Abstract :
[en] Multidrug-resistant bacteria contribute to various infectious diseases including the challenging disease infective endocarditis. The escalating prevalence of infections caused by antibacterial-resistant strains that are resistant to last-resort antibiotics including vancomycin and daptomycin, urges the need to explore new therapeutic strategies. An emerging avenue of interest involves the repurposing of existing drugs for tackling infections with multidrug-resistant bacteria. One such potential drug that has recently garnered interest is the P2Y12 antagonist ticagrelor.
Ticagrelor is an antiplatelet drug that was reported to have antibacterial properties against Gram-positive and resistant Gram-positive bacteria including methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis. Several retrospective studies in cardiovascular patients support an antibacterial effect of this drug which is not observed for other P2Y12 inhibitors including clopidogrel. Despite the evidence supporting the antibacterial properties of ticagrelor, its mechanism of action remains unclear and will be further elucidated in this thesis.
The first study focused on investigating the prophylactic potential of ticagrelor or clopidogrel against Staphylococcus aureus infective endocarditis using a validated inflammation-induced mouse model. Our research demonstrates that a conventional dose of ticagrelor prevents vegetation formation in a Staphylococcus aureus infective endocarditis mouse model, while clopidogrel did not exhibit the same protective effect. We partly attribute this preventive effect against Staphylococcus aureus infective endocarditis to be related to the antivirulence activity of ticagrelor against Staphylococcus aureus. Ticagrelor inhibited toxin production and prothrombin activity, as well as bacterial adhesion to activated endothelial cells and extracellular matrix proteins including VWF and Fg. Furthermore, our study revealed that ticagrelor downregulates key components within the quorum-sensing accessory gene regulator system of Staphylococcus aureus. Specifically, the expression levels of agrA and agrC, as well as downstream RNAIII, α-hemolysin, and psma effectors, were reduced.
Additionally, ticagrelor impacted the regulation of the histidine kinase SaeR, encoded by the sae locus, and the global regulator mgrA.
The second study focused on elucidating the mechanism of action responsible for the bactericidal properties of ticagrelor, as well as its efficacy against multidrug-resistant bacteria, including strains resistant to last-resort antibiotics vancomycin and daptomycin. We found that ticagrelor induces cell-envelope stress related pathways, indicative for an effect at the level of the cell wall or bacterial membrane. Specifically, we observed a dose-dependent disruptive effect on the bacterial membrane, reminiscent of membrane active agents. At subinhibitory concentrations, ticagrelor induced disturbance of membrane topology, which was reflected by the delocalization of lipid II, a critical peptidoglycan precursor, and MinD, a key regulator of cell division. At the MIC of ticagrelor, membrane depolarization, as well as the formation of membrane dye aggregates, DNA condensation, and an increased uptake of DAPI and membrane impermeant dyes was observed. Whole genome sequencing of in vitro-generated ticagrelor-resistant MRSA clones revealed mutations in genes encoding for ClpP, ClpX, and YjbH. Additionally, lipidomic analysis of these resistant clones displayed changes in levels of the most abundant lipids of the Staphylococcus aureus membrane, e.g., cardiolipins, phosphatidylglycerols, and diacylglycerols. Exogeneous cardiolipin, phosphatidylglycerol, or diacylglycerol antagonized the antibacterial properties of ticagrelor. Notably, ticagrelor retained its antibacterial activity against multidrug-resistant staphylococci including daptomycin- and vancomycin-resistant strains and enhanced the antibacterial activity of these last-resort antibiotics.
Our findings support the potential of ticagrelor as a prophylactic antibacterial agent in cardiovascular patients at high risk of infection, who need antiplatelet therapy. Furthermore, it underscores the potential of ticagrelor as an adjunct therapy in the management of infective endocarditis, warranting further clinical investigation.
