Oral P. gingivalis impairs gut permeability and mediates immune responses associated with neurodegeneration in LRRK2 R1441G mice.

BACKGROUND: The R1441G mutation in the leucine-rich repeat kinase 2 (LRRK2) gene results in late-onset Parkinson's disease (PD). Peripheral inflammation and gut microbiota are closely associated with the pathogenesis of PD. Chronic periodontitis is a common type of peripheral inflammation, which is associated with PD. Porphyromonas gingivalis (Pg), the most common bacterium causing chronic periodontitis, can cause alteration of gut microbiota. It is not known whether Pg-induced dysbiosis plays a role in the pathophysiology of PD. METHODS: In this study, live Pg were orally administrated to animals, three times a week for 1 month. Pg-derived lipopolysaccharide (LPS) was used to stimulate mononuclear cells in vitro. The effects of oral Pg administration on the gut and brain were evaluated through behaviors, morphology, and cytokine expression. RESULTS: Dopaminergic neurons in the substantia nigra were reduced, and activated microglial cells were increased in R1441G mice given oral Pg. In addition, an increase in mRNA expression of tumor necrosis factor (TNF-α) and interleukin-1ß (IL-1ß) as well as protein level of α-synuclein together with a decrease in zonula occludens-1 (Zo-1) was detected in the colon in Pg-treated R1441G mice. Furthermore, serum interleukin-17A (IL-17A) and brain IL-17 receptor A (IL-17RA) were increased in Pg-treated R1441G mice. CONCLUSIONS: These findings suggest that oral Pg-induced inflammation may play an important role in the pathophysiology of LRRK2-associated PD.

hUCMSCs Mitigate LPS-Induced Trained Immunity in Ischemic Stroke.

Innate immune memory is a part of the innate immune system that facilitates the elimination of pathogens. However, it may exacerbate neuropathology. In this study, we found that innate immune memory is detrimental in stroke, because it promotes the acute immune response and exacerbates ischemic infarcts. Mesenchymal stem cell therapy has been widely studied for its therapeutic potential in various diseases including stroke, but whether it diminishes innate immune memory has not been studied. Here, our study demonstrates that, after the activation of innate immune memory by lipopolysaccharide, mesenchymal stem cell therapy can diminish innate immune memory though down-regulation of H3 methylation and subsequently protect against stroke. Our results demonstrate that innate immune memory is detrimental in stroke, and we describe a novel potential therapeutic target involving the use of mesenchymal stem cells to treat stroke patients.

Overexpression of Slit2 decreases neuronal excitotoxicity, accelerates glymphatic clearance, and improves cognition in a multiple microinfarcts model.

BACKGROUND: Cerebral microinfarcts (MIs) lead to progressive cognitive impairments in the elderly, and there is currently no effective preventative strategy due to uncertainty about the underlying pathogenic mechanisms. One possibility is the dysfunction of GABAergic transmission and ensuing excitotoxicity. Dysfunction of GABAergic transmission induces excitotoxicity, which contributes to stroke pathology, but the mechanism has kept unknown. The secreted leucine-rich repeat (LRR) family protein slit homologue 2 (Slit2) upregulates GABAergic activity and protects against global cerebral ischemia, but the neuroprotective efficacy of Slit2 against MIs has not been examined. METHODS: Middle-aged Wild type (WT) and Slit2-Tg mice were divided into sham and MI treatment groups. MIs were induced in parietal cortex by laser-evoked arteriole occlusion. Spatial memory was then compared between sham and MI groups using the Morris water maze (MWM) task. In addition, neuronal activity, blood brain barrier (BBB) permeability, and glymphatic clearance in peri-infarct areas were compared using two-photon imaging, while GABAergic transmission, microglial activation, neuronal loss, and altered cortical connectivity were compared by immunofluorescent staining or western blotting. RESULTS: Microinfarcts increased the amplitude and frequency of spontaneous intracellular Ca2+ signals, reduced neuronal survival and connectivity within parietal cortex, decreased the number of GABAergic interneurons and expression of vesicular GABA transporter (VGAT), induced neuroinflammation, and impaired both glymphatic clearance and spatial memory. Alternatively, Slit2 overexpression attenuated dysfunctional neuronal Ca2+ signaling, protected against neuronal death in the peri-infarct area as well as loss of parietal cortex connectivity, increased GABAergic interneuron number and VGAT expression, attenuated neuroinflammation, and improved both glymphatic clearance and spatial memory. CONCLUSION: Our results strongly suggest that overexpression of Slit2 protected against the dysfunction in MIs, which is a potential therapeutic target for cognition impairment in the elderly.

Continuous theta burst stimulation dilates meningeal lymphatic vessels by up-regulating VEGF-C in meninges.

BACKGROUND: Lymphatic vessels (LVs) of meninges and lymphatic drainage in the brain have been investigated previously. Here, we examined the role of continuous theta burst stimulation (CTBS) in the modulation of meningeal LVs. METHODS: To explore the effects of CTBS on meningeal LVs, the diameters of LVs were measured between a real CTBS group and sham CTBS group of wild-type male mice. Vascular endothelial growth factor-C (VEGF-C) expression was subsequently calculated in both groups to account for lymphatic changes after CTBS. Sunitinib was administered by 3-day oral gavage to inhibit the VEGF receptor (VEGFR), and the effects of CTBS were further examined in the following groups: vehicle with real CTBS, vehicle with sham CTBS, sunitinib treatment with real CTBS, and sunitinib treatment with sham CTBS. RESULTS: The lymphatic vessels were augmented, and the level of VEGF-C in meninges increased after CTBS. CTBS dilated meningeal lymphatic vessels were impaired after the VEGF-C/VEGFR3 pathway was blocked. CONCLUSIONS: CTBS can dilate meningeal lymphatic vessels by up-regulating VEGF-C in meninges.

Mesenchymal stem cells alleviate AQP-4-dependent glymphatic dysfunction and improve brain distribution of antisense oligonucleotides in BACHD mice.

Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the huntingtin (HTT) gene that results in the production of neurotoxic mutant HTT (mHTT) protein. Suppressing HTT production with antisense oligonucleotides (ASOs) is a promising treatment strategy for HD; however, the difficulty of delivering ASOs to deep brain structures is a major barrier for its clinical application. The glymphatic system of astrocytes involving aquaporin 4 (AQP-4) controls the entry of macromolecules from the cerebrospinal fluid into the brain. Mesenchymal stem cells (MSCs) target astrocytes to inhibit neuroinflammation. Here we examined the glymphatic distribution of ASO in the brain and the therapeutic potential of combining intravenously injection of mesenchymal stem cells (IV-MSC) and ASOs for the treatment of HD. Our results show that Cy3-labeled ASOs entered the brain parenchyma via the perivascular space following cisternal injection, but the brain distribution was significantly lower in AQP-4-/- as compared with wild-type mice. Downregulation of the AQP-4 M23 isoform was accompanied by decreased brain levels of ASOs in BACHD mice as well as an increase in astrogliosis and phosphorylation of nuclear factor κB (NF-κB) p65. IV-MSC treatment restored AQP-4 M23 expression, attenuated astrogliosis, and decreased NF-κB p65 phosphorylation; it also increased the brain distribution of ASOs and enhanced the suppression of mHTT in BACHD mice. These results suggest that modulating glymphatic activity using IV-MSC is a novel strategy for improving the potency of ASO in the treatment of HD.

Phasic GABA signaling mediates the protective effects of cTBS against cerebral ischemia in mice.

Continuous theta burst stimulation (cTBS) has been widely recognized as a therapeutic treatment for ischemic stroke, but the underlying mechanism is still elusive. Here, we investigated the protective effects of cTBS in the posterior parietal cortex during the chronic phase of stroke in the photothrombotic ischemic model. Infarction volume and neuron excitability in the peri-infarct area were assessed using immunohistochemistry and whole-cell patch-clamp. Spatial cognitive function was measured using the Morris water maze. Gamma-Amino butyric acid (GABA) interneurons were responsive to cTBS, and cTBS induced elevated phasic inhibition rather than tonic inhibition. Given that GABA-A-mediated phasic inhibition was elevated during the chronic phase of ischemic stroke for 30 days and was beneficial for stroke recovery, we investigated the therapeutic potential of cTBS in promoting functional recovery and found that the elevated phasic inhibition by cTBS improved spatial cognitive function in the photothrombotic stroke mouse model with induction in the posterior parietal cortex. Our study indicates the mechanism by which cTBS may modify the excitability of the brain cortex and provides novel insight into the potential of cTBS to protect against neuronal dysfunction in ischemic stroke.

Continuous theta burst stimulation provides neuroprotection by accelerating local cerebral blood flow and inhibiting inflammation in a mouse model of acute ischemic stroke.

Acute ischemic stroke is a leading cause of disability with limited therapeutic options. Continuous theta burst stimulation (cTBS) has recently been shown to be a promising noninvasive therapeutic strategy for neuroprotection in ischemic stroke patients. Here, we investigated the protective effects of cTBS following acute infarction using a photothrombotic stroke (PTS) model in the right posterior parietal cortex (PPC) of C57BL/6 mice. Treatment with cTBS resulted in a reduction in the volume of the infarct region and significantly increased vascular diameter and blood flow velocity in peri-infarct region, as well as decreased the numbers of calcium binding adapter molecule 1 (Iba-1)-positive microglia and glial fibrillary acidic protein (GFAP)-positive astrocytes. Moreover, the number of CD16/32 positive microglia was decreased, whereas the number of CD206 positive microglia was increased. In addition, performance in a water maze task was significantly improved. These results indicated that cTBS protected against PPC infarct region, leading to an improvement in spatial cognitive function, possibly as a result of changes to cerebral microvascular function and inflammatory responses.

Extracellular ASC exacerbated the recurrent ischemic stroke in an NLRP3-dependent manner.

Using a photothrombotic mouse model of single stroke, we show that a single stroke onset increases the nuclear factor-κB (NF-κB), NLR family CARD domain containing protein 4 (NLRC4), and absent in melanoma 2 (AIM2) inflammasomes, as well as the mRNA levels of NLRP3. Next, using a photothrombotic mouse model of recurrent stroke, we found that recurrent strokes increased the activation of NLRP3, exacerbated the brain damage and the pro-inflammatory response in wild type (WT) mice, but not in NLRP3 knockout (NLRP3 KO) mice. Additionally, we found that apoptosis-associated speck-like protein containing a CARD (ASC) protein level surrounding the infarct area was comparatively increased, but that ASC specks outside of microglia in both the ipsilateral and contralateral of stroke site were decreased in NLRP3 KO mice relative to wild-type (WT) controls, and the number of ASC specks surrounding the second infarct area was positively correlated to the damage scores. Mechanistically, we found that recombinant ASC (RecASC) activated NLRP3 and induced pro-inflammatory responses, exacerbating the outcome of ischemic stroke, in WT mice, but not in NLRP3 KO mice. We therefore conclude that the NLRP3 inflammasome is activated by two attacks of stroke, which act together with ASC to exacerbate recurrent strokes.

Effects of Voluntary Wheel-Running Types on Hippocampal Neurogenesis and Spatial Cognition in Middle-Aged Mice.

While increasing evidence demonstrated that voluntary wheel running promotes cognitive function, little is known on how different types of voluntary wheel running affect cognitive function in elderly populations. We investigated the effects of various voluntary wheel-running types on adult hippocampal neurogenesis and spatial cognition in middle-aged mice. Male C57BL6 and Thy1-green fluorescent protein (GFP) transgenic mice (13 months) were equally assigned to one of the following groups: (1) T1: no voluntary wheel running; (2) T2: intermittent voluntary wheel running; and (3) T3: continuous voluntary wheel running. The Thy1-GFP transgenic mice were used to specifically label granule cells, since Thy-1 is a promoter for neuronal expression. Behavioral evaluations suggested that intermittent voluntary wheel running improved Morris water maze performance in middle-aged mice. The number of BrdU-positive cells was significantly higher in both intermittent and continuous voluntary wheel running compared with no voluntary wheel running. However, only intermittent voluntary wheel running facilitated the newborn cells to differentiate into granule cells, while newborn cells tended to differentiate into astrocytes and repopulation of microglia was also enhanced in the continuous voluntary wheel-running group. These results indicated that intermittent voluntary exercise may be more beneficial for enhancing spatial memory. Effective improvement of hippocampal neurogenesis was also caused by intermittent voluntary wheel running in middle-aged mice.

Transplanted human neural precursor cells integrate into the host neural circuit and ameliorate neurological deficits in a mouse model of traumatic brain injury.

Traumatic brain injury (TBI) is to date one of the major critical conditions causing death and disability worldwide. Exogenous neural stem/precursor cells (NSCs/NPCs) hold great promise for improving neurological dysfunction, but their functional properties in vivo remain unknown. Human neural precursor cells (hNPCs) carrying one fluorescent reporter gene (DsRed) can be observed directly in vivo using two-photon laser-scanning microscope. Therefore, we evaluated the neural integration and potential therapeutic effect of hNPCs on mice with TBI. Behavioral tests were performed by rotarod task and Morris Water Maze task. Neural integration was detected by fluorometric Ca2+ imaging and nerve tracing. We found that motor and cognition functions were significantly improved in mice with hNPCs injection compared to mice with vehicle treatment, and hNPCs integrated into the host circuit and differentiated toward neuronal lineage. Our study provided reliable evidence for further hNPCs transplantation in clinical practice.

Evaluation of neuroactive effects of ethanol extract of Schisandra chinensis, Schisandrin, and Schisandrin B and determination of underlying mechanisms by zebrafish behavioral profiling.

Schisandra chinensis, a traditional Chinese medicine (TCM), has been used to treat sleep disorders. Zebrafish sleep/wake behavioral profiling provides a high-throughput platform to screen chemicals, but has never been used to study extracts and components from TCM. In the present study, the ethanol extract of Schisandra chinensis and its two main lignin components, schisandrin and schisandrin B, were studied in zebrafish. We found that the ethanol extract had bidirectional improvement in rest and activity in zebrafish. Schisandrin and schisandrin B were both sedative and active components. We predicted that schisandrin was related to serotonin pathway and the enthanol extract of Schisandra chinensis was related to seoronin and domapine pathways using a database of zebrafish behaviors. These predictions were confirmed in experiments using Caenorhabditis elegans. In conclusion, zebrafish behavior profiling could be used as a high-throughput platform to screen neuroactive effects and predict molecular pathways of extracts and components from TCM.

Continuous theta burst stimulation facilitates the clearance efficiency of the glymphatic pathway in a mouse model of sleep deprivation.

Sleep deprivation (SD) is a common condition associated with a variety of nervous system diseases, and has a negative impact on emotional and cognitive function. Continuous theta burst stimulation (cTBS) is known to improve cognition and emotion function in normal situations as well as in various types of dysfunction, but the mechanism remains unknown. We used two-photon in vivo imaging to explore the effect of cTBS on glymphatic pathway clearance in normal and SD C57BL/6J mice. Aquaporin-4 (AQP4) polarization was detected by immunofluorescence. Anxiety-like behaviors was measured using open field tests. We found that SD reduced influx efficiency along the peri-vascular space (PVS), disturbed AQP4 polarization and induced anxiety-like behaviors. CTBS significantly attenuated the decrease in efficiency of solute clearance usually incurred with SD, restored the loss of AQP4 polarization and improved anxiety-like behavior in SD animals. Our results implied that cTBS had the potential to protect against neuronal dysfunction induced by sleep disorders.

GABA-ergic interneurons involved in transcallosal inhibition of the visual cortices in vivo in mice.

In the current study we investigated the role of the corpus callosum, particularly the gamma-aminobutyric acid-ergic (GABAergic) projection neurons involved in interhemispheric inhibition (IHI). In order to explore IHI in primary visual cortices, we adopted a protocol whereby we performed a direct current lesion of the unilateral primary visual cortex with or without posterior callosotomy, and used two-photon Ca(2+)in vivo imaging on the opposite unaffected region to detect neural activities in mice. Following this procedure, the numbers of vesicular GABAergic transporters (VGATs) and GABAergic interneurons in the unaffected primary cortex were determined using immunofluorescence staining. Results indicated that following unilateral visual cortical lesioning without callosotomy, the neuronal Ca(2+) activities in the opposite side were significantly increased. However, the neuronal activities of the unaffected visual cortex in animals with unilateral cortical lesion with callosotomy were not significantly different. Additionally, there was no significant difference in the numbers of GABAergic interneurons in the unaffected region between each group, while the number of VGATs in the unaffected region was significantly decreased following unilateral visual cortical lesion without callosotomy, which was unchanged once with callosotomy. Finally, callosotomy alone without cortical lesioning produced no change in neuronal activities, the number of GABAergic interneurons or VGATs. Our results demonstrate that IHI between the homologous primary visual cortices occurs via the corpus callosum, and further indicate the important involvement of long-range GABAergic interneurons in transcallosal inhibition.

Allopurinol protects against ischemic insults in a mouse model of cortical microinfarction.

Microinfarcts are common in patients with cognitive decline and dementia. Allopurinol (ALLO), a xanthine oxidase (XO) enzyme inhibitor, has been found to reduce proinflammatory molecules and oxidative stress in the vasculature. We here examined the effect of pre-treatment with allopurinol on the cortical microinfarction. C57BL/6J mice were subjected to a permanent single penetrating arteriole occlusion induced by two-photon laser irradiation. Infarction volume, the activation of glial cells and nitrosative stress in the ischemic brain was assessed using immunohistochemistry. Pre-treatment with ALLO achieved 42% reduction of infarct volume and significantly reduced microglia infiltration, astrocyte proliferation and nitrosative stress in the ischemic brain. These data indicate that ALLO protects against microinfarcts possibly through inhibition of nitrosative stress and attenuation of microglia infiltration as well as astrocytes reactivation.

Identification of marine neuroactive molecules in behaviour-based screens in the larval zebrafish.

High-throughput behavior-based screen in zebrafish is a powerful approach for the discovery of novel neuroactive small molecules for treatment of nervous system diseases such as epilepsy. To identify neuroactive small molecules, we first screened 36 compounds (1-36) derived from marine natural products xyloketals and marine isoprenyl phenyl ether obtained from the mangrove fungus. Compound 1 demonstrated the most potent inhibition on the locomotor activity in larval zebrafish. Compounds 37-42 were further synthesized and their potential anti-epilepsy action was then examined in a PTZ-induced epilepsy model in zebrafish. Compound 1 and compounds 39, 40 and 41 could significantly attenuate PTZ-induced locomotor hyperactivity and elevation of c-fos mRNA in larval zebrafish. Compound 40 showed the most potent inhibitory action against PTZ-induced hyperactivity. The structure-activity analysis showed that the OH group at 12-position played a critical role and the substituents at the 13-position were well tolerated in the inhibitory activity of xyloketal derivatives. Thus, these derivatives may provide some novel drug candidates for the treatment of epilepsy.

Protective effects of traditional Chinese medicine formula NaoShuanTong capsule on haemorheology and cerebral energy metabolism disorders in rats with blood stasis.

NaoShuanTong capsule (NSTC), an oral traditional Chinese medicine formula, is composed of Pollen Typhae, Radix Paeoniae Rubra, Rhizoma Gastrodiae, Radix Rhapontici and Radix Curcumae. It has been widely used to treat ischemic stroke in clinic for many years in China. In addition to neuronal apoptosis, haemorheology and cerebral energy metabolism disorders also play an important role in the pathogenesis and development of ischemic stroke. The present study was designed to evaluate the in vivo protective effects of NSTC on haemorheology and cerebral energy metabolism disorders in rats with blood stasis. Sixty specific pathogen-free sprague-dawley rats, male only, were randomly divided into six groups (control group, model group, aspirin (100 mg/kg/d) group, NSTC low-dose (400 mg/kg/d) group, NSTC intermediate-dose (800 mg/kg/d) group, NSTC high-dose (1600 mg/kg/d) group) with 10 animals in each. The rats except those in the control group were placed in ice-cold water (0-4 °C) for 5 min during the time interval (4 h) of two adrenaline hydrochloride injections (0.8 mg/kg) to induce blood stasis. After treatment, whole blood viscosity at three shear rates, plasma viscosity and erythrocyte sedimentation rate significantly decreased in NSTC intermediate- and high-dose groups; erythrocyte aggregation index and red corpuscle electrophoresis index significantly decreased in all the three dose NSTC groups. Moreover, treatment with high-dose NSTC could significantly improve Na+-K+ adenosine triphosphatase (ATPase) and Ca2+ ATPase activity, as well as lower lactic acid level in brain tissues. These results demonstrated the protective effects of NSTC on haemorheology and cerebral energy metabolism disorders, which may provide scientific information for the further understanding of mechanism(s) of NSTC as a clinical treatment for ischemic stroke. Furthermore, the protective effects of activating blood circulation as observed in this study might create valuable insight for the utilisation of NSTC to be a feasible alternative therapeutic agent for patients with blood stasis.