Ricardo José1, Andrew Williams2, Michal Sulikowski2, David Brealey3, Jeremy Brown2, Rachel Chambers2. 1. Centre for Inflammation and Tissue Repair, University College London, London, UK. Electronic address: r.jose@ucl.ac.uk. 2. Centre for Inflammation and Tissue Repair, University College London, London, UK. 3. Department of Intensive Care Medicine, University College London Hospital, London, UK.
Abstract
BACKGROUND: Community-acquired pneumonia is commonly caused by Streptococcus pneumoniae, which is associated with excessive neutrophilic inflammation. The high-affinity thrombin receptor, proteinase-activated receptor 1 (PAR1), has been implicated in mediating the interplay between coagulation and inflammation. However, its role during S pneumoniae-induced neutrophilic inflammation, and the mechanisms for neutrophil recruitment in this context are poorly understood. We aimed to investigate the role of neutrophilic inflammation and PAR1 in S pneumoniae-induced pneumonia. METHODS: We used the most clinically advanced PAR-1 antagonist, SCH530348, and performed neutrophil depletion and chemokine neutralisation studies in two murine models. We also did translational studies to examine CXC and CC chemokine receptor expression by flow cytometry on neutrophils in blood and bronchoalveolar lavage fluid (BALF) from mechanically ventilated patients with acute respiratory distress syndrome induced by community-acquired pneumonia. FINDINGS: S pneumoniae infection led to activation of coagulation, increased neutrophil recruitment, and increased PAR-1 expression. By contrast with neutrophil depletion, PAR1 antagonist treatment significantly reduced neutrophil recruitment (mean difference 26·7 × 10(3) cells per mL [SE 4·9] at 4 h, p=0·0002; and 149·3 [41·4] at 24 h, p=0·0032) without being detrimental to host defence. Markers of alveolar leak, coagulation activation, and proinflammatory cytokines and chemokines (interleukin 1β, CXCL1, CCL2, and CCL7) were attenuated. Neutralisation studies demonstrated that interleukin 1β and CCL7, but not CXCL1 and CCL2, had a key role in neutrophil recruitment in this model. In patients with acute respiratory distress syndrome induced by community-acquired pneumonia (n=10), CXCR1 and CXCR2 expression on BALF neutrophils was higher than in controls (n=3) (median difference in mean fluorescence intensity [MFI] 703 arbitrary units [p=0·0699] for CXCR1 and 658·7 [p=0·0280] for CXCR2). The expression of CXCR1 was decreased on neutrophils from BALF compared with blood (median difference in MFI 1337, p=0·0020) and that of CXCR2, CCR1, CCR2, and CCR3 was increased (125·5, p=0·0020; 335·1, p=0·0020; 116, p=0·0068; and 275, p=0·0020; respectively). INTERPRETATION: These findings suggest that clinically available PAR1 antagonists might offer a novel therapeutic approach for prevention and management of excessive neutrophilic inflammation and alveolar barrier dysfunction in pneumococcal pneumonia without compromising host defence. Furthermore, these data highlight a role for chemokine receptor switching in acute respiratory distress syndrome induced by community-acquired pneumonia. FUNDING: Wellcome Trust.
BACKGROUND: Community-acquired pneumonia is commonly caused by Streptococcus pneumoniae, which is associated with excessive neutrophilic inflammation. The high-affinity thrombin receptor, proteinase-activated receptor 1 (PAR1), has been implicated in mediating the interplay between coagulation and inflammation. However, its role during S pneumoniae-induced neutrophilic inflammation, and the mechanisms for neutrophil recruitment in this context are poorly understood. We aimed to investigate the role of neutrophilic inflammation and PAR1 in S pneumoniae-induced pneumonia. METHODS: We used the most clinically advanced PAR-1 antagonist, SCH530348, and performed neutrophil depletion and chemokine neutralisation studies in two murine models. We also did translational studies to examine CXC and CC chemokine receptor expression by flow cytometry on neutrophils in blood and bronchoalveolar lavage fluid (BALF) from mechanically ventilated patients with acute respiratory distress syndrome induced by community-acquired pneumonia. FINDINGS: S pneumoniae infection led to activation of coagulation, increased neutrophil recruitment, and increased PAR-1 expression. By contrast with neutrophil depletion, PAR1 antagonist treatment significantly reduced neutrophil recruitment (mean difference 26·7 × 10(3) cells per mL [SE 4·9] at 4 h, p=0·0002; and 149·3 [41·4] at 24 h, p=0·0032) without being detrimental to host defence. Markers of alveolar leak, coagulation activation, and proinflammatory cytokines and chemokines (interleukin 1β, CXCL1, CCL2, and CCL7) were attenuated. Neutralisation studies demonstrated that interleukin 1β and CCL7, but not CXCL1 and CCL2, had a key role in neutrophil recruitment in this model. In patients with acute respiratory distress syndrome induced by community-acquired pneumonia (n=10), CXCR1 and CXCR2 expression on BALF neutrophils was higher than in controls (n=3) (median difference in mean fluorescence intensity [MFI] 703 arbitrary units [p=0·0699] for CXCR1 and 658·7 [p=0·0280] for CXCR2). The expression of CXCR1 was decreased on neutrophils from BALF compared with blood (median difference in MFI 1337, p=0·0020) and that of CXCR2, CCR1, CCR2, and CCR3 was increased (125·5, p=0·0020; 335·1, p=0·0020; 116, p=0·0068; and 275, p=0·0020; respectively). INTERPRETATION: These findings suggest that clinically available PAR1 antagonists might offer a novel therapeutic approach for prevention and management of excessive neutrophilic inflammation and alveolar barrier dysfunction in pneumococcal pneumonia without compromising host defence. Furthermore, these data highlight a role for chemokine receptor switching in acute respiratory distress syndrome induced by community-acquired pneumonia. FUNDING: Wellcome Trust.
Authors: Kruthika Sundaram; Mohd Akhlakur Rahman; Srabani Mitra; Daren L Knoell; Shireen A Woodiga; Samantha J King; Mark D Wewers Journal: PLoS One Date: 2016-09-06 Impact factor: 3.240
Authors: Luciana P Tavares; Cristiana C Garcia; Marina G Machado; Celso M Queiroz-Junior; Adeline Barthelemy; François Trottein; Marilda M Siqueira; Laura Brandolini; Marcello Allegretti; Alexandre M Machado; Lirlândia P de Sousa; Mauro M Teixeira Journal: Front Immunol Date: 2017-12-13 Impact factor: 7.561