The association of astrogliosis and microglial activation with aging and Alzheimer's disease pathology in the chimpanzee brain

Bearded capuchin monkeys as a model for Alzheimer's disease

The absence of a natural animal model is one of the main challenges in Alzheimer's disease research. Despite the challenges of using nonhuman primates in studies, these animals can bridge mouse models and humans, as nonhuman primates are phylogenetically closer to humans and can spontaneously develop AD-type pathology. The capuchin monkey, a New World primate, has recently attracted attention due to its skill in creating and using instruments. We analyzed one capuchin brain using structural 7 T MRI and performed a neuropathological evaluation of three animals. Alzheimer-type pathology was found in the two of the capuchins. Widespread β-amyloid pathology was observed, mainly in focal deposits with variable morphology and a high density of mature plaques. Notably, plaque-associated dystrophic neurites associated with disruption of axonal transport and early cytoskeletal alteration were frequently found. Unlike in other species of New World monkeys, cerebral arterial angiopathy was not the predominant form of β-amyloid pathology. Additionally, abnormal aggregates of hyperphosphorylated tau, resembling neurofibrillary pathology, were observed in the temporal and frontal cortex. Astrocyte hypertrophy surrounding plaques was found, suggesting a neuroinflammatory response. These findings indicate that aged capuchin monkeys can spontaneously develop Alzheimer-type pathology, indicating that they may be an advantageous animal model for research in Alzheimer's disease.

Depth- and curvature-based quantitative susceptibility mapping analyses of cortical iron in Alzheimer's disease

In addition to amyloid beta plaques and neurofibrillary tangles, Alzheimer's disease (AD) has been associated with elevated iron in deep gray matter nuclei using quantitative susceptibility mapping (QSM). However, only a few studies have examined cortical iron, using more macroscopic approaches that cannot assess layer-specific differences. Here, we conducted column-based QSM analyses to assess whether AD-related increases in cortical iron vary in relation to layer-specific differences in the type and density of neurons. We obtained global and regional measures of positive (iron) and negative (myelin, protein aggregation) susceptibility from 22 adults with AD and 22 demographically matched healthy controls. Depth-wise analyses indicated that global susceptibility increased from the pial surface to the gray/white matter boundary, with a larger slope for positive susceptibility in the left hemisphere for adults with AD than controls. Curvature-based analyses indicated larger global susceptibility for adults with AD versus controls; the right hemisphere versus left; and gyri versus sulci. Region-of-interest analyses identified similar depth- and curvature-specific group differences, especially for temporo-parietal regions. Finding that iron accumulates in a topographically heterogenous manner across the cortical mantle may help explain the profound cognitive deterioration that differentiates AD from the slowing of general motor processes in healthy aging.

Bearded capuchin monkey as a model for Alzheimer's disease research

The absence of a natural animal model is one of the main challenges in Alzheimer's disease research. Despite the challenges of using non-human primates in studies, they can bridge mouse models and humans, as non-human primates are phylogenetically close to humans and can spontaneously develop AD-type pathology. The capuchin monkey, a New World primate, has recently attracted attention due to its skill in creating and using instruments. We analyzed three capuchin brains using structural 7T MRI and neuropathological evaluation. Alzheimer-type pathology was found in one case. Widespread β-amyloid pathology mainly in the form of focal deposits with variable morphology and high density of mature plaques. Noteworthy, plaque-associated dystrophic neurites, associated with disrupted of axonal transport and early cytoskeletal alteration, were frequently found. Unlike other species of New World monkeys, cerebral arterial angiopathy was not the predominant form of β-amyloid pathology. Additionally, abnormal aggregates of hyperphosphorylated tau, resembling neurofibrillary pathology, were observed in the temporal and frontal cortex. Besides, astrocyte hypertrophy surrounding plaques was found, suggesting a neuroinflammatory response. Aged capuchin monkeys can spontaneously develop Alzheimer-type pathology, indicating that they may be an advantageous animal model for research in Alzheimer's disease.

Neuroprotective effects of methylene blue in streptozotocin-induced model of Alzheimer's disease

Methylene blue (MB) can be used as a multidirectional neuroprotector to stop the development of multiple cascades of neuron damage during neurodegenerative processes. This study assesses a protective effect of MB, using an experimental simulation of sporadic Alzheimer's disease by intracerebroventricular administration of streptozotocin (STZ) in rats. It was found that a STZ-induced impairment of memory can be partially mitigated with intravenous injections of MB after the administration of STZ. The treatment of animals with MB prevented the STZ-induced increase in the number and density of microglial and GFAP-positive cells in the brain cortex. In addition, it was shown that the expression of the LC3B protein, an indicator of autophagy, increases in the hippocampus of animals treated with STZ. In the hippocampus of animals treated with MB, an increase in the expression of the LC3B protein was prevented. Using the Griess reaction assay and immunocytochemical study was found that MB reduces lipopolysaccharide-induced NO-production and the expression of iNOS in cultured neurons. In conclusion, our data demonstrate that MB has neuroprotective and anti-inflammatory effects and is able to prevent autophagy. These effects have important therapeutic implications, so MB could potentially play a role in the treatment of neurodegenerative processes.