Minocycline improves functional outcomes, memory deficits, and histopathology after endovascular perforation-induced subarachnoid hemorrhage in rats

Minocycline Acts as a Neuroprotective Agent Against Tramadol-Induced Neurodegeneration: Behavioral and Molecular Evidence

Background

Previous evidence indicates that tramadol (TRA) can lead to neurodegenerative events and minocycline (MIN) has neuroprotective properties.

Aim of the Study

The current research evaluated the neuroprotective effects of MIN for TRA-promoted neurodegeneration.

Methods

Sixty adult male rats were placed into the following groups: 1 (received 0.7 ml/rat of normal saline, IP), 2 (received 50 mg/kg of TRA, i.p.), 3, 4, 5 (administered TRA as 50 mg/kg simultaneously with MIN at 20, 40, and 60 mg/kg, IP, respectively), and 6 (received MIN alone as 60 mg/kg, IP). The treatment procedure was 21 days. An open field test (OFT) was used to measure motor activity and anxiety-related behavior. Furthermore, oxidative stress; hippocampal inflammation; apoptotic parameters as well as activity of mitochondrial complexes I, II, III, and IV; ATP levels; and mitochondrial membrane potential (MMP) were evaluated. In addition, histomorphological alteration was assessed in two regions of the hippocampus: Cornu Ammonis (CA1) and dentate gyrus (DG).

Results

MIN treatment could inhibit TRA-induced anxiety and motor activity disturbances (P < 0.05). In addition, MIN could attenuate reactive oxygen species (ROS), H2O2, oxidized glutathione (GSSG), and malondialdehyde (MDA) level (P < 0.05), while there was increased reduced glutathione (GSH), total antioxidant capacity (TAC), ATP, MMP, and BCL2 levels (P < 0.05) and also elevation of SOD, GPX, GSR (P < 0.05), and mitochondrial complexes I, II, III, and IV activity (P < 0.05) in TRA-treated rats. In consistence with these findings, MIN could reduce TNF/TNF-α, IL1B/IL1-β, BAX, and CASP3 levels (P < 0.05) in TRA-treated rats. MIN also restored the quantitative (P < 0.05) and qualitative histomorphological sequels of TRA in both CA1 and DG areas of the hippocampus.

Conclusions

MIN probably has repositioning capability for inhibition of TRA-induced neurodegeneration via modulation of inflammation, oxidative stress, apoptosis, and mitochondrial disorders.

Matrix metalloproteinase 9 (MMP-9) activity, hippocampal extracellular free water, and cognitive deficits are associated with each other in early phase psychosis

Increasing evidence points toward the role of the extracellular matrix, specifically matrix metalloproteinase 9 (MMP-9), in the pathophysiology of psychosis. MMP-9 is a critical regulator of the crosstalk between peripheral and central inflammation, extracellular matrix remodeling, hippocampal development, synaptic pruning, and neuroplasticity. Here, we aim to characterize the relationship between plasma MMP-9 activity, hippocampal microstructure, and cognition in healthy individuals and individuals with early phase psychosis. We collected clinical, blood, and structural and diffusion-weighted magnetic resonance imaging data from 39 individuals with early phase psychosis and 44 age and sex-matched healthy individuals. We measured MMP-9 plasma activity, hippocampal extracellular free water (FW) levels, and hippocampal volumes. We used regression analyses to compare MMP-9 activity, hippocampal FW, and volumes between groups. We then examined associations between MMP-9 activity, FW levels, hippocampal volumes, and cognitive performance assessed with the MATRICS battery. All analyses were controlled for age, sex, body mass index, cigarette smoking, and years of education. Individuals with early phase psychosis demonstrated higher MMP-9 activity (p < 0.0002), higher left (p < 0.05) and right (p < 0.05) hippocampal FW levels, and lower left (p < 0.05) and right (p < 0.05) hippocampal volume than healthy individuals. MMP-9 activity correlated positively with hippocampal FW levels (all participants and individuals with early phase psychosis) and negatively with hippocampal volumes (all participants and healthy individuals). Higher MMP-9 activity and higher hippocampal FW levels were associated with slower processing speed and worse working memory performance in all participants. Our findings show an association between MMP-9 activity and hippocampal microstructural alterations in psychosis and an association between MMP-9 activity and cognitive performance. Further, more extensive longitudinal studies should examine the therapeutic potential of MMP-9 modulators in psychosis.

Repurposing of pexidartinib for microglia depletion and renewal

Pexidartinib (PLX3397) is a small molecule receptor tyrosine kinase inhibitor of colony stimulating factor 1 receptor (CSF1R) with moderate selectivity over other members of the platelet derived growth factor receptor family. It is approved for treatment of tenosynovial giant cell tumors (TGCT). CSF1R is highly expressed by microglia, which are macrophages of the central nervous system (CNS) that defend the CNS against injury and pathogens and contribute to synapse development and plasticity. Challenged by pathogens, apoptotic cells, debris, or inflammatory molecules they adopt a responsive state to propagate the inflammation and eventually return to a homeostatic state. The phenotypic switch may fail, and disease-associated microglia contribute to the pathophysiology in neurodegenerative or neuropsychiatric diseases or long-lasting detrimental brain inflammation after brain, spinal cord or nerve injury or ischemia/hemorrhage. Microglia also contribute to the growth permissive tumor microenvironment of glioblastoma (GBM). In rodents, continuous treatment for 1-2 weeks via pexidartinib food pellets leads to a depletion of microglia and subsequent repopulation from the remaining fraction, which is aided by peripheral monocytes that search empty niches for engraftment. The putative therapeutic benefit of such microglia depletion or forced renewal has been assessed in almost any rodent model of CNS disease or injury or GBM with heterogeneous outcomes, but a tendency of partial beneficial effects. So far, microglia monitoring e.g. via positron emission imaging is not standard of care for patients receiving Pexidartinib (e.g. for TGCT), so that the depletion and repopulation efficiency in humans is still largely unknown. Considering the virtuous functions of microglia, continuous depletion is likely no therapeutic option but short-lasting transient partial depletion to stimulate microglia renewal or replace microglia in genetic disease in combination with e.g. stem cell transplantation or as part of a multimodal concept in treatment of glioblastoma appears feasible. The present review provides an overview of the preclinical evidence pro and contra microglia depletion as a therapeutic approach.

Clinical Potential of Immunotherapies in Subarachnoid Hemorrhage Treatment: Mechanistic Dissection of Innate and Adaptive Immune Responses

Subarachnoid hemorrhage (SAH), classified as a medical emergency, is a devastating and severe subtype of stroke. SAH induces an immune response, which further triggers brain injury; however, the underlying mechanisms need to be further elucidated. The current research is predominantly focused on the production of specific subtypes of immune cells, especially innate immune cells, post-SAH onset. Increasing evidence suggests the critical role of immune responses in SAH pathophysiology; however, studies on the role and clinical significance of adaptive immunity post-SAH are limited. In this present study, we briefly review the mechanistic dissection of innate and adaptive immune responses post-SAH. Additionally, we summarized the experimental studies and clinical trials of immunotherapies for SAH treatment, which may form the basis for the development of improved therapeutic approaches for the clinical management of SAH in the future.

The protective effect of low-dose minocycline on brain microvascular ultrastructure in a rodent model of subarachnoid hemorrhage

The multifaceted nature of subarachnoid hemorrhage (SAH) pathogenesis is poorly understood. To date, no pharmacological agent has been found to be efficacious for the prevention of brain injury when used for acute SAH intervention. This study was undertaken to evaluate the beneficial effects of low-dose neuroprotective agent minocycline on brain microvascular ultrastructures that have not been studied in detail. We studied SAH brain injury using an in vivo prechiasmatic subarachnoid hemorrhage rodent model. We analyzed the qualitative and quantitative ultrastructural morphology of capillaries and surrounding neuropil in the rodent brains with SAH and/or minocycline administration. Here, we report that low-dose minocycline (1 mg/kg) displayed protective effects on capillaries and surrounding cells from significant SAH-induced changes. Ultrastructural morphology analysis revealed also that minocycline stopped endothelial cells from abnormal production of vacuoles and vesicles that compromise blood-brain barrier (BBB) transcellular transport. The reported ultrastructural abnormalities as well as neuroprotective effects of minocycline during SAH were not directly mediated by inhibition of MMP-2, MMP-9, or EMMPRIN. However, SAH brain tissue treated with minocycline was protected from development of other morphological features associated with oxidative stress and the presence of immune cells in the perivascular space. These data advance the knowledge on the effect of SAH on brain tissue ultrastructure in an SAH rodent model and the neuroprotective effect of minocycline when administered in low doses.

Altered hippocampal functional connectivity after the rupture of anterior communicating artery aneurysm

BACKGROUND AND PURPOSE

Aneurysmal subarachnoid hemorrhage (SAH) predisposes hippocampal injury, a major cause of follow-up cognitive impairment. Our previous study has revealed an abnormal resting-state brain network in patients after the rupture of anterior communicating artery (ACoA) aneurysm. However, the functional connectivity (FC) characteristics of the hippocampus and its relationship with cognitive performance in these patients remain unknown.

METHODS

This study ultimately included 26 patients and 19 age- and sex-matched controls who completed quality control for resting-state functional magnetic resonance imaging (fMRI). The mean time series for each side of the hippocampus was extracted from individuals and then a seed-to-voxel analysis was performed. We compared the difference in FC strength between the two groups and subsequently analyzed the correlations between abnormal FC and their cognitive performance.

RESULTS

The results of bilateral hippocampus-based FC analysis were largely consistent. Compared with the healthy controls, patients after the rupture of ACoA aneurysm exhibited significantly decreased FC between the hippocampus and other brain structures within the Papez circuit, including bilateral anterior and middle cingulate cortex (MCC), bilateral medial superior frontal gyrus, and left inferior temporal gyrus (ITG). Instead, increased FC between the hippocampus and bilateral insula was observed. Correlation analyses showed that more subjective memory complaints or lower total cognitive scores were associated with decreased connectivity in the hippocampus and several brain regions such as left anterior cingulate cortex (ACC) and frontotemporal cortex.

CONCLUSION

These results extend our previous findings and suggest that patients with ruptured ACoA aneurysm exist hypoconnectivity between the hippocampus and multiple brain regions within the Papez circuit. Deactivation of the Papez circuit may be a crucial neural mechanism related to cognitive deficits in patients after the rupture of ACoA aneurysm.

Alpha-asarone ameliorates neurological deterioration of intracerebral hemorrhagic rats by alleviating secondary brain injury via anti-excitotoxicity pathways

BACKGROUND

Secondary brain injury (SBI) has been confirmed as a leading cause for the poor prognosis of patients suffering from intracerebral hemorrhage (ICH). SBI co-exists in ischemia and hemorrhagic stroke. Neuro-excitotoxicity is considered the initiating factor of ICH-induced SBI. Our previous research has revealed alpha-asarone (ASA)'s efficacy against cerebral ischemia-reperfusion stroke by mitigating neuro-excitotoxicity. It is not yet known if ASA exhibit neuroprotection against ICH.

PURPOSE

This work aimed to investigate ASA's therapeutic effects and potential mechanisms of action against ICH in a classic rat model induced by collagenase Ⅶ injection.

METHODS

An in vivo ICH model of Sprague-Dawley rats was established by collagenase Ⅶ injection. We administrated different ASA doses (10, 20, or 40 mg/kg, i.p.) at 2 h post-ICH. Then, rats' short- and long-term neurobehavioral function, bodyweight change, and learning and memory ability were blindly evaluated. Histological, Nissl, and flow cytometry were applied to assess the neuronal damage post-ICH. The wet/dry method and Evans blue extravasation estimated brain edema and blood-brain barrier function. Pathway-related proteins were investigated by immunofluorescence staining, enzyme-linked immunosorbent assay, and Western-blot analysis.

RESULTS

The results demonstrated that ASA ameliorated neurological deterioration, bodyweight loss, and learning and memory ability of ICH rats. Histological, Nissl, and flow cytometry analyses showed that ASA reduced neuronal damage and apoptosis post-ICH. Besides, ASA probably mitigated brain edema and blood-brain barrier dysfunction via inhibiting astrocyte activation and consequent pro-inflammatory response. The mechanism investigation attributed ASA's efficacy to the following aspects: 1) promoting sodium ion excretion, thus blocking excitatory signal transduction along the axon; 2) preventing glutamate-involved pathways, i.e., decrease of N-methyl-d-aspartic acid receptor subunit 2B, increase of glutamate transporter-1, and alleviation of calcium-related cascades, mitochondrion-associated apoptosis, and neuronal autophagy; 3) enhancing the expression of GABA_ARs, thus abating neuronal excitotoxicity.

CONCLUSION

Our study first confirmed the effect of ASA on ameliorating the neurobehavioral deterioration of ICH rats, possibly via alleviation of glutamate-involved neuro-excitotoxicity, i.e., calcium cascades, mitochondrion-involved apoptosis, neuronal autophagy, and astrocyte-related inflammation. These findings not only provided a promising drug candidate for clinical treatment of ICH but also shed light on the future drug discovery against ICH.

Minocycline Attenuates Microglia/Macrophage Phagocytic Activity and Inhibits SAH-Induced Neuronal Cell Death and Inflammation

Background

Neuroprotective treatment strategies aiming at interfering with either inflammation or cell death indicate the importance of these mechanisms in the development of brain injury after subarachnoid hemorrhage (SAH). This study was undertaken to evaluate the influence of minocycline on microglia/macrophage cell activity and its neuroprotective and anti-inflammatory impact 14 days after aneurismal SAH in mice.

Methods

Endovascular filament perforation was used to induce SAH in mice. SAH + vehicle-operated mice were used as controls for SAH vehicle-treated mice and SAH + minocycline-treated mice. The drug administration started 4 h after SAH induction and was daily repeated until day 7 post SAH and continued until day 14 every second day. Brain cryosections were immunolabeled for Iba1 to detect microglia/macrophages and NeuN to visualize neurons. Phagocytosis assay was performed to determine the microglia/macrophage activity status. Apoptotic cells were stained using terminal deoxyuridine triphosphate nick end labeling. Real-time quantitative polymerase chain reaction was used to estimate cytokine gene expression.

Results

We observed a significantly reduced phagocytic activity of microglia/macrophages accompanied by a lowered spatial interaction with neurons and reduced neuronal apoptosis achieved by minocycline administration after SAH. Moreover, the SAH-induced overexpression of pro-inflammatory cytokines and neuronal cell death was markedly attenuated by the compound.

Conclusions

Minocycline treatment may be implicated as a therapeutic approach with long-term benefits in the management of secondary brain injury after SAH in a clinically relevant time window.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12028-022-01511-5.

Effects of TRAM-34 and minocycline on neuroinflammation caused by diabetic ketoacidosis in a rat model

INTRODUCTION

Diabetic ketoacidosis (DKA) causes acute and chronic neuroinflammation that may contribute to cognitive decline in patients with type 1 diabetes. We evaluated the effects of agents that reduce neuroinflammation (triarylmethane-34 (TRAM-34) and minocycline) during and after DKA in a rat model.

RESEARCH DESIGN AND METHODS

Juvenile rats with DKA were treated with insulin and saline, either alone or in combination with TRAM-34 (40 mg/kg intraperitoneally twice daily for 3 days, then daily for 4 days) or minocycline (45 mg/kg intraperitoneally daily for 7 days). We compared cytokine and chemokine concentrations in brain tissue lysates during DKA among the three treatment groups and in normal controls and diabetic controls (n=9-15/group). We also compared brain inflammatory mediator levels in these same groups in adult diabetic rats that were treated for DKA as juveniles.

RESULTS

Brain tissue concentrations of chemokine (C-C) motif ligand (CCL)3, CCL5 and interferon (IFNγ) were increased during acute DKA, as were brain cytokine composite scores. Both treatments reduced brain inflammatory mediator levels during acute DKA. TRAM-34 predominantly reduced chemokine concentrations (chemokine (C-X-C) motif ligand (CXCL-1), CCL5) whereas minocycline had broader effects, (reducing CXCL-1, tumor necrosis factor (TNFα), IFNγ, interleukin (IL) 2, IL-10 and IL-17A). Brain inflammatory mediator levels were elevated in adult rats that had DKA as juveniles, compared with adult diabetic rats without previous DKA, however, neither TRAM-34 nor minocycline treatment reduced these levels.

CONCLUSIONS

These data demonstrate that both TRAM-34 and minocycline reduce acute neuroinflammation during DKA, however, treatment with these agents for 1 week after DKA does not reduce long-term neuroinflammation.

SPARC Aggravates Blood-Brain Barrier Disruption via Integrin αVβ3/MAPKs/MMP-9 Signaling Pathway after Subarachnoid Hemorrhage

Blood-brain barrier (BBB) disruption is a common and critical pathology following subarachnoid hemorrhage (SAH). We investigated the BBB disruption property of secreted protein acidic and rich in cysteine (SPARC) after SAH. A total of 197 rats underwent endovascular perforation to induce SAH or sham operation. Small interfering ribonucleic acid (siRNA) for SPARC or scrambled siRNA was administered intracerebroventricularly to rats 48 h before SAH. Anti-SPARC monoclonal antibody (mAb) 236 for functional blocking or normal mouse immunoglobulin G (IgG) was administered intracerebroventricularly 1 h after SAH. Selective integrin αVβ3 inhibitor cyclo(-RGDfK) or phosphate-buffered saline was administered intranasally 1 h before SAH, along with recombinant SPARC treatment. Neurobehavior, SAH severity, brain edema, immunohistochemical staining, and Western blot were evaluated. The expression of SPARC and integrin αVβ3 was upregulated after SAH in the endothelial cells. SPARC siRNA and anti-SPARC mAb 236 prevented neuroimpairments and brain edema through protection of BBB as measured by IgG extravasation 24 and 72 h after SAH. Recombinant SPARC aggravated neuroimpairments and cyclo(-RGDfK) suppressed the harmful neurological effects via inhibition of activated c-Jun N-terminal kinase, p38, and matrix metalloproteinase-9 followed by retention of endothelial junction proteins. SPARC may induce post-SAH BBB disruption via integrin αVβ3 signaling pathway.

Intra-arterial Contrast-enhanced Micro-computed Tomography Can Evaluate Intracranial Status in the Ultra-early Phase of Experimental Subarachnoid Hemorrhage in Rats

The endovascular perforation (EP) model is a common technique for experimental subarachnoid hemorrhage (SAH) in rats, simulating the pathophysiological features observed in the acute phase of SAH. Due to the drawbacks of large variations in the amount of bleeding, the results obtained from this model require severity evaluation. However, no less-invasive procedure could confirm the precise intracranial conditions immediately after establishing the rat EP model. We created a novel method for evaluating SAH immediately after establishing the rat EP model using intra-arterial contrast-enhanced micro-computed tomography (CT). We administered contrast agents continuously via the carotid artery during surgery and performed CT examination immediately after SAH induction. First, bleeding severity was classified by establishing a scoring system based on the CT findings (cSAH scoring system). Subsequently, we determined the actual SAH distribution macroscopically and histologically and compared it with the cSAH scores. Second, we investigated the contrast agent’s neurotoxicity in rats. Finally, we confirmed the correlation between cSAH scores and SAH severity, including neurological status, cerebral vasospasm, and hematoma volume 24 hr after SAH. Intra-arterial contrast-enhanced micro-CT could visualize the distribution of SAH proportionally to the bleeding severity immediately after establishing the EP model. Moreover, the contrast agent administration was determined not to be neurotoxic to rats. The cSAH scoring revealed a significant correlation with the SAH severity in the rat EP model (P <0.01). Thus, our minimally invasive method provided precise information on intracranial status in the ultra-early phase of SAH in rats EP model.

T0901317, an Agonist of Liver X Receptors, Attenuates Neuronal Apoptosis in Early Brain Injury after Subarachnoid Hemorrhage in Rats via Liver X Receptors/Interferon Regulatory Factor/P53 Upregulated Modulator of Apoptosis/Dynamin-1-Like Protein Pathway

Methods

Subarachnoid hemorrhage (SAH) models of Sprague-Dawley rats were established with perforation method. T0901317 was injected intraperitoneally 1-hour post-SAH. GSK2033, an inhibitor of LXRs, and interferon regulatory factor (IRF-1) CRISPR activation were injected intracerebroventricularly to evaluate potential signaling pathway. The severity of SAH, neurobehavior test in both short- and long-term and apoptosis was measured with Western blot and immunofluorescence staining.

Results

Expression of LXR-α and IRF-1 increased and peaked at 24 h post-SAH, while LXR-β remained unaffected in SAH+vehicle group compared with Sham group. Post-SAH T0901317 treatment attenuated neuronal impairments in both short- and long-term and decreased neuronal apoptosis, the expression of IRF-1, P53 upregulated modulator of apoptosis (PUMA), dynamin-1-like protein (Drp1), Bcl-2-associated X protein (Bax) and cleaved caspase-3, and increasing B-cell lymphoma 2 (Bcl-2) at 24 h from modeling. GSK2033 inhibited LXRs and reversed T0901317's neuroprotective effects. IRF-1 CRISPR activation upregulated the expression of IRF-1 and abolished the treatment effects of T0901317.

Conclusion

T0901317 attenuated neuronal apoptosis via LXRs/IRF-1/PUMA/Drp1 pathway in SAH rats.

Blockade of Motor Cortical Long-Term Potentiation Induction by Glutamatergic Dysfunction Causes Abnormal Neurobehavior in an Experimental Subarachnoid Hemorrhage Model

Subarachnoid hemorrhage (SAH) is a life-threatening condition that can also lead to permanent paralysis. However, the mechanisms that underlying neurobehavioral deficits after SAH have not been fully elucidated. As theta burst stimulation (TBS) can induce long-term potentiation (LTP) in the motor cortex, we tested its potential as a functional evaluation tool after experimentally induced SAH. Motor cortical inter-neuronal excitability was evaluated in anesthetized rats after 200 Hz-quadripulse TBS (QTS5), 200 Hz-quadripulse stimulation (QPS5), and 400 Hz-octapulse stimulation (OPS2.5). Furthermore, correlation between motor cortical LTP and N-methyl-D-aspartate-receptor activation was evaluated using MK-801, a NMDA-receptor antagonist. We evaluated inhibition-facilitation configurations [interstimulus interval: 3 ms; short-latency intracortical inhibition (SICI) and 11 ms; intracortical facilitation (ICF)] with paired electrical stimulation protocols and the effect of TBS paradigm on continuous recording of motor-evoked potentials (MEPs) for quantitative parameters. SAH and MK-801 completely blocked ICF, while SICI was preserved. QTS5, QPS5, and OPS2.5 facilitated continuous MEPs, persisting for 180 min. Both SAH and MK-801 completely blocked MEP facilitations after QPS5 and OPS2.5, while MEP facilitations after QTS5 were preserved. Significant correlations were found among neurological scores and 3 ms-SICI rates, 11 ms-ICF rates, and MEP facilitation rates after 200 Hz-QTS5, 7 days after SAH (R² = 0.6236; r = −0.79, R² = 0.6053; r = −0.77 and R² = 0.9071; r = 0.95, p < 0.05, respectively). Although these findings need to be verified in humans, our study demonstrates that the neurophysiological parameters 3 ms-SICI, 11 ms-ICF, and 200 Hz-QTS5-MEPs may be useful surrogate quantitative biomarkers for assessing inter-neuronal function after SAH.

Gene expression profiling of brain endothelial cells after experimental subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) is a type of hemorrhagic stroke that is associated with high morbidity and mortality. New effective treatments are needed to improve outcomes. The pathophysiology of SAH is complex and includes early brain injury and delayed cerebral ischemia, both of which are characterized by blood–brain barrier (BBB) impairment. We isolated brain endothelial cells (BECs) from mice subjected to SAH by injection of blood into the prechiasmatic cistern. We used gene expression profiling to identify 707 unique genes (2.8% of transcripts, 403 upregulated, 304 downregulated, 24,865 interrogated probe sets) that were significantly differentially expressed in mouse BECs after SAH. The pathway involving prostaglandin synthesis and regulation was significantly upregulated after SAH, including increased expression of the Ptgs2 gene and its corresponding COX-2 protein. Celecoxib, a selective COX-2 inhibitor, limited upregulation of Ptgs2 in BECs. In this study, we have defined the gene expression profiling of BECs after experimental SAH and provide further insight into BBB pathophysiology, which may be relevant to other neurological diseases such as traumatic brain injury, brain tumours, ischaemic stroke, multiple sclerosis, and neurodegenerative disorders.

Neuroprotective effect of minocycline against acute brain injury in clinical practice: A systematic review

Acute brain injury is a leading cause of morbidity and mortality worldwide. The term is inclusive of traumatic brain injury, cerebral ischemia, subarachnoid hemorrhage, and intracerebral hemorrhage. Current pharmacologic treatments have had minimal effect on improving neurological outcomes leading to a significant interest in the development neuroprotective agents. Minocycline is a second-generation tetracycline with high blood brain barrier penetrance due to its lipophilic properties. It functions across multiple molecular pathways involved in secondary-injury cascades following acute brain injury. Animal model studies suggest that minocycline might lead to improved neurologic outcomes, but few such trials exist in humans. Clinical investigations have been limited to small randomized trials in ischemic stroke patients which have not demonstrated a clear advantage in neurologic outcomes, but also have not been sufficiently powered to draw definitive conclusions. The potential neuroprotective effect of minocycline in the setting of traumatic brain injury, subarachnoid hemorrhage, and intracerebral hemorrhage have all been limited to pilot studies with phase II/III investigations pending. The authors aim to synthesize what is currently known about minocycline as a neuroprotective agent against acute brain injury in humans.

Mdivi-1 alleviates brain damage and synaptic dysfunction after intracerebral hemorrhage in mice

As a selective inhibitor of mitochondrial fission protein dynamin-related protein-1 (Drp1), mitochondrial division inhibitor 1 (mdivi-1) can cross the blood-brain barrier (BBB) and exert neuroprotection. However, it remains unclear whether mdivi-1 can attenuate intracerebral hemorrhage (ICH)-induced secondary brain injury. This study was undertaken to characterize the roles of mdivi-1 in short-term and long-term behavioral outcomes, along with synaptic plasticity changes in mice after ICH. The results indicated mdivi-1 reversed Drp1 translocation and the morphologic changes of mitochondria, as well as ameliorated short-term neurobehavioral deficits, the BBB disruption and brain edema remarkably. In addition, mdivi-1 could rescue ICH-induced motor and memory dysfunctions. Mdivi-1 could also prevent ICH-induced reductions in synaptic proteins (synapsin I, PSD95) and phosphorylated cAMP-response element binding (p-CREB). In vitro, mdivi-1 inhibited hemin-induced hippocampal neuron death and improved neurite outgrowth. In conclusion, we found that mdivi-1 can alleviate short-term and long-term neurological deficits, synaptic dysfunction. These findings demonstrate that mdivi-1 may be beneficial in the treatment of secondary brain injury, synaptic dysfunction and neurological outcomes caused by ICH.

Effects of 9-t-butyl doxycycline on the innate immune response to CNS ischemia-reperfusion injury

Cerebral ischemia triggers a cascade of neuroinflammatory and peripheral immune responses that contribute to post-ischemic reperfusion injury. Prior work conducted in CNS ischemia models underscore the potential to harness non-antibiotic properties of tetracycline antibiotics for therapeutic benefit. In the present study, we explored the immunomodulatory effects of the tetracycline derivative 9-tert-butyl doxycycline (9-TB) in a mouse model of transient global ischemia that mimics immunologic aspects of the post-cardiac arrest syndrome. Pharmacokinetic studies performed in C57BL/6 mice demonstrate that within four hours after delivery, levels of 9-TB in the brain were 1.6 and 9.5-fold higher than those obtained using minocycline and doxycycline, respectively. Minocycline and 9-TB also dampened inflammation, measured by reduced TNFα-inducible, NF-κβ-dependent luciferase activity in a microglial reporter line. Notably, daily 9-TB treatment following ischemia-reperfusion injury in vivo induced the retention of polymorphonuclear neutrophils (PMNs) within the spleen while simultaneously biasing CNS PMNs towards an anti-inflammatory (CD11b^LowYm1+) phenotype. These studies indicate that aside from exhibiting enhanced CNS delivery, 9-TB alters both the trafficking and polarization of PMNs in the context of CNS ischemia-reperfusion injury.

Behavioral tests in rodent models of stroke

Rodents are the most widely used experimental animals in stroke research due to their similar vascular anatomy, high reproductive rates, and availability of transgenic models. However, the difficulties in assessing higher brain functions, such as cognition and memory, in rodents decrease the translational potential of these studies. In this review, we summarize commonly used motor/sensorimotor and cognition tests in rodent models of stroke. Specifically, we first briefly introduce the objective and procedure of each behavioral test. Next, we summarize the application of each test in both ischemic stroke and hemorrhagic stroke. Last, the advantages and disadvantages of these tests in assessing stroke outcome are discussed. This review summarizes commonly used behavioral tests in stroke studies and compares their applications in different stroke types.

Neurocognitive Outcomes in a Cisternal Blood Injection Murine Model of Subarachnoid Hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) results in neurocognitive dysfunction and anxiety in humans and in animal models. Neurobehavioral tests such as the Morris Water Maze (MWM) and Elevated Plus Maze (EPM) tests are validated in several models of SAH but have not been tested in the murine cisternal blood injection SAH model.

METHODS

Adult C57BL/6 mice (n=16) were randomized into two groups. Group 1 (n=8) received sham surgery. Group 2 (n=8) underwent SAH with 60 µL of autologous blood injected into the cisterna magna. Mice were then tested using the Modified Garcia Score on post-operative day 2 (POD2), EPM on POD5 & POD16, and MWM on POD6-16.Brain tissues harvested on POD16 were stained with Fluoro-Jade C to identify neurodegeneration in the hippocampus and cortex and Iba-1 immunofluorescence staining for microglial activation in the dentate gyrus and CA1 region of the hippocampus.

RESULTS

SAH mice showed increased escape latency on POD10. Swim distance was significantly increased on POD9-10 and swim speed was significantly decreased on POD6&POD10 in SAH mice. SAH mice exhibited a trend for lowered proportion of covered arm entries in EPM on POD16. Modified Garcia Score was not significantly different between the groups on POD2. The area of microglial activation in the dentate gyrus and CA1 region of the hippocampus was mildly increased but not significantly different at day 16 after SAH. Similarly, no significant differences were noted in the number of Fluoro-Jade C (+) cells in cortex or hippocampus.

CONCLUSIONS

Cisternal single blood injection in mice produces mild neurocognitive deficits most pronounced in spatial learning and most evident 10 days after SAH.

Hydrogen gas inhalation improves delayed brain injury by alleviating early brain injury after experimental subarachnoid hemorrhage

Molecular hydrogen (H₂) protect neurons against reactive oxygen species and ameliorates early brain injury (EBI) after subarachnoid hemorrhage (SAH). This study investigated the effect of H₂ on delayed brain injury (DBI) using the rat SAH + unilateral common carotid artery occlusion (UCCAO) model with the endovascular perforation method. 1.3% H₂ gas (1.3% hydrogen premixed with 30% oxygen and balanced nitrogen) inhalation was performed on days 0 and 1, starting from anesthesia induction and continuing for 2 h on day 0, and starting from anesthesia induction and continuing for 30 min on day 1. EBI was assessed on the basis of brain edema, expression of S100 calcium-binding protein B (S100B), and phosphorylation of C-Jun N-terminal kinase on day 2, and neurological deficits on day 3. Reactive astrogliosis and severity of cerebral vasospasm (CV) were assessed on days 3 and 7. DBI was assessed on the basis of neurological deficits and neuronal cell death on day 7. EBI, reactive astrogliosis, and DBI were ameliorated in the H₂ group compared with the control group. CV showed no significant improvement between the control and H₂ groups. This study demonstrated that H₂ gas inhalation ameliorated DBI by reducing EBI without improving CV in the rat SAH + UCCAO model.

Hydrogen Inhalation Attenuates Oxidative Stress Related Endothelial Cells Injury After Subarachnoid Hemorrhage in Rats

Background: Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease with poor clinical outcome. Nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome serves a key role in inflammatory response, which may lead to endothelial cell injury and blood-brain barrier (BBB) disruption. Hydrogen (H₂) is considered a neuroprotective antioxidant. This study was set out to explore whether hydrogen inhalation protects against SAH induced endothelial cell injury, BBB disruption, microthrombosis and vasospasm in rats.

Methods: One hundred eighty-two male SD rats were used for the study. SAH was induced by endovascular perforation. H2 at a concentration of 3.3% was inhaled beginning at 0.5 h after SAH for duration of 30, 60 or 120 min, followed by single administration or once daily administration for 3 days. The temporal expression of NLRP3 and ASC in the brain was determined, with the effect of hydrogen inhalation evaluated. In addition, brain water content, oxidative stress markers, inflammasome, apoptotic markers, microthrombosis, and vasospasm were evaluated at 24 or 72 h after SAH.

Results: The expression of NLRP3 and ASC were upregulated after SAH associated with elevated expression of MDA, 8-OHdG, 4-HNE, HO-1, TLR4/NF-κB, inflammatory and apoptotic makers. Hydrogen inhalation reduced the expression of these inflammatory and apoptotic makers in the vessels, brain edema, microthrombi formation, and vasospasm in rats with SAH relative to control. Hydrogen inhalation also improved short-term and long-term neurological recovery after SAH.

Conclusion: Hydrogen inhalation can ameliorate oxidative stress related endothelial cells injury in the brain and improve neurobehavioral outcomes in rats following SAH. Mechanistically, the above beneficial effects might be related to, at least in part, the inhibition of activation of ROS/NLRP3 axis.

Minocycline Attenuates Experimental Subarachnoid Hemorrhage in Rats

Backgroud

The aim of this study was to evaluate the therapeutic effect of minocycline on treating experimental subarachnoid hemorrhage (SAH) in rats and to explore its possible molecular mechanism.

Methods

SAH was induced in male Sprague-Dawley rats by endovascular perforation. The rats were treated with minocycline (25 mg/kg or 50 mg/kg) or saline at 2 hand 12 h post SAH. Neurological function, cerebral hemorrhage, and edema were scored at 48 h post SAH. Cell death and P2X4 receptor (P2X4R) expression were observed in the prefrontal cortex (PFC).

Results

Treatment with a highdose of minocycline significantly improved the neurological function score, and attenuated cerebral hemorrhage and edema. Low-dose minocycline could reduce hemorrhage, but the effect on neurological deficits and brain edema was not obvious. Minocycline treatment could alleviate neuronal apoptosis in the PFC, which was related to reduced expression of inflammatory cytokines. Immunofluorescence showed that P2X4R on microglia was activated after SAH. Minocycline treatment inhibited P2X4R activation and further suppressed the phosphorylation of downstream p38 MAPK.

Conclusions

Minocycline plays a neuroprotective role by attenuating early brain injury after experimental SAH. The therapeutic mechanism of minocycline may be mediated by the inhibition of P2X4R on microglia.

Osteopontin-Enhanced Autophagy Attenuates Early Brain Injury via FAK-ERK Pathway and Improves Long-Term Outcome after Subarachnoid Hemorrhage in Rats

Osteopontin (OPN) enhances autophagy, reduces apoptosis, and attenuates early brain injury (EBI) after a subarachnoid hemorrhage (SAH). A total of 87 Sprague–Dawley rats were subjected to sham or SAH operations to further investigate the signaling pathway involved in osteopontin-enhanced autophagy during EBI, and the potential effect of recombinant OPN (rOPN) administration to improve long-term outcomes after SAH. Rats were randomly divided into five groups: Sham, SAH + Vehicle (PBS, phosphate-buffered saline), SAH + rOPN (5 μg/rat recombinant OPN), SAH + rOPN + Fib-14 (30 mg/kg of focal adhesion kinase (FAK) inhibitor-14), and SAH + rOPN + DMSO (dimethyl sulfoxide). Short-term and long-term neurobehavior tests were performed, followed by a collection of brain samples for assessment of autophagy markers in neurons, pathway proteins expression, and delayed hippocampal injury. Western blot, double immunofluorescence staining, Nissl staining, and Fluoro-Jade C staining assay were used. Results showed that rOPN administration increased autophagy in neurons and improved neurobehavior in a rat model of SAH. With the administration of FAK inhibitor-14 (Fib-14), neurobehavioral improvement and autophagy enhancement induced by rOPN were abolished, and there were consistent changes in the phosphorylation level of ERK1/2. In addition, early administration of rOPN in rat SAH models improved long-term neurobehavior results, possibly by alleviating hippocampal injury. These results suggest that FAK–ERK signaling may be involved in OPN-enhanced autophagy in the EBI phase after SAH. Early administration of rOPN may be a preventive and therapeutic strategy against delayed brain injury after SAH.

Osteopontin attenuates early brain injury through regulating autophagy-apoptosis interaction after subarachnoid hemorrhage in rats

Aim

To determine the effect of osteopontin (OPN) on autophagy and autophagy‐apoptosis interactions after SAH.

Methods

The endovascular perforation model of SAH or sham surgery was performed in a total of 86 Sprague‐Dawley male rats. The temporal expressions of endogenous OPN and autophagy‐related proteins (Beclin 1, ATG5, LC3 II to I ratio) were measured in sham and SAH rats at different time points (3, 6, 12, 24, and 72 hours). Rats were randomly divided into three groups: Sham, SAH + Vehicle (PBS, phosphate‐buffered saline), and SAH + rOPN (5 μg/rat recombinant OPN). Neurobehavioral tests were performed 24 hours after SAH, followed by the collection of brain samples for assessment of autophagy and apoptosis proteins. These tests assessed whether an autophagy‐apoptosis relationship existed on the histological level in the brain.

Results

Endogenous OPN and autophagy‐related proteins all increased after SAH. rOPN administration improved neurological dysfunction, increased the expression of autophagy‐related proteins (Beclin 1, ATG5, LC3 II to I ratio) and antiapoptotic protein Bcl‐2, while decreasing the expression of proapoptotic proteins (cleaved Caspase‐3 and Bax). rOPN also regulated autophagy‐apoptosis interactions 24 hours after SAH.

Conclusion

rOPN attenuates early brain injury and inhibits neuronal apoptosis by activating autophagy and regulating autophagy‐apoptosis interactions.

Early Antiinflammatory Therapy Attenuates Brain Damage After Sah in Rats

BACKGROUND

Early inflammatory processes may play an important role in the development of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Experimental studies suggest that anti-inflammatory and membrane-stabilizing drugs might have beneficial effects, although the underlying mechanisms are not fully understood. The aim of this study was to investigate the effect of early treatment with methylprednisolone and minocycline on cerebral perfusion and EBI after experimental SAH.

METHODS

Male Sprague-Dawley rats were subjected to SAH using the endovascular filament model. 30 minutes after SAH, they were randomly assigned to receive an intravenous injection of methylprednisolone (16mg/kg body weight, n=10), minocycline (45mg/kg body weight, n=10) or saline (n=11). Mean arterial blood pressure (MABP), intracranial pressure (ICP) and local cerebral blood flow (LCBF) over both hemispheres were recorded continuously for three hours following SAH. Neurological assessment was performed after 24 hours. Hippocampal damage was analyzed by immunohistochemical staining (caspase 3).

RESULTS

Treatment with methylprednisolone or minocycline did not result in a significant improvement of MABP, ICP or LCBF. Animals of both treatment groups showed a non-significant trend to better neurological recovery compared to animals of the control group. Mortality was reduced and hippocampal damage significantly attenuated in both methylprednisolone and minocycline treated animals.

CONCLUSION

The results of this study suggest that inflammatory processes may play an important role in the pathophysiology of EBI after SAH. Early treatment with the anti-inflammatory drugs methylprednisolone or minocycline in the acute phase of SAH has the potential to reduce brain damage and exert a neuroprotective effect.

Mitophagy Reduces Oxidative Stress Via Keap1 (Kelch-Like Epichlorohydrin-Associated Protein 1)/Nrf2 (Nuclear Factor-E2-Related Factor 2)/PHB2 (Prohibitin 2) Pathway After Subarachnoid Hemorrhage in Rats

Background and Purpose- Mitoquinone has been reported as a mitochondria-targeting antioxidant to promote mitophagy in various chronic diseases. Here, our aim was to study the role of mitoquinone in mitophagy activation and oxidative stress-induced neuronal death reduction after subarachnoid hemorrhage (SAH) in rats. Methods- Endovascular perforation was used for SAH model of male Sprague-Dawley rats. Exogenous mitoquinone was injected intraperitoneally 1 hour after SAH. ML385, an inhibitor of Nrf2 (nuclear factor-E2-related factor 2), was given intracerebroventricularly 24 hours before SAH. Small interfering RNA for PHB2 (prohibitin 2) was injected intracerebroventricularly 48 hours before SAH. Nuclear, mitochondrial, and cytoplasmic fractions were gathered using nucleus and mitochondria isolation kits. SAH grade evaluation, short- and long- term neurological function tests, oxidative stress, and apoptosis measurements were performed. Pathway related proteins were investigated with Western blot and immunofluorescence staining. Results- Expression of Keap1 (Kelch-like epichlorohydrin-associated protein 1, 2.84× at 24 hours), Nrf2 (2.78× at 3 hours), and LC3II (light chain 3-II; 1.94× at 24 hours) increased, whereas PHB2 (0.46× at 24 hours) decreased after SAH compared with sham group. Mitoquinone treatment attenuated oxidative stress and neuronal death, both short-term and long-term. Administration of mitoquinone resulted in a decrease in expression of Keap1 (0.33×), Romo1 (reactive oxygen species modulator 1; 0.24×), Bax (B-cell lymphoma-2 associated X protein; 0.31×), Cleaved Caspase-3 (0.29×) and an increase in Nrf2 (2.13×), Bcl-xl (B-cell lymphoma-extra large; 1.67×), PINK1 (phosphatase and tensin-induced kinase 1; 1.67×), Parkin (1.49×), PHB2 (1.60×), and LC3II (1.67×) proteins compared with SAH+vehicle group. ML385 abolished the treatment effects of mitoquinone on behavior and protein levels. PHB2 small interfering RNA reversed the outcomes of mitoquinone administration through reduction in protein expressions downstream of PHB2. Conclusions- Mitoquinone inhibited oxidative stress-related neuronal death by activating mitophagy via Keap1/Nrf2/PHB2 pathway after SAH. Mitoquinone may serve as a potential treatment to relieve brain injury after SAH.

RP001 hydrochloride improves neurological outcome after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) results in neurological damage, acute cardiac damage and has a high mortality rate. Immunoresponse in the acute phase after SAH plays a key role in mediating vasospasm, edema, inflammation and neuronal damage. The S1P/S1PR pathway impacts multiple cellular functions, exerts anti-inflammatory and anti-apoptotic effects, promotes remyelination, and improves outcome in several central nervous system (CNS) diseases. RP001 hydrochloride is a novel S1PR agonist, which sequesters lymphocytes within their secondary tissues and prevents infiltration of immune cells into the CNS thereby reducing immune response. In this study, we investigated whether RP001 attenuates neuronal injury after SAH by reducing inflammation. S1PRs, specifically S1PR_{1, 3} not only exerts anti-inflammatory effects, but also decreases heart rate and induces atrioventricular conduction abnormalities. Therefore, we also tested whether RP001 treatment of SAH regulates cardiac functional outcome. Male adult C57BL/6 mice were subjected to SAH, and neurological function tests, echocardiography, and immunohistochemical analysis were performed. SAH induces neurological deficits and acute cardiac dysfunction compared to sham control mice. Treatment of SAH with a low-dose of RP001 induces better neurological outcome and cardiac function compared to a high-dose of RP001. Low-dose-RP001 treatment significantly decreases apoptosis, white matter damage, blood brain barrier permeability, microglial/astrocyte activation, macrophage chemokine protein-1, matrix metalloproteinase-9 and NADPH oxidase-2 expression in the brain compared to SAH control mice. Our findings indicate that low-dose of RP001 alleviates neurological damage after SAH, in part by decreasing neuroinflammation.

Neurogenesis changes and the fate of progenitor cells after subarachnoid hemorrhage in rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease that leads to poor outcomes. Neurogenesis, an essential recovery mechanism after brain injury, has not been fully elucidated after SAH.

METHODS

A total of 122 SD rats were used in this study. For experiment one, the rats were randomly divided into six groups: sham and SAH with different time points (1,3,5,7,14 days) (n = 12/group). An endovascular perforation method was conducted for SAH model. Rats were injected with 5-Bromo-2'-deoxyuridine (BrdU, 50 mg/kg) 24 h before euthanasia at different time points after SAH. The BrdU labeled cells were detected by immunohistochemistry; Doublecortin (DCX) and glial fibrillary acidic protein (GFAP) were measured by western blot and immunohistochemistry. For experiment two, rats were randomly divided into five groups: sham and SAH with different time points (1, 2, 4, 8 weeks) (n = 6/group). Rats received BrdU (50 mg/kg) once daily for 7 days after the induction of SAH. Double immunofluorescence staining was used to verify proliferation, differentiation and migration of progenitor cells. Rotarod test and water maze used to test the neurobehavioral recovery.

RESULTS

Our results showed that BrdU positive cells in hippocampus changed overtime after SAH. BrdU positive cells decreased as early as 1 day reaching lowest levels at 3 days after SAH, after which it gradually recovered. Similar change patterns were observed with DCX, which was reversed with GFAP. In addition, BrdU did not co-localize with cleaved caspase-3. The BrdU positive cells mainly differentiated into immature neurons for short-term fate, whereas they differentiated into mature neurons for long-term fate but not astrocytes, which facilitated neurobehavioral recovery after SAH.

CONCLUSION

Neurogenesis in the hippocampus changes overtime after SAH. The neuronal progenitor cells may play an essential role in the neurobehavioral recovery after brain injury induced by SAH, since short-term progenitors helped with the recovery of immature neurons in the hippocampus, whereas long-term progenitors differentiated into mature neurons.

Recombinant CTRP9 administration attenuates neuroinflammation via activating adiponectin receptor 1 after intracerebral hemorrhage in mice

Background

Neuroinflammation is a crucial factor contributing to neurological injuries after intracerebral hemorrhage (ICH). C1q/TNF-related protein 9 (CTRP9), an agonist of adiponectin receptor 1 (AdipoR1), has recently been shown to reduce inflammatory responses in systemic diseases. The objective of this study was to investigate the protective role of CTRP9 against neuroinflammation after ICH in a mouse model and to explore the contribution of adenosine monophosphate-activated protein kinase (AMPK)/nuclear factor kappa B (NFκB) pathway in AdipoR1-mediated protection.

Methods

Adult male CD1 mice (n = 218) were randomly assigned to different groups for the study. ICH was induced via intrastriatal injection of bacterial collagenase. Recombinant CTRP9 (rCTRP9) was administered intranasally at 1 h after ICH. To elucidate the underlying mechanism, AdipoR1 small interfering ribonucleic acid (siRNA) and selective phosphorylated AMPK inhibitor Dorsomorphin were administered prior to rCTRP9 treatment. Brain edema, short- and long-term neurobehavior evaluation, blood glucose level, western blot, and immunofluorescence staining were performed.

Results

Endogenous CTRP9 and AdipoR1 expression was increased and peaked at 24 h after ICH. AdipoR1 was expressed by microglia, neurons, and astrocytes. Administration of rCTRP9 reduced brain edema, improved short- and long-term neurological function, enhanced the expression of AdipoR1 and p-AMPK, and decreased the expression of phosphorylated NFκB and inflammatory cytokines after ICH. The protective effects of rCTRP9 were abolished by administration of AdipoR1 siRNA and Dorsomorphin.

Conclusions

Our findings demonstrated that administration of rCTRP9 attenuated neuroinflammation through AdipoR1/AMPK/NFκB signaling pathway after ICH in mice, thereby reducing brain edema and improving neurological function after experimental ICH in mice. Therefore, CTRP9 may provide a potential therapeutic strategy to alleviate neuroinflammation in ICH patients.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1256-8) contains supplementary material, which is available to authorized users.

Inflammatory Events Following Subarachnoid Hemorrhage (SAH)

Acute SAH from a ruptured intracranial aneurysm contributes for 30% of all hemorrhagic strokes. The bleeding itself occurs in the subarachnoid space. Nevertheless, injury to the brain parenchyma occurs as a consequence of the bleeding, directly, via several well-defined mechanisms and pathways, but also indirectly, or secondarily. This secondary brain injury following SAH has a variety of causes and possible mechanisms. Amongst others, inflammatory events have been shown to occur in parallel to, contribute to, or even to initiate programmed cell death (PCD) within the central nervous system (CNS) in human and animal studies alike. Mechanisms of secondary brain injury are of utmost interest not only to scientists, but also to clinicians, as they often provide possibilities for translational approaches as well as distinct time windows for tailored treatment options. In this article, we review secondary brain injury due to inflammatory changes, that occur on cellular, as well as on molecular level in the various different compartments of the CNS: the brain vessels, the subarachnoid space, and the brain parenchyma itself and hypothesize about possible signaling mechanisms between these compartments.

The Role of Inflammatory Response in Stroke Associated Programmed Cell Death

Stroke represents devastating pathology which is associated with a high morbidity and mortality. Initial damage caused directly by the onset of stroke, primary injury, may be eclipsed by secondary injury which may have a much more devastating effect on the brain. Primary injury is predominantly associated with necrotic cell death due to fatal insufficiency of oxygen and glucose. Secondary injury may on the contrary, lead apoptotic cell death due to structural damage which is not compatible with cellular functions or which may even represent the danger of malign transformation. The immune system is responsible for surveillance, defense and healing processes and the immune system plays a major role in triggering programmed cell death. Severe pathologies, such as stroke, are often associated with deregulation of the immune system, resulting in aggravation of secondary brain injury. The goal of this article is to overview the current knowledge about the role of immune system in the pathophysiology of stroke with respect to programmed neuronal cell death as well as to discuss current therapeutic strategies targeting inflammation after stroke.

Dihydrolipoic Acid Inhibits Lysosomal Rupture and NLRP3 Through Lysosome-Associated Membrane Protein-1/Calcium/Calmodulin-Dependent Protein Kinase II/TAK1 Pathways After Subarachnoid Hemorrhage in Rat

BACKGROUND AND PURPOSE

The NLRP3 (nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3) inflammasome is a crucial component of the inflammatory response in early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated a role of dihydrolipoic acid (DHLA) in lysosomal rupture, NLRP3 activation, and determined the underlying pathway.

METHODS

SAH was induced by endovascular perforation in male Sprague-Dawley rats. DHLA was administered intraperitoneally 1 hour after SAH. Small interfering RNA for lysosome-associated membrane protein-1 and CaMKIIα (calcium/calmodulin-dependent protein kinase II α) was administered through intracerebroventricular 48 hours before SAH induction. SAH grade evaluation, short- and long-term neurological function testing, Western blot, and immunofluorescence staining experiments were performed.

RESULTS

DHLA treatment increased the expression of lysosome-associated membrane protein-1 and decreased phosphorylated CaMKIIα and NLRP3 inflammasome, thereby alleviating neurological deficits after SAH. Lysosome-associated membrane protein-1 small interfering RNA abolished the neuroprotective effects of DHLA and increased the level of phosphorylated CaMKIIα, p-TAK1 (phosphorylated transforming growth factor-β-activated kinase), p-JNK (phosphorylated c-Jun-N-terminal kinase), and NLRP3 inflammasome. CaMKIIα small interfering RNA downregulated the expression of p-TAK1, p-JNK, and NLRP3 and improved the neurobehavior after SAH.

CONCLUSIONS

DHLA treatment improved neurofunction and alleviated inflammation through the lysosome-associated membrane protein-1/CaMKII/TAK1 pathway in early brain injury after SAH. DHLA may provide a promising treatment to alleviate early brain injury after SAH.

Neurobehavioral testing in subarachnoid hemorrhage: A review of methods and current findings in rodents

The most important aspect of a preclinical study seeking to develop a novel therapy for neurological diseases is whether the therapy produces any clinically relevant functional recovery. For this purpose, neurobehavioral tests are commonly used to evaluate the neuroprotective efficacy of treatments in a wide array of cerebrovascular diseases and neurotrauma. Their use, however, has been limited in experimental subarachnoid hemorrhage studies. After several randomized, double-blinded, controlled clinical trials repeatedly failed to produce a benefit in functional outcome despite some improvement in angiographic vasospasm, more rigorous methods of neurobehavioral testing became critical to provide a more comprehensive evaluation of the functional efficacy of proposed treatments. While several subarachnoid hemorrhage studies have incorporated an array of neurobehavioral assays, a standardized methodology has not been agreed upon. Here, we review neurobehavioral tests for rodents and their potential application to subarachnoid hemorrhage studies. Developing a standardized neurobehavioral testing regimen in rodent studies of subarachnoid hemorrhage would allow for better comparison of results between laboratories and a better prediction of what interventions would produce functional benefits in humans.

Mechanisms of Global Cerebral Edema Formation in Aneurysmal Subarachnoid Hemorrhage

A growing body of clinical literature emphasizes the impact of cerebral edema in early brain injury following aneurysmal subarachnoid hemorrhage (aSAH). Aneurysm rupture itself initiates global cerebral edema in up to two thirds of cases. Although cerebral edema is not a universal feature of aSAH, it portends a poor clinical course, with quantitative analysis revealing a direct correlation between cerebral edema and poor outcome, including mortality and cognitive deficits. Mechanistically, global cerebral edema has been linked to global ischemia at the time of aneurysm rupture, dysfunction of autoregulation, blood breakdown products, neuroinflammation, and hyponatremia/endocrine abnormalities. At a molecular level, several culprits have been identified, including aquaporin-4, matrix metalloproteinase-9, SUR1-TRPM4 cation channels, vascular endothelial growth factor, bradykinin, and others. Here, we review these cellular and molecular mechanisms of global cerebral edema formation in aSAH. Given the importance of edema to the outcome of patients with aSAH and its status as a highly modifiable pathological process, a better understanding of cerebral edema in aSAH promises to hasten the development of medical therapies to improve outcomes in this frequently devastating disease.

Minocycline protects against delayed cerebral ischemia after subarachnoid hemorrhage via matrix metalloproteinase-9 inhibition

Objective

Delayed cerebral ischemia (DCI) is an independent risk factor for poor outcome after aneurysmal subarachnoid hemorrhage (SAH) and is multifactorial in etiology. While prior studies have suggested a role for matrix metalloproteinase-9 (MMP-9) in early brain injury after SAH, its contribution to the pathophysiology of DCI is unclear.

Methods

In the first experiment, wild-type (WT) and MMP-9^-/- mice were subjected to sham or endovascular perforation SAH surgery. In separate experiments, WT and MMP-9^-/-mice were administered vehicle or minocycline either pre- or post-SAH. All mice underwent assessment of multiple components of DCI including vasospasm, neurobehavioral function, and microvessel thrombosis. In another experiment, rabbits were subjected to sham or cisterna magna injection SAH surgery, and administered vehicle or minocycline followed by vasospasm assessment.

Results

MMP-9 expression and activity was increased after SAH. Genetic (MMP-9^-/- mice) and pharmacological (pre-SAH minocycline administration) inhibition of MMP-9 resulted in decreased vasospasm and neurobehavioral deficits. A therapeutically feasible strategy of post-SAH administration of minocycline resulted in attenuation of multiple components of DCI. Minocycline administration to MMP-9^-/- mice did not yield additional protection. Consistent with experiments in mice, both pre- and post-SAH administration of minocycline attenuated SAH-induced vasospasm in rabbits.

Interpretation

MMP-9 is a key player in the pathogenesis of DCI. The consistent attenuation of multiple components of DCI with both pre- and post-SAH administration of minocycline across different species and experimental models of SAH, combined with the excellent safety profile of minocycline in humans suggest that a clinical trial in SAH patients is warranted.

Exendin-4 attenuates neuronal death via GLP-1R/PI3K/Akt pathway in early brain injury after subarachnoid hemorrhage in rats

Neuronal apoptosis is considered to be a crucial therapeutic target against early brain injury (EBI) after subarachnoid hemorrhage (SAH). Emerging evidence indicates that Exendin-4 (Ex-4), a glucagon-like peptide 1 receptor (GLP-1R) agonist, plays a neuroprotective role in cerebrovascular disease. This study was conducted in order to verify the neuroprotective role of EX-4 in EBI after SAH in rats. The endovascular perforation model of SAH was performed in Sprague-Dawley rats (n = 153). Ex-4 was intraperitoneally injected 1 h after SAH induction in the rats (SAH + Ex-4). To elucidate the underlying molecular mechanism, small interfering ribonucleic acid (siRNA) for GLP-1R and a specific inhibitor of PI3K, LY294002, were injected intracerebroventricularly into SAH + Ex-4 rats before induction of SAH (n = 6 per group). SAH grading evaluation, immunohistochemistry, Western blots, neurobehavioral assessment, and Fluoro-Jade C (FJC) staining experiments were performed. Expression of GLP-1R was significantly increased and mainly expressed in neurons at 24 h after SAH induction. Administration of Ex-4 significantly improved both short- and long-term neurobehavior in SAH + Ex-4 group compared to SAH + Vehicle group after SAH. Ex-4 treatment significantly increased the expression of GLP-1R, PI3K, p-Akt, Bcl-xl, and Bcl-2, while at the same time was found to decrease expression of Bax in the brain. Effects of Ex-4 were reversed by the intervention of GLP-1R siRNA and LY294002 in SAH + Ex-4+GLP-1R siRNA and SAH + Ex-4+LY294002 groups, respectively. In conclusion, the neuroprotective effect of Ex-4 in EBI after SAH was mediated by attenuation of neuronal apoptosis via GLP-1R/PI3K/Akt signaling pathway, therefore EX-4 should be further investigated as a potential therapeutic agent in stroke patients.

Minimal Long-Term Neurobehavioral Impairments after Endovascular Perforation Subarachnoid Hemorrhage in Mice

Cognitive deficits are among the most severe and pervasive consequences of aneurysmal subarachnoid hemorrhage (SAH). A critical step in developing therapies targeting such outcomes is the characterization of experimentally-tractable pre-clinical models that exhibit multi-domain neurobehavioral deficits similar to those afflicting humans. We therefore searched for neurobehavioral abnormalities following endovascular perforation induction of SAH in mice, a heavily-utilized model. We instituted a functional screen to manage variability in injury severity, then assessed acute functional deficits, as well as activity, anxiety-related behavior, learning and memory, socialization, and depressive-like behavior at sub-acute and chronic time points (up to 1 month post-injury). Animals in which SAH was induced exhibited reduced acute functional capacity and reduced general activity to 1 month post-injury. Tests of anxiety-related behavior including central area time in the elevated plus maze and thigmotaxis in the open field test revealed increased anxiety-like behavior at subacute and chronic time-points, respectively. Effect sizes for subacute and chronic neurobehavioral endpoints in other domains, however, were small. In combination with persistent variability, this led to non-significant effects of injury on all remaining neurobehavioral outcomes. These results suggest that, with the exception of anxiety-related behavior, alternate mouse models are required to effectively analyze cognitive outcomes after SAH.

Prostaglandin E2 EP4 Receptor Activation Attenuates Neuroinflammation and Early Brain Injury Induced by Subarachnoid Hemorrhage in Rats

Activation of E prostanoid 4 receptor (EP4) shows neuroprotective effects in multiple central nervous system (CNS) lesions, but the roles of EP4 receptor in subarachnoid hemorrhage (SAH) are not explored. This study was designed to research the effects of EP4 modulation on early brain injury (EBI) after experimental SAH in rats. We found that the administration of EP4 selective agonist AE1-329 significantly improved neurological dysfunction, blood brain barrier (BBB) damage and brain edema at 24 h after SAH. Furthermore, AE1-329 obviously reduced the number of activated microglia and the mRNA and protein levels of pro-inflammatory cytokines, and increased Ser1177 phosphorylated endothelial nitric oxide synthase (Ser1177 p-eNOS). Moreover, AE1-329 significantly reduced the number of TUNEL-positive cells and active caspase-3 in cortex after SAH. The EP4 selective antagonist AE3-208 was also administrated and the opposite effects were achieved. Our results indicate that activation of EP4 protects brain from EBI through downregulating neuroinflammation reaction after SAH.

Neuroprotective Effects of Hydrogen Sulfide Against Early Brain Injury and Secondary Cognitive Deficits Following Subarachnoid Hemorrhage

Although the neuroprotective effects of hydrogen sulfide (H₂ S) have been demonstrated in several studies, whether H₂ S protects against early brain injury (EBI) and secondary cognitive dysfunction in subarachnoid hemorrhage (SAH) model remains unknown. This study was undertaken to evaluate the influence of H₂ S on both acute brain injury and neurobehavioral changes as well as the underlying mechanisms after SAH. The H₂ S donor, NaHS, was administered via an intraperitoneal injection at a dose of 5.6 mg/kg at 2 h, 6 h, 24 h, and 46 h after SAH in rat model. The results showed that NaHS treatment significantly improved brain edema and neurobehavioral function, and attenuated neuronal cell death in the prefrontal cortex, associated with a decrease in Bax/Bcl-2 ratio and suppression of caspase-3 activation at 48 h after SAH. NaHS also promoted phospho-Akt and phospho-ERK levels. Furthermore, NaHS treatment significantly enhanced the levels of brain-derived neurotrophic factor (BDNF) and phospho-CREB. Importantly, NaHS administration improved learning and memory performance in the Morris water maze test at 7 days post-SAH in rats. These results demonstrated that NaHS, as an exogenous H₂ S donor, could significantly alleviate the development of EBI and cognitive dysfunction induced by SAH via Akt/ERK-related antiapoptosis pathway, and upregulating BDNF-CREB expression.

Lipoxin A4 Reduces Inflammation Through Formyl Peptide Receptor 2/p38 MAPK Signaling Pathway in Subarachnoid Hemorrhage Rats

BACKGROUND AND PURPOSE

Lipoxin A4 (LXA4) has been reported to reduce inflammation in several neurological injury models. We studied the effects of LXA4 on neuroinflammation after subarachnoid hemorrhage (SAH) in a rat model.

METHODS

Two hundred and thirty-eight Sprague-Dawley male rats, weight 280-320 g, were used. Exogenous LXA4 (0.3 and 1.0 nmol) were injected intracerebroventricularly at 1.5 hours after SAH. Neurological scores, brain water content, and blood-brain barrier were evaluated at 24 hours after SAH; Morris water maze and T-maze tests were examined at 21 days after SAH. The expression of endogenous LXA4 and its receptor formyl peptide receptor 2 (FPR2), as well as p38, interleukin-1β, and interleukin-6 were studied either by ELISA or by Western blots. Neutrophil infiltration was observed by myeloperoxidase staining. FPR2 siRNA was used to knock down LXA4 receptor.

RESULTS

The expression of endogenous LXA4 decreased, and the expression of FPR2 increased after SAH. Exogenous LXA4 decreased brain water content, reduced Evans blue extravasation, and improved neurological functions and improved the learning and memory ability after SAH. LXA4 reduced neutrophil infiltration and phosphorylation of p38, interleukin-1β, and interleukin-6. These effects of LXA4 were abolished by FPR2 siRNA.

CONCLUSIONS

Exogenous LXA4 inhibited inflammation by activating FPR2 and inhibiting p38 after SAH. LXA4 may serve as an alternative treatment to relieve early brain injury after SAH.

Brain Volume Determination in Subarachnoid Hemorrhage Using Rats

Brain edema is routinely measured using the wet-dry method. Volume, however, is the sum total of all cerebral tissues, including water. Therefore, volumetric change following injury may not be adequately quantified using percentage of edema. We thus tested the hypothesis that dried brains can be reconstituted with water and then re-measured to determine the actual volume. Subarachnoid hemorrhage (SAH) was induced by endovascular perforation in adult male Sprague-Dawley rats (n = 30). Animals were euthanized at 24 and 72 h after evaluation of neurobehavior for determination of brain water content. Dried brains were thereafter reconstituted with equal parts of water (lost from brain edema) and centrifuged to remove air bubbles. The total volume was quantified using hydrostatic (underwater) physics principles that 1 ml water (mass) = 1 cm(3) (volume). The amount of additional water needed to reach a preset level marked on 2-ml test tubes was added to that lost from brain edema, and from the brain itself, to determine the final volume. SAH significantly increased both brain water and volume while worsening neurological function in affected rats. Volumetric measurements demonstrated significant brain swelling after SAH, in addition to the brain edema approach. This modification of the "wet-dry" method permits brain volume determination using valuable post hoc dried brain tissue.

The role of rhynchophylline in alleviating early brain injury following subarachnoid hemorrhage in rats

Rhynchophylline (Rhy) has been demonstrated protective effects on some neurological diseases. However, the roles of Rhy in the subarachnoid hemorrhage (SAH) are still to be cleared. In the present study, the effects of Rhy on attenuation of early brain injury (EBI) after SAH have been evaluated. The adult male Sprague-Dawley rats (280-300g) were used to establish the SAH models using endovascular perforation method. Rhy was administered by intraperitoneal injection immediately following SAH. Brain edema was assessed by magnetic resonance imaging (MRI) at 24h after SAH. Neurological deficits, brain water content, malondialdehyde (MDA) concentration, myeloperoxidase (MPO) activity and reactive oxygen species (ROS) content in hippocampus were also evaluated. Immunofluorescence and western blot were used to explore the underlying protective mechanism of Rhy. The results showed that, following 10mg/kg Rhy treatment, the brain edema and neurological deficits, and blood-brain barrier (BBB) disruption were significantly attenuated at 24h after SAH. Additionally, in hippocampus, MDA concentration, MPO activity and ROS content were markedly decreased. Meanwhile, the levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase (NQO-1) were increased, while the expressions of p-p53, cleaved-caspase-3 and tumor necrosis factor-α (TNF-α) were significantly decreased. Our results indicated that Rhy could attenuate early brain injury by reducing inflammation and apoptosis in hippocampus after SAH.

ASK1 is involved in cognitive impairment caused by long-term high-fat diet feeding in mice

Although high-fat diet intake is known to cause obesity and diabetes, the effect of high-fat diet itself on cognitive function remains to be clarified. We have previously shown that apoptosis signal-regulating kinase 1 (ASK1) is responsible for cognitive impairment caused by chronic cerebral hypoperfusion. The present work, by using ASK1 deficient mice, was undertaken to explore the influence of chronic high-fat diet intake on cognitive function and the role of ASK1. Cognitive function in wild-type mice fed high-fat diet from 2 to 24 months of age was significantly impaired compared to those fed control diet, which was associated with the significant white matter lesions, reduction of hippocampal capillary density, and decrement of hippocampal neuronal cell. However, ASK1 deficiency abolished the development of cognitive impairment and cerebral injury caused by high-fat diet. Our results provided the evidence that high-fat diet itself causes cognitive impairment and ASK1 participates in such cognitive impairment.

Valproic Acid treatment after experimental subarachnoid hemorrhage

INTRODUCTION

Subarachnoid hemorrhage (SAH) can result in significant brain injury. Valproic acid (VPA), a widely-used anti-epileptic drug, was investigated as a possible neuroprotective drug in a prechiasmatic injection model of SAH in mice.

METHODS

Mice were randomized to the following experimental groups: SAH, SAH + VPA, Sham, and Sham + VPA. VPA (400 mg/kg) or saline was administered within 30 min of SAH induction and every 12 h thereafter for 48 h. Neurobehavioral assessments using the modified Garcia Score were conducted at 24 and 48 h. Brain injury was assessed at 48 h with fluoro-jade b and caspase-3/NeuN histo- and immunohistochemistry. Vasospasm was assessed in the MCA branches using hematoxylin & eosin histology.

RESULTS

SAH mice treated with VPA appeared to have improved neurobehavioral assessments at both 24 and 48 h compared to untreated SAH mice. VPA treatment in SAH mice also significantly decreased the number of degenerating neurons on fluoro-jade b staining. In VPA-treated SAH mice, there was a trend toward a decrease in the number of apoptotic neurons on caspase-3/NeuN immunohistochemistry. VPA did not significantly affect vasospasm.

CONCLUSION

This study demonstrated that VPA improves neurological outcome and decreases brain injury in a mouse model of SAH.

Early brain injury after aneurysmal subarachnoid hemorrhage: a multimodal neuromonitoring study

Introduction

There is a substantial amount of evidence from animal models that early brain injury (EBI) may play an important role for secondary brain injury after aneurysmal subarachnoid hemorrhage (aSAH). Cerebral microdialysis (CMD) allows online measurement of brain metabolites, including the pro-inflammatory cytokine interleukin-6 (IL-6) and matrix metalloproteinase-9 (MMP-9), which is indicative for disruption of the blood-brain barrier.

Methods

Twenty-six consecutive poor-grade aSAH patients with multimodal neuromonitoring were analyzed for brain hemodynamic and metabolic changes, including CMD-IL-6 and CMD-MMP-9 levels. Statistical analysis was performed by using a generalized estimating equation with an autoregressive function.

Results

The baseline cerebral metabolic profile revealed brain metabolic distress and an excitatory response which improved over the following 5 days (P <0.001). Brain tissue hypoxia (brain tissue oxygen tension of less than 20 mm Hg) was common (more than 60% of patients) in the first 24 hours of neuromonitoring and improved thereafter (P <0.05). Baseline CMD-IL-6 and CMD-MMP-9 levels were elevated in all patients (median = 4,059 pg/mL, interquartile range (IQR) = 1,316 to 12,456 pg/mL and median = 851 pg/mL, IQR = 98 to 25,860 pg/mL) and significantly decreased over days (P <0.05). A higher pro-inflammatory response was associated with the development of delayed cerebral ischemia (P = 0.04), whereas admission disease severity and early brain tissue hypoxia were associated with higher CMD-MMP-9 levels (P <0.03). Brain metabolic distress and increased IL-6 levels were associated with poor functional outcome (modified Rankin Scale of more than 3, P ≤0.01). All models were adjusted for probe location, aneurysm securing procedure, and disease severity as appropriate.

Conclusions

Multimodal neuromonitoring techniques allow insight into pathophysiologic changes in the early phase after aSAH. The results may be used as endpoints for future interventions targeting EBI in poor-grade aSAH patients.