Euglena gracilis–Derived Extracellular Vesicles as a Natural Immune Modulator

Since extracellular vesicles (EVs) possess the same cell therapeutic effect due to its similar characteristics to parent cells, they have emerged as an attractive alternative to cell therapy. Taking advantage of this, a variety of EVs have been developed for tissue regeneration, anti-cancer immunotherapy, and intractable disease treatment. In terms of therapeutic application, microalgae-derived EVs has been of great interest because they contain unique physiologically active substances such as polysaccharides, minerals, vitamins and amino acids. However, most microalgae cells are structured with a strong cell membrane which is not easily cleaved and recombine to form EVs. The derivation of EVs from <i>Euglena gracilis</i> (<i>EG</i>), a microalgae species, warrants special attention due to its relatively flexible cell membrane. Moreover, it can be cultivated in substantial quantities, providing a valuable resource for production purpose while mitigating the risk of viral infection. In this study, we introduce an <i>EG</i>-derived EV (EV<i>_EG</i>) system with an enhanced immune performance. β-1,3-glucan, which is specifically accumulated in <i>EG</i> cells, is a representative substance that activates natural killer cells and macrophages to enhance natural immunity. To efficiently deliver β-1,3-glucan present in the <i>EG</i> to immune cells, the EV<i>_EG</i> are fabricated by cell extrusion method that can convert cells into vesicles by sequentially passing several micro-sized pores. Basically, the endocytosis mechanism study on the EV<i>_EG</i> exhibited notable cellular uptake compared to β-1,3-glucan only. We verified that the EV<i>_EG</i> fabricated in this study notably stimulated the mitogen activated protein kinase (MAPK) pathway, resulting in release of inflammatory mediators such as nitro oxide, cyclooxygenase-2 (COX-2) and pro-inflammatory cytokines. The expression level of these immune factors was appropriately leveled to strengthen the immune system, not excessively inducing immune response such as cytokine storms. We also showed that the -1,3-glucan encapsulated in the EV<i>_EG</i>, like other polysaccharides, was readily recognized by receptors such as Dectin-1 and TLR4 present on immune cell membranes. These results highlight that our EV_EG immunomodulatory system has potential for health promotion and disease treatment in various biomedical applications.