A novel subpopulation of monocyte-like cells in the human lung after lipopolysaccharide inhalation.

The co-ordinated recruitment of monocyte subpopulations, neutrophils and regulatory T-cells (Tregs) during the early stages of human acute lung inflammation remains poorly understood. We therefore performed a detailed characterisation of these lineages in the blood and lungs in a model of human acute lung inflammation. Healthy volunteers inhaled lipopolysaccharide (LPS) or saline (n=6 for each group). Blood was collected at 0, 2, 4, 6 and 8 h and bronchoscopy with bronchoalveolar lavage (BAL) performed at 8 h. Multiparameter flow cytometry was used to characterise monocyte subpopulations, neutrophils and Tregs in the blood and lung. Inhalation of LPS was associated with significant blood and BAL fluid neutrophilia. Blood populations of monocyte subpopulations and Tregs were unaltered by LPS. In contrast, LPS induced an accumulation of a pulmonary monocyte-like cell (PMLC) population, which was further subdivided into "inducible" CD14(++)CD16(-) and "resident" CD14(++)CD16(+) subsets. Inducible PMLCs were significantly increased following LPS inhalation (p=0.0046), whereas resident PMLCs were unchanged. In addition, we noted a significant decrease in Tregs in BAL fluid with LPS inhalation (p=0.027). The early stages of LPS-induced inflammation in humans is characterised by pulmonary accumulation of a novel inducible monocyte-like subpopulation, accompanied by significant changes in both neutrophil and Treg numbers.

Increased platelet activation in patients with stable and acute exacerbation of COPD.

RATIONALE: Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and cardiovascular disease. Interaction between inflammatory cells and activated platelets is important in the pathogenesis of atherothrombosis and may contribute to cardiovascular risk in patients with COPD. OBJECTIVES: To assess platelet-monocyte aggregation in patients with COPD and matched controls, and in patients with an acute exacerbation of COPD. METHODS: 18 men with COPD and 16 male controls matched for age and cigarette smoke exposure were recruited. A further 12 patients were investigated during and at least 2 weeks after hospitalisation for an acute exacerbation. Platelet-monocyte aggregation and platelet P-selectin expression were determined using flow cytometry. RESULTS: Patients with COPD had increased circulating platelet-monocyte aggregates compared with controls (mean (SD) 25.3 (8.3)% vs 19.5 (4.0)%, p=0.01). Platelet-monocyte aggregation was further increased during an acute exacerbation compared with convalescence (32.0 (11.0)% vs 25.5 (6.4)%, p=0.03). Platelet P-selectin expression and soluble P-selectin did not differ between groups. CONCLUSIONS: Patients with stable COPD have increased circulating platelet-monocyte aggregates compared with well-matched controls. Platelet activation is further increased in patients with COPD during an acute exacerbation. These findings identify a novel mechanism to explain the increased cardiovascular risk in COPD and suggest platelet inhibition as a plausible therapeutic target.

-------A type I IFN, prothrombotic hyperinflammatory neutrophil signature is distinct for COVID-19 ARDS--.

Background: Acute respiratory distress syndrome (ARDS) is a severe critical condition with a high mortality that is currently in focus given that it is associated with mortality caused by coronavirus disease 2019 (COVID-19). Neutrophils play a key role in the lung injury characteristic of non-COVID-19 ARDS and there is also accumulating evidence of neutrophil mediated lung injury in patients who succumb to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: We undertook a functional proteomic and metabolomic survey of circulating neutrophil populations, comparing patients with COVID-19 ARDS and non-COVID-19 ARDS to understand the molecular basis of neutrophil dysregulation. Results: Expansion of the circulating neutrophil compartment and the presence of activated low and normal density mature and immature neutrophil populations occurs in ARDS, irrespective of cause. Release of neutrophil granule proteins, neutrophil activation of the clotting cascade and upregulation of the Mac-1 platelet binding complex with formation of neutrophil platelet aggregates is exaggerated in COVID-19 ARDS. Importantly, activation of components of the neutrophil type I interferon responses is seen in ARDS following infection with SARS-CoV-2, with associated rewiring of neutrophil metabolism, and the upregulation of antigen processing and presentation. Whilst dexamethasone treatment constricts the immature low density neutrophil population, it does not impact upon prothrombotic hyperinflammatory neutrophil signatures. Conclusions: Given the crucial role of neutrophils in ARDS and the evidence of a disordered myeloid response observed in COVID-19 patients, this work maps the molecular basis for neutrophil reprogramming in the distinct clinical entities of COVID-19 and non-COVID-19 ARDS.

Surface derivatization state of polystyrene latex nanoparticles determines both their potency and their mechanism of causing human platelet aggregation in vitro.

There is evidence that nanoparticles (NP) can enter the bloodstream following deposition in the lungs, where they may interact with platelets. Polystyrene latex nanoparticles (PLNP) of the same size but with different surface charge-unmodified (umPLNP), aminated (aPLNP), and carboxylated (cPLNP)-were used as model NP to study interactions with human blood and platelets. Both the cPLNP and the aPLNP caused platelet aggregation, whereas the umPLNP did not. Whereas cPLNP caused aggregation by classical upregulation of adhesion receptors, aPLNP did not upregulate adhesion receptors and appeared to act by perturbation of the platelet membrane, revealing anionic phospholipids. Neither oxidative stress generation by particles nor metal contamination was responsible for these effects, which were a result of differential surface derivatization. The study reveals that NP composed of insoluble low-toxicity material are significantly altered in their potency in causing platelet aggregation by altering the surface chemistry. The two surface modifications, aminated and carboxylated, that did cause aggregation did so by different mechanisms. The study highlights the fundamental role of surface chemistry on bioactivity of NP in a platelet activation model.