Protracted morphine withdrawal induces upregulation of peroxiredoxin II and reduces 14-3-3 protein levels in the rat brain cortex and hippocampus.

Protracted opioid withdrawal is considered to be a traumatic event with many adverse effects. However, little attention is paid to its consequences on the protein expression in the rat brain. A better understanding of the changes at the molecular level is essential for designing future innovative drug therapies. Our previous proteomic data indicated that long-term morphine withdrawal is associated with altered proteins functionally involved in energy metabolism, cytoskeletal changes, oxidative stress, apoptosis, or signal transduction. In this study, we selected peroxiredoxin II (PRX II) as a marker of oxidative stress, 14-3-3 proteins as adaptors, and creatine kinase-B (CK-B) as a marker of energy metabolism to detect their amounts in the brain cortex and hippocampus isolated from rats after 3-month (3 MW) and 6-month morphine withdrawal (6 MW). Methodically, our work was based on immunoblotting accompanied by 2D resolution of PRX II and 14-3-3 proteins. Our results demonstrate significant upregulation of PRX II in the rat brain cortex (3-fold) and hippocampus (1.3-fold) after 3-month morphine abstinence, which returned to the baseline six months since the drug was withdrawn. Interestingly, the level of 14-3-3 proteins was downregulated in both brain areas in 3 MW samples and remained decreased only in the brain cortex of 6 MW. Our findings suggest that the rat brain cortex and hippocampus exhibit the oxidative stress-induced vulnerability represented by compensatory upregulation of PRX II after three months of morphine withdrawal.