Reversibility of lung inflammation caused by SP-B deficiency (original) (raw)
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Surfactant proteins and the inflammatory and immune response in the lung
2009
Surfactant proteins are important for regulating surfactant activity and innate host defence; in particular, polymorphisms in intron 4 of the SP-B gene and dominant mutations of SP-C have been associated with bronchopulmonary dysplasia. The innate immune system is older and consists of soluble proteins, which bind microbial products and phagocytic leukocytes resembling primitive amebae, which float through the bloodstream and migrate into tissues at sites of inflammation, or reside in tissue waiting for foreign material. The innate immune system is always active and is immediately responsive, ready to recognize and inactivate microbial products entering lungs and other tissues. Pro-inflammatory cytokines (interleukins IL-1β, IL-6 and soluble ICAM-1) are present in lung lavage fluid from day 1 in premature infants with respiratory distress and reach a peak in the second week. IL-1β induces the release of inflammatory mediators, activating inflammatory cells and up-regulating adhesion...
2001
This study examines the relationships between inflammation, surfactant protein (SP) expression, surfactant function, and lung physiology in a murine model of acute lung injury (ALI). 129/J mice received aerosolized endotoxin lipopolysaccharide [LPS] daily for up to 96 h to simulate the cytokine release and acute inflammation of ALI. Lung elastance (E L ) and resistance, lavage fluid cell counts, cytokine levels, phospholipid and protein content, and surfactant function were measured. Lavage and lung tissue SP content were determined by Western blot and immunohistochemistry, and tissue messenger RNA (mRNA) levels were assessed by Northern blot and in situ hybridization. Tumor necrosis factor-␣ and neutrophil counts in bronchoalveolar lavage fluid increased within 2 h of LPS exposure, followed by increases in total protein, interleukin (IL)-1  , IL-6, and interferon-␥ . E L increased within 24 h of LPS exposure and remained abnormal up to 96 h. SP-B protein and mRNA levels were decreased at 24, 48, and 96 h. By contrast, SP-A protein and mRNA levels and SP-C mRNA levels were not reduced. Surfactant dysfunction occurred coincident with changes in SP-B levels. This study demonstrates that lung dysfunction in mice with LPS-ALI corresponds closely with abnormal surfactant function and reduced SP-B expression.
EFFECT OF SURFACTANT PROTEIN A (SPA) ON THE PRODUCTION OF CYTOKINES BY HUMAN PULMONARY MACROPHAGES
Shock, 2000
Surfactant protein A (SP-A) is thought to play a role in the modulation of lung inflammation during acute respiratory distress syndrome (ARDS). However, SP-A has been reported both to stimulate and to inhibit the proinflammatory activity of pulmonary macrophages (M). Because of the interspecies differences and heterogeneity of M subpopulations used may have influenced previous controversial results, in this study, we investigated the effect of human SP-A on the production of cytokines and other inflammatory mediators by two well-defined subpopulations of human pulmonary M. Surfactant and both alveolar (aM) and interstitial (iM) macrophages were obtained from multiple organ donor lungs by bronchoalveolar lavage and enzymatic digestion. Donors with either recent history of tobacco smoking, more than 72 h on mechanical ventilation, or any radiological pulmonary infiltrate were discarded. SP-A was purified from isolated surfactant using sequential butanol and octyl glucoside extractions. After 24-h preculture, purified M were cultured for 24 h in the presence or absence of LPS (10 µg/mL), SP-A (50 µg/mL), and combinations. Nitric oxide and carbon monoxide (CO) generation (pmol/µg protein), cell cGMP content (pmol/µg protein), and tumor necrosis factor alpha (TNF␣), interleukin (IL)-1, and IL-6 release to the medium (pg/µg protein) were determined. SP-A inhibited the lipopolysaccharide (LPS)-induced TNF␣ response of both interstitial and alveolar human M, as well as the IL-1 response in iM. The SP-A effect on TNF␣ production could be mediated by a suppression in the LPS-induced increase in intracellular cGMP. In iM but not in aM, SP-A also inhibited the LPS-induced IL-1 secretion and CO generation. These data lend further credit to a physiological function of SP-A in regulating alveolar host defense and inflammation by suggesting a fundamental role of this apoprotein in limiting excessive proinflammatory cytokine release in pulmonary M during ARDS.
SP-B deficiency causes respiratory failure in adult mice
2003
2003; 10.1152/ajplung.00011.2003.—Targeted deletion of the surfactant protein (SP)-B locus in mice causes lethal neona-tal respiratory distress. To assess the importance of SP-B for postnatal lung function, compound transgenic mice were generated in which the mouse SP-B cDNA was conditionally expressed under control of exogenous doxycycline in SP-B/ mice. Doxycycline-regulated expression of SP-B fully cor-rected lung function in compound SP-B/ mice and pro-tected mice from respiratory failure at birth. Withdrawal of doxycycline from adult compound SP-B/ mice resulted in decreased alveolar content of SP-B, causing respiratory fail-ure when SP-B concentration was reduced to25 % of normal levels. Decreased SP-B was associated with low alveolar content of phosphatidylglycerol, accumulation of mispro-cessed SP-C proprotein in the air spaces, increased protein
Surfactant Protein-A Function: Knowledge Gained From SP-A Knockout Mice
Frontiers in Pediatrics
Pulmonary surfactant proteins have many roles in surfactant- related functions and innate immunity. One of these proteins is the surfactant protein A (SP-A) that plays a role in both surfactant-related processes and host defense and is the focus in this review. SP-A interacts with the sentinel host defense cell in the alveolus, the alveolar macrophage (AM), to modulate its function and expression profile under various conditions, as well as other alveolar epithelial cells such as the Type II cell. Via these interactions, SP-A has an impact on the alveolar microenvironment. SP-A is also important for surfactant structure and function. Much of what is understood of the function of SP-A and its various roles in lung health has been learned from SP-A knockout (KO) mouse experiments, as reviewed here. A vast majority of this work has been done with infection models that are bacterial, viral, and fungal in nature. Other models have also been used, including those of bleomycin-induced lung...
LPS-Treated Macrophage Cytokines Repress Surfactant Protein–B in Lung Epithelial Cells
American Journal of Respiratory Cell and Molecular Biology, 2013
In the mouse lung, Escherichia coli LPS can decrease surfactant protein-B (SFTPB) mRNA and protein concentrations. LPS also regulates the expression, synthesis, and concentrations of a variety of gene and metabolic products that inhibit SFTPB gene expression. The purpose of the present study was to determine whether LPS acts directly or indirectly on pulmonary epithelial cells to trigger signaling pathways that inhibit SFTPB expression, and whether the transcription factor CCAAT/enhancer binding protein (C/EBP)-b (CEBPB) is a downstream inhibitory effector. To investigate the mechanism of SFTPB repression, the human pulmonary epithelial cell lines NCI-H441 (H441) and NCI-H820 (H820) and the mouse macrophage-like cell line RAW264.7 were treated with LPS. Whereas LPS did not decrease SFTPB transcripts in H441 or H820 cells, the conditioned medium of LPS-treated RAW264.7 cells decreased SFTPB transcripts in H441 and H820 cells, and inhibited SFTPB promoter activity in H441 cells. In the presence of neutralizing anti-tumor necrosis factor (TNF) antibodies, the conditioned medium of LPS-treated RAW264.7 cells did not inhibit SFTPB promoter activity. In H441 cells treated with recombinant TNF protein, SFTPB transcripts decreased, whereas CEBPB transcripts increased and the transient coexpression of CEBPB decreased SFTPB promoter activity. Further, CEBPB short, interfering RNA increased basal SFTPB transcripts and countered the decrease of SFTPB transcripts by TNF. Together, these findings suggest that macrophages participate in the repression of SFTPB expression by LPS, and that macrophage-released cytokines (including TNF) regulate the transcription factor CEBPB, which can function as a downstream transcriptional repressor of SFTPB gene expression in pulmonary epithelial cells.
AJP: Lung Cellular and Molecular Physiology, 2012
Nguyen HA, Rajaram MV, Meyer DA, Schlesinger LS. Pulmonary surfactant protein A and surfactant lipids upregulate IRAK-M, a negative regulator of TLR-mediated inflammation in human macrophages. Alveolar macrophages (AMs) are exposed to frequent challenges from inhaled particulates and microbes and function as a first line of defense with a highly regulated immune response because of their unique biology as prototypic alternatively activated macrophages. Lung collectins, particularly surfactant protein A (SP-A), contribute to this activation state by fine-tuning the macrophage inflammatory response. During short-term (10 min-2 h) exposure, SP-A's regulation of human macrophage responses occurs through decreased activity of kinases required for proinflammatory cytokine production. However, AMs are continuously exposed to surfactant, and the biochemical pathways underlying long-term reduction of proinflammatory cytokine activity are not known. We investigated the molecular mechanism(s) underlying SP-A-and surfactant lipid-mediated suppression of proinflammatory cytokine production in response to Toll-like receptor (TLR) 4 (TLR4) activation over longer time periods. We found that exposure of human macrophages to SP-A for 6 -24 h upregulates expression of IL-1 receptor-associated kinase M (IRAK-M), a negative regulator of TLR-mediated NF-B activation. Exposure to Survanta, a natural bovine lung extract lacking SP-A, also enhances IRAK-M expression, but at lower magnitude and for a shorter duration than SP-A. Surfactant-mediated upregulation of IRAK-M in macrophages suppresses TLR4-mediated TNF-␣ and IL-6 production in response to LPS, and IRAK-M knockdown by small interfering RNA reverses this suppression. In contrast to TNF-␣ and IL-6, the surfactant components upregulate LPS-mediated immunoregulatory IL-10 production, an effect reversed by IRAK-M knockdown. In conclusion, these data identify an important signaling regulator in human macrophages that is used by surfactant to control the long-term alveolar inflammatory response, i.e., enhanced IRAK-M activity. alveolar macrophages; pattern recognition receptors; alternative activation * H. A. Nguyen and M. V. S. Rajaram contributed equally to this work.