Ischemic tolerance is associated with VEGF-C and VEGFR-3 signaling in the mouse hippocampus

Glycyrrhizic Acid Inhibits Hippocampal Neuron Apoptosis by Activating the PI3K/ AKT Signaling Pathway

Glycyrrhizic acid (GA), one of the main active substances in Glycyrrhiza, has anti-inflammatory, anti-viral, and neuroprotective effects. GA can significantly reduce cerebral infarction size in middle cerebral artery occlusion (MCAO) rats and suppress inflammatory responses. However, the underlying mechanism by which GA protects the neuronal system remains poorly understood. Cell proliferation and viability were tested using CCK-8 and Edu assays. The effects of GA on apoptosis were detected using flow cytometry and Tunel assays. Western blotting was performed to assess protein expression. Behavioral experiments were conducted using the Morris water maze and rotation tests. Infarct size was observed using TTC staining. We report that GA protects neurons by inhibiting apoptosis, mainly through the PI3K/AKT pathway in oxygen-glucose deprivation/reoxygenation (OGD/R) and MCAO rat models. GA increases the viability and proliferation of oxygen- and glucose-deprived hippocampal neurons. Hippocampal neuron apoptosis decreased after GA treatment in vitro and in vivo. Furthermore, we determined that GA treatment increased the active state of PI3K and its downstream protein p-AKT, whereas when using a specific inhibitor of PI3K, Y294002, the levels of p-PI3K and p-AKT decreased. Finally, we showed that GA treatment improved spatial memory and motor coordination in MCAO rats, while TTC staining showed that GA decreased cerebral infarct size in MCAO rats. We reveal that GA protects hippocampal neurons by inhibiting their apoptosis, mainly through the PI3K/AKT signaling pathway.

VEGF-C prophylaxis favors lymphatic drainage and modulates neuroinflammation in a stroke model

Meningeal lymphatic vessels (MLVs) promote tissue clearance and immune surveillance in the central nervous system (CNS). Vascular endothelial growth factor-C (VEGF-C) regulates MLV development and maintenance and has therapeutic potential for treating neurological disorders. Herein, we investigated the effects of VEGF-C overexpression on brain fluid drainage and ischemic stroke outcomes in mice. Intracerebrospinal administration of an adeno-associated virus expressing mouse full-length VEGF-C (AAV-mVEGF-C) increased CSF drainage to the deep cervical lymph nodes (dCLNs) by enhancing lymphatic growth and upregulated neuroprotective signaling pathways identified by single nuclei RNA sequencing of brain cells. In a mouse model of ischemic stroke, AAV-mVEGF-C pretreatment reduced stroke injury and ameliorated motor performances in the subacute stage, associated with mitigated microglia-mediated inflammation and increased BDNF signaling in brain cells. Neuroprotective effects of VEGF-C were lost upon cauterization of the dCLN afferent lymphatics and not mimicked by acute post-stroke VEGF-C injection. We conclude that VEGF-C prophylaxis promotes multiple vascular, immune, and neural responses that culminate in a protection against neurological damage in acute ischemic stroke.

Rosuvastatin Enhances Lymphangiogenesis after Myocardial Infarction by Regulating the miRNAs/Vascular Endothelial Growth Factor Receptor 3 (miRNAs/VEGFR3) Pathway

BACKGROUND

Several clinical studies have suggested that the early administration of statins could reduce the risk of in-hospital mortality in acute myocardial infarction (AMI) patients. Recently, some studies have identified that stimulating lymphangiogenesis after AMI could improve cardiac function by reducing myocardial edema and inflammation. This study aimed to identify the effect of rosuvastatin on postinfarct lymphangiogenesis and to identify the underlying mechanism of this effect.

METHOD

Myocardial infarction (MI) was induced by ligation of the left anterior descending coronary artery in mice orally administered rosuvastatin for 7 days. The changes in cardiac function, pathology, and lymphangiogenesis following MI were measured by echocardiography and immunostaining. EdU, Matrigel tube formation, and scratch wound assays were used to evaluate the effect of rosuvastatin on the proliferation, tube formation, and migration of the lymphatic endothelial cell line SVEC4-10. The expression of miR-107-3p, miR-491-5p, and VEGFR3 was measured by polymerase chain reaction (PCR) and Western blotting. A gain-of-function study was performed using miR-107-3p and miR-491-5p mimics.

RESULTS

The rosuvastatin-treated mice had a significantly improved ejection fraction and increased lymphatic plexus density 7 days after MI. Rosuvastatin also reduced myocardial edema and inflammatory response after MI. We used a VEGFR3 inhibitor to partially reverse these effects. Rosuvastatin promoted the proliferation, migration, and tube formation of SVEC4-10 cells. PCR and Western blot analyses revealed that rosuvastatin intervention downregulated miR-107-3p and miR-491-5p and promoted VEGFR3 expression. The gain-of-function study showed that miR-107-3p and miR-491-5p could inhibit the proliferation, migration, and tube formation of SVEC4-10 cells.

CONCLUSION

Rosuvastatin could improve heart function by promoting lymphangiogenesis after MI by regulating the miRNAs/VEGFR3 pathway.

VEGF-C promotes brain-derived fluid drainage, confers neuroprotection, and improves stroke outcomes

Meningeal lymphatic vessels promote tissue clearance and immune surveillance in the central nervous system (CNS). Vascular endothelium growth factor-C (VEGF-C) is essential for meningeal lymphatic development and maintenance and has therapeutic potential for treating neurological disorders, including ischemic stroke. We have investigated the effects of VEGF-C overexpression on brain fluid drainage, single cell transcriptome in the brain, and stroke outcomes in adult mice. Intra-cerebrospinal fluid administration of an adeno-associated virus expressing VEGF-C (AAV-VEGF-C) increases the CNS lymphatic network. Post-contrast T1 mapping of the head and neck showed that deep cervical lymph node size and drainage of CNS-derived fluids were increased. Single nuclei RNA sequencing revealed a neuro-supportive role of VEGF-C via upregulation of calcium and brain-derived neurotrophic factor (BDNF) signaling pathways in brain cells. In a mouse model of ischemic stroke, AAV-VEGF-C pretreatment reduced stroke injury and ameliorated motor performances in the subacute stage. AAV-VEGF-C thus promotes CNS-derived fluid and solute drainage, confers neuroprotection, and reduces ischemic stroke damage.

Short abstract

Intrathecal delivery of VEGF-C increases the lymphatic drainage of brain-derived fluids confers neuroprotection, and improves neurological outcomes after ischemic stroke.

Pre-Clinical Assessment of Roflumilast Therapy in a Thoracic Model of Spinal Cord Injury

The failure of axons to regenerate after a spinal cord injury (SCI) remains one of the greatest challenges in neuroscience. The initial mechanical trauma is followed by a secondary injury cascade, creating a hostile microenvironment, which not only is not permissive to regeneration but also leads to further damage. One of the most promising approaches for promoting axonal regeneration is to maintain the levels of cyclic adenosine monophosphate (cAMP), specifically by a phosphodiesterase-4 (PDE4) inhibitor expressed in neural tissues. Therefore, in our study, we evaluated the therapeutic effect of an FDA-approved PDE4 inhibitor, Roflumilast (Rof), in a thoracic contusion rat model. Results indicate that the treatment was effective in promoting functional recovery. Rof-treated animals showed improvements in both gross and fine motor function. Eight weeks post-injury, the animals significantly recovered by achieving occasional weight-supported plantar steps. Histological assessment revealed a significant decrease in cavity size, less reactive microglia, as well as higher axonal regeneration in treated animals. Molecular analysis revealed that IL-10 and IL-13 levels, as well as VEGF, were increased in the serum of Rof-treated animals. Overall, Roflumilast promotes functional recovery and supports neuroregeneration in a severe thoracic contusion injury model and may be important in SCI treatment.

The Lymphatic Endothelium in the Context of Radioimmuno-Oncology

The study of lymphatic tumor vasculature has been gaining interest in the context of cancer immunotherapy. These vessels constitute conduits for immune cells' transit toward the lymph nodes, and they endow tumors with routes to metastasize to the lymph nodes and, from them, toward distant sites. In addition, this vasculature participates in the modulation of the immune response directly through the interaction with tumor-infiltrating leukocytes and indirectly through the secretion of cytokines and chemokines that attract leukocytes and tumor cells. Radiotherapy constitutes the therapeutic option for more than 50% of solid tumors. Besides impacting transformed cells, RT affects stromal cells such as endothelial and immune cells. Mature lymphatic endothelial cells are resistant to RT, but we do not know to what extent RT may affect tumor-aberrant lymphatics. RT compromises lymphatic integrity and functionality, and it is a risk factor to the onset of lymphedema, a condition characterized by deficient lymphatic drainage and compromised tissue homeostasis. This review aims to provide evidence of RT's effects on tumor vessels, particularly on lymphatic endothelial cell physiology and immune properties. We will also explore the therapeutic options available so far to modulate signaling through lymphatic endothelial cell receptors and their repercussions on tumor immune cells in the context of cancer. There is a need for careful consideration of the RT dosage to come to terms with the participation of the lymphatic vasculature in anti-tumor response. Here, we provide new approaches to enhance the contribution of the lymphatic endothelium to radioimmuno-oncology.

Cohort study on the differential expression of inflammatory and angiogenic factors in thrombi, cerebral and peripheral plasma following acute large vessel occlusion stroke

Inflammation plays an important role in the pathogenesis of stroke. The differential expression of inflammatory and angiogenic factors in thrombi and plasma remain undefined. In this observational cohort study, we evaluated angiogenic factors and inflammatory cytokines, in cerebral thrombi, local cerebral plasma (CP), and peripheral plasma (PP) in patients with acute ischemic stroke. Protein analysis of thrombi, CP and PP were used to measure angiogenic and inflammatory proteins using electrochemiluminescence. Our data indicate that VEGF-A, VEGF-C, bFGF, IL-4, IL-13, IL-1β, IL-2, IL-8, IL-16, IL-6 and IL-12p70 were higher in the thrombi of acute ischemic stroke patients than in the CP and PP of stroke patients. Moreover, the protein levels of GM-CSF were lower in the PP than in the CP and the clot. Moreover, VEGF-D, Flt-1, PIGF, TIE-2, IL-5, TNF-β, IL-15, IL-12/IL-23p40, IFN-γ and IL-17A were higher in PP and CP than in thrombi. Our results show that cytokines mediating the inflammatory response and proteins involved in angiogenesis are differentially expressed in thrombi within the cerebral and peripheral circulations. These data highlight the importance of identifying new biomarkers in different compartments of the circulatory system and in thrombi that may be used for the diagnosis and treatment of stroke patients.

Spontaneous, transient adenosine release is not enhanced in the CA1 region of hippocampus during severe ischemia models

Ischemic stroke causes damage in the brain, and a slow buildup of adenosine is neuroprotective during ischemic injury. Spontaneous, transient adenosine signaling, lasting only 3 s per event, has been discovered that increases in frequency in the caudate-putamen during early stages of mild ischemia-reperfusion injury. However, spontaneous adenosine changes have not been studied in the hippocampus during ischemia, an area highly susceptible to stroke. Here, we investigated changes of spontaneous, transient adenosine in the CA1 region of rat hippocampus during three different models of the varied intensity of ischemia. During the early stages of the milder bilateral common carotid artery occlusion (BCCAO) model, there were fewer spontaneous, transient adenosine, but no change in the concentration of individual events. In contrast, during the moderate 2 vertebral artery occlusion (2VAO) and severe 4 vessel occlusion (4VO) models, both the frequency of spontaneous, transient adenosine and the average event adenosine concentration decreased. Blood flow measurements validate that the ischemia models decreased blood flow, and corresponding pathological changes were observed by transmission electron microscopy (TEM). 4VO occlusion showed the most severe damage in histology and BCCAO showed the least. Overall, our data suggest that there is no enhanced spontaneous adenosine release in the hippocampus during moderate and severe ischemia, which could be due to depletion of the rapidly releasable adenosine pool. Thus, during ischemic stroke, there are fewer spontaneous adenosine events that could inhibit neurotransmission, which might lead to more damage and less neuroprotection in the hippocampus CA1 region. Read the Editorial Highlight for this article on page 800.

Vascular endothelial growth factor receptor-3 regulates astroglial glutamate transporter-1 expression via mTOR activation in reactive astrocytes following pilocarpine-induced status epilepticus

Recent evidence has shown that the vascular endothelial growth factor (VEGF) system plays a crucial role in several neuropathological processes. We previously reported an upregulation of VEGF-C and its receptor, VEGFR-3, in reactive astrocytes after the onset of status epilepticus (SE). However, it remains unknown, which molecules act as downstream signals following VEGFR-3 upregulation, and are involved in reactive astrogliosis after SE. Therefore, we investigated whether VEGFR-3 upregulation within reactive astrocytes is associated with the activation of mammalian target of rapamycin (mTOR) signaling, which we confirmed by assaying for the phosphorylated form of S6 protein (pS6), and whether VEGFR-3-mediated mTOR activation induces astroglial glutamate transporter-1 (GLT-1) expression in the hippocampus after pilocarpine-induced SE. We found that spatiotemporal expression of pS6 was consistent with VEGFR-3 expression in the hippocampus after SE, and that both pS6 and VEGFR-3 were highly expressed in SE-induced reactive astrocytes. Treatment with the mTOR inhibitor rapamycin decreased astroglial VEGFR-3 expression and GLT-1 expression after SE. Treatment with a selective inhibitor for VEGFR-3 attenuated astroglial pS6 expression as well as suppressed GLT-1 expression and astroglial reactivity in the hippocampus after SE. These findings demonstrate that VEGFR-3-mediated mTOR activation could contribute to the regulation of GLT-1 expression in reactive astrocytes during the subacute phase of epilepsy. In conclusion, the present study suggests that VEGFR-3 upregulation in reactive astrocytes may play a role in preventing hyperexcitability induced by continued seizure activity.

Phthalide derivative CD21 ameliorates ischemic brain injury in a mouse model of global cerebral ischemia: involvement of inhibition of NLRP3

The activation of NLRP3 inflammasome is closely related to ischemic brain injury and inhibition of NLRP3 inflammasome activation may be a new therapeutic strategy for ischemic stroke. Our previous studies showed that ligustilide (LIG) had a dose-dependent neuroprotective effect on various models of cerebral ischemia and dementia in vivo and in vitro. CD21, a kind of phthalide derivative, was modified from LIG. In this study, we established a global cerebral ischemia-reperfusion model in mice by bilateral common carotid artery ligation (2VO), and explored the neuroprotective effect of CD21 and its anti-inflammatory mechanism on cerebral ischemia mice. CD21 significantly improved weight loss, neurobehavioral deficits and neurons loss in hippocampal CA1 and caudate putamen (CPu) subregions, which were induced by 2VO in mice. CD21 significantly inhibited the overactivation of astrocyte and microglia, and decreased the mRNA level of IL-6, TNF-α and IL-1β. Moreover, CD21 significantly inhibited the activation of TLR4/NF-κB signaling pathway mediated by HMGB1 and NLRP3/ASC/Caspase-1 signaling pathway mediated by Cathepsin B, thus inhibiting the activation of NLRP3 inflammasome. Our results demonstrated that CD21 may exert a neuroprotection by inhibiting NLRP3 inflammasome activation after cerebral ischemia. These findings provide a new strategy for the treatment of ischemic stroke.

Cell Secretome: Basic Insights and Therapeutic Opportunities for CNS Disorders

Transplantation of stem cells, in particular mesenchymal stem cells (MSCs), stands as a promising therapy for trauma, stroke or neurodegenerative conditions such as spinal cord or traumatic brain injuries (SCI or TBI), ischemic stroke (IS), or Parkinson's disease (PD). Over the last few years, cell transplantation-based approaches have started to focus on the use of cell byproducts, with a strong emphasis on cell secretome. Having this in mind, the present review discusses the current state of the art of secretome-based therapy applications in different central nervous system (CNS) pathologies. For this purpose, the following topics are discussed: (1) What are the main cell secretome sources, composition, and associated collection techniques; (2) Possible differences of the therapeutic potential of the protein and vesicular fraction of the secretome; and (3) Impact of the cell secretome on CNS-related problems such as SCI, TBI, IS, and PD. With this, we aim to clarify some of the main questions that currently exist in the field of secretome-based therapies and consequently gain new knowledge that may help in the clinical application of secretome in CNS disorders.

Impaired meningeal lymphatic vessel development worsens stroke outcome

The discovery of meningeal lymphatic vessels (LVs) has sparked interest in identifying their role in diseases of the central nervous system. Similar to peripheral LVs, meningeal LVs depend on vascular endothelial growth factor receptor-3 (VEGFR3) signaling for development. Here we characterize the effect of stroke on meningeal LVs, and the impact of meningeal lymphatic hypoplasia on post-stroke outcomes. We show that photothrombosis (PT), but not transient middle cerebral artery occlusion (tMCAo), induces meningeal lymphangiogenesis in young male C57Bl/J6 mice. We also show that Vegfr3^wt/mut mice develop significantly fewer meningeal LVs than Vegfr3^wt/wt mice. Again, meningeal lymphangiogenesis occurs in the alymphatic zone lateral to the sagittal sinus only after PT-induced stroke in Vegfr3^wt/wt mice. Interestingly, Vegfr3^wt/mut mice develop larger stroke volumes than Vegfr3^wt/wt mice after tMCAo, but not after PT. Our results reveal differences between PT and tMCAo models of stroke and underscore the need to consider method of stroke induction when investigating the role of meningeal lymphatics. Taken together, our data indicate that ischemic injury can induce the growth of meningeal LVs and that the absence of these LVs can impact post-stroke outcomes.

Increased expression of vascular endothelial growth factor-C and vascular endothelial growth factor receptor-3 after pilocarpine-induced status epilepticus in mice

Vascular endothelial growth factor (VEGF)-C and its receptor, vascular endothelial growth factor receptor (VEGFR)-3, are responsible for lymphangiogenesis in both embryos and adults. In epilepsy, the expression of VEGF-C and VEGFR-3 was significantly upregulated in the human brains affected with temporal lobe epilepsy. Moreover, pharmacologic inhibition of VEGF receptors after acute seizures could suppress the generation of spontaneous recurrent seizures, suggesting a critical role of VEGF-related signaling in epilepsy. Therefore, in the present study, the spatiotemporal expression of VEGF-C and VEGFR-3 against pilocarpine-induced status epilepticus (SE) was investigated in C57BL/6N mice using immunohistochemistry. At 1 day after SE, hippocampal astrocytes and microglia were activated. Pyramidal neuronal death was observed at 4 days after SE. In the subpyramidal zone, VEGF-C expression gradually increased and peaked at 7 days after SE, while VEGFR-3 was significantly upregulated at 4 days after SE and began to decrease at 7 days after SE. Most VEGF-C/VEGFR-3-expressing cells were pyramidal neurons, but VEGF-C was also observed in some astrocytes in sham-manipulated animals. However, at 4 days and 7 days after SE, both VEGFR-3 and VEGF-C immunoreactivities were observed mainly in astrocytes and in some microglia of the stratum radiatum and lacunosum-moleculare of the hippocampus, respectively. These data indicate that VEGF-C and VEGFR-3 can be upregulated in hippocampal astrocytes and microglia after pilocarpine-induced SE, providing basic information about VEGF-C and VEGFR-3 expression patterns following acute seizures.

A Novel Role of VEGFC in Cerebral Ischemia With Lung Injury

Cerebral ischemia (CI) is a severe brain injury resulting in a variety of motor impairments combined with secondary injury in remote organs, especially the lung. This condition occurs due to insufficient blood supply to the brain during infancy. However, it has a molecular linkage that needs to be thoroughly covered. Here, we report on the role of vascular endothelial growth factor C (VEGFC) in lung injury induced by CI. The middle cerebral artery occlusion (MCAO) was depended to establish the animal model of CI. Rats were used and brain ischemia was confirmed through TTC staining. Serum was used for protein chip analysis to study the proteomic interaction. Immunohistochemistry analyses were used to quantify and locate the VEGFC in the lung and brain. The role of VEGFC was detected by siVEGFC technology in SY5Y, HUCEV, and A549 cell lines, under normal and oxygen glucose deprivation (OGD) conditions in vitro. As a result, the TTC staining demonstrated that the model of brain ischemia was successfully established, and MPO experiments reported that lung damage was induced in MCAO rats. VEGFC levels were up-regulated in serum. On the other hand, immunohistochemistry showed that VEGFC increased significantly in the cytoplasm of neurons, the endothelium of small trachea and the lung cells of CI animals. On a functional level, siVEGFC effectively inhibited the proliferation of SY5Y cells and decreased the viability of HUVEC cells in normal cell lines. But under OGD conditions, siVEGFC decreased the growth of HUVEC and increased the viability of A549 cells, while no effect was noticed on SYSY cells. Therefore, we confirmed the different role of VEGFC played in neurons and lung cells in cerebral ischemia-reperfusion injury. These findings may contribute to the understanding the molecular linkage of brain ischemia and lung injury, which therefore provides a new idea for the therapeutic approach to cerebral ischemia-reperfusion.

An Experimental Study on Repeated Brief Ischemia in Promoting Sciatic Nerve Repair and Regeneration in Rats

BACKGROUND

Research has shown that ischemic preconditioning reduced the severity of ischemia-reperfusion injury in brain in rats, we have a hypothesis that repeated brief ischemia has positive effects on peripheral nerve damage. This study was conducted to investigate the potential protective effects of repeated brief ischemia on peripheral nerve regeneration using a rat model of experimental sciatic nerve transection injury.

METHODS

Treatment groups (groups A-D) received repeated, brief ischemia every 1 day/2 days/3 days/7 days. After surgery for 4, 8, 12 weeks, we evaluated sciatic functional index test, gastrocnemius muscle wet mass, axon and nerve fiber diameter, density, G-ratio, immunohistochemistry of S-100, vascular endothelial growth factor (VEGF), and the ultrastructure of the nerves.

RESULTS

Sciatic functional index test and muscle wet mass were improved on the repeated brief ischemia groups. Ischemia treatment resulted in a significant increase in axon and nerve fiber density as well as S-100 and VEGF-positive cell, which indicated that repeated brief ischemia promotes Schwann cell proliferation and reconstruction.

CONCLUSIONS

This study exhibits the positive effects of repeated brief ischemia in sciatic nerve transection injury, possibly in part because it can improve VEGF and the physiologic state of Schwann cells in the ischemic environment and then accelerate the ability of neurite outgrow.

Protective Effect of Klotho against Ischemic Brain Injury Is Associated with Inhibition of RIG-I/NF-κB Signaling

Aging is the greatest independent risk factor for the occurrence of stroke and poor outcomes, at least partially through progressive increases in oxidative stress and inflammation with advanced age. Klotho is an antiaging gene, the expression of which declines with age. Klotho may protect against neuronal oxidative damage that is induced by glutamate. The present study investigated the effects of Klotho overexpression and knockdown by an intracerebroventricular injection of a lentiviral vector that encoded murine Klotho (LV-KL) or rat Klotho short-hairpin RNA (LV-KL shRNA) on cerebral ischemia injury and the underlying anti-neuroinflammatory mechanism. The overexpression of Klotho induced by LV-KL significantly improved neurobehavioral deficits and increased the number of live neurons in the hippocampal CA1 and caudate putamen subregions 72 h after cerebral hypoperfusion that was induced by transient bilateral common carotid artery occlusion (2VO) in mice. The overexpression of Klotho significantly decreased the immunoreactivity of glial fibrillary acidic protein and ionized calcium binding adaptor molecule-1, the expression of retinoic-acid-inducible gene-I, the nuclear translocation of nuclear factor-κB, and the production of proinflammatory cytokines (tumor necrosis factor α and interleukin-6) in 2VO mice. The knockdown of Klotho mediated by LV-KL shRNA in the brain exacerbated neurological dysfunction and cerebral infarct after 22 h of reperfusion following 2 h middle cerebral artery occlusion in rats. These findings suggest that Klotho itself or enhancers of Klotho may compensate for its aging-related decline, thus providing a promising therapeutic approach for acute ischemic stroke during advanced age.

Effect of VEGF on Inflammatory Regulation, Neural Survival, and Functional Improvement in Rats following a Complete Spinal Cord Transection

After complete transection of the thoracic spinal segment, neonatal rats exhibit spontaneous locomotor recovery of hindlimbs, but this recovery is not found in adult rats after similar injury. The potential mechanism related to the difference in recovery of neonatal and adult rats remains unknown. In this study, 342 animals were analyzed. The vascular endothelial growth factor (VEGF) level in spinal segments below injury sites was significantly higher in postnatal day 1 rats (P1) compared with 28-day-old adult rats (P28) following a complete T9 transection. VEGF administration in P28 rats with T9 transection significantly improved the functional recovery; by contrast, treatment with VEGF receptor inhibitors in P1 rats with T9 transection slowed down the spontaneous functional recovery. Results showed more neurons reduced in the lumbar spinal cord and worse local neural network reorganization below injury sites in P28 rats than those in P1 rats. Transynaptic tracing with pseudorabies virus and double immunofluorescence analysis indicated that VEGF treatment in P28 rats alleviated the reduced number of neurons and improved their network reorganization. VEGF inhibition in neonates resulted in high neuronal death rate and deteriorated network reorganization. In in vivo studies, T9 transection induced less increase in the number of microglia in the spinal cord in P1 animals than P28 animals. VEGF treatment reduced the increase in microglial cells in P28 animals. VEGF administration in cultured spinal motoneurons prevented lipopolysaccharide (LPS)-induced neuronal death and facilitated neurite growth. Western blots of the samples of lumbar spinal cord after spinal transection and cultured spinal motoneurons showed a lower level of Erk1/2 phosphorylation after the injury or LPS induction compared with that in the control. The phosphorylation level increased after VEGF treatment. In conclusion, VEGF is a critical mediator involved in functional recovery after spinal transection and can be considered a potential target for clinical therapy.

WNK-Cab39-NKCC1 signaling increases the susceptibility to ischemic brain damage in hypertensive rats

With-no-lysine kinase (WNK) and Na⁺-K⁺-2Cl^- cotransporter 1 (NKCC1) are involved in the pathogenesis of hypertension. In this study, we investigated the WNK-NKCC1 signaling pathway in spontaneously hypertensive rats (SHR) and their associated susceptibility to stroke injury. Basal NKCC1 protein levels were higher in SHR than in normotensive Wistar Kyoto (WKY) rat brains. After inducing ischemic stroke, adult male WKY and SHR received either saline or NKCC1 inhibitor bumetanide (10 mg/kg/day, i.p.) starting at 3-h post-reperfusion. NKCC1 inhibition blunted the extent of ischemic infarction in SHR and improved their neurobehavioral functions. Interestingly, ischemia led to increased NKCC1 phosphorylation in SHR but not in WKY rats. Pronounced elevation of WNK1, WNK2 and WNK4 protein and downregulation of WNK3 were detected in ischemic SHR, but not in ischemic WKY rats. Upregulation of WNK-NKCC1 complex in ischemic SHR brain was associated with increased Ca²⁺-binding protein 39 (Cab39), without increases in Ste20-related proline alanine-rich kinase or oxidative stress-responsive kinase-1. Moreover, subacute middle cerebral artery stroke human brain autopsy exhibited increased expression of NKCC1 protein. We conclude that augmented WNK-Cab39-NKCC1 signaling in SHR is associated with an increased susceptibility to ischemic brain damage and may serve as a novel target for anti-hypertensive and anti-ischemic stroke therapy.

An in vivo study of hypoxia-inducible factor-1α signaling in ginsenoside Rg1-mediated brain repair after hypoxia/ischemia brain injury

BACKGROUND

Hypoxia/ischemia (HI) brain injury is a common central nervous system insult in newborns. Studies have demonstrated bioactivity of ginsenoside Rg1 in increasing neural viability and promoting angiogenesis. However, there are few reports on roles of Rg1 in brain repair of neonatal HI, and the mechanisms involved are unclear.

METHODS

a neonatal HI model was established by a modified Rice-Vannucci model (RVM) and pups received ginsenoside Rg1 or monosialotetrahexosyl ganglioside (GM1) treatment. Neurological function and pathologic damage of rats were evaluated. Cellular apoptosis was detected with Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Immunohistochemistry for von willebrand factor (vwf) was used to label micro vessels. Expression levels of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and cleaved caspase 3 (CC3) were detected by western blot.

RESULTS

Both Rg1 and GM1 reduced neurological impairment and pathologic damage after HI by enhancing neural survival. Rg1, but not GM1, could also facilitate angiogenesis after HI. These pharmacological effects of Rg1 may be attributed to regulation of expression level of VEGF and CC3 and HIF-1α signaling pathway was involved.

CONCLUSION

Rg1 plays a neuroprotective role in brain repair following neonatal HI, and HIF-1α is a potential target for therapeutic intervention in neonates with HI brain injury.

Transcriptional Coactivator and Chromatin Protein PC4 Is Involved in Hippocampal Neurogenesis and Spatial Memory Extinction

Although the elaborate combination of histone and non-histone protein complexes defines chromatin organization and hence regulates numerous nuclear processes, the role of chromatin organizing proteins remains unexplored at the organismal level. The highly abundant, multifunctional, chromatin-associated protein and transcriptional coactivator positive coactivator 4 (PC4/Sub1) is absolutely critical for life, because its absence leads to embryonic lethality. Here, we report results obtained with conditional PC4 knock-out (PC4(f/f) Nestin-Cre) mice where PC4 is knocked out specifically in the brain. Compared with the control (PC4(+/+) Nestin-Cre) mice, PC4(f/f) Nestin-Cre mice are smaller with decreased nocturnal activity but are fertile and show no motor dysfunction. Neurons in different areas of the brains of these mice show sensitivity to hypoxia/anoxia, and decreased adult neurogenesis was observed in the dentate gyrus. Interestingly, PC4(f/f) Nestin-Cre mice exhibit a severe deficit in spatial memory extinction, whereas acquisition and long term retention were unaffected. Gene expression analysis of the dorsal hippocampus of PC4(f/f) Nestin-Cre mice revealed dysregulated expression of several neural function-associated genes, and PC4 was consistently found to localize on the promoters of these genes, indicating that PC4 regulates their expression. These observations indicate that non-histone chromatin-associated proteins like PC4 play a significant role in neuronal plasticity.