Unexpected Classes of Aquaporin Channels Detected by Transcriptomic Analysis in Human Brain Are Associated with Both Patient Age and Alzheimer’s Disease Status

Dysregulation of astrocytic Aquaporin-1 in the brains of oldest-old rhesus macaques: the NIA caloric restriction study

Aquaporin-1 (AQP1) is a highly conserved water-channel protein, found to be expressed by astrocytes in adult humans and non-human primates (NHPs). Upregulation of cortical AQP1 expression occurs with cancer, injury, and neurodegenerative disease, but minimal information is available about the effects of normative aging on AQP1 expression. This study leverages tissues from the oldest-old rhesus macaques, some greater than 40 years of age, from the National Institute on Aging longitudinal study of caloric restriction (CR). We tested whether AQP1 levels are altered in the NHP brain as a function of diet group, sex, and age. Sections of formaldehyde-fixed prefrontal (PFC) and temporal (TC) cortices from 36 rhesus macaques (both sexes, 22 to 44 years, + / - CR) were immunochemically stained for AQP1, then the percent area of AQP1 staining was regionally measured using ImageJ free-ware. Results showed age-related regional increases of AQP1 expression, with no effect of diet group or sex. Specifically, in the PFC, AQP1 positively-stained area increased with age in multiple subregions. For the TC subregions, AQP1 area coverage was not affected by age, despite having average levels that were greater than in the PFC. The peak expression of AQP1 in astrocytes appeared in clusters across cortical layers in a subgroup of animals 30 + years old. Astrocytic AQP1 dysregulation may contribute to progressive risk of neuropathology with aging.

A Map of Transcriptomic Signatures of Different Brain Areas in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder that progressively involves brain regions with an often-predictable pattern. Damage to the brain appears to spread and worsen with time, but the molecular mechanisms underlying the region-specific distribution of AD pathology at different stages of the disease are still under-investigated. In this study, a whole-transcriptome analysis was carried out on brain samples from the hippocampus (HI), temporal and parietal cortices (TC and PC, respectively), cingulate cortex (CG), and substantia nigra (SN) of six subjects with a definite AD diagnosis and three healthy age-matched controls in duplicate. The transcriptomic results showed a greater number of differentially expressed genes (DEGs) in the TC (1571) and CG (1210) and a smaller number of DEGs in the HI (206), PC (109), and SN (60). Furthermore, the GSEA showed a difference between the group of brain areas affected early (HI and TC) and the group of areas that were subsequently involved (PC, CG, and SN). Notably, in the HI and TC, there was a significant downregulation of shared DEGs primarily involved in synaptic transmission, while in the PC, CG, and SN, there was a significant downregulation of genes primarily involved in protein folding and trafficking. The course of AD could follow a definite time- and severity-related pattern that arises from protein misfolding, as observed in the PC, CG, and SN, and leads to synaptic impairment, as observed in the HI and TC. Therefore, a map of the molecular and biological processes involved in AD pathogenesis may be traced. This could aid in the discovery of novel biological targets in order to develop effective and well-timed therapeutic approaches.

Aquaporins: Gatekeepers of Fluid Dynamics in Traumatic Brain Injury

Aquaporins (AQPs), particularly AQP4, play a crucial role in regulating fluid dynamics in the brain, impacting the development and resolution of edema following traumatic brain injury (TBI). This review examines the alterations in AQP expression and localization post-injury, exploring their effects on brain edema and overall injury outcomes. We discuss the underlying molecular mechanisms regulating AQP expression, highlighting potential therapeutic strategies to modulate AQP function. These insights provide a comprehensive understanding of AQPs in TBI and suggest novel approaches for improving clinical outcomes through targeted interventions.

Animal and Cellular Models of Alzheimer's Disease

Animal and cellular models have been essential tools over the years to understand many pathogenic mechanisms underlying different neurodegenerative disorders (NDDs), including Alzheimer's disease (AD) [...].

Neuroprotective Strategies and Cell-Based Biomarkers for Manganese-Induced Toxicity in Human Neuroblastoma (SH-SY5Y) Cells

Manganese (Mn) is an essential heavy metal in the human body, while excess Mn leads to neurotoxicity, as observed in this study, where 100 µM of Mn was administered to the human neuroblastoma (SH-SY5Y) cell model of dopaminergic neurons in neurodegenerative diseases. We quantitated pathway and gene changes in homeostatic cell-based adaptations to Mn exposure. Utilizing the Gene Expression Omnibus, we accessed the GSE70845 dataset as a microarray of SH-SY5Y cells published by Gandhi et al. (2018) and applied statistical significance cutoffs at p < 0.05. We report 74 pathway and 10 gene changes with statistical significance. ReactomeGSA analyses demonstrated upregulation of histones (5 out of 10 induced genes) and histone deacetylases as a neuroprotective response to remodel/mitigate Mn-induced DNA/chromatin damage. Neurodegenerative-associated pathway changes occurred. NF-κB signaled protective responses via Sirtuin-1 to reduce neuroinflammation. Critically, Mn activated three pathways implicating deficits in purine metabolism. Therefore, we validated that urate, a purine and antioxidant, mitigated Mn-losses of viability in SH-SY5Y cells. We discuss Mn as a hypoxia mimetic and trans-activator of HIF-1α, the central trans-activator of vascular hypoxic mitochondrial dysfunction. Mn induced a 3-fold increase in mRNA levels for antioxidant metallothionein-III, which was induced 100-fold by hypoxia mimetics deferoxamine and zinc.

Protective roles of peroxiporins AQP0 and AQP11 in human astrocyte and neuronal cell lines in response to oxidative and inflammatory stressors

In addition to aquaporin (AQP) classes AQP1, AQP4 and AQP9 known to be expressed in mammalian brain, our recent transcriptomic analyses identified AQP0 and AQP11 in human cortex and hippocampus at levels correlated with age and Alzheimer's disease (AD) status; however, protein localization remained unknown. Roles of AQP0 and AQP11 in transporting hydrogen peroxide (H2O2) in lens and kidney prompted our hypothesis that up-regulation in brain might similarly be protective. Established cell lines for astroglia (1321N1) and neurons (SHSY5Y, differentiated with retinoic acid) were used to monitor changes in transcript levels for human AQPs (AQP0 to AQP12) in response to inflammation (simulated with 10-100 ng/ml lipopolysaccharide [LPS], 24 h), and hypoxia (5 min N2, followed by 0 to 24 h normoxia). AQP transcripts up-regulated in both 1321N1 and SHSY5Y included AQP0, AQP1 and AQP11. Immunocytochemistry in 1321N1 cells confirmed protein expression for AQP0 and AQP11 in plasma membrane and endoplasmic reticulum; AQP11 increased 10-fold after LPS and AQP0 increased 0.3-fold. In SHSY5Y cells, AQP0 expression increased 0.2-fold after 24 h LPS; AQP11 showed no appreciable change. Proposed peroxiporin roles were tested using melondialdehyde (MDA) assays to quantify lipid peroxidation levels after brief H2O2. Boosting peroxiporin expression by LPS pretreatment lowered subsequent H2O2-induced MDA responses (∼50%) compared with controls; conversely small interfering RNA knockdown of AQP0 in 1321N1 increased lipid peroxidation (∼17%) after H2O2, with a similar trend for AQP11 siRNA. Interventions that increase native brain peroxiporin activity are promising as new approaches to mitigate damage caused by aging and neurodegeneration.

Neuropathological and sociodemographic factors associated with the cortical amyloid load in aging and Alzheimer's disease

Alzheimer's disease (AD) is the leading cause of dementia and is characterized by a progressive decline in cognitive abilities. A pathological hallmark of AD is a region-specific accumulation of the amyloid-beta protein (Aβ). Here, we explored the association between regional Aβ deposition, sociodemographic, and local biochemical factors. We quantified the Aβ burden in postmortem cortical samples from parietal (PCx) and temporal (TCx) regions of 27 cognitively unimpaired (CU) and 15 AD donors, aged 78-100 + years. Histological images of Aβ immunohistochemistry and local concentrations of pathological and inflammatory proteins were obtained at the "Aging, Dementia and TBI Study" open database. We used the area fraction fractionator stereological methodology to quantify the Aβ burden in the gray and white matter within each cortical region. We found higher Aβ burdens in the TCx of AD octogenarians compared to CU ones. We also found higher Aβ loads in the PCx of AD nonagenarians than in AD octogenarians. Moreover, AD women exhibited increased Aβ deposition compared to CU women. Interestingly, we observed a negative correlation between education years and Aβ burden in the white matter of both cortices in CU samples. In AD brains, the Aβ40, Aβ42, and pTau181 isoforms of Aβ and Tau proteins were positively correlated with the Aβ burden. Additionally, in the TCx of AD donors, the proinflammatory cytokine TNFα showed a positive correlation with the Aβ load. These novel findings contribute to understanding the interplay between sociodemographic characteristics, local inflammatory signaling, and the development of AD-related pathology in the cerebral cortex.