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DAP12 is required for macrophage recruitment to the lung in response to cigarette smoke and chemotaxis toward CCL2.

ABSTRACT: DAP12 is an adapter protein that associates with several receptors in macrophages. Little is known about the biological role of DAP12 in alveolar macrophages. In genome-wide profiling, we previously found that two DAP12-associated receptors, myeloid DAP12-associated lectin-1 and triggering receptor expressed on myeloid cells 2 (TREM2), were highly induced in alveolar macrophages from habitual smokers. Here, we found that transcript levels for these receptors in alveolar macrophages increased with packs per day of cigarettes smoked and expression of TREM2 protein was increased in lung macrophages of former smokers with emphysema compared with that in controls. In vitro, cigarette smoke directly induced expression of myeloid DAP12-associated lectin-1 and TREM2 and activation of DAP12 signaling in mouse macrophages. To determine whether DAP12 plays a role in cigarette smoke-induced pulmonary inflammation, we exposed wild-type and DAP12-deficient mice to chronic cigarette smoke and found significant reduction in recruitment of alveolar macrophages in DAP12-deficient mice. Because cigarette smoking induces the macrophage chemoattractant CCL2, we tested the chemotactic ability of DAP12-deficient macrophages and found abrogation of chemotaxis toward CCL2 in vitro. Airway administration of CCL2 also resulted in a significant reduction of macrophage recruitment to the lungs of DAP12-deficient mice compared with that in controls. DAP12 was also required for normal macrophage migration in a "scratch" assay. Reconstitution studies revealed that phosphorylation of the DAP12 ITAM was required for normal migration in vitro and association with TREM2 was sufficient for normal migration. These findings indicate that DAP12, possibly through association with TREM2, contributes to alveolar macrophage chemotaxis and recruitment to the lung and may mediate macrophage accumulation in lung diseases such as emphysema.

SUBMITTER: Koth LL

PROVIDER: S-EPMC4091814 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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DAP12 is required for macrophage recruitment to the lung in response to cigarette smoke and chemotaxis toward CCL2.

Koth Laura L LL Cambier C J CJ Ellwanger Almut A Solon Margaret M Hou Lydia L Lanier Lewis L LL Abram Clare L CL Hamerman Jessica A JA Woodruff Prescott G PG

Journal of immunology (Baltimore, Md. : 1950) 20100426 11

DAP12 is an adapter protein that associates with several receptors in macrophages. Little is known about the biological role of DAP12 in alveolar macrophages. In genome-wide profiling, we previously found that two DAP12-associated receptors, myeloid DAP12-associated lectin-1 and triggering receptor expressed on myeloid cells 2 (TREM2), were highly induced in alveolar macrophages from habitual smokers. Here, we found that transcript levels for these receptors in alveolar macrophages increased wit ...[more]

PMID: 20421649

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Project description:IntroductionCigarette smoking is the main risk factor for lung cancer. MSCs in the TME promoting tumor angiogenesis, growth, and metastasis. SIBLING proteins enable cancer cells to extend, invade and metastasize.ObjectivesCigarette smoke promotes the progression and metastasis of lung cancer, although how this occurs is poorly understood. We evaluated the impact of whether cigarette smoking motivates SIBLING protein expression and is involved in MSC-mediated lung tumor metastasis.MethodsWe investigated the expression of OPN in the Gene Expression Omnibus (GEO) databases and confirmed the results by immunohistochemistry (IHC), qPCR and Western blotting (WB) of lung cancer cells and tissues. The effect of OPN on the recruitment and adhesion of mesenchymal stem cells (MSCs) to lung cancer cells and lung cancers metastasis was investigated by Transwell, adhesion assays. A series of in vitro and in vivo experiments were conducted to demonstrate the mechanisms by which OPN modulates recruitment and adhesion of MSCs to lung cancer cells and lung cancer metastasis.ResultsCigarette smoke extract (CSE) and benzo[α]pyrene (B[α]P) increased levels of OPN expression and facilitated the recruitment and adhesion of MSCs to lung cancer cells via JAK2/STAT3 signaling. We also observed that OPN promotes tumor-associated MSC (TA-MSC) formation through the OPN receptor (integrins αvβ1, αvβ3, αvβ5 or CD44), inducing lung cancer cell migration and invasion. In an orthotopic mouse model of lung cancer, increases in OPN expression promoted by cigarette smoke upregulated MSC recruitment and facilitated lung cancer metastasis. Knockdown of OPN expression inhibited cigarette smoke-induced lung cancer metastasis in vivo.ConclusionCigarette smoke increases OPN expression through the JAK2/STAT3 signaling pathway to attract MSC cell recruitment and promote lung cancer metastasis. Our findings offer important insights into how lung cancer metastasis develops in smokers.

Project description:BackgroundNeuroinflammation has been implicated in the pathogenesis of chronic traumatic encephalopathy (CTE), a progressive neurodegenerative disease association with exposure to repetitive head impacts (RHI) received though playing contact sports such as American football. Past work has implicated early and sustained activation of microglia as a potential driver of tau pathology within the frontal cortex in CTE. However, the RHI induced signals required to recruit microglia to areas of damage and pathology are unknown.MethodsPostmortem brain tissue was obtained from 261 individuals across multiple brain banks. Comparisons were made using cases with CTE, cases with Alzheimer's disease (AD), and cases with no neurodegenerative disease and lacked exposure to RHI (controls). Recruitment of Iba1+ cells around the CTE perivascular lesion was compared to non-lesion vessels. TMEM119 staining was used to characterize microglia or macrophage involvement. The potent chemoattractant CCL2 was analyzed using frozen tissue from the dorsolateral frontal cortex (DLFC) and the calcarine cortex. Finally, the amounts of hyperphosphorylated tau (pTau) and Aβ42 were compared to CCL2 levels to examine possible mechanistic pathways.ResultsAn increase in Iba1+ cells was found around blood vessels with perivascular tau pathology compared to non-affected vessels in individuals with RHI. TMEM119 staining revealed the majority of the Iba1+ cells were microglia. CCL2 protein levels in the DLFC were found to correlate with greater years of playing American football, the density of Iba1+ cells, the density of CD68+ cells, and increased CTE severity. When comparing across multiple brain regions, CCL2 increases were more pronounced in the DLFC than the calcarine cortex in cases with RHI but not in AD. When examining the individual contribution of pathogenic proteins to CCL2 changes, pTau correlated with CCL2, independent of age at death and Aβ42 in AD and CTE. Although levels of Aβ42 were not correlated with CCL2 in cases with CTE, in males in the AD group, Aβ42 trended toward an inverse relationship with CCL2 suggesting possible gender associations.ConclusionOverall, CCL2 is implicated in the pathways recruiting microglia and the development of pTau pathology after exposure to RHI, and may represent a future therapeutic target in CTE.

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DAP12 is required for macrophage recruitment to the lung in response to cigarette smoke and chemotaxis toward CCL2.

Publications

DAP12 is required for macrophage recruitment to the lung in response to cigarette smoke and chemotaxis toward CCL2.

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