Type-4 Phosphodiesterase (PDE4) Blockade Reduces NETosis in Cystic Fibrosis.

Licia Totani,Angelo Di Santo,Alessandra Bragonzi,Serena Ranucci,Antonio Piccoli,Roberto Plebani,Virgilio Evangelista,Paolo Moretti,Nicola Martelli,Alice Rossi,Mario Romano,Concetta Amore,Giuseppe Dell’Elba,Romina Pecce,Ida De Fino

doi:10.3389/fphar.2021.702677

Abstract

Neutrophilic inflammation is a key determinant of cystic fibrosis (CF) lung disease. Neutrophil-derived free DNA, released in the form of extracellular traps (NETs), significantly correlates with impaired lung function in patients with CF, underlying their pathogenetic role in CF lung disease. Thus, specific approaches to control NETosis of neutrophils migrated into the lungs may be clinically relevant in CF. We investigated the efficacy of phosphodiesterase (PDE) type-4 inhibitors, in vitro, on NET release by neutrophils from healthy volunteers and individuals with CF, and in vivo, on NET accumulation and lung inflammation in mice infected with Pseudomonas aeruginosa. PDE4 blockade curbed endotoxin-induced NET production and preserved cellular integrity and apoptosis in neutrophils, from healthy subjects and patients with CF, challenged with endotoxin, in vitro. The pharmacological effects of PDE4 inhibitors were significantly more evident on CF neutrophils. In a mouse model of Pseudomonas aeruginosa chronic infection, aerosol treatment with roflumilast, a selective PDE4 inhibitor, gave a significant reduction in free DNA in the BALF. This was accompanied by reduced citrullination of histone H3 in neutrophils migrated into the airways. Roflumilast-treated mice showed a significant improvement in weight recovery. Our study provides the first evidence that PDE4 blockade controls NETosis in vitro and in vivo, in CF-relevant models. Since selective PDE4 inhibitors have been recently approved for the treatment of COPD and psoriasis, our present results encourage clinical trials to test the efficacy of this class of drugs in CF.

Highlights

Neutrophilic inflammation is the trademark of cystic fibrosis (CF) lung disease (Tirouvanziam, 2006)
From a mechanistic point of view, we have recently discovered that selective blockade of PDE4 in human neutrophils downregulates Src family kinase activities (SFK), through protein kinase A (PKA)–mediated activation of COOH-terminal Src kinase (CSK), a major endogenous regulator of SFK (Totani et al, 2014)
In order to explore the potential role of CFTR in NETosis, we evaluated, in parallel, neutrophil extracellular traps (NETs) formation in neutrophils that were untreated or exposed to CFTRinh-172, a selective CFTR inhibitor

Summary

Introduction

Neutrophilic inflammation is the trademark of cystic fibrosis (CF) lung disease (Tirouvanziam, 2006). Excessive and persistent accumulation of neutrophils in the airways, associated with impaired bacterial clearance and tissue damage, is the early event in the life of patients with CF (Davis and Ferkol, 2013; Sly et al, 2013). Phosphodiesterase 4 Inhibition in Cystic Fibrosis induces inflammatory responses, impairs ciliary function in epithelial cells, disables CXCL8-induced bacterial killing, and causes bronchomalacia and bronchiectasis (Hartl et al, 2007; Davis and Ferkol, 2013). Recent observations in preclinical and clinical CF models indicate that the excessive accumulation of NETs in the airways plays a key pathogenetic role in lung disease (Cheng and Palaniyar, 2013). Excessive NET formation may play a pathogenetic role in vasculitis (Kessenbrock et al, 2009) and provide a scaffold for platelet adhesion and thrombus formation (Fuchs et al, 2010), mediating micro- and macrovascular occlusion

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Conclusion