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Byline: Vishal. Bali, Peter. Kardos, Clive. Page, Paola. Rogliani, Luigino. Calzetta, Ada. Adriano, Aidan. Byrne, Adekemi. Adeyemi, Andrew. Frederickson, Jonathan. Schelfhout BACKGROUND: Refractory or unexplained chronic cough (RCC or UCC) [...]

Platelets are recruited to inflammatory foci and contribute to host defense and inflammatory responses. Compared with platelet recruitment in hemostasis and thrombosis, the mechanisms of platelet recruitment in inflammation and host defense are poorly understood. Neutrophil recruitment to lung airspaces after inhalation of bacterial LPS requires platelets and PSGL-1 in mice. Given this association between platelets and neutrophils, we investigated whether recruitment of platelets to lungs of mice after LPS inhalation was dependent on PSGL-1, P-selectin, or interaction with neutrophils. BALB/c mice were administered intranasal LPS (O55:B5, 5 mg/kg) and, 48 hours later, lungs were collected and platelets and neutrophils quantified in tissue sections by immunohistochemistry. The effects of functional blocking antibody treatments targeting the platelet-neutrophil adhesion molecules, P-selectin or PSGL-1, or treatment with a neutrophil-depleting antibody targeting Ly6G, were tested on the extent of LPS-induced lung platelet recruitment. Separately in Pf4-Cre × mTmG mice, two-photon intravital microscopy was used to image platelet adhesion in live lungs. Inhalation of LPS caused both platelet and neutrophil recruitment to the lung vasculature. However, decreasing lung neutrophil recruitment by blocking PSGL-1, P-selectin, or depleting blood neutrophils had no effect on lung platelet recruitment. Lung intravital imaging revealed increased adhesion of platelets in the lung microvasculature which was not associated with thrombus formation. In conclusion, platelet recruitment to lungs in response to LPS occurs through mechanisms distinct from those mediating neutrophil recruitment, or the occurrence of pulmonary emboli.

Isolated airway smooth muscle has been extensively investigated since 1840 to understand the pharmacology of airway diseases. There has often been poor predictability from murine experiments to drugs evaluated in patients with asthma or chronic obstructive pulmonary disease (COPD). However, the use of isolated human airways represents a sensible strategy to optimise the development of innovative molecules for the treatment of respiratory diseases. This review aims to provide updated evidence on the current uses of isolated human airways in validated in vitro methods to investigate drugs in development for the treatment of chronic obstructive respiratory disorders. This review also provides historical notes on the pioneering pharmacological research on isolated human airway tissues, the key differences between human and animal airways, as well as the pivotal differences between human medium bronchi and small airways. Experiments carried out with isolated human bronchial tissues in vitro and ex vivo replicate many of the main anatomical, pathophysiological, mechanical and immunological characteristics of patients with asthma or COPD. In vitro models of asthma and COPD using isolated human airways can provide information that is directly translatable into humans with obstructive lung diseases. Regardless of the technique used to investigate drugs for the treatment of chronic obstructive respiratory disorders (i.e., isolated organ bath systems, videomicroscopy and wire myography), the most limiting factors to produce high‐quality and repeatable data remain closely tied to the manual skills of the researcher conducting experiments and the availability of suitable tissue. [ABSTRACT FROM AUTHOR]

Background and Purpose: Platelet function during inflammation is dependent on activation by endogenous nucleotides. Non‐canonical signalling via the P2Y1 receptor is important for these non‐thrombotic functions of platelets. However, apart from ADP, the role of other endogenous nucleotides acting as agonists at P2Y1 receptors is unknown. This study compared the effects of ADP, Ap3A, NAD+, ADP‐ribose, and Up4A on platelet functions contributing to inflammation or haemostasis. Experimental Approach: Platelets obtained from healthy human volunteers were incubated with ADP, Ap3A, NAD+, ADP‐ribose, or Up4A, with aggregation and fibrinogen binding measured (examples of function during haemostasis) or before exposure to fMLP to measure platelet chemotaxis (an inflammatory function). In silico molecular docking of these nucleotides to the binding pocket of P2Y1 receptors was then assessed. Key Results: Platelet aggregation and binding to fibrinogen induced by ADP was not mimicked by NAD+, ADP‐ribose, and Up4A. However, these endogenous nucleotides induced P2Y1‐dependent platelet chemotaxis, an effect that required RhoA and Rac‐1 activity, but not canonical PLC activity. Analysis of molecular docking of the P2Y1 receptor revealed distinct differences of amino acid interactions and depth of fit within the binding pocket for Ap3A, NAD+, ADP‐ribose, or Up4A compared with ADP. Conclusion and Implications: Platelet function (aggregation vs motility) can be differentially modulated by biased‐agonist activation of P2Y1 receptors. This may be due to the character of the ligand‐binding pocket interaction. This has implications for future therapeutic strategies aimed to suppress platelet activation during inflammation without affecting haemostasis as is the requirement of current ant‐platelet drugs. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non‐thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc [ABSTRACT FROM AUTHOR]