PB1358 - Extracellular vesicle lipid functions in inflammation and endothelial dysfunction

Background: Extracellular Vesicles (EVs) of different origins are involved in many inflammatory processes. Their functions rely on the respective cargo, which depends on the type and state of the originating cells. While EV nucleic acids and proteins are investigated extensively in the literature, the characterization of EV lipids is not sufficiently understood. Bioactive lipids such as PUFAs or eicosanoids however play a significant role in the propagation and resolution of inflammation, platelet reactivity, and clot formation.The role of EVs in the mediation of these lipid effects remains a largely unanswered question.

Aims: In our study, we hypothesized that the EV lipid distribution changes during inflammation. We further investigated whether such changes have a functional relevance on cell adhesion, endothelial dysfunction, and the propagation of inflammation.

Methods: EVs were purified by Sequential Filtration. PUFA and Eicosanoid profiles in the EV preparations were assessed using LC-MS/MS. The functional relevance was investigated using RT-qPCR, cell adhesion assays, etc. 12-LOX was inhibited by ML355.

Results: The lipid profiles of macrophage-derived EVs differed largely depending on the polarization of the originating macrophages. M1-derived EVs showed decreased levels of arachidonic acid but increased levels of ARA-derived 12-and 15LOX and products, particularly 8/12-HETE. Both M1 EVs and 8/12 HETE induced expression of pro-inflammatory chemokines in target cells. M1 EVs induced monocyte adhesion, monocyte migration, and endothelial barrier dysfunction. These effects were significantly lower in 12-LOX-metabolite-free M1 EVs.

Conclusion(s): Our results show that differing EV lipid profiles during inflammation are functionally relevant: 12-LOX inhibition of pro-inflammatory macrophages reduces pro-inflammatory effects of their EVs. This indicates that EVs mediate 12-LOX dependent endothelial activation and expression of pro-inflammatory adhesion markers. We hypothesize that the EV lipids are contributing factors towards the development of endothelial dysfunction, and the genesis of atherosclerosis.