Amyloid precursor proteins in the cerebellar cortex of Alzheimer's disease patients devoid of cerebellar beta-amyloid deposits: immunocytochemical study of five cases

Characterization of cerebellar amyloid-β deposits in Alzheimer disease

Cerebellar amyloid-β (Aβ) plaques are a component of the diagnostic criteria used in Thal staging and ABC scoring for Alzheimer disease (AD) neuropathologic change. However, Aβ deposits in this anatomic compartment are unique and under-characterized; and their relationship with other pathological findings are largely undefined. In 73 cases of pure or mixed AD with an A3 score in the ABC criteria, parenchymal (plaques) and vascular (cerebral amyloid angiopathy [CAA]) cerebellar Aβ-42 deposits were characterized with respect to localization, morphology, density, and intensity. Over 85% of cases demonstrated cerebellar Aβ-42 parenchymal staining that correlated with a Braak stage V-VI/B3 score (p < 0.01). Among the 63 with cerebellar Aβ-42 deposits, a diffuse morphology was observed in 75% of cases, compact without a central dense core in 32%, and compact with a central dense core in 16% (all corresponding to plaques evident on hematoxylin and eosin staining). Cases with Purkinje cell (PC) loss showed higher proportions of PC layer Aβ-42 staining than cases without PC loss (88% vs 44%, p = 0.02), suggesting a link between Aβ-42 deposition and PC damage. Among all 73 cases, CAA was observed in the parenchymal vessels of 19% of cases and in leptomeningeal vessels in 44% of cases.

Reflections on Cerebellar Neuropathology in Classical Scrapie

In this review, the most important neuropathological changes found in the cerebella of sheep affected by classical natural scrapie are discussed. This disease is the oldest known of a group of unconventional “infections” caused by toxic prions of different origins. Scrapie is currently considered a “transmissible spongiform encephalopathy” (due to its neuropathological characteristics and its transmission), which is the paradigm of prion pathologies as well as many encephalopathies (prion-like) that present aberrant deposits of insoluble protein with neurotoxic effects due to errors in their catabolization (“misfolding protein diseases”). The study of this disease is, therefore, of great relevance. Our work data from the authors’ previous publications as well as other research in the field. The four most important types of neuropathological changes are neuron abnormalities and loss, neurogliosis, tissue vacuolization (spongiosis) and pathological or abnormal prion protein (PrP) deposits/deposition. These findings were analyzed and compared to other neuropathologies. Various aspects related to the presentation and progression of the disease, the involution of different neuronal types, the neuroglial responses and the appearance of abnormal PrP deposits are discussed. The most important points of controversy in scrapie neuropathology are presented.

BARHL1 Is Downregulated in Alzheimer's Disease and May Regulate Cognitive Functions through ESR1 and Multiple Pathways

The Transcription factor BarH like homeobox 1 (BARHL1) is overexpressed in medulloblastoma and plays a role in neurogenesis. However, much about the BARHL1 regulatory networks and their functions in neurodegenerative and neoplastic disorders is not yet known. In this study, using a tissue microarray (TMA), we report for the first time that BARHL1 is downregulated in hormone-negative breast cancers and Alzheimer’s disease (AD). Furthermore, using an integrative bioinformatics approach and mining knockout mouse data, we show that: (i) BARHL1 and Estrogen Receptor 1 (ESR1) may constitute a network that regulates Neurotrophin 3 (NTF3)- and Brain Derived Neurotrophic Factor (BDNF)-mediated neurogenesis and neural survival; (ii) this is probably linked to AD pathways affecting aberrant post-translational modifications including SUMOylation and ubiquitination; (iii) the BARHL1-ESR1 network possibly regulates β-amyloid metabolism and memory; and (iv) hsa-mir-18a, having common key targets in the BARHL1-ESR1 network and AD pathway, may modulate neuron death, reduce β-amyloid processing and might also be involved in hearing and cognitive decline associated with AD. We have also hypothesized why estrogen replacement therapy improves AD condition. In addition, we have provided a feasible new mechanism to explain the abnormal function of mossy fibers and cerebellar granule cells related to memory and cognitive decline in AD apart from the Tau and amyloid pathogenesis through our BARHL1-ESR1 axis.

Changes induced by natural scrapie in the calretinin-immunopositive cells and fibres of the sheep cerebellar cortex

Calretinin (CR)-immunopositive cells and fibres in the cerebellar cortex (vermal archicerebellum and neocerebellum) of scrapie-affected, ARQ/ARQ, Rasa Aragonesa breed sheep were studied in comparison with healthy, young and aged, ARQ/ARQ, Rasa Aragonesa animals and with Manchega breed sheep. The scrapie-affected sheep showed signs of both cellular involution and hypertrophic/hyperimmunoreactive responses in all neuronal subtypes; the distribution of the neuronal subtypes in the archi- and neocerebellum, however, did not change compared with controls. The results suggest that the different CR expression and/or CR content of cerebellar cortical neurons in scrapie-affected sheep are more related to their specific functions than any neuroprotective response. The reduction in the cell density of some CR-immunopositive neuronal subsets (i.e. unipolar brush cells) is contradictory to the supposed neuroprotective role of the calcium binding protein CR. However, the hyperimmunoreactivity of many CR-immunopositive neuronal subsets (e.g. the Purkinje cells) suggests the involvement of an over-expression of CR (transitory or restricted to selected neurons) as an adaptative mechanism to fight against the neurodegeneration caused by this prion disease. The changes in the number of immunopositive cells and the hypertrophic/hyperimmunoreactive response seen in scrapie-affected and aged sheep suggests that some different and some similar mechanisms are at work in this disease and aging.

Immunohistochemical increase in cyclooxygenase-2 without apoptosis in different brain areas of subchronic nicotine- and D-amphetamine-treated rats

Cyclooxygenase-2 (COX-2) upregulation has been related to both neurodegeneration and physiological processes. To clarify whether nicotine-induced upregulation of COX-2 occurs, and to analyse its significance, a comparative immunohistochemical and Western blot study was performed on the frontoparietal cortex, hippocampus and cerebellar cortex of rats treated (14 days) with nicotine, D(+)amphetamine (0.35 and 1.16 mg free base/kg/day, respectively), or both drugs simultaneously. None of these treatments promoted neuronal apoptosis. Lipid peroxidation increased in the hippocampus of the nicotine-treated rats and in all the brain regions examined in the D(+)amphetamine rats, but not in the double-treated animals. Both molecules increased the COX-2 content (as determined by the number of immunopositive neurons and the intensity of their immunodeposits) in an area-, layer- and neuron type-dependent manner, in all brain regions in which a large number of COX-2 immunopositive neurons were observed in controls (the somatosensory cortical areas, CA-1, CA-3, the gyrus dentatus, the ectorhinal/perirhinal areas, and the gyrus cingularis). No increase was seen in the motor cortical areas, while a reduction was recorded in the cerebellar cortex; these regions had only a few immunopositive neurons in controls. Western blot analysis revealed a 50-80% increase in COX-2 in the brain cortex and hippocampus of nicotine-treated rats, and similar increases (150-200%) in the cortex of the D(+)amphetamine- and nicotine + D(+)amphetamine-treated rats. Nicotine-induced upregulation of COX-2 seems to be related to neuronal plasticity rather than neurodegeneration. Nicotine agonists might be useful in the treatment of cognitive disorders.

Co-localization and distribution of cerebral APP and SP1 and its relationship to amyloidogenesis

Alzheimer's disease is characterized by amyloid-beta peptide (Abeta)-loaded plaques in the brain. Abeta is a cleavage fragment of amyloid-beta protein precursor (APP) and over production of APP may lead to amyloidogenesis. The regulatory region of the APP gene contains consensus sites recognized by the transcription factor, specificity protein 1 (SP1), which has been shown to be required for the regulation of APP and Abeta. To understand the role of SP1 in APP biogenesis, herein we have characterized the relative distribution and localization of SP1, APP, and Abeta in various brain regions of rodent and primate models using immunohistochemistry. We observed that overall distribution and cellular localization of SP1, APP, and Abeta are similar and neuronal in origin. Their distribution is abundant in various layers of neocortex, but restricted to the Purkinje cell layer of the cerebellum, and the pyramidal cell layer of hippocampus. These findings suggest that overproduction of Abeta in vivo may be associated with transcriptional pathways involving SP1 and the APP gene.

Brain cholinesterases: II. The molecular and cellular basis of Alzheimer's disease

Currently available evidence demonstrates that cholinesterases (ChEs), owing to their powerful enzymatic and non-catalytic actions, unusually strong electrostatics, and exceptionally ubiquitous presence and redundancy in their capacity as the connector, the organizer and the safeguard of the brain, play fundamental role(s) in the well-being of cells, tissues, animal and human lives, while they present themselves adequately in quality and quantity. The widespread intracellular and extracellular membrane networks of ChEs in the brain are also subject to various insults, such as aging, gene anomalies, environmental hazards, head trauma, excessive oxidative stress, imbalances and/or deficits of organic constituents. The loss and the alteration of ChEs on the outer surface membranous network may initiate the formation of extracellular senile plaques and induce an outside-in cascade of Alzheimer's disease (AD). The alteration in ChEs on the intracellular compartments membranous network may give rise to the development of intracellular neurofibrillary tangles and induce an inside-out cascade of AD. The abnormal patterns of glycosylation and configuration changes in ChEs may be reflecting their impaired metabolism at the molecular and cellular level and causing the enzymatic and pharmacodynamical modifications and neurotoxicity detected in brain tissue and/or CSF of patients with AD and in specimens in laboratory experiments. The inflammatory reactions mainly arising from ChEs-containing neuroglial cells may facilitate the pathophysiologic process of AD. It is proposed that brain ChEs may serve as a central point rallying various hypotheses regarding the etio-pathogenesis of AD.