Optogenetic Inhibition of Striatal GABAergic Neuronal Activity Improves Outcomes After Ischemic Brain Injury

Tropism-shifted AAV-PHP.eB-mediated bFGF gene therapy promotes varied neurorestoration after ischemic stroke in mice

JOURNAL/nrgr/04.03/01300535-202602000-00040/figure1/v/2025-05-05T160104Z/r/image-tiff AAV-PHP.eB is an artificial adeno-associated virus (AAV) that crosses the blood-brain barrier and targets neurons more efficiently than other AAVs when administered systematically. While AAV-PHP.eB has been used in various disease models, its cellular tropism in cerebrovascular diseases remains unclear. In the present study, we aimed to elucidate the tropism of AAV-PHP.eB for different cell types in the brain in a mouse model of ischemic stroke and evaluate its effectiveness in mediating basic fibroblast growth factor ( bFGF ) gene therapy. Mice were injected intravenously with AAV-PHP.eB either 14 days prior to (pre-stroke) or 1 day following (post-stroke) transient middle cerebral artery occlusion. Notably, we observed a shift in tropism from neurons to endothelial cells with post-stroke administration of AAV-PHP.eB-mNeonGreen (mNG). This endothelial cell tropism correlated strongly with expression of the endothelial membrane receptor lymphocyte antigen 6 family member A (Ly6A). Furthermore, AAV-PHP.eB-mediated overexpression of bFGF markedly improved neurobehavioral outcomes and promoted long-term neurogenesis and angiogenesis post-ischemic stroke. Our findings underscore the significance of considering potential tropism shifts when utilizing AAV-PHP.eB-mediated gene therapy in neurological diseases and suggest a promising new strategy for bFGF gene therapy in stroke treatment.

Chemogenetic modulation in stroke recovery: A promising stroke therapy Approach

Stroke remains a leading cause of long-term disability and mortality worldwide, necessitating novel therapeutic strategies to enhance recovery. Traditional rehabilitation approaches, including physical therapy and pharmacological interventions, often provide limited functional improvement. Neuromodulation has emerged as a promising strategy to promote post-stroke recovery by enhancing neuroplasticity and functional reorganization. Among various neuromodulatory techniques, chemogenetics, particularly Designer Receptors Exclusively Activated by Designer Drugs (DREADDs), offers precise, cell-type-specific, and temporally controlled modulation of neuronal and glial activity. This review explores the mechanisms and therapeutic potential of chemogenetic modulation in stroke recovery. Preclinical studies have demonstrated that activation of excitatory DREADDs (hM3Dq) in neurons located within the peri-infarct area or contralateral M1 has been shown to enhance neuroplasticity, facilitate axonal sprouting, and lead to improved behavioral recovery following stroke. Conversely, stimulation of inhibitory DREADDs (hM4Di) suppresses stroke-induced excitotoxicity, mitigates peri-infarct spreading depolarizations (PIDs), and modulates neuroinflammatory responses. By targeting specific neuronal and glial populations, chemogenetics enables phase-specific interventions-early inhibition to minimize damage during the acute phase and late excitation to promote plasticity during the recovery phase. Despite its advantages over traditional neuromodulation techniques, such as optogenetics and deep brain stimulation, several challenges remain before chemogenetics can be translated into clinical applications. These include optimizing viral vector delivery, improving ligand specificity, minimizing off-target effects, and ensuring long-term receptor stability. Furthermore, integrating chemogenetics with existing stroke rehabilitation strategies, including brain-computer interfaces and physical therapy, may enhance functional recovery by facilitating adaptive neuroplasticity. Future research should focus on refining chemogenetic tools to enable clinical application. By offering a highly selective, reversible, and minimally invasive approach, chemogenetics holds great potential for revolutionizing post-stroke therapy and advancing personalized neuromodulation strategies.

Improving Sensitivity and Longevity of In Vivo Glutamate Sensors with Electrodeposited NanoPt

In vivo glutamate sensing has provided valuable insight into the physiology and pathology of the brain. Electrochemical glutamate biosensors, constructed by cross-linking glutamate oxidase onto an electrode and oxidizing H2O2 as a proxy for glutamate, are the gold standard for in vivo glutamate measurements for many applications. While glutamate sensors have been employed ubiquitously for acute measurements, there are almost no reports of long-term, chronic glutamate sensing in vivo, despite demonstrations of glutamate sensors lasting for weeks in vitro. To address this, we utilized a platinum electrode with nanometer-scale roughness (nanoPt) to improve the glutamate sensors' sensitivity and longevity. NanoPt improved the GLU sensitivity by 67.4% and the sensors were stable in vitro for 3 weeks. In vivo, nanoPt glutamate sensors had a measurable signal above a control electrode on the same array for 7 days. We demonstrate the utility of the nanoPt sensors by studying the effect of traumatic brain injury on glutamate in the rat striatum with a flexible electrode array and report measurements of glutamate taken during the injury itself. We also show the flexibility of the nanoPt platform to be applied to other oxidase enzyme-based biosensors by measuring γ-aminobutyric acid in the porcine spinal cord. NanoPt is a simple, effective way to build high sensitivity, robust biosensors harnessing enzymes to detect neurotransmitters in vivo.

GABAergic system and chloride cotransporters as potential therapeutic targets to mitigate cell death in ischemia

Gamma aminobutyric acid (GABA) is a critical inhibitory neurotransmitter in the central nervous system that plays a vital role in modulating neuronal excitability. Dysregulation of GABAergic signaling, particularly involving the cotransporters NKCC1 and KCC2, has been implicated in various pathologies, including epilepsy, schizophrenia, autism spectrum disorder, Down syndrome, and ischemia. NKCC1 facilitates chloride influx, whereas KCC2 mediates chloride efflux via potassium gradient. Altered expression and function of these cotransporters have been associated with excitotoxicity, inflammation, and cellular death in ischemic events characterized by reduced cerebral blood flow, leading to compromised tissue metabolism and subsequent cell death. NKCC1 inhibition has emerged as a potential therapeutic approach to attenuate intracellular chloride accumulation and mitigate neuronal damage during ischemic events. Similarly, targeting KCC2, which regulates chloride efflux, holds promise for improving outcomes and reducing neuronal damage under ischemic conditions. This review emphasizes the critical roles of GABA, NKCC1, and KCC2 in ischemic pathologies and their potential as therapeutic targets. Inhibiting or modulating the activity of these cotransporters represents a promising strategy for reducing neuronal damage, preventing excitotoxicity, and improving neurological outcomes following ischemic events. Furthermore, exploring the interactions between natural compounds and NKCC1/KCC2 provides additional avenues for potential therapeutic interventions for ischemic injury.

Integration of 16S rRNA gene sequencing and LC/MS-based metabolomic analysis of early biomarkers of acute ischaemic stroke in Tibetan miniature pigs

Acute ischaemic stroke (AIS) is a complex, systemic, pathological, and physiological process. Systemic inflammatory responses and disorders of the gut microbiome contribute to increased mortality and disability following AIS. We conducted 16S high-throughput sequencing and ultra-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry-based non-targeted metabolomic analyses of the plasma from a Tibetan miniature pig middle cerebral artery occlusion (MCAO) model. A significant decrease in the abundance of Firmicutes and a significant increase in the abundance of Actinobacteria were observed after the onset of AIS. Among the plasma metabolites, the levels of phospholipids and amino acids were considerably altered. Loading values and differential metabolite-bacterial group association analyses of the metabolome and microbiome indicated a correlation between the microbiome and metabolome of Tibetan miniature pigs after MCAO. Furthermore, significant changes were observed in the ABC transporter pathway and purine metabolism in the gut microbiome-plasma metabolome during the early stage of AIS. Kyoto Encyclopaedia of Genes and Genomes enrichment analysis showed that arginine, proline, and cyanoamino acid metabolism was upregulated while ABC transporter metabolism pathway and carbohydrate digestion and absorption were substantially downregulated. The results of this study suggest that AIS affects the gut microbiota and plasma metabolites in Tibetan miniature pigs and that faecal microbiota transplantation could be a potential therapeutic approach for AIS.

Preventing development of post-stroke hyperexcitability by optogenetic or pharmacological stimulation of cortical excitatory activity

Stroke is the most common cause of acquired epilepsy, but treatment for preventing the development of post-stroke epilepsy is still unavailable. Since stroke results in neuronal damage and death as well as initial loss of activity in the affected brain region, homeostatic plasticity may be trigged and contribute to an increase in network hyperexcitability that underlies epileptogenesis. Correspondingly, enhancing brain activity may inhibit hyperexcitability from enhanced homeostatic plasticity and prevent post-stroke epileptogenesis. To test these hypotheses, we first used in vivo two-photon and mesoscopic imaging of activity of cortical pyramidal neurons in Thy1-GCaMP6 transgenic mice to determine longitudinal changes in excitatory activity after a photothrombotic ischemic stroke. At 3-days post-stroke, there was a significant loss of neuronal activity in the peri-injury area as indicated by reductions in the frequency of calcium spikes and percentage of active neurons, which recovered to baseline level at day 7, supporting a homeostatic activity regulation of the surviving neurons in the peri-injury area. We further used optogenetic stimulation to specifically stimulate activity of pyramidal neurons in the peri-injury area of Thy-1 channelrhodopsin transgenic mice from day 5 to day 15 after stroke. Using pentylenetetrazole test to evaluate seizure susceptibility, we showed that stroke mice are more susceptible to Racine stage V seizures (time latency 54.3 ± 12.9 min) compared to sham mice (107.1 ± 13.6 min), but optogenetic stimulation reversed the increase in seizure susceptibility (114.0 ± 9.2 min) in mice with stroke. Similarly, administration of D-cycloserine, a partial N-methyl-d-aspartate (NMDA) receptor agonist that can mildly enhance neuronal activity without causing post-stroke seizure, from day 5 to day 15 after a stroke significantly reversed the increase in seizure susceptibility. The treatment also resulted in an increased survival of glutamic acid decarboxylase 67 (GAD67) positive interneurons and a reduced activation of glial fibrillary acidic protein (GFAP) positive reactive astrocytes. Thus, this study supports the involvement of homeostatic activity regulation in the development of post-stroke hyperexcitability and potential application of activity enhancement as a novel strategy to prevent post-stroke late-onset seizure and epilepsy through regulating cortical homeostatic plasticity.

Upregulation of CCNB2 and Its Perspective Mechanisms in Cerebral Ischemic Stroke and All Subtypes of Lung Cancer: A Comprehensive Study

Cyclin B2 (CCNB2) belongs to type B cell cycle family protein, which is located on chromosome 15q22, and it binds to cyclin-dependent kinases (CDKs) to regulate their activities. In this study, 103 high-throughput datasets related to all subtypes of lung cancer (LC) and cerebral ischemic stroke (CIS) with the data of CCNB2 expression were collected. The analysis of standard mean deviation (SMD) and summary receiver operating characteristic (SROC) reflecting expression status demonstrated significant up-regulation of CCNB2 in LC and CIS (Lung adenocarcinoma: SMD = 1.40, 95%CI [0.98–1.83], SROC = 0.92, 95%CI [0.89–0.94]. Lung squamous cell carcinoma: SMD = 2.56, 95%CI [1.64–3.48]. SROC = 0.97, 95%CI [0.95–0.98]. Lung small cell carcinoma: SMD = 3.01, 95%CI [2.01–4.01]. SROC = 0.98, 95%CI [0.97–0.99]. CIS: SMD = 0.29, 95%CI [0.05–0.53], SROC = 0.68, 95%CI [0.63–0.71]). Simultaneously, protein-protein interaction (PPI) analysis indicated that CCNB2 is the hub molecule of crossed high-expressed genes in CIS and LC. Through Multiscale embedded gene co-expression network analysis (MEGENA), a gene module of CIS including 76 genes was obtained and function enrichment analysis of the CCNB2 module genes implied that CCNB2 may participate in the processes in the formation of CIS and tissue damage caused by CIS, such as “cell cycle,” “protein kinase activity,” and “glycosphingolipid biosynthesis.” Afterward, via single-cell RNA-seq analysis, CCNB2 was found up-regulated on GABAergic neurons in brain organoids as well as T cells expressing proliferative molecules in LUAD. Concurrently, the expression of CCNB2 distributed similarly to TOP2A as a module marker of cell proliferation in cell cluster. These findings can help in the field of the pathogenesis of LC-related CIS and neuron repair after CIS damage.

Optogenetic Methods to Investigate Brain Alterations in Preclinical Models

Investigating the neuronal dynamics supporting brain functions and understanding how the alterations in these mechanisms result in pathological conditions represents a fundamental challenge. Preclinical research on model organisms allows for a multiscale and multiparametric analysis in vivo of the neuronal mechanisms and holds the potential for better linking the symptoms of a neurological disorder to the underlying cellular and circuit alterations, eventually leading to the identification of therapeutic/rescue strategies. In recent years, brain research in model organisms has taken advantage, along with other techniques, of the development and continuous refinement of methods that use light and optical approaches to reconstruct the activity of brain circuits at the cellular and system levels, and to probe the impact of the different neuronal components in the observed dynamics. These tools, combining low-invasiveness of optical approaches with the power of genetic engineering, are currently revolutionizing the way, the scale and the perspective of investigating brain diseases. The aim of this review is to describe how brain functions can be investigated with optical approaches currently available and to illustrate how these techniques have been adopted to study pathological alterations of brain physiology.

Transcranial focused ultrasound stimulation reduces vasogenic edema after middle cerebral artery occlusion in mice

Blood-brain barrier (BBB) disruption underlies the vasogenic edema and neuronal cell death induced by acute ischemic stroke. Reducing this disruption has therapeutic potential. Transcranial focused ultrasound stimulation has shown neuromodulatory and neuroprotective effects in various brain diseases including ischemic stroke. Ultrasound stimulation can reduce inflammation and promote angiogenesis and neural circuit remodeling. However, its effect on the BBB in the acute phase of ischemic stroke is unknown. In this study of mice subjected to middle cerebral artery occlusion for 90 minutes, low-intensity low-frequency (0.5 MHz) transcranial focused ultrasound stimulation was applied 2, 4, and 8 hours after occlusion. Ultrasound stimulation reduced edema volume, improved neurobehavioral outcomes, improved BBB integrity (enhanced tight junction protein ZO-1 expression and reduced IgG leakage), and reduced secretion of the inflammatory factors tumor necrosis factor-α and activation of matrix metalloproteinase-9 in the ischemic brain. Our results show that low-intensity ultrasound stimulation attenuated BBB disruption and edema formation, which suggests it may have therapeutic use in ischemic brain disease as a protector of BBB integrity.

Stroke subtype-dependent synapse elimination by reactive gliosis in mice

The pathological role of reactive gliosis in CNS repair remains controversial. In this study, using murine ischemic and hemorrhagic stroke models, we demonstrated that microglia/macrophages and astrocytes are differentially involved in engulfing synapses in the reactive gliosis region. By specifically deleting MEGF10 and MERTK phagocytic receptors, we determined that inhibiting phagocytosis of microglia/macrophages or astrocytes in ischemic stroke improved neurobehavioral outcomes and attenuated brain damage. In hemorrhagic stroke, inhibiting phagocytosis of microglia/macrophages but not astrocytes improved neurobehavioral outcomes. Single-cell RNA sequencing revealed that phagocytosis related biological processes and pathways were downregulated in astrocytes of the hemorrhagic brain compared to the ischemic brain. Together, these findings suggest that reactive microgliosis and astrogliosis play individual roles in mediating synapse engulfment in pathologically distinct murine stroke models and preventing this process could rescue synapse loss.

Glia: A major player in glutamate-GABA dysregulation-mediated neurodegeneration

The imbalance between glutamate and γ-aminobutyric acid (GABA) results in the loss of synaptic strength leading to neurodegeneration. The dogma on the field considered neurons as the main players in this excitation-inhibition (E/I) balance. However, current strategies focusing only on neurons have failed to completely understand this condition, bringing up the importance of glia as an alternative modulator for neuroinflammation as glia alter the activity of neurons and is a source of both neurotrophic and neurotoxic factors. This review's primary goal is to illustrate the role of glia over E/I balance in the central nervous system and its interaction with neurons. Rather than focusing only on the neuronal targets, we take a deeper look at glial receptors and proteins that could also be explored as drug targets, as they are early responders to neurotoxic insults. This review summarizes the neuron-glia interaction concerning GABA and glutamate, possible targets, and its involvement in the E/I imbalance in neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis.

Cell-to-Cell Interactions Mediating Functional Recovery after Stroke

Ischemic damage in brain tissue triggers a cascade of molecular and structural plastic changes, thus influencing a wide range of cell-to-cell interactions. Understanding and manipulating this scenario of intercellular connections is the Holy Grail for post-stroke neurorehabilitation. Here, we discuss the main findings in the literature related to post-stroke alterations in cell-to-cell interactions, which may be either detrimental or supportive for functional recovery. We consider both neural and non-neural cells, starting from astrocytes and reactive astrogliosis and moving to the roles of the oligodendrocytes in the support of vulnerable neurons and sprouting inhibition. We discuss the controversial role of microglia in neural inflammation after injury and we conclude with the description of post-stroke alterations in pyramidal and GABAergic cells interactions. For all of these sections, we review not only the spontaneous evolution in cellular interactions after ischemic injury, but also the experimental strategies which have targeted these interactions and that are inspiring novel therapeutic strategies for clinical application.

Neuroprotective Effect of Alpha-asarone on the Rats Model of Cerebral Ischemia-Reperfusion Stroke via Ameliorating Glial Activation and Autophagy

Alpha-asarone, a major active component isolated from Acorus gramineus, can affect brain functions and behaviors by multiple mechanisms. However, the effect of alpha-asarone on cerebral ischemia-reperfusion (CIR) stroke has not been reported. The present study aimed to investigate the neuroprotective effect of alpha-asarone and the involved mechanisms against CIR stroke. Rats were subjected to middle cerebral occlusion (MCAO) for 2 h. Then the drug or drug-free vehicle was intravenously injected to corresponding groups. After reperfusion for 24 h, the infarct volume was evaluated by Triphenyl Tetrazolium Chloride (TTC) staining. The neurofunctional recovery and post-stroke epilepsy were evaluated. Nissl and Hematoxylin-Eosin (H&E) staining were used for histological observation. We investigated the protective mechanism of alpha-asarone against the stroke. The results showed that alpha-asarone exhibited a desirable neuroprotective effect, manifested as reducing infarct volume and post-stroke epilepsy and improving neurological function. Histological and flow cytometry analysis revealed that alpha-asarone treatment alleviated cell injury and apoptosis in vivo and in vitro. Furthermore, alpha-asarone decreased GFAP, Iba-1, and LC3II/LC3I expression and increased the expression of p62. These results suggested that alpha-asarone attenuated the CIR stroke injury via ameliorating glial activation and autophagy.

BK Channel-Mediated Microglial Phagocytosis Alleviates Neurological Deficit After Ischemic Stroke

Microglial phagocytosis benefits neurological recovery after stroke. Large-conductance Ca2⁺-activated K⁺ currents are expressed in activated microglia, and BK channel knockout aggravates cerebral ischemic injury. However, the effect of BK channels on microglial phagocytosis after ischemic stroke remains unknown. Here, we explored whether BK channel activation is beneficial for neurological outcomes through microglial phagocytosis after ischemic stroke. ICR mice after transient middle cerebral artery occlusion (tMCAO) were treated with dimethyl sulfoxide (DMSO), BK channel activator NS19504, and inhibitor Paxilline. The results showed a decrease in BK channel expression after tMCAO. BK channel activator NS19504 alleviates neurological deficit after experimental modeling of tMCAO in mice compared to the control. Furthermore, we treated primary microglia with DMSO, NS19504, and Paxilline after oxygen glucose deprivation (OGD). NS19504 promoted primary microglial phagocytosing fluorescent beads and neuronal debris, which reduced neuronal apoptosis after stroke. These effects could be reversed by BK channel inhibitor Paxilline. Finally, NS19504 increased relative phosphorylated extracellular signal-regulated kinase 1/2 expression compared to the Paxilline group at the third day after stroke. Our findings indicate that microglial BK channels are a potential target for acute stage of ischemic stroke therapy.

Transcranial Focused Ultrasound Stimulation Improves Neurorehabilitation after Middle Cerebral Artery Occlusion in Mice

Transcranial focused ultrasound stimulation (tFUS) regulates neural activity in different brain regions in humans and animals. However, the role of ultrasound stimulation in modulating neural activity and promoting neurorehabilitation in the ischemic brain is largely unknown. In the present study, we explored the effect of tFUS on neurological rehabilitation and the underlying mechanism. Adult male ICR mice (n=42) underwent transient middle cerebral artery occlusion. One week after brain ischemia, low frequency (0.5 MHz) tFUS was applied to stimulate the ischemic hemisphere of mice for 7 consecutive days (10 minutes daily). Brain infarct volume, neurobehavioral tests, microglia activation, IL-10 and IL-10R levels were further assessed for up to 14 days. We found that the brain infarct volume was significantly reduced in the tFUS treated mice compared to that in the non-treated mice (p<0.05). Similarly, neurological severity scores, elevated body swing test, and corner test improved in the tFUS treated mice (p<0.05). We also demonstrated that tFUS resulted in increased M2 microglia in the ischemic brain region. The expression of IL-10R and IL-10 levels were also substantially upregulated (p<0.05). We concluded that tFUS served as a unique technique to promote neurorehabilitation after brain ischemia by promoting microglia polarization and further regulating IL-10 signaling in the ischemic brain.

Urolithin A Prevents Focal Cerebral Ischemic Injury via Attenuating Apoptosis and Neuroinflammation in Mice

Neuroinflammation contributes to neuronal death in cerebral ischemia. Urolithin A (UA), a gut microbial metabolite of ellagic acid, has emerged as a potential anti-inflammatory agent. However, its roles and precise mechanisms in stroke remain unknown. Here we found that UA treatment ameliorated infarction, neurological deficit scores, and spatial memory deficits after cerebral ischemia. Furthermore, UA significantly reduced neuron loss and promoted neurogenesis after ischemic stroke. We also found that UA attenuated apoptosis by regulating apoptotic-related proteins. Meanwhile, UA treatment inhibited glial activation via affecting inflammatory signaling pathways, specifically by enhancing cerebral AMPK and IκBa activation while decreasing the activation of Akt, P65NFκB, ERK, JNK, and P38MAPK. Our findings reveal a key role of UA against ischemic stroke through modulating apoptosis and neuroinflammation in mice.

Fingolimod Inhibits Inflammation but Exacerbates Brain Edema in the Acute Phases of Cerebral Ischemia in Diabetic Mice

Background and Purpose: Diabetes mellitus increases stroke incidence and mortality and hampers functional recovery after stroke. Fingolimod has been shown to improve neurofunctional recovery and reduce brain infarction after ischemic injury in mice without comorbidities. In this work, we investigated the effects of fingolimod in diabetic mice after transient middle cerebral artery occlusion (tMCAO).

Methods: Hyperglycemia was induced by a single bolus streptozotocin injection. Adult male ICR mice (n = 86) underwent 1-h tMCAO surgery and received intraperitoneal injection of fingolimod (1 mg/kg) or vehicle immediately after reperfusion. Clark neurological score, brain infarction and edema, blood–brain barrier (BBB) integrity, apoptosis, and inflammation were evaluated at 24 h after tMCAO.

Results: Fingolimod treatment reduced the number of infiltrated inflammatory cells and lowered the mRNA level of Tnfα. It also increased the ratio of Bcl-2/Bax. However, fingolimod significantly aggravated brain edema and reduced the expression levels of tight junction proteins ZO-1 and Occludin. The negative impacts of fingolimod on BBB integrity outweighed its beneficial effects in anti-inflammation, which resulted in the lack of improvement in endpoint outcomes at 24 h after tMCAO.

Conclusion: Caution should be taken in considering the acute treatment using fingolimod for ischemic stroke with diabetes comorbidity.

Optogenetic translocation of protons out of penumbral neurons is protective in a rodent model of focal cerebral ischemia

BACKGROUND

Intracellular acidosis in the ischemic penumbra can contribute to further cell death, effectively enlarging the infarct core. Restoring the acid-base balance may enhance tissue survivability after cerebral ischemia.

OBJECTIVE

This study investigated whether translocating protons out of penumbral neurons could mitigate tissue acidification and induce neuroprotection in a rodent model of acute cerebral ischemia.

METHODS

We modulated the penumbral neurons via a light-driven pump to translocate protons out (i.e., archaerhodopsin/ArchT group) or into (i.e., channelrhodopsin-2/ChR2 group) neurons after focal cerebral ischemia in rats. Intracellular pH values were imaged via neutral red (NR) fluorescence and cerebral blood flow (CBF) was monitored through laser speckle contrast imaging (LSCI). Global CBF responses to electrical stimulation of the hindlimbs were obtained 24 h and 48 h after ischemia to assess neurological function. Behavioral and histological outcomes were evaluated 48 h after ischemia. A control group without gene modification was included.

RESULTS

The reduction of relative pH (R_pH), the amplitude of negative peak of hypoemic response (R_NP) and the hemispheric lateralization index (LI) in ArchT group were significantly less than those of the ChR2 or control group. Moreover, R_pH was strongly correlated with R_NP (r = 0.60) and LI (r_24h = 0.80, r_48h = 0.59). In addition, behavioral and histological results supported a neuroprotective effect of countering neuronal acidosis in penumbra through optogenetic stimulation.

CONCLUSION(S)

These results indicate that countering intracellular acidosis by optogenetically translocating protons out of penumbral neurons during the acute ischemic stage could induce protection after ischemic brain injury.

New era of optogenetics: from the central to peripheral nervous system

Optogenetics has recently gained recognition as a biological technique to control the activity of cells using light stimulation. Many studies have applied optogenetics to cell lines in the central nervous system because it has the potential to elucidate neural circuits, treat neurological diseases and promote nerve regeneration. There have been fewer studies on the application of optogenetics in the peripheral nervous system. This review introduces the basic principles and approaches of optogenetics and summarizes the physiology and mechanism of opsins and how the technology enables bidirectional control of unique cell lines with superior spatial and temporal accuracy. Further, this review explores and discusses the therapeutic potential for the development of optogenetics and its capacity to revolutionize treatment for refractory epilepsy, depression, pain, and other nervous system disorders, with a focus on neural regeneration, especially in the peripheral nervous system. Additionally, this review synthesizes the latest preclinical research on optogenetic stimulation, including studies on non-human primates, summarizes the challenges, and highlights future perspectives. The potential of optogenetic stimulation to optimize therapy for peripheral nerve injuries (PNIs) is also highlighted. Optogenetic technology has already generated exciting, preliminary evidence, supporting its role in applications to several neurological diseases, including PNIs.

Chemogenetics-mediated acute inhibition of excitatory neuronal activity improves stroke outcome

BACKGROUND AND PURPOSE

Ischemic stroke significantly perturbs neuronal homeostasis leading to a cascade of pathologic events causing brain damage. In this study, we assessed acute stroke outcome after chemogenetic inhibition of forebrain excitatory neuronal activity.

METHODS

We generated hM4Di-TG transgenic mice expressing the inhibitory hM4Di, a Designer Receptors Exclusively Activated by Designer Drugs (DREADD)-based chemogenetic receptor, in forebrain excitatory neurons. Clozapine-N-oxide (CNO) was used to activate hM4Di DREADD. Ischemic stroke was induced by transient occlusion of the middle cerebral artery. Neurologic function and infarct volumes were evaluated. Excitatory neuronal suppression in the hM4Di-TG mouse forebrain was assessed electrophysiologically in vitro and in vivo, based on evoked synaptic responses, and in vivo based on occurrence of potassium-induced cortical spreading depolarizations.

RESULTS

Detailed characterization of hM4Di-TG mice confirmed that evoked synaptic responses in both in vitro hippocampal slices and in vivo motor cortex were significantly reduced after CNO-mediated activation of the inhibitory hM4Di DREADD. Further, CNO treatment had no obvious effects on physiology and motor function in either control or hM4Di-TG mice. Importantly, hM4Di-TG mice treated with CNO at either 10 min before ischemia or 30 min after reperfusion exhibited significantly improved neurologic function and smaller infarct volumes compared to CNO-treated control mice. Mechanistically, we showed that potassium-induced cortical spreading depression episodes were inhibited, including frequency and duration of DC shift, in CNO-treated hM4Di-TG mice.

CONCLUSIONS

Our data demonstrate that acute inhibition of a subset of excitatory neurons after ischemic stroke can prevent brain injury and improve functional outcome. This study, together with the previous work in optogenetic neuronal modulation during the chronic phase of stroke, supports the notion that targeting neuronal activity is a promising strategy in stroke therapy.

Early reduced behavioral activity induced by large strokes affects the efficiency of enriched environment in rats

The majority of stroke patients develop post-stroke fatigue, a symptom which impairs motivation and diminishes the success of rehabilitative interventions. We show that large cortical strokes acutely reduce activity levels in rats for 1-2 weeks as a physiological response paralleled by signs of systemic inflammation. Rats were exposed early (1-2 weeks) or late (3-4 weeks after stroke) to an individually monitored enriched environment to stimulate self-controlled high-intensity sensorimotor training. A group of animals received Anti-Nogo antibodies for the first two weeks after stroke, a neuronal growth promoting immunotherapy already in clinical trials. Early exposure to the enriched environment resulted in poor outcome: Training intensity was correlated to enhanced systemic inflammation and functional impairment. In contrast, animals starting intense sensorimotor training two weeks after stroke preceded by the immunotherapy revealed better recovery with functional outcome positively correlated to the training intensity and the extent of re-innervation of the stroke denervated cervical hemi-cord. Our results suggest stroke-induced fatigue as a biological purposeful reaction of the organism during neuronal remodeling, enabling new circuit formation which will then be stabilized or pruned in the subsequent rehabilitative training phase. However, intense training too early may lead to wrong connections and is thus less effective.

Optogenetics in Brain Research: From a Strategy to Investigate Physiological Function to a Therapeutic Tool

Dissecting the functional roles of neuronal circuits and their interaction is a crucial step in basic neuroscience and in all the biomedical field. Optogenetics is well-suited to this purpose since it allows us to study the functionality of neuronal networks on multiple scales in living organisms. This tool was recently used in a plethora of studies to investigate physiological neuronal circuit function in addition to dysfunctional or pathological conditions. Moreover, optogenetics is emerging as a crucial technique to develop new rehabilitative and therapeutic strategies for many neurodegenerative diseases in pre-clinical models. In this review, we discuss recent applications of optogenetics, starting from fundamental research to pre-clinical applications. Firstly, we described the fundamental components of optogenetics, from light-activated proteins to light delivery systems. Secondly, we showed its applications to study neuronal circuits in physiological or pathological conditions at the cortical and subcortical level, in vivo. Furthermore, the interesting findings achieved using optogenetics as a therapeutic and rehabilitative tool highlighted the potential of this technique for understanding and treating neurological diseases in pre-clinical models. Finally, we showed encouraging results recently obtained by applying optogenetics in human neuronal cells in-vitro.

Optogenetic manipulation of astrocytes from synapses to neuronal networks: A potential therapeutic strategy for neurodegenerative diseases

Astrocytes are the most widespread and heterogeneous glial cells in the central nervous system and key regulators for brain development. They are capable of receiving neurotransmitters produced by synaptic activities and regulating synaptic functions by releasing gliotransmitters as part of the tripartite synapse. In addition to communicating with neurons at synaptic levels, astrocytes can integrate into inhibitory neural networks to interact with neurons in neuronal circuits. Astrocytes are closely related to the pathogenesis and pathological processes of neurodegenerative diseases (NDs). Recently, optogenetics has now been applied to reveal the function of astrocytes in physiology and pathology. Herein, we discuss the possibility whether optogenetics could be used to control the release of gliotransmitters and regulate astrocytic membrane channels. Thus, the capability of modulating the bidirectional interactions between astrocytes and neurons in both synaptic and neuronal networks via optogenetics is evaluated. Furthermore, we discuss that manipulating astrocytes via optogenetics might be an effective way to investigate the potential therapeutic strategy for NDs.

GABAergic imbalance is normalized by dopamine D1 receptor activation in the striatum contralateral to the cortical injury in motor deficit-recovered rats

RATIONALE

The sensorimotor cortex and the striatum are interconnected by the corticostriatal pathway, suggesting that cortical injury alters the striatal function, which may be modulated by dopamine.

OBJECTIVES

We studied whether the activation of dopamine D₁ receptors (D₁Rs) modulates the γ-aminobutyric acid (GABA) and glutamate levels in the striatum of recovered rats at 192 h after cortical injury.

METHODS

The D₁R agonist SKF-38393 (0, 2, 3, or 4 mg/kg) was administered at 24, 48, 96, and 192 h post-injury, and then rats were decapitated to determine GABA and glutamate levels and the levels of D₁R mRNA on both sides of the striatum.

RESULTS

GABAergic imbalance in the striatum contralateral to the injury site was normalized by the administration of the D₁R agonist, but this treatment did not produce a significant effect on glutamate levels, suggesting that glutamate was metabolized into GABA. The administration of SKF-38393 (2 mg/kg) decreased the levels of D₁R mRNA in the striatum contralateral to the injury, and this effect was blocked by the coadministration of the D₁R antagonist SCH-23390 (2 mg/kg). In the striatum ipsilateral to the injury, the D₁R agonist increased the D₁R mRNA levels, an effect that was blocked by SCH-23390.

CONCLUSION

The reversal of the GABAergic imbalance in the striatum contralateral to the cortical injury can be modulated by extrastriatal D₁R activation, and the D₁R agonist-induced increases in the D₁R mRNA levels in the striatum ipsilateral to the injury suggest that the striatum may be necessary to achieve functional recovery.

The effect of lithium chloride on the attenuation of cognitive impairment in experimental hypoglycemic rats

BACKGROUND

Hypoglycemia is the most common complication in the treatment of diabetes mellitus. Accumulating evidence indicated that severe hypoglycemia could induce cognitive impairment. However, the molecular mechanism of regulating this progress is largely unknown.

METHODS

We established a model of insulin-induced recurrent hypoglycemia in adult male Wistar rats (n = 40). Lithium chloride was injected after hypoglycemia once a day for consecutive 30 days. The loss of cognition function was evaluated by water maze test in these hypoglycemic rats. Glial cells activation and Wnt and inflammatory cytokines IL-1β, IL-6, IL-4, IL-10, TGFβ and TNFα expression were further examined to determine the mechanism of cognitive function impairment.

RESULTS

Hypoglycemia could induce impairment of cognitive function in rats and administration of lithium chloride could partly attenuate cognitive impairment compared to the control (p < 0.05). Lithium chloride could significantly up-regulate Wnt signaling and reduce hypoglycemia-induced neuronal death, glial cells activation and inflammatory response in the hippocampus of rats compared to the control (p < 0.05). The efficacy of lithium chloride could be reversed by injecting canonical Wnt signaling antagonist the dickkopf homolog 1.

CONCLUSION

Lithium chloride attenuated hypoglycemia-induced cognitive function impairment in rats; and it was associated with Wnt signaling up-regulation and reduction of inflammatory response. Our results suggested that activating Wnt signaling pathways and inhibiting inflammatory response were the therapeutic potential to prevent hypoglycemia-induced neurological damage.

L-glutamine protects mouse brain from ischemic injury via up-regulating heat shock protein 70

INTRODUCTION

L-glutamine is an antioxidant that plays a role in a variety of biochemical processes. Given that oxidative stress is a key component of stroke pathology, the potential of L-glutamine in the treatment of ischemic stroke is worth exploring.

AIMS

In this study, we investigated the effect and mechanisms of action of L-glutamine after cerebral ischemic injury.

RESULTS

L-glutamine reduced brain infarct volume and promoted neurobehavioral recovery in mice. L-glutamine administration increased the expression of heat-shock protein 70 (HSP70) in astrocytes and endothelial cells. Such effects were abolished by the coadministration of Apoptozole, an inhibitor of the ATPase activity of HSP70. L-glutamine also reduced oxidative stress and neuronal apoptosis, and increased the level of superoxide dismutase, glutathione, and brain-derived neurotrophic factor. Cotreatment with Apoptozole abolished these effects. Cell culture study further revealed that the conditioned medium from astrocytes cultured with L-glutamine reduced the apoptosis of neurons after oxygen-glucose deprivation.

CONCLUSION

L-glutamine attenuated ischemic brain injury and promoted functional recovery via HSP70, suggesting its potential in ischemic stroke therapy.

State-of-the-Art Techniques to Causally Link Neural Plasticity to Functional Recovery in Experimental Stroke Research

Current experimental stroke research faces the same challenge as neuroscience: to transform correlative findings in causative ones. Research of recent years has shown the tremendous potential of the central nervous system to react to noxious stimuli such as a stroke: Increased plastic changes leading to reorganization in form of neuronal rewiring, neurogenesis, and synaptogenesis, accompanied by transcriptional and translational turnover in the affected cells, have been described both clinically and in experimental stroke research. However, only minor attempts have been made to connect distinct plastic remodeling processes as causative features for specific behavioral phenotypes. Here, we review current state-of the art techniques for the examination of cortical reorganization and for the manipulation of neuronal circuits as well as techniques which combine anatomical changes with molecular profiling. We provide the principles of the techniques together with studies in experimental stroke research which have already applied the described methodology. The tools discussed are useful to close the loop from our understanding of stroke pathology to the behavioral outcome and may allow discovering new targets for therapeutic approaches. The here presented methods open up new possibilities to assess the efficiency of rehabilitative strategies by understanding their external influence for intrinsic repair mechanisms on a neurobiological basis.