We investigated the changes in redox state and protein expression in selected parts of the rat brain induced by a 4 week administration of morphine (10 mg/kg/day). We found a significant reduction in lipid peroxidation that mostly persisted for 1 week after morphine withdrawal. Morphine treatment led to a significant increase in complex II in the cerebral cortex (Crt), which was accompanied by increased protein carbonylation, in contrast to the other brain regions studied. Glutathione levels were altered differently in the different brain regions after morphine treatment. Using label-free quantitative proteomic analysis, we found some specific changes in protein expression profiles in the Crt, hippocampus, striatum, and cerebellum on the day after morphine withdrawal and 1 week later. A common feature was the upregulation of anti-apoptotic proteins and dysregulation of the extracellular matrix. Our results indicate that the tested protocol of morphine administration has no significant toxic effect on the rat brain. On the contrary, it led to a decrease in lipid peroxidation and activation of anti-apoptotic proteins. Furthermore, our data suggest that long-term treatment with morphine acts specifically on different brain regions and that a 1 week drug withdrawal is not sufficient to normalize cellular redox state and protein levels.

• Keywords
• brain, morphine, oxidative stress, proteomics, withdrawal,
• Publication type
• Journal Article MeSH

The interactions between TRPV1 and µ-opioid receptors (MOR) have recently attracted much attention because these two receptors play important roles in pain pathways and can apparently modulate each other's functioning. However, the knowledge about signaling interactions and crosstalk between these two receptors is still limited. In this study, we investigated the mutual interactions between MOR and TRPV1 shortly after their activation in HEK293 cells expressing these two receptors. After activation of one receptor we observed significant changes in the other receptor's lateral mobility and vice versa. However, the changes in receptor movement within the plasma membrane were not connected with activation of the other receptor. We also observed that plasma membrane β-arrestin 2 levels were altered after treatment with agonists of both these receptors. Knockdown of β-arrestin 2 blocked all changes in the lateral mobility of both receptors. Furthermore, we found that β-arrestin 2 can play an important role in modulating the effectiveness of ERK1/2 phosphorylation after activation of MOR in the presence of TRPV1. These data suggest that β-arrestin 2 and ERK1/2 are important mediators between these two receptors and their signaling pathways. Collectively, MOR and TRPV1 can mutually affect each other's behavior and β-arrestin 2 apparently plays a key role in the bidirectional crosstalk between these two receptors in the plasma membrane.

• Keywords
• ERK1/2, TRPV1, biased signaling, receptor lateral mobility, β-arrestin 2, μ-opioid receptor,
• MeSH
• Arrestins metabolism   MeSH
• beta-Arrestin 2 metabolism   physiology   MeSH
• beta-Arrestins metabolism   MeSH
• Cell Membrane metabolism   physiology   MeSH
• Phosphorylation MeSH
• HEK293 Cells MeSH
• TRPV Cation Channels metabolism   physiology   MeSH
• Humans MeSH
• MAP Kinase Signaling System physiology   MeSH
• Morphine metabolism   MeSH
• Analgesics, Opioid metabolism   MeSH
• Receptors, Opioid, mu metabolism   physiology   MeSH
• Receptors, Opioid metabolism   MeSH
• Signal Transduction MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Arrestins MeSH
• beta-Arrestin 2 MeSH
• beta-Arrestins MeSH
• TRPV Cation Channels MeSH
• Morphine MeSH
• Analgesics, Opioid MeSH
• Receptors, Opioid, mu MeSH
• Receptors, Opioid MeSH
• TRPV1 protein, human MeSH Browser