g(m2)-ganglioside and Alzheimer-Disease

Alzheimer's Disease (AD) affects millions globally, but therapy development is lagging. New experimental systems that monitor neuronal functions in conditions approximating the AD brain may be beneficial for identifying new therapeutic strategies.. We expose cultured neurons to aqueous-soluble human brain extract from 43 individuals across a spectrum of AD pathology. Multi-electrode arrays (MEAs) and live-cell imaging were used to assess neuronal firing and neurite integrity (NI), respectively, following treatments of rat cortical neurons (MEA) and human iPSC-derived neurons (iN) with human brain extracts.. We observe associations between spontaneous activity and Aβ42:40 levels, between neurite integrity and oligomeric Aβ, and between neurite integrity and tau levels present in the brain extracts. However, these associations with Aβ and tau do not fully account for the effects observed. Proteomic profiling of the brain extracts revealed additional candidates correlated with neuronal structure and activity. Neurotoxicity in MEA and NI assays was associated with proteins implicated in lysosomal storage disorders, while neuroprotection was associated with proteins of the WAVE regulatory complex controlling actin cytoskeleton dynamics. Elevated ganglioside GM2 activator (GM2A) associates with reductions in both NI and MEA activity, and cell-derived GM2A alone is sufficient to induce a loss of neurite integrity and a reduction in neuronal firing.. The techniques and data herein introduce a system for modeling neuronal vulnerability in response to factors in the human brain and provide insights into proteins potentially contributing to AD pathogenesis.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; G(M2) Ganglioside; Gangliosides; Humans; Neurites; Neurons; Proteins; Proteomics; Rats; tau Proteins

A major characteristic of Alzheimer's disease (AD) is the accumulation of misfolded amyloid-β (Aβ) peptide. Several studies linked AD with type 2 diabetes due to similarities between Aβ and human amylin. This study investigates the effect of amylin and pramlintide on Aβ pathogenesis and the predisposing molecular mechanism(s) behind the observed effects in TgSwDI mouse, a cerebral amyloid angiopathy (CAA) and AD model. Our findings showed that thirty days of intraperitoneal injection with amylin or pramlintide increased Aβ burden in mice brains. Mechanistic studies revealed both peptides altered the amyloidogenic pathway and increased Aβ production by modulating amyloid precursor protein (APP) and γ-secretase levels in lipid rafts. In addition, both peptides increased levels of B4GALNT1 enzyme and GM1 ganglioside, and only pramlintide increased the level of GM2 ganglioside. Increased levels of GM1 and GM2 gangliosides play an important role in regulating amyloidogenic pathway proteins in lipid rafts. Increased brain Aβ burden by amylin and pramlintide was associated with synaptic loss, apoptosis, and microglia activation. In conclusion, our findings showed amylin or pramlintide increase Aβ levels and related pathology in TgSwDI mice brains, and suggest that increased amylin levels or the therapeutic use of pramlintide could increase the risk of AD.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Cerebral Amyloid Angiopathy; G(M1) Ganglioside; G(M2) Ganglioside; Islet Amyloid Polypeptide; Membrane Microdomains; Mice; Mice, Transgenic; N-Acetylgalactosaminyltransferases; Protein Processing, Post-Translational

CSF diagnostics has proved to be a formidable testing ground for N-glycoproteomic analysis of neurological diseases. To characterize specific N-glycan profiles of CSF in early and advanced phases of Alzheimer's disease, as well as in lysosomal storage disorders such as Tay-Sachs disease, we set up in our lab a robust and feasible protocol by coupling bioanalytical methods and mass spectrometry analysis.Starting from a few microliters of CSF, after protein denaturation, reduction, and alkylation, N-glycans are released from glycoproteins using the peptide-N-glycosidase F (PNGase F) and purified. The analysis of permethylated N-glycans by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and MALDI-TOF MS/MS allowed us to identify specific glyco-structures and also to distinguish between isobaric N-glycans.

Topics: Aged; Alzheimer Disease; G(M2) Ganglioside; Glycoproteins; Humans; Ions; Polysaccharides; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tay-Sachs Disease

The aging brain is often characterized by the presence of multiple comorbidities resulting in synergistic damaging effects in the brain as demonstrated through the interaction of Alzheimer's disease (AD) and stroke. Gangliosides, a family of membrane lipids enriched in the central nervous system, may have a mechanistic role in mediating the brain's response to injury as their expression is altered in a number of disease and injury states. Matrix-Assisted Laser Desorption Ionization (MALDI) Imaging Mass Spectrometry (IMS) was used to study the expression of A-series ganglioside species GD1a, GM1, GM2, and GM3 to determine alteration of their expression profiles in the presence of beta-amyloid (Aβ) toxicity in addition to ischemic injury. To model a stroke, rats received a unilateral striatal injection of endothelin-1 (ET-1) (stroke alone group). To model Aβ toxicity, rats received intracerebralventricular (i.c.v.) injections of the toxic 25-35 fragment of the Aβ peptide (Aβ alone group). To model the combination of Aβ toxicity with stroke, rats received both the unilateral ET-1 injection and the bilateral icv injections of Aβ25-35 (combined Aβ/ET-1 group). By 3 d, a significant increase in the simple ganglioside species GM2 was observed in the ischemic brain region of rats who received a stroke (ET-1), with or without Aβ. By 21 d, GM2 levels only remained elevated in the combined Aβ/ET-1 group. GM3 levels however demonstrated a different pattern of expression. By 3 d GM3 was elevated in the ischemic brain region only in the combined Aβ/ET-1 group. By 21 d, GM3 was elevated in the ischemic brain region in both stroke alone and Aβ/ET-1 groups. Overall, results indicate that the accumulation of simple ganglioside species GM2 and GM3 may be indicative of a mechanism of interaction between AD and stroke.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Brain Ischemia; G(M1) Ganglioside; G(M2) Ganglioside; G(M3) Ganglioside; Male; Peptide Fragments; Rats, Wistar; Reperfusion Injury; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Alzheimer's disease (AD) is a neurodegenerative disorder where β-amyloid tends to aggregate and form plaques. Lipid raft-associated ganglioside GM1 has been suggested to facilitate β-amyloid aggregation; furthermore, GM1 and GM2 are increased in lipid rafts isolated from cerebral cortex of AD cases.. The distribution of GM1 and GM2 was studied by immunohistochemistry in the frontal and temporal cortex of AD cases. Frontotemporal dementia (FTD) was included as a contrast group.. The distribution of GM1 and GM2 changes during the process of AD (n = 5) and FTD (n = 3) compared to controls (n = 5). Altered location of the GM1-positive small circular structures seems to be associated with myelin degradation. In the grey matter, the staining of GM1-positive plasma membranes might reflect neuronal loss in the AD/FTD tissue. The GM1-positive compact bundles were only visible in cells located in the AD frontal grey matter, possibly reflecting raft formation of GM1 and thus a pathological connection. Furthermore, our results suggest GM2 to be enriched within vesicles of pyramidal neurons of the AD/FTD brain.. Our study supports the biochemical finding of ganglioside accumulation in cellular membranes of AD patients and shows a redistribution of these molecules.

Topics: Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Female; Frontal Lobe; Frontotemporal Dementia; G(M1) Ganglioside; G(M2) Ganglioside; Humans; Immunohistochemistry; Male; Membrane Microdomains; Middle Aged; Myelin Sheath; Neurons; Research Design; Temporal Lobe

Ganglioside lipid fractions in the cerebral gray matter were studied in 13 patients with various forms of dementia. In 2 patients with Alzheimer's disease and 1 with senile dementia an abnormal ganglioside pattern was observed, i.e., a decrease of G1 and G3 in association with an increase of G2. In the light of the total clinical and histologic data on the patients, it would seem that this disturbance in ganglioside metabolism may be a phenomenon accompanying extensive degradation of brain tissue rather than a factor in the etiology of dementia.

Topics: Adult; Aged; Alzheimer Disease; Autopsy; Brain; Brain Chemistry; Dementia; Female; G(M2) Ganglioside; Gangliosides; Humans; Male; Middle Aged; Superior Colliculi; Temporal Lobe