Cholinergic imaging in corticobasal syndrome, progressive supranuclear palsy and frontotemporal dementia.

Corticobasal syndrome, progressive supranuclear palsy and frontotemporal dementia are all part of a disease spectrum that includes common cognitive impairment and movement disorders. The aim of this study was to characterize brain cholinergic deficits in these disorders. We measured brain acetylcholinesterase activity by [11C] N-methylpiperidin-4-yl acetate and positron emission tomography in seven patients with corticobasal syndrome (67.6+/-5.9 years), 12 with progressive supranuclear palsy (68.5+/-4.1 years), eight with frontotemporal dementia (59.8+/-6.9 years) and 16 healthy controls (61.2+/-8.5 years). Two-tissue compartment three-parameter model and non-linear least squares analysis with arterial input function were performed. k3 value, an index of acetylcholinesterase activity, was calculated voxel-by-voxel in the brain of each subject. The k3 images in each disease group were compared with the control group by using Statistical Parametric Mapping 2. Volume of interest analysis was performed on spatially normalized k3 images. The corticobasal syndrome group showed decreased acetylcholinesterase activity (k3 values) in the paracentral region, frontal, parietal and occipital cortices (P<0.05, cluster corrected). The group with progressive supranuclear palsy had reduced acetylcholinesterase activity in the paracentral region and thalamus (P<0.05, cluster corrected). The frontotemporal dementia group showed no significant differences in acetylcholinesterase activity. Volume of interest analysis showed mean cortical acetylcholinesterase activity to be reduced by 17.5% in corticobasal syndrome (P<0.001), 9.4% in progressive supranuclear palsy (P<0.05) and 4.4% in frontotemporal dementia (non-significant), when compared with the control group. Thalamic acetylcholinesterase activity was reduced by 6.4% in corticobasal syndrome (non-significant), 24.0% in progressive supranuclear palsy (P<0.03) and increased by 3.3% in frontotemporal dementia (non-significant). Both corticobasal syndrome and progressive supranuclear palsy showed brain cholinergic deficits, but their distribution differed somewhat. Significant brain cholinergic deficits were not seen in frontotemporal dementia, which may explain the unresponsiveness of this condition to cholinergic modulation therapy.

Identification of G-protein coupled receptor kinase 2 in paired helical filaments and neurofibrillary tangles.

G-protein coupled receptor kinases (GRKs) constitute a serine/threonine kinase family playing a major role in agonist-induced phosphorylation and desensitization of G-protein coupled receptors. Recently, GRK2 and GRK5 have been demonstrated to phosphorylate alpha-synuclein (Ser129) and other synuclein isoforms. We studied colocalization of GRK2, GRK5, alpha-synuclein, and tau in neurodegenerative disorders characterized by fibrillary tau inclusions and/or alpha-synuclein-enriched Lewy bodies. We found that Lewy bodies were negative for both GRK2 and GRK5 in Lewy body disease (LBD) and LBD mixed with Alzheimer disease (AD + LBD). Instead, GRK2 but not GRK5 colocalized with 40% to 50% of neurofibrillary tangles in AD + LBD and AD brains. In disorders with less prominent alpha-synucleinopathy, neuronal and glial fibrillary tau deposits known to contain distinct subsets of tau isoforms were also positive for GRK2. These deposits included tufted astrocytes and coiled bodies in progressive supranuclear palsy, astrocytic plaques in corticobasal degeneration, and Pick bodies in Pick disease. In addition, paired helical filaments isolated from AD and AD + LBD brains were found to immunogold-label for GRK2, suggesting that GRK2 could be a potential tau kinase associated with fibrillary tau. Our studies indicate that GRK2 is a novel component of neuronal and glial fibrillary tau deposits with no preference in tau isoform binding. GRK2 may play a role in hyperphosphorylation of tau in tauopathies.

Expression of 8-oxoguanine DNA glycosylase (OGG1) in Parkinson's disease and related neurodegenerative disorders.

Oxidative stress including DNA oxidation is implicated in Parkinson's disease (PD). We postulated that DNA repair enzymes such as 8-oxoguanosine DNA glycosylase (OGG1) are involved in the PD process. We performed immunohistochemical and biochemical studies on brains of patients with PD and those of patients with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) as disease controls, and control subjects. We found higher expression levels of mitochondrial isoforms of OGG1 enzymes in the substantia nigra (SN) in cases of PD. Furthermore, Western blot analysis revealed high OGG1 levels in the SN of the patients with PD. Our results indicate the importance of oxidative stress within the susceptible lesions in the pathogenesis of PD.

Protein levels of glycogen synthase 3 kinase are normal in progressive supranuclear palsy.

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by pure neurofibrillary tau pathology involving mainly basal ganglia and brain stem nuclei. One of the kinases involved in tau phosphorylation is glycogen synthase 3 kinase (GSK3). In mammals GSK3 is present in two isoforms, alpha and beta regulated by phosphorylation: phosphorylation of Ser9 in GSK3beta or Ser21 in GSK3alpha leads to inactivation while phosphorylation of Tyr216 in GSK3beta or Tyr279 in GSK3alpha leads to activation. We analyzed the protein levels of GSK3alpha/beta and of the phosphorylated forms GSK3beta S(9), GSK3beta Y(216), GSK3alpha Y(279) in brain tissues of subjects with PSP. The analysis failed to show significant differences of all GSK3 isoforms in PSP in comparison to age-matched control cases. This negative result argues against the role of GSK3 in the pathogenesis of PSP.

Elevated levels of matrix metalloproteinases-9 and -1 and of tissue inhibitors of MMPs, TIMP-1 and TIMP-2 in postmortem brain tissue of progressive supranuclear palsy.

We determined the levels and tissue localization of matrix metalloproteinases (MMPs) as well as their endogenous tissue inhibitors (TIMPs) in postmortem brain tissue from 13 patients with progressive supranuclear palsy (PSP) and 8 age-matched controls. MMP-9 expression was significantly increased in both the frontal cortex (p = 0.002) and substantia nigra (p = 0.003) of PSP cases as compared to controls whereas MMP-1 levels were increased in the substantia nigra (p = 0.01) but unchanged in the frontal cortex (p = 0.41). Levels of the endogenous tissue inhibitors of MMPs, TIMP-1 and TIMP-2 were significantly elevated in the substantia nigra (TIMP-1: p = 0.004, TIMP-2: p = 0.01). Levels of TIMPs were unchanged in PSP frontal cortex as compared to control cases. Together, these data show alterations of MMPs and TIMPs in the substantia nigra as well as in the frontal cortex of PSP, consistent with the possibility that alterations in MMPs/TIMPs may contribute to disease pathogenesis.

Mutational study of the nuclear factor kappa B inducing kinase gene in patients with progressive supranuclear palsy.

The nuclear factor kappa B inducing kinase gene (NIK) is located near the region of the haplotype associated with progressive supranuclear palsy (PSP) in chromosome 17q. We have analysed the coding region of the NIK gene in PSP patients through single strand conformation polymorphism and direct sequencing, in order to investigate the possible existence of pathogenic mutations. A change in exon 15 consisting of a G/C variation in position 2839 was found. This change was then analysed through restriction endonuclease HphI in 40 PSP samples and 35 control samples, but no differences in allelic frequency were found between the PSP and control groups. Our results do not support a pathogenic role of the NIK gene in PSP.

Transglutaminase activity, protein, and mRNA expression are increased in progressive supranuclear palsy.

Transglutaminases catalyze the covalent cross-linking of substrate proteins to form insoluble protein complexes that are resistant to degradation. Our previous studies demonstrated that transglutaminase-induced cross-linking of tau proteins occurs in Alzheimer disease and progressive supranuclear palsy (PSP). The current study was designed to measure transglutaminase enzyme activity and the mRNA and protein levels of 3 transglutaminase isoforms that are expressed in human brain. Overall, transglutaminase activity was significantly increased in the globus pallidus (182% of control) and pons in PSP (171% of control) but not the occipital cortex (a region spared from pathology). Using a Spearman rank correlation test, we found that tissues with more transglutaminase-activity had more neurofibrillary tangles. Protein and mRNA levels of transglutaminase 1 were increased in globus pallidus of PSP as compared to controls. There were also significantly higher mRNA levels of the short form of transglutaminase 2 in globus pallidus of PSP (974% of control). Transglutaminase 1 mRNA and the long isoform of transglutaminase 2 mRNA (2212% of control) were significantly higher in PSP in the dentate of cerebellum. Together, these findings suggest that transglutaminase 1 and 2 enzymes may be involved in the formation and/or stabilization of neurofibrillary tangles in selectively vulnerable brain regions in PSP. These transglutaminases may be potential targets for therapeutic intervention.

Brain proteasomal function in sporadic Parkinson's disease and related disorders.

Because genetic defects relating to the ubiquitin-proteasome system were reported in familial parkinsonism, we evaluated proteasomal function in autopsied brains with sporadic Parkinson's disease. We found that proteasome peptidase activities in a fraction specific to the proteasome were preserved in five brain areas (including the striatum) of Parkinson's disease where neuronal loss is not observed. Striatal protein levels of two proteasome subunits were normal in Parkinson's disease but reduced mildly in disease controls (multiple system atrophy). Our brain data suggest that a systemic, global disturbance in the catalytic activity and degradation ability of the proteasome itself is unlikely to explain the cause of Parkinson's disease.

Brain aconitase activity is not decreased in progressive supranuclear palsy.

The novel finding of decreased activity of aconitase, a key Krebs cycle enzyme highly sensitive to oxidative damage, in cybrid cell lines using mitochondrial DNA from patients with progressive supranuclear palsy (PSP) implies an enzyme abnormality in brain. However, the authors found that postmortem brain aconitase activity is normal in PSP. This suggests that patients with PSP do not have systemic aconitase deficiency and that data derived from cybrid cell models of neurodegenerative disorders might not always predict similar changes in human brain.

Increase of cdk5 is related to neurofibrillary pathology in progressive supranuclear palsy.

BACKGROUND: Progressive supranuclear palsy (PSP) is characterized by a pure neurofibrillary tau pathology involving mainly basal ganglia and brainstem nuclei. In addition to a haplotype of the tau gene potentially favoring tau aggregation, lipoperoxidation has been shown to be associated with PSP tau pathology. OBJECTIVE: To analyze cdk5/p35 complex, a kinase that regulates neurite outgrowth, as a potential cellular mechanism underlying tau phosphorylation in brain tissues from PSP and control cases and comparatively in cerebral cortex from subjects with AD. METHODS: Cdk5/p35 protein levels and distribution were evaluated by immunoblotting and immunocytochemistry in brain regions from seven PSP, six AD, and seven control cases, with similar postmortem intervals. RESULTS: Total cdk5 protein levels were significantly increased by more than threefold in PSP tissue and were augmented in PSP neurons, codistributed with tau immunoreactivity. P35, the regulatory subunit of cdk5, was degraded by postmortem proteolysis to the same extent in PSP, AD, and control tissues. CONCLUSIONS: The proteolysis in vivo of p35, the regulatory subunit of the kinase, is not ascertainable because it is masked by its postmortem degradation. The study, however, indicates that in PSP, the alteration of cdk5 is different from that described in AD and suggests that the absence of amyloid beta protein deposition may account for the different pathways responsible for the same kinase activation.

Mitochondrial impairment in the cerebellum of the patients with progressive supranuclear palsy.

Abnormalities in energy metabolism and oxidative stress accompany many neurodegenerative diseases, including progressive supranuclear palsy (PSP). Previously, we showed decreased activities of a mitochondrial enzyme complex, alpha-ketoglutarate dehydrogenase complex (KGDHC), and marked increases in tissue malondialdehyde levels in post-mortem superior frontal cortex from the patients with PSP. The current study demonstrates that KGDHC is also significantly diminished (-58%) in the cerebellum from patients with PSP (n = 14), compared to age-matched control brains (n = 13). In contrast to cortex, markers of oxidative stress, such as malondialdehyde, tyrosine nitration or general protein carbonyl modification, did not increase in cerebellum. Furthermore, the protein levels of the individual components of KGDHC did not decline. The activities of two other mitochondrial enzymes were measured to determine whether the changes in KGDHC were selective. The activity of aconitase, a mitochondrial enzyme with an iron/sulfur cluster, is also significantly diminished (-50%), whereas glutamate dehydrogenase activity is unchanged. The present results suggest that the interaction of metabolic impairment and oxidative stress is region-specific in PSP brain. In cerebellum, reductions in KGDHC occur in the absence of increases in common measures of oxidative stress, and may underlie the metabolic deficits and contribute to pathological and clinical manifestation related to the cerebellum in patients with PSP.

A new splicing variant for human tyrosine hydroxylase in the adrenal medulla.

It has been reported that several mRNA isoforms of tyrosine 3-monooxygenase (tyrosine hydroxylase; TH) occur only in primates. New TH isoforms produced by skipping of exon 3 in the adrenal medulla of patients with progressive supranuclear palsy (PSP) have recently been reported, J. Neurochem. 67 (1996) 19. Here, we looked for the presence of new TH isoforms in control brains and adrenal medulla and in brains from patients with PSP. We found a novel type of TH mRNA in the adrenal medulla from one of the control subjects. The mRNA lacked exon 4, resulting in a premature stop codon at amino acid 147. This result suggests the importance of alternative splicing in the regulation of TH activity.

Phosphorylated mitogen-activated protein kinase (MAPK/ERK-P), protein kinase of 38 kDa (p38-P), stress-activated protein kinase (SAPK/JNK-P), and calcium/calmodulin-dependent kinase II (CaM kinase II) are differentially expressed in tau deposits in neurons and glial cells in tauopathies.

Calcium/calmodulin-dependent kinase II (alpha- and beta-CaM kinase II), and phosphorylated mitogen-activated extracellular signal-regulated protein kinase (MAPK/ERK-P), phosphorylated protein kinase of 38 kDa (p38-P) and phosphorylated stress-activated protein kinase (SAPK/JNK-P) expression have been examined in Alzheimer disease (AD), Pick's disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). The study was carried out to increase understanding of the signals that may regulate tau phosphorylation in tauopathies. MAPK/ERK-P was found in a subset of neurons and glial cells bearing abnormal tau deposition, but rarely in neurofibrillary tangles. Strong p38-P immunoreactivity was observed in about 50-70% of neurons with neurofibrillary tangles and in dystrophic neurites of senile plaques in AD. Strong p38-P immunoreactivity was seen in practically all Pick bodies in PiD, and in most neurons with neurofibrillary degeneration or with tau deposits (pre-tangle neurons) in PSP and CBD, as revealed with single and double-labeling immunohistochemistry to p38-P and tau. In addition, strong p38-P immunoreactivity was present in tau-positive astrocytes and in coiled bodies in PSP and CBD. Single and double-labeling immunohistochemistry to MAPK/ERK-P and p38-P disclosed that MAPK/ERK-P appeared at early stages of tau phosphorylation in neurons and glial cells in tauopathies, and that MAPK/ERK-P and p38-P co-localize only in a subset of neurons and glial cells with phosphorylated tau deposits. SAPK/JNK-P immunoreactivity was seen in a subset of neurons, including many neurons with neurofibrillary degeneration, and in glial cells accumulating abnormal tau, in AD, PiD, PSP and CBD. Double-labeling immunohistochemistry disclosed partial co-localization of SAPK/JNK-P and either MAPK/ERK-P or p-38-P immunoreactivity. These findings indicate that MAPK/ERK-P, SAPK/JNK-P and p-38-P are differentially expressed in association with tau deposits in tauopathies. Finally, CaM kinase II is present in neurons but not in glial cells, thus suggesting no role of CaM kinase II in tau phosphorylation of glial cells. These observations, together with previous results of in vitro studies, support the idea that several MAPK/ERK, SAPK/JNK, p38 and CaM kinase II may participate in tau phosphorylation in tauopathies. Lack of co-localization between MAPK/ERK-P, SAPK/JNK-P and p-38-P over-expression, and staining with the method of in situ end-labeling of nuclear DNA fragmentation in individual cells indicate that over-expression of these kinases is not linked with increased nuclear DNA vulnerability in AD, PiD, PSP and CBD.

Neuritic sprouting with aberrant expression of the nitric oxide synthase III gene in neurodegenerative diseases.

Neuronal loss, synaptic disconnection and neuritic sprouting correlate with dementia in Alzheimer's disease (AD). Nitric oxide (NO) is an important synaptic plasticity molecule generated by nitric oxide synthase (NOS) oxidation of a guanidino nitrogen of L-arginine. Experimentally, the NOS III gene is modulated with neuritic sprouting. In a previous study, NOS III expression was found to be abnormal in cortical neurons, white matter glial cells, and dystrophic neurites in AD and Down syndrome brains. The present study demonstrates the same abnormalities in neuronal and glial NOS III expression with massive proliferation of NOS III-immunoreactive neurites and glial cell processes in other neurodegenerative diseases including: diffuse Lewy body disease, Pick's disease, progressive supranuclear palsy, amyotrophic lateral sclerosis, multiple system atrophy, and Parkinson's disease. However, each disease, including AD, was distinguished by the selective alterations in NOS III expression and sprouting in structures marred by neurodegeneration. Double label immunohistochemical staining studies demonstrated nitrotyrosine and NOS III co-localized in only rare neurons and neuritic sprouts, suggesting that peroxynitrite formation and nitration of growth cone proteins may not be important consequences of NOS III enzyme accumulation. The results suggest that aberrant NOS III expression and NOS III-associated neuritic sprouting in the CNS are major abnormalities common to several important neurodegenerative diseases.

A human tyrosine hydroxylase isoform associated with progressive supranuclear palsy shows altered enzymatic activity.

A novel human tyrosine hydroxylase (HTH) messenger RNA subgroup generated by alternative splicing and characterized by the absence of the third exon was recently identified. The corresponding putative protein lacks 74 amino acids including Ser31 and Ser40, two major phosphorylation sites implicated in the regulation of HTH activity. These mRNA species are detected in adrenal medulla and are overexpressed in patients suffering from progressive supranuclear palsy, a neurodegenerative disease mostly affecting catecholaminergic neurons of the basal ganglia. In the present work, an HTH protein isoform lacking exon 3 was identified in human adrenal medulla. For this purpose, an antibody was raised against the HTH exon 3. The effect of the removal of exon 3 on the enzymatic activity of HTH was studied in vitro by comparing a purified recombinant fusion protein without exon 3 (glutathione S-transferase (GST)-HTHDelta3) to the equivalent protein containing exon 3 (GST-HTH3). In initial velocity conditions, GST-HTHDelta3 has 30% of the maximal velocity of GST-HTH3. Moreover, the skipping of exon 3 results in the absence of activation of GST-HTH by heparin and increases by 10-fold the retroinhibition constant for dopamine, demonstrating the involvement of exon 3 in the regulation of HTH enzymatic activity. The identification of a variably expressed HTH isoform that lacks an exon implicated in activity regulation supports the view that HTH alternative splicing contributes to the functional diversity within the catecholaminergic system and may be implicated in some neurological diseases.

Cyclin-dependent kinase 5 and mitogen-activated protein kinase in glial cytoplasmic inclusions in multiple system atrophy.

Glial cytoplasmic inclusions (GCI) characteristically occur in the oligodendrocytes of patients with multiple system atrophy (MSA). However, the molecular mechanisms underlying GCI formation are unknown. To investigate whether these inclusions are related to proline-directed protein kinases that have been associated with neuronal inclusion bodies in some other neurodegenerative diseases, we immunohistochemically probed tissue samples from MSA brains with a panel of antibodies against cyclin-dependent kinases and mitogen-activated protein kinase. We unexpectedly detected cyclin-dependent kinase 5- (cdk5) and mitogen-activated protein kinase- (MAPK) immunoreactivities in GCI. We also found TAU1 immunoreactivity in GCI, and a strong expression of microtubule-associated protein (MAP) 2 immunoreactivity in oligodendrocytes of MSA brains. This immunoreactivity was not observed in the normal or neurological controls. The accumulated evidence suggest a close association between GCI and the microtubular cytoskeleton. Cdk5 phosphorylates tau and MAP2, and MAPK is capable of phosphorylating MAP2. The present results suggest that the aberrant or ectopic expression of cdk5 and MAPK causes abnormal phosphorylation of microtubular cytoskeletal proteins, thus leading to GCI formation in affected oligodendrocytes.

Inducible nitric oxide synthase (iNOS)-like immunoreactivity in argyrophilic, tau-positive astrocytes in progressive supranuclear palsy.

The immunoreactivity to the free radical-related enzymes, nitric oxide synthase (NOS) and superoxide dismutase (SOD), was examined in brain tissue in progressive supranuclear palsy (PSP). To determine the relationship between the immunoexpression of these enzymes and tau-positive, argyrophilic cytoplasmic inclusions, which are constantly present in PSP brains, double-label immunohistochemistry was applied. We demonstrated for the first time that strong inducible NOS-like immunoreactivity (iNOS-ir) was detected in tau-positive astrocytes that bore tufts of abnormal fibers (TAF), but not in oligodendrocytes containing argyrophilic/tau-positive coiled bodies nor in microglia. No brain NOS-ir was detected in neurons with neurofibrillary tangles. MnSOD-ir was also detected in tau-positive astrocytes and oligodendrocytes. Nitrotyrosine-ir of variable intensity was observed in astrocytes, oligodendrocytes and neurons. Our results indicate: (1) that TAF-bearing astrocytes may be a major source of excessive NO in PSP brains; (2) that after the induction of iNOS by unknown stimulating factors, TAF-bearing astrocytes produce an excessive amount of NO that exceeds the detoxification capability of SOD; and (3) that peroxynitrite and excessive NO, both cytotoxic, may be present in astrocytes, oligodendrocytes and neurons. Although the precise relationship between NO production and neuronal cell death in PSP remained uncertain, based on the specificity of TAF for PSP brains, our results indicated a possible mechanism of NO-mediated cytotoxicity that may contribute to the neuronal and glial cell damage followed by abnormal tau accumulation in this disease.