Transcranial pulse current stimulation improves the locomotor function in a rat model of stroke

Interference with glutamate antiporter system xc - enables post-hypoxic long-term potentiation in hippocampus

Our group previously showed that genetic or pharmacological inhibition of the cystine/glutamate antiporter, system xc -, mitigates excitotoxicity after anoxia by increasing latency to anoxic depolarization, thus attenuating the ischaemic core. Hypoxia, however, which prevails in the ischaemic penumbra, is a condition where neurotransmission is altered, but excitotoxicity is not triggered. The present study employed mild hypoxia to further probe ischaemia-induced changes in neuronal responsiveness from wild-type and xCT KO (xCT-/-) mice. Synaptic transmission was monitored in hippocampal slices from both genotypes before, during and after a hypoxic episode. Although wild-type and xCT-/- slices showed equal suppression of synaptic transmission during hypoxia, mutant slices exhibited a persistent potentiation upon re-oxygenation, an effect we termed 'post-hypoxic long-term potentiation (LTP)'. Blocking synaptic suppression during hypoxia by antagonizing adenosine A1 receptors did not preclude post-hypoxic LTP. Further examination of the induction and expression mechanisms of this plasticity revealed that post-hypoxic LTP was driven by NMDA receptor activation, as well as increased calcium influx, with no change in paired-pulse facilitation. Hence, the observed phenomenon engaged similar mechanisms as classical LTP. This was a remarkable finding as theta-burst stimulation-induced LTP was equivalent between genotypes. Importantly, post-hypoxic LTP was generated in wild-type slices pretreated with system xc - inhibitor, S-4-carboxyphenylglycine, thereby confirming the antiporter's role in this phenomenon. Collectively, these data indicate that system xc - interference enables neuroplasticity in response to mild hypoxia, and, together with its regulation of cellular damage in the ischaemic core, suggest a role for the antiporter in post-ischaemic recovery of the penumbra.

Blocking cerebral lymphatic system reduces central and peripheral inflammatory response in ischemic stroke

Reduced blood supply to the brain activates the intracranial inflammatory response, a key contributor to secondary brain damage in ischemic stroke. Post-stroke, activation of peripheral immune cells leads to systemic inflammatory responses. Usingin vivo approaches, we investigated meningeal lymphatics' role in central immune cell infiltration and peripheral immune cell activation. The bilateral deep cervical lymph nodes (dCLNs) were removed 7 days before right middle cerebral artery occlusion in Sprague Dawley (SD) rats. At 3, 24, and 72 h post-intervention, brain immune cell infiltration and microglial and astrocyte activation were measured, while immune cells were classified in the spleen and blood. Inflammatory factor levels in peripheral blood were analyzed. Simultaneously, reverse verification was conducted by injecting AAV-vascular endothelial growth factor C (AAV-VEGFC) adenovirus into the lateral ventricle 14 days before middle cerebral artery occlusion (MCAO) induction to enhance meningeal lymph function. Blocking meningeal LVs in MCAO rats significantly reduced infarct area and infiltration, and inhibited microglia and pro-inflammatory astrocytes activation. After removing dCLNs, CD4+ T lymphocytes, CD8+ T lymphocytes, B lymphocytes, macrophages, and neutrophils in the spleen and blood of MCAO rats decreased significantly at different time points. The levels of inflammatory factors IL-6, IL-10, IL-1β, and TNF-α in plasma decreased significantly. Tests confirmed the results, and AAV-VEGFC-induced MCAO rats provided reverse validation.

Progranulin Facilitates Corneal Repair Through Dual Mechanisms of Inflammation Suppression and Regeneration Promotion

The cornea serves as a vital protective barrier for the eye; however, it is prone to injury and damage that can disrupt corneal epithelium and nerves, triggering inflammation. Therefore, understanding the biological effects and molecular mechanisms involved in corneal wound healing and identifying drugs targeting these pathways is crucial for researchers in this field. This study aimed to investigate the therapeutic potential of progranulin (PGRN) in treating corneal injuries. Our findings demonstrated that PGRN significantly enhanced corneal wound repair by accelerating corneal re-epithelialization and re-innervation. In vitro experiments with cultured epithelial cells and trigeminal ganglion cells further revealed that PGRN stimulated corneal epithelial cell proliferation and promoted axon growth in trigeminal ganglion cells. Through RNA-sequencing (RNA-seq) analysis and other experimental techniques, we discovered that PGRN exerted its healing effects modulating Wnt signaling pathway, which played a critical role in repairing epithelial cells and promoting axon regeneration in trigeminal neurons. Importantly, our study highlighted the anti-inflammatory properties of PGRN by inhibiting the NF-κB signaling pathway, leading to decreased infiltration of macrophages. In conclusion, our findings underscored the potential of PGRN in facilitating corneal wound healing by promoting corneal epithelial cell proliferation, trigeminal ganglion cell axon regeneration, and suppressing ocular inflammation. These results suggest that PGRN could potentially expedite the healing process and improve visual outcomes in patients with corneal injuries.

[Therapies for the Improvement of Stroke Recovery - Assessment of Clinical Trial Results]

Recovery processes after stroke include restoration or compensation of function initially lost or newly acquired after injury. Therapeutic interventions can either directly improve these processes and/or inhibit processes that impede regeneration. Numerous experimental studies suggested a great opportunity for such treatments, but the results from recent large clinical trials with neuromodulators such as dopamine and fluoxetine have been rather disappointing. The reasons for this are manifold and involve the extrapolation of results from animal models to humans. Given the differences between animals and humans in genetic and epigenetic background, brain size and anatomy, cerebral vascular anatomy, immune system, as well as clinical function, and behavior, direct extrapolation is unlikely to work. Backward blockades include the incompatible adaption of clinical trial objectives and outcomes in clinical trials with regard to previous preclinical findings. For example, the clinical recovery trial design widely varies and has been characterized by the selection of different clinical endpoints, the inclusion a wide spectrum of stroke subtypes and clinical syndromes, and different time windows for treatment initiation after onset of infarction. This review will discuss these aspects based on the results of the recent stroke recovery trials with the aim to contributing to the development of a therapy that improves the functional outcome of a chronic stroke patient.

TRPM4 Blocking Antibody Protects Cerebral Vasculature in Delayed Stroke Reperfusion

Reperfusion therapy for acute ischemic stroke aims to restore the blood flow of occluded blood vessels. However, successful recanalization is often associated with disruption of the blood-brain barrier, leading to reperfusion injury. Delayed recanalization increases the risk of severe reperfusion injury, including severe cerebral edema and hemorrhagic transformation. The TRPM4-blocking antibody M4P has been shown to alleviate reperfusion injury and improve functional outcomes in animal models of early stroke reperfusion. In this study, we examined the role of M4P in a clinically relevant rat model of delayed stroke reperfusion in which the left middle cerebral artery was occluded for 7 h. To mimic the clinical scenario, M4P or control IgG was administered 1 h before recanalization. Immunostaining showed that M4P treatment improved vascular morphology after stroke. Evans blue extravasation demonstrated attenuated vascular leakage following M4P treatment. With better vascular integrity, cerebral perfusion was improved, leading to a reduction of infarct volume and animal mortality rate. Functional outcome was evaluated by the Rotarod test. As more animals with severe injuries died during the test in the control IgG group, we observed no difference in functional outcomes in the surviving animals. In conclusion, we identified the potential of TRPM4 blocking antibody M4P to ameliorate vascular injury during delayed stroke reperfusion. If combined with reperfusion therapy, M4P has the potential to improve current stroke management.

Magnetothermal-based non-invasive focused magnetic stimulation for functional recovery in chronic stroke treatment

Magnetic heat-based brain stimulation of specific lesions could promote the restoration of impaired motor function caused by chronic stroke. We delivered localized stimulation by nanoparticle-mediated heat generation within the targeted brain area via focused magnetic stimulation. The middle cerebral artery occlusion model was prepared, and functional recovery in the chronic-phase stroke rat model was demonstrated by the therapeutic application of focused magnetic stimulation. We observed a transient increase in blood-brain barrier permeability at the target site of < 4 mm and metabolic brain activation at the target lesion. After focused magnetic stimulation, the rotarod score increased by 390 ± 28% (p < 0.05) compared to the control group. Standardized uptake value in the focused magnetic stimulation group increased by 2063 ± 748% (p < 0.01) compared to the control group. Moreover, an increase by 24 ± 5% (p < 0.05) was observed in the sham group as well. Our results show that non-invasive focused magnetic stimulation can safely modulate BBB permeability and enhance neural activation for chronic-phase stroke treatment in the targeted deep brain area.

Leonurine Reduces Oxidative Stress and Provides Neuroprotection against Ischemic Injury via Modulating Oxidative and NO/NOS Pathway

Leonurine (Leo) has been found to have neuroprotective effects against cerebral ischemic injury. However, the exact molecular mechanism underlying its neuroprotective ability remains unclear. The aim of the present study was to investigate whether Leo could provide protection through the nitric oxide (NO)/nitric oxide synthase (NOS) pathway. We firstly explored the effects of NO/NOS signaling on oxidative stress and apoptosis in in vivo and in vitro models of cerebral ischemia. Further, we evaluated the protective effects of Leo against oxygen and glucose deprivation (OGD)-induced oxidative stress and apoptosis in PC12 cells. We found that the rats showed anxiety-like behavior, and the morphology and number of neurons were changed in a model of photochemically induced cerebral ischemia. Both in vivo and in vitro results show that the activity of superoxide dismutase (SOD) and glutathione (GSH) contents were decreased after ischemia, and reactive oxygen species (ROS) and malondialdehyde (MDA) levels were increased, indicating that cerebral ischemia induced oxidative stress and neuronal damage. Moreover, the contents of NO, total NOS, constitutive NOS (cNOS) and inducible NOS (iNOS) were increased after ischemia in rat and PC12 cells. Treatment with L-nitroarginine methyl ester (L-NAME), a nonselective NOS inhibitor, could reverse the change in NO/NOS expression and abolish these detrimental effects of ischemia. Leo treatment decreased ROS and MDA levels and increased the activity of SOD and GSH contents in PC12 cells exposed to OGD. Furthermore, Leo reduced NO/NOS production and cell apoptosis, decreased Bax expression and increased Bcl-2 levels in OGD-treated PC12 cells. All the data suggest that Leo protected against oxidative stress and neuronal apoptosis in cerebral ischemia by inhibiting the NO/NOS system. Our findings indicate that Leo could be a potential agent for the intervention of ischemic stroke and highlighted the NO/NOS-mediated oxidative stress signaling.

Efficacy and safety of transcutaneous auricular vagus nerve stimulation combined with conventional rehabilitation training in acute stroke patients: a randomized controlled trial conducted for 1 year involving 60 patients

Transcutaneous auricular vagus nerve stimulation (ta-VNS) is a novel noninvasive treat-ment for stroke that directly stimulates the peripheral auricular branch of the vagus nerve. There have been recent reports that ta-VNS combined with conventional rehabilitation training promotes the recovery of neurological function of patients with acute stroke. However, these were small-sample-sized studies on the recovery of neurological function in patients after percutaneous vagus nerve stimulation in the subacute and chronic phases after stroke. This double-blinded randomized controlled trial involved 60 acute ischemic or hemorrhagic stroke patients aged 18-80 years who received treatment in the Second Affiliated Hospital of Chongqing Medical University. The subjects were randomly assigned to receive ta-VNS or sham ta-VNS combined with conventional rehabilitation training. The follow-up results over 1 year revealed that ta-VNS combined with conventional rehabilitation training greatly improved the recovery of motor and sensory functions and emotional responses compared with sham ta-VNS combined with conventional rehabilitation training. There were no obvious side effects. These findings suggest that ta-VNS combined with conventional rehabilitation training for the treatment of acute ischemic or hemorrhagic stroke patients is safe and effective.

Electroacupuncture treatment improves motor function and neurological outcomes after cerebral ischemia/reperfusion injury

Electroacupuncture (EA) has been widely used for functional restoration after stroke. However, its role in post-stroke rehabilitation and the associated regulatory mechanisms remain poorly understood. In this study, we applied EA to the Zusanli (ST36) and Quchi (LI11) acupoints in rats with middle cerebral artery occlusion and reperfusion. We found that EA effectively increased the expression of brain-derived neurotrophic factor and its receptor tyrosine kinase B, synapsin-1, postsynaptic dense protein 95, and microtubule-associated protein 2 in the ischemic penumbra of rats with middle cerebral artery occlusion and reperfusion. Moreover, EA greatly reduced the expression of myelin-related inhibitors Nogo-A and NgR in the ischemic penumbra. Tyrosine kinase B inhibitor ANA-12 weakened the therapeutic effects of EA. These findings suggest that EA can improve neurological function after middle cerebral artery occlusion and reperfusion, possibly through regulating the activity of the brain-derived neurotrophic factor/tyrosine kinase B signal pathway. All procedures and experiments were approved by the Animal Research Committee of Shanghai University of Traditional Chinese Medicine, China (approval No. PZSHUTCM200110002) on January 10, 2020.

Stroke recovery enhancing therapies: lessons from recent clinical trials

Poststroke recovery processes include restoration or compensation of function, respectively functions initially lost or new functions acquired after an injury. Therapeutic interventions can enhance these processes and/or reduce processes impeding regeneration. Numerous experimental studies suggest great opportunities for such treatments, but the results from recent large clinical trials using neuromodulators such as dopamine and fluoxetine are disappointing. The reasons for this are manifold affecting forward translation of results from animals models into the human situation. This “translational road block” is defined by differences between animals and humans with regard to the genetic and epigenetic background, size and anatomy of the brain, cerebral vascular anatomy, immune system, as well as clinical function and behavior. Backward blockade includes the incompatible adaption of targets and outcomes in clinical trials with regard to prior preclinical findings. For example, the design of clinical recovery trials varies widely and was characterized by the selection of different clinical endpoints, the inclusion a broad spectrum of stroke subtypes and clinical syndromes as well as different time windows for treatment initiation after infarct onset. This review will discuss these aspects based on the results of the recent stroke recovery trials with the goal to contribute to the currently biggest unmet need in stroke research - the development of a recovery enhancing therapy that improves the functional outcome of a chronic stroke patient.

Cerebral Ischemia-Reperfusion Is Associated With Upregulation of Cofilin-1 in the Motor Cortex

Cerebral ischemia is one of the leading causes of death. Reperfusion is a critical stage after thrombolysis or thrombectomy, accompanied by oxidative stress, excitotoxicity, neuroinflammation, and defects in synapse structure. The process is closely related to the dephosphorylation of actin-binding proteins (e.g., cofilin-1) by specific phosphatases. Although studies of the molecular mechanisms of the actin cytoskeleton have been ongoing for decades, limited studies have directly investigated reperfusion-induced reorganization of actin-binding protein, and little is known about the gene expression of actin-binding proteins. The exact mechanism is still uncertain. The motor cortex is very important to save nerve function; therefore, we chose the penumbra to study the relationship between cerebral ischemia-reperfusion and actin-binding protein. After transient middle cerebral artery occlusion (MCAO) and reperfusion, we confirmed reperfusion and motor function deficit by cerebral blood flow and gait analysis. PCR was used to screen the high expression mRNAs in penumbra of the motor cortex. The high expression of cofilin in this region was confirmed by immunohistochemistry (IHC) and Western blot (WB). The change in cofilin-1 expression appears at the same time as gait imbalance, especially maximum variation and left front swing. It is suggested that cofilin-1 may partially affect motor cortex function. This result provides a potential mechanism for understanding cerebral ischemia-reperfusion.