Mihaly Palmai-Pallag

The alarmin IL-1α is a master cytokine in acute lung inflammation induced by silica micro- and nanoparticles

BackgroundInflammasome-activated IL-1β plays a major role in lung neutrophilic inflammation induced by inhaled silica. However, the exact mechanisms that contribute to the initial production of precursor IL-1β (pro-IL-1β) are still unclear. Here, we assessed the implication of alarmins (IL-1α, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1α is a master cytokine that regulates IL-1β expression.MethodsPro- and mature IL-1β as well as alarmins were assessed by ELISA, Western Blot or qRT-PCR in macrophage cultures and in mouse lung following nano- and micrometric silica exposure. Implication of these immune mediators in the establishment of lung inflammatory responses to silica was investigated in knock-out mice or after antibody blockade by evaluating pulmonary neutrophil counts, CXCR2 expression and degree of histological injury.ResultsWe found that the early release of IL-1α and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1β and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1β by alveolar macrophages was significantly induced by recombinant IL-1α but not by IL-33. Neutralization or deletion of IL-1α reduced IL-1β production and neutrophil accumulation after silica in mice. Finally, IL-1α released by J774 macrophages after in vitro exposure to a range of micro- and nanoparticles of silica was correlated with the degree of lung inflammation induced in vivo by these particles.ConclusionsWe demonstrated that in response to silica exposure, IL-1α is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1β production. Moreover, we demonstrated that in vitro IL-1α release from macrophages can be used to predict the acute inflammogenic activity of silica micro- and nanoparticles.

Critical Role of Aquaporins in Interleukin 1β (IL-1β)-induced Inflammation

Background: Aquaporins are channels permeable to water, and they are essential for immune cell migration. Results: We demonstrate that aquaporin-mediated water fluxes are necessary for the NLRP3 inflammasome-dependent release of mature IL-1β in vitro and in vivo. Conclusion: Aquaporins are implicated in the mechanisms of proinflammatory cytokine secretion during inflammation. Significance: The discovery of a new function for AQPs opens new diagnostic and therapeutic opportunities in inflammatory disorders. Rapid changes in cell volume characterize macrophage activation, but the role of water channels in inflammation remains unclear. We show here that, in vitro, aquaporin (AQP) blockade or deficiency results in reduced IL-1β release by macrophages activated with a variety of NLRP3 activators. Inhibition of AQP specifically during the regulatory volume decrease process is sufficient to limit IL-1β release by macrophages through the NLRP3 inflammasome axis. The immune-related activity of AQP was confirmed in vivo in a model of acute lung inflammation induced by crystals. AQP1 deficiency is associated with a marked reduction of both lung IL-1β release and neutrophilic inflammation. We conclude that AQP-mediated water transport in macrophages constitutes a general danger signal required for NLRP3-related inflammation. Our findings reveal a new function of AQP in the inflammatory process and suggest a novel therapeutic target for anti-inflammatory therapy.

IL-1α induces CD11b(low) alveolar macrophage proliferation and maturation during granuloma formation.

Macrophages play a central role in immune and tissue responses of granulomatous lung diseases induced by pathogens and foreign bodies. Circulating monocytes are generally viewed as central precursors of these tissue effector macrophages. Here, we provide evidence that granulomas derive from alveolar macrophages serving as a local reservoir for the expansion of activated phagocytic macrophages. By exploring lung granulomatous responses to silica particles in IL‐1‐deficient mice, we found that the absence of IL‐1α, but not IL‐1β, was associated with reduced CD11bhigh phagocytic macrophage accumulation and fewer granulomas. This defect was associated with impaired alveolar clearance and resulted in the development of pulmonary alveolar proteinosis (PAP). Reconstitution of IL‐1α−/− mice with recombinant IL‐1α restored lung clearance functions and the pulmonary accumulation of CD11bhigh phagocytic macrophages. Mechanistically, IL‐1α induced the proliferation of CD11blow alveolar macrophages and differentiated these cells into CD11bhigh macrophages which perform critical phagocytic functions and organize granuloma. We newly discovered here that IL‐1α triggers lung responses requiring macrophage proliferation and maturation from tissue‐resident macrophages. Copyright

CCR2+ monocytic myeloid‐derived suppressor cells (M‐MDSCs) inhibit collagen degradation and promote lung fibrosis by producing transforming growth factor‐β1

Monocytes infiltrating scar tissue are predominantly viewed as progenitor cells. Here, we show that tissue CCR2+ monocytes have specific immunosuppressive and profibrotic functions. CCR2+ monocytic cells are acutely recruited to the lung before the onset of silica‐induced fibrosis in mice. These tissue monocytes are defined as monocytic myeloid‐derived suppressor cells (M‐MDSCs) because they significantly suppress T‐lymphocyte proliferation in vitro. M‐MDSCs collected from silica‐treated mice also express transforming growth factor (TGF)‐β1, which stimulates lung fibroblasts to release tissue inhibitor of metalloproteinase (TIMP)‐1, an inhibitor of metalloproteinase collagenolytic activity. By using LysMCreCCR2loxP/loxP mice, we show that limiting CCR2+ M‐MDSC accumulation reduces the pulmonary contents of TGF‐β1, TIMP‐1 and collagen after silica treatment. M‐MDSCs do not differentiate into lung macrophages, granulocytes or fibrocytes during pulmonary fibrogenesis. Collectively, our data indicate that M‐MDSCs contribute to lung fibrosis by specifically promoting a non‐degrading collagen microenvironment. Copyright

Towards predicting the lung fibrogenic activity of MWCNT: Key role of endocytosis, kinase receptors and ERK 1/2 signaling

Abstract Carbon nanotubes (CNT) have been reported to induce lung inflammation and fibrosis in rodents. We investigated the direct and indirect cellular mechanisms mediating the fibrogenic activity of multi-wall (MW) CNT on fibroblasts. We showed that MWCNT indirectly stimulate lung fibroblast (MLg) differentiation, via epithelial cells and macrophages, whereas no direct effect of MWCNT on fibroblast differentiation or collagen production was detected. MWCNT directly stimulated the proliferation of fibroblasts primed with low concentrations of growth factors, such as PDGF, TGF-β or EGF. MWCNT prolonged ERK 1/2 phosphorylation induced by low concentrations of PDGF or TGF-β in fibroblasts. This phenomenon and the proliferative activity of MWCNT on fibroblasts was abrogated by the inhibitors of ERK 1/2, PDGF-, TGF-β- and EGF-receptors. This activity was also reduced by amiloride, an endocytosis inhibitor. Finally, the lung fibrotic response to several MWCNT samples (different in length and diameter) correlated with their in vitro capacity to stimulate the proliferation of fibroblasts and to prolong ERK 1/2 signaling in these cells. Our findings point to a crosstalk between MWCNT, kinase receptors, ERK 1/2 signaling and endocytosis which stimulates the proliferation of fibroblasts. The mechanisms of action identified in this study contribute to predict the fibrogenic potential of MWCNT.

Lung inflammation and thymic atrophy after bleomycin are controlled by the prostaglandin D2 receptor DP1

Acute lung injury (ALI) can be accompanied by secondary systemic manifestations. In a model of ALI induced by bleomycin (bleo), we examined the response of D prostanoid receptor 1 (DP1)-deficient mice (DP1(-/-)) to better understand these processes. DP1 deficiency aggravated the toxicity of bleo as indicated by enhanced body weight loss, mortality, and lung inflammation including bronchoalveolar permeability and neutrophilia. Thymic atrophy was also observed after bleo and was strongly exacerbated in DP1(-/-) mice. This resulted from the enhanced depletion of immature T lymphocytes in the thymus of DP1(-/-) mice, a phenomenon usually related to increased glucocorticoid release in blood. Serum corticosterone was more elevated in DP1(-/-) mice after bleo than in wild-type (wt) mice. Thymocytes of DP1(-/-) mice were not more sensitive to dexamethasone in vitro, and systemic delivery of dexamethasone or peritoneal inflammation after LPS induced a similar thymic atrophy in wt and DP1(-/-) mice, indicating that pulmonary DP1 was critical to the control of thymic atrophy after bleo. DP1(-/-) mice showed increased lung and/or blood mediators involved in neutrophil recruitment and/or glucocorticoid production/thymic atrophy (osteopontin, leukemia inhibitory factor, and keratinocyte-derived chemokine) after bleo. Finally, local pulmonary DP1 activation or inhibition in wt mice abrogated or amplified thymic atrophy after bleo, respectively. Altogether, our data reveal that ALI can perturb the systemic T-cell pool by inducing thymic atrophy and that both pathological processes are controlled by the pulmonary DP1 receptor. This new pathway represents a potential therapeutic target in ALI.

New interplay between interstitial and alveolar macrophages explains pulmonary alveolar proteinosis (PAP) induced by indium tin oxide particles

Occupational exposure to indium tin oxide (ITO) particles has been associated with the development of severe lung diseases, including pulmonary alveolar proteinosis (PAP). The mechanisms of this lung toxicity remain unknown. Here, we reveal the respective roles of resident alveolar (Siglec-Fhigh AM) and recruited interstitial (Siglec-Flow IM) macrophages contributing in concert to the development of PAP. In mice treated with ITO particles, PAP is specifically associated with IL-1α (not GM-CSF) deficiency and Siglec-Fhigh AM (not Siglec-Flow IM) depletion. Mechanistically, ITO particles are preferentially phagocytosed and dissolved to soluble In3+ by Siglec-Flow IM. In contrast, Siglec-Fhigh AM weakly phagocytose or dissolve ITO particles, but are sensitive to released In3+ through the expression of the transferrin receptor-1 (TfR1). Blocking pulmonary Siglec-Flow IM recruitment in CCR2-deficient mice reduces ITO particle dissolution, In3+ release, Siglec-Fhigh AM depletion, and PAP formation. Restoration of IL-1-related Siglec-Fhigh AM also prevented ITO-induced PAP. We identified a new mechanism of secondary PAP development according to which metal ions released from inhaled particles by phagocytic IM disturb IL-1α-dependent AM self-maintenance and, in turn, alveolar clearance.