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Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity.

ABSTRACT: The tissue-resident macrophages of barrier organs constitute the first line of defence against pathogens at the systemic interface with the ambient environment. In the lung, resident alveolar macrophages (AMs) provide a sentinel function against inhaled pathogens. Bacterial constituents ligate Toll-like receptors (TLRs) on AMs, causing AMs to secrete proinflammatory cytokines that activate alveolar epithelial receptors, leading to recruitment of neutrophils that engulf pathogens. Because the AM-induced response could itself cause tissue injury, it is unclear how AMs modulate the response to prevent injury. Here, using real-time alveolar imaging in situ, we show that a subset of AMs attached to the alveolar wall form connexin 43 (Cx43)-containing gap junction channels with the epithelium. During lipopolysaccharide-induced inflammation, the AMs remained sessile and attached to the alveoli, and they established intercommunication through synchronized Ca(2+) waves, using the epithelium as the conducting pathway. The intercommunication was immunosuppressive, involving Ca(2+)-dependent activation of Akt, because AM-specific knockout of Cx43 enhanced alveolar neutrophil recruitment and secretion of proinflammatory cytokines in the bronchoalveolar lavage. A picture emerges of a novel immunomodulatory process in which a subset of alveolus-attached AMs intercommunicates immunosuppressive signals to reduce endotoxin-induced lung inflammation.

SUBMITTER: Westphalen K

PROVIDER: S-EPMC4117212 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity.

Westphalen Kristin K Gusarova Galina A GA Islam Mohammad N MN Subramanian Manikandan M Cohen Taylor S TS Prince Alice S AS Bhattacharya Jahar J

Nature 20140119 7489

The tissue-resident macrophages of barrier organs constitute the first line of defence against pathogens at the systemic interface with the ambient environment. In the lung, resident alveolar macrophages (AMs) provide a sentinel function against inhaled pathogens. Bacterial constituents ligate Toll-like receptors (TLRs) on AMs, causing AMs to secrete proinflammatory cytokines that activate alveolar epithelial receptors, leading to recruitment of neutrophils that engulf pathogens. Because the AM- ...[more]

PMID: 24463523

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Project description:The glutathione S-transferase (GST) gene family codes for enzymes that detoxify xenobiotics by catalyzing the conjugation of xenobiotics to glutathione. Based on reports that inherited copy number variations (CNV) in the genome modulate some GST expression levels and with the knowledge that cigarette smoke contains >3000 xenobiotics, and that the small airway epithelium and alveolar macrophages are involved early in the pathogensis of smoking-induced lung disease, we asked: do germline CNVs modulate GST expression level in the small airway epithelium and alveolar macrophages? Affymetrix HG U133 Plus 2.0 microarrays were used to survey GST gene expression in the small airway epithelium and alveolar macrophages obtained by bronchoscopic brushings from current smokers (n=35) and nonsmokers (n=35). The CNV genotypes of these 70 subjects were determined by Affymetrix Human SNP array 5.0 chips. Sixteen % of subjects had deletions of both GSTM1 alleles. These deletions were associated with reduced GSTM1 mRNA levels in both the small airway epithelium (p<10-7) and alveolar macrophages (p<0.05). Thirty % of subjects had homozygous deletions of GSTT1 with concomitant reduced mRNA levels in both small airway epithelium and alveolar macrophages (p<10-7). In contrast, genes flanking the CNV regions of both GST genes showed no difference in expression level among subjects with and without the GST deletions (p>0.3). Interestingly, GSTT2B, a duplicate gene of GSTT2, exhibited homozygous deletion in blood in 27% of subjects and was not expressed in small airway epithelium in the remainder of subjects but was expressed in alveolar macrophages of heterozygotes and wild type subjects, proportionate to genotype (p<10-3). These data demonstrate that highly prevalent CNV deletions of genes critical to ameliorating smoking-associated xenobiotic-induced damage in the lung can result in significant modulation of the gene expression levels, with the linear relationship of genotype to expression level suggesting minimal compensation of gene expression levels in heterozygotes consistent with GST polymorphisms playing a role in the risk for development of smoking-induced lung disease.

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Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity.

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Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity.

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