Lysosomal hydrolases in cerebrospinal fluid from subjects with Parkinson's disease.

Recent studies have shown a genetic association between glucocerebrosidase deficiencies and Parkinson's disease (PD). To further explore this issue the activity of beta-glucocerebrosidase and the activities of other lysosomal enzymes, alpha-mannosidase, beta-mannosidase, beta-hexosaminidase, and beta-galactosidase have been evaluated in the cerebrospinal fluid (CSF) of PD patients. The activities of alpha-mannosidase, beta-mannosidase, beta-glucocerebrosidase, and beta-hexosaminidase were substantially decreased in the CSF of PD patients, while levels of beta-galactosidase were essentially identical to controls. This study indicates that in PD several lysosomal hydrolases have decreased activities, further supporting a possible link between pathophysiological mechanisms underlying PD and lysosomal hydrolases.     

Aggresome-related biogenesis of Lewy bodies

Neurodegenerative disorders such as Parkinson's disease (PD) and 'dementia with Lewy bodies' (DLB) are characterized pathologically by selective neuronal death and the appearance of intracytoplasmic protein aggregates (Lewy bodies). The process by which these inclusions are formed and their role in the neurodegenerative process remain elusive. In this study, we demonstrate a close relationship between Lewy bodies and aggresomes, which are cytoplasmic inclusions formed at the centrosome as a cytoprotective response to sequester and degrade excess levels of potentially toxic abnormal proteins within cells. We show that the centrosome/aggresome-related proteins gamma-tubulin and pericentrin display an aggresome-like distribution in Lewy bodies in PD and DLB. Lewy bodies also sequester the ubiquitin-activating enzyme (E1), the proteasome activators PA700 and PA28, and HSP70, all of which are recruited to aggresomes for enhanced proteolysis. Using novel antibodies that are specific and highly sensitive to ubiquitin-protein conjugates, we revealed the presence of numerous discrete ubiquitinated protein aggregates in neuronal soma and processes in PD and DLB. These aggregates appear to be being transported from peripheral sites to the centrosome where they are sequestered to form Lewy bodies in neurons. Finally, we have shown that inhibition of proteasomal function or generation of misfolded proteins cause the formation of aggresome/Lewy body-like inclusions and cytotoxicity in dopaminergic neurons in culture. These observations suggest that Lewy body formation may be an aggresome-related event in response to increasing levels of abnormal proteins in neurons. This phenomenon is consistent with growing evidence that altered protein handling underlies the etiopathogenesis of PD and related disorders.     

Milestones in clinical neurophysiology

Over the last 25 years, clinical neurophysiology has made many advances in the understanding, diagnosis, and even treatment of different movement disorders. Transcranial magnetic stimulation has been the biggest technical advance. Progress in pathophysiology includes improved knowledge about bradykinesia in Parkinson's disease, loss of inhibition and increased plasticity in dystonia, abnormal startle in hyperekplexia, and various features of psychogenic movement disorders that can aid diagnosis. Studies have been done looking at the use of noninvasive brain stimulation for therapy, but effects are generally small. © 2011 Movement Disorder Society     

In utero bacterial endotoxin exposure causes loss of tyrosine hydroxylase neurons in the postnatal rat midbrain.

We investigated whether in utero exposure to the Gram(-) bacteriotoxin lipopolysaccharide (LPS) induces dopamine (DA) neuron loss in rats. The proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) kills DA neurons and is elevated in the brains of patients with Parkinson's disease (PD). LPS is a potent inducer of TNF-alpha, and both are increased in the chorioamniotic environment of women who have bacterial vaginosis (BV) during pregnancy, suggesting that BV might interfere with the normal development of fetal DA neurons. Gravid female rats were injected intraperitoneally with either LPS or normal saline at embryonic day 10.5 and their pups were killed at postnatal day 21. The brains of the pups were assessed for DA and TNF-alpha levels and DA cell counts in the mesencephalon using tyrosine hydroxylase immunoreactive (THir) cells as a DA neuron marker. Prenatal LPS exposure significantly reduced striatal DA (29%) and increased DA activity (72%) as well as TNF-alpha (101%). Stereological cell counts in the mesencephalon were also significantly reduced (27%) by prenatal LPS exposure. Prenatal exposure to LPS, as might occur in humans with BV, produces a significant loss of THir cells in rats that is still present 33 days following a single injection of LPS. Since this cell loss is well past the normal phase of DA neuron apoptosis that occurs in early postnatal life, rats so exposed may have a permanent loss of DA neurons, suggesting that prenatal infections may represent risk factors for PD.     

Transcranial Magnetic Stimulation in Neurology: What We Have Learned From Randomized Controlled Studies

Background. Initially developed to excite peripheral nerves, magnetic stimulation was quickly recognized as a valuable tool to noninvasively activate the cerebral cortex. The subsequent discovery that repetitive transcranial magnetic stimulation (rTMS) could have long‐lasting effects on cortical excitability spawned a broad interest in the use of this technique as a new therapeutic method in a variety of neuropsychiatric disorders. Although the current outcomes from initial trials include some conflicting results, initial evidence supports that rTMS might have a therapeutic value in different neurologic conditions. Methods. We reviewed the results of clinical trials of rTMS on four different disorders: stroke, Parkinson's disease, chronic refractory pain, and epilepsy. We reviewed randomized, controlled studies only in order to obtain the strongest evidence for the clinical effects of rTMS. Results. An extensive literature review revealed 32 articles that met our criteria. From these studies, we found evidence for the therapeutic efficacy of rTMS, particularly in the relief of chronic pain and motor neurorehabilitation in single hemisphere stroke patients. Repetitive TMS also seems to have a therapeutic effect on motor function in Parkinson's disease, but the evidence is somewhat confounded by the uncontrolled variability of multiple factors. Lastly, only two randomized, sham‐controlled studies have been performed for epilepsy; although evidence indicates rTMS may reduce seizure frequency in patients with neocortical foci, more research is needed to confirm these initial findings. Conclusions. There is mounting evidence for the efficacy of rTMS in the short‐term treatment of certain neurologic conditions. More long‐term research is needed in order to properly evaluate the effects of this method in a clinical setting.     

Exercise-induced dystonia as a preceding symptom of familial Parkinson's disease.

Paroxysmal exercise-induced dystonia can occur with Parkinson's disease (PD), and in rare cases, this can also be the presenting symptom. We report on 2 second cousins (no known consanguinity) who presented with paroxysmal exercise-induced dystonia who later developed clinical features of PD. Although autosomal recessive inheritance was suggested, and the dystonic features further suggest parkin as a possible cause, sequencing for parkin mutations was negative and this family may represent a genetic variant of PD. Further genotype-phenotype studies in this and similar families may give clues to pre-symptomatic symptoms in PD and may reflect a particular phenotype of interest for genetics studies in the future.     

Presenilin 1 is involved in the maturation of beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1)

One of the pathologic hallmarks of Alzheimer's disease is the excessive deposition of beta-amyloid peptides (Abeta) in senile plaques. Abeta is generated when beta-amyloid precursor protein (APP) is cleaved sequentially by beta-secretase, identified as beta-site APP-cleaving enzyme 1 (BACE1), and gamma-secretase, a putative enzymatic complex containing presenilin 1 (PS1). However, functional interaction between PS1 and BACE1 has never been known. In addition to this classical role in the generation of Abeta peptides, it has also been proposed that PS1 affects the intracellular trafficking and maturation of selected membrane proteins. We show that the levels of exogenous and endogenous mature BACE1 expressed in presenilin-deficient mouse embryonic fibroblasts (PS-/-MEFs) were reduced significantly compared to those in wild-type MEFs. Moreover, the levels of mature BACE1 were increased in human neuroblastoma cell line, SH-SY5Y, stably expressing wild-type PS1, compared to native cells. Conversely, the maturation of BACE1 was compromised under the stable expression of dominant-negative mutant PS1 overexpression. Immunoprecipitation assay showed that PS1 preferably interacts with proBACE1 rather than mature BACE1, indicating that PS1 can be directly involved in the maturation process of BACE1. Further, endogenous PS1 was immunoprecipitated with endogenous BACE1 in SH-SY5Y cells and mouse brain tissue. We conclude that PS1 is directly involved in the maturation of BACE1, thus possibly functioning as a regulator of both beta- and gamma-secretase in Abeta generation.     

MEP latency shift after implantation of deep brain stimulation systems in the subthalamic nucleus in patients with advanced Parkinson's disease.

Deep brain stimulation (DBS) into the subthalamic nucleus (STN) is a highly effective treatment for advanced Parkinson's disease (PD). The consequences of STN stimulation on intracortical and corticospinal excitability have been addressed in a few studies using transcranial magnetic stimulation (TMS). Although excitability measurements were compared between the STN stimulation OFF and ON condition, in these experiments, there are no longitudinal studies examining the impact of electrode implantation per se on motor excitability. Here, we explored the effects of STN electrode implantation on resting motor thresholds (RMT), motor evoked potential (MEP) recruitment curves, and MEP onset latencies on 2 consecutive days before and shortly after STN surgery with the stimulator switched off, thus avoiding the effects of chronic DBS on the motor system, in 8 PD patients not taking any dopaminergic medication. After surgery, RMT and MEP recruitment curves were unchanged. In contrast, MEP onset latencies were significantly shorter when examined in relaxed muscles but were unchanged under preactivation. We hypothesize that postoperatively TMS pulses induced small currents in scalp leads underneath the TMS coil connecting the external stimulator with STN electrodes leading to inadvertent stimulation of fast-conducting descending neural elements in the vicinity of the STN, thereby producing submotor threshold descending volleys. These "conditioning" volleys probably preactivated spinal motor neurons leading to earlier suprathreshold activation by the multiple corticospinal volleys produced by TMS of the motor cortex. These TMS effects need to be considered when interpreting results of excitability measurements in PD patients after implantation of STN electrodes.     

Microglial phagocytosis is enhanced by monomeric alpha-synuclein, not aggregated alpha-synuclein: implications for Parkinson's disease

Gathering evidence has associated activation of microglia with the pathogenesis of numerous neurodegenerative diseases of the central nervous system (CNS) such as Alzheimer's disease and Parkinson's disease. Microglia are the resident macrophages of the CNS whose functions include chemotaxis, phagocytosis, and secretion of a variety of cytokines and proteases. In this study, we examined the possibility that alpha-synuclein (alpha-syn), which is associated with the pathogenesis of Parkinson's disease, may affect the phagocytic function of microglia. We found that extracellular monomeric alpha-syn enhanced microglial phagocytosis in both a dose- and time-dependent manner, but beta- and gamma- syn did not. We also found that the N-terminal and NAC region of alpha-syn, especially the NAC region, might be responsible for the effect of alpha-syn on microglial phagocytosis. In contrast to monomeric alpha-syn, aggregated alpha-syn actually inhibited microglial phagocytosis. The different effects of monomeric and aggregated alpha-syn on phagocytosis might be related to their localization in cells. This study indicates that alpha-syn can modulate the function of microglia and influence inflammatory changes such as those seen in neurodegenerative disorders.     

Myoclonus-dystonia syndrome with severe depression is caused by an exon-skipping mutation in the epsilon-sarcoglycan gene.

We describe two affected individuals in a family with myoclonus-dystonia syndrome complicated with severe depression. One individual committed suicide. Molecular genetic analysis revealed a heterozygous point mutation in the epsilon-sarcoglycan gene, which we show leads to skipping of exon 5. This report suggests that the psychiatric spectrum of MDS includes more severe depression.     

Effect of age on the duration and extent of amyloid plaque reduction and microglial activation after injection of anti-Abeta antibody into the third ventricle of TgCRND8 mice

We have previously shown that anti beta-amyloid (Abeta) antibody injected into the third ventricle of mice is distributed throughout the brain within 24 hr and is completely washed out of brain within 36 hr after injection and that, in Tg2576 animals, a single injection of antibody reduces cerebral Abeta and restores presynaptic deficits 1 month after injection without producing hemorrhage or inflammation at an early plaque stage. Here we report the effects of a single ICV injection of anti-Abeta antibody on cerebral levels of immunoreactive Abeta and of microglial activation measured by immunoreactive interleukin-1beta (IL-1beta) at 1, 4, and 8 weeks after injections in TgCRND8 mice at two ages, 2 months (sparse plaques) and 8 months (abundant plaques). The data show that parenchymal amyloid accumulates before cerebral microvascular amyloid and that a single ICV injection reduces only parenchymal amyloid by about 70%, without affecting vascular amyloid, and reduces microglial activation by 46-60% at 1 week after injection. The reappearance of plaques after antibody injection takes 4-8 weeks, whereas plaque-associated focal microglial activation begins increasing between 1 and 4 weeks, suggesting that accumulation of nonfibrillar oligomeric Abeta may account for the earlier onset of microglial activation. No perivascular hemorrhage or inflammation was observed. These results suggest that periodic intraventricular administration of anti-Abeta is a potentially useful method for rapid reduction of both preexisting amyloid load and associated inflammation, providing a window of 4 weeks' duration for possible pharmacological cotreatment(s) to prevent de novo Abeta formation. This ICV method of passive immunization may be safer than active immunization, which has been known to produce encephalitis, or systemic passive immunization, which exposes amyloid-laden cerebral microvasculature to high levels of antibody in the blood and the potential of perivascular hemorrhages.     

TorsinA accumulation in Lewy bodies in sporadic Parkinson's disease

Parkinson's disease (PD) is a neurodegnerative disorder that is pathologically characterized by the presence of Lewy bodies in the brain. We show that Lewy bodies in PD are strongly immunoreactive for torsinA, the protein product of the DYT1 gene, which is associated with primary generalized dystonia. In the substantia nigra, torsinA immunoreactivity is localized to the periphery of Lewy bodies, whereas, in cortical Lewy bodies it is uniformly distributed. The significance of this finding is unknown, but may implicate torsinA in neuronal dysfunction that occurs in PD as well as in primary dystonia.     

Advanced glycation end products induce in vitro cross-linking of alpha-synuclein and accelerate the process of intracellular inclusion body formation

Cross-linking of alpha-synuclein and Lewy body formation have been implicated in the dopaminergic neuronal cell death observed in Parkinson's disease (PD); the mechanisms responsible, however, are not clear. Reactive oxygen species and advanced glycation end products (AGEs) have been found in the intracellular, alpha-synuclein-positive Lewy bodies in the brains of both PD as well as incidental Lewy body disease patients, suggesting a role for AGEs in alpha-synuclein cross-linking and Lewy body formation. The aims of the present study were to determine 1) whether AGEs can induce cross-linking of alpha-synuclein peptides, 2) the progressive and time-dependent intracellular accumulation of AGEs and inclusion body formation, and 3) the effects of extracellular or exogenous AGEs on intracellular inclusion formation. We first investigated the time-dependent cross-linking of recombinant human alpha-synuclein in the presence of AGEs in vitro, then used a cell culture model based on chronic rotenone treatment of human dopaminergic neuroblastoma cells (SH-SY5Y) over a period of 1-4 weeks, in the presence of different doses of AGEs. Cells (grown on coverslips) and cell lysates, collected at the end of every week, were analyzed for the presence of intracellular reactive oxygen species, AGEs, alpha-synuclein proteins, and intracellular alpha-synuclein- and AGE-positive inclusion bodies by using immunocytochemical, biochemical, and Western blot techniques. Our results show that AGEs promote in vitro cross-linking of alpha-synuclein, that intracellular accumulation of AGEs precedes alpha-synuclein-positive inclusion body formation, and that extracellular AGEs accelerate the process of intracellular alpha-synuclein-positive inclusion body formation.     

1-Benzyl-1,2,3,4-tetrahydroisoquinoline, a Parkinsonism-inducing endogenous toxin, increases alpha-synuclein expression and causes nuclear damage in human dopaminergic cells

1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ), an endogenous neurotoxin, is known to cause parkinsonism in rodents and nonhuman primates. The levels of 1BnTIQ in cerebrospinal fluid of patients with Parkinson's disease (PD) were reported to be three times higher than those in control subjects. In the present study, we have evaluated the effects of 1BnTIQ on alpha-synuclein (alpha-syn) expression together with biochemical and morphological changes in human dopaminergic SH-SY5Y cells in culture. 1BnTIQ at lower concentrations (1-50 microM) increased alpha-syn protein expression in a time- and dose-dependent manner in these cells. There was also up-regulation of alpha-syn mRNA by 1BnTIQ. Inhibition of complex I by rotenone and depletion of glutathione by L-buthionine sulfoxamine also correlated with an increase in alpha-syn expression, suggesting that oxidative stress may cause an increase in alpha-syn levels in dopaminergic cells. Furthermore, 1BnTIQ significantly depleted glutathione levels. 1BnTIQ at higher concentrations (500 microM) increased reactive oxygen species levels, decreased ATP levels, and caused nuclear damage in the cells. The 1BnTIQ-induced alpha-syn up-regulation was inhibited by cotreatment with the antioxidants selegiline, coenzyme Q(10), and N-acetylcystein and the caspase inhibitor DEVD-CHO. Taken together, these results suggest that alpha-syn up-regulation and oxidative stress are contributing factors in 1BnTIQ-induced neurotoxicity in dopaminergic neurons in PD.     

Genetics of parkinsonism.

Parkinson's disease (PD) was noted to have a familial component as early as 1880 (Leroux, 1880). More recently, the discovery of several genetic factors influencing parkinsonism has emphasized the importance of heredity in PD. The clinical spectrum of familial parkinsonism is wide; it includes not only PD, but also dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), essential tremor, and other disorders. In the general population, it is likely that PD results from combined genetic and environmental factors, most of which are not yet known. The discovery of causal mutations in the gene for alpha-synuclein, parkin, and of genetic linkages to chromosomes 2p4, 4p5, and three loci on 1q6-8 have revolutionized PD research. This review focuses on recent progress in the Mendelian genetics of PD and those diseases in which parkinsonism is a prominent feature, and considers how these discoveries modify our beliefs regarding the etiology and pathogenesis of these disorders.     

Cortical versus spinal dysfunction in amyotrophic lateral sclerosis

Little is known about the possible link between cortical and spinal motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). We correlated the characteristics of the responses to transcranial magnetic stimulation (TMS) with the electromechanical properties and firing pattern of single motor units (MUs) tested in nine ALS patients, three patients with Kennedy's disease, and 15 healthy subjects. In Kennedy's disease, 19 of 22 MUs were markedly enlarged with good electromechanical coupling and discharged with great variability. Their excitatory responses increased with MU size. In ALS, 17 of 34 MUs with excitatory responses behaved as in Kennedy's disease. By contrast, 28 MUs with nonsignificant responses showed poor electromechanical coupling and high firing rates, whereas 28 MUs with inhibitory responses showed moderate functional alterations. This result indicates that in ALS as in Kennedy's disease, sprouting of corticospinal axons may occur on surviving motoneurons. A clear relationship exists between the responsiveness of MUs to TMS and their functional state.