Abstract P3163: Exosomes From Pseudomonas Aeruginosa Infected Macrophages Drives Cardiomyocyte Contractile Dysfunction

Abstract

Rationale: Pseudomonas aeruginosa ( P.a. ) infection is very common in ICU patients and is known to increase the mortality rate. Our lab demonstrated that P.a. infection caused severe cardiac dysfunction without disseminating into the heart. However, the mechanism of cardiac complication during P. a. infection is not known; understanding this is critical for the development of host-protective therapy. Thus, we hypothesize that cardiac dysfunction caused by P.a. is either mediated through systemic inflammation and/or the release of exosomes and bacterial outer membrane vesicles from infected cells. Objective: Identify the mechanism of cardiac inflammation and cardiac dysfunction caused by P.a. infection. Methods and Results: To investigate whether P.a. infection causes cardiomyocyte contractile dysfunction, we exposed the hiPSC-CMs with P.a. and monitored the hiPSC-CMs electrical activity using Multi-electrode array (MEA). We found that the contraction of hiPSC-CMs stopped completely at 8h post-infection. Next, to test whether the inflammatory cytokines, exosomes, and bacterial OMVs released upon infection affect contractile function, we exposed the hiPSC-CMs with conditioned media harvested from P.a. infected hMDMs. Our data revealed that exposure of conditioned media to hiSPC-CMs caused severe contractile dysfunction and arrhythmia. Also, we found that conditioned media contains an increased level of inflammatory cytokines IL-1β, TNFα, and IL-6 along with exosomes and OMVs. To test whether heat inactivation of conditioned media preserves the hiPSC-CMs, we inactivated the media and stimulated the cells. Our data suggest that the heat-inactivated conditioned media impaired the hiPSC-CMs contractility, due to the release of exosomal content. Furthermore, based on LC-MS/MS analysis of purified exosomes from P.a. infected hMDMs, we identified that exosomes are packed with bacterial toxins and immunogenic antigens. Conclusion: Our data demonstrate that P.a. releases OMVs and bacterial toxins into the host cells, which are packed in exosomes. Though, infected macrophages release inflammatory cytokines, the main source for hiPSC-CM contractile dysfunction is the release of exosomes packed with bacterial toxins and antigens.