Methylene Blue Ameliorates Ischemia/Reperfusion-Induced Cerebral Edema: An MRI and Transmission Electron Microscope Study

Methylene blue and its potential in the treatment of traumatic brain injury, brain ischemia, and Alzheimer's disease

Traumatic brain injury (TBI) and brain ischemia/reperfusion cause neurodegenerative processes that can continue after the acute stage with the development of severe brain atrophy with dementia. In this case, the long-term neurodegeneration of the brain is similar to the neurodegeneration characteristic of Alzheimer's disease (AD) and is associated with the accumulation of beta amyloid and tau protein. In the pathogenesis of AD as well as in the pathogenesis of cerebral ischemia and TBI oxidative stress, progressive inflammation, glial activation, blood-brain barrier dysfunction, and excessive activation of autophagy are involved, which implies the presence of many targets that can be affected by neuroprotectors. That is, multivariate cascades of nerve tissue damage represent many potential targets for therapeutic interventions. One of such substances that can be used in multi-purpose therapeutic strategies is methylene blue (MB). This drug can have an antiapoptotic and anti-inflammatory effect, activate autophagy, inhibit the aggregation of proteins with an irregular shape, inhibit NO synthase, and bypass impaired electron transfer in the respiratory chain of mitochondria. MB is a well-described treatment for methemoglobinemia, malaria, and encephalopathy caused by ifosfamide. In recent years, this drug has attracted great interest as a potential treatment for a number of neurodegenerative disorders, including the effects of TBI, ischemia, and AD.

Inhalation of Atmospheric-Pressure Gas Plasma Attenuates Brain Infarction in Rats With Experimental Ischemic Stroke

Previous studies suggest the potential efficacy of neuroprotective effects of gaseous atmospheric-pressure plasma (APP) treatment on neuronal cells. However, it remains unclear if the neuroprotective properties of the gas plasmas benefit the ischemic stroke treatment, and how to use the plasmas in the in vivo ischemic stroke models. Rats were subjected to 90 min middle cerebral artery occlusion (MCAO) to establish the ischemic stroke model and then intermittently inhaled the plasma for 2 min at 60 min MCAO. The regional cerebral blood flow (CBF) was monitored. Animal behavior scoring, magnetic resonance imaging (MRI), 2,3,5-triphenyltetrazolium chloride (TTC) staining, and hematoxylin and eosin (HE) staining were performed to evaluate the therapeutic efficacy of the gas plasma inhalation on MCAO rats. Intermittent gas plasma inhalation by rats with experimental ischemic stroke could improve neurological function, increase regional CBF, and decrease brain infarction. Further MRI tests showed that the gas plasma inhalation could limit the ischemic lesion progression, which was beneficial to improve the outcomes of the MCAO rats. Post-stroke treatment with intermittent gas plasma inhalation could reduce the ischemic lesion progression and decrease cerebral infarction volume, which might provide a new promising strategy for ischemic stroke treatment.

Pseudoginsenoside-F11 ameliorates thromboembolic stroke injury in rats by reducing thromboinflammation

Pseudoginsenoside-F11 (PF11), an ocotillol-type ginsenoside, has been reported to exert neuroprotective effects on ischemic stroke induced by permanent and transient middle cerebral artery occlusion in experimental animals. The aim of the present study was to investigate the effect of PF11 on thromboembolic stroke in rats and its possible mechanisms on thromboinflammation. PF11 (4, 12, 36 mg/kg) was injected intravenously (i.v.) once a day for 3 consecutive days to male Wistar rats followed by embolic middle cerebral artery occlusion (eMCAO). The results showed that PF11 significantly reduced the cerebral infarction volume, brain edema and neurological deficits induced by eMCAO. Meanwhile, the thromboinflammation in the ischemic hemisphere was observed at 24 h after eMCAO, as indicated by the increased number of microvascular thrombus and inflammatory response. Moreover, eMCAO resulted in the up-regulation of platelet glycoprotein Ibα (GPIbα) and VI (GPVI), as well as the activation of contact-kinin pathway. Notably, PF11 significantly reversed all these changes. Furthermore, PF11 prevented the eMCAO-induced loss of tight junction proteins and up-regulation of matrix metalloproteinase-9 (MMP-9), thus leading to the alleviation of blood-brain barrier (BBB) damage. In conclusion, the present study revealed that thromboinflammation was induced in the ischemic hemisphere of rats after eMCAO and PF11 exerted marked protective effects against thromboembolic stroke by attenuating thromboinflammation and preventing BBB damage. This research further identifies the potential therapeutic role of PF11 for ischemic stroke.

Methylene blue ameliorates brain edema in rats with experimental ischemic stroke via inhibiting aquaporin 4 expression

Brain edema is a common and serious complication of ischemic stroke with limited effective treatment. We previously reported that methylene blue (MB) attenuated ischemic brain edema in rats, but the underlying mechanisms remained unknown. Aquaporin 4 (AQP4) in astrocytes plays a key role in brain edema. We also found that extracellular signal-regulated kinase 1/2 (ERK1/2) activation was involved in the regulation of AQP4 expression in astrocytes. In the present study, we investigated whether AQP4 and ERK1/2 were involved in the protective effect of MB against cerebral edema. Rats were subjected to transient middle cerebral artery occlusion (tMCAO), MB (3 mg/kg, for 30 min) was infused intravenously through the tail vein started immediately after reperfusion and again at 3 h after ischemia (1.5 mg/kg, for 15 min). Brain edema was determined by MRI at 0.5, 2.5, and 48 h after tMCAO. The decreases of apparent diffusion coefficient (ADC) values on diffusion-weighted MRI indicated cytotoxic brain edema, whereas the increase of T2 MRI values reflected vasogenic brain edema. We found that MB infusion significantly ameliorated cytotoxic brain edema at 2.5 and 48 h after tMCAO and decreased vasogenic brain edema at 48 h after tMCAO. In addition, MB infusion blocked the AQP4 increases and ERK1/2 activation in the cerebral cortex in ischemic penumbra at 48 h after tMCAO. In a cell swelling model established in cultured rat astrocyte exposed to glutamate (1 mM), we consistently found that MB (10 μM) attenuated cell swelling, AQP4 increases and ERK1/2 activation. Moreover, the ERK1/2 inhibitor U0126 (10 μM) had the similar effects as MB. These results demonstrate that MB improves brain edema and astrocyte swelling, which may be mediated by the inhibition of AQP4 expression via ERK1/2 pathway, suggesting that MB may be a potential choice for the treatment of brain edema.

Mitochondria as a target for neuroprotection: role of methylene blue and photobiomodulation

Mitochondrial dysfunction plays a central role in the formation of neuroinflammation and oxidative stress, which are important factors contributing to the development of brain disease. Ample evidence suggests mitochondria are a promising target for neuroprotection. Recently, methods targeting mitochondria have been considered as potential approaches for treatment of brain disease through the inhibition of inflammation and oxidative injury. This review will discuss two widely studied approaches for the improvement of brain mitochondrial respiration, methylene blue (MB) and photobiomodulation (PBM). MB is a widely studied drug with potential beneficial effects in animal models of brain disease, as well as limited human studies. Similarly, PBM is a non-invasive treatment that promotes energy production and reduces both oxidative stress and inflammation, and has garnered increasing attention in recent years. MB and PBM have similar beneficial effects on mitochondrial function, oxidative damage, inflammation, and subsequent behavioral symptoms. However, the mechanisms underlying the energy enhancing, antioxidant, and anti-inflammatory effects of MB and PBM differ. This review will focus on mitochondrial dysfunction in several different brain diseases and the pathological improvements following MB and PBM treatment.

Lipopolysaccharide worsens the prognosis of experimental cerebral ischemia via interferon gamma-induced protein 10 recruit in the acute stage

BACKGROUND

Infection is an important clinical complication facing stroke-patients and triples the risk of death within 30 days post-stroke via mechanisms which are poorly understood.

AIMS

We tried to explore the mechanisms that inflammation caused by infections aggravated the ischemic brain injury after middle cerebral artery occlusion (MCAO).

METHODS

We used lipopolysaccharide (LPS) as systemic inflammatory stimuli to explore the mechanisms of aggravated ischemic brain injury after Sprague-Dawley male rats subjected to MCAO. Brain damage was evaluated by cerebral blood perfusion, Longa-5 scores, infarct volume and edema degree. Systemic cytokine responses and inflammatory changes in the plasma and brain were analyzed by ELISA kit, RT² Profiler™ PCR array, and quantitative real-time PCR. The differential genes were subjected to Gene Ontology enrichment analysis and protein-protein interaction (PPI) network construction.

RESULTS

Lipopolysaccharide profoundly aggravated the brain damage after 24 h post-MCAO. At the acute stage (ischemia/reperfusion 90 min/3 h), the brain homogenate gene expression of interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β) and Interferon gamma-induced protein 10 (IP-10) was significantly up-regulated and the contents in plasma and brain homogenate were significantly increased in MCAO and MCAO + LPS group. IP-10 was the only gene with significant difference between MCAO and MCAO + LPS group, which was also in an important position with degrees of ≥ 14 in PPI network.

CONCLUSIONS

It was possible that trace LPS aggravated the ischemic brain injury by induction of excessive IP-10 secretion in the acute stage, leading to excessive inflammatory response, which consequently increased the infarct volume and edema degree 24 h post-MCAO.

Bu Yang Huan Wu decoction prevents reperfusion injury following ischemic stroke in rats via inhibition of HIF-1 α, VEGF and promotion β-ENaC expression

ETHNOPHARMACOLOGICAL RELEVANCE

Bu Yang Huan Wu Decoction (BYHW) is a famous traditional Chinese medicine (TCM) formula used in China for the treatment of cerebral ischemic stroke. But the protective effects and underlining mechanisms of BYHW remain unclear.

AIM OF THE STUDY

This study was designed to investigate the protective effects and underlining signaling mechanisms of BYHW on brain tissues in a rat model of cerebral ischemic reperfusion (I/R) injury.

MATERIALS AND METHODS

Liquid chromatography was used to verify the composition of BYHW. The cerebral edema and infarct volume were measured by magnetic resonance imaging (MRI). The morphology and ultrastructure of ischemic penumbra brain tissues were observed by hematoxylin-eosin (HE) and transmission electron microscopy (TEM). The expression levels of HIF-1 α, VEGF and β-ENaC were tested using immunohistochemistry technique, western blot and quantitative PCR analysis, respectively.

RESULTS

Administration of BYHW significantly decreased cerebral edema, rat neurological function scores, reduced brain infarct volume. At the same time, BYHW had protective effect on the blood-brain barrier (BBB), which improved the morphology and ultrastructure of ischemic penumbra brain tissues. BYHW treatment significantly decreased the protein and mRNA levels of HIF-1 α and VEGF compared with the model treatment. In addition, BYHW treatment significantly up-regulated the protein and mRNA levels of β-ENaC.

CONCLUSIONS

BYHW protected against cerebral I/R injury in MCAO rats through inhibiting the activation of the HIF-1 α /VEGF pathway and stabilizing ion channel of β-ENaC in brain, indicating that BYHW shows potential for stroke treatment in acute stage.

From Mitochondrial Function to Neuroprotection-an Emerging Role for Methylene Blue

Methylene blue (MB) is a well-established drug with a long history of use, owing to its diverse range of use and its minimal side effect profile. MB has been used classically for the treatment of malaria, methemoglobinemia, and carbon monoxide poisoning, as well as a histological dye. Its role in the mitochondria, however, has elicited much of its renewed interest in recent years. MB can reroute electrons in the mitochondrial electron transfer chain directly from NADH to cytochrome c, increasing the activity of complex IV and effectively promoting mitochondrial activity while mitigating oxidative stress. In addition to its beneficial effect on mitochondrial protection, MB is also known to have robust effects in mitigating neuroinflammation. Mitochondrial dysfunction has been identified as a seemingly unifying pathological phenomenon across a wide range of neurodegenerative disorders, which thus positions methylene blue as a promising therapeutic. In both in vitro and in vivo studies, MB has shown impressive efficacy in mitigating neurodegeneration and the accompanying behavioral phenotypes in animal models for such conditions as stroke, global cerebral ischemia, Alzheimer's disease, Parkinson's disease, and traumatic brain injury. This review summarizes recent work establishing MB as a promising candidate for neuroprotection, with particular emphasis on the contribution of mitochondrial function to neural health. Furthermore, this review will briefly examine the link between MB, neurogenesis, and improved cognition in respect to age-related cognitive decline.

Methylene Blue Attenuates Lung Injury Induced by Hindlimb Ischemia Reperfusion in Rats

Objective

This study was aimed to investigate the protective effect of methylene blue against lung injury induced by reperfusion of ischemic hindlimb in a rat model.

Methods

Twenty-four healthy adult male Sprague-Dawley rats were equally randomized into three groups: sham (SM) group, ischemia reperfusion (IR) group, and methylene blue (MB) group. Rats in both IR and MB groups were subjected to 4 h of ischemia by clamping the left femoral artery and then followed by 4 h of reperfusion. Treatment with 1% methylene blue (50 mg/kg) was administrated intraperitoneally at 10 min prior to reperfusion in the MB group. After 4 h of reperfusion, malondialdehyde (MDA) level, myeloperoxidase (MPO), and superoxide dismutase (SOD) activities in lung tissue were detected; inflammatory cytokines, including IL-1β and IL-6, were measured in bronchoalveolar lavage fluid (BALF); correspondingly, the morphological changes and water content in both gastrocnemius muscle and lung samples were evaluated.

Results

Hindlimb IR caused remarkable morphological abnormalities and edema in both muscle and lung tissues. SOD activity was decreased, both the MPO activity and MDA level in lung tissue, as well as IL-1β and IL-6 levels in BALF, were increased in the IR group (p < 0.05). Compared with the IR group, SOD activity was increased, whereas MPO activity and MDA level in lung tissue and IL-1β and IL-6 levels in BALF were decreased in the MB group (p < 0.05). Also, the histological damage and edema in both lung and muscle tissues were significantly attenuated by the treatment of methylene blue.

Conclusion

Methylene blue attenuates lung injury induced by hindlimb IR in rats, at least in part, by inhibiting oxidative stress.

Aquaporin 4-Mediated Glutamate-Induced Astrocyte Swelling Is Partially Mediated through Metabotropic Glutamate Receptor 5 Activation

Astrocytes are one of the most abundant cell types in the mammalian central nervous system (CNS), and astrocyte swelling is the primary event associated with brain edema. Glutamate, the principal excitatory amino acid neurotransmitter in the CNS, is released at high levels after brain injury including cerebral ischemia. This leads to astrocyte swelling, which we previously demonstrated is related to metabotropic glutamate receptor (mGluR) activation. Aquaporin 4 (AQP4), the predominant water channel in the brain, is expressed in astrocyte endfeet and plays an important role in brain edema following ischemia. Studies recently showed that mGluR5 is also expressed on astrocytes. Therefore, it is worth investigating whether AQP4 mediates the glutamate-induced swelling of astrocytes via mGluR5. In the present study, we found that 1 mM glutamate induced astrocyte swelling, quantified by the cell perimeter, but it had no effect on astrocyte viability measured by the cell counting kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays. Quantitative reverse transcription polymerase chain reaction analyses revealed that AQP4, among AQP1, 4, 5, 9 and 11, was the main molecular expressed in cultured astrocytes. Glutamate-induced cell swelling was accompanied by a concentration-dependent change in AQP4 expression. Furthermore, RNAi technology revealed that AQP4 gene silencing inhibited glutamate-induced astrocyte swelling. Moreover, we found that mGluR5 expression was greatest among the mGluRs in cultured astrocytes and was co-expressed with AQP4. Activation of mGluR5 in cultured astrocytes using (S)-3,5-dihydroxyphenylglycine (DHPG), an mGluR5 agonist, mimicked the effect of glutamate. This effect was abolished by co-incubation with the mGluR5 antagonist fenobam but was not influenced by DL-threo-β-benzyloxyaspartic acid (DL-TBOA), a glutamate transporter inhibitor. Finally, experiments in a rat model of transient middle cerebral artery occlusion (tMCAO) revealed that co-expression of mGluR5 and AQP4 was increased in astrocyte endfeet around capillaries in the penumbra, and this was accompanied by brain edema. Collectively, these results suggest that glutamate induces cell swelling and alters AQP4 expression in astrocytes via mGluR5 activation, which may provide a novel approach for the treatment of edema following brain injury.

Combination Treatment with Methylene Blue and Hypothermia in Global Cerebral Ischemia

Therapeutic hypothermia (TH) is the most potent therapeutic strategy for global cerebral ischemia (GCI), usually induced by cardiac arrest. TH has been shown both to suppress the delayed neuronal cell death in the vulnerable hippocampal CA1 subregion and to improve neurological outcomes in experimental animals after GCI. However, given the multiple adverse effects resulting from TH, application of such a therapy is typically limited. In recent years, methylene blue (MB) has emerged as a potential therapeutic drug for the treatment of neurodegenerative diseases. In this study, we investigated the beneficial effects of mild TH combined with MB treatment after GCI. We report that both the neuronal survival in the hippocampal CA1 region and the hippocampus-dependent spatial learning and memory in the combined treatment animals were enhanced compared to those in the single treatment animals. Mechanistic studies revealed that combined TH and MB treatment significantly attenuated mitochondrial dysfunction induced by GCI in the hippocampus CA1 region. The combined treatment also markedly suppressed GCI-induced reactive gliosis and inflammation and reduced oxidative stress while enhancing the antioxidant capacity of hippocampal CA1 neurons. Finally, combining TH and MB synergistically attenuated the intrinsic cytochrome c/caspase-3 apoptotic pathway induced by GCI. Our results suggest that TH and MB act synergistically to protect the ischemic brain and suppress cognitive impairment caused by GCI.

MRI Dynamically Evaluates the Therapeutic Effect of Recombinant Human MANF on Ischemia/Reperfusion Injury in Rats

As an endoplasmic reticulum (ER) stress-inducible protein, mesencephalic astrocyte-derived neurotrophic factor (MANF) has been proven to protect dopaminergic neurons and nondopaminergic cells. Our previous studies had shown that MANF protected against ischemia/reperfusion injury. Here, we developed a magnetic resonance imaging (MRI) technology to dynamically evaluate the therapeutic effects of MANF on ischemia/reperfusion injury. We established a rat focal ischemic model by using middle cerebral artery occlusion (MCAO). MRI was performed to investigate the dynamics of lesion formation. MANF protein was injected into the right lateral ventricle at 3 h after reperfusion following MCAO for 90 min, when the obvious lesion firstly appeared according to MRI investigation. T2-weighted imaging for evaluating the therapeutic effects of MANF protein was performed in ischemia/reperfusion injury rats on Days 1, 2, 3, 5, and 7 post-reperfusion combined with histology methods. The results indicated that the administration of MANF protein at the early stage after ischemia/reperfusion injury decreased the mortality, improved the neurological function, reduced the cerebral infarct volume, and alleviated the brain tissue injury. The findings collected from MRI are consistent with the morphological and pathological changes, which suggest that MRI is a useful technology for evaluating the therapeutic effects of drugs.

Central Role of Maladapted Astrocytic Plasticity in Ischemic Brain Edema Formation

Brain edema formation and the ensuing brain damages are the major cause of high mortality and long term disability following the occurrence of ischemic stroke. In this process, oxygen and glucose deprivation and the resulting reperfusion injury play primary roles. In response to the ischemic insult, the neurovascular unit experiences both intracellular and extracellular edemas, associated with maladapted astrocytic plasticity. The astrocytic plasticity includes both morphological and functional plasticity. The former involves a reactive gliosis and the subsequent glial retraction. It relates to the capacity of astrocytes to buffer changes in extracellular chemical levels, particularly K⁺ and glutamate, as well as the integrity of the blood-brain barrier (BBB). The latter involves the expression and activity of a series of ion and water transport proteins. These molecules are grouped together around glial fibrillary acidic protein (GFAP) and water channel protein aquaporin 4 (AQP4) to form functional networks, regulate hydromineral balance across cell membranes and maintain the integrity of the BBB. Intense ischemic challenges can disrupt these capacities of astrocytes and result in their maladaptation. The maladapted astrocytic plasticity in ischemic stroke cannot only disrupt the hydromineral homeostasis across astrocyte membrane and the BBB, but also leads to disorders of the whole neurovascular unit. This review focuses on how the maladapted astrocytic plasticity in ischemic stroke plays the central role in the brain edema formation.