Alterations in prodynorphin, proenkephalin, and GAD67 mRNA levels in the aged human putamen: correlation with Parkinson's disease

The effect of acetic acid-induced pain in Parkinson's disease model in zebrafish

Parkinson's disease (PD) is the second most common neurodegenerative disease caused by the degeneration of dopaminergic neurons and the accumulation of Lewy bodies. Pain is one of the most common non-motor symptoms in PD, but the molecular mechanism of pain in PD is not fully understood, which prevents early diagnosis of PD. We aimed to determine the changes in opioidergic pathways when external pain is inflicted by inducing pain intraperitoneally in zebrafish, for which we generated a rotenone-induced PD model. After behavioural analyses in control(C), acetic acid (AA), rotenone (ROT), and rotenone+ acetic acid (ROT+AA) groups, catecholamine levels in brain tissue were determined by LC-MS/MS, expression of opioid peptides and their receptors by RT-PCR, expression of tyrosine hydroxylase by immunohistochemical method, and analyses of oxidant-antioxidant parameters by spectrophotometric methods. In the ROT group, distance travelled, average speed, and brain dopamine levels decreased, while LPO (lipid peroxidation) and NO (nitric oxide) increased as indicators of oxidative damage, and the SOD activity decreased. The mRNA expression of lrrk, pink1, and park7 genes associated with PD increased, while the mRNA expression of park2 decreased. This indicates that rotenone exposure is a suitable means to induce PD in zebrafish. The fact that body curvature was higher in the AA group than in the ROT and ROT+AA groups, as well as the decreased expression of penka, pdyn, and ion channels associated with the perception of peripheral pain in the ROT+AA group, suggest that mechanisms associated with pain are impaired in the rotenone-induced PD model in zebrafish.

Next-generation profiling to identify the molecular etiology of Parkinson dementia

OBJECTIVE

We sought to determine the underlying cortical gene expression changes associated with Parkinson dementia using a next-generation RNA sequencing approach.

METHODS

In this study, we used RNA sequencing to evaluate differential gene expression and alternative splicing in the posterior cingulate cortex from neurologically normal control patients, patients with Parkinson disease, and patients with Parkinson disease with dementia.

RESULTS

Genes overexpressed in both disease states were involved with an immune response, whereas shared underexpressed genes functioned in signal transduction or as components of the cytoskeleton. Alternative splicing analysis produced a pattern of immune and RNA-processing disturbances.

CONCLUSIONS

Genes with the greatest degree of differential expression did not overlap with genes exhibiting significant alternative splicing activity. Such variation indicates the importance of broadening expression studies to include exon-level changes because there can be significant differential splicing activity with potential structural consequences, a subtlety that is not detected when examining differential gene expression alone, or is underrepresented with probe-limited array technology.

Combined exposure to agriculture pesticides, paraquat and maneb, induces alterations in the N/OFQ-NOPr and PDYN/KOPr systems in rats: Relevance to sporadic Parkinson's disease

Despite several years of research, the aetiology of Parkinson's disease (PD) is quite far from being solved. In PD, as well as in other neurodegenerative disorders, it has been proposed that the combination of multiple factors might contribute to the onset of the disease. Indeed, several authors have suggested that environmental factors, such as pollutants and chemicals, might be associated with the onset of several neurodegenerative disorders. On the other hand, several studies have described that the nociceptin/orphanin-NOP and prodynorphin-KOP opioid systems are implicated in the pathology of Parkinson's disease. Considering the nonrestricted commercial availability and common use of several pesticides, such as paraquat and maneb, in agriculture of less developed countries, the aim of our study was to investigate the involvement of nociceptin/orphanin-NOP and prodynorphin-KOP systems in a chronic paraquat and maneb animal model of Parkinson's disease. Our results showed that after paraquat/maneb (5/15 mg kg(-1) ) treatment, a significant reduction in tyrosine hydroxylase (TH) levels, the rate-limiting enzyme for dopamine synthesis, was observed. Also, the association of paraquat and maneb (5/15 mg kg(-1) ) induced an increase in nociceptin/orphanin and a decrease of prodynorphin gene expression levels in the substantia nigra with a down-regulation of NOP and KOP receptors after both treatments in the substantia nigra and caudate putamen. These data further confirm that paraquat and maneb toxicity can modulate gene expression of the nociceptin/orphanin-NOP receptor and prodynorphin-KOP receptor systems in the substantia nigra and caudate putamen, offering further support to the hypothesis that chronic exposure to these agrochemicals might be implicated in the mechanisms underlying sporadic Parkinson's disease. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 656-663, 2015.

Decreased glutamic acid decarboxylase mRNA expression in prefrontal cortex in Parkinson's disease

Parkinson's disease (PD) patients typically suffer from motor disorders but mild to severe cognitive deficits can also be present. Neuropathology of PD primarily involves loss of dopaminergic neurons in the substantia nigra, pars compacta, although more widespread pathology from the brainstem to the cerebral cortex occurs at different stages of the disease. Cognitive deficits in PD are thought to involve the cerebral cortex, and imaging studies have identified the dorsolateral prefrontal cortex (DLPFC) as a possible site for some of the symptoms. GABAergic neurons in the cerebral cortex play a key role in the modulation of pyramidal neurons and alterations in muscimol binding to GABA(A) receptors have been reported in Brodmann area 9 (BA9) of the prefrontal cortex in PD patients (Nishino et al., 1988). In order to further assess the likelihood that GABAergic activity is altered in the prefrontal cortex in PD, gene expression of the 67 kilodalton isoform of the GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD67 encoded by the GAD1 gene), was examined in BA9 of post-mortem brains from 19 patients and 20 controls using isotopic in situ hybridization histochemistry. GAD67 mRNA labeling was examined and quantified on X-ray films and emulsion radioautographs. We show that GAD67 mRNA labeling is significantly lower in PD compared to control cases. Analysis of emulsion radioautographs indicates that GAD67 mRNA labeling is decreased in individual neurons and is not paralleled by a decrease in the number of GAD67 mRNA-labeled neurons. Analysis of expression data from a microarray study performed in 29 control and 33 PD samples from BA9 confirms that GAD67 expression is decreased in PD. Another finding from the microarray study is a negative relationship between GAD67 mRNA expression and age at death. Altogether, the results support the possibility that GABAergic neurotransmission is impaired in the DLPFC in PD, an effect that may be involved in some of the behavioral deficits associated with the disease.

Decreased glutamic acid decarboxylase(67) mRNA expression in multiple brain areas of patients with schizophrenia and mood disorders

Reduced levels of glutamic acid decarboxylase(67) (GAD(67)), an essential enzyme for GABA synthesis, is one of the most consistent gene expression changes found in the frontal cortex of patients with schizophrenia. Recently this reduction has been shown to extend to other areas including primary sensory, primary motor and anterior cingulate (ACC) cortices. To determine the extent to which additional cortical and subcortical regions may be affected in schizophrenia, we measured the level of GAD(67) mRNA in previously unexplored areas including the orbitofrontal (OFC) and superior temporal (STG) cortices as well as the caudate, putamen, nucleus accumbens, medial dorsal thalamus and anterior thalamus using in situ hybridization. We also examined GAD(67) mRNA levels in all these regions in individuals with bipolar disorder and major depression. ANCOVA comparing GAD(67) mRNA levels in all four diagnostic groups revealed a significant reduction (approximately 30%) in layers III and IV of the OFC of patients with schizophrenia and bipolar disorder. A priori t-tests comparing GAD(67) mRNA levels between the schizophrenia and control groups revealed significant reductions in the ACC, STG, striatum and thalamus. These findings suggest that there may be a widespread reduction in GABA neurotransmission due to a decrease in the synthesis of GAD(67) in subjects with psychiatric disorders. The resulting decrease in inhibitory tone across multiple brain areas may contribute to the psychotic behavior observed in patients with schizophrenia and bipolar disorder.

Effects of prodynorphin deletion on striatal dopamine in mice during normal aging and in response to MPTP

Dynorphins, endogenous neuropeptides found in striatonigral neurons, have been observed to exhibit dopamine-inhibitory actions and under some circumstances possess intrinsic neurotoxic activity. To test the hypothesis that dynorphin suppression mitigates effects of aging on the striatal dopaminergic system, HPLC quantitation of dopamine and related amines was performed on striatal homogenates of wild-type (WT) mice and mice lacking the prodynorphin (Pdyn) gene at varying ages. Pdyn knockout (KO) mice at 10 and 20 months show significant elevations in striatal dopamine compared to 3-month mice. Differences in tyrosine hydroxylase (TH) immunoreactivity could not account for these findings, but phosphorylation of TH at Ser40, but not Ser31, was enhanced in aged Pdyn KO mice. Systemic administration of MPTP produced significant dopamine depletion in an age-dependent manner, but Pdyn deletion conferred no protection against MPTP-induced dopamine loss, arguing against a mechanism by which Pdyn deletion enhances dopaminergic neuron survival. The above findings demonstrate an age-dependent inhibitory effect of dynorphins on striatal dopamine synthesis via modulation of TH activity.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

alpha-Synuclein pathology in the neostriatum in Parkinson's disease

We immunohistochemically examined the neostriatum from 25 patients with symptomatic and presymptomatic Parkinson's disease (PD) with various degrees of Lewy body pathology, using anti-phosphorylated alpha-synuclein (alphaS) antibody. These patients were classified according to the PD staging proposed by Braak et al. (Neurobiol Aging 24:197-211, 2003): stage II (alphaS pathology confined to the medulla oblongata and pontine tegmentum), stage III (alphaS pathology confined to the brainstem), stage IV (limbic stage), and stages V and VI (neocortical stage). alphaS immunohistochemistry revealed neuronal and glial cytoplasmic inclusions and neuritic changes in the neostriatum. alphaS inclusions were found in the medium-sized neurons (GABAergic neurons that project to the globus pallidus) and large neurons (cholinergic interneurons); the former began to appear at stage III and the latter was noted at stages V and VI. Neuritic changes and glial inclusions also began to appear at stage III. The numbers of neuronal and glial inclusions, and the extent of neuritic changes, correlated with the PD stage (P < 0.001). These findings suggest that intrinsic neostriatal neurons degenerate through alphaS aggregation during PD progression.

Motor deficits and altered striatal gene expression in aphakia (ak) mice

Like humans with Parkinson's disease (PD), the ak mouse lacks the majority of the substantia nigra pars compacta (SNc) and experiences striatal denervation. The purpose of this study was to test whether motor abnormalities in the ak mouse progress over time, and whether motor function could be associated with temporal alterations in the striatal transcriptome. Ak and wt mice (28 to 180 days old) were tested using paradigms sensitive to nigrostriatal dysfunction. Results were analyzed using a linear mixed model. Ak mice significantly underperformed wt controls in rotarod, balance beam, string test, pole test and cotton shred tests at all ages examined. Motor performance in ak mice remained constant over the first 6 months of life, with the exception of the cotton shred test, in which ak mice exhibited marginal decline in performance. Dorsal striatal semi-quantitative RT-PCR for 19 dopaminergic, cholinergic, glutaminergic and catabolic genes was performed in 1- and 6-month-old groups of ak and wt mice. Preproenkephalin levels in ak mice were elevated in both age groups. Drd1, 3 and 4 levels declined over time, in contrast to increasing Drd2 expression. Additional findings included decreased Chrnalpha6 expression and elevated VGluT1 expression at both time points in ak mice and elevated AchE expression in young ak mice only. Results confirm that motor ability does not decline significantly for the first 6 months of life in ak mice. Their striatal gene expression patterns are consistent with dopaminergic denervation, and change over time, despite relatively unaltered motor performance.