Jerzy Wegiel

Brain region‐specific deficit in mitochondrial electron transport chain complexes in children with autism

J. Neurochem. (2011) 117, 209–220.

Reduced number and altered morphology of microglial cells in colony stimulating factor-1-deficient osteopetrotic op/op mice

The numerical density of microglial cells is reduced by 47% in the corpus callosum, by 37% in the parietal cortex and by 34% in the frontal cortex of mice mutant at the op locus which are totally devoid of colony stimulating factor-1 (CSF-1), the major growth factor for macrophages. Moreover, microglia in the frontal cortex of the op/op mice are smaller and have shorter cytoplasmic processes compared to control mice. Study suggests that CSF-1 plays a role in vivo in the formation and maturation of microglia and has little or no effect on perivascular cells.

Walnut Extract Inhibits the Fibrillization of Amyloid Beta-Protein, and also Defibrillizes its Preformed Fibrils

Fibrillar amyloid beta-protein (Abeta) is the principal component of amyloid plaques in the brains of patients with Alzheimers disease. We have studied the effect of walnut extract on Abeta fibrillization by Thioflavin T fluorescence spectroscopy and electron microscopy. The walnut extract not only inhibited Abeta fibril formation in a concentration and time- dependent manner but it was also able to defibrillize Abeta preformed fibrils. Over 90% inhibition of Abeta fibrillization was observed with 5 microl of methanolic extract of walnut (MEOW) both after 2 and 3 days of incubation. The maximum defibrillization (91.6%) was observed when preformed Abeta fibrils were incubated with 10 microl of MEOW for 2 days. These results suggest that walnuts may reduce the risk or delay the onset of Alzheimers disease by maintaining Abeta in the soluble form. Further studies showed that anti-amyloidogenic compound in walnut is an organic compound of molecular weight less than 10 kDa, which is neither a lipid nor a protein. Chloroform extract of walnut had no effect on Abeta fibrillization while MEOW and its 10 kDa filtrate inhibited Abeta fibrillization equally. It is proposed that polyphenolic compounds (such as flavonoids) present in walnuts may be responsible for its anti-amyloidogenic activity.

Gelsolin is Proteolytically Cleaved in the Brains of Individuals with Alzheimer's Disease

Gelsolin, a multifunctional actin-binding protein, forms a complex with amyloid-beta protein and reduces the amyloid load in the transgenic mouse model of Alzheimers disease (AD). Gelsolin consists of six homologous domains, which have specific affinities for phosphatidylinositol 4, 5-bisphosphate, calcium, and actin. During apoptosis, gelsolin is cleaved by the caspase-3 resulting in a 48 kDa carboxyl-terminal fragment (gelsolin-CTF). We report here that gelsolin is significantly cleaved in the frontal cortex of individuals with AD as compared to age-matched controls. A positive correlation was observed between the appearance of gelsolin-CTF in frontal cortex and severity of AD. Gelsolin-CTF was also observed in apoptotic SH-SY5Y cells induced by H2O2 or calcium ionophore A23187. In addition, lipid peroxidation was increased in the frontal cortex of AD suggesting that oxidative stress occurs in AD brain. Taken together, these results suggest that there may be a link among oxidative stress, neuronal apoptosis, and gelsolin cleavage in AD.

Binding of trypsin to fibrillar amyloid beta-protein.

We have recently reported that fibrillar amyloid beta-protein (Abeta) inhibits the proteolytic activity of trypsin and high molecular weight bovine brain protease. We report here that trypsin binds to fibrillar Abeta (fAbeta) and the resulting complex of trypsin/fAbeta is sodium dodecyl sulfate (SDS)-stable. Electron microscopic analysis confirmed the binding of trypsin on the fibrils of both Abeta 1-40 and Abeta 1-42. SDS-polyacrylamide gel electrophoresis (PAGE) of fAbeta sample incubated in the presence of trypsin showed that major amount of trypsin was associated with fAbeta that did not enter the gel. The presence of trypsin in this protein complex was confirmed by Western blotting after its elution from the gel. Kinetic studies showed that the binding of trypsin to fibrillar Abeta was dependent on the degree of Abeta fibrillization and on the concentration of fAbeta. However, the trypsin binding to Abeta oligomers did not affect the fibril growth. The maximum binding (B(max)) of trypsin to fAbeta 1-40 and fAbeta 1-42 was 36 pmol and 40 pmol, and dissociation constant (K(d)) was 18.31 microM and 20 microM respectively. Similar to fAbeta, trypsin could also bind to fibrillar amylin. This binding was dependent on the concentration of fibrillar amylin. Under similar conditions, bovine serum albumin did not bind to fibrillar Abeta. These results suggest that fAbeta and fibrillar amylin have strong affinities for trypsin, and chelation of proteases by abnormal aggregated proteins may be a general mechanism for inflicting pathological conditions in various diseases.

Delayed Development of the Claustrum in Autism

The clinical phenotype of autism, with deficits in social interactions; verbal and nonverbal communication; and restricted repetitive and stereotyped patterns of behavior, interests and activities, suggests that numerous high-order functions are not processed properly. Extensive reciprocal connections between the claustrum and almost all brain regions suggest that developmental alterations of the claustrum may contribute to autism’s clinical profile, as it integrates a number of physiological processes that collectively maintain contact between the individual and the environment. Stereological studies revealed a significant delay of neuronal growth in the claustrum. Examination of older children and adults with autism shows that during the teenage years acceleration of neuronal growth results in a partial correction of neuronal size in the claustrum. n nDesynchronization of neuronal growth in the claustrum and interacting brain modalities, including the social brain, the sensorimotor system and the memory system, appears to be a significant contributor to the clinical symptoms of autism. A smaller claustrum and undersized neurons could be indicative of underconnectivity in the brains of autistic subjects. Underconnectivity of the claustrum may result in defects/deficits of the integration of cortical and subcortical modalities and may contribute to the cognitive impairment, repetitive behaviors, deficits of social interactions, altered processing of sensory signals and other components of the autistic phenotype.

Amyloidosis in prion diseases and cells involved in PrP fibrillogenesis.

Prion protein (PrP) plaque formation and neuronal degeneration with spongiform changes and astrogliosis and microgliosis are major neuropathological changes in transmissible encephalopathies. The target in kuru. Creutzfeldt-Jakob disease (CJD). and Gerstmann-Straussler-Scheinker disease (GSS) in humans, and scrapie, bovine spongiform encephalopathy, transmissible mink encephalopathy is nerve cell membrane. I. Also, infectivity in spongiform encephalopathies is associated with cell mernbrane~. .~ Amyloid fibrils are composed of very similar molecules in CJD, GSS, and in plaques of animals suffering from spongiform encephalopathies both naturally occurring and infected experimentally.5 Chemically heterogeneous amyloid proteins are seen in a number of disorders with different etiologies and clinical manifestations, but they share the common properties of Congo-red binding with green birefringence when viewed under polarized light and a fibrillar appearance at the ultrastructural level. Fibrillogenesis links transmissible encephalopathies with other amyloidoses, especially with P-amyloidosis in Alzheimer disease (AD). In both types of amyloidoses, fibrils are deposited in brain, and in both, microglial cells are involved in amyloid fibril format i~n .~ , The genes encoding the precursor proteins are identified, cloned, and sequenced in several amyloidoses, including p-amyloidosis in AD. and PrP amyloidosis in scrapie.. Recent morphological studies provide new data about plaque pathogenesis, amyloid deposit formation, and the types of cells engaged in fibrillogenesis in both AD and spongiform encephalopathies.

Clinicopathological Stratification of Idiopathic Autism and Autism with 15q11.2-q13 Duplications

Postmortem studies of brains of individuals with idiopathic autism and 15q11.2–q13 duplications autism (dup(15)) identify a cluster of neuropathological features differentiating these cohorts. They show a need for both reclassification of autism according to etiology, clinical presentation and neuropathology, and a commonality of clinical and neuropathological traits justifying autism diagnosis. The features differentiating these cohorts include: (a) maternal origin in patients with dup(15); (b) autism in 78% of subjects; (c) more severe clinical phenotypes, with intellectual deficit (100%), early-onset of severe or intractable seizures in 78% of subjects, and increased prevalence (up to 67%) of sudden unexplained death; (d) high prevalence of microcephaly, with mean brain weight 300g less than in idiopathic autism; (e) several-fold increase in the number of developmental abnormalities, including defects of migration and dysplastic changes, especially numerous in the hippocampal formation; and (f) significant increase in the intraneuronal amyloid load, reflecting enhanced amyloid-β precursor protein processing with α-secretase.

Cellular and Test Tube Models of Amyloid-βFormation

Aggregation of Alzheimer’s amyloid-β peptide (Aβ) and formation of amyloid plaques and vascular amyloid are considered a cause of dementia of the Alzheimer’s type. The mechanisms and/or agents that trigger fibrillization of Aβ, which could be the targets of rational therapy for Alzheimer’s disease (AD), are still unknown. The lack of appropriate experimental models has restricted the search for potential anti-β-amyloidogenic drugs and the development of treatment procedures. In the present study, we demonstrated the cellular model of β-amyloidogenesis, which appears to possess various features of the in vivo pathology and could be useful for drug evaluation. We also used cell-free in vitro methods to examine the ability of various factors to interfere with aggregation and fibrillization of synthetic Aβ.

Neuropathological Bases of Alzheimer Disease, Implications for Treatment

Neuropathological implications for Alzheimer disease (AD) treatment are based on several basic observations. There appears to be more than one cause of development of AD neuropathology and therefore, AD might be considered a syndrome. The duration of both the clinical and the preclinical course is very long. Discoveries of the proteins (s-peptide, over-phosphorylated tau, apolipoprotein (Apo) E4 and other amyloid-associated proteins) and the cells (microglia, perivascular cells and myocytes) that participate in amyloid formation open a new avenue for development of therapeutic strategies in prevention and treatment of AD.