Protein Profiling of Plasma and Synaptic Interactomes Following Acute and Chronic Withdrawal from Cocaine in Rhesus Monkeys

Scott E. Hemby, Wake Forest University School of Medicine

Cocaine abuse and dependence in the United States continues to be a major public health concern yet significant obstacles remain for the appropriate diagnosis and treatment of individuals suffering from addictive disorders. Research efforts have focused primarily on the development and refinement of toxicological assays for detecting cocaine as a measure of recent cocaine use and on the identification of genetic markers indicative of a predisposition to cocaine abuse. A continuing unmet medical need is the identification of peripheral biological markers that can assist with the objective diagnosis, assessment of current severity, risk stratification, and monitoring the progression of substance abuse and response to treatment. Moreover, biomarkers could also be used as surrogates of neuroadaptive alterations associated with chronic drug use – helping guide clinical trials for cocaine addiction and once reliable drug treatments are established also for treatment decisions in patient populations.

Therefore the goal of this research will be to identify and correlate plasma biomarkers with biochemical changes occurring in reward relevant brain regions during abstinence from chronic cocaine self-administration in rhesus monkeys. We propose to provide a longitudinal assessment of the plasma proteome as a function of cocaine self-administration and during a thirty day period of cocaine abstinence. Samples will be analyzed using unbiased complimentary proteomic methods (2D-DIGE and iTRAQ/MDLC) and appropriate validation methods. Multivariate statistical analysis approaches will be used to delineate a finite set of proteins with the greatest degree of distinction between intake and abstinence and also between acute and chronic withdrawal. Chronic cocaine administration induces neuroadaptive changes that lead to alterations in regional brain function that may underlie persistent drug taking behaviors, “craving” and relapse. These changes are due in part to alterations in glutamatergic signaling in the ventral striatum and prefrontal cortex. Using immunoprecipitation techniques, we will isolate specific NMDA and AMPA receptor subunits and associated proteins in the ventral striatum and prefrontal cortical regions at one and thirty days of abstinence from cocaine to determine changes in the receptor-associated interactomes. The expression of peripheral biomarkers identified in Aim 1 will be correlated with neurobiological changes identified in Aim 2. We anticipate these strategies will provide a preliminary biosignature of cocaine use/withdrawal and correlated neuronal dysregulation that ultimately can be used as a diagnostic and prognostic tool in the treatment of cocaine addiction.