Large-Scale, Ion-Current-Based Proteomic Investigation of the Rat Striatal Proteome in a Model of Short- and Long-Term Cocaine Withdrawal

Given
the tremendous detriments of cocaine dependence, effective
diagnosis and patient stratification are critical for successful intervention
yet difficult to achieve due to the largely unknown molecular mechanisms
involved. To obtain new insights into cocaine dependence and withdrawal,
we employed a reproducible, reliable, and large-scale proteomics approach
to investigate the striatal proteomes of rats (n =
40, 10 per group) subjected to chronic cocaine exposure, followed
by either short- (WD1) or long- (WD22) term withdrawal. By implementing
a surfactant-aided precipitation/on-pellet digestion procedure, a
reproducible and sensitive nanoLC-Orbitrap MS analysis, and an optimized
ion-current-based MS1 quantification pipeline, >2000 nonredundant
proteins were quantified confidently without missing data in any replicate.
Although cocaine was cleared from the body, 129/37 altered proteins
were observed in WD1/WD22 that are implicated in several biological
processes related closely to drug-induced neuroplasticity. Although
many of these changes recapitulate the findings from independent studies
reported over the last two decades, some novel insights were obtained
and further validated by immunoassays. For example, significantly
elevated striatal protein kinase C activity persisted over the 22
day cocaine withdrawal. Cofilin-1 activity was up-regulated in WD1
and down-regulated in WD22. These discoveries suggest potentially
distinct structural plasticity after short- and long-term cocaine
withdrawal. In addition, this study provides compelling evidence that
blood vessel narrowing, a long-known effect of cocaine use, occurred
after long-term but not short-term withdrawal. In summary, this work
developed a well-optimized paradigm for ion-current-based quantitative
proteomics in brain tissues and obtained novel insights into molecular
alterations in the striatum following cocaine exposure and withdrawal.