Microparticles and exosomes in cell-cell communication

Growing evidence indicates that cells are able to communicate with neighbouring and distant cells in the body by production of extracellular vesicles (EV). EV are classified according to their size and mechanisms of formation. Exosomes and microparticles are the most extensively studied clinically relevant forms of EV, and they often reflect the activation status of the parent cell, by carrying similar surface markers and cargo. Because of these molecular characteristics, EV are considered to be mediators of cell activation by transferring molecules (e.g., proteins, lipids, and nucleic acids) to neighbouring or distant cell populations. Increased levels of circulating EV have been observed in various diseases, including hypertension, atherosclerosis, kidney diseases, and cancer. In this chapter, we will address the formation of different EV and their importance in cell-cell communication, controlling basic cellular functions in homeostatic and pathologic conditions associated with cardiovascular diseases. In addition, we highlight their role as biomarkers and discuss the potential of EV as therapeutic tools

Exosomes are released by bystander cells exposed to radiation-induced biophoton signals: Reconciling the mechanisms mediating the bystander effect

OBJECTIVE:The objective of our study was to explore a possible molecular mechanism by which ultraviolet (UV) biophotons could elicit bystander responses in reporter cells and resolve the problem of seemingly mutually exclusive mechanisms of a physical UV signal & a soluble factor-mediated bystander signal. METHODS:The human colon carcinoma cell line, HCT116 p53 +/+, was directly irradiated with 0.5 Gy tritium beta particles to induce ultraviolet biophoton emission. Bystander cells were not directly irradiated but were exposed to the emitted UV biophotons. Medium was subsequently harvested from UV-exposed bystander cells. The exosomes extracted from this medium were incubated with reporter cell populations. These reporter cells were then assayed for clonogenic survival and mitochondrial membrane potential with and without prior treatment of the exosomes with RNase. RESULTS:Clonogenic cell survival was significantly reduced in reporter cells incubated with exosomes extracted from cells exposed to secondarily-emitted UV. These exosomes also induced significant mitochondrial membrane depolarization in receiving reporter cells. Conversely, exosomes extracted from non-UV-exposed cells did not produce bystander effects in reporter cells. The treatment of exosomes with RNase prior to their incubation with reporter cells effectively abolished bystander effects in reporter cells and this suggests a role for RNA in mediating the bystander response elicited by UV biophotons and their produced exosomes. CONCLUSION:This study supports a role for exosomes released from UV biophoton-exposed bystander cells in eliciting bystander responses and also indicates a reconciliation between the UV-mediated bystander effect and the bystander effect which has been suggested in the literature to be mediated by soluble factors