Matrix metalloproteinase-9 is required for hippocampal late-phase long-term potentiation and memory

Integrated multi-omics analysis reveals immunovascular mechanisms of the placenta-maternal brain axis and lifespan neurobehavior changes in a mouse model of preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy, among the leading global drivers of maternal morbidity. PE can precipitate neuropsychiatric risk, including for peripartum anxiety, depression, and cognitive problems. To investigate mechanisms underlying psycho-obstetric risk in PE, we examined maternal metabolic, placental, brain, and behavioral changes in our chronic vasopressin (AVP) infusion PE mouse model (C57Bl6/J). Elevated maternal AVP secretion predicts PE in humans, and chronic AVP administration is sufficient to phenocopy immune, obstetric, and renal phenotypes of PE in pregnant mice. Late-pregnancy metabolomics (N = 4-6/condition/tissue) revealed no significant disruptions in plasma, but 33 changed metabolites were changed in AVP mouse placenta, implicating altered protein, energy, and nutrient functions. Placental RNA sequencing (RNA-seq; N = 3/condition) revealed 140 differentially expressed genes (DEGs), with pathway analyses highlighting changes in structural and metabolic remodeling. Placental multi-omic integration (RNA-seq and metabolomics) identified altered purine metabolism. Analysis of RNA-seq-predicted placental secretome suggested altered immunovascular factors (e.g., C2cd4, Klk1b1). In late-gestation maternal brain, RNA-seq (N = 3/condition) revealed extensive gene suppression in the hypothalamic paraventricular nucleus (PVN, 329 DEGs; 322 down-regulated) and frontal cortex (114 DEGs; 113 down-regulated), implicating altered signaling and immune-vascular pathways, respectively. AVP increased antepartum exploratory behavior without changing depressive-like or hedonic behaviors. Spatial memory deficits in aged postpartum AVP dams were also significant and associated with molecular changes in the hippocampus. Overall, the AVP model of PE induces placental and maternal brain changes, invoking immune and vascular mechanisms. This work identifies potential mechanisms underlying PE impacts on maternal brain, with implications for associated mental health challenges.

BBB proteomic analysis reveals that complex febrile seizures in infancy enhance susceptibility to epilepsy in adulthood through dysregulation of ECM-receptor interaction signaling pathway

BACKGROUND

Complex febrile seizures (CFS) have been associated with an increased risk of epilepsy in adulthood. However, the specific link between blood-brain barrier (BBB) and the predisposition to epilepsy in adults who experienced CFS during infancy remains unclear. The objective of this study was to investigate the alteration of BBB in adult mice who had experienced CFS during infancy, and to explore the mechanisms of increased susceptibility to epilepsy after CFS.

METHODS

The CFS pup model was induced using hot air, and the seizure susceptibility was examined using low-dose pentylenetetrazole (PTZ) after 8 W. The brain microvessels representing BBB function were isolated and their protein expression changes were analyzed using data-independent acquisition (DIA) proteomic techniques. Subsequently, the bioinformatic analyses were performed using ClusterProfiler, STRING, Gene Set Enrichment Analysis (GSEA), etc. The enriched pathways, changes in the expression of BBB-related proteins, and alterations in metabolites including certain neurotransmitters were subsequently validated by Western Blotting, quantitative real-time polymerase chain reaction (qRT-PCR), and mass spectrometric imaging (MSI). In addition, we selected the MMP inhibitor Incyclinide to verify that dysregulation of the ECM-receptor interaction signaling pathway increases epilepsy susceptibility in adult mice.

RESULTS

Mice that experienced CFS in infancy show increased susceptibility to epilepsy in adulthood, and BBB proteomic profile was significantly altered in the CFS mice. The network analysis suggests that dysregulation of the extracellular matrix (ECM)-receptor interaction pathway is a key mechanism. Moreover, MSI analysis uncovered notable changes in differential metabolites, including amino acids and nucleotide-derived neurotransmitters associated with the function of BBB maintaining neuronal homeostasis. Subsequent validation experiments showed that dysregulation of the ECM-receptor interaction signaling pathway exacerbated epilepsy susceptibility in adult mice.

CONCLUSION

Our research represents the pioneering demonstration of the modified BBB proteomics associated with epilepsy susceptibility in adult mice previously exposed to CFS in infancy. Notably, the increased susceptibility is attributed to the dysregulation of the ECM-receptor interaction pathway. These findings may help to elucidate the role of BBB alterations in the progression of epilepsy susceptibility, and provide new orientations for subsequent prevention and treatment of epilepsy.

MMP-2/9 inhibition modulates sharp wave abundance, inhibitory proteoglycan sulfation, and fear memory in juvenile zebrafish: relevance to affective disorders

Sharp wave ripple (SWR) events, present in diverse species, spontaneously occur in the hippocampus during quiescent restfulness and slow-wave sleep. SWRs comprise a negative deflection, the sharp wave (SW) event with an often-superimposed ripple (R) and are the neural correlates of memory consolidation and recall. The Anterodorsolateral lobe (ADL) (zebrafish hippocampal homolog) exhibits SW and SWR events, and since SWs initiate SWRs, their abundance typically shows the same directionality. In previous work, we observed matrix metalloproteinase-9 (MMP-9)-dependent effects on depression-relevant behaviors, perineuronal net (PNN) levels, and SWR abundance in the adult rodent hippocampus. Here, we investigate MMP-2/9-dependent effects on biochemical, behavioral, and neurophysiological endpoints in juvenile zebrafish and zebrafish at the transition from the late juvenile period to early adulthood. With MMP-2/9 inhibition, juvenile zebrafish showed reduced SW amplitude and abundance together with increased fear memory retention and decreased sociability. Juvenile zebrafish also showed an increased percentage of longer-duration SW events. Except for a reduction in SW amplitude, these changes were not observed at the transition from late juvenile to early adulthood. These changes were accompanied by increased levels of chondroitin sulfate (CS) proteoglycan 4-O-sulfation, which modulates PNNs and excitatory-to-inhibitory (E/I) balance. Discontinuation of MMP-2/9 inhibition in juvenile zebrafish normalized deficits in ADL SW abundance and sociability. Together, these findings show that MMP-2/9 significantly influences E/I balance and learning and memory during the highly plastic juvenile period. Findings also have relevance to an emerging appreciation of PNN changes that may contribute to altered neuronal oscillations and mood or cognition.

Selenium deficiency impedes maturation of parvalbumin interneurons, perineuronal nets, and neural network activity

Selenoproteins are fundamental players in redox signaling that are essential for proper brain development and function. They are indispensable for the vitality of GABAergic parvalbumin-expressing interneurons (PVIs), a cell type characterized by fast-spiking activity and heightened rates of metabolism. During development, PVIs are preferentially encapsulated by specialized extracellular matrix structures, termed perineuronal nets (PNNs), which serve to stabilize synaptic structure and act as protective barriers against redox insults. Consequently, alterations in PVIs and PNNs are well chronicled in neuropsychiatric disease, and evidence from animal models indicates that redox imbalance during adolescence impedes their maturation. Herein, we examined the influence of selenium on maturation of neural network structure and activity in primary cortical cultures. Cultures grown in selenium-deficient media exhibited reduced antioxidant activity, impaired PNN formation, and decreased synaptic input onto PVIs at 28 days in vitro, which coincided with increased oxidative stress. Parallel studies to monitor longitudinal maturation of in vitro electrophysiological activity were conducted using microelectrode arrays (MEA). Selenium content affected the electrophysiological profile of developing cultures, as selenium-deficient cultures exhibited impairments in long-term potentiation in conjunction with reduced spike counts for both network bursts and in response to stimulation. Finally, similar PNN deficits were observed in the cortex of mice raised on a selenium-deficient diet, providing corroborative evidence for the importance of selenium in PNN development. In sum, these findings show the vital role of selenium for the development of GABAergic inhibitory circuits.

MMP-2/9 inhibition modulates sharp wave abundance, inhibitory proteoglycan sulfation, and fear memory in juvenile zebrafish: relevance to affective disorders

Sharp wave ripple (SWR) events, present in diverse species, spontaneously occur in the hippocampus during quiescent restfulness and slow-wave sleep. SWRs comprise a negative deflection, the sharp wave (SW) event with an often-superimposed ripple (R) and are the neural correlates of memory consolidation and recall. The Anterodorsolateral lobe (ADL) (zebrafish hippocampal homologue) exhibits SW and SWR events, and since SWs initiate SWRs, their abundance typically shows the same directionality. In previous work, we observed matrix metalloproteinase-9 (MMP-9)-dependent effects on depression-relevant behaviors, perineuronal net (PNN) levels, and SWR abundance in the adult rodent hippocampus. Here, we investigate MMP-2/9-dependent effects on biochemical, behavioral, and neurophysiological endpoints in juvenile zebrafish and zebrafish at the transition from the late juvenile period to early adulthood. With MMP-2/9 inhibition, juvenile zebrafish showed reduced SW amplitude and abundance together with increased fear memory retention and reduced sociability. Juvenile zebrafish also showed an increased percentage of longer-duration SW events. Except for a reduction in SW amplitude, these changes were not observed at the transition from late juvenile to early adulthood. These changes were accompanied by increased levels of chondroitin sulfate (CS) proteoglycan 4- O -sulfation, which modulates PNNs and excitatory-to-inhibitory (E/I) balance. Discontinuation of MMP-2/9 inhibition in juvenile zebrafish normalized deficits in ADL SW abundance and sociability. Together, these findings show that MMP-2/9 significantly influences E/I balance and learning and memory during the highly plastic juvenile period in zebrafish. Findings also have relevance to an emerging appreciation of PNN changes that may contribute to altered neuronal oscillations and mood or cognition.

The Role of Perineuronal Nets in Physiology and Disease: Insights from Recent Studies

Perineuronal nets (PNNs) are specialized extracellular matrix structures that predominantly surround inhibitory neurons in the central nervous system (CNS). They have been identified as crucial regulators of synaptic plasticity and neuronal excitability. This literature review aims to summarize the current state of knowledge about PNNs, their molecular composition and structure, as well as their functional roles and involvement in neurological diseases. Furthermore, future directions in PNN research are proposed, and the therapeutic potential of targeting PNNs to develop novel treatment options for various neurological disorders is explored. This review emphasizes the importance of PNNs in CNS physiology and pathology and underscores the need for further research in this area.

Forget me not: The effect of doxycycline on human declarative memory

Investigations into neuroprotective drugs are in high demand for the treatment of neurodegenerative diseases, such as multiple sclerosis or Alzheimer's disease, but also psychiatric disorders, such as depression, trauma, and substance use. One potential drug class being investigated are tetracyclines impacting on a variety of neuroprotective mechanisms. At the same time, tetracyclines like doxycycline have been suggested to affect human fear and spatial memory as well as reducing declarative memory retention. Based on the assumed necessity for synaptic consolidation in hippocampus-dependent learning, we hypothesised declarative memory may be similarly impaired by doxycycline as fear and spatial memory. Therefore, in this study we investigate the potential diminishing effects of doxycycline on consolidation of declarative memory in healthy humans. Additionally, to test for effect specificity we assessed motor memory, sustained attention, and processing speed. We administered a neuropsychological test battery in three independent randomized placebo-controlled double-blind trials (RCTs), in which healthy young volunteers (total N = 252) either received a single oral dose doxycycline (200 mg, n = 126) or placebo (n = 126) in a between-subject design. We found no evidence for a detrimental effect of doxycycline on declarative memory; instead, doxycycline improved declarative learning (p-value=0.022, Cohen's d=0.15) and memory consolidation (p=0.040, d=0.26). Contrarily, doxycycline slightly reduced motor learning (p=0.001, d=0.10) but subtly strengthened long-term motor memory (p=0.001, d=0.10). These results suggest that doxycycline can improve declarative learning and memory without having long term negative effects on other cognitive domains in healthy humans. Our results give hope to further investigate doxycycline in neuroprotective treatment applications.

Evaluation of MMP-9 enzyme in drug-induced suicide cases admitted to the emergency room

OBJECTIVE

This study investigates MMP-9 enzyme levels in patients who attempted suicide by taking high doses of drugs, considering their sociodemographic characteristics.

METHODS

The study included 45 patients who attempted suicide by high-dose drug intake admitted to the emergency room and 45 healthy volunteers with no neuropsychiatric disorders. Blood samples were collected to measure MMP-9 levels, and informed consent was obtained. The samples were centrifuged and analyzed using the ELISA method, with results statistically compared.

RESULTS

Findings indicate that being single and a student significantly increased suicide tendencies (p = 0.002 and p = 0.001, respectively). Psychiatric disorders were the most common cause at 40.0%, followed by antidepressants (55.6%), analgesics (20.0%), and antidiabetics (8.9%) as the most used drugs for suicide. MMP-9 levels were significantly higher in patients who attempted suicide compared to controls (83.74 (±7.14) ng/mL vs. 54.97 (±12.27) ng/mL, p = 0.001). Additionally, MMP-9 levels were higher in single patients compared to married or divorced individuals (p = 0.008). MMP-9 levels were lower in patients with psychiatric disorders, recent psychiatric services, family history of psychiatric disorders, and previous suicide attempts (p = 0.014, p = 0.046, p = 0.035, p = 0.034).

CONCLUSIONS

This study shows MMP-9 enzyme can be a potential biomarker for drug-induced suicide attempts, emphasizing the importance of evaluating MMP-9 levels to assess suicide risk and develop prevention strategies.

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.

Biological significance and pathophysiological role of Matrix Metalloproteinases in the Central Nervous System

Matrix Metalloproteinases (MMPs), which are endopeptidase reliant on zinc, are low in embryonic tissues but increases in response to a variety of physiological stimulus and pathological stresses. Neuro-glial cells, endothelial cells, fibroblasts, and leucocytes secrete MMPs, which cleave extracellular matrix proteins in a time-dependent manner. MMPs affect synaptic plasticity and the development of short-term memory by controlling the size, shape, and excitatory synapses' function through the lateral diffusion of receptors. In addition, MMPs influence the Extracellular Matrix proteins in the Peri-Neuronal Net at the Neuro-glial interface, which aids in the establishment of long-term memory. Through modulating neuronal, and glial cells migration, differentiation, Neurogenesis, and survival, MMPs impact brain development in mammals. In adult brains, MMPs play a beneficial role in physiological plasticity, which includes learning, memory consolidation, social interaction, and complex behaviors, by proteolytically altering a wide variety of factors, including growth factors, cytokines, receptors, DNA repair enzymes, and matrix proteins. Additionally, stress, depression, addiction, hepatic encephalopathy, and stroke may all have negative effects on MMPs. In addition to their role in glioblastoma development, MMPs influence neurological diseases such as epilepsy, schizophrenia, autism spectrum disorder, brain damage, pain, neurodegeneration, and Alzheimer's and Parkinson's. To help shed light on the potential of MMPs as a therapeutic target for neurodegenerative diseases, this review summarizes their regulation, mode of action, and participation in brain physiological plasticity and pathological damage. Finally, by employing different MMP-based nanotools and inhibitors, MMPs may also be utilized to map the anatomical and functional connectome of the brain, analyze its secretome, and treat neurodegenerative illnesses.

Input specificity of NMDA-dependent GABAergic plasticity in the hippocampus

Sensory experiences and learning induce long-lasting changes in both excitatory and inhibitory synapses, thereby providing a crucial substrate for memory. However, the co-tuning of excitatory long-term potentiation (eLTP) or depression (eLTD) with the simultaneous changes at inhibitory synapses (iLTP/iLTD) remains unclear. Herein, we investigated the co-expression of NMDA-induced synaptic plasticity at excitatory and inhibitory synapses in hippocampal CA1 pyramidal cells (PCs) using a combination of electrophysiological, optogenetic, and pharmacological approaches. We found that inhibitory inputs from somatostatin (SST) and parvalbumin (PV)-positive interneurons onto CA1 PCs display input-specific long-term plastic changes following transient NMDA receptor activation. Notably, synapses from SST-positive interneurons consistently exhibited iLTP, irrespective of the direction of excitatory plasticity, whereas synapses from PV-positive interneurons predominantly showed iLTP concurrent with eLTP, rather than eLTD. As neuroplasticity is known to depend on the extracellular matrix, we tested the impact of metalloproteinases (MMP) inhibition. MMP3 blockade interfered with GABAergic plasticity for all inhibitory inputs, whereas MMP9 inhibition selectively blocked eLTP and iLTP in SST-CA1PC synapses co-occurring with eLTP but not eLTD. These findings demonstrate the dissociation of excitatory and inhibitory plasticity co-expression. We propose that these mechanisms of plasticity co-expression may be involved in maintaining excitation-inhibition balance and modulating neuronal integration modes.

Matrix metalloproteinase-9: A magic drug target in neuropsychiatry?

Neuropsychiatric conditions represent a major medical and societal challenge. The etiology of these conditions is very complex and combines genetic and environmental factors. The latter, for example, excessive maternal or early postnatal inflammation, as well as various forms of psychotrauma, often act as triggers leading to mental illness after a prolonged latent period (sometimes years). Matrix metalloproteinase-9 (MMP-9) is an extracellularly and extrasynaptic operating protease that is markedly activated in response to the aforementioned environmental insults. MMP-9 has also been shown to play a pivotal role in the plasticity of excitatory synapses, which, in its aberrant form, has repeatedly been implicated in the etiology of mental illness. In this conceptual review, we evaluate the experimental and clinical evidence supporting the claim that MMP-9 is uniquely positioned to be considered a drug target for ameliorating the adverse effects of environmental insults on the development of a variety of neuropsychiatric conditions, such as schizophrenia, bipolar disorder, major depression, autism spectrum disorders, addiction, and epilepsy. We also identify specific challenges and bottlenecks hampering the translation of knowledge on MMP-9 into new clinical treatments for the conditions above and suggest ways to overcome these barriers.

Oral Administration of Probiotic Bifidobacterium breve Ameliorates Tonic-Clonic Seizure in a Pentylenetetrazole-Induced Kindling Mouse Model via Integrin-Linked Kinase Signaling

Epilepsy is a chronic neurological disorder characterized by recurrent seizures that affects over 70 million people worldwide. Although many antiepileptic drugs that block seizures are available, they have little effect on preventing and curing epilepsy, and their side effects sometimes lead to serious morbidity. Therefore, prophylactic agents with anticonvulsant properties and no adverse effects need to be identified. Recent studies on probiotic administration have reported a variety of beneficial effects on the central nervous system via the microbiota-gut-brain axis. In this study, we investigated the effects of the oral administration of Bifidobacterium breve strain A1 [MCC1274] (B. breve A1) on tonic-clonic seizure in a pentylenetetrazole (PTZ)-induced kindling mouse (KD mouse) model. We found that the oral administration of B. breve A1 every other day for 15 days significantly reduced the seizure score, which gradually increased with repetitive injections of PTZ in KD mice. The administration of B. breve A1, but not saline, to KD mice significantly increased the level of Akt Ser473 phosphorylation (p-Akt) in the hippocampus; this increase was maintained for a minimum of 24 h after PTZ administration. Treatment of B. breve A1-administered KD mice with the selective inhibitor of integrin-linked kinase (ILK) Cpd22 significantly increased the seizure score and blocked the antiepileptic effect of B. breve A1. Moreover, Cpd22 blocked the B. breve A1-induced increase in hippocampal p-Akt levels. These results suggest that the ILK-induced phosphorylation of Akt Ser473 in the hippocampus might be involved in the antiepileptic effect of B. breve A1.

Perineuronal Nets in the Rat Medial Prefrontal Cortex Alter Hippocampal-Prefrontal Oscillations and Reshape Cocaine Self-Administration Memories

The medial prefrontal cortex (mPFC) is a major contributor to relapse to cocaine in humans and to reinstatement in rodent models of cocaine use disorder. The output from the mPFC is potently modulated by parvalbumin (PV)-containing fast-spiking interneurons, the majority of which are surrounded by perineuronal nets. We previously showed that treatment with chondroitinase ABC (ABC) reduced the consolidation and reconsolidation of a cocaine conditioned place preference memory. However, self-administration memories are more difficult to disrupt. Here we report in male rats that ABC treatment in the mPFC attenuated the consolidation and blocked the reconsolidation of a cocaine self-administration memory. However, reconsolidation was blocked when rats were given a novel, but not familiar, type of retrieval session. Furthermore, ABC treatment prior to, but not after, memory retrieval blocked reconsolidation. This same treatment did not alter a sucrose memory, indicating specificity for cocaine-induced memory. In naive rats, ABC treatment in the mPFC altered levels of PV intensity and cell firing properties. In vivo recordings from the mPFC and dorsal hippocampus (dHIP) during the novel retrieval session revealed that ABC prevented reward-associated increases in high-frequency oscillations and synchrony of these oscillations between the dHIP and mPFC. Together, this is the first study to show that ABC treatment disrupts reconsolidation of the original memory when combined with a novel retrieval session that elicits coupling between the dHIP and mPFC. This coupling after ABC treatment may serve as a fundamental signature for how to disrupt reconsolidation of cocaine memories and reduce relapse.

Overexpression of Motopsin, an Extracellular Serine Protease Related to Intellectual Disability, Promotes Adult Neurogenesis and Neuronal Responsiveness in the Dentate Gyrus

Motopsin, a serine protease encoded by PRSS12, is secreted by neuronal cells into the synaptic clefts in an activity-dependent manner, where it induces synaptogenesis by modulating Na+/K+-ATPase activity. In humans, motopsin deficiency leads to severe intellectual disability and, in mice, it disturbs spatial memory and social behavior. In this study, we investigated mice that overexpressed motopsin in the forebrain using the Tet-Off system (DTG-OE mice). The elevated agrin cleavage or the reduced Na+/K+-ATPase activity was not detected. However, motopsin overexpression led to a reduction in spine density in hippocampal CA1 basal dendrites. While motopsin overexpression decreased the ratio of mature mushroom spines in the DG, it increased the ratio of immature thin spines in CA1 apical dendrites. Female DTG-OE mice showed elevated locomotor activity in their home cages. DTG-OE mice showed aberrant behaviors, such as delayed latency to the target hole in the Barnes maze test and prolonged duration of sniffing objects in the novel object recognition test (NOR), although they retained memory comparable to that of TRE-motopsin littermates, which normally express motopsin. After NOR, c-Fos-positive cells increased in the dentate gyrus (DG) of DTG-OE mice compared with that of DTG-SO littermates, in which motopsin overexpression was suppressed by the administration of doxycycline, and TRE-motopsin littermates. Notably, the numbers of doublecortin- and 5-bromo-2'-deoxyuridine-labeled cells significantly increased in the DG of DTG-OE mice, suggesting increased adult neurogenesis. Importantly, our results revealed a new function in addition to modulating neuronal responsiveness and spine morphology in the DG: the regulation of neurogenesis.

Synaptic cell adhesion molecules contribute to the pathogenesis and progression of fragile X syndrome

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and a monogenic cause of autism spectrum disorders. Deficiencies in the fragile X messenger ribonucleoprotein, encoded by the FMR1 gene, lead to various anatomical and pathophysiological abnormalities and behavioral deficits, such as spine dysmorphogenesis and learning and memory impairments. Synaptic cell adhesion molecules (CAMs) play crucial roles in synapse formation and neural signal transmission by promoting the formation of new synaptic contacts, accurately organizing presynaptic and postsynaptic protein complexes, and ensuring the accuracy of signal transmission. Recent studies have implicated synaptic CAMs such as the immunoglobulin superfamily, N-cadherin, leucine-rich repeat proteins, and neuroligin-1 in the pathogenesis of FXS and found that they contribute to defects in dendritic spines and synaptic plasticity in FXS animal models. This review systematically summarizes the biological associations between nine representative synaptic CAMs and FMRP, as well as the functional consequences of the interaction, to provide new insights into the mechanisms of abnormal synaptic development in FXS.

Exploring the Role of MMP-9 and MMP-9/TIMP-1 Ratio in Subacute Stroke Recovery: A Prospective Observational Study

Despite the significant changes that unfold during the subacute phase of stroke, few studies have examined recovery abilities during this critical period. As neuroinflammation subsides and tissue degradation diminishes, the processes of neuroplasticity and angiogenesis intensify. An important factor in brain physiology and pathology, particularly neuroplasticity, is matrix metalloproteinase 9 (MMP-9). Its activity is modulated by tissue inhibitors of metalloproteinases (TIMPs), which impede substrate binding and activity by binding to its active sites. Notably, TIMP-1 specifically targets MMP-9 among other matrix metalloproteinases (MMPs). Our present study examines whether MMP-9 may play a beneficial role in psychological functions, particularly in alleviating depressive symptoms and enhancing specific cognitive domains, such as calculation. It appears that improvements in depressive symptoms during rehabilitation were notably linked with baseline MMP-9 plasma levels (r = -0.36, p = 0.025), and particularly so with the ratio of MMP-9 to TIMP-1, indicative of active MMP-9 (r = -0.42, p = 0.008). Furthermore, our findings support previous research demonstrating an inverse relationship between pre-rehabilitation MMP-9 serum levels and post-rehabilitation motor function. Crucially, our study emphasizes a positive correlation between cognition and motor function, highlighting the necessity of integrating both aspects into rehabilitation planning. These findings demonstrate the potential utility of MMP-9 as a prognostic biomarker for delineating recovery trajectories and guiding personalized treatment strategies for stroke patients during the subacute phase.

The impact of doxycycline on human contextual fear memory

RATIONALE

 Previous work identified an attenuating effect of the matrix metalloproteinase (MMP) inhibitor doxycycline on fear memory consolidation. This may present a new mechanistic approach for the prevention of trauma-related disorders. However, so far, this has only been unambiguously demonstrated in a cued delay fear conditioning paradigm, in which a simple geometric cue predicted a temporally overlapping aversive outcome. This form of learning is mainly amygdala dependent. Psychological trauma often involves the encoding of contextual cues, which putatively necessitates partly different neural circuits including the hippocampus. The role of MMP signalling in the underlying neural pathways in humans is unknown.

METHODS

Here, we investigated the effect of doxycycline on configural fear conditioning in a double-blind placebo-controlled randomised trial with 100 (50 females) healthy human participants.

RESULTS

Our results show that participants successfully learned and retained, after 1 week, the context-shock association in both groups. We find no group difference in fear memory retention in either of our pre-registered outcome measures, startle eye-blink responses and pupil dilation. Contrary to expectations, we identified elevated fear-potentiated startle in the doxycycline group early in the recall test, compared to the placebo group.

CONCLUSION

Our results suggest that doxycycline does not substantially attenuate contextual fear memory. This might limit its potential for clinical application.

Cotransplantation of NSCs and ethyl stearate promotes synaptic plasticity in PD rats by Drd1/ERK/AP-1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine views kidney shortage as a significant contributor to the aetiology of Parkinson's disease (PD), a neurodegenerative condition that is closely linked to aging. In clinical, patients with Parkinson's disease are often treated with Testudinis Carapax et Plastrum (Plastrum Testudinis, PT), a traditional Chinese medication that tonifies the kidney. Previous research has demonstrated that ethyl stearate (PubChem CID: 8122), an active component of Plastrum Testudinis Extracted with ethyl acetate (PTE), may encourage neural stem cells (NSCs) development into dopaminergic (DAergic) neurons. However, the effectiveness and mechanism of cotransplantation of ethyl stearate and NSCs in treating PD model rats still require further investigation.

AIM OF THE STUDY

PD is a neurodegenerative condition marked by the loss and degradation of dopaminergic neurons in the substantia nigra of the midbrain. Synaptic damage is also a critical pathology in PD. Because of their self-renewal, minimal immunogenicity, and capacity to differentiate into dopaminergic (DAergic) neurons, NSCs are a prospective treatment option for Parkinson's disease cell transplantation therapy. However, encouraging transplanted NSCs to differentiate into dopaminergic neurons and enhancing synaptic plasticity in vivo remains a significant challenge in improving the efficacy of NSCs transplantation for PD. This investigation seeks to examine the efficacy of cotransplantation of NSCs and ethyl stearate in PD model rats and its mechanism related to synaptic plasticity.

MATERIALS AND METHODS

On 6-hydroxydopamine-induced PD model rats, we performed NSCs transplantation therapy and cotransplantation therapy involving ethyl stearate and NSCs. Rotating behavior induced by apomorphine (APO) and pole climbing tests were used to evaluate behavioral changes. Using a variety of methods, including Western blotting (WB), immunofluorescence analysis, enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction (qRT-PCR), we examined the function and potential molecular mechanisms of ethyl stearate in combined NSCs transplantation therapy.

RESULTS

In the rat PD model, cotransplantation of ethyl stearate with NSCs dramatically reduced motor dysfunction, restored TH protein levels, and boosted dopamine levels in the striatum, according to our findings. Furthermore, the expression levels of SYN1 and PSD95, markers of synaptic plasticity, and BDNF, closely related to synaptic plasticity, were significantly increased. Cotransplantation with ethyl stearate and NSCs also increased the expression levels of Dopamine Receptor D1 (Drd1), an important receptor in the dopamine neural circuit, accompanied by an increase in MMP9 levels, ERK1/2 phosphorylation levels, and c-fos protein levels.

CONCLUSIONS

According to the results of our investigation, cotransplantation of ethyl stearate and NSCs significantly improves the condition of PD model rats. We found that cotransplantation of ethyl stearate and NSCs may promote the expression of MMP9 by regulating the Drd1-ERK-AP-1 pathway, thus improving synaptic plasticity after NSCs transplantation. These findings provide new experimental support for the treatment of PD with the kidney tonifying Chinese medicine Plastrum Testudinis and suggest a potential therapeutic strategy for PD based on cotransplantation therapy.

Fear conditioning and extinction distinctively alter bidirectional synaptic plasticity within the amygdala of an animal model of post-traumatic stress disorder

Synaptic plasticity in the amygdala plays an essential role in the formation and inhibition of fear memory; however, this plasticity has mainly been studied in the lateral amygdala, making it largely uninvestigated in other subnuclei. Here, we investigated long-term potentiation (LTP) and long-term depression (LTD) in the basolateral amygdala (BLA) to the medial division of the central amygdala (CEm) synapses of juvenile C57BL/6N (B6) and 129S1/SvImJ (S1) mice. We found that in naïve B6 and S1 mice, LTP was not induced at the BLA to CEm synapses, whereas fear conditioning lowered the threshold for LTP induction in these synapses of both B6 and S1 mice. Interestingly, fear extinction disrupted the induction of LTP at the BLA to CEm synapses of B6 mice, whereas LTP was left intact in S1 mice. Both low-frequency stimulation (LFS) and modest LFS (mLFS) induced LTD in naïve B6 and S1 mice, suggesting that the BLA to CEm synapses express bidirectional plasticity. Fear conditioning disrupted both types of LTD induction selectively in S1 mice and LFS-LTD, presumably NMDAR-dependent LTD was partially recovered by fear extinction. However, mLFS-LTD which has been known to be endocannabinoid receptor 1 (CB1R)-dependent was not induced after fear extinction in both mouse strains. Our observations suggest that fear conditioning enhances LTP while fear extinction diminishes LTP at the BLA to the CEm synapses of B6 mice with successful extinction. Considering that S1 mice showed strong fear conditioning and impaired extinction, strong fear conditioning in the S1 strain may be related to disrupted LTD, and impaired extinction may be due to constant LTP and weak LFS-LTD at the BLA to CEm synapses. Our study contributes to the further understanding of the dynamics of synaptic potentiation and depression between the subnuclei of the amygdala in juvenile mice after fear conditioning and extinction.

BDNF signaling requires Matrix Metalloproteinase-9 during structural synaptic plasticity

Synaptic plasticity underlies learning and memory processes as well as contributes, in its aberrant form, to neuropsychiatric disorders. One of its major forms is structural long-term potentiation (sLTP), an activity-dependent growth of dendritic spines that harbor excitatory synapses. The process depends on the release of brain-derived neurotrophic factor (BDNF), and activation of its receptor, TrkB. Matrix metalloproteinase-9 (MMP-9), an extracellular protease is essential for many forms of neuronal plasticity engaged in physiological as well as pathological processes. Here, we utilized two-photon microscopy and two-photon glutamate uncaging to demonstrate that MMP-9 activity is essential for sLTP and is rapidly (~seconds) released from dendritic spines in response to synaptic stimulation. Moreover, we show that either chemical or genetic inhibition of MMP-9 impairs TrkB activation, as measured by fluorescence lifetime imaging microscopy of FRET sensor. Furthermore, we provide evidence for a cell-free cleavage of proBDNF into mature BDNF by MMP-9. Our findings point to the autocrine mechanism of action of MMP-9 through BDNF maturation and TrkB activation during sLTP.

More than a small adult brain: Lessons from chemotherapy-induced cognitive impairment for modelling paediatric brain disorders

Childhood is recognised as a period of immense physical and emotional development, and this, in part, is driven by underlying neurophysiological transformations. These neurodevelopmental processes are unique to the paediatric brain and are facilitated by augmented rates of neuroplasticity and expanded neural stem cell populations within neurogenic niches. However, given the immaturity of the developing central nervous system, innate protective mechanisms such as neuroimmune and antioxidant responses are functionally naïve which results in periods of heightened sensitivity to neurotoxic insult. This is highly relevant in the context of paediatric cancer, and in particular, the neurocognitive symptoms associated with treatment, such as surgery, radio- and chemotherapy. The vulnerability of the developing brain may increase susceptibility to damage and persistent symptomology, aligning with reports of more severe neurocognitive dysfunction in children compared to adults. It is therefore surprising, given this intensified neurocognitive burden, that most of the pre-clinical, mechanistic research focuses exclusively on adult populations and extrapolates findings to paediatric cohorts. Given this dearth of age-specific research, throughout this review we will draw comparisons with neurodevelopmental disorders which share comparable pathways to cancer treatment related side-effects. Furthermore, we will examine the unique nuances of the paediatric brain along with the somatic systems which influence neurological function. In doing so, we will highlight the importance of developing in vitro and in vivo paediatric disease models to produce age-specific discovery and clinically translatable research.

How dendritic spines shape is determined by MMP-9 activity in FXS

Matrix metalloproteinase-9 (MMP-9) belongs to the family of endopeptidases expressed in neurons and secreted at the synapse in response to neuronal activity. It regulates the pericellular environment by cleaving its protein components. MMP9 is involved in activity-dependent reorganization of spine architecture. In the mouse model of fragile X syndrome (FXS), the most common inherited intellectual disability and the most common single-gene cause of autism, increased synaptic expression of MMP-9 is responsible for the observed dendritic spine abnormalities. In this chapter, I summarize the current data on the molecular regulatory pathways responsible for synaptic MMP-9 expression and discuss the fact that MMP-9 is extracellularly localized, making it a particularly attractive potential target for therapeutic pharmacological intervention in FXS.

The role of integrin beta in schizophrenia: a preliminary exploration

Integrins are transmembrane heterodimeric (αβ) receptors that transduce mechanical signals between the extracellular milieu and the cell in a bidirectional manner. Extensive research has shown that the integrin beta (β) family is widely expressed in the brain and that they control various aspects of brain development and function. Schizophrenia is a relatively common neurological disorder of unknown etiology and has been found to be closely related to neurodevelopment and neurochemicals in neuropathological studies of schizophrenia. Here, we review literature from recent years that shows that schizophrenia involves multiple signaling pathways related to neuronal migration, axon guidance, cell adhesion, and actin cytoskeleton dynamics, and that dysregulation of these processes affects the normal function of neurons and synapses. In fact, alterations in integrin β structure, expression and signaling for neural circuits, cortex, and synapses are likely to be associated with schizophrenia. We explored several aspects of the possible association between integrin β and schizophrenia in an attempt to demonstrate the role of integrin β in schizophrenia, which may help to provide new insights into the study of the pathogenesis and treatment of schizophrenia.

MMP-9 plasma level as biomarker of cochlear implantation outcome in cohort study of deaf children

PURPOSE

If before cochlear implantation it was possible to assay biomarkers of neuroplasticity, we might be able to identify those children with congenital deafness who, later on, were at risk of poor speech and language rehabilitation outcomes.

METHODS

A group of 40 children aged up to 2 years with DFNB1-related congenital deafness was observed in this prospective cohort study over three follow-up intervals (0, 8, and 18 months) after cochlear implant (CI) activation. Children were assessed for auditory development using the LittlEARS Questionnaire (LEAQ) score, and at the same time, measurements were made of matrix metalloproteinase-9 (MMP-9) plasma levels.

RESULTS

There were significant negative correlations between plasma levels of MMP-9 at 8-month follow-up and LEAQ score at cochlear implantation (p = 0.04) and LEAQ score at 18-month follow-up (p = 0.02) and between MMP-9 plasma levels at 18-month follow-up and LEAQ score at cochlear implantation (p = 0.04). As already reported, we confirmed a significant negative correlation between MMP-9 plasma level at cochlear implantation and LEAQ score at 18-month follow-up (p = 0.005). Based on this latter correlation, two clusters of good and poor CI performers could be isolated.

CONCLUSIONS

The study shows that children born deaf who have an MMP-9 plasma level of less than 150 ng/ml at cochlear implantation have a good chance of attaining a high LEAQ score after 18 months of speech and language rehabilitation. This indicates that MMP-9 plasma level at cochlear implantation is a good prognostic marker for CI outcome.

Nicotine's effect on cognition, a friend or foe?

Tobacco smoking is a preventable cause of morbidity and mortality throughout the world. Smoking comes in form of absorption of many compounds, among which nicotine is the main psychoactive component of tobacco and its positive and negative reinforcement effects are proposed to be the key mechanism for the initiation and maintenance of smoking. Growing evidence suggests that the cognitive enhancement effects of nicotine may also contribute to the difficulty of quitting smoking, especially in individuals with psychiatric disorders. In this review, we first introduce the beneficial effect of nicotine on cognition including attention, short-term memory and long-term memory. We next summarize the beneficial effect of nicotine on cognition under pathological conditions, including Alzheimer's disease, Parkinson's disease, Schizophrenia, Stress-induced Anxiety, Depression, and drug-induced memory impairment. The possible mechanism underlying nicotine's effect is also explored. Finally, nicotine's detrimental effect on cognition is discussed, including in the prenatal and adolescent periods, and high-dose nicotine- and withdrawal-induced memory impairment is emphasized. Therefore, nicotine serves as both a friend and foe. Nicotine-derived compounds could be a promising strategy to alleviate neurological disease-associated cognitive deficit, however, due to nicotine's detrimental effect, continued educational programs and public awareness campaigns are needed to reduce tobacco use among pregnant women and smoking should be quitted even if it is e-cigarette, especially for the adolescents.

Exploring brain glutathione and peripheral blood markers in posttraumatic stress disorder: a combined [1H]MRS and peripheral blood study

Introduction

Oxidative stress has been implicated in psychiatric disorders, including posttraumatic stress disorder (PTSD). Currently, the status of glutathione (GSH), the brain's most abundant antioxidant, in PTSD remains uncertain. Therefore, the current study investigated brain concentrations of GSH and peripheral concentrations of blood markers in individuals with PTSD vs. Healthy Controls (HC).

Methods

GSH spectra was acquired in the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC) using MEGA-PRESS, a J-difference-editing acquisition method. Peripheral blood samples were analyzed for concentrations of metalloproteinase (MMP)-9, tissue inhibitors of MMP (TIMP)-1,2, and myeloperoxidase (MPO).

Results

There was no difference in GSH between PTSD and HC in the ACC (n = 30 PTSD, n = 20 HC) or DLPFC (n = 14 PTSD, n = 18 HC). There were no group differences between peripheral blood markers (P > 0.3) except for (non-significantly) lower TIMP-2 in PTSD. Additionally, TIMP-2 and GSH in the ACC were positively related in those with PTSD. Finally, MPO and MMP-9 were negatively associated with duration of PTSD.

Conclusions

We do not report altered GSH concentrations in the ACC or DLPFC in PTSD, however, systemic MMPs and MPO might be implicated in central processes and progression of PTSD. Future research should investigate these relationships in larger sample sizes.

Circulating Serum VEGF, IGF-1 and MMP-9 and Expression of Their Genes as Potential Prognostic Markers of Recovery in Post-Stroke Rehabilitation-A Prospective Observational Study

The key period in post-stroke recovery is the first three months due to the high activity of spontaneous and therapeutic-induced processes related to neuroplasticity, angiogenesis and reperfusion. Therefore, the present study examines the expression of VEGF, IGF-1 and MMP-9 proteins and their genes to identify biomarkers that can prognose brain repair ability and thus estimate the outcome of stroke. It also identifies possible associations with clinical scales, including cognitive assessment and depression scales. The study group comprised 32 patients with moderate ischemic stroke severity, three to four weeks after incident. The results obtained after three-week hospitalization indicate a statistically significant change in clinical parameter estimations, as well as in MMP9 and VEGF protein and mRNA expression, over the rehabilitation process. Our findings indicate that combined MMP9 protein and mRNA expression might be a useful biomarker for cognitive improvement in post-stroke patients, demonstrating 87% sensitivity and 71% specificity (p < 0.0001).

A shift in the mechanisms controlling hippocampal engram formation during brain maturation

The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of precise, episodic-like memory are unclear. In mice, the absence of a competitive neuronal engram allocation process in the immature hippocampus precluded the formation of sparse engrams and precise memories until the fourth postnatal week, when inhibitory circuits in the hippocampus mature. This age-dependent shift in precision of episodic-like memories involved the functional maturation of parvalbumin-expressing interneurons in subfield CA1 through assembly of extracellular perineuronal nets, which is necessary and sufficient for the onset of competitive neuronal allocation, sparse engram formation, and memory precision.

Sex differences in synaptic plasticity underlying learning

Although sex differences in learning behaviors are well documented, sexual dimorphism in the synaptic processes of encoding is only recently appreciated. Studies in male rodents have built upon the discovery of long-term potentiation (LTP), and acceptance of this activity-dependent increase in synaptic strength as a mechanism of encoding, to identify synaptic receptors and signaling activities that coordinate the activity-dependent remodeling of the subsynaptic actin cytoskeleton that is critical for enduring potentiation and memory. These molecular substrates together with other features of LTP, as characterized in males, have provided an explanation for a range of memory phenomena including multiple stages of consolidation, the efficacy of spaced training, and the location of engrams at the level of individual synapses. In the present report, we summarize these findings and describe more recent results from our laboratories showing that in females the same actin regulatory mechanisms are required for hippocampal LTP and memory but, in females only, the engagement of both modulatory receptors such as TrkB and synaptic signaling intermediaries including Src and ERK1/2 requires neuron-derived estrogen and signaling through membrane-associated estrogen receptor α (ERα). Moreover, in association with the additional ERα involvement, females exhibit a higher threshold for hippocampal LTP and spatial learning. We propose that the distinct LTP threshold in females contributes to as yet unappreciated sex differences in information processing and features of learning and memory.

Muscarinic Cholinergic Receptor Antagonism Impairs Spatial Memory Retrieval and Minimizes Retrieval-Induced Alterations in Matrix Metalloproteinase-9

Cholinergic dysfunction in the hippocampus causes memory impairment, and degradation of the forebrain cholinergic system has been implicated in several neurological disorders. One such disorder, Alzheimer's Disease (AD) is associated with the abnormal expression of various proteins including matrix metalloproteinase-9 (MMP-9), an enzyme known to regulate hippocampus-dependent memory. Memory involves several stages including acquisition, consolidation, and retrieval, but the neurobiological correlates of retrieval have been studied much less than other stages of memory. We sought to investigate the potential relationship between cholinergic signaling and hippocampal MMP-9 expression and the involvement of each in spatial memory retrieval. We trained rats in the water maze until the task was well-learned, then, seven days later, we allowed some to retrieve the memory after an intracerebroventricular injection of scopolamine or vehicle. Western blot analysis of hippocampal tissue shows elevated levels of a truncated form of MMP-9 associated with spatial memory retrieval. Additionally, our results indicate that centrally administered scopolamine both impairs spatial memory retrieval and prevents retrieval-induced elevations in MMP-9. These findings provide evidence for a potential link between cholinergic dysregulation and abnormal MMP-9 levels seen in the brains of AD patients. An important, yet unresolved question is whether MMP-9 serves to support memory retrieval itself or if it is involved in maintaining the ongoing stability of a retrieved memory.

Environmental conditions of recognition memory testing induce neurovascular changes in the hippocampus in a sex-specific manner in mice

Experiences are linked to emotions impacting memory consolidation and associated brain neuronal circuits. Posttraumatic stress disorder is an example of strong negative emotions affecting memory processes by flashbacks of past traumas. Stress-related memory deficits are also observed in major depressive disorder (MDD). We recently highlighted that sex-specific blood-brain barrier (BBB) alterations underlie stress responses in mice and human depression. However, little is known about the relationship between emotional valence, memory encoding and BBB gene expression. Here, we investigated the effects of novel object recognition (NOR) test, an experience considered of neutral emotional valence, on BBB properties in dorsal vs ventral hippocampus (HIPP) in the context of various environmental conditions (arena size, handling, age). The HIPP is a brain area central for learning and memory processes with the dorsal and ventral subregions being associated with working memory vs reference memory retrieval, respectively. Expression of genes related to BBB integrity are altered in line with learning and memory processes in a region- and sex-specific manner. We observed correlations between poor learning, anxiety, stress-induced corticosterone release and changes in BBB-associated gene expression. Comparison of BBB transcriptomes between sexes also revealed profound differences at baseline in both ventral and dorsal HIPP. Finally, we identified circulating vascular biomarkers, such as sE-selectin and matrix metallopeptidase 9 (MMP-9), altered following NOR exposure supporting that recognition memory formation has an impact on the neurovasculature. Although deemed as a neutral valence test, NOR experimental conditions can shift it toward a negative valence, impacting performance and highlighting the need to minimize anxiety when performing this commonly used test in mice.

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.

Matrix metalloproteinase-9 overexpression in the hippocampus reduces alcohol-induced conditioned-place preference by regulating synaptic plasticity in mice

Extracellular matrix proteins appear to be necessary for the synaptic plasticity that underlies addiction memory. In the brain, matrix metalloproteinases (MMPs), especially matrix metalloproteinase-9 (MMP-9), have been recently implicated in processes involving alcohol reward and memory. Here, we showed for the first time, the positive effects of MMP-9 on alcohol-induced conditioned place preference (CPP) behavior and hippocampal neuron plasticity in C57BL/6 mice. Using recombinant adeno-associated viruses to overexpress MMP-9 in the hippocampus, we investigated the NMDAR, PSD-95, and cellular cytoskeleton proteins F-actin/G-actin in the modulation of alcohol reward behavior in mice exposed to CPP. We found that hippocampal infusions of MMP-9 decreased alcohol-induced place preference suggesting a reduction in alcohol reward. Western blot analysis demonstrated that protein expression of NMDA receptors (GluN1, GluN2A and GluN2B) in the hippocampus of alcohol-exposed mice were higher than that of the saline group. Further, the expression of these proteins was decreased in MMP-9 overexpressing mice. MMP-9 also regulated the ratio of F-actin/G-actin (dendritic spines cytoskeleton proteins), which might be the key mediator for behavioral changes in mice. Consequently, our results highlight new evidence that MMP-9 may play an important role in the molecular mechanism underlying alcohol reward and preference.

Extracellular zinc regulates contextual fear memory formation in male rats through MMP-BDNF-TrkB pathway in dorsal hippocampus and basolateral amygdala

Large amount of zinc (100 µM even up to 300 µM) is released from the nerve terminals in response to high frequency neuronal stimulation in certain brain regions including hippocampus and amygdala. However, its precise pharmacological effect is poorly understood. Here, we investigated the role of extracellular zinc (endogenous zinc) and exogenous zinc in memory formation using contextual fear conditioning (CFC) model. Male Sprague Dawley rats were trained for fear conditioning followed by in vivo microdialysis for collection of microdialysate samples from CA1 and CA3 regions of hippocampus and basolateral amygdala (BLA). Extracellular zinc chelator CaEDTA, BDNF scavenger TrkB-Fc, exogenous 7,8-DHF and matrix metalloproteinases (MMP) inhibitor were infused into the CA1 and CA3 regions of hippocampus and BLA after CFC. Different doses of exogenous zinc hydroaspartate were administered intraperitoneally immediately after CFC. We found that CFC increased the level of extracellular zinc in the hippocampus and BLA. Infusing the CaEDTA, TrkB-Fc and MMP inhibitor into the CA1 and CA3 regions of hippocampus and BLA disrupted the fear memory formation. Furthermore, administration of TrKB agonist 7,8-DHF reversed the inhibitory effect of CaEDTA on fear memory formation, suggesting that extracellular zinc may regulate fear memory formation via the BDNF-TrKB pathway. We also found that high dose of exogenous zinc hydroaspartate supplementation increased extracellular zinc levels in brain and enhanced fear memory formation. Altogether, these findings indicate that extracellular zinc may participate in formation of contextual fear memory through MMP-BDNF-TrkB pathway in the hippocampus and BLA.

Longitudinal Changes in BDNF and MMP-9 Protein Plasma Levels in Children after Cochlear Implantation

Congenitally deaf children who undergo cochlear implantation before 1 year of age develop their auditory skills faster than children who are implanted later. In this longitudinal study, a cohort of 59 implanted children were divided into two subgroups according to their ages at implantation-below or above 1 year old-and the plasma levels of matrix metalloproteinase-9 (MMP-9), brain-derived neurotrophic factor (BDNF), and pro-BDNF were measured at 0, 8, and 18 months after cochlear implant activation, while auditory development was simultaneously evaluated using the LittlEARs Questionnaire (LEAQ). A control group consisted of 49 age-matched healthy children. We identified statistically higher BDNF levels at 0 months and at the 18-month follow-ups in the younger subgroup compared to the older one and lower LEAQ scores at 0 months in the younger subgroup. Between the subgroups, there were significant differences in the changes in BDNF levels from 0 to 8 months and in LEAQ scores from 0 to 18 months. The MMP-9 levels significantly decreased from 0 to 18 months and from 0 to 8 months in both subgroups and from 8 to 18 months only in the older one. For all measured protein concentrations, significant differences were identified between the older study subgroup and the age-matched control group.

Long-Term Neuromodulatory Effects of Repetitive Transcranial Magnetic Stimulation (rTMS) on Plasmatic Matrix Metalloproteinases (MMPs) Levels and Visuospatial Abilities in Mild Cognitive Impairment (MCI)

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation technique that is used against cognitive impairment in mild cognitive impairment (MCI) and Alzheimer's disease (AD). However, the neurobiological mechanisms underlying the rTMS therapeutic effects are still only partially investigated. Maladaptive plasticity, glial activation, and neuroinflammation, including metalloproteases (MMPs) activation, might represent new potential targets of the neurodegenerative process and progression from MCI to AD. In this study, we aimed to evaluate the effects of bilateral rTMS over the dorsolateral prefrontal cortex (DLPFC) on plasmatic levels of MMP1, -2, -9, and -10; MMPs-related tissue inhibitors TIMP1 and TIMP2; and cognitive performances in MCI patients. Patients received high-frequency (10 Hz) rTMS (MCI-TMS, n = 9) or sham stimulation (MCI-C, n = 9) daily for four weeks, and they were monitored for six months after TMS. The plasmatic levels of MMPs and TIMPs and the cognitive and behavioral scores, based on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Beck Depression Inventory II, Beck Anxiety Inventory, and Apathy Evaluation Scale, were assessed at baseline (T0) and after 1 month (T1) and 6 months (T2) since rTMS. In the MCI-TMS group, at T2, plasmatic levels of MMP1, -9, and -10 were reduced and paralleled by increased plasmatic levels of TIMP1 and TIMP2 and improvement of visuospatial performances. In conclusion, our findings suggest that targeting DLPFC by rTMS might result in the long-term modulation of the MMPs/TIMPs system in MCI patients and the neurobiological mechanisms associated with MCI progression to dementia.

Effect of the Matrix Metalloproteinase Inhibitor Doxycycline on Human Trace Fear Memory

Learning to predict threat is of adaptive importance, but aversive memory can also become disadvantageous and burdensome in clinical conditions such as posttraumatic stress disorder (PTSD). Pavlovian fear conditioning is a laboratory model of aversive memory and thought to rely on structural synaptic reconfiguration involving matrix metalloproteinase (MMP)9 signaling. It has recently been suggested that the MMP9-inhibiting antibiotic doxycycline, applied before acquisition training in humans, reduces fear memory retention after one week. This previous study used cued delay fear conditioning, in which predictors and outcomes overlap in time. However, temporal separation of predictors and outcomes is common in clinical conditions. Learning the association of temporally separated events requires a partly different neural circuitry, for which the role of MMP9 signaling is not yet known. Here, we investigate the impact of doxycycline on long-interval (15 s) trace fear conditioning in a randomized controlled trial with 101 (50 females) human participants. We find no impact of the drug in our preregistered analyses. Exploratory post hoc analyses of memory retention suggested a serum level-dependent effect of doxycycline on trace fear memory retention. However, effect size to distinguish CS+/CS- in the placebo group turned out to be smaller than in previously used delay fear conditioning protocols, which limits the power of statistical tests. Our results suggest that doxycycline effect on trace fear conditioning in healthy individuals is smaller and less robust than anticipated, potentially limiting its clinical application potential.

Brain matrix metalloproteinase-9 activity is altered in the corticosterone mouse model of depression

Major depressive disorder is a highly prevalent psychiatric condition. Metalloproteinase 9 (MMP-9), a gelatinase involved in synaptic plasticity, learning and memory processes, is elevated in both chronic stress animal models and human peripheral blood samples of depressed patients. In this study we have evaluated the MMP-9 activity and protein expression in brain areas relevant to depression using the chronic corticosterone mouse model of depression. These mice show a depressive- and anxious-like behaviour. The MMP-9 activity and protein levels are significantly elevated in both the hippocampus and the cortex, and nectin-3 levels are lower in these brain areas in this model. In particular, these mice display an increased gelatinase activity in the CA1 and CA3 subfields of the hippocampus and in the internal layer of the prefrontal cortex. Moreover, the immobility time in the tail suspension test presents a positive correlation with the cortical MMP-9 activity, and a negative correlation with nectin-3 levels. In conclusion, the chronic corticosterone model of depression leads to an increase in the protein expression and activity of MMP-9 and a reduction of its substrate nectin-3 in relevant areas implicated in this disease. The MMP-9 activity correlates with behavioural despair in this model of depression. All these findings support the role of MMP-9 in the pathophysiology of depression, and as a putative target to develop novel antidepressant drugs.

Extracellular matrix and synapse formation

The extracellular matrix (ECM) is a complex molecular network distributed throughout the extracellular space of different tissues as well as the neuronal system. Previous studies have identified various ECM components that play important roles in neuronal maturation and signal transduction. ECM components are reported to be involved in neurogenesis, neuronal migration, and axonal growth by interacting or binding to specific receptors. In addition, the ECM is found to regulate synapse formation, the stability of the synaptic structure, and synaptic plasticity. Here, we mainly reviewed the effects of various ECM components on synapse formation and briefly described the related diseases caused by the abnormality of several ECM components.

Electrophysiology of Dendritic Spines: Information Processing, Dynamic Compartmentalization, and Synaptic Plasticity

For many years, synaptic transmission was considered as information transfer between presynaptic neuron and postsynaptic cell. At the synaptic level, it was thought that dendritic arbors were only receiving and integrating all information flow sent along to the soma, while axons were primarily responsible for point-to-point information transfer. However, it is important to highlight that dendritic spines play a crucial role as postsynaptic components in central nervous system (CNS) synapses, not only integrating and filtering signals to the soma but also facilitating diverse connections with axons from many different sources. The majority of excitatory connections from presynaptic axonal terminals occurs on postsynaptic spines, although a subset of GABAergic synapses also targets spine heads. Several studies have shown the vast heterogeneous morphological, biochemical, and functional features of dendritic spines related to synaptic processing. In this chapter (adding to the relevant data on the biophysics of spines described in Chap. 1 of this book), we address the up-to-date functional dendritic characteristics assessed through electrophysiological approaches, including backpropagating action potentials (bAPs) and synaptic potentials mediated in dendritic and spine compartmentalization, as well as describing the temporal and spatial dynamics of glutamate receptors in the spines related to synaptic plasticity.

Promoting Effect and Potential Mechanism of Lactobacillus pentosus LPQ1-Produced Active Compounds on the Secretion of 5-Hydroxytryptophan

5-hydroxytryptophan (5-HTP) is an important substance thought to improve depression. It has been shown that Lactobacillus can promote the secretion of 5-HTP in the body and thus ameliorate depression-like behavior in mice. However, the mechanism by which Lactobacillus promotes the secretion of 5-HTP is unclear. In this study, we investigated the promoting effect and mechanism of Lactobacillus, isolated from Chinese fermented foods, on the secretion of 5-HTP. The results showed that Lactobacillus (L.) pentosus LPQ1 exhibited the strongest 5-HTP secretion-promoting effect ((9.44 ± 0.69)-fold), which was dependent on the mixture of compounds secreted by L. pentosus LPQ1 (termed SLPQ1). In addition, the results of the RNA sequencing (RNA-seq) and quantitative real-time polymerase chain reaction (qRT-PCR) analyses indicated that SLPQ1 alters the TNF and oxidative phosphorylation signaling pathways. Moreover, the SLPQ1 ultrafiltration fraction (>10 kDa) showed a similar 5-HTP promoting effect as SLPQ1. Furthermore, reverse-phase liquid chromatography-tandem mass spectrometry (RPLC-MS/MS) identified 29 compounds of >10 kDa in SLPQ1, including DUF488 domain-containing protein, BspA family leucine-rich repeat surface protein, and 30S ribosomal protein S5, which together accounted for up to 62.51%. This study reports new findings on the mechanism by which L. pentosus LPQ1 promotes 5-HTP production in some cell lines in vitro.

Effects of uridine administration on hippocampal matrix metalloproteinases and their endogenous inhibitors in REM sleep-deprived rats

Rapid eye movement (REM) sleep is associated with synaptic plasticity which is considered essential for long-term potentiation (LTP). The composition of extracellular matrix (ECM), in part, plays a role in REM sleep-associated synaptic functioning. The objective of this study was to investigate the effects of uridine administration on levels of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) in rats subjected to REM sleep deprivation (REMSD). REMSD was induced by modified multiple platform method for 96-hour. Rats were randomized to receive either saline or uridine (1 mmol/kg) intraperitoneally twice a day for four days. Rats were then decapitated and their hippocampi were dissected for analyzing the levels of MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2 and TIMP-3 by Western-blotting and the activities of MMP-2 and MMP-9 by Gelatin zymography. REMSD resulted in reduced levels of MMP-3, MMP-9, TIMP-3 and activity of MMP-9 in saline-treated rats, while uridine treatment significantly enhanced their impairment. TIMP-1 was enhanced following REMSD but uridine treatment had no significant effect on TIMP-1 levels. MMP-2, TIMP-2 levels and MMP-2 activity were not affected by either REMSD or uridine administration. These data show that REMSD significantly affects ECM composition which is ameliorated by uridine administration suggesting a possible use of uridine in sleep disorders.

Elevated Matrix Metalloproteinase 9 in Treatment Resistant Bipolar Depression

Objective: Matrix metalloproteinase is a family of proteases with different pathophysiological roles. Matrix metalloproteinase 9 (MMP9) plays an enzymatic role in the restructuring of the extracellular matrix and adhesion molecules. MMP9 is upregulated in pro-inflammatory states and leads to breakdown of tight junctions thereby increasing blood-brain barrier (BBB) permeability. MMP9 may contribute to the pathophysiology of bipolar disorder (BD) via proteolysis of the BBB thus allowing entry of cytokines and neurotoxic agents into CNS. Polymorphisms of the MMP9 gene may pose increased risk for BD and schizophrenia. In this study we sought to determine MMP9 levels in treatment resistant bipolar depressed patients before and after treatment. Methods: Treatment resistant bipolar depressed patients were treated with escitalopram, in combination with the COX-2 inhibitor, celecoxib. It was hypothesized that combination treatment would reverse resistance and augmented treatment responses. This was a 10-week, randomized, double-blind, two-arm, placebo-controlled study. Results: MMP9 levels were higher in bipolar depressed patients compared to healthy controls at baseline, however, the difference did not reach significance. Levels decreased after treatment reaching significance in the escitalopram plus placebo group. Female patients had significantly lower MMP9 levels at end of treatment. MMP9 was higher in carriers the MMP9 SNP, rs3918242, than in noncarriers, but the difference did not reach statistical significance. Conclusion: MMP9 decreased in bipolar depressed patients with treatment. Age, sex and the rs3918242 polymorphism play a role in MMP9 levels. Future studies should confirm the role of MMP9 in the pathogenesis and pathophysiology of bipolar disorder, as a potential diagnostic biomarker.

Matrixmetalloproteinase-9 gene polymorphism (rs 17576) increases the risk of depressive symptoms in bipolar disorder

Objectives

Plasticity of neural synapses is known to be involved in the complications in bipolar disorder (BD) patients. Matrix metalloproteinases (MMPs) play a role in synaptic plasticity and memory. Even though elevated MMP-9 levels are reported in neuropsychiatric disorders, there is limited data about MMP-9 gene polymorphism in BD. The objectives of the study was to investigate genotype frequency and allele frequency of MMP-9 genetic variant (rs 17576) in BD and its association with disease severity.

Materials and Methods

Eighty BD cases and 80 controls were recruited in the study. MMP-9 genotyping and allele frequency and plasma MMP-9 levels were analyzed in both the groups. Hamilton depression rating scale and Young's Mania Rating Scale (YMRS) were used to evaluate severity of BD.

Results

The genotype and minor allele (G allele) frequency were not significant between BD and controls. MMP-9 levels were significantly increased in BD patients with AG (P < 0.001) and GG (P = 0.022) genotypes compared to controls. BD patients with GG genotype (P = 0.038, OR: 3.26 (1.16-9.09), and G (mutant) allele (P = 0.013, OR 2.03(1.18-3.48) confer increased risk of depressive symptoms. MMP-9 was positively correlated with YMRS scale (r = 0.227, P = 0.043) in BD.

Conclusion

MMP-9 gene polymorphism (rs 17576) is linked with depressive symptoms in BD.

The emerging role of furin in neurodegenerative and neuropsychiatric diseases

Furin is an important mammalian proprotein convertase that catalyzes the proteolytic maturation of a variety of prohormones and proproteins in the secretory pathway. In the brain, the substrates of furin include the proproteins of growth factors, receptors and enzymes. Emerging evidence, such as reduced FURIN mRNA expression in the brains of Alzheimer's disease patients or schizophrenia patients, has implicated a crucial role of furin in the pathophysiology of neurodegenerative and neuropsychiatric diseases. Currently, compared to cancer and infectious diseases, the aberrant expression of furin and its pharmaceutical potentials in neurological diseases remain poorly understood. In this article, we provide an overview on the physiological roles of furin and its substrates in the brain, summarize the deregulation of furin expression and its effects in neurodegenerative and neuropsychiatric disorders, and discuss the implications and current approaches that target furin for therapeutic interventions. This review may expedite future studies to clarify the molecular mechanisms of furin deregulation and involvement in the pathogenesis of neurodegenerative and neuropsychiatric diseases, and to develop new diagnosis and treatment strategies for these diseases.

A central alarm system that gates multi-sensory innate threat cues to the amygdala

Perception of threats is essential for survival. Previous findings suggest that parallel pathways independently relay innate threat signals from different sensory modalities to multiple brain areas, such as the midbrain and hypothalamus, for immediate avoidance. Yet little is known about whether and how multi-sensory innate threat cues are integrated and conveyed from each sensory modality to the amygdala, a critical brain area for threat perception and learning. Here, we report that neurons expressing calcitonin gene-related peptide (CGRP) in the parvocellular subparafascicular nucleus in the thalamus and external lateral parabrachial nucleus in the brainstem respond to multi-sensory threat cues from various sensory modalities and relay negative valence to the lateral and central amygdala, respectively. Both CGRP populations and their amygdala projections are required for multi-sensory threat perception and aversive memory formation. The identification of unified innate threat pathways may provide insights into developing therapeutic candidates for innate fear-related disorders.

Induction of A Disintegrin and Metalloproteinase with Thrombospondin motifs 1 by a rare variant or cognitive activities reduces hippocampal amyloid-β and consequent Alzheimer’s disease risk

Amyloid-β (Aβ) derived from amyloid precursor protein (APP) hydrolysis is acknowledged as the predominant hallmark of Alzheimer’s disease (AD) that especially correlates to genetics and daily activities. In 2019, meta-analysis of AD has discovered five new risk loci among which A Disintegrin and Metalloproteinase with Thrombospondin motifs 1 (ADAMTS1) has been further suggested in 2021 and 2022. To verify the association, we re-sequenced ADAMTS1 of clinical AD samples and subsequently identified a novel rare variant c.–2067A > C with watchable relevance (whereas the P-value was not significant after adjustment). Dual-luciferase assay showed that the variant sharply stimulated ADAMTS1 expression. In addition, ADAMTS1 was also clearly induced by pentylenetetrazol-ignited neuronal activity and enriched environment (EE). Inspired by the above findings, we investigated ADAMTS1’s role in APP metabolism in vitro and in vivo. Results showed that ADAMTS1 participated in APP hydrolysis and consequently decreased Aβ generation through inhibiting β-secretase-mediated cleavage. In addition, we also verified that the hippocampal amyloid load of AD mouse model was alleviated by the introduction of ADAMTS1, and thus spatial cognition was restored as well. This study revealed the contribution of ADAMTS1 to the connection of genetic and acquired factors with APP metabolism, and its potential in reducing hippocampal amyloid and consequent risk of AD.

Disrupting interaction between miR-132 and Mmp9 3'UTR improves synaptic plasticity and memory in mice

As microRNAs have emerged to be important regulators of molecular events occurring at the synapses, the new questions about their regulatory effect on the behavior have araised. In the present study, we show for the first time that the dysregulated specific targeting of miR132 to Mmp9 mRNA in the mouse brain results in the increased level of Mmp9 protein, which affects synaptic plasticity and has an effect on memory formation. Our data points at the importance of complex and precise regulation of the Mmp9 level by miR132 in the brain.

SIRT1, MMP-9 and TIMP-1 levels in children with specific learning disorder

BACKGROUND

Specific Learning Disorder (SLD) is a common developmental and neurobiological disorder of childhood characterized by impairment of functionality in one or more areas such as reading, writing, mathematics, listening, speaking, and reasoning. The etiology of SLD is still not fully understood. The aim of this study was to evaluate children with SLD to investigate the potential role of MMP-9, TIMP-1 and SIRT-1, which have important roles in synaptic plasticity, cognitive functions, learning and memory, and are known to be associated with various psychiatric disorders.

METHODS

The study was conducted with 44 outpatients aged 8-14 years who were diagnosed with SLD according to DSM-5 in the outpatient clinic and a control group of 44 age, gender and education level-matched healthy children. The groups were compared in respect of serum levels of MMP-9, TIMP-1 and SIRT-1, evaluated using the ELISA method.

RESULTS

Serum MMP-9 levels were significantly lower in children in the SLD group than in the control group, while TIMP-1 was higher. No difference was determined between the groups in respect of the SIRT1 levels. SLD severity was negatively correlated with MMP-9 levels and positively correlated with TIMP-1 levels.

CONCLUSIONS

MMP-9 appear to contribute to hippocampal-dependent memory and learning by modulating long-term synaptic plasticity. The findings of this study also reinforce the idea that deregulation of the MMP-9/TIMP-1 ratio may impact learning and play a role in SLD. These findings will help to elucidate the etiology of SLD. Furthermore, understanding molecular pathways can contribute to the discovery of certain biomarkers in SLD pathogenesis and the development of new treatment possibilities.