ABSTRACT
While the development of addictive behaviors and the associated short- and long-term neuroadaptations after
exposure to cocaine have been extensively studied, the mechanisms of cocaine addiction have not been fully
elucidated. Using a novel method developed in our laboratory, we have isolated exosomes from the mouse
brain and found in preliminary studies that chronic cocaine treatment increased levels of exosomes in the brain
and changed the protein and lipid content of exosomes. Since cocaine has been shown to cause dysfunctions
in the endosomal/autophagic/lysosomal system, we hypothesize that cocaine enhances exosome secretion in
order to release accumulation of cellular materials caused by the disturbed degradation pathway. However,
recent studies indicate that exosomes also serve as intercellular communication vehicles. Therefore, we
suggest that exosome secretion is involved in the addiction process by transferring addiction-related proteins,
lipids, and RNAs to target cells. We propose to test this hypothesis by characterizing the exosomes isolated
from the brain of mice treated with cocaine or saline as control. Time course of changes in the level and cargo
compositions of exosomes during non-contingent and contingent cocaine administration, followed by
withdrawal (Aim 1), brain regional comparison of exosomal characteristics (Aim 2), and the direct effects of
isolated exosomes on cocaine-related cellular and behavioral changes (Aim 3) would identify exosome-
dependent and brain region specific mechanisms that underlie addictive behaviors. We have identified four
exosomal populations, and in Aim 1 we propose to characterize the exosome populations affected by acute
and chronic cocaine treatment. We will determine secretion levels of exosomes and analyze their cocaine-
dependent proteomics, lipidomics, and RNA profiles. While global analyses of these molecules are our goal, a
special focus will be given to BDNF, NMDA e2, and gangliosides based on our preliminary results that have
shown cocaine-induced changes in the levels of these molecules in exosomes. In Aim 2 we will identify brain
regions and cellular changes involved in cocaine-induced secretion of exosomes containing cocaine-altered
proteins, lipids, and RNAs in order to determine the role of exosomes in the induction, sensitization, or
withdrawal phases of addiction. In Aim 3 we will evaluate roles of exosomes in cocaine addiction. The effects
of exosomes derived from cocaine-treated mice, as well as, from in vitro cocaine-treated primary cultured
cortical neurons and glial cells, on addiction-related molecular, cellular, and behavioral changes will be tested
in naïve mice. Future studies will examine whether some of the cocaine-induced changes in proteins, lipids,
and RNAs, found in brain exosomes are also observed in cerebrospinal fluid and serum exosomes isolated
from cocaine-addicted humans. The studies proposed here aim to give an insight into mechanisms behind the
role of exosomes in cocaine addiction and may lead to finding new targets for addiction therapy and/or new
biomarkers for cocaine addiction and withdrawal.