Monocytes and macrophages transmit inflammatory signals to each other via extracellular vesicles

Monocytes and macrophages play an important role in the development of inflammatory diseases, including sepsis, etc. In addition to their role as “scavengers,” macrophages secrete various substances (mainly cytokines and chemokines), which have a systemic effect and modulate the microenvironment of the inflammatory focus. Disruption of their normal function can cause various immune pathologies and changes in tissue homeostasis. Macrophages are able to transmit signals to other cells in the area of inflammation, including various cytokines and other compounds. Usually, they are secreted directly into the extracellular space. However, the lifetime and range of action of these substances may be limited. An alternative method of intercellular communication is the packaging of substances into extracellular vesicles, which can help in signal propagation. Extracellular vesicles are small particles with a bilayer lipid membrane that transport various biologically active substances. There are different types of extracellular vesicles, each of which can have its own specific effect on other cells. Due to the presence of specific receptors on the surface of the vesicles, they can make selective delivery of biological molecules to certain cells. Vesicles can contain various components, such as nucleic acids, proteins, lipids, and even individual cell organelles. Therefore, it is not surprising that vesicles are able to modulate physiological processes in the body and be involved in the pathogenesis of various diseases. Establishing the mechanisms of vesicle participation in the development of inflammatory diseases, including chronic ones, is extremely important. The aim of the present study was to determine whether extracellular vesicles are capable of modulating the immune response. To do this, we assessed cytokine secretion by macrophages treated with vesicles from LPS-stimulated monocytes and macrophages. It was found that cells that received vesicles from LPS-activated monocytes and macrophages secrete more pro-inflammatory signaling molecules: the cytokine IL-6 and the chemokine IL-8. The results demonstrate that intercellular interaction and transmission of the inflammatory signal of monocytic cells also occurs through extracellular vesicles. In the future, additional research is needed to understand the full picture of what substances in the extracellular vesicles of monocytes and macrophages allow them to have an immunomodulatory effect not only on each other, but also on other types of cells.