Effects of aging on protein expression in mice brain microvessels: ROS scavengers, mRNA/protein stability, glycolytic enzymes, mitochondrial complexes, and basement membrane components

Three-dimensional object geometry of mitochondria-associated signal: 3-D analysis pipeline for two-photon image stacks of cerebrovascular endothelial mitochondria

Increasing evidence indicates the role of mitochondrial and vascular dysfunction in aging and aging-associated pathologies; however, the exact mechanisms and chronological processes remain enigmatic. High-energy demand organs, such as the brain, depend on the health of their mitochondria and vasculature for the maintenance of normal functions, therefore representing vulnerable targets for aging. This methodology article describes an analysis pipeline for three-dimensional (3-D) mitochondria-associated signal geometry of two-photon image stacks of brain vasculature. The analysis methods allow the quantification of mitochondria-associated signals obtained in real time in their physiological environment. In addition, signal geometry results will allow the extrapolation of fission and fusion events under normal conditions, during aging, or in the presence of different pathological conditions, therefore contributing to our understanding of the role mitochondria play in a variety of aging-associated diseases with vascular etiology.NEW & NOTEWORTHY Analysis pipeline for 3-D mitochondria-associated signal geometry of two-photon image stacks of brain vasculature.

Exploring the properties and potential of the neural extracellular matrix for next-generation regenerative therapies

The extracellular matrix (ECM) is a dynamic and complex network of proteins and molecules that surrounds cells and tissues in the nervous system and orchestrates a myriad of biological functions. This review carefully examines the diverse interactions between cells and the ECM, as well as the transformative chemical and physical changes that the ECM undergoes during neural development, aging, and disease. These transformations play a pivotal role in shaping tissue morphogenesis and neural activity, thereby influencing the functionality of the central nervous system (CNS). In our comprehensive review, we describe the diverse behaviors of the CNS ECM in different physiological and pathological scenarios and explore the unique properties that make ECM-based strategies attractive for CNS repair and regeneration. Addressing the challenges of scalability, variability, and integration with host tissues, we review how advanced natural, synthetic, and combinatorial matrix approaches enhance biocompatibility, mechanical properties, and functional recovery. Overall, this review highlights the potential of decellularized ECM as a powerful tool for CNS modeling and regenerative purposes and sets the stage for future research in this exciting field. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

Atherosclerotic burden and cerebral small vessel disease: exploring the link through microvascular aging and cerebral microhemorrhages

Cerebral microhemorrhages (CMHs, also known as cerebral microbleeds) are a critical but frequently underestimated aspect of cerebral small vessel disease (CSVD), bearing substantial clinical consequences. Detectable through sensitive neuroimaging techniques, CMHs reveal an extensive pathological landscape. They are prevalent in the aging population, with multiple CMHs often being observed in a given individual. CMHs are closely associated with accelerated cognitive decline and are increasingly recognized as key contributors to the pathogenesis of vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). This review paper delves into the hypothesis that atherosclerosis, a prevalent age-related large vessel disease, extends its pathological influence into the cerebral microcirculation, thereby contributing to the development and progression of CSVD, with a specific focus on CMHs. We explore the concept of vascular aging as a continuum, bridging macrovascular pathologies like atherosclerosis with microvascular abnormalities characteristic of CSVD. We posit that the same risk factors precipitating accelerated aging in large vessels (i.e., atherogenesis), primarily through oxidative stress and inflammatory pathways, similarly instigate accelerated microvascular aging. Accelerated microvascular aging leads to increased microvascular fragility, which in turn predisposes to the formation of CMHs. The presence of hypertension and amyloid pathology further intensifies this process. We comprehensively overview the current body of evidence supporting this interconnected vascular hypothesis. Our review includes an examination of epidemiological data, which provides insights into the prevalence and impact of CMHs in the context of atherosclerosis and CSVD. Furthermore, we explore the shared mechanisms between large vessel aging, atherogenesis, microvascular aging, and CSVD, particularly focusing on how these intertwined processes contribute to the genesis of CMHs. By highlighting the role of vascular aging in the pathophysiology of CMHs, this review seeks to enhance the understanding of CSVD and its links to systemic vascular disorders. Our aim is to provide insights that could inform future therapeutic approaches and research directions in the realm of neurovascular health.

Acute severe hypoglycemia alters mouse brain microvascular proteome

Hypoglycemia increases the risk related to stroke and neurodegenerative diseases, however, the underlying mechanisms are unclear. For the first time, we studied the effect of a single episode (acute) of severe (ASH) and mild (AMH) hypoglycemia on mouse brain microvascular proteome. After four-hour fasting, insulin was administered (i.p) to lower mean blood glucose in mice and induce ∼30 minutes of ASH (∼30 mg/dL) or AMH (∼75 mg/dL), whereas a similar volume of saline was given to control mice (∼130 mg/dL). Blood glucose was allowed to recover over 60 minutes either spontaneously or by 20% dextrose administration (i.p). Twenty-four hours later, the brain microvessels (BMVs) were isolated, and tandem mass tag (TMT)-based quantitative proteomics was performed using liquid chromatography-mass spectrometry (LC/MS). When compared to control, ASH significantly downregulated 13 proteins (p ≤ 0.05) whereas 23 proteins showed a strong trend toward decrease (p ≤ 0.10). When compared to AMH, ASH significantly induced the expression of 35 proteins with 13 proteins showing an increasing trend. AMH downregulated only 3 proteins. ASH-induced downregulated proteins are involved in actin cytoskeleton maintenance needed for cell shape and migration which are critical for blood-brain barrier maintenance and angiogenesis. In contrast, ASH-induced upregulated proteins are RNA-binding proteins involved in RNA splicing, transport, and stability. Thus, ASH alters BMV proteomics to impair cytoskeletal integrity and RNA processing which are critical for cerebrovascular function.

Thioredoxin (Trx): A redox target and modulator of cellular senescence and aging-related diseases

Thioredoxin (Trx) is a compact redox-regulatory protein that modulates cellular redox state by reducing oxidized proteins. Trx exhibits dual functionality as an antioxidant and a cofactor for diverse enzymes and transcription factors, thereby exerting influence over their activity and function. Trx has emerged as a pivotal biomarker for various diseases, particularly those associated with oxidative stress, inflammation, and aging. Recent clinical investigations have underscored the significance of Trx in disease diagnosis, treatment, and mechanistic elucidation. Despite its paramount importance, the intricate interplay between Trx and cellular senescence-a condition characterized by irreversible growth arrest induced by multiple aging stimuli-remains inadequately understood. In this review, our objective is to present a comprehensive and up-to-date overview of the structure and function of Trx, its involvement in redox signaling pathways and cellular senescence, its association with aging and age-related diseases, as well as its potential as a therapeutic target. Our review aims to elucidate the novel and extensive role of Trx in senescence while highlighting its implications for aging and age-related diseases.

Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway

We previously reported evidence that oxidative stress during aging leads to adverse protein profile changes of brain cortical microvessels (MVs: end arterioles, capillaries, and venules) that affect mRNA/protein stability, basement membrane integrity, and ATP synthesis capacity in mice. As an extension of our previous study, we also found that proteins which comprise the blood-brain barrier (BBB) and regulate mitochondrial quality control were also significantly decreased in the mice's cortical MVs with aging. Interestingly, the neuroinflammatory protein fibrinogen (Fgn) was increased in mice brain MVs, which corresponds with clinical reports indicating that the plasma Fgn concentration increased progressively with aging. In this study, protein-protein interaction network analysis indicated that high expression of Fgn is linked with downregulated expression of both BBB- and mitochondrial fission/fusion-related proteins in mice cortical MVs with aging. To investigate the mechanism of Fgn action, we observed that 2 mg/mL or higher concentration of human plasma Fgn changed cell morphology, induced cytotoxicity, and increased BBB permeability in primary human brain microvascular endothelial cells (HBMECs). The BBB tight junction proteins were significantly decreased with increasing concentration of human plasma Fgn in primary HBMECs. Similarly, the expression of phosphorylated dynamin-related protein 1 (pDRP1) and other mitochondrial fission/fusion-related proteins were also significantly reduced in Fgn-treated HBMECs. Interestingly, DRP1 knockdown by shRNA(h) resulted in the reduction of both BBB- and mitochondrial fission/fusion-related proteins in HBMECs. Our results suggest that elevated Fgn downregulates DRP1, leading to mitochondrial-dependent endothelial and BBB dysfunction in the brain microvasculature.

Advanced Age in Humans and Mouse Models of Glioblastoma Show Decreased Survival from Extratumoral Influence

PURPOSE

Glioblastoma (GBM) is the most common aggressive primary malignant brain tumor in adults with a median age of onset of 68 to 70 years old. Although advanced age is often associated with poorer GBM patient survival, the predominant source(s) of maladaptive aging effects remains to be established. Here, we studied intratumoral and extratumoral relationships between adult patients with GBM and mice with brain tumors across the lifespan.

EXPERIMENTAL DESIGN

Electronic health records at Northwestern Medicine and the NCI SEER databases were evaluated for GBM patient age and overall survival. The commercial Tempus and Caris databases, as well as The Cancer Genome Atlas were profiled for gene expression, DNA methylation, and mutational changes with varying GBM patient age. In addition, gene expression analysis was performed on the extratumoral brain of younger and older adult mice with or without a brain tumor. The survival of young and old wild-type or transgenic (INK-ATTAC) mice with a brain tumor was evaluated after treatment with or without senolytics and/or immunotherapy.

RESULTS

Human patients with GBM ≥65 years of age had a significantly decreased survival compared with their younger counterparts. While the intra-GBM molecular profiles were similar between younger and older patients with GBM, non-tumor brain tissue had a significantly different gene expression profile between young and old mice with a brain tumor and the eradication of senescent cells improved immunotherapy-dependent survival of old but not young mice.

CONCLUSIONS

This work suggests a potential benefit for combining senolytics with immunotherapy in older patients with GBM.

Targeting mitochondria in the aged cerebral vasculature with SS-31, a proteomic study of brain microvessels

Cognitive impairment and dementias during aging such as Alzheimer's disease are linked to functional decline and structural alterations of the brain microvasculature. Although mechanisms leading to microvascular changes during aging are not clear, loss of mitochondria, and reduced efficiency of remaining mitochondria appear to play a major role. Pharmacological agents, such as SS-31, which target mitochondria have been shown to be effective during aging and diseases; however, the benefit to mitochondrial- and non-mitochondrial proteins in the brain microvasculature has not been examined. We tested whether attenuation of aging-associated changes in the brain microvascular proteome via targeting mitochondria represents a therapeutic option for the aging brain. We used aged male (> 18 months) C57Bl6/J mice treated with a mitochondria-targeted tetrapeptide, SS-31, or vehicle saline. Cerebral blood flow (CBF) was determined using laser speckle imaging during a 2-week treatment period. Then, isolated cortical microvessels (MVs) composed of end arterioles, capillaries, and venules were used for Orbitrap Eclipse Tribrid mass spectrometry. CBF was similar among the groups, whereas bioinformatic analysis revealed substantial differences in protein abundance of cortical MVs between SS-31 and vehicle. We identified 6267 proteins, of which 12% were mitochondria-associated. Of this 12%, 107 were significantly differentially expressed and were associated with oxidative phosphorylation, metabolism, the antioxidant defense system, or mitochondrial dynamics. Administration of SS-31 affected many non-mitochondrial proteins. Our findings suggest that mitochondria in the microvasculature represent a therapeutic target in the aging brain, and widespread changes in the proteome may underlie the rejuvenating actions of SS-31 in aging.

Novel Approaches to the Establishment of Local Microenvironment from Resorbable Biomaterials in the Brain In Vitro Models

The development of brain in vitro models requires the application of novel biocompatible materials and biopolymers as scaffolds for controllable and effective cell growth and functioning. The "ideal" brain in vitro model should demonstrate the principal features of brain plasticity like synaptic transmission and remodeling, neurogenesis and angiogenesis, and changes in the metabolism associated with the establishment of new intercellular connections. Therefore, the extracellular scaffolds that are helpful in the establishment and maintenance of local microenvironments supporting brain plasticity mechanisms are of critical importance. In this review, we will focus on some carbohydrate metabolites-lactate, pyruvate, oxaloacetate, malate-that greatly contribute to the regulation of cell-to-cell communications and metabolic plasticity of brain cells and on some resorbable biopolymers that may reproduce the local microenvironment enriched in particular cell metabolites.

Role of cytokines and reactive oxygen species in brain aging

Aging is a complex process that produces profound effects on the brain. Although a number of external factors can promote the initiation and progression of brain aging, peripheral and central changes in the immune cells with time, also play an important role. Immunosenescence, which is an age-associated decline in immune function and Inflammaging, a low-grade inflammatory state in the aging brain contribute to an elevation in cytokine and reactive oxygen species production. In this review, we focus on the pro-inflammatory state that is established in the brain as a consequence of these two phenomena and the resulting detrimental changes in brain structure, function and repair that lead to a decline in central and neuroendocrine function.

Expression of placental glycans and its role in regulating peripheral blood NK cells during preeclampsia: a perspective

Preeclampsia is a pregnancy-related multisystem disorder characterized by altered trophoblast invasion, oxidative stress, exacerbation of systemic inflammatory response, and endothelial damage. The pathogenesis includes hypertension and mild-to-severe microangiopathy in the kidney, liver, placenta, and brain. The main mechanisms involved in its pathogenesis have been proposed to limit trophoblast invasion and increase the release of extracellular vesicles from the syncytiotrophoblast into the maternal circulation, exacerbating the systemic inflammatory response. The placenta expresses glycans as part of its development and maternal immune tolerance during gestation. The expression profile of glycans at the maternal-fetal interface may play a fundamental role in physiological pregnancy changes and disorders such as preeclampsia. It is unclear whether glycans and their lectin-like receptors are involved in the mechanisms of maternal-fetal recognition by immune cells during pregnancy homeostasis. The expression profile of glycans appears to be altered in hypertensive disorders of pregnancy, which could lead to alterations in the placental microenvironment and vascular endothelium in pregnancy conditions such as preeclampsia. Glycans with immunomodulatory properties at the maternal-fetal interface are altered in early-onset severe preeclampsia, implying that innate immune system components, such as NK cells, exacerbate the systemic inflammatory response observed in preeclampsia. In this article, we discuss the evidence for the role of glycans in gestational physiology and the perspective of glycobiology on the pathophysiology of hypertensive disorders in gestation.

The Glymphatic System May Play a Vital Role in the Pathogenesis of Hepatic Encephalopathy: A Narrative Review

Hepatic encephalopathy (HE) is a neurological complication of liver disease resulting in cognitive, psychiatric, and motor symptoms. Although hyperammonemia is a key factor in the pathogenesis of HE, several other factors have recently been discovered. Among these, the impairment of a highly organized perivascular network known as the glymphatic pathway seems to be involved in the progression of some neurological complications due to the accumulation of misfolded proteins and waste substances in the brain interstitial fluids (ISF). The glymphatic system plays an important role in the clearance of brain metabolic derivatives and prevents aggregation of neurotoxic agents in the brain ISF. Impairment of it will result in aggravated accumulation of neurotoxic agents in the brain ISF. This could also be the case in patients with liver failure complicated by HE. Indeed, accumulation of some metabolic by-products and agents such as ammonia, glutamine, glutamate, and aromatic amino acids has been reported in the human brain ISF using microdialysis technique is attributed to worsening of HE and correlates with brain edema. Furthermore, it has been reported that the glymphatic system is impaired in the olfactory bulb, prefrontal cortex, and hippocampus in an experimental model of HE. In this review, we discuss different factors that may affect the function of the glymphatic pathways and how these changes may be involved in HE.

Circulating Plasma Exosomal Proteins of Either SHIV-Infected Rhesus Macaque or HIV-Infected Patient Indicates a Link to Neuropathogenesis

Despite the suppression of human immunodeficiency virus (HIV) replication by combined antiretroviral therapy (cART), 50-60% of HIV-infected patients suffer from HIV-associated neurocognitive disorders (HAND). Studies are uncovering the role of extracellular vesicles (EVs), especially exosomes, in the central nervous system (CNS) due to HIV infection. We investigated links among circulating plasma exosomal (crExo) proteins and neuropathogenesis in simian/human immunodeficiency virus (SHIV)-infected rhesus macaques (RM) and HIV-infected and cART treated patients (Patient-Exo). Isolated EVs from SHIV-infected (SHIV-Exo) and uninfected (CTL-Exo) RM were predominantly exosomes (particle size < 150 nm). Proteomic analysis quantified 5654 proteins, of which 236 proteins (~4%) were significantly, differentially expressed (DE) between SHIV-/CTL-Exo. Interestingly, different CNS cell specific markers were abundantly expressed in crExo. Proteins involved in latent viral reactivation, neuroinflammation, neuropathology-associated interactive as well as signaling molecules were expressed at significantly higher levels in SHIV-Exo than CTL-Exo. However, proteins involved in mitochondrial biogenesis, ATP production, autophagy, endocytosis, exocytosis, and cytoskeleton organization were significantly less expressed in SHIV-Exo than CTL-Exo. Interestingly, proteins involved in oxidative stress, mitochondrial biogenesis, ATP production, and autophagy were significantly downregulated in primary human brain microvascular endothelial cells exposed with HIV+/cART+ Patient-Exo. We showed that Patient-Exo significantly increased blood-brain barrier permeability, possibly due to loss of platelet endothelial cell adhesion molecule-1 protein and actin cytoskeleton structure. Our novel findings suggest that circulating exosomal proteins expressed CNS cell markers-possibly associated with viral reactivation and neuropathogenesis-that may elucidate the etiology of HAND.

Advances in the Functions of Thioredoxin System in Central Nervous System Diseases

Significance: The thioredoxin system comprises thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate, besides an endogenous Trx inhibitor, the thioredoxin-interacting protein (TXNIP). The Trx system plays critical roles in maintaining the redox homeostasis in the central nervous system (CNS), in which oxidative stress damage is prone to occurrence due to its high-energy demand. Recent Advances: Increasing studies have demonstrated that the expression or activity of Trx/TrxR is usually decreased and that TXNIP expression is increased in patients with CNS diseases, including neurodegenerative diseases, cerebral ischemia, traumatic brain injury, and depression, as well as in their cellular and animal models. The compromise of Trx/TrxR enhances the susceptibility of neurons to related pathological state. Increased TXNIP not only enhances the inhibition of Trx activity, but also activates the NOD-like receptor protein 3 inflammasome, resulting in neuroinflammation in the brain. Critical Issues: In this review, we highlight the sources of oxidative stress in the CNS. The expression and function of the Trx system are summarized in different CNS diseases. This review also mentions that some inducers of Trx show neuroprotection in CNS diseases. Future Directions: Accumulating evidence has demonstrated the important roles of the Trx system in CNS diseases, suggesting that the Trx system may be a promising therapeutic target for CNS diseases. Further study should aim to develop the most effective inducers of Trx and specific inhibitors of TXNIP and to apply them in the clinical trials for the treatment of CNS diseases. Antioxid. Redox Signal. 38, 425-441.

Adipose stromal vascular fraction reverses mitochondrial dysfunction and hyperfission in aging-induced coronary microvascular disease

Aging is associated with blunted coronary microvascular vasodilatory function. Previously, systemically administered adipose stromal vascular fraction (SVF) therapy reversed aging-induced attenuation of β1-adrenergic- and flow-mediated dilation dependent on reducing mitochondrial reactive oxygen species. We hypothesized that SVF-mediated recovery of microvascular dilatory function is dependent on recovery of mitochondrial function, specifically by reducing mitochondrial hyperfission. Female Fischer-344 rats were allocated into young control, old control, and old + SVF therapy groups. Pressure myography, immunofluorescent staining, Western blot analysis, and RNA sequencing were performed to determine coronary microvascular mitochondrial dynamics and function. Gene and protein expression of fission-mediator DRP-1 was enhanced with aging but reversed by SVF therapy. SVF facilitated an increase in fusion-mediator MFN-1 gene and protein expression. Mitochondrial morphology was characterized as rod-like and densely networked in young controls, isolated circular and punctate with aging, and less circularity with partially restored mitochondrial branch density with SVF therapy. Decreased mitochondrial membrane potential and ATP bioavailability in aged animals at baseline and during flow-mediated dilation were reversed by SVF and accompanied with enhanced oxygen consumption. Dilation to norepinephrine and flow in young controls were dependent on uninhibited mitochondrial fusion, whereas inhibiting fission did not restore aged microvessel response to norepinephrine or flow. SVF-mediated recovery of β-adrenergic function was dependent on uninhibited mitochondrial fusion, whereas recovery of flow-mediated dilation was dependent on maintained mitochondrial fission. Impaired dilation in aging is mitigated by SVF therapy, which recovers mitochondrial function and fission/fusion balance.NEW & NOTEWORTHY We elucidated the consequences of aging on coronary microvascular mitochondrial health as well as SVF's ability to reverse these effects. Aging shifts gene/protein expression and mitochondrial morphology indicating hyperfission, alongside attenuated mitochondrial membrane potential and ATP bioavailability, all reversed using SVF therapy. Mitochondrial membrane potential and ATP levels correlated with vasodilatory efficiency. Mitochondrial dysfunction is a contributing pathological factor in aging that can be targeted by therapeutic SVF to preserve microvascular dilative function.