Inflammation as common link to progressive neurological diseases

JNK inhibition mitigates sepsis-associated encephalopathy via attenuation of neuroinflammation, oxidative stress and apoptosis

Sepsis-associated encephalopathy (SAE) is a severe complication of sepsis, leading to cognitive dysfunction and neuronal damage. C-Jun N-terminal kinases (JNKs), a subset of the MAP kinase family, have attracted substantial interest for their role in cellular events during sepsis conditions. Previous investigations have established the involvement of JNK signaling against memory impairment and abnormal synaptic plasticity. However, the present study is the first to investigate the effects of JNK inhibition in sepsis-associated cerebral injury and cognitive impairments. This study investigated the neuroprotective effects of SP600125, a selective JNK inhibitor, in cecal ligation and puncture (CLP) mouse model of sepsis. CLP-induced sepsis resulted in significant cognitive impairments, as assessed by the open field test, inhibitory avoidance test, morris water maze, and novel object recognition test. Additionally, septic mice exhibited increased serum levels of neuronal injury markers (S100B and NSE), pro-inflammatory cytokines (TNF-α and IL-1β), and oxidative stress markers (MDA), along with decreased antioxidant levels (GSH, SOD, and CAT). Histological analysis revealed neuronal pyknosis, degeneration, and loss of Nissl bodies in the cortex and hippocampus of septic mice. Furthermore, sepsis-induced blood-brain barrier dysfunction was evident from increased cerebral edema. Treatment with SP600125 (10, 30, and 50 mg/kg) significantly attenuated CLP-induced cognitive deficits, neuronal injury, neuroinflammation, oxidative stress, and apoptosis in a dose-dependent manner. The present study provides preliminary evidence that JNK inhibition by SP600125 exerts neuroprotective effects against sepsis-induced encephalopathy in vivo via suppression of neuroinflammation, oxidative stress, and apoptosis.

Stimuli-Responsive Nano Drug Delivery Systems for the Treatment of Neurological Diseases

Nanomaterials with unparalleled physical and chemical attributes have become a cornerstone in the field of nanomedicine delivery. These materials can be engineered into various functionalized nanocarriers, which have become the focus of research. Stimulus-responsive nanodrug delivery systems (SRDDS) stand out as a sophisticated class of nanocarriers that can release drugs in response to environmental cues. Due to the complex pathogenesis and the multifaceted pathological environment of the nervous system, developing accurate and effective drug therapy with low side-effects is a formidable task. In recent years, SRDDS have been widely used in the treatment of neurological diseases. By customizing SRDDS to align with the specific microenvironment of the nervous system tissues or external stimulation, the efficacy of drug delivery can be enhanced. This review provides an in-depth look at the characteristics of the microenvironment of neurological diseases and highlights case studies of SRDDS tailored to treat these disorders based on the unique stimulation criteria of nervous system tissues or external triggers. Additionally, this review provides a comprehensive overview of the progress and future prospects of SRDDS technology in the treatment of neurological diseases, providing valuable guidance for its transition from fundamental research to clinical application.

Targeting Cytokine-Mediated Inflammation in Brain Disorders: Developing New Treatment Strategies

Cytokine-mediated inflammation is increasingly recognized for playing a vital role in the pathophysiology of a wide range of brain disorders, including neurodegenerative, psychiatric, and neurodevelopmental problems. Pro-inflammatory cytokines such as interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) cause neuroinflammation, alter brain function, and accelerate disease development. Despite progress in understanding these pathways, effective medicines targeting brain inflammation are still limited. Traditional anti-inflammatory and immunomodulatory drugs are effective in peripheral inflammatory illnesses. Still, they face substantial hurdles when applied to the central nervous system (CNS), such as the blood-brain barrier (BBB) and unwanted systemic effects. This review highlights the developing treatment techniques for modifying cytokine-driven neuroinflammation, focusing on advances that selectively target critical cytokines involved in brain pathology. Novel approaches, including cytokine-specific inhibitors, antibody-based therapeutics, gene- and RNA-based interventions, and sophisticated drug delivery systems like nanoparticles, show promise with respect to lowering neuroinflammation with greater specificity and safety. Furthermore, developments in biomarker discoveries and neuroimaging techniques are improving our ability to monitor inflammatory responses, allowing for more accurate and personalized treatment regimens. Preclinical and clinical trial data demonstrate the therapeutic potential of these tailored techniques. However, significant challenges remain, such as improving delivery across the BBB and reducing off-target effects. As research advances, the creation of personalized, cytokine-centered therapeutics has the potential to alter the therapy landscape for brain illnesses, giving patients hope for better results and a higher quality of life.

Exploring the Therapeutic Potential of Glycyrrhiza Compounds in Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. Research shows that the development of AD is linked to neuroinflammation, endoplasmic reticulum stress, mitochondrial dysfunction, cell death, and abnormal cholinergic signaling. Glycyrrhiza compounds contain active ingredients and extracts that offer multiple benefits, including targeting various pathways, high efficacy with low toxicity, and long-lasting therapeutic effects. These benefits highlight the significant potential of Glycyrrhiza compounds for preventing and treating AD. This review summarizes recent advancements in Glycyrrhiza compounds for preventing and treating AD. It focuses on their inhibitory effects on key signaling pathways, such as Toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), and cholinergic signaling. This study aims to establish a scientific framework for using Glycyrrhiza compounds in the clinical prevention and treatment of AD and to support the development of new therapeutic interventions.

Investigating interleukin-8 in Alzheimer's disease: A comprehensive review

Several studies indicate that the development of Alzheimer's disease (AD) has strong interactions with immune mechanisms within the brain, indicating a close association between inflammation in the central nervous system and the progression of neurodegeneration. Despite considerable progress in understanding the inflammatory aspects of AD, several of them remain unresolved. Pro-inflammatory cytokines and microglia are pivotal components in the inflammatory cascade. Among these, the role of interleukin-8 (IL-8) in neurodegeneration seems complex and multifaceted, involving inflammation, neurotoxicity, blood-brain barrier disruption, and oxidative stress, and is still poorly characterized. We conducted a review to describe the evidence of IL-8 involvement in AD. IL-8 is a cytokine known for its proinflammatory properties and typically produced by macrophages, predominantly functions as a chemotactic signal for attracting neutrophils to inflamed sites in the bloodstream. Interestingly, IL-8 is also present in the brain, where it is primarily released by microglia in response to inflammatory signals. This review aims to provide a comprehensive overview of the structure, function, and regulatory mechanisms of IL-8 relevant to AD pathology.

Hippocampal Nogo66-NgR1 signaling activation restricts postsynaptic assembly in aged mice with postoperative neurocognitive disorders

Postoperative neurocognitive disorders (pNCD) are a common neurological complication, especially in elderly following anesthesia and surgery. Yet, the underlying mechanisms of pNCD remain elusive. This study aimed to investigate the molecular mechanisms that compromise synaptic metaplasticity in pNCD development with a focus on the involvement of Nogo-66 receptor 1 (NgR1) in the pathogenesis of pNCD in aged mice. Aged mice subjected to anesthesia and laparotomy surgery exhibited anxiety-like behavior and contextual fear memory impairment. Moreover, the procedure significantly increased NogoA and NgR1 expressions, particularly in the hippocampal CA1 and CA3 regions. This increase led to the depolymerization of F-actin, attributed to the activation of the RhoA-GTPase, resulting in a reduction of dendritic spines and changes in their morphology. Additionally, these changes hindered the efficient postsynaptic delivery of the subunit GluA1 and GluA2 of AMPA receptors (AMPARs), consequently diminishing excitatory neurotransmission in the hippocampus. Importantly, administering the competitive NgR1 antagonist peptide NEP1-40 (Nogo-A extracellular peptide residues 1-40 amino acids of Nogo-66) and Fasudil (a Rho-kinase inhibitor) effectively mitigated synaptic impairments and reversed neurocognitive deficits in aged mice following anesthesia and surgery. Our work indicates that high hippocampal Nogo66-NgR1 signaling disrupts postsynaptic AMPA receptor surface delivery due to F-actin depolymerization in the pathophysiology of pNCD.

The Interplay Between Accumulation of Amyloid-Beta and Tau Proteins, PANoptosis, and Inflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a common progressive neurodegenerative disorder, and the vast majority of cases occur in elderly patients. Recently, the accumulation of Aβ and tau proteins has drawn considerable attention in AD research. This review explores the multifaceted interactions between these proteins and their contribution to the pathological landscape of AD, encompassing synaptic dysfunction, neuroinflammation, and PANoptosis. PANoptosis is a collective term for programmed cell death (PCD) modalities that encompass elements of apoptosis, pyroptosis, and necroptosis. The accumulation of Aβ peptides and tau proteins, along with the immune response in brain cells, may trigger PANoptosis, thus advancing the progression of the disease. Recent advancements in molecular imaging and genetics have provided deeper insights into the interactions between Aβ peptides, tau proteins, and the immune response. The review also discusses the role of mitochondrial dysregulation in AD. The exploration of the interplay between neurodegeneration, immune responses, and cell death offers promising avenues for the development of innovative treatments.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Chemotherapy-induced cognitive impairment and glia: A new take on chemobrain?

The significant rise in cancer survivorship stands out as one of the most notable achievements of modern science. However, this comes with a significant burden, as cancer treatment is not without adverse effects. Lately, there has been a growing focus on cognitive dysfunction associated with cancer treatment, often referred to as 'chemobrain'. It significantly impacts the quality of life for cancer survivors. The underlying mechanisms studied so far usually focus on neurons, while other cells of the central nervous system are often overlooked. This review seeks to place the hypothesis that glial cells may play a role in the development of chemotherapy-induced cognitive dysfunction. It summarizes the primary mechanisms proposed to date while underscoring the existing gaps in this research field. Inflammation and release of pro-inflammatory mediators by M1 microglia and A1 astrocytes are the most prevalent findings after chemotherapy. However, activation of A1 astrocytes by some chemotherapeutic agents may contribute to neuronal degeneration, alterations in synaptic branches, as well as glutamate excitotoxicity, which can contribute to cognitive impairment. Furthermore, the reduction in the number of oligodendrocytes after chemotherapy may also impact the myelin sheath, contributing to 'chemobrain'. Furthermore, some chemotherapeutic drugs activate M1 microglia, which is associated with decreased neuroplasticity and, possibly, cognitive impairment. In conclusion, data regarding the effects of chemotherapy on glial cells are scarce, and it is essential to understand how these cells are affected after cancer treatment to enable reliable therapeutic or preventive actions on cancer-treated patients.

Spatial regulation of NMN supplementation on brain lipid metabolism upon subacute and sub-chronic PM exposure in C57BL/6 mice

BACKGROUND

Atmospheric particulate matter (PM) exposure-induced neuroinflammation is critical in mediating nervous system impairment. However, effective intervention is yet to be developed.

RESULTS

In this study, we examine the effect of β-nicotinamide mononucleotide (NMN) supplementation on nervous system damage upon PM exposure and the mechanism of spatial regulation of lipid metabolism. 120 C57BL/6 male mice were exposed to real ambient PM for 11 days (subacute) or 16 weeks (sub-chronic). NMN supplementation boosted the level of nicotinamide adenine dinucleotide (NAD+) in the mouse brain by 2.04 times. This augmentation effectively reduced neuroinflammation, as evidenced by a marked decrease in activated microglia levels across various brain regions, ranging from 29.29 to 85.96%. Whole brain lipidomics analysis revealed that NMN intervention resulted in an less increased levels of ceramide (Cer) and lysophospholipid in the brain following subacute PM exposure, and reversed triglyceride (TG) and glycerophospholipids (GP) following sub-chronic PM exposure, which conferred mice with anti-neuroinflammation response, improved immune function, and enhanced membrane stability. In addition, we demonstrated that the hippocampus and hypothalamus might be the most sensitive brain regions in response to PM exposure and NMN supplementation. Particularly, the alteration of TG (60:10, 56:2, 60:7), diacylglycerol (DG, 42:6), and lysophosphatidylcholine (LPC, 18:3) are the most profound, which correlated with the changes in functional annotation and perturbation of pathways including oxidative stress, inflammation, and membrane instability unveiled by spatial transcriptomic analysis.

CONCLUSIONS

This study demonstrates that NMN intervention effectively reduces neuroinflammation in the hippocampus and hypothalamus after PM exposure by modulating spatial lipid metabolism. Strategies targeting the improvement of lipid homeostasis may provide significant protection against brain injury associated with air pollutant exposure.

The Potential of Mitochondrial Therapeutics in the Treatment of Oxidative Stress and Inflammation in Aging

Mitochondria are central to cellular energy production, and their dysfunction is a major contributor to oxidative stress and chronic inflammation, pivotal factors in aging, and related diseases. With aging, mitochondrial efficiency declines, leading to an increase in ROS and persistent inflammatory responses. Therapeutic interventions targeting mitochondrial health show promise in mitigating these detrimental effects. Antioxidants such as MitoQ and MitoVitE, and supplements like coenzyme Q10 and NAD + precursors, have demonstrated potential in reducing oxidative stress. Additionally, gene therapy aimed at enhancing mitochondrial function, alongside lifestyle modifications such as regular exercise and caloric restriction can ameliorate age-related mitochondrial decline. Exercise not only boosts mitochondrial biogenesis but also improves mitophagy. Enhancing mitophagy is a key strategy to prevent the accumulation of dysfunctional mitochondria, which is crucial for cellular homeostasis and longevity. Pharmacological agents like sulforaphane, SS-31, and resveratrol indirectly promote mitochondrial biogenesis and improve cellular resistance to oxidative damage. The exploration of mitochondrial therapeutics, including emerging techniques like mitochondrial transplantation, offers significant avenues for extending health span and combating age-related diseases. However, translating these findings into clinical practice requires overcoming challenges in precisely targeting dysfunctional mitochondria and optimizing delivery mechanisms for therapeutic agents. Continued research is essential to refine these approaches and fully understand the interplay between mitochondrial dynamics and aging.

The impact of physical exercise on neuroinflammation mechanism in Alzheimer's disease

Introduction

Alzheimer's disease (AD), a major cause of dementia globally, imposes significant societal and personal costs. This review explores the efficacy of physical exercise as a non-pharmacological intervention to mitigate the impacts of AD.

Methods

This review draws on recent studies that investigate the effects of physical exercise on neuroinflammation and neuronal enhancement in individuals with AD.

Results

Consistent physical exercise alters neuroinflammatory pathways, enhances cognitive functions, and bolsters brain health among AD patients. It favorably influences the activation states of microglia and astrocytes, fortifies the integrity of the blood-brain barrier, and attenuates gut inflammation associated with AD. These changes are associated with substantial improvements in cognitive performance and brain health indicators.

Discussion

The findings underscore the potential of integrating physical exercise into comprehensive AD management strategies. Emphasizing the necessity for further research, this review advocates for the refinement of exercise regimens to maximize their enduring benefits in decelerating the progression of AD.

Kynurenic acid inflammatory signaling expands in primates and impairs prefrontal cortical cognition

Cognitive deficits from dorsolateral prefrontal cortex (dlPFC) dysfunction are common in neuroinflammatory disorders, including long-COVID, schizophrenia and Alzheimer's disease, and have been correlated with kynurenine inflammatory signaling. Kynurenine is further metabolized to kynurenic acid (KYNA) in brain, where it blocks NMDA and α7-nicotinic receptors (nic-α7Rs). These receptors are essential for neurotransmission in dlPFC, suggesting that KYNA may cause higher cognitive deficits in these disorders. The current study found that KYNA and its synthetic enzyme, KAT II, have greatly expanded expression in primate dlPFC in both glia and neurons. Local application of KYNA onto dlPFC neurons markedly reduced the delay-related firing needed for working memory via actions at NMDA and nic-α7Rs, while inhibition of KAT II enhanced neuronal firing in aged macaques. Systemic administration of agents that reduce KYNA production similarly improved cognitive performance in aged monkeys, suggesting a therapeutic avenue for the treatment of cognitive deficits in neuroinflammatory disorders.

Neuroinflammation and Neurodegenerative Diseases: How Much Do We Still Not Know?

The term "neuroinflammation" defines the typical inflammatory response of the brain closely related to the onset of many neurodegenerative diseases (NDs). Neuroinflammation is well known, but its mechanisms and pathways are not entirely comprehended. Some progresses have been achieved through many efforts and research. Consequently, new cellular and molecular mechanisms, diverse and conventional, are emerging. In listing some of those that will be the subject of our description and discussion, essential are the important roles of peripheral and infiltrated monocytes and clonotypic cells, alterations in the gut-brain axis, dysregulation of the apelinergic system, alterations in the endothelial glycocalyx of the endothelial component of neuronal vascular units, variations in expression of some genes and levels of the encoding molecules by the action of microRNAs (miRNAs), or other epigenetic factors and distinctive transcriptional factors, as well as the role of autophagy, ferroptosis, sex differences, and modifications in the circadian cycle. Such mechanisms can add significantly to understanding the complex etiological puzzle of neuroinflammation and ND. In addition, they could represent biomarkers and targets of ND, which is increasing in the elderly.