Dual effects of human neutrophil peptides in a mouse model of pneumonia and ventilator-induced lung injury

Abstract

BackgroundPneumonia is a major cause of high morbidity and mortality in critically illness, and frequently requires support with mechanical ventilation. The latter can lead to ventilator-induced lung injury characterized by neutrophil infiltration. The cationic human neutrophil peptides (HNP) stored in neutrophils can kill microorganisms, but excessive amount of HNP released during phagocytosis may contribute to inflammatory responses and worsen lung injury. Based on our previous work, we hypothesized that blocking the cell surface purinergic receptor P2Y6 will attenuate the HNP-induced inflammatory responses while maintaining their antimicrobial activity in pneumonia followed by mechanical ventilation.MethodsPlasma HNP levels were measured in patients with pneumonia who received mechanical ventilation and in healthy volunteers. FVB littermate control and HNP transgenic (HNP+) mice were randomized to receive P. aeruginosa intranasally. The P2Y6 antagonist (MRS2578) or vehicle control was given after P. aeruginosa instillation. Additional mice underwent mechanical ventilation at either low pressure (LP) or high pressure (HP) ventilation 48 h after pneumonia, and were observed for 24 h.ResultsPlasma HNP concentration increased in patients with pneumonia as compared to healthy subjects. The bacterial counts in the bronchoalveolar lavage fluid (BALF) were lower in HNP+ mice than in FVB mice 72 h after P. aeruginosa instillation. However, upon receiving HP ventilation, HNP+ mice had higher levels of cytokines and chemokines in BALF than FVB mice. These inflammatory responses were attenuated by the treatment with MRS2578 that did not affect the microbial effects of HNP.ConclusionsHNP exerted dual effects by exhibiting antimicrobial activity in pneumonia alone condition while enhancing inflammatory responses in pneumonia followed by HP mechanical ventilation. Blocking P2Y6 can attenuate the inflammation without affecting the antibacterial property of HNP. The P2Y6 receptor may be a novel therapeutic target in attenuation of the leukocyte-mediated excessive host responses in inflammatory lung diseases.

P2 Purinergic Signaling in the Distal Lung in Health and Disease

“…Hasan et al suggested that desensitization of P2Y 2 and P2X 4 receptors might contribute to the development of VILI [ 95 ]. Zheng et al presented results that in a two-hit mouse model of Pseudomonas aeruginosa pneumonia with high-pressure ventilation a specific P2Y 6 receptor antagonist partially attenuated inflammation and lung injury without interfering with the ability of the immune system to clear the bacteria [ 215 ].…”

<p>Modulation of Human Neutrophil Peptides on <em>P. aeruginosa</em> Killing, Epithelial Cell Inflammation and Mesenchymal Stromal Cell Secretome Profiles</p>

“…We observed that HNP exerted microbicidal properties in clearing P. aeruginosa per se, while also increasing the P. aeruginosa -induced inflammatory response by enhancing IL-8 production in human lung epithelial cells. Since the use of the P2Y 6 antagonist MRS2578 attenuated the HNP-induced IL-8 production and did not affect the microbicidal activity of HNP, our results indicated that 1) HNPs acted on eukaryotic cells through ligand-receptor mechanisms12–14 and kill prokaryotic cells via different approaches such as charge–charge interaction;32 and 2) the ligand-receptor mechanism seemed to override that of charge interaction when eukaryotic and prokaryotic cells were co-existent.…”

“…Levels of HNP are significantly elevated in the blood and body fluid including bronchoalveolar lavage fluid (BALF) and pleural fluid from patients with infections10 and ARDS 6,11. HNP has also been recently shown to act as an immunoregulatory agent due to its ability to induce cytokine production and to activate immune cells through mechanisms of ligand-receptor (i.e., the purinergic receptor P2Y 6 ) interaction 12–14. Thus HNP is not only an important biomarker for infection but also an effector contributing to inflammation in lung microenvironment.…”

Possible role of purinergic signaling in COVID-19

“…The P2Y6 receptor, in turn, was investigated in an animal model in the context of complicated bacterial pneumonia ( Pseudomonas aeruginosa ) and ventilator-induced lung injury [ 31 ]. In patients with COVID-19, there is an inflammatory infiltrate with neutrophils and the application of ventilators is common in severe cases of SARS [ 5 ].…”

“…In patients with COVID-19, there is an inflammatory infiltrate with neutrophils and the application of ventilators is common in severe cases of SARS [ 5 ]. In this research conducted by Zheng et al [ 31 ] on P2Y6R, there was an increment in the α-defensins released by neutrophils, which can kill microorganisms, but in excess contributes to the inflammatory response with high levels of cytokines (IL-1β, IL-6, and TNF-α) and injury to the epithelium and pulmonary endothelium. The intervention occurred through the use of MRS2578, a selective P2Y6R inhibitor, which attenuated the inflammatory state without affecting the anti-bacterial properties of α-defensins.…”