The role of pro- and anti-inflammatory responses in silica-induced lung fibrosis

BACKGROUND: It has been generally well accepted that chronic inflammation is a necessary component of lung fibrosis but this concept has recently been challenged. METHODS: Using biochemical, histological, immunohistochemistry, and cellular analyses, we compared the lung responses (inflammation and fibrosis) to fibrogenic silica particles (2.5 and 25 mg/g lung) in Sprague-Dawley rats and NMRI mice. RESULTS: Rats treated with silica particles developed chronic and progressive inflammation accompanied by an overproduction of TNF-α as well as an intense lung fibrosis. Dexamethasone or pioglitazone limited the amplitude of the lung fibrotic reaction to silica in rats, supporting the paradigm that inflammation drives lung fibrosis. In striking contrast, in mice, silica induced only a limited and transient inflammation without TNF-α overproduction. However, mice developed lung fibrosis of a similar intensity than rats. The fibrotic response in mice was accompanied by a high expression of the anti-inflammatory and fibrotic cytokine IL-10 by silica-activated lung macrophages. In mice, IL-10 was induced only by fibrotic particles and significantly expressed in the lung of silica-sensitive but not silica-resistant strains of mice. Anti-inflammatory treatments did not control lung fibrosis in mice. CONCLUSION: These results indicate that, beside chronic lung inflammation, a pronounced anti-inflammatory reaction may also contribute to the extension of silica-induced lung fibrosis and represents an alternative pathway leading to lung fibrosis

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

BackgroundInflammasome-activated IL-1ß 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-1ß (pro-IL-1ß) are still unclear. Here, we assessed the implication of alarmins (IL-1¿, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1¿ is a master cytokine that regulates IL-1ß expression.MethodsPro- and mature IL-1ß 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-1¿ and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1ß and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1ß by alveolar macrophages was significantly induced by recombinant IL-1¿ but not by IL-33. Neutralization or deletion of IL-1¿ reduced IL-1ß production and neutrophil accumulation after silica in mice. Finally, IL-1¿ 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-1¿ is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1ß production. Moreover, we demonstrated that in vitro IL-1¿ release from macrophages can be used to predict the acute inflammogenic activity of silica micro- and nanoparticles

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

Doravirine plus lamivudine two-drug regimen as maintenance antiretroviral therapy in people living with HIV: a French observational study

International audienceBackground: Two-drug regimens based on integrase strand transfer inhibitors (INSTIs) and boosted PIs have entered recommended ART. However, INSTIs and boosted PIs may not be suitable for all patients. We aimed to report our experience with doravirine/lamivudine as maintenance therapy in people living with HIV (PLWH) followed in French HIV settings.Methods: This observational study enrolled all adults who initiated doravirine/lamivudine between 1 September 2019 and 31 October 2021, in French HIV centres participating in the Dat'AIDS cohort. The primary outcome was the rate of virological success (plasma HIV-RNA < 50 copies/mL) at Week (W)48. Secondary outcomes included: rate of treatment discontinuation for non-virological reasons, evolution of CD4 count and CD4/CD8 ratio over follow-up.Results: Fifty patients were included, with 34 (68%) men; median age: 58 years (IQR 51-62), ART duration: 20 years (13-23), duration of virological suppression: 14 years (8-19), CD4 count: 784 cells/mm3 (636-889). Prior to switching, all had plasma HIV-RNA < 50 copies/mL. All but three were naive to doravirine, and 36 (72%) came from a three-drug regimen. Median follow-up was 79 weeks (IQR 60-96). Virological success rate at W48 was 98.0% (95% CI 89.4-99.9). One virological failure occurred at W18 (HIV-RNA = 101 copies/mL) in a patient who briefly discontinued doravirine/lamivudine due to intense nightmares; there was no resistance at baseline and no resistance emergence. There were three strategy discontinuations for adverse events (digestive disorders: n = 2; insomnia: n = 1). There was no significant change in CD4/CD8 ratio, while CD4 T cell count significantly increased.Conclusions: These preliminary findings suggest that doravirine/lamivudine regimens can maintain high levels of viral suppression in highly ART-experienced PLWH with long-term viral suppression, and good CD4+ T cell count