NAD+ rescues aging-induced blood-brain barrier damage via the CX43-PARP1 axis

TSPO exacerbates sepsis-induced cardiac dysfunction by inhibiting p62-Mediated autophagic flux via the ROS-RIP1/RIP3-exosome axis

Septic cardiomyopathy (SCM) is a critical complication of sepsis, primarily attributed to mitochondrial dysfunction and impaired autophagic flux. This study explores the role of translocator protein (TSPO) in SCM pathogenesis and assesses its potential as a therapeutic target. We identified increased TSPO expression in plasma samples from sepsis patients, with further validation in septic rats and LPS-stimulated H9C2 cardiomyocytes. Elevated TSPO disrupted mitochondrial function, leading to increased reactive oxygen species (ROS) production and activation of the RIP1/RIP3 pathway, which hindered p62-positive autophagosome degradation and promoted inflammation. Moreover, exosome release containing TSPO-positive autophagosomes into plasma may exacerbate systemic inflammation. NADH, identified as a TSPO-binding molecule, restored autophagic flux, improved mitochondrial function, and enhanced cardiac performance and survival in septic rats. These findings suggest that targeting TSPO with NADH could alleviate mitochondrial dysfunction and inflammatory responses in SCM, providing a promising therapeutic strategy for sepsis-induced cardiac injury.

The mechanisms, hallmarks, and therapies for brain aging and age-related dementia

Age-related cognitive decline and dementia are significant manifestations of brain aging. As the elderly population grows rapidly, the health and socio-economic impacts of cognitive dysfunction have become increasingly significant. Although clinical treatment of dementia has faced considerable challenges over the past few decades, with limited breakthroughs in slowing its progression, there has been substantial progress in understanding the molecular mechanisms and hallmarks of age-related dementia (ARD). This progress brings new hope for the intervention and treatment of this disease. In this review, we categorize the latest findings in ARD biomarkers into four stages based on disease progression: Healthy brain, pre-clinical, mild cognitive impairment, and dementia. We then systematically summarize the most promising therapeutic approaches to prevent or slow ARD at four levels: Genome and epigenome, organelle, cell, and organ and organism. We emphasize the importance of early prevention and detection, along with the implementation of combined treatments as multimodal intervention strategies, to address brain aging and ARD in the future.

NAD+ supplement relieved chronic sleep restriction (CSR)-induced microglial proinflammation in vivo and in vitro

Sleep insufficiency is a significant health problem worldwide and can induce multiple neurodevelopmental disorders in the central nervous system (CNS). Sleep deprivation (SD), especially chronic SD, leads to cognition and memory loss and worsens neurodegenerative disease liability. Microglia are the main inflammation-dominant glia and play a crucial role in SD-induced neurological impairments. Nicotinamide adenine dinucleotide (NAD+) is a redox reaction coenzyme that exerts anti-inflammatory and mitochondria-protective effects in microglia. Whether NAD+ mitigated SD-induced neurological disorders by regulating microglial functions is still unknown. In the current study, we designed an in vivo and in vitro model to evaluate the neuroprotective effect of NAD+ on chronic sleep restriction (CSR) and further investigate the underlying mechanisms. Behavioral tests and immunofluorescence staining were applied to investigate the cognition impairments and microglial activation. Biochemical experiments were tested to analyze the oxidative status and possible mechanism. In vitro data were used to verify the in vivo data. Our results displayed that NAD+ supplement mitigated CSR-induced cognitive decline and microglial activation response by suppressing the expression of pro-inflammatory cytokines in vivo. NAD+ administration also decreased oxidative stress and mitochondrial impairments in microglia. In vitro results showed that NAD+ treatment inhibited ROS production and prompted M1 conversion to M2 phenotype. cGAS-STING/NF-κB pathways were significantly activated but down-regulated by NAD+ administration. H151, a STING antagonist, was applied to validate that NAD+ treatment alleviates neuroinflammation partially by regulating cGAS-STING pathways in microglia. Our findings suggest that NAD+ supplement is a promising therapy for sleep disorders-induced neurological problems, and cGAS-STING pathway may act as a critical regulator in microglial proinflammation.

Insight into cerebral microvessel endothelial regulation of cognitive impairment: A systematic review of the causes and consequences

Research on cognitive impairment (CI) has increasingly focused on the central nervous system, identifying numerous neuronal targets and circuits of relevance for CI pathogenesis and treatment. Brain microvascular endothelial cells (BMECs) form a barrier between the peripheral and central nervous systems, constituting the primary component of the blood-brain barrier (BBB) and playing a vital role in maintaining neural homeostasis. Stemming from the recognition of the close link between vascular dysfunction and CI, in recent years intense research has been devoted to characterize the pathological changes and molecular mechanisms underlying BMEC dysfunction both during normal aging and in disorders of cognition such as Alzheimer's disease and vascular dementia. In this review, keywords such as "dementia", "cognitive impairment", and "endothelium" were used to search PubMed and Web of Science. Based on the literature thus retrieved, we first review some common triggers of CI, i.e., amyloid beta and tau deposition, chronic cerebral hypoperfusion, hyperglycemia, viral infections, and neuroinflammation, and describe the specific mechanisms responsible for endothelial damage. Second, we review molecular aspects of endothelial damage leading to BBB disruption, neuronal injury, and myelin degeneration, which are crucial events underlying CI. Finally, we summarize the potential targets of endothelial damage in the development of cognitive dysfunction associated with Alzheimer's disease, vascular dementia, type 2 diabetes mellitus, and physiological aging. A thorough understanding of the induction mechanism and potential outcomes of microvascular endothelial damage is of great significance for the study of CI, to guide both diagnostic and therapeutic approaches for its prevention and treatment.

Pathobiochemistry of Aging and Neurodegeneration: Deregulation of NAD+ Metabolism in Brain Cells

NAD+ plays a pivotal role in energy metabolism and adaptation to external stimuli and stressful conditions. A significant reduction in intracellular NAD+ levels is associated with aging and contributes to the development of chronic cardiovascular, neurodegenerative, and metabolic diseases. It is of particular importance to maintain optimal levels of NAD+ in cells with high energy consumption, particularly in the brain. Maintaining the tissue level of NAD+ with pharmacological tools has the potential to slow down the aging process, to prevent the development of age-related diseases. This review covers key aspects of NAD+ metabolism in terms of brain metabolic plasticity, including NAD+ biosynthesis and degradation in different types of brain cells, as well as its contribution to the development of neurodegeneration and aging, and highlights up-to-date approaches to modulate NAD+ levels in brain cells.

Defective autophagy of pericytes enhances radiation-induced senescence promoting radiation brain injury

BACKGROUND

Radiation-induced brain injury (RBI) represents a major challenge for cancer patients undergoing cranial radiotherapy. However, the molecular mechanisms and therapeutic strategies of RBI remain inconclusive. With the continuous exploration of the mechanisms of RBI, an increasing number of studies have implicated cerebrovascular dysfunction as a key factor in RBI-related cognitive impairment. As pericytes are a component of the neurovascular unit, there is still a lack of understanding in current research about the specific role and function of pericytes in RBI.

METHODS

We constructed a mouse model of RBI-associated cognitive dysfunction in vivo and an in vitro radiation-induced pericyte model to explore the effects of senescent pericytes on the blood-brain barrier (BBB) and normal central nervous system cells, even glioma cells. To further clarify the effects of pericyte autophagy on senescence, molecular mechanisms were explored at the animal and cellular levels. Finally, we validated the clearance of pericyte senescence by using a senolytic drug and all-trans retinoic acid to investigate the role of radiation-induced pericyte senescence.

RESULTS

Our findings indicated that radiation-induced pericyte senescence plays a key role in BBB dysfunction, leading to RBI and subsequent cognitive decline. Strikingly, pericyte senescence also contributed to the growth and invasion of glioma cells. We further demonstrated that defective autophagy in pericytes is a vital regulatory mechanism for pericyte senescence. Moreover, autophagy activated by rapamycin could reverse pericyte senescence. Notably, the elimination of senescent cells by senolytic drugs significantly mitigated radiation-induced cognitive dysfunction.

CONCLUSIONS

Our results demonstrated that pericyte senescence may be a promising therapeutic target for RBI and glioma progression.

Early central nervous system development and neuron regeneration

The nervous system is the most complex system in the human body, and the normal development of the central nervous system (CNS) is essential for maintaining the healthy life activities of the individual. CNS development requires the orchestration of multiple internal or external or direct or indirect factors to regulate neural stem cell fate specification. Here, we provide a broad overview of the regulatory system of nerve cell fate decisions and discuss the latest technological approaches to achieve neural regeneration. Understanding the CNS development and regeneration mechanisms has shifted the paradigm from traditional experiments to high-throughput sequencing.

Acute changes in hippocampal metabolism after anesthesia and surgery: Implications for perioperative neurocognitive disorder

BACKGROUND

The risk of developing dementia is higher in individuals who suffer from perioperative neurocognitive disorder (PND), including postoperative cognitive dysfunction (POCD) and delirium. Recent studies have indicated correlations between anesthesia, surgery and PND. Acute metabolic changes induced by anesthesia and surgery may be related to cognitive impairments. Despite a paucity of research on acute metabolic changes in the hippocampus during surgery, there are conflicting about specific metabolites.

METHODS

We developed a mouse model of cognitive impairment induced by isoflurane anesthesia and unilateral nephrectomy. Cognition was evaluated by Y maze and fear conditioning test (FCT). The hippocampus was harvested after the surgery. LC-MS (liquid chromatography-mass spectrometry) was performed. The differential metabolites involved in lipid, amino acid, nucleotide, carbohydrate metabolism were analyzed.

RESULTS

Anesthesia and surgery exposure induced cognition decline. A total of 49 metabolites were significantly up-regulated and 122 down-regulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway of the metabolites identified purine, glutathione, nicotinate and nicotinamide metabolism. Metabolites involved in lipid, amino acid, nucleotide, carbohydrate metabolism were identified including nicotinamide adenine dinucleotide (NAD), 1-Methylnicotinamide, propionic acid, histidine, adenosine, and guanosine cyclic monophosphate. Some metabolites exhibited a consistent change trend in the hippocampus of aging mice.

CONCLUSIONS

The study indicates that anesthesia and surgery can induce acute alterations in hippocampal metabolomics, including metabolites involved in lipid, amino acid, nucleotide, and carbohydrate metabolism. These metabolites may play a role in modulating PND through the regulation of neuroinflammation, oxidative stress, blood-brain barrier (BBB) permeability.

Cerebral biomimetic nano-drug delivery systems: A frontier strategy for immunotherapy

Brain diseases are a significant threat to human health, especially in the elderly, and this problem is growing as the aging population increases. Efficient brain-targeted drug delivery has been the greatest challenge in treating brain disorders due to the unique immune environment of the brain, including the blood-brain barrier (BBB). Recently, cerebral biomimetic nano-drug delivery systems (CBNDSs) have provided a promising strategy for brain targeting by mimicking natural biological materials. Herein, this review explores the latest understanding of the immune microenvironment of the brain, emphasizing the immune mechanisms of the occurrence and progression of brain disease. Several brain targeting systems are summarized, including cell-based, exosome-based, protein-based, and microbe-based CBNDSs, and their immunological mechanisms are highlighted. Moreover, given the rise of immunotherapy, the latest applications of CBNDSs in immunotherapy are also discussed. This review provides a comprehensive understanding of CBNDSs and serves as a guideline for immunotherapy in treating brain diseases. In addition, it provides inspiration for the future of CBNDSs.

Nicotinamide adenine dinucleotide treatment confers resistance to neonatal ischemia and hypoxia: effects on neurobehavioral phenotypes

JOURNAL/nrgr/04.03/01300535-202412000-00031/figure1/v/2024-04-08T165401Z/r/image-tiff Neonatal hypoxic-ischemic brain injury is the main cause of hypoxic-ischemic encephalopathy and cerebral palsy. Currently, there are few effective clinical treatments for neonatal hypoxic-ischemic brain injury. Here, we investigated the neuroprotective and molecular mechanisms of exogenous nicotinamide adenine dinucleotide, which can protect against hypoxic injury in adulthood, in a mouse model of neonatal hypoxic-ischemic brain injury. In this study, nicotinamide adenine dinucleotide (5 mg/kg) was intraperitoneally administered 30 minutes before surgery and every 24 hours thereafter. The results showed that nicotinamide adenine dinucleotide treatment improved body weight, brain structure, adenosine triphosphate levels, oxidative damage, neurobehavioral test outcomes, and seizure threshold in experimental mice. Tandem mass tag proteomics revealed that numerous proteins were altered after nicotinamide adenine dinucleotide treatment in hypoxic-ischemic brain injury mice. Parallel reaction monitoring and western blotting confirmed changes in the expression levels of proteins including serine (or cysteine) peptidase inhibitor, clade A, member 3N, fibronectin 1, 5'-nucleotidase, cytosolic IA, microtubule associated protein 2, and complexin 2. Proteomics analyses showed that nicotinamide adenine dinucleotide ameliorated hypoxic-ischemic injury through inflammation-related signaling pathways (e.g., nuclear factor-kappa B, mitogen-activated protein kinase, and phosphatidylinositol 3 kinase/protein kinase B). These findings suggest that nicotinamide adenine dinucleotide treatment can improve neurobehavioral phenotypes in hypoxic-ischemic brain injury mice through inflammation-related pathways.

WIF-1 contributes to lupus-induced neuropsychological deficits via the CRYAB/STAT4-SHH axis

BACKGROUND

Neuropsychiatric systemic lupus erythematosus (NPSLE) often manifests as cognitive deterioration, with activated microglia and blood-brain barrier (BBB) disruption implicated in these neurological complications. Wnt-inhibitory factor-1 (WIF-1), a secreted protein, has been detected in the cerebrospinal fluid (CSF) of NPSLE patients. However, the contribution of WIF-1 in contributing to lupus cognitive impairment remains poorly understood.

METHODS

Using MRL/MpJ-Faslpr (MRL/lpr) lupus-prone mice and TLR7 agonist imiquimod (IMQ)-induced lupus mice, recombinant WIF-1 protein (rWIF-1) and adeno-associated virus (AAV) encoding sh-WIF-1 were administered via intracerebroventricular injection. Behavioral tests, histopathological examinations, flow cytometry, and molecular biology techniques were employed to investigate the underlying mechanisms.

RESULTS

Microinjection of rWIF-1 exacerbated cognitive deficits and mood abnormalities, increased BBB leakage and neuronal degeneration, and caused aberrant activation of microglia and synaptic pruning in the hippocampus. Conversely, lupus mice injected with AAV-shWIF-1 exhibited significant remission. In vitro, rWIF-1 induced overactivation of microglia with an increased CD86+ pro-inflammatory subpopulation, upregulated phagocytic activity, and excessive synaptic engulfment, contributing to increased BBB permeability. Furthermore, WIF-1 exerted its biological effects through the CRYAB/STAT4 pathway, transcriptionally decreasing SHH production. We also identified that symmetric dimethylarginine (SDMA) could alleviate rWIF-1-induced microglial activation and BBB damage, thereby restoring SHH levels.

CONCLUSIONS

In conclusion, WIF-1 exacerbates lupus-induced cognitive dysfunction in mice by triggering aberrant microglial activation and BBB disruption through the CRYAB/STAT4-SHH axis, highlighting the potential therapeutic effects of SDMA for the treatment of NPSLE.

Small Molecule Hydrogels Loading Small Molecule Drugs from Chinese Medicine for the Enhanced Treatment of Traumatic Brain Injury

Self-assembly of hydrogels for mechanical support and drug delivery has been extensively researched in traumatic brain injury (TBI), where treatment options are limited. The chief challenge is that most self-assembled hydrogels rely on high molecular carriers or the incorporation of exogenous inactive substances as mediators. It is difficult for these drug delivery systems to achieve clinical translation due to concerns regarding biological safety. Here we report a small molecule hydrogel (GBR-gel) loading small molecule drugs (glycyrrhizic acid, berberine, and rhein) that originated from popular Chinese medicines without additional drug loading or inactive components under physiological conditions. In the long run, GBR-gel possesses several advantages, including ease of preparation, cost-effectiveness, and high biocompatibility. As a proof-of-concept, GBR-gel allows for prompt administration at the site of brain injury to exert potent pharmacodynamic effects. Further single-cell RNA sequencing and experimental validation indicated that GBR-gel can effectively rescue the suppressed glutamatergic synapse pathway after TBI, thereby attenuating inflammatory responses and neural impairments. Our work provides an alternative strategy for timely intervention of TBI.

An accelerated Parkinson's disease monkey model using AAV-α-synuclein plus poly(ADP-ribose)

The etiology of Parkinson's disease (PD) remains elusive, and the limited availability of suitable animal models hampers research on pathogenesis and drug development. We report the development of a cynomolgus monkey model of PD that combines adeno-associated virus (AAV)-mediated overexpression of α-synuclein into the substantia nigra with an injection of poly(ADP-ribose) (PAR) into the striatum. Our results show that pathological processes were accelerated, including dopaminergic neuron degeneration, Lewy body aggregation, and hallmarks of inflammation in microglia and astrocytes. Behavioral phenotypes, dopamine transporter imaging, and transcriptomic profiling further demonstrate consistencies between the model and patients with PD. This model can help to determine the mechanisms underlying PD impacted by α-synuclein and PAR and aid in the accelerated development of therapeutic strategies for PD.

Synergistic anti-aging effect of Dendrobium officinale polysaccharide and spermidine: A metabolomics analysis focusing on the regulation of lipid, nucleotide and energy metabolism

The importance of synergy has been underscored in recent medical research for augmenting the efficacy of therapeutic interventions, targeting multiple biological pathways simultaneously. Our prior research elucidated that Dendrobium officinale polysaccharide (DOP) has the potential to prolong the lifespan of Caenorhabditis elegans (C. elegans) via regulating gut microbiota. Concurrently, spermidine (Spd), as a mimicking caloric restriction, facilitates autophagy and exerts a pronounced anti-aging effect. To enhance the anti-aging capabilities of DOP, we conducted a comprehensive study examining the combined effects of DOP and Spd in C. elegans, incorporating metabolomics analysis to investigate the underlying mechanisms. A combination of 250 mg/L DOP and 29.0 mg/L Spd yielded the most favorable outcomes in lifespan extension, evidencing a synergistic effect with a combination index (CI) of 0.65. In oxidative and heat stress tolerance assays, the observed CIs were 0.50 and 0.33, respectively. Metabolomic analysis highlighted significant alterations in metabolites related to lipid, nucleotide and energy metabolism, notably regulating glycerol 3-phosphate, linoleoyl glycerol, docosapentaenoic acid and β-nicotinamide mononucleotide, nicotinamide adenine dinucleotide. The effects of DS on lipid metabolism were further validated using Oil Red O staining and triglyceride level in C. elegans. The results indicated that DS may primarily be via modulating lipid metabolism. To further confirm these findings, a high-fat diet-induced mouse model was employed. Consequently, it can be inferred that the synergistic anti-aging impact of DOP and Spd is likely mediated primarily through alterations in lipid metabolic processes.

Lactate Contributes to Remote Ischemic Preconditioning-Mediated Protection Against Myocardial Ischemia Reperfusion Injury by Facilitating Autophagy via the AMP-Activated Protein Kinase-Mammalian Target of Rapamycin-Transcription Factor EB-Connexin 43 Axis

Remote ischemic preconditioning (RIPC) exerts a protective role on myocardial ischemia/reperfusion (I/R) injury by the release of various humoral factors. Lactate is a common metabolite in ischemic tissues. Nevertheless, little is known about the role lactate plays in myocardial I/R injury and its underlying mechanism. This investigation revealed that RIPC elevated the level of lactate in blood and myocardium. Furthermore, AZD3965, a selective monocarboxylate transporter 1 inhibitor, and 2-deoxy-d-glucose, a glycolysis inhibitor, mitigated the effects of RIPC-induced elevated lactate in the myocardium and prevented RIPC against myocardial I/R injury. In an in vitro hypoxia/reoxygenation model, lactate markedly mitigated hypoxia/reoxygenation-induced cell damage in H9c2 cells. Further studies suggested that lactate contributed to RIPC, rescuing I/R-induced autophagy deficiency by promoting transcription factor EB (TFEB) translocation to the nucleus through activating the AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) pathway without influencing the phosphatidylinositol 3-kinase-Akt pathway, thus reducing cardiomyocyte damage. Interestingly, lactate up-regulated the mRNA and protein expression of connexin 43 (CX43) by facilitating the binding of TFEB to CX43 promoter in the myocardium. Functionally, silencing of TFEB attenuated the protective effect of lactate on cell damage, which was reversed by overexpression of CX43. Further mechanistic studies suggested that lactate facilitated CX43-regulated autophagy via the AMPK-mTOR-TFEB signaling pathway. Collectively, this research demonstrates that RIPC protects against myocardial I/R injury through lactate-mediated myocardial autophagy via the AMPK-mTOR-TFEB-CX43 axis.

Microglial activation and polarization in type 2 diabetes-related cognitive impairment: A focused review of pathogenesis

Microglia, as immune cells in the central nervous system, are closely related to cognitive impairment associated with type 2 diabetes (T2D). Preliminary explorations have investigated the relationship between T2D-related cognitive impairment and the activation and polarization of microglia. This review summarizes the potential mechanisms of microglial activation and polarization in the context of T2D. It discusses central inflammatory responses, neuronal apoptosis, amyloid-β deposition, and abnormal phosphorylation of Tau protein mediated by microglial activation and polarization, exploring the connections between microglial activation and polarization and T2D-related cognitive impairment from multiple perspectives. Additionally, this review provides references for future treatment targeting microglia in T2D-related cognitive impairment and for clinical translation.

Endothelial Myosin IIA Is Required for the Maintenance of Blood-Brain Barrier Integrity

Brain endothelial cells (ECs) are essential elements of the blood-brain barrier (BBB), maintaining its integrity through both paracellular junctions and transcellular transport systems. Myosin IIA, a multifunctional protein, plays a significant role in various cellular processes, including cytoskeletal maintenance, cell division, and signal transduction. While Myosin IIA has been implicated in bleeding and ischemic stroke, its role in regulating BBB integrity under physiological conditions remains unclear. In this study, we investigated the impact of Myosin IIA deficiency on BBB integrity using intravenous tracer injections and models of epilepsy. Flow cytometry, Western blot, and real-time PCR were employed to isolate brain cells and assess changes in protein and mRNA levels. Additionally, immunofluorescence staining and electron microscopy were used to explore alterations in protein expression and the structure of BBB. Our results demonstrate that endothelial Myosin IIA deficiency increased BBB permeability and exacerbated symptoms in BBB-related diseases. Mechanistically, we found that Myosin IIA modulates β-catenin transcription and protein interactions. The overexpression of β-catenin in brain endothelial Myosin IIA deficiency mice improved BBB integrity and reduced disease severity. This study establishes Myosin IIA as a critical regulator of BBB integrity and suggests new therapeutic targets for vascular diseases.

Exploring the heterogeneous targets of metabolic aging at single-cell resolution

Our limited understanding of metabolic aging poses major challenges to comprehending the diverse cellular alterations that contribute to age-related decline, and to devising targeted interventions. This review provides insights into the heterogeneous nature of cellular metabolism during aging and its response to interventions, with a specific focus on cellular heterogeneity and its implications. By synthesizing recent findings using single-cell approaches, we explored the vulnerabilities of distinct cell types and key metabolic pathways. Delving into the cell type-specific alterations underlying the efficacy of systemic interventions, we also discuss the complexity of integrating single-cell data and advocate for leveraging computational tools and artificial intelligence to harness the full potential of these data, develop effective strategies against metabolic aging, and promote healthy aging.

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

The role of SIRT3 in homeostasis and cellular health

Mitochondria are responsible for maintaining cellular energy levels, and play a major role in regulating homeostasis, which ensures physiological function from the molecular to whole animal. Sirtuin 3 (SIRT3) is the major protein deacetylase of mitochondria. SIRT3 serves as a nutrient sensor; under conditions of mild metabolic stress, SIRT3 activity is increased. Within the mitochondria, SIRT3 regulates every complex of the electron transport chain, the tricarboxylic acid (TCA) and urea cycles, as well as the mitochondria membrane potential, and other free radical scavengers. This article reviews the role of SIRT3 in regulating homeostasis, and thus physiological function. We discuss the role of SIRT3 in regulating reactive oxygen species (ROS), ATP, immunological function and mitochondria dynamics.

Macrod1 suppresses diabetic cardiomyopathy via regulating PARP1-NAD+-SIRT3 pathway

Diabetic cardiomyopathy (DCM), one of the most serious long-term consequences of diabetes, is closely associated with oxidative stress, inflammation and apoptosis in the heart. MACRO domain containing 1 (Macrod1) is an ADP-ribosylhydrolase 1 that is highly enriched in mitochondria, participating in the pathogenesis of cardiovascular diseases. In this study, we investigated the role of Macrod1 in DCM. A mice model was established by feeding a high-fat diet (HFD) and intraperitoneal injection of streptozotocin (STZ). We showed that Macrod1 expression levels were significantly downregulated in cardiac tissue of DCM mice. Reduced expression of Macrod1 was also observed in neonatal rat cardiomyocytes (NRCMs) treated with palmitic acid (PA, 400 μM) in vitro. Knockout of Macrod1 in DCM mice not only worsened glycemic control, but also aggravated cardiac remodeling, mitochondrial dysfunction, NAD+ consumption and oxidative stress, whereas cardiac-specific overexpression of Macrod1 partially reversed these pathological processes. In PA-treated NRCMs, overexpression of Macrod1 significantly inhibited PARP1 expression and restored NAD+ levels, activating SIRT3 to resist oxidative stress. Supplementation with the NAD+ precursor Niacin (50 μM) alleviated oxidative stress in PA-stimulated cardiomyocytes. We revealed that Macrod1 reduced NAD+ consumption by inhibiting PARP1 expression, thereby activating SIRT3 and anti-oxidative stress signaling. This study identifies Macrod1 as a novel target for DCM treatment. Targeting the PARP1-NAD+-SIRT3 axis may open a novel avenue to development of new intervention strategies in DCM. Schematic illustration of macrod1 ameliorating diabetic cardiomyopathy oxidative stress via PARP1-NAD+-SIRT3 axis.

Connexins and blood-brain barrier: Beyond the gap

In this issue of Neuron, Zhan, Meng, et al.1 explore the non-canonical roles of connexin-43 in brain endothelial cells and connect its faltering expression to the depletion of nicotinamide adenine dinucleotide (NAD), mitochondrial stress, and blood-brain barrier rupture.

Blood-brain barrier dysfunction and Alzheimer's disease: associations, pathogenic mechanisms, and therapeutic potential

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ), hyperphosphorylation of tau, and neuroinflammation in the brain. The blood-brain barrier (BBB) limits solutes from circulating blood from entering the brain, which is essential for neuronal functioning. Focusing on BBB function is important for the early detection of AD and in-depth study of AD pathogenic mechanisms. However, the mechanism of BBB alteration in AD is still unclear, which hinders further research on therapeutics that target the BBB to delay the progression of AD. The exact timing of the vascular abnormalities in AD and the complex cause-and-effect relationships remain uncertain. Thus, it is necessary to summarize and emphasize this process. First, in this review, the current evidence for BBB dysfunction in AD is summarized. Then, the interrelationships and pathogenic mechanisms between BBB dysfunction and the risk factors for AD, such as Aβ, tau, neuroinflammation, apolipoprotein E (ApoE) genotype and aging, were analyzed. Finally, we discuss the current status and future directions of therapeutic AD strategies targeting the BBB. We hope that these summaries or reviews will allow readers to better understand the relationship between the BBB and AD.