Activated microglial cells are an integral component of fibrillar plaques in brains of subjects w... more Activated microglial cells are an integral component of fibrillar plaques in brains of subjects with Alzheimer's disease (AD) and in brains of transgenic mice overexpressing amyloidogenic fragments of human amyloid precursor protein (APP). The aim of this ultrastructural study of fibrillar plaques was to characterize the origin of microglial cells involved in cored plaque formation. Computer-aided three-dimensional reconstruction of plaques and microvessels in APPsw transgenic mice shows perivascular development of cored plaques. Perivascular location of almost all examined plaques and the infiltration at the interface between vessels and plaques with cells of monocyte/microglia lineage indicates that plaques are formed by inflammatory cells of blood origin. The increase in the number of microglial cells from 1 or 2 in an early plaque to more than 100 in a several-month-old plaque does not result in plaque degradation, but is associated with amyloid core growth and progression of neuronal degeneration, and suggests that recruitment of inflammatory cells of blood origin sustains plaque growth. Infiltration of the plaque with cells of blood origin and degeneration of 10-46% of inflammatory cells in large plaques, which is especially frequent at the interface between capillary wall and plaque, suggest their accelerated turnover.
Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followe... more Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followed by progressively worsening ataxia, hind limb paresis, episodes of immobility, and seizures by 5 to 14 weeks. Gross lesions were not observed at necropsy in rats euthanized and perfused at 4 to 16 weeks of age. Neurohistologic examination revealed dysmyelination in the central nervous system. Astrogliosis in the white matter with marked increase of expression of the glial fibrillary acid protein marker was accompanied by diffuse microgliosis. Scattered glial cells, interpreted to be oligodendrocytes, contained minute periodic acid-Schiff-positive cytoplasmic granules. Large mineralized periodic acid-Schiff-positive and laminated structures were observed in the cerebellar white matter, midbrain, and thalamus of rats over 6 weeks old. Neuronal degeneration and loss was evident in the cortex, hippocampus, and midbrain. Large axonal spheroids were found in the ventral and lateral funiculi of the spinal cord. An ultrastructural study of four affected rats revealed an almost complete absence of myelinated axons and normal sheaths, and degeneration and necrosis of oligodendrocytes. The Long Evans shaker rat represents a novel myelin mutant with a remarkable survival period and appears to have an autosomal recessive mode of inheritance.
Journal of neuropathology and experimental neurology, 2005
The accumulation of lysosomes and their hydrolases within neurons is a well-established neuropath... more The accumulation of lysosomes and their hydrolases within neurons is a well-established neuropathologic feature of Alzheimer disease (AD). Here we show that lysosomal pathology in AD brain involves extensive alterations of macroautophagy, an inducible pathway for the turnover of intracellular constituents, including organelles. Using immunogold labeling with compartmental markers and electron microscopy on neocortical biopsies from AD brain, we unequivocally identified autophagosomes and other prelysosomal autophagic vacuoles (AVs), which were morphologically and biochemically similar to AVs highly purified from mouse liver. AVs were uncommon in brains devoid of AD pathology but were abundant in AD brains particularly, within neuritic processes, including synaptic terminals. In dystrophic neurites, autophagosomes, multivesicular bodies, multilamellar bodies, and cathepsin-containing autophagolysosomes were the predominant organelles and accumulated in large numbers. These compartmen...
Liver disease is characterized by fatty liver, hepatitis, fibrosis and cirrhosis and is a major c... more Liver disease is characterized by fatty liver, hepatitis, fibrosis and cirrhosis and is a major cause of illness and death worldwide. The prevalence of liver diseases highlights the need for animal models for research on the mechanism of disease pathogenesis and efficient and cost-effective treatments. Here we show that a senescence-accelerated mouse strain (SAMP8 mice), displays severe liver pathology, which is not seen in senescence-resistant mice (SAMR1). The livers of SAMP8 mice show fatty degeneration, hepatocyte death, fibrosis, cirrhotic changes, inflammatory mononuclear cell infiltration and sporadic neoplastic changes. SAMP8 mice also show abnormal liver function tests: significantly increased levels of alanine amino-transferase (ALT) and aspartate aminotransferase (AST). Furthermore, titers of murine leukemia virus are higher in livers of SAMP8 than in those of SAMR1 mice. Our observations suggest that SAMP8 mouse strain is a valuable animal model for the study of liver di...
Microtubule-associated protein tau in a hyperphosphorylated state is the major component of the f... more Microtubule-associated protein tau in a hyperphosphorylated state is the major component of the filamentous lesions that define a number of neurodegenerative diseases commonly referred to as tauopathies. Hyperphosphorylation of tau at most sites appears to precede filament assembly. Many of the hyperphosphorylated sites are serine/threonine-proline sequences. Here we show that c-Jun N-terminal kinases JNK1, JNK2 and JNK3 phosphorylate tau at many serine/threonine-prolines, as assessed by the generation of the epitopes of phosphorylation-dependent anti-tau antibodies. Of the three protein kinases, JNK2 phosphorylated the most sites in tau, followed by JNK3 and JNK1. Phosphorylation by JNK isoforms resulted in a greatly reduced ability of tau to promote microtubule assembly. These findings extend the number of candidate protein kinases for the hyperphosphorylation of tau in Alzheimer's disease and other neurodegenerative disorders.
THE majority of early-onset familial Alzheimer's disease (FAD) is associated with mutations in th... more THE majority of early-onset familial Alzheimer's disease (FAD) is associated with mutations in the presenilin-1 (PS1) gene. We describe a novel Polish PS1 mutation of Pro117Leu, associated with the earliest average age of onset and death so far reported in a PS-linked, FAD kindred. Human kidney 293 and mouse neuroblastoma N2a cells were stably transfected with wild-type and PS1 P117L. There was a significant increase in the amyloid 42/40 ratio in the N2a P117L PS1 transfected cells compared with N2a transfected with wild-type PS1. What role PS has in the pathogenesis of AD remains to be determined, however, the severity of the clinical picture associated with this PS1 mutation stresses the importance of presenilin.
Activated microglial cells are an integral component of fibrillar plaques in brains of subjects w... more Activated microglial cells are an integral component of fibrillar plaques in brains of subjects with Alzheimer's disease (AD) and in brains of transgenic mice overexpressing amyloidogenic fragments of human amyloid precursor protein (APP). The aim of this ultrastructural study of fibrillar plaques was to characterize the origin of microglial cells involved in cored plaque formation. Computer-aided three-dimensional reconstruction of plaques and microvessels in APPsw transgenic mice shows perivascular development of cored plaques. Perivascular location of almost all examined plaques and the infiltration at the interface between vessels and plaques with cells of monocyte/microglia lineage indicates that plaques are formed by inflammatory cells of blood origin. The increase in the number of microglial cells from 1 or 2 in an early plaque to more than 100 in a several-month-old plaque does not result in plaque degradation, but is associated with amyloid core growth and progression of neuronal degeneration, and suggests that recruitment of inflammatory cells of blood origin sustains plaque growth. Infiltration of the plaque with cells of blood origin and degeneration of 10-46% of inflammatory cells in large plaques, which is especially frequent at the interface between capillary wall and plaque, suggest their accelerated turnover.
Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the ne... more Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the neurodegeneration of Alzheimer's disease (AD). The basis for the profuse accumulation of autophagic vacuoles (AVs) in affected neurons of the AD brain, however, is unknown. In this study, we show that constitutive macroautophagy in primary cortical neurons is highly efficient, because newly formed autophagosomes are rapidly cleared by fusion with lysosomes, accounting for their scarcity in the healthy brain. Even after macroautophagy is strongly induced by suppressing mTOR (mammalian target of rapamycin) kinase activity with rapamycin or nutrient deprivation, active cathepsin-positive autolysosomes rather than LC3-II-positive autophagosomes predominate, implying efficient autophagosome clearance in healthy neurons. In contrast, selectively impeding late steps in macroautophagy by inhibiting cathepsin-mediated proteolysis within autolysosomes with cysteine-and aspartyl-protease inhibitors caused a marked accumulation of electron-dense double-membrane-limited AVs, containing cathepsin D and incompletely degraded LC3-II in perikarya and neurites. Similar structures accumulated in large numbers when fusion of autophagosomes with lysosomes was slowed by disrupting their transport on microtubules with vinblastine. Finally, we find that the autophagic vacuoles accumulating after protease inhibition or prolonged vinblastine treatment strongly resembled AVs that collect in dystrophic neurites in the AD brain and in an AD mouse model. We conclude that macroautophagy is constitutively active and highly efficient in healthy neurons and that the autophagic pathology observed in AD most likely arises from impaired clearance of AVs rather than strong autophagy induction alone. Therapeutic modulation of autophagy in AD may, therefore, require targeting late steps in the autophagic pathway.
Amyloid plaques appear early during Alzheimer's disease (AD), and their development is intimately... more Amyloid plaques appear early during Alzheimer's disease (AD), and their development is intimately linked to activated astrocytes and microglia. Astrocytes are capable of accumulating substantial amounts of neuron-derived, amyloid (1-42) (A42)-positive material and other neuron-specific proteins as a consequence of their debris-clearing role in response to local neurodegeneration. Immunohistochemical analyses have suggested that astrocytes overburdened with these internalized materials can eventually undergo lysis, and radial dispersal of their cytoplasmic contents, including A42, can lead to the deposition of a persistent residue in the form of small, GFAP-rich, astrocytic amyloid plaques, first appearing in the molecular layer of the cerebral cortex. Microglia, most of which appear to be derived from blood monocytes and recruited from local blood vessels, rapidly migrate into and congregate within neuritic and dense-core plaques, but not diffuse plaques. Instead of internalizing and removing A from plaques, microglia appear to contribute to their morphological and chemical evolution by facilitating the conversion of existing soluble and oligomeric A within plaques to the fibrillar form. A fibrillogenesis may occur largely within tiny, tube-like invaginations in the surface plasma membrane of microglia. These results highlight the therapeutic potential of blocking the initial intracellular accumulation of A42 in neurons and astrocytes and inhibiting microglia-mediated assembly of fibrillar A, which is particularly resistant to degradation in Alzheimer brain.
Activated microglial cells are an integral component of fibrillar plaques in brains of subjects w... more Activated microglial cells are an integral component of fibrillar plaques in brains of subjects with Alzheimer's disease (AD) and in brains of transgenic mice overexpressing amyloidogenic fragments of human amyloid precursor protein (APP). The aim of this ultrastructural study of fibrillar plaques was to characterize the origin of microglial cells involved in cored plaque formation. Computer-aided three-dimensional reconstruction of plaques and microvessels in APPsw transgenic mice shows perivascular development of cored plaques. Perivascular location of almost all examined plaques and the infiltration at the interface between vessels and plaques with cells of monocyte/microglia lineage indicates that plaques are formed by inflammatory cells of blood origin. The increase in the number of microglial cells from 1 or 2 in an early plaque to more than 100 in a several-month-old plaque does not result in plaque degradation, but is associated with amyloid core growth and progression of neuronal degeneration, and suggests that recruitment of inflammatory cells of blood origin sustains plaque growth. Infiltration of the plaque with cells of blood origin and degeneration of 10-46% of inflammatory cells in large plaques, which is especially frequent at the interface between capillary wall and plaque, suggest their accelerated turnover.
Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followe... more Tremors were observed in 15 Long Evans rats beginning at 10 to 12 days of age. These were followed by progressively worsening ataxia, hind limb paresis, episodes of immobility, and seizures by 5 to 14 weeks. Gross lesions were not observed at necropsy in rats euthanized and perfused at 4 to 16 weeks of age. Neurohistologic examination revealed dysmyelination in the central nervous system. Astrogliosis in the white matter with marked increase of expression of the glial fibrillary acid protein marker was accompanied by diffuse microgliosis. Scattered glial cells, interpreted to be oligodendrocytes, contained minute periodic acid-Schiff-positive cytoplasmic granules. Large mineralized periodic acid-Schiff-positive and laminated structures were observed in the cerebellar white matter, midbrain, and thalamus of rats over 6 weeks old. Neuronal degeneration and loss was evident in the cortex, hippocampus, and midbrain. Large axonal spheroids were found in the ventral and lateral funiculi of the spinal cord. An ultrastructural study of four affected rats revealed an almost complete absence of myelinated axons and normal sheaths, and degeneration and necrosis of oligodendrocytes. The Long Evans shaker rat represents a novel myelin mutant with a remarkable survival period and appears to have an autosomal recessive mode of inheritance.
Journal of neuropathology and experimental neurology, 2005
The accumulation of lysosomes and their hydrolases within neurons is a well-established neuropath... more The accumulation of lysosomes and their hydrolases within neurons is a well-established neuropathologic feature of Alzheimer disease (AD). Here we show that lysosomal pathology in AD brain involves extensive alterations of macroautophagy, an inducible pathway for the turnover of intracellular constituents, including organelles. Using immunogold labeling with compartmental markers and electron microscopy on neocortical biopsies from AD brain, we unequivocally identified autophagosomes and other prelysosomal autophagic vacuoles (AVs), which were morphologically and biochemically similar to AVs highly purified from mouse liver. AVs were uncommon in brains devoid of AD pathology but were abundant in AD brains particularly, within neuritic processes, including synaptic terminals. In dystrophic neurites, autophagosomes, multivesicular bodies, multilamellar bodies, and cathepsin-containing autophagolysosomes were the predominant organelles and accumulated in large numbers. These compartmen...
Liver disease is characterized by fatty liver, hepatitis, fibrosis and cirrhosis and is a major c... more Liver disease is characterized by fatty liver, hepatitis, fibrosis and cirrhosis and is a major cause of illness and death worldwide. The prevalence of liver diseases highlights the need for animal models for research on the mechanism of disease pathogenesis and efficient and cost-effective treatments. Here we show that a senescence-accelerated mouse strain (SAMP8 mice), displays severe liver pathology, which is not seen in senescence-resistant mice (SAMR1). The livers of SAMP8 mice show fatty degeneration, hepatocyte death, fibrosis, cirrhotic changes, inflammatory mononuclear cell infiltration and sporadic neoplastic changes. SAMP8 mice also show abnormal liver function tests: significantly increased levels of alanine amino-transferase (ALT) and aspartate aminotransferase (AST). Furthermore, titers of murine leukemia virus are higher in livers of SAMP8 than in those of SAMR1 mice. Our observations suggest that SAMP8 mouse strain is a valuable animal model for the study of liver di...
Microtubule-associated protein tau in a hyperphosphorylated state is the major component of the f... more Microtubule-associated protein tau in a hyperphosphorylated state is the major component of the filamentous lesions that define a number of neurodegenerative diseases commonly referred to as tauopathies. Hyperphosphorylation of tau at most sites appears to precede filament assembly. Many of the hyperphosphorylated sites are serine/threonine-proline sequences. Here we show that c-Jun N-terminal kinases JNK1, JNK2 and JNK3 phosphorylate tau at many serine/threonine-prolines, as assessed by the generation of the epitopes of phosphorylation-dependent anti-tau antibodies. Of the three protein kinases, JNK2 phosphorylated the most sites in tau, followed by JNK3 and JNK1. Phosphorylation by JNK isoforms resulted in a greatly reduced ability of tau to promote microtubule assembly. These findings extend the number of candidate protein kinases for the hyperphosphorylation of tau in Alzheimer's disease and other neurodegenerative disorders.
THE majority of early-onset familial Alzheimer's disease (FAD) is associated with mutations in th... more THE majority of early-onset familial Alzheimer's disease (FAD) is associated with mutations in the presenilin-1 (PS1) gene. We describe a novel Polish PS1 mutation of Pro117Leu, associated with the earliest average age of onset and death so far reported in a PS-linked, FAD kindred. Human kidney 293 and mouse neuroblastoma N2a cells were stably transfected with wild-type and PS1 P117L. There was a significant increase in the amyloid 42/40 ratio in the N2a P117L PS1 transfected cells compared with N2a transfected with wild-type PS1. What role PS has in the pathogenesis of AD remains to be determined, however, the severity of the clinical picture associated with this PS1 mutation stresses the importance of presenilin.
Activated microglial cells are an integral component of fibrillar plaques in brains of subjects w... more Activated microglial cells are an integral component of fibrillar plaques in brains of subjects with Alzheimer's disease (AD) and in brains of transgenic mice overexpressing amyloidogenic fragments of human amyloid precursor protein (APP). The aim of this ultrastructural study of fibrillar plaques was to characterize the origin of microglial cells involved in cored plaque formation. Computer-aided three-dimensional reconstruction of plaques and microvessels in APPsw transgenic mice shows perivascular development of cored plaques. Perivascular location of almost all examined plaques and the infiltration at the interface between vessels and plaques with cells of monocyte/microglia lineage indicates that plaques are formed by inflammatory cells of blood origin. The increase in the number of microglial cells from 1 or 2 in an early plaque to more than 100 in a several-month-old plaque does not result in plaque degradation, but is associated with amyloid core growth and progression of neuronal degeneration, and suggests that recruitment of inflammatory cells of blood origin sustains plaque growth. Infiltration of the plaque with cells of blood origin and degeneration of 10-46% of inflammatory cells in large plaques, which is especially frequent at the interface between capillary wall and plaque, suggest their accelerated turnover.
Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the ne... more Macroautophagy, a major pathway for organelle and protein turnover, has been implicated in the neurodegeneration of Alzheimer's disease (AD). The basis for the profuse accumulation of autophagic vacuoles (AVs) in affected neurons of the AD brain, however, is unknown. In this study, we show that constitutive macroautophagy in primary cortical neurons is highly efficient, because newly formed autophagosomes are rapidly cleared by fusion with lysosomes, accounting for their scarcity in the healthy brain. Even after macroautophagy is strongly induced by suppressing mTOR (mammalian target of rapamycin) kinase activity with rapamycin or nutrient deprivation, active cathepsin-positive autolysosomes rather than LC3-II-positive autophagosomes predominate, implying efficient autophagosome clearance in healthy neurons. In contrast, selectively impeding late steps in macroautophagy by inhibiting cathepsin-mediated proteolysis within autolysosomes with cysteine-and aspartyl-protease inhibitors caused a marked accumulation of electron-dense double-membrane-limited AVs, containing cathepsin D and incompletely degraded LC3-II in perikarya and neurites. Similar structures accumulated in large numbers when fusion of autophagosomes with lysosomes was slowed by disrupting their transport on microtubules with vinblastine. Finally, we find that the autophagic vacuoles accumulating after protease inhibition or prolonged vinblastine treatment strongly resembled AVs that collect in dystrophic neurites in the AD brain and in an AD mouse model. We conclude that macroautophagy is constitutively active and highly efficient in healthy neurons and that the autophagic pathology observed in AD most likely arises from impaired clearance of AVs rather than strong autophagy induction alone. Therapeutic modulation of autophagy in AD may, therefore, require targeting late steps in the autophagic pathway.
Amyloid plaques appear early during Alzheimer's disease (AD), and their development is intimately... more Amyloid plaques appear early during Alzheimer's disease (AD), and their development is intimately linked to activated astrocytes and microglia. Astrocytes are capable of accumulating substantial amounts of neuron-derived, amyloid (1-42) (A42)-positive material and other neuron-specific proteins as a consequence of their debris-clearing role in response to local neurodegeneration. Immunohistochemical analyses have suggested that astrocytes overburdened with these internalized materials can eventually undergo lysis, and radial dispersal of their cytoplasmic contents, including A42, can lead to the deposition of a persistent residue in the form of small, GFAP-rich, astrocytic amyloid plaques, first appearing in the molecular layer of the cerebral cortex. Microglia, most of which appear to be derived from blood monocytes and recruited from local blood vessels, rapidly migrate into and congregate within neuritic and dense-core plaques, but not diffuse plaques. Instead of internalizing and removing A from plaques, microglia appear to contribute to their morphological and chemical evolution by facilitating the conversion of existing soluble and oligomeric A within plaques to the fibrillar form. A fibrillogenesis may occur largely within tiny, tube-like invaginations in the surface plasma membrane of microglia. These results highlight the therapeutic potential of blocking the initial intracellular accumulation of A42 in neurons and astrocytes and inhibiting microglia-mediated assembly of fibrillar A, which is particularly resistant to degradation in Alzheimer brain.
Autism causes neuropathological changes in varied anatomical loci. A coherent neural mechanism to... more Autism causes neuropathological changes in varied anatomical loci. A coherent neural mechanism to explain the spectrum of autistic symptomatology has not been proposed because most anatomical researchers focus on point-to-point functional neural systems (e.g., auditory and social networks) rather than considering global chemical neural systems. Serotonergic neurons have a global innervation pattern. Disorders Research Program, AS073234, Program Project (JW). Their cell bodies are found in the midbrain but they project their axons throughout the neural axis beginning in the fetal brain. This global system is implicated in autism by animal models and by biochemical, imaging, pharmacological, and genetics studies. However, no anatomical studies of the 5-HT innervation of autistic donors have been reported. Our review presents immunocytochemical evidence of an increase in 5-HT axons in postmortem brain tissue from autism donors aged 2.8-29 years relative to controls. This increase is observed in the principle ascending fiber bundles of the medial and lateral forebrain bundles, and in the innervation density of the amygdala and the piriform, superior temporal, and parahippocampal cortices. In autistic donors 8 years of age and up, several types of dystrophic 5-HT axons were seen in the termination fields. One class of these dystrophic axons, the thick heavily stained axons, was not seen in the brains of patients with neurodegenerative diseases. These findings provide morphological evidence for the involvement of serotonin neurons in the early etiology of autism, and suggest new therapies may be effective to blunt serotonin's trophic actions during early brain development in children.
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Papers by Jerzy Wegiel