Pneumonia induced rise in glucagon promotes endothelial damage and vascular thrombogenicity

Abstract

BackgroundRecent studies have demonstrated a link between respiratory infections and increased short-term risk of cardiovascular disease (CVD). However, the molecular mechanisms underlying the increased cardiovascular risk after respiratory infections are only poorly understood. Here, we aimed to decipher pathophysiological circuits of pneumonia associated CVD in experimental models of bacterial pneumonia and vascular injury.MethodsC57BL/6J mice were exposed to intranasal inoculation with eitherStreptococcus pneumoniae(S. pneumoniae) serotype 4 (pneumonia group) or phosphate buffered saline (PBS) (control group). 24 hourspost infectionem(p.i.) mice were treated with antibiotics until the end of the study. On day 7 p.i. carotid artery injury (CI) was induced by electric stimulation and vascular repair was analyzed 3 days after injury. Plasma proteomic analyses were performed by Olink Bioscience. Primary human aortic endothelial cells (HAECs) were used to study alterations of the endothelial functional properties, bioenergetic state and thrombogenic potentialin vitro. Intravital fluorescence microscopy equipped with video recording was applied to measure thrombus formation in real-time.ResultsBacterial pneumonia impaired repair capacity of the endothelium after vascular injury. Proteomic analyses revealed significantly higher plasma levels of glucagon in mice after recovery from pneumonia relative to controls, which was further confirmed by ELISA detecting glucagon. Mechanistically, we found that glucagon impaired mitochondrial bioenergetics and migratory potential in HAECs and induced an inflammatory response. Moreover, glucagon fostered vascular thrombogenicity as demonstrated by increased thrombocyte adhesion to HAECs and accelerated carotid artery thrombus formationin vivo. Acute application of the glucagon-like peptide-1 receptor (GLP1-R) agonist liraglutide to lower blood glucagon levels, restored vascular repair potential and attenuated vascular thrombogenicity in mice with pneumonia.ConclusionsOur findings reveal a novel mechanism that associates elevated circulatory glucagon levels to dysfunctional endothelium and increased vascular thrombogenicity, suggesting glucagon signaling as a potential therapeutic target to prevent pneumonia-induced cardiovascular events.Graphical Abstract