Oxidation of KCNB1 potassium channels in the murine brain during aging is associated with cognitive impairment

Sympathetic Motor Neuron Dysfunction is a Missing Link in Age-Associated Sympathetic Overactivity

Overactivity of the sympathetic nervous system is a hallmark of aging. The cellular mechanisms behind this overactivity remain poorly understood, with most attention paid to likely central nervous system components. In this work, we hypothesized that aging also affects the function of motor neurons in the peripheral sympathetic ganglia. To test this hypothesis, we compared the electrophysiological responses and ion-channel activity of neurons isolated from the superior cervical ganglia of young (12 weeks), middle-aged (64 weeks), and old (115 weeks) mice. These approaches showed that aging does impact the intrinsic properties of sympathetic motor neurons, increasing spontaneous and evoked firing responses. A reduction of M current emerged as a major contributor to age-related hyperexcitability. Thus, it is essential to consider the effect of aging on motor components of the sympathetic reflex as a crucial part of the mechanism involved in sympathetic overactivity.

STAMarker: determining spatial domain-specific variable genes with saliency maps in deep learning

Spatial transcriptomics characterizes gene expression profiles while retaining the information of the spatial context, providing an unprecedented opportunity to understand cellular systems. One of the essential tasks in such data analysis is to determine spatially variable genes (SVGs), which demonstrate spatial expression patterns. Existing methods only consider genes individually and fail to model the inter-dependence of genes. To this end, we present an analytic tool STAMarker for robustly determining spatial domain-specific SVGs with saliency maps in deep learning. STAMarker is a three-stage ensemble framework consisting of graph-attention autoencoders, multilayer perceptron (MLP) classifiers, and saliency map computation by the backpropagated gradient. We illustrate the effectiveness of STAMarker and compare it with serveral commonly used competing methods on various spatial transcriptomic data generated by different platforms. STAMarker considers all genes at once and is more robust when the dataset is very sparse. STAMarker could identify spatial domain-specific SVGs for characterizing spatial domains and enable in-depth analysis of the region of interest in the tissue section.

Inflammaging and Osteoarthritis

Osteoarthritis is a highly prevalent disease particularly in subjects over 65 years of age worldwide. While in the past it was considered a mere consequence of cartilage degradation leading to anatomical and functional joint impairment, in recent decades, there has been a more dynamic view with the synovium, the cartilage, and the subchondral bone producing inflammatory mediators which ultimately lead to cartilage damage. Inflammaging is defined as a chronic, sterile, low-grade inflammation state driven by endogenous signals in the absence of infections, occurring with aging. This chronic status is linked to the production of reactive oxygen species and molecules involved in the development of age-related disease such as cancer, diabetes, and cardiovascular and neurodegenerative diseases. Inflammaging contributes to osteoarthritis development where both the innate and the adaptive immune response are involved. Elevated systemic and local inflammatory cytokines and senescent molecules promote cartilage degradation, and antigens derived from damaged joints further trigger inflammation through inflammasome activation. B and T lymphocyte populations also change with inflammaging and OA, with reduced regulatory functions, thus implicating self-reactivity as an additional mechanism of joint damage. The discovery of the underlying pathogenic pathways may help to identify potential therapeutic targets for the management or the prevention of osteoarthritis. We will provide a comprehensive evaluation of the current literature on the role of inflammaging in osteoarthritis and discuss the emerging therapeutic strategies.

Age-related changes in Kv4/Shal and Kv1/Shaker expression in Drosophila and a role for reactive oxygen species

Age-related changes in ion channel expression are likely to affect neuronal signaling. Here, we examine how age affects Kv4/Shal and Kv1/Shaker K+ channel protein levels in Drosophila. We show that Kv4/Shal protein levels decline sharply from 3 days to 10 days, then more gradually from 10 to 40 days after eclosion. In contrast, Kv1/Shaker protein exhibits a transient increase at 10 days that then stabilizes and eventually declines at 40 days. We present data that begin to show a relationship between reactive oxygen species (ROS), Kv4/Shal, and locomotor performance. We show that Kv4/Shal levels are negatively affected by ROS, and that over-expression of Catalase or RNAi knock-down of the ROS-generating enzyme, Nicotinamide Adenine Dinucleotide Phosphate (NADPH) Oxidase (NOX), can attenuate the loss of Kv4/Shal protein. Finally, we compare levels of Kv4.2 and Kv4.3 in the hippocampus, olfactory bulb, cerebellum, and motor cortex of mice aged 6 weeks and 1 year. While there was no global decline in Kv4.2/4.3 that parallels what we report in Drosophila, we did find that Kv4.2/4.3 are differentially affected in various brain regions; this survey of changes may help inform mammalian studies that examine neuronal function with age.

Dopamine-Dependent QR2 Pathway Activation in CA1 Interneurons Enhances Novel Memory Formation

The formation of memory for a novel experience is a critical cognitive capacity. The ability to form novel memories is sensitive to age-related pathologies and disease, to which prolonged metabolic stress is a major contributing factor. Presently, we describe a dopamine-dependent redox modulation pathway within the hippocampus of male mice that promotes memory consolidation. Namely, following novel information acquisition, quinone reductase 2 (QR2) is suppressed by miRNA-182 (miR-182) in the CA1 region of the hippocampus via dopamine D1 receptor (D1R) activation, a process largely facilitated by locus coeruleus activity. This pathway activation reduces ROS generated by QR2 enzymatic activity, a process that alters the intrinsic properties of CA1 interneurons 3 h following learning, in a form of oxidative eustress. Interestingly, novel experience decreases QR2 expression predominately in inhibitory interneurons. Additionally, we find that in aged animals this newly described QR2 pathway is chronically under activated, resulting in miR-182 underexpression and QR2 overexpression. This leads to accumulative oxidative stress, which can be seen in CA1 via increased levels of oxidized, inactivated potassium channel Kv2.1, which undergoes disulfide bridge oligomerization. This newly described interneuron-specific molecular pathway lies alongside the known mRNA translation-dependent processes necessary for long-term memory formation, entrained by dopamine in CA1. It is a process crucial for the distinguishing features of novel memory, and points to a promising new target for memory enhancement in aging and age-dependent diseases.SIGNIFICANCE STATEMENT One way in which evolution dictates which sensory information will stabilize as an internal representation, relies on information novelty. Dopamine is a central neuromodulator involved in this process in the mammalian hippocampus. Here, we describe for the first time a dopamine D1 receptor-dependent quinone reductase 2 pathway in interneurons. This is a targeted redox event necessary to delineate a novel experience to a robust long-term internal representation. Activation of this pathway alone can explain the effect novelty has on "flashbulb" memories, and it can become dysfunctional with age and diseases, such as Alzheimer's disease.

Identification of the potential biomarkers in patients with glioma: a weighted gene co-expression network analysis

Glioma is the most common brain tumor with high mortality. However, there are still challenges for the timely and accurate diagnosis and effective treatment of the tumor. One hundred and twenty-one samples with grades II, III and IV from the Gene Expression Omnibus database were used to construct gene co-expression networks to identify hub modules closely related to glioma grade, and performed pathway enrichment analysis on genes from significant modules. In gene co-expression network constructed by 2345 differentially expressed genes from 121 gene expression profiles for glioma, we identified the black and blue modules that associated with grading. The module preservation analysis based on 118 samples indicates that the two modules were replicable. Enrichment analysis showed that the extracellular matrix genes were enriched for blue module, while cell division genes were enriched for black module. According to survival analysis, 21 hub genes were significantly up-regulated and one gene was significantly down-regulated. What’s more, IKBIP, SEC24D, and FAM46A are the genes with little attention among the 22 hub genes. In this study, IKBIP, SEC24D, and FAM46A related to glioma were mentioned for the first time to the current knowledge, which might provide a new idea for us to study the disease in the future. IKBIP, SEC24D and FAM46A among the 22 hub genes identified that are related to the malignancy degree of glioma might be used as new biomarkers to improve the diagnosis, treatment and prognosis of glioma.

Mfsd2a Reverses Spatial Learning and Memory Impairment Caused by Chronic Cerebral Hypoperfusion via Protection of the Blood-Brain Barrier

Disruption of the blood–brain barrier (BBB) can lead to cognitive impairment. Major facilitator superfamily domain-containing protein 2a (Mfsd2a) is a newly discovered protein that is essential for maintaining BBB integrity. However, the role of Mfsd2a in vascular cognitive impairment has not been explored yet. In this study, a rat model of chronic cerebral hypoperfusion (CCH) was established by producing permanent bilateral common carotid artery occlusion (2VO) in rats. We found that after the 2VO procedure, the rats exhibited cognitive impairment, showed increased BBB leakage within the hippocampus, and had reduced expression of the Mfsd2a protein. The overexpression of Mfsd2a in the rat hippocampus reversed these changes. Further investigations using transmission electron microscopy revealed a significantly increased rate of vesicular transcytosis in the BBB of the hippocampus of the CCH rats; the rate reduced after overexpression of Mfsd2a. Moreover, Mfsd2a overexpression did not cause changes in the expression of tight junction-associated proteins and in the ultrastructures of the tight junctions. In conclusion, Mfsd2a attenuated BBB damage and ameliorated cognitive impairment in CCH rats, and its protective effect on the BBB was achieved via inhibition of vesicular transcytosis.

Complexes formed with integrin-α5 and KCNB1 potassium channel wild type or epilepsy-susceptibility variants modulate cellular plasticity via Ras and Akt signaling

Voltage-gated potassium (K⁺) channel subfamily B member 1 (KCNB1, Kv2.1) and integrin-α5 form macromolecular complexes-named integrin-α5-KCNB1 complexes (IKCs)-in the human brain, but their function was poorly understood. Here we report that membrane depolarization triggered IKC intracellular signals mediated by small GTPases of the Ras subfamily and protein kinase B (Akt) to advance the development of filopodia and lamellipodia in Chinese hamster ovary cells, stimulate their motility, and enhance neurite outgrowth in mouse neuroblastoma Neuro2a cells. Five KCNB1 mutants (L211P, R312H G379R, G381R, and F416L) linked to severe infancy or early-onset epileptic encephalopathy exhibited markedly defective conduction. However, although L211P, G379R, and G381R normally engaged Ras/Akt and stimulated cell migration, R312H and F416L failed to activate Ras/Akt signaling and did not enhance cell migration. Taken together, these data suggest that IKCs modulate cellular plasticity via Ras and Akt signaling. As such, defective IKCs may cause epilepsy through mechanisms other than dysregulated excitability such as, for example, abnormal neuronal development and resulting synaptic connectivity.-Yu, W., Shin, M. R., Sesti, F. Complexes formed with integrin-α5 and KCNB1 potassium channel wild type or epilepsy-susceptibility variants modulate cellular plasticity via Ras and Akt signaling.

Inflammaging and Oxidative Stress in Human Diseases: From Molecular Mechanisms to Novel Treatments

It has been proposed that a chronic state of inflammation correlated with aging known as inflammaging, is implicated in multiple disease states commonly observed in the elderly population. Inflammaging is associated with over-abundance of reactive oxygen species in the cell, which can lead to oxidation and damage of cellular components, increased inflammation, and activation of cell death pathways. This review focuses on inflammaging and its contribution to various age-related diseases such as cardiovascular disease, cancer, neurodegenerative diseases, chronic obstructive pulmonary disease, diabetes, and rheumatoid arthritis. Recently published mechanistic details of the roles of reactive oxygen species in inflammaging and various diseases will also be discussed. Advancements in potential treatments to ameliorate inflammaging, oxidative stress, and consequently, reduce the morbidity of multiple disease states will be explored.