Affiliation:
1. University of Alabama at Birmingham
Abstract
Abstract
Background
Bacterial pneumonia and related lung injury are among the most frequent causes of mortality in intensive care units, but also inflict serious and prolonged respiratory complications among survivors. Given that endoplasmic reticulum (ER) stress is a hallmark of sepsis-related alveolar epithelial cell (AEC) dysfunction, we tested if AMP-activated protein kinase (AMPK) affects recovery from ER stress and apoptosis of AECs during post-bacterial infection.
Methods
In a murine model of lung injury by P. aeruginosa non-lethal infection, therapeutic interventions included AMPK activator metformin or GSK-3β inhibitor Tideglusib for 96 hours. Recovery from AEC injury was evidenced by accumulation of soluble T-1α (AEC Type 1 marker) in BAL fluids along with fluorescence analysis of ER-stress (CHOP) and apoptosis (TUNEL) in lung sections. AMPK phosphorylation status was determined via Immunoblot analysis from lung homogenates. Macrophage-dependent clearance of apoptotic cells was determined using flow cytometry assay.
Results
P. aeruginosa-induced lung injury resulted in accumulation of neutrophils and cellular debris in the alveolar space along with persistent (96 hours) ER-stress and apoptosis of AECs. While lung infection triggered AMPK inactivation (de-phosphorylation of Thr172-AMPK), metformin and Tideglusib promptly restored the AMPK activation status. In post infected mice, AMPK activation reduced indices of lung injury, ER stress and related apoptosis of AECs, as early as 24 hours post administration of AMPK activators. In addition, we demonstrate that the extent of apoptotic cell accumulation is also dependent on AMPK-mediated clearance of apoptotic cells by macrophages.
Conclusions
Our study provides important insights into AMPK function in the preservation of AEC viability after bacterial infection, in particular due reduction of ER-stress and apoptosis, thereby promoting effective recovery from lung injury after pneumonia.
Publisher
Research Square Platform LLC
Reference64 articles.
1. Sepsis and septic shock;Hotchkiss RS;Nat Rev Dis Primers,2016
2. Acute lung injury and the acute respiratory distress syndrome: a clinical review;Wheeler AP;Lancet,2007
3. Acute respiratory distress syndrome in adults: diagnosis, outcomes, long-term sequelae, and management;Gorman EA;Lancet,2022
4. Acute respiratory distress syndrome: causes, pathophysiology, and phenotypes;Bos LDJ;Lancet,2022
5. Sepsis-induced immune dysfunction: can immune therapies reduce mortality?;Delano MJ;J Clin Invest,2016