Oral treatment of 4-methylumbelliferone reduced perineuronal nets and improved recognition memory in mice

Pretreatment with 4-methylumbilliferon improves anxiety-like behaviors and memory impairment in stressed rats via modulation of neuronal cell death and oxidative stress

This work was done to investigate the ameliorating impact of 4-methylumbilliferon (4-MU) on spatial learning and memory dysfunction and restraint stress (STR)-induced anxiety-like behaviors in male Wistar rats and the underlying mechanisms. Thirty-two animals were assigned into 4 cohorts: control, 4-MU, STR, and STR+4-MU. Animals were exposed to STR for 4 h per day for 14 consecutive days or kept in normal conditions (healthy animals without exposure to stress). 4-MU (25 mg/kg) was intraperitoneally administered once daily to STR rats before restraint stress for 14 consecutive days. The behavioral tests were performed through Morris water maze tests and elevated-plus maze to examine learning/memory function, and anxiety levels, respectively. The levels of the antioxidant defense biomarkers (GPX, SOD) and MDA as an oxidant molecule in the brain tissues were measured using commercial ELISA kits. Neuronal loss or density of neurons was evaluated using Nissl staining. STR exposure could cause significant alterations in the levels of the antioxidant defense biomarkers (MDA, GPX, and SOD) in the prefrontal cortex and hippocampus, induce anxiety, and impair spatial learning and memory function. Treatment with 4-MU markedly reduced anxiety levels and improved spatial learning and memory dysfunction via restoring the antioxidant defense biomarkers to normal values and reducing MDA levels. Moreover, more intact cells with normal morphologies were detected in STR-induced animals treated with 4-MU. 4-MU could attenuate the STR-induced anxiety-like behaviors and spatial learning and memory dysfunction by reducing oxidative damage and neuronal loss in the prefrontal cortex and hippocampus region. Taken together, our findings provide new insights regarding the potential therapeutic effects of 4-MU against neurobehavioral disorders induced by STR.

Pramipexole, a D3 receptor agonist, increases cortical gamma power and biochemical correlates of cortical excitation; implications for mood disorders

Major depressive disorder (MDD) has been associated with deficits in working memory as well as underlying gamma oscillation power. Consistent with this, overall reductions in cortical excitation have also been described with MDD. In previous work, we have demonstrated that the monoamine reuptake inhibitor venlafaxine increases gamma oscillation power in ex vivo hippocampal slices and that this is associated with concomitant increases in pyramidal arbour and reduced levels of plasticity-restricting perineuronal nets (PNNs). In the present study, we have examined the effects of chronic treatment with pramipexole (PPX), a D3 dopamine receptor agonist, for its effects on gamma oscillation power as measured by in vivo electroencephalography (EEG) recordings in female BALB/c and C57Bl6 mice. We observe a modest but significant increase in 20-50 Hz gamma power with PPX in both strains. Additionally, biochemical analysis of prefrontal cortex lysates from PPX-treated BALB/c mice shows a number of changes that could contribute to, or follow from, increased pyramidal excitability and/or gamma power. PPX-associated changes include reduced levels of specific PNN components as well as tissue inhibitor of matrix metalloproteases-1 (TIMP-1), which inhibits long-term potentiation of synaptic transmission. Consistent with its effects on gamma power, PNN proteins and TIMP-1, chronic PPX treatment also improves working memory and reduces anhedonia. Together these results add to an emerging literature linking extracellular matrix and/or gamma oscillation power to both mood and cognition.

Modulation of stress-, pain-, and alcohol-related behaviors by perineuronal nets

Perineuronal nets (PNNs) are a special form of central nervous system extracellular matrix enriched in hyaluronan, chondroitin sulfate proteoglycans, tenascins, and link proteins that regulate synaptic plasticity. Most PNNs in the brain surround parvalbumin-expressing inhibitory interneurons, which tightly regulate excitatory/inhibitory balance and brain activity associated with optimal cognitive functioning. Alterations in PNNs have been observed in neurological diseases and psychiatric disorders, suggesting that they may be key contributors to the neuropathological progression and behavioral changes in these diseases. Alcohol use disorder (AUD), major depressive disorder (MDD), and chronic pain are highly comorbid conditions, and changes in PNNs have been observed in animal models of these disorders, as well as postmortem tissue from individuals diagnosed with AUD and MDD. This review focuses on the literature describing stress-, alcohol-, and pain-induced adaptations in PNNs, potential cellular contributors to altered PNNs, and the role of PNNs in behaviors related to these disorders. Medicines that can restore PNNs to a non-pathological state may be a novel therapeutic approach to treating chronic pain, AUD, and MDD.

4-methylumbilliferon (4-MU) as a Potential Treatment Against Cerebral ischemia and Reperfusion Injury in Rats; An Experimental Study

Introduction

Ischemic stroke (IS) is one of the three main fatal disorders and is a major health challenge. 4-methylumbelliferone (4-MU) is one of the coumarin derivatives (7-hydroxy-4-methylcoumarin) with antioxidant and anti-inflammatory impact. This study was conducted to elucidate the neuroprotective effects and anti-inflammatory impact of 4-MU in a rodent model of IS.

Methods

The IS model was induced by middle cerebral artery occlusion (MCAO) for 1 hour and reperfusion was established for 24 hours. 44 Male Wistar rats were divided into four groups: 1) Sham, 2) MCAO, 3) MCAO + Vehicle, and 4) MCAO + 4-MU (25 mg/kg). Evaluation of neurological deficit was performed using Garcia's score. 2,3,5-triphenoyl-2H-tetrazolium chloride (TTC) staining was employed to measure infarct size. Nissl staining was applied to determine neuronal loss. Moreover, western blotting was utilized to detect the expression of the proteins relevant to the TLR4/NF-κB/NLRP3 axis (p-NF-κB p65, TLR4, NLRP3, IL-1β, IL-10, IL-18, ASC, and Caspase-1).

Results

It was observed that MCAO caused neurological deficit (P<0.0001), infarct (P<0.0001), and neuronal loss (P<0.002); up-regulated NLRP3 (P<0.0001), TLR4 (P<0.0001), p-NF-κB p65 (P<0.0005), IL-1β (P<0.0014), IL-18 (P<0.0001), ASC (P<0.0027), and Caspase-1 (P<0.0052); and reduced IL-10 concentrations (P<0.0024). Administration of 4-MU (25 mg/kg) quickly after reperfusion reduced neurological deficit (P<0.0001), infarct size (P<0.0001), neuronal loss (P<0.0058), and down-regulated NLRP3 (P<0.0257), TLR4 (P<0.0001), p-NF-κB p65 (P<0.0075), IL-1β (P<0.0106), IL-18 (P<0.0005), ASC (P<0.0072), and Caspase-1 (P<0.0315), and increased IL-10 concentrations (P<0.0215).

Conclusion

These results indicate that 4-MU can attenuate injury after MCAO by suppressing the TLR4/NF-κB/NLRP3 axis. Our findings show that 4-MU can be considered a novel therapeutic compound to cure IS.

Perineuronal Net Microscopy: From Brain Pathology to Artificial Intelligence

Perineuronal nets (PNN) are a special highly structured type of extracellular matrix encapsulating synapses on large populations of CNS neurons. PNN undergo structural changes in schizophrenia, epilepsy, Alzheimer's disease, stroke, post-traumatic conditions, and some other brain disorders. The functional role of the PNN microstructure in brain pathologies has remained largely unstudied until recently. Here, we review recent research implicating PNN microstructural changes in schizophrenia and other disorders. We further concentrate on high-resolution studies of the PNN mesh units surrounding synaptic boutons to elucidate fine structural details behind the mutual functional regulation between the ECM and the synaptic terminal. We also review some updates regarding PNN as a potential pharmacological target. Artificial intelligence (AI)-based methods are now arriving as a new tool that may have the potential to grasp the brain's complexity through a wide range of organization levels-from synaptic molecular events to large scale tissue rearrangements and the whole-brain connectome function. This scope matches exactly the complex role of PNN in brain physiology and pathology processes, and the first AI-assisted PNN microscopy studies have been reported. To that end, we report here on a machine learning-assisted tool for PNN mesh contour tracing.

Perineuronal Nets in the CNS: Architects of Memory and Potential Therapeutic Target in Neuropsychiatric Disorders

The extracellular matrix (ECM) within the brain possesses a distinctive composition and functionality, influencing a spectrum of physiological and pathological states. Among its constituents, perineuronal nets (PNNs) are unique ECM structures that wrap around the cell body of many neurons and extend along their dendrites within the central nervous system (CNS). PNNs are pivotal regulators of plasticity in CNS, both during development and adulthood stages. Characterized by their condensed glycosaminoglycan-rich structures and heterogeneous molecular composition, PNNs not only offer neuroprotection but also participate in signal transduction, orchestrating neuronal activity and plasticity. Interfering with the PNNs in adult animals induces the reactivation of critical period plasticity, permitting modifications in neuronal connections and promoting the recovery of neuroplasticity following spinal cord damage. Interestingly, in the adult brain, PNN expression is dynamic, potentially modulating plasticity-associated states. Given their multifaceted roles, PNNs have emerged as regulators in the domains of learning, memory, addiction behaviors, and other neuropsychiatric disorders. In this review, we aimed to address how PNNs contribute to the memory processes in physiological and pathological conditions.

Low oral dose of 4-methylumbelliferone reduces glial scar but is insufficient to induce functional recovery after spinal cord injury

Spinal cord injury (SCI) induces the upregulation of chondroitin sulfate proteoglycans (CSPGs) at the glial scar and inhibits neuroregeneration. Under normal physiological condition, CSPGs interact with hyaluronan (HA) and other extracellular matrix on the neuronal surface forming a macromolecular structure called perineuronal nets (PNNs) which regulate neuroplasticity. 4-methylumbelliferone (4-MU) is a known inhibitor for HA synthesis but has not been tested in SCI. We first tested the effect of 4-MU in HA reduction in uninjured rats. After 8 weeks of 4-MU administration at a dose of 1.2 g/kg/day, we have not only observed a reduction of HA in the uninjured spinal cords but also a down-regulation of CS glycosaminoglycans (CS-GAGs). In order to assess the effect of 4-MU in chronic SCI, six weeks after Th8 spinal contusion injury, rats were fed with 4-MU or placebo for 8 weeks in combination with daily treadmill rehabilitation for 16 weeks to promote neuroplasticity. 4-MU treatment reduced the HA synthesis by astrocytes around the lesion site and increased sprouting of 5-hydroxytryptamine fibres into ventral horns. However, the current dose was not sufficient to suppress CS-GAG up-regulation induced by SCI. Further adjustment on the dosage will be required to benefit functional recovery after SCI.

Matrix disequilibrium in Alzheimer's disease and conditions that increase Alzheimer's disease risk

Alzheimer's Disease (AD) and related dementias are a leading cause of death globally and are predicted to increase in prevalence. Despite this expected increase in the prevalence of AD, we have yet to elucidate the causality of the neurodegeneration observed in AD and we lack effective therapeutics to combat the progressive neuronal loss. Throughout the past 30 years, several non-mutually exclusive hypotheses have arisen to explain the causative pathologies in AD: amyloid cascade, hyper-phosphorylated tau accumulation, cholinergic loss, chronic neuroinflammation, oxidative stress, and mitochondrial and cerebrovascular dysfunction. Published studies in this field have also focused on changes in neuronal extracellular matrix (ECM), which is critical to synaptic formation, function, and stability. Two of the greatest non-modifiable risk factors for development of AD (aside from autosomal dominant familial AD gene mutations) are aging and APOE status, and two of the greatest modifiable risk factors for AD and related dementias are untreated major depressive disorder (MDD) and obesity. Indeed, the risk of developing AD doubles for every 5 years after ≥ 65, and the APOE4 allele increases AD risk with the greatest risk in homozygous APOE4 carriers. In this review, we will describe mechanisms by which excess ECM accumulation may contribute to AD pathology and discuss pathological ECM alterations that occur in AD as well as conditions that increase the AD risk. We will discuss the relationship of AD risk factors to chronic central nervous system and peripheral inflammation and detail ECM changes that may follow. In addition, we will discuss recent data our lab has obtained on ECM components and effectors in APOE4/4 and APOE3/3 expressing murine brain lysates, as well as human cerebrospinal fluid (CSF) samples from APOE3 and APOE4 expressing AD individuals. We will describe the principal molecules that function in ECM turnover as well as abnormalities in these molecular systems that have been observed in AD. Finally, we will communicate therapeutic interventions that have the potential to modulate ECM deposition and turnover in vivo.

CCR5 deficiency normalizes TIMP levels, working memory, and gamma oscillation power in APOE4 targeted replacement mice

The APOE4 allele increases the risk for Alzheimer's disease (AD) in a dose-dependent manner and is also associated with cognitive decline in non-demented elderly controls. In mice with targeted gene replacement (TR) of murine APOE with human APOE3 or APOE4, the latter show reduced neuronal dendritic complexity and impaired learning. APOE4 TR mice also show reduced gamma oscillation power, a neuronal population activity which is important to learning and memory. Published work has shown that brain extracellular matrix (ECM) can reduce neuroplasticity as well as gamma power, while attenuation of ECM can instead enhance this endpoint. In the present study we examine human cerebrospinal fluid (CSF) samples from APOE3 and APOE4 individuals and brain lysates from APOE3 and APOE4 TR mice for levels of ECM effectors that can increase matrix deposition and restrict neuroplasticity. We find that CCL5, a molecule linked to ECM deposition in liver and kidney, is increased in CSF samples from APOE4 individuals. Levels of tissue inhibitor of metalloproteinases (TIMPs), which inhibit the activity of ECM-degrading enzymes, are also increased in APOE4 CSF as well as astrocyte supernatants brain lysates from APOE4 TR mice. Importantly, as compared to APOE4/wild-type heterozygotes, APOE4/CCR5 knockout heterozygotes show reduced TIMP levels and enhanced EEG gamma power. The latter also show improved learning and memory, suggesting that the CCR5/CCL5 axis could represent a therapeutic target for APOE4 individuals.

4-Methylumbeliferone Treatment at a Dose of 1.2 g/kg/Day Is Safe for Long-Term Usage in Rats

4-methylumbelliferone (4MU) has been suggested as a potential therapeutic agent for a wide range of neurological diseases. The current study aimed to evaluate the physiological changes and potential side effects after 10 weeks of 4MU treatment at a dose of 1.2 g/kg/day in healthy rats, and after 2 months of a wash-out period. Our findings revealed downregulation of hyaluronan (HA) and chondroitin sulphate proteoglycans throughout the body, significantly increased bile acids in blood samples in weeks 4 and 7 of the 4MU treatment, as well as increased blood sugars and proteins a few weeks after 4MU administration, and significantly increased interleukins IL10, IL12p70 and IFN gamma after 10 weeks of 4MU treatment. These effects, however, were reversed and no significant difference was observed between control treated and 4MU-treated animals after a 9-week wash-out period.

Hyaluronan in the Cancer Cells Microenvironment

The presence of the glycosaminoglycan hyaluronan in the extracellular matrix of tissues is the result of the cooperative synthesis of several resident cells, that is, macrophages and tumor and stromal cells. Any change in hyaluronan concentration or dimension leads to a modification in stiffness and cellular response through receptors on the plasma membrane. Hyaluronan has an effect on all cancer cell behaviors, such as evasion of apoptosis, limitless replicative potential, sustained angiogenesis, and metastasis. It is noteworthy that hyaluronan metabolism can be dramatically altered by growth factors and matrikines during inflammation, as well as by the metabolic homeostasis of cells. The regulation of HA deposition and its dimensions are pivotal for tumor progression and cancer patient prognosis. Nevertheless, because of all the factors involved, modulating hyaluronan metabolism could be tough. Several commercial drugs have already been described as potential or effective modulators; however, deeper investigations are needed to study their possible side effects. Moreover, other matrix molecules could be identified and targeted as upstream regulators of synthetic or degrading enzymes. Finally, co-cultures of cancer, fibroblasts, and immune cells could reveal potential new targets among secreted factors.

Structural and Functional Deviations of the Hippocampus in Schizophrenia and Schizophrenia Animal Models

Schizophrenia is a grave neuropsychiatric disease which frequently onsets between the end of adolescence and the beginning of adulthood. It is characterized by a variety of neuropsychiatric abnormalities which are categorized into positive, negative and cognitive symptoms. Most therapeutical strategies address the positive symptoms by antagonizing D2-dopamine-receptors (DR). However, negative and cognitive symptoms persist and highly impair the life quality of patients due to their disabling effects. Interestingly, hippocampal deviations are a hallmark of schizophrenia and can be observed in early as well as advanced phases of the disease progression. These alterations are commonly accompanied by a rise in neuronal activity. Therefore, hippocampal formation plays an important role in the manifestation of schizophrenia. Furthermore, studies with animal models revealed a link between environmental risk factors and morphological as well as electrophysiological abnormalities in the hippocampus. Here, we review recent findings on structural and functional hippocampal abnormalities in schizophrenic patients and in schizophrenia animal models, and we give an overview on current experimental approaches that especially target the hippocampus. A better understanding of hippocampal aberrations in schizophrenia might clarify their impact on the manifestation and on the outcome of this severe disease.