Biomedical subjects

Roger M Nitsch

Publications and source records attributed to Roger M Nitsch.

At least 37 records · Page 2Linked to original sources

PubMed2005

No influence of amyloid-beta-degrading neprilysin activity on prion pathogenesis.

Transmissible spongiform encephalopathies are characterized by the accumulation of PrPSc, a protease-resistant form of a host-derived protein termed PrPC. Substantial evidence indicates that PrPSc represents an essential component of the infectious agent, which is termed prion. The accumulation of PrPSc within the central nervous system of prion-infected organisms is a dynamic process that is regulated both by production and by clearance of PrPSc. Although several proteases have been implicated in proteolysis of PrPC, the mechanisms underlying proteolysis of PrPSc remain unclear. Here, it was investigated whether neprilysin, a metalloprotease known to degrade extracellular amyloidogenic proteins such as amyloid-beta, plays a role in prion pathogenesis in vivo. As neprilysin has a broad substrate specificity and is localized subcellularly in the vicinity of PrP, it represents a plausible candidate for prion degradation. Prions were therefore administered to mice lacking or overexpressing neprilysin in brain. However, the gene dosage of neprilysin did not modulate accumulation of PrPSc in brain. Also, incubation times and clinical course of prion disease, as well as brain infectivity titres at terminal stage, were unaffected. These data rule out neprilysin as a major modulator of PrPSc accumulation and prion pathogenesis.

Amyloid beta-Peptides↗

PubMed2005

The novel cytosolic RING finger protein dactylidin is up-regulated in brains of patients with Alzheimer's disease.

Alzheimer's disease (AD) is characterized by a progressive degeneration of neurons along with deposition of amyloid plaques and the formation of neurofibrillary tangles. Neurodegeneration in AD follows both a spatial pattern of selective vulnerability and temporal staging of affected neurons. In order to address transcriptional changes associated with this selective vulnerability, we used subtractive hybridization of transcripts derived from human frontal cortex, which degenerates in late stages of AD, against transcripts of the inferior temporal cortex, which is affected both heavily and early in the course of AD. Moreover, we compared these to brain sections obtained from age-matched control subjects. We isolated a differentially expressed novel gene encoding a polypeptide that contained an amino-terminal C3HC4 RING finger domain, called dactylidin. It is ubiquitously expressed in all tissues examined and in situ hybridization of mouse brain sections revealed specific expression in neurons. Further, heterologous expression studies revealed a cytoplasmic localization of dactylidin and as all known cytoplasmic RING finger proteins function as ubiquitin protein ligases, an E3-like ligase function of dactylidin is probable. However, the up-regulation of dactylidin in highly vulnerable brain tissues of AD patients was confirmed by a quantitative PCR approach, suggesting that dactylidin may function early in the progression of neurodegenerative diseases.

Aged↗

PubMed2005

Cholesterol 25-hydroxylase on chromosome 10q is a susceptibility gene for sporadic Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia. It is characterized by beta-amyloid (A beta) plaques, neurofibrillary tangles and the degeneration of specifically vulnerable brain neurons. We observed high expression of the cholesterol 25-hydroxylase (CH25H) gene in specifically vulnerable brain regions of AD patients. CH25H maps to a region within 10q23 that has been previously linked to sporadic AD. Sequencing of the 5' region of CH25H revealed three common haplotypes, CH25Hchi2, CH25Hchi3 and CH25Hchi4; CSF levels of the cholesterol precursor lathosterol were higher in carriers of the CH25Hchi4 haplotype. In 1,282 patients with AD and 1,312 healthy control subjects from five independent populations, a common variation in the vicinity of CH25H was significantly associated with the risk for sporadic AD (p = 0.006). Quantitative neuropathology of brains from elderly non-demented subjects showed brain A beta deposits in carriers of CH25Hchi4 and CH25Hchi3 haplotypes, whereas no A beta deposits were present in CH25Hchi2 carriers. Together, these results are compatible with a role of CH25Hchi4 as a putative susceptibility factor for sporadic AD; they may explain part of the linkage of chromosome 10 markers with sporadic AD, and they suggest the possibility that CH25H polymorphisms are associated with different rates of brain A beta deposition.

5' Untranslated Regions↗

PubMed2005

Clinical observations with AN-1792 using TAPIR analyses.

Clinical observations with AN-1792 using tissue amyloid plaque immunoreactivity (TAPIR) analyses established for the first time evidence in humans that antibodies against beta-amyloid-related epitopes are capable of slowing progression in Alzheimer's disease. Antibodies derived upon TAPIR assay selection may specifically target the pathologic neoepitopes of aggregated A beta species present in amyloid plaques and some of their aggregated, protofibrillar and low molecular weight oligomeric precursors. We briefly summarize here how the proof of concept was established and why it provides the basis for a potential cure for Alzheimer's disease.

Alzheimer Disease↗

PubMed2005

A cluster of cholesterol-related genes confers susceptibility for Alzheimer's disease.

OBJECTIVE: Polygenic diseases are related to the complex interplay of genetic variations. We evaluated whether clusters of cholesterol- and lipid-related genetic variations are associated with Alzheimer's disease. METHOD: We analyzed 12 cholesterol-related single nucleotide polymorphisms and 48 control polymorphisms in 545 study participants (Alzheimer's disease group N = 284; control group N = 261). Diagnoses of Alzheimer's disease were made according to the NINCDS-ADRDA criteria. Multi-locus genetic association analysis was done with the set-association method. Dates of data collection were from January 2000 to December 2003. RESULTS: We identified a cluster of polymorphisms in APOE, SOAT1, APOE 5'-untranslated region, OLR1, CYP46A1, LPL, LIPA, and APOA4 conferring significant (p = .0002) susceptibility for Alzheimer's disease. This gene cluster reached a diagnostic accuracy of 74% and correlated significantly (p = .018) with the levels of the brain cholesterol catabolite 24S-hydroxycholesterol in the cerebrospinal fluid. CONCLUSION: Our results establish a novel approach for the identification of disease-related genetic clusters and demonstrate the need for multi-locus methods in the genetics of complex diseases.

Aged↗

PubMed2004

Laboratory animal welfare: cage enrichment and mouse behaviour.

Mice housed in standard cages show impaired brain development, abnormal repetitive behaviours (stereotypies) and an anxious behavioural profile, all of which can be lessened by making the cage environment more stimulating. But concerns have been raised that enriched housing might disrupt standardization and so affect the precision and reproducibility of behavioural-test results (for example, see ref. 4). Here we show that environmental enrichment increases neither individual variability in behavioural tests nor the risk of obtaining conflicting data in replicate studies. Our findings indicate that the housing conditions of laboratory mice can be markedly improved without affecting the standardization of results.

Analysis of Variance↗

PubMed2004

Possible association of mitochondrial transcription factor A (TFAM) genotype with sporadic Alzheimer disease.

Mitochondrial transcription factor A (TFAM) is essential for transcription and replication of mammalian mitochondrial DNA (mtDNA). Disturbance of maintenance of mtDNA integrity or mitochondrial function may underlay neurodegenerative disorders such as Alzheimer disease (AD). TFAM, the gene encoding TFAM maps to chromosome 10q21.1, a region that showed linkage to late-onset AD in several study samples. We screened TFAM for single nucleotide polymorphisms (SNPs) and genotyped the G>C SNP rs1937, coding for S12T in mitochondrial signal sequence of TFAM, and the A>G SNP rs2306604 (IVS4+113A>G) in 372 AD patients and 295 nondemented control subjects. There was an association of genotype rs1937G/G with AD in females and an association of a TFAM haplotype with AD both in the whole sample and in females. The findings suggest that a TFAM haplotype containing rs1937 G (for S12) may be a moderate risk factor for AD.

Alzheimer Disease↗

PubMed2004

The APP intracellular domain forms nuclear multiprotein complexes and regulates the transcription of its own precursor.

The physiological functions of the beta-amyloid precursor protein (APP) may include nuclear signaling. To characterize the role of the APP adaptor proteins Fe65, Jip1b, X11alpha (MINT1) and the chromatin-associated protein Tip60, we analyzed their interactions by confocal microscopy and co-immunoprecipitations. AICD corresponding to S3-cleaved APP bound to Fe65 that transported it to nuclei and docked it to Tip60. These proteins formed AICD-Fe65-Tip60 (AFT) complexes that were concentrated in spherical nuclear spots. gamma-Secretase inhibitors prevented AFT-complex formation with AICD derived from full-length APP. The APP adaptor protein Jip1b also transported AICD to nuclei and docked it to Tip60, but AICD-Jip1b-Tip60 (AJT) complexes had different, speckle-like morphology. By contrast, X11alpha trapped AICD in the cytosol. Induced AICD expression identified the APP-effector genes APP, BACE, Tip60, GSK3beta and KAI1, but not the Notch-effector gene Hes1 as transcriptional targets. These data establish a role for APP in nuclear signaling, and they suggest that therapeutic strategies designed to modulate the cleavage of APP affect AICD-dependent signaling.

Acetyltransferases↗

PubMed2004

Age-dependent neurodegeneration and Alzheimer-amyloid plaque formation in transgenic Drosophila.

Beta-amyloid peptides that are cleaved from the amyloid precursor protein (APP) play a critical role in Alzheimer's disease (AD) pathophysiology. Here, we show that in Drosophila, the targeted expression of the key genes of AD, APP, the beta-site APP-cleaving enzyme BACE, and the presenilins led to the generation of beta-amyloid plaques and age-dependent neurodegeneration as well as to semilethality, a shortened life span, and defects in wing vein development. Genetic manipulations or pharmacological treatments with secretase inhibitors influenced the activity of the APP-processing proteases and modulated the severity of the phenotypes. This invertebrate model of amyloid plaque pathology demonstrates Abeta-induced neurodegeneration as a basic biological principle and may allow additional genetic analyses of the underlying molecular pathways.

Age Factors↗

PubMed2004

Anti-amyloid activity of neprilysin in plaque-bearing mouse models of Alzheimer's disease.

Abnormally high concentrations of beta-amyloid peptide (Abeta) and amyloid plaque formation in Alzheimer's disease (AD) may be caused either by increased generation or by decreased degradation of Abeta. Therefore, activation of mechanisms that lower brain Abeta levels is considered valuable for AD therapy. Neuronal upregulation of neprilysin (NEP) in young transgenic mice expressing the AD-causing amyloid precursor protein mutations (SwAPP) led to reduction of brain Abeta levels and delayed Abeta plaque deposition. In contrast, a comparable increase of brain NEP levels in aged SwAPP mice with pre-existing plaque pathology did not result in a significant reduction of plaque pathology. Therefore, we suggest that the potential of NEP for AD therapy is age-dependent and most effective early in the course of AD pathophysiology.

Age Factors↗

PubMed2004

Antibodies from a DNA peptide vaccination decrease the brain amyloid burden in a mouse model of Alzheimer's disease.

The neuropathology of Alzheimer's disease(AD) is characterized by the accumulation of amyloid peptide Abeta in the brain derived from proteolytic cleavage of the amyloid precursor protein (APP). Vaccination of mice with plasmid DNA coding for the human Abeta42 peptide together with low doses of preaggregated peptide induced antibodies with detectable titers after only 2 weeks. One serum was directed against the four aminoterminal amino acids DAEF and differs from previously described ones. Both immune sera and monoclonal antibodies solubilized preformed aggregates of Abeta42 in vitro and recognized amyloid plaques in brain sections of mice transgenic for human APP. Passive immunization of transgenic AD mice caused a significant and rapid reduction in brain amyloid plaques within 24 h. The combined DNA peptide vaccine may prove useful for active immunization with few inoculations and low peptide dose which may prevent the recently described inflammatory reactions inpatients. The monoclonal antibodies are applicable for passive immunization studies and may lead to a therapy of AD.

Alzheimer Disease↗

PubMed2004

Accelerated extinction of conditioned taste aversion in P301L tau transgenic mice.

Neurofibrillary tangles, insoluble protein deposits composed of filamentous tau aggregates, are neuropathological hallmarks of Alzheimer's disease and familial frontotemporal dementia (FTDP-17). Transgenic mice expressing the FTDP-17 mutation P301L of tau recapitulate key features of the human pathology, that is, tau proteins aggregate and neurofibrillary tangles begin to appear in the amygdala at 6 months of age. To detect early signs of tau aggregate-associated changes, we investigated behavioral alterations and cognitive deficits in such mice using an amygdala-specific test battery for anxiety-related and cognitive behavior. P301L mice had anxiety levels not different from wild-types, but their exploratory behavior was significantly increased. Acquisition of a fear response to tone and context as well as taste aversion was comparable to wild-types. However, extinction of a conditioned taste aversion was significantly accelerated. We conclude that already aggregation of tau proteins not yet accompanied by massive formation of neurofibrillary tangles causes selective behavioral deficits.

Animals↗

PubMed2004

Active immunization of mice with an Abeta-Hsp70 vaccine.

Heat-shock proteins are highly immunogenic. Complexed with an antigen, they act as adjuvants, inducing a humoral and cellular immune response against both the antigen and the chaperone. In this study, we produced an Hsp70-supported vaccine to induce the generation of antibodies against amyloid-beta (Abeta) peptides, the major constituent of beta-amyloid plaques in Alzheimer's disease. The vaccine consisted of synthetic human Abeta42 covalently cross-linked with DnaK, an Hsp70 homolog of Escherichia coli. Active immunization of mice with this vaccine resulted in the generation of antibodies against Abeta, that were detectable in sera after the first booster immunization. Antibody titers varied markedly with the genetic background of the mice. Prophylactic short-term immunization of transgenic mice (APP tg2576) before the onset of plaques, however, did not prevent amyloid plaque deposition. There were no differences in the plaque load and in the level of Triton X-100-soluble Abeta peptides in the brains of immunized and control-treated transgenic mice. Unexpectedly, the level of formic-acid soluble Abeta peptides tended to be higher in immunized mice. The reason for the increase may be an enhanced deposition of Abeta in the small cerebral blood vessels. These data emphasize the need for anti-Abeta antibodies that remove Abeta peptides from the central nervous system without negative side effects.

Adjuvants, Immunologic↗

PubMed2004

Assessment of the bioactivity of antibodies against beta-amyloid peptide in vitro and in vivo.

The accumulation of the beta-amyloid peptide (Abeta) is a central event in the pathogenesis of Alzheimer's disease (AD). Abeta removal from the brain by immune therapy shows promising potential for the treatment of patients with AD, although the mechanisms of the antibody action are incompletely understood. In this study we compared the biological activities of antibodies raised against various Abeta fragments for Abeta reduction in vitro and in vivo. Antibodies against Abeta enhanced the uptake of Abeta42 aggregates up to 6-fold by primary microglial cells in vitro. The kinetics of Abeta42 uptake varied considerably among antibodies. Based on the activity to mediate Abeta42 uptake by microglial cells, we identified a bioactive antibody that significantly reduced Abeta42 levels in the brains of transgenic mice with neuronal expression of an AD-related mutated amyloid precursor protein. This effect depended on the epitopes recognized by the antibody. Our data suggest that the ability to facilitate Abeta42 uptake by primary microglia cells in vitro can be used to predict the biological activity of the antibody by passive immunization in vivo. This protocol may prove useful for the rapid validation of the activity of antibodies designed to be used in immune therapy of AD.

Amyloid beta-Peptides↗

PubMed2004

Cerebrospinal fluid profile of amyloid beta peptides in patients with Alzheimer's disease determined by protein biochip technology.

Amyloid-beta peptides (Abeta) are major components of amyloid plaques in the Alzheimer's disease (AD) brain and have been proposed as diagnostic markers in cerebrospinal fluid (CSF). Abeta derived from brain may be processed into fragments before emerging in CSF. Therefore, we determined mass profiles of Abeta peptides in CSF of patients with AD and age-matched healthy control subjects (CTR) by using protein biochip technology. Abeta peptides were captured on the chip surfaces (spots) by the specific monoclonal antibody 6E10 and were then analyzed by integrated surface-enhanced laser desorption and ionization time-of-flight mass spectrometry (SELDI-TOF-MS). We found Abeta species with mean molecular masses at 1,583.3 Da (corresponding to Abeta2-14), 2,068.5 Da (Abeta1-17), 2,166.4 Da (Abeta1-18), 3,676.6 Da (Abeta1-33), 3,789.4 Da (Abeta1-34), 4,076.9 Da (Abeta1-37), 4,134.0 Da (Abeta1-38), 4,233.3 Da (Abeta1-39), 4,332.4 Da (Abeta1-40) and 4,516.8 Da (Abeta1-42) in both AD (n = 24) and CTR (n = 24) subjects. Abeta1-38 appeared to be a major Abeta species in human CSF along with Abeta1-40. Quantitation revealed that CSF levels of Abeta1-38 were significantly decreased in AD as compared to CTR subjects. The CSF profile of Abeta peptides may be used for diagnostic and therapeutic purposes in clinical studies.

Aged↗

PubMed2004

Low-dose cortisol for symptoms of posttraumatic stress disorder.

OBJECTIVE: Because elevated cortisol levels inhibit memory retrieval in healthy human subjects, the present study investigated whether cortisol administration might also reduce excessive retrieval of traumatic memories and related symptoms in patients with chronic posttraumatic stress disorder (PTSD). METHOD: During a 3-month observation period, low-dose cortisol (10 mg/day) was administered orally for 1 month to three patients with chronic PTSD in a double-blind, placebo-controlled, crossover design. RESULTS: In each patient investigated, there was a significant treatment effect, with cortisol-related reductions of at least 38% in one of the daily rated symptoms of traumatic memories, as assessed by self-administered rating scales. In accordance, Clinician-Administered PTSD Scale ratings assessed after each month showed cortisol-related improvements for reexperiencing symptoms and, additionally, in one patient for avoidance symptoms. CONCLUSIONS: The results of this pilot study indicate that low-dose cortisol treatment reduces the cardinal symptoms of PTSD.

Administration, Oral↗

PubMed2004

BACE1 overexpression regulates amyloid precursor protein cleavage and interaction with the ShcA adapter.

The amyloid precursor protein (APP) is a cell surface protein with a large extracellular N-terminal domain, a single transmembrane segment, and a short cytoplasmic tail. Its location and structural features are characteristic of a receptor for signal transduction. Yet, the physiological function of APP is unclear, although it is well documented that APP's proteolytic processing, through the formation of membrane-bound C-terminal fragments (CTFs) and of beta-amyloid peptides, likely influences the development of Alzheimer's disease (AD). There is evidence that BACE1 is the enzyme responsible for beta-site cleavage of the APP and for the generation of CTFs. BACE1 expression is upregulated in AD brain, and we have recently shown in human brain and in vitro that BACE product CTFs, when phosphorylated in tyrosine residues, interact with the adaptor proteins ShcA and Grb2, which usually are involved in signal transduction pathways. We investigated the interaction between ShcA, APP, and CTFs in the H4 human cell line that overexpresses BACE1 to clarify the significance of such interactions in vitro and for AD generation. Our result show that the APP, CTF, and ShcA interaction is induced only upon overexpression of BACE1 either transiently or in stable cell lines. In particular, although BACE1 drives the formation of C99 and C89 CTFs, only C99 interacts with the ShcA adaptor protein. Therefore, our data suggest that BACE1 activity influences APP processing and its intracellular signaling through the ShcA adaptor protein.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Glucocorticoid-related genetic susceptibility for Alzheimer's disease.

Because glucocorticoid excess increases neuronal vulnerability, genetic variations in the glucocorticoid system may be related to the risk for Alzheimer's disease (AD). We analyzed single-nucleotide polymorphisms in 10 glucocorticoid-related genes in a population of 814 AD patients and unrelated control subjects. Set-association analysis revealed that a rare haplotype in the 5' regulatory region of the gene encoding 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1) was associated with a 6-fold increased risk for sporadic AD. Results of a reporter-gene assay indicated that the rare risk-associated haplotype altered HSD11B1 transcription. HSD11B1 controls tissue levels of biologically active glucocorticoids and thereby influences neuronal vulnerability. Our results indicate that a functional variation in the glucocorticoid system increases the risk for AD, which may have important implications for the diagnosis and treatment of this disease.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗