Extracellular vesicles and cytokines released from Pseudomonas aeruginosa infected macrophages activate cardiac fibroblasts 2259917

Introduction Pseudomonas aeruginosa (P. aeruginosa) is a gram-negative, opportunistic pathogen and a major cause of severe pneumonia. Infections caused by P. aeruginosa carry a high mortality rate, ranging from 32% to 42.8%. Notably, the risk of pneumonia is strongly associated with cardiovascular diseases (CVD), particularly heart failure. Methods In our previous studies, we demonstrated that P. aeruginosa lung infection leads to significant cardiac electrical disturbances and left ventricular (LV) dysfunction, despite minimal bacterial dissemination to the heart. To further investigate the underlying mechanisms, we identified that extracellular vesicles (EVs) released from both host cells, used LC-MS/MS to identify the EV content, and systemically administered outer membrane vesicles (OMVs) via tail vein injection to study the effects in vivo. Cardiac fibroblasts, key components of heart tissues, play a critical role in cardiac inflammation and damage upon activation. Using human cardiac fibroblasts (HCFs), we examined the effects of conditioned media (C-media), which contains both cytokines and EVs, on fibroblast activation. Results Our data revealed that exposure to C-media significantly elevated inflammatory markers CXCL10, IRF1, CXCL2, TNFα, and IL6 at both 6 and 24 hours, as detected by next-generation mRNA sequencing and confirmed by ELISA and qPCR. The EVs carried bacterial products, including toxins (as shown by LC-MS/MS), and tail vein injection of the OMVs resulted in pronounced LV dysfunction and increased mortality. Conclusion Mechanistically, these findings suggest that EVs upregulate the TNF signaling pathway, leading to increased cytokine production, leukocyte recruitment, and severe cardiac inflammation and dysfunction. In summary, our data indicate that P. aeruginosa infection induces the release of EVs that activate cardiac fibroblasts and impair cardiomyocyte contractility, contributing to cardiac dysfunction. Funding Source AI145262 Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)