ABSTRACT
Resident-tissue macrophages (RTMs) arise from embryonic precursors1,2, yet the developmental signals that shape their longevity remain largely unknown. Here we demonstrate in mice genetically deficient in 12-lipoxygenase and 15-lipoxygenase (Alox15-/- mice) that neonatal neutrophil-derived 12-HETE is required for self-renewal and maintenance of alveolar macrophages (AMs) during lung development. Although the seeding and differentiation of AM progenitors remained intact, the absence of 12-HETE led to a significant reduction in AMs in adult lungs and enhanced senescence owing to increased prostaglandin E2 production. A compromised AM compartment resulted in increased susceptibility to acute lung injury induced by lipopolysaccharide and to pulmonary infections with influenza A virus or SARS-CoV-2. Our results highlight the complexity of prenatal RTM programming and reveal their dependency on in trans eicosanoid production by neutrophils for lifelong self-renewal.
Subject(s)
12-Hydroxy-5,8,10,14-eicosatetraenoic Acid , Cell Self Renewal , Macrophages, Alveolar , Neutrophils , Animals , Mice , 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid/metabolism , Acute Lung Injury , Animals, Newborn , Arachidonate 12-Lipoxygenase/deficiency , Arachidonate 15-Lipoxygenase/deficiency , COVID-19 , Influenza A virus , Lipopolysaccharides , Lung/cytology , Lung/virology , Macrophages, Alveolar/cytology , Macrophages, Alveolar/metabolism , Neutrophils/metabolism , Orthomyxoviridae Infections , Prostaglandins E , SARS-CoV-2 , Disease SusceptibilityABSTRACT
OBJECTIVE: To determine if inhaled and intranasal ciclesonide are superior to placebo at decreasing respiratory symptoms in adult outpatients with covid-19. DESIGN: Randomised, double blind, placebo controlled trial. SETTING: Three Canadian provinces (Quebec, Ontario, and British Columbia). PARTICIPANTS: 203 adults aged 18 years and older with polymerase chain reaction confirmed covid-19, presenting with fever, cough, or dyspnoea. INTERVENTION: Participants were randomised to receive either inhaled ciclesonide (600 µg twice daily) and intranasal ciclesonide (200 µg daily) or metered dose inhaler and nasal saline placebos for 14 days. MAIN OUTCOME MEASURES: The primary outcome was symptom resolution at day 7. Analyses were conducted on the modified intention-to-treat population (participants who took at least one dose of study drug and completed one follow-up survey) and adjusted for stratified randomisation by sex. RESULTS: The modified intention-to-treat population included 203 participants: 105 were randomly assigned to ciclesonide (excluding two dropouts and one loss to follow-up) and 98 to placebo (excluding three dropouts and six losses to follow-up). The median age was 35 years (interquartile range 27-47 years) and 54% were women. The proportion of participants with resolution of symptoms by day 7 did not differ significantly between the intervention group (42/105, 40%) and control group (34/98, 35%); absolute adjusted risk difference 5.5% (95% confidence interval -7.8% to 18.8%). Results might be limited to the population studied, which mainly included younger adults without comorbidities. The trial was stopped early, therefore could have been underpowered. CONCLUSION: Compared with placebo, the combination of inhaled and intranasal ciclesonide did not show a statistically significant increase in resolution of symptoms among healthier young adults with covid-19 presenting with prominent respiratory symptoms. As evidence is insufficient to determine the benefit of inhaled and intranasal corticosteroids in the treatment of covid-19, further research is needed. TRIAL REGISTRATION: ClinicalTrials.gov NCT04435795.