L-DOPA-induced dyskinesia is associated with regional increase of striatal dynorphin peptides as elucidated by imaging mass spectrometry

Abstract

Opioid peptides are involved in various pathophysiological processes, including algesia, epilepsy, and drug dependence. A strong association between L-DOPA-induced dyskinesia (LID) and elevated prodynorphin mRNA levels has been established in both patients and in animal models of Parkinson's disease, but to date the endogenous prodynorphin peptide products have not been determined. Here, matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) was used for characterization, localization, and relative quantification of striatal neuropeptides in a rat model of LID in Parkinson's disease. MALDI IMS has the unique advantage of high sensitivity and high molecular specificity, allowing comprehensive detection of multiple molecular species in a single tissue section. Indeed, several dynorphins and enkephalins could be detected in the present study, including dynorphin A(1-8), dynorphin B, ␣-neoendorphin, MetEnkRF, MetEnkRGL, PEnk (198 -209, 219 -229). IMS analysis revealed elevated levels of dynorphin B, ␣-neoendorphin, substance P, and PEnk (220 -229) in the dorsolateral striatum of high-dyskinetic animals compared with low-dyskinetic and lesion-only control rats. Furthermore, the peak-intensities of the prodynorphin derived peptides, dynorphin B and ␣-neoendorphin, were strongly and positively correlated with LID severity. Interestingly, these LID associated dynorphin peptides are not those with high affinity to opioid receptors, but are known to bind and activate also -and ⌬-opioid receptors. In addition, the peak intensities of a novel endogenous metabolite of ␣-neoendorphin lacking the N-terminal tyrosine correlated positively with dyskinesia severity. MALDI IMS of striatal sections from Pdyn knockout mice verified the identity of fully processed dynorphin peptides and the presence of endogenous des-tyrosine ␣-neoendorphin. Des-tyrosine dynorphins display reduced opioid receptor binding and this points to possible novel nonopioid receptor mediated changes in the striatum of dyskinetic rats. Because des-tyrosine dynorphins can only be detected by mass spectrometry, as no antibodies are available, these findings highlight the importance of MALDI IMS analysis for the study of molecular dynamics in neurological diseases. Molecular & Cellular

The Pharmacology of l-DOPA-Induced Dyskinesia in Parkinson’s Disease

“…However, the behavioral endpoint of that study was rotational L-DOPA-Induced Dyskinesia Pharmacology behavior and not AIMs, therefore precluding one to correlate AIMs with increased striatal levels of substance P. In contrast, a study that measured substance P levels in the striatum of 6-OHDA-lesioned rats killed at peak AIMs expression found no increase P levels when compared with control animals and no correlation between substance P levels and AIMs (Hanrieder et al, 2011). In PD patients treated with L-DOPA (dyskinetic phenotype not mentioned), substance P mRNA levels within the striatum were not different to those from control individuals (Levy et al, 1995b).…”

“…Although PPT and substance P appear to be decreased in parkinsonism and normalized after L-DOPA therapy, the design of the studies does not allow establishing correlations between PPT and dyskinesia, although the most convincing data, from a study by Hanrieder et al (2011), in which animals were killed at peak dyskinesia expression, suggest that LID is likely not associated with enhanced substance P levels.…”

Neuroproteomics tools in clinical practice

“…When irradiated with the laser, energy is transferred to the matrix and ionizes the analyte into the gas phase. Another recent approach MALDI-imaging mass spectrometry (IMS) is becoming a valuable tool in neuroproteomics to identify the distribution of neuropeptides and proteins directly in thin brain tissue sections [55][56][57].…”

Imaging Mass Spectrometry in Neuroscience

“…94,95 Here, IMS was employed to characterize spatial regulations of prodynorphin peptides in L-DOPA induced dyskinesia in experimental Parkinsons's disease. L-DOPA is the major pharmacotherapy for symptomatic Parkinsons's disease treatment but is accompanied by severe side effects, including abnormal involuntary movements, that is, dyskinesia.…”

“…Moreover, des-Tyr dynorphins were earlier reported to show NMDA receptor affinity pointing toward alternative opioid signaling mechanisms in LID. 94 In the area of PD research, MALDI Imaging has been successfully employed to image proteins. Here, IMS was used to elucidate striatal protein distributions in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injected rats 96 ( Figure 5a).…”