermore, MD-2−/− mice displayed increased bacterial burden in the lungs and enhanced bacterial dissemination. Toll-like receptor (TLR)-5−/− mice infected with E. coli exhibited attenuated neutrophil accumulation, whereas MD-2/TLR5−/− mice inoculated with E. coli showed further attenuated neutrophil influx and impaired bacterial clearance. Taken together, these new findings demonstrate: (1) the important role of MD-2 in the CD14-independent LPS-mediated cascade of neutrophil influx; (2) the relative importance of bone marrow– and non–bone marrow cell–derived MD-2 in LPS-induced inflammation; and (3) the essential role of MD-2–dependent and MD-2–independent (TLR5) signaling in E. coli–induced neutrophil accumulation and pulmonary host defense