Research progress on the roles of neurovascular unit in stroke-induced immunosuppression. / ç¥žç»è¡€ç®¡å•å ƒä¸Žè„‘æ¢—æ­»åŽå ç–«æŠ‘åˆ¶ç ”ç©¶è¿›å±•.

A complex pathophysiological mechanism is involved in brain injury following cerebral infarction. The neurovascular unit (NVU) is a complex multi-cellular structure consisting of neurons, endothelial cells, pericyte, astrocyte, microglia and extracellular matrix, etc. The dyshomeostasis of NVU directly participates in the regulation of inflammatory immune process. The components of NVU promote inflammatory overreaction and synergize with the overactivation of autonomic nervous system to initiate stroke-induced immunodepression (SIID). SIID can alleviate the damage caused by inflammation, however, it also makes stroke patients more susceptible to infection, leading to systemic damage. This article reviews the mechanism of SIID and the roles of NVU in SIID, to provide a perspective for reperfusion, prognosis and immunomodulatory therapy of cerebral infarction.

Polystyrene nanoplastics aggravated dibutyl phthalate-induced blood-testis barrier dysfunction via suppressing autophagy in male mice.

Nanoplastics (NPs) frequently cause adverse health effects by transporting organic pollutants such as dibutyl phthalate (DBP) into organisms by utilizing their large specific surface area, large surface charge, and increased hydrophobicity. However, the effects of NPs combined with DBP on the reproductive systems of mammals are still unclear. The present investigation involved the administration of polystyrene NPs (PS-NPs) to BALB/c mice via gavage, with a size of 100 nm and at doses of 5 mg/kg/day or 50 mg/kg/day, along with DBP at a dose of 0.5 mg/kg/day, or a combination of PS-NPs and DBP, for 30 days, to assess their potential for reproductive toxicity. The co-exposure of mice to PS-NPs and DBP resulted in a significant increase in reproductive toxicities compared to exposure to PS-NPs or DBP alone. This was demonstrated by a marked decrease in sperm quality, significant impairment of spermatogenesis, and increased disruption of the blood-testis barrier (BTB). Furthermore, a combination of in vivo and in vitro investigations were conducted to determine that the co-exposure of DBP and PS-NPs resulted in a noteworthy reduction in the expressions of tight junction proteins (ZO-1 and occludin). Moreover, the in vitro findings revealed that monobutyl phthalate (MBP, the active metabolite of DBP, 0.5 µg/mL) and PS-NPs (30 µg/mL or 300 µg/mL) inhibited autophagy in Sertoli cells, thereby increasing the expression of matrix metalloproteinases (MMPs). The study found that PS-NPs and DBP co-exposure caused harmful effects in male reproductive organs by disrupting BTB, which may be alleviated by reactivating autophagy. The paper's conclusions provided innovative perspectives on the collective toxicities of PS-NPs and other emerging pollutants.

IGF2 inhibits hippocampal over-activated microglia and alleviates depression-like behavior in LPS- treated male mice.

Over-activated microglia and inflammatory mediators are found in patients with depression, while manipulation of the microglia function might represent a potential therapeutic strategy. Insulin-like growth factor 2 (IGF2) has been implicated in bacterial infections and autoimmune disorders, but the role of IGF2 on the active phenotype of microglia and neuroinflammation has not been well established. IGF2 influences in modulating microglia responding to neuroinflammation induced by lipopolysaccharide（LPS）challenge will be carefully examined. In the current study, we verified that systemic IGF2 treatment could produce an anti-depression effect in LPS-treated mice. Particularly, we found that systemic IGF2 treatment inhibited microglia over-activation and prevented its transformation to a pro-inflammatory phenotype, thereby protecting hippocampal neurogenesis. Since microglia reactive to neuroinflammation is a common feature of neuropsychiatric disorders, the discoveries from the present study may provide therapeutic innovation for these diseases.

Hyperactivation of TRPV4 causes the hippocampal pyroptosis pathway and results in cognitive impairment in LPS-treated mice.

Pyroptosis, a newly discovered proinflammatory programmed cell death, is involved in the regulation of cognitive dysfunction, such as Alzheimer's disease. Exploring potential drug targets that prevent pyroptotic procedures might benefit the development of a cure for these diseases. In the present study, we explored whether the transient receptor potential vanilloid 4 (TRPV4) blocker HC067047 and knockdown of TRPV4 in the hippocampus could improve cognitive behavior through the inhibition of pyroptosis in a mouse model developed using systemic administration of lipopolysaccharide (LPS). We found that systemic administration of HC067047 or knockdown of hippocampal TRPV4 prevented the activation of canonical and noncanonical pyroptosis in the hippocampus of LPS-treated mice. Consistent with the inhibition of the hippocampal pyroptosis pathway, a knockdown of hippocampal TRPV4 lowered expression of TNF-α, IL-1ß, IL-18, and IL-6. Furthermore, we verified that the main pyroptosis cell type might be a neuron, indicated by reduced neuronal marker expression. Mechanically, we also found that knockdown of hippocampal TRPV4 might inhibit phosphorylation of CamkⅡα which results in NFκb mediated inflammasome reduction in the hippocampus of LPS-treated mice. More interestingly, mice intraperitoneally injected with HC067047 or the hippocampus injected with TRPV4 shRNA showed improved cognitive behavior, as indicated by the enhanced discrimination ratio in the NORT, NOPT, and SNPT. Collectively, we consider that HC067047 might be a small molecular drug that prevents pyroptosis, and TRPV4 could be an effective therapeutic target for preventing pyroptosis-induced cognitive dysfunction.

Interleukin-33 regulates the functional state of microglia.

Microglia, the most prominent resident immune cells, exhibit multiple functional states beyond their immunomodulatory roles. Non-immune functions such as synaptic reorganization, removal of cellular debris, and deposition of abnormal substances are mediated by phagocytosis of normal or enhanced microglia. Activation or migration of microglia occurs when environmental cues are altered. In response to pathological factors, microglia change into various phenotypes, preventing or exacerbating tissue damage. Interleukin-33 (IL-33) is an important cytokine that regulates innate immunity, and microglia are thought to be its target cells. Here, we outline the role of IL-33 in the expression of microglial functions such as phagocytosis, migration, activation, and inflammatory responses. We focus on microglial properties and diverse functional states in health and disease, including the different effects of IL-33 perturbation on microglia in vivo and in vitro. We also highlight several well-established mechanisms of microglial function mediated by IL-33, which may be initiators and regulators of microglial function and require elucidation and expansion of the underlying mechanisms.

Molecular mechanisms of programmed cell death in methamphetamine-induced neuronal damage.

Methamphetamine, commonly referred to as METH, is a highly addictive psychostimulant and one of the most commonly misused drugs on the planet. Using METH continuously can increase your risk for drug addiction, along with other health complications like attention deficit disorder, memory loss, and cognitive decline. Neurotoxicity caused by METH is thought to play a significant role in the onset of these neurological complications. The molecular mechanisms responsible for METH-caused neuronal damage are discussed in this review. According to our analysis, METH is closely associated with programmed cell death (PCD) in the process that causes neuronal impairment, such as apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. In reviewing this article, some insights are gained into how METH addiction is accompanied by cell death and may help to identify potential therapeutic targets for the neurological impairment caused by METH abuse.

Contributing Factors and Induced Outcomes of Psychological Stress Response in Stroke Survivors: A Systematic Review.

Background: Remarkable evidence indicates that psychological stress is significantly associated with stroke. However, a uniform recommendation to identify and alleviate poststroke psychological stress responses and improve postmorbid outcomes is not currently available. Thus, this systematic review aimed to summarize the types of poststroke psychological stress, measurement tools, contributing factors, and outcomes. Methods: This systematic review was undertaken in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A literature search was conducted in PubMed, Web of Science, Embase, CNKI, WanFangData, and CQVIP from database inception to November 2021. Cross-sectional and longitudinal studies were included in this research. Quality assessment was performed based on the National Institutes of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Results: Eighteen quantitative, peer-reviewed studies were included for analysis. Selected articles mainly investigated perceived stress and posttraumatic stress disorder after stroke. We classified the contributing factors into four categories: sociodemographic factors, clinical disease factors, psychological factors, and behavioral and lifestyle factors. The postmorbid outcomes were divided into three categories: clinical disease outcomes, psychological outcomes, and behavioral and quality of life outcomes. Conclusions: Compared to common patients, stroke survivors with the following characteristics suffered an increased psychological stress response: younger age, the presence of caregivers, depression, unsuitable coping strategies, etc. Meanwhile, lower quality of life, worse drug compliance, worse functional independence, and more severe mental disorders were significantly associated with increased psychological stress symptoms. Further studies are required to provide more trustworthy and meaningful references for mitigating the damage caused by psychological stress after stroke.

Nrf2 deficiency attenuates atherosclerosis by reducing LOX-1-mediated proliferation and migration of vascular smooth muscle cells.

BACKGROUND AND AIMS: Oxidative stress and abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) influence atherosclerosis formation and development. Oxidative stress significantly influences the abnormal proliferation and migration of VSMCs, and nuclear factor erythroid 2-related factor 2 (Nrf2) is a major antioxidant factor. However, the precise function of Nrf2 in the regulation of abnormal proliferation and migration of VSMCs and atherosclerosis is unclear. METHODS: We investigated the proliferation and migration of VSMCs in atherosclerosis in male Apoe-/- and Apoe-/-Nrf2-/- mice fed a high-fat diet for 12 weeks. In cultured mouse VSMCs, we studied the effect of Nrf2 on ox-LDL-stimulated proliferation and migration by using siRNA treatment to silence Nrf2. We then performed dual luciferase reporter and immunoprecipitation assays to study the interaction between Nrf2 and the promoter sequence of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1). RESULTS: Our results demonstrate that Nrf2 expression levels were increased in the aorta and VSMCs of mice in the atherosclerosis model group compared with the control group. We also provide evidence that Nrf2 deficiency attenuated atherosclerotic plaque burden, diminished proliferation, and migration of VSMCs but enhanced VSMC-specific marker gene expression in vitro and in vivo. This is related to Nrf2 binding to the promoter sequence of LOX-1. Furthermore, Nrf2 downregulation contributes to restrain both transcriptional and translational activities of LOX-1. CONCLUSIONS: Together, our data indicate that Nrf2 insufficiency is linked to attenuation of atherosclerosis, and could diminish the pathological process by blunting LOX-1-mediated proliferation and migration of VSMCs.

Research progress of mesenchymal stem cell-derived exosomes on inflammatory response after ischemic stroke.

Ischemic stroke is characterized by cute onset and high mortality. The suppression of neuroinflammation is crucial in the treatment of ischemic stroke. Exosomes derived from mesenchymal stem cell (MSC) have attracted extensive research attention due to their wide origin, small size, and containing large number of active components. Recent studies have shown that MSC-derived exosomes can inhibit the proinflammatory activity of microglia and astrocytes and stimulate their neuroprotective activity; also can inhibit neuroinflammation by regulating immune cells and inflammatory mediators. This article reviews the roles and related mechanism of MSC-derived exosomes in neuroinflammation after ischemic stroke, hoping to provide ideas and references for the development of a novel approach for the treatment of ischemic stroke diseases.

Ultrastructural clarification of the peripherally located actin network in the myelinated axons / Aclaración ultraestructural de la red de actina localizada periféricamente en los axones mielinizados

SUMMARY: Despite the existence of a large amount of actin in the axons, the concentration F-actin was quite low in the myelinated axons and almost all the F-actin were located in the peripheries of the myelinated axons. Until now, the ultrastructural localization of F-actin has still not been reported in the myelinated axons, probably due to the lack of an appropriate detection method. In the present study, a phalloidin-based FITC-anti-FITC technique was adopted to investigate the subcellular localization of F-actin in the myelinated axons. By using this technique, F-actin is located in the outer and inner collars of myelinated cytoplasm surrounding the intermodal axon, the Schmidt-Lanterman incisures, the paranodal terminal loops and the nodal microvilli. In addition, the satellite cell envelope, which encapsulates the axonal initial segment of the peripheral sensory neuron, was also demonstrated as an F-actin-enriched structure. This study provided a hitherto unreported ultrastructural view of the F-actin in the myelinated axons, which may assist in understanding the unique organization of axonal actin cytoskeleton.

RESUMEN: A pesar de la existencia de una gran cantidad de actina en los axones, la concentración de F-actina era bastante baja en los axones mielinizados y casi la totalidad de F-actina se localizaba en las periferias de los axones mielinizados. A la fecha aún no se ha reportado la localización ultraestructural de F-actina en los axones mielinizados, probablemente debido a la falta de un método de detección apropiado. En el presente estudio, se adoptó una técnica FITC-anti-FITC basada en faloidina para investigar la localización subcelular de F-actina en los axones mielinizados. Mediante el uso de esta técnica, la F-actina se localiza en los collares externo e interno del citoplasma mielinizado que rodea el axón intermodal, a las incisiones de Schmidt-Lanterman,a las asas terminales paranodales y a las microvellosidades nodales. Además, la envoltura de la célula satélite, que encapsula el segmento axonal inicial de la neurona sensorial periférica, también se demostró como una estructura enriquecida con F-actina. Este estudio proporcionó una vista ultraestructural de la F-actina en los axones mielinizados, que puede ayudar a comprender la organización única del citoesqueleto de actina axonal.

The temporal and spatial changes of microtubule cytoskeleton in the CA1 stratum radiatum following global transient ischemia.

The down-regulation of microtubule proteins has been widely documented in the ischemic brain, but the temporal or spatial alteration of microtubules has not been systematically investigated in the vulnerable areas after ischemia. By examining the stability and distribution of microtubules following transient global ischemia, we found that the biomarkers of stable microtubules, MAP2 and acetylated α-tubulin, became significantly down-regulated in the CA1 stratum radiatum of rat hippocampus and that the neuron-specific microtubule protein, class III ß-tubulin, was progressively decreased in the same region. Surprisingly, pan-ß-tubulin, which is expressed at a low level in glial cells under physiological conditions, was significantly increased in reactive astrocytes after ischemia. The finding was supported by protein quantification and confocal microscopy analysis, and consistent with the different vulnerabilities of neuronal and glial cells to the ischemic insult. To our knowledge, the different responses of microtubules between neuronal and glial cells have not been described in the ischemic brain before. The deconstruction of microtubules in the neurons is expected to contribute to the selective and delayed neuronal death in the vulnerable brain regions, while the increased microtubules in the reactive astrocytes may play an important role in the shape conversion of astrocytes induced by ischemia.

The temporal and spatial changes of actin cytoskeleton in the hippocampal CA1 neurons following transient global ischemia.

Transient global ischemia usually results in delayed neuronal death in selective brain regions, prior to which a rapid loss of dendritic spines has been widely reported in these regions. Dendritic spines are characterized by a highly branched meshwork of actin cytoskeleton (F-actin), which is extremely vulnerable to the ATP-depleted conditions such as hypoxia/ischemia. However, the ischemia-induced changes of F-actin are still not clarified in the vulnerable brain areas. This study was designed to examine the temporal and spatial alterations of F-actin in the CA1 subfield of rat hippocampus following reperfusion after global cerebral ischemia. Phalloidin staining and confocal microscopic examination showed that F-actin disappeared from the dentritic spines in the CA1 stratum radiatum, but aggregated into thread- or fiber-like structures on days 1.5-2 after ischemia. This was followed by a nearly complete loss of F-actin in the CA1 subfield on days 3-7 after ischemia. Colocalization analysis demonstrated that the F-actin threads or fibers were located mainly within the dentritic trunks. As revealed by Nissl and Fluoro-Jade B staining, the decrease of F-actin proceeded concurrently with the evolution of ischemic damage. Consistently, western blots detected a significant decrease of F-/G-actin ratio in the dissected CA1 subfield after ischemia. To our knowledge, this is the first report on the change of F-actin in the ischemic brain. Although the underlying mechanisms remain to be elucidated, our findings may provide an important structural clue for the neuronal dysfunction induced by ischemia.

Dexamethasone ameliorates the damage of hippocampal filamentous actin cytoskeleton but is not sufficient to cease epileptogenesis in pilocarpine induced epileptic mice.

Rogressive deconstruction of filament actin (F-actin) in hippocampal neurons in the epileptic brain have been associated with epileptogenesis. Previous clinical studies suggest that glucocorticoids treatment plays beneficial roles in refractory epilepsy. Glucocorticoids treatment affects dendritic spine morphology by regulating local glucocorticoid receptors and F-actin cytoskeleton dynamics. However, how glucocorticoids regulate epileptogenesis by controlling F-actin cytoskeleton is not clear yet. Here we study the function of glucocorticoids in epileptogenesis by examining F-actin abundance, hippocampal neuron number, and synaptic markers in pilocarpine-induced epileptic mice in the presence or absence of dexamethasone (DEX) treatment. We found that spontaneous seizure duration was significantly reduced; F-actin damage in hippocampal subfields was remarkably attenuated; loss of pyramidal cells was dramatically decreased; more intact synaptic structures indicated by pre- and postsynaptic markers were preserved in multiple hippocampal regions after DEX treatment. However, the number of ZNT3 positive particles in the molecular layer in the hippocampus of pilocarpine epileptic mice was not altered after DEX treatment. Although not sufficient to cease epileptogenesis, our results suggest that dexamethasone treatment ameliorates the damage of epileptic brain by stabilizing F-actin cytoskeleton in the pilocarpine epileptic mice.

The effects of epothilone D on microtubule degradation and delayed neuronal death in the hippocampus following transient global ischemia.

Disruption of microtubule cytoskeleton plays an important role during the evolution of brain damage after transient cerebral ischemia. However, it is still unclear whether microtubule-stabilizing drugs such as epothilone D (EpoD) have a neuroprotective action against the ischemia-induced brain injury. This study examined the effects of pre- and postischemic treatment with different doses of EpoD on the microtubule damage and the delayed neuronal death in the hippocampal CA1 subfield on day 2 following reperfusion after 13-min global cerebral ischemia. Our results showed that systemic treatment with 0.5 mg/kg EpoD only slightly alleviated the microtubule disruption and the CA1 neuronal death, while treatment with 3.0 mg/kg EpoD was not only ineffective against the CA1 neuronal death, but also produced additional damage in the dentate gyrus in some ischemic rats. Since the pyramidal cells in the CA1 subfield and the granule neurons in the dentate gyrus are known to be equipped with dynamically different microtubule systems, this finding indicates that the effects of microtubule-disrupting drugs may be unpredictably complicated in the central nervous system.

The effects of calcineurin inhibitor FK506 on actin cytoskeleton, neuronal survival and glial reactions after pilocarpine-induced status epilepticus in mice.

After status epilepticus (SE), actin cytoskeleton (F-actin) becomes progressively deconstructed in the hippocampus, which is consistent with the delayed pyramidal cell death in both time course and spatial distribution. A variety of experiments show that calcineurin inhibitors such as FK506 are able to inhibit the SE-induced actin depolymerization. However, it is still unclear what changes happen to the F-actin in the epileptic brain after FK506 treatment. A pilocarpine model of SE in mice was used to examine the effects of FK506 on the F-actin in the hippocampal neurons. The post SE (PSE) mice with or without FK506 treatment were monitored consecutively for 14 days to examine the frequency and duration of spontaneous seizures. The effects of FK506 on the activity of cofilin and actin dynamics were assessed at 7 and 14 d PSE by western blots. The organization of F-actin, neuronal cell death, and glial reactions were investigated by phalloidin staining, histological and immunocytochemical staining, respectively. As compared to the PSE + vehicle mice, FK506 treatment significantly decreased the frequency and duration of spontaneous seizures. Relative to the PSE + vehicle mice, western blots detected a partial restoration of phosphorylated cofilin and a significant increase of F/G ratio in the hippocampus after FK506 treatment. In the PSE + vehicle mice, almost no F-actin puncta were left in the CA1 and CA3 subfields at 7 and 14 d PSE. FK506-treated PSE mice showed a similar decrease of F-actin, but the extent of damage was significantly ameliorated. Consistently, the surviving neurons became significantly increased in number after FK506 treatment, relative to the PSE + vehicle groups. After FK506 treatment, microglial reaction was partially inhibited, but the expression of GFAP was not significantly changed, compared to the PSE + vehicle mice. The results suggest that post-epileptic treatment with FK506 ameliorated, but could not stop the deconstruction of F-actin or the delayed neuronal loss in the PSE mice.

The unique organization of filamentous actin in the medullary canal of the medulla oblongata.

In the central canal, F-actin is predominantly localized in the apical region, forming a ring-like structure around the circumference of the lumen. However, an exception is found in the medulla oblongata, where the apical F-actin becomes interrupted in the ventral aspect of the canal. To clarify the precise localization of F-actin, the fluorescence signals for F-actin were converted to the peroxidase/DAB reaction products in this study by a phalloidin-based ultrastructural technique, which demonstrated that F-actin is located mainly in the microvilli and terminal webs in the ependymocytes. It is because the ventrally oriented ependymocytes do not possess well-developed microvilli or terminal web that led to a discontinuous labeling of F-actin in the medullary canal. Since spinal motions can change the shape and size of the central canal, we next examined the cytoskeletons in the medullary canal in both rats and monkeys, because these two kinds of animals show different kinematics at the atlanto-occipital articulation. Our results first demonstrated that the apical F-actin in the medullary canal is differently organized in the animals with different head-neck kinemics, which suggests that the mechanic stretching of spinal motions is capable of inducing F-actin reorganization and the subsequent cell-shape changes in the central canal.

The progressive changes of filamentous actin cytoskeleton in the hippocampal neurons after pilocarpine-induced status epilepticus.

In a previous study, we reported a persistent reduction of F-actin puncta but a compensating increase in puncta size in the mouse hippocampus at 2 months after pilocarpine-induced status epilepticus (Epilepsy Res. 108 (2014), 379-389). However, the F-actin changes during the period of epileptogenesis remain unknown. This study was designed to examine the temporal and spatial changes of F-actin during the period of epileptogenesis in a pilocarpine-induced epilepsy model, primarily by the histological and TUNEL evaluation of cell loss, phalloidin detection of F-actin, and immunohistochemical analysis of glial reactions. The results demonstrated that F-actin continued to decrease after pilocarpine treatment, which was consistent in its time course with hippocampal neuronal death. Within different hippocampal subfields, the spatial changes of F-actin exhibited similar features. First, the F-actin puncta decreased in number. Thereafter, F-actin was transiently aggregated in dendritic shafts and neuronal cell bodies and eventually was completely lost in the degenerated neurons. The progressive changes of F-actin in the degenerating neurons reported in this study may help to elucidate a cytoskeletal mechanism that may link to the delayed cell loss that occurs during epileptogenesis.

Contamination of Phenylobacterium in several human and murine cell cultures.

OBJECTIVE: To identify and characterize an unknown microorganism causing contamination in several mammalian cell cultures. METHODS: This bacterium was identified by 16S rRNA sequencing and studied by DAPI and DiOC6 (3) staining, Gram staining, acid-fast staining, and electron microscopy. The isolated bacterium was also used to infect host cells to observe antibiotic effectiveness and its relationship with host cells. RESULTS: The 16S rRNA sequence analysis shows that this rod-shaped microorganism belongs to the family Caulobacteraceae, class Alphaproteobacteria, and was most closely related to Phenylobacterium zucineum HLK1T strain. The bacterium collected in the "swimming" stage was Gram staining negative, but Gram staining positive in the "sessile" stage. Under the electron microscope both flagellated and non-flagellated types were found. So far, no antibiotics were effective to inhibit this microorganism. The contamination with this bacterium frequently led to failed resuscitation of thawed cells. We found that the cells resuscitated with the used culture supernatants were increased in number by 3-4 folds as compared to those resuscitated with freshly prepared media. CONCLUSION: Phenylobacterium may have a dimorphic life cycle including a swimming stage and a sessile stalked stage.

Pilocarpine-induced epilepsy is associated with actin cytoskeleton reorganization in the mossy fiber-CA3 synapses.

Dramatic structural changes have been demonstrated in the mossy fiber-CA3 synapses in the post status epilepticus (SE) animals, suggesting a potential reorganization of filamentous actin (F-actin) network occurring in the hippocampus. However, until now the long-term effects of SE on the synaptic F-actin have still not been reported. In this study, phalloidin labeling combined with confocal microscopy and protein analyses were adopted to investigate the effects of pilocarpine treatment on the F-actin in the C57BL/6 mice. As compared to the controls, there was ∼ 43% reduction in F-actin density in the post SE mice. Quantitative analysis showed that the labeling density and the puncta number were significantly decreased after pilocarpine treatment (p<0.01, n=5 mice per group, Student's t-test). The puncta of F-actin in the post SE group tended to be highly clustered, while those in the controls were generally distributed evenly. The mean puncta size of F-actin puncta was 0.73±0.19µm(2) (n=1102 puncta from 5 SE mice) in the experimental group, significantly larger than that in the controls (0.51±0.10µm(2), n=1983 puncta from 5 aged-matched control mice, p<0.01, Student's t-test). These observations were well consistent with the alterations of postsynaptic densities in the same region, revealed by immunostaining of PSD95, suggesting the reorganization of F-actin occurred mainly postsynaptically. Our results are indicative of important cytoskeletal changes in the mossy fiber-CA3 synapses after pilocarpine treatment, which may contribute to the excessive excitatory output in the hippocampal trisynaptic circuit.

The rearrangement of filamentous actin in mossy fiber synapses in pentylenetetrazol-kindled C57BL/6 mice.

Chemical kindling, as an experimental model of epileptogenesis, is induced by repetitive administration of subconvulsive amount of excitatory drugs. Kindled mice do not typically display spontaneous recurrent seizures, but are instead characterized by enhanced seizure susceptibility to convulsive stimulations. In order to provide insights into the aberrant synaptic plasticity during kindling, this study investigated the effect of pentylenetetrazol (PTZ) kindling on filamentous actin (F-actin) in mossy fiber synapses in C57BL/6 mice. Phalloidin labeling of F-actin showed that F-actin puncta were increased in number in the stratum lucidum of CA3 region in the hippocampus after kindling. The rearrangement of F-actin seemed to occur presynaptically, since synapsin I, a specific marker for mossy fiber terminals, was also up-regulated. Such subtle structural modifications occurring in the synapses are thought to contribute to the long-lasting increased sensitivity in the PTZ-kindled C57BL/6 mice.