Memory facilitation by methylene blue: Dose-dependent effect on behavior and brain oxygen consumption

Deciphering Chemical Rules for Drug Penetration into Strongyloides

Background: Strongyloidiasis, a parasitic infection, presents a significant public health challenge in tropical regions due to the limited repertoire of effective treatments. The screening of chemical libraries against the therapeutically relevant third-stage larvae (L3) of the model parasite Strongyloides venezuelensis yielded meager success rates. This situation is reminiscent of Gram-negative bacteria, where drug entry is a limiting factor. Methods: Here, we set out to determine whether similar barriers are in place and establish whether structural and property requirements exist for anti-strongyloides drug discovery. We focused on dyes as their uptake and effects on viability can be independently assessed in the multicellular parasite, thus providing a means to study the possibility of similar entry rules. We tested different dyes in in vitro assays on L3s. Results: We found that staining was necessary to reduce parasite viability, with some dyes achieving anti-strongyloides effects at concentrations similar to those of the reference drug, ivermectin (IV). Some dyes also showed activity against female adults at concentrations well below that of ivermectin. Unfortunately, the most potent dye, Methylene Blue, was unable to prevent the infection in a preliminary in vivo mouse model assay, presumably due to fast dye clearance. Structural analysis showed that positive charges facilitated the access of the compounds to the L3 tissue, thus providing a structural tool for the introduction of activity. For female adults, low globularity is additionally required. As a proof of concept, we added a positive charge to an inactive compound of one of our chemical libraries and re-determined the activity. Conclusions: These findings allow us to establish structural rules for parasite entry that could be of interest for future drug screening or drug development campaigns. These rules might also be applicable to other related parasites.

Mechanism of Methylene Blue Inducing the Disulfide Bond Formation of Tubulin-Associated Unit Proteins

Methylene blue (MB) has recently completed a Phase-3 clinical trial as leuco-methylthioninium (LMT) bis(hydromethanesulfonate) for treating Alzheimer's disease. Herein, we investigated the mechanism underlying the MB inhibition of tubulin-associated unit (tau) aggregation by focusing on tau monomers. We found that MB causes disulfide bond formation, resulting in strong nuclear magnetic resonance chemical shift perturbations in a large area of tau proteins. The oxidized form of MB, namely methylthioninium (MT+), specifically catalyzed the oxidation of cysteine residues in tau proteins to form disulfide bonds directly using O2. This process is independent of the MT+-to-LMT redox cycle. Moreover, MT+ preferentially oxidized C291 and C322 in the lysine-rich R2 and R3 domains. Under in vivo brain physoxia conditions, LMT may convert to MT+, possibly interfering with tau fibrillation via disulfide bond formation.

The effects of acute Methylene Blue administration on cerebral blood flow and metabolism in humans and rats

Methylene Blue (MB) is a brain-penetrating drug with putative neuroprotective, antioxidant and metabolic enhancing effects. In vitro studies suggest that MB enhances mitochondrial complexes activity. However, no study has directly assessed the metabolic effects of MB in the human brain. We used in vivo neuroimaging to measure the effect of MB on cerebral blood flow (CBF) and brain metabolism in humans and in rats. Two doses of MB (0.5 and 1 mg/kg in humans; 2 and 4 mg/kg in rats; iv) induced reductions in global cerebral blood flow (CBF) in humans (F(1.74, 12.17)5.82, p = 0.02) and rats (F(1,5)26.04, p = 0.0038). Human cerebral metabolic rate of oxygen (CMRO2) was also significantly reduced (F(1.26, 8.84)8.01, p = 0.016), as was the rat cerebral metabolic rate of glucose (CMRglu) (t = 2.6(16) p = 0.018). This was contrary to our hypothesis that MB will increase CBF and energy metrics. Nevertheless, our results were reproducible across species and dose dependent. One possible explanation is that the concentrations used, although clinically relevant, reflect MB's hormetic effects, i.e., higher concentrations produce inhibitory rather than augmentation effects on metabolism. Additionally, here we used healthy volunteers and healthy rats with normal cerebral metabolism where MB's ability to enhance cerebral metabolism might be limited.

Methylene Blue Delivery Mediated by Focused Ultrasound-Induced Blood-Brain Barrier Disruption Reduces Neural Damage and Amyloid-Beta Plaques by AQP-4 Upregulation

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide, causing progressive cognitive decline, memory impairment, and neurological deficits. Methylene blue (MB), an antioxidant, has emerged as a potential drug for the treatment of AD owing to its cognitive improvement and neuroprotective functions. Despite the small molecular size of MB, which can cross the BBB, the therapeutic effective dosage using a BBB-permeable delivery system in a specific brain localization remains unclear. In this study, we presented magnetic resonance-guided focused ultrasound (MRgFUS) as a delivery system to enhance BBB permeability for the effective treatment of AD. MRgFUS using two ultrasound intensities (0.25 and 0.32 MPa) was used to intravenously deliver MB to the hippocampal region. Compared with treatment with 0.25 MPa FUS, treatment with 0.32 MPa FUS significantly enhanced MB brain accumulation. Deposition of amyloid-β (Aβ) plaques and neural cell damage was significantly reduced in 0.32 MPa FUS/MB-treated APP/PS1 mice. Furthermore, aquaporin-4 expression increased significantly in the 0.32 MPa FUS and 0.32 MPa FUS/MB groups without glial fibrillary acidic protein activation. The results from this study demonstrate that FUS improved MB delivery to the brain, and FUS/MB combination treatment reduced the number of Aβ plaques. This study revealed the potential of FUS-BBBD as an effective strategy to enhance the efficacy of therapeutic drugs for AD.

The Potentials of Methylene Blue as an Anti-Aging Drug

Methylene blue (MB), as the first fully man-made medicine, has a wide range of clinical applications. Apart from its well-known applications in surgical staining, malaria, and methemoglobinemia, the anti-oxidative properties of MB recently brought new attention to this century-old drug. Mitochondrial dysfunction has been observed in systematic aging that affects many different tissues, including the brain and skin. This leads to increaseding oxidative stress and results in downstream phenotypes under age-related conditions. MB can bypass Complex I/III activity in mitochondria and diminish oxidative stress to some degree. This review summarizes the recent studies on the applications of MB in treating age-related conditions, including neurodegeneration, memory loss, skin aging, and a premature aging disease, progeria.

Rescuing mitochondria in traumatic brain injury and intracerebral hemorrhages - A potential therapeutic approach

Mitochondria are dynamic organelles responsible for cellular energy production. Besides, regulating energy homeostasis, mitochondria are responsible for calcium homeostasis, signal transmission, and the fate of cellular survival in case of injury and pathologies. Accumulating reports have suggested multiple roles of mitochondria in neuropathologies, neurodegeneration, and immune activation under physiological and pathological conditions. Mitochondrial dysfunction, which occurs at the initial phase of brain injury, involves oxidative stress, inflammation, deficits in mitochondrial bioenergetics, biogenesis, transport, and autophagy. Thus, development of targeted therapeutics to protect mitochondria may improve functional outcomes following traumatic brain injury (TBI) and intracerebral hemorrhages (ICH). In this review, we summarize mitochondrial dysfunction related to TBI and ICH, including the mechanisms involved, and discuss therapeutic approaches with special emphasis on past and current clinical trials.

Pretreatment with Methylene Blue Protects Against Acute Seizure and Oxidative Stress in a Kainic Acid-Induced Status Epilepticus Model

Background

The aim of the present study was to investigate the potential anticonvulsant effect of methylene blue (MB) in a kainic acid (KA)-induced status epilepticus (SE) model. The effects of MB on levels of oxidative stress and glutamate (Glu) also were explored.

Material/Methods

Sixty C57BL/6 mice were randomly divided into 5 equal-sized groups: (1) controls; (2) KA; (3) MB 0.5 mg/kg+KA; (4) MB 1 mg/kg+KA; and (5) vehicle+KA. The SE model was established by intra-amygdala microinjection of KA. Behavioral observations and simultaneous electroencephalographic records of the seizures in different groups were analyzed to determine the potential anticonvulsant effect of MB. The influences of MB on oxidative stress markers and glutamate were also detected to explore the possible mechanism.

Results

MB afforded clear protection against KA-induced acute seizure, as measured by the delayed latency of onset of generalized seizures and SE, decreased percentage of SE, and increased survival rate in mice with acute epilepsy. MB markedly increased the latency to first onset of epileptiform activity and decreased the average duration of epileptiform events, as well as the percentage of time during which the epileptiform activity occurred. Administration of MB prevented KA-induced deterioration of oxidative stress markers and Glu.

Conclusions

MB is protective against acute seizure in SE. This beneficial effect may be at least partially related to its potent antioxidant ability and influence on Glu level.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

Effect of long-term methylene blue treatment on the composition of mouse gut microbiome and its relationship with the cognitive abilities of mice

In recent years, methylene blue (MB) has attracted considerable interest as a potential drug for the treatment of methemoglobinemia and neurodegenerative diseases. MB is active against microorganisms from various taxonomic groups. However, no studies have yet been conducted on the effect of MB on the intestinal microbiome of model animals. The aim of this work was to study the effect of different concentrations of MB on the mouse gut microbiome and its relationship with the cognitive abilities of mice. We showed that a low MB concentration (15 mg/kg/day) did not cause significant changes in the microbiome composition. The Bacteroidetes/Firmicutes ratio decreased relative to the control on the 2nd and 3rd weeks. A slight decrease in the levels Actinobacteria was detected on the 3rd week of the experiment. Changes in the content of Delta, Gamma, and Epsilonproteobacteria have been also observed. We did not find significant alterations in the composition of intestinal microbiome, which could be an indication of the development of dysbiosis or other gut dysfunction. At the same time, a high concentration of MB (50 mg/kg/day) led to pronounced changes, primarily an increase in the levels of Delta, Gamma and Epsilonproteobacteria. Over 4 weeks of therapy, the treatment with high MB concentration has led to an increase in the median content of Proteobacteria to 7.49% vs. 1.61% in the control group. Finally, we found that MB at a concentration of 15 mg/kg/day improved the cognitive abilities of mice, while negative correlation between the content of Deferribacteres and cognitive parameters was revealed. Our data expand the understanding of the relationship between MB, cognitive abilities, and gut microbiome in respect to the antibacterial properties of MB.

Protective effect of methylene blue against copper oxide nanoparticle-induced neurobehavioral toxicity

Increasing attention has been paid in the past decade to assessing the toxicological effects of nanoparticles and finding a protectant; thus, the current study aimed to investigate the protective effect of the mitochondria-targeting drug methylene blue (MB) against copper oxide nanoparticle (CuO-NP)-induced neurobehavioral toxicity in rats. For this purpose, twenty rats were allocated to four equal groups (n = 5). The negative control group received distilled water intraperitoneally (IP) and Tween 80 (10 %) orally. The CuO-NP group was given a dose of 100 mg/kg of CuO-NPs, administered orally, and the positive control group was treated with 1 mg/kg MB intraperitoneally (IP). The final group was concurrently exposed to CuO-NPs and MB for 14 consecutive days. At the end of the study, each group was neurobehaviorally blind tested relative to other experimental animals, then brain tissue markers were determined and a histopathological examination was conducted. The results showed that supplementation with CuO-NPs induced neurobehavioral alterations; increased Cu content in the brain; and enhanced lipid peroxidation (malondialdehyde [MDA]), protein peroxidation (protein carbonyl [PC]), and DNA oxidative damage (8-hydroxy-2-deoxyguanosine [8-OH-dG]) compared to other treatments. In addition, a decrease was noted in the mitochondrial dehydrogenases' (aldehyde dehydrogenase 2 [ALDH2], and glutamate dehydrogenase [GDH]) activity in Cu-exposed rats. The histopathological findings revealed shrunken, pyknotic, and hypereosinophic cortical neurons and increased immune positive brown staining of caspase-3 protein, indicating apoptosis. Co-treatment with methylene blue ameliorated the neurotoxic effects of CuO-NPs; therefore, MB evidently had a powerful modulatory effect against the neurotoxicity of nano-Cu oxide via its antioxidant and mitochondrial protection properties.

Cancer and Alzheimer's disease: intracellular pH scales the metabolic disorders

Alzheimer's disease (AD) and cancer have much in common than previously recognized. These pathologies share common risk factors (inflammation and aging), with similar epidemiological and biochemical features such as impaired mitochondria. Metabolic reprogramming occurs during aging and inflammation. We assume that inflammation is directly responsible of the Warburg effect in cancer cells, with a decreased oxidative phosphorylation and a compensatory highthroughput glycolysis (HTG). Similarly, the Warburg effect in cancer is thought to support an alkaline intracellular pH (pHi), a key component of unrelenting cell growth. In the brain, inflammation results in increased secretion of lactate by astrocytes. The increased uptake of lactic acid by neurons results in the inverse Warburg effect, such as seen in AD. The neuronal activity is dampened by a fall of pHi. Pronounced cytosol acidification results in decreased mitochondrial energy yield as well as apoptotic cell death. The link between AD and cancer is reinforced by the fact that treatment aiming at restoring the mitochondrial activity have been experimentally shown to be effective in both diseases. Low carb diet, lipoic acid, and/or methylene blue could then appear promising in both sets of these clinically diverse diseases.

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.

Methylene Blue Preserves Cytochrome Oxidase Activity and Prevents Neurodegeneration and Memory Impairment in Rats With Chronic Cerebral Hypoperfusion

Chronic cerebral hypoperfusion in neurocognitive disorders diminishes cytochrome oxidase activity leading to neurodegenerative effects and impairment of learning and memory. Methylene blue at low doses stimulates cytochrome oxidase activity and may thus counteract the adverse effects of cerebral hypoperfusion. However, the effects of methylene blue on cytochrome oxidase activity during chronic cerebral hypoperfusion have not been described before. To test this hypothesis, rats underwent bilateral carotid artery occlusion or sham surgery, received daily 4 mg/kg methylene blue or saline injections, and learned a visual water task. Brain mapping of cytochrome oxidase activity was done by quantitative enzyme histochemistry. Permanent carotid occlusion for 1 month resulted in decreased cytochrome oxidase activity in visual cortex, prefrontal cortex, perirhinal cortex, hippocampus and amygdala, and weaker interregional correlation of cytochrome oxidase activity between these regions. Methylene blue preserved cytochrome oxidase activity in regions affected by carotid occlusion and strengthened their interregional correlations of cytochrome oxidase activity, which prevented neurodegenerative effects and facilitated task-specific learning and memory. Brain-behavior correlations revealed positive correlations between performance and brain regions in which cytochrome oxidase activity was preserved by methylene blue. These results are the first to demonstrate that methylene blue prevents neurodegeneration and memory impairment by preserving cytochrome oxidase activity and interregional correlation of cytochrome oxidase activity in brain regions susceptible to chronic hypoperfusion. This demonstration provides further support for the hypothesis that lower cerebral blood flow results in an Alzheimer's-like syndrome and that stimulating cytochrome oxidase activity with low-dose methylene blue is neuroprotective.

Methylene blue inhibits Caspase-6 activity, and reverses Caspase-6-induced cognitive impairment and neuroinflammation in aged mice

Activated Caspase-6 (Casp6) is associated with age-dependent cognitive impairment and Alzheimer disease (AD). Mice expressing human Caspase-6 in hippocampal CA1 neurons develop age-dependent cognitive deficits, neurodegeneration and neuroinflammation. This study assessed if methylene blue (MB), a phenothiazine that inhibits caspases, alters Caspase-6-induced neurodegeneration and cognitive impairment in mice. Aged cognitively impaired Casp6-overexpressing mice were treated with methylene blue in drinking water for 1 month. Methylene blue treatment did not alter Caspase-6 levels, assessed by RT-PCR, western blot and immunohistochemistry, but inhibited fluorescently-labelled Caspase-6 activity in acute brain slice intact neurons. Methylene blue treatment rescued Caspase-6-induced episodic and spatial memory deficits measured by novel object recognition and Barnes maze, respectively. Methylene blue improved synaptic function of hippocampal CA1 neurons since theta-burst long-term potentiation (LTP), measured by field excitatory postsynaptic potentials (fEPSPs) in acute brain slices, was successfully induced in the Schaffer collateral-CA1 pathway in methylene blue-treated, but not in vehicle-treated, Caspase-6 mice. Increased neuroinflammation, measured by ionized calcium binding adaptor molecule 1 (Iba1)-positive microglia numbers and subtypes, and glial fibrillary acidic protein (GFAP)-positive astrocytes, were decreased by methylene blue treatment. Therefore, methylene blue reverses Caspase-6-induced cognitive deficits by inhibiting Caspase-6, and Caspase-6-mediated neurodegeneration and neuroinflammation. Our results indicate that Caspase-6-mediated damage is reversible months after the onset of cognitive deficits and suggest that methylene blue could benefit Alzheimer disease patients by reversing Caspase-6-mediated cognitive decline.

Modification of NO-cGMP Pathway Differentially Affects Diazepam- and Flunitrazepam-Induced Spatial and Recognition Memory Impairments in Rodents

This study investigated the influence of sildenafil and methylene blue (MB), two modulators of the nitric oxide (NO)-cyclic guanosine-3',5'-monophosphate (cGMP) pathway on amnesic effects of two benzodiazepines (BZs) (diazepam (DZ) and flunitrazepam (FNZ)), in rodents-mice and rats. In the modified elevated plus maze (mEPM) and novel object recognition (NOR) tests, MB given ip at a dose of 5 mg/kg 5 min prior to DZ administration (0.25 or 1 mg/kg, sc) enhanced/induced memory impairment caused by DZ. When MB (2.5, 5, and 10 mg/kg) was applied 5 min prior to FNZ administration (0.05 and 0.1 mg/kg), an effect was opposite and memory impairment induced by FNZ was reduced. When sildenafil (2.5 and 5 mg/kg, ip) was applied 5 min prior to DZ, we observed a reduction of DZ-induced memory deficiency in the mEPM test. A similar effect of sildenafil was shown in the NOR test when the drug was applied at doses of 1.25, 2.5, and 5 mg/kg prior to DZ. In the mEPM test, sildenafil at abovementioned doses had no effects on FNZ-induced memory impairment. In turns, sildenafil administered at doses of 2.5 and 5 mg/kg increased the effect of FNZ on memory impairment in the NOR test. In conclusion, the NO-cGMP pathway is involved differentially into BZs-induced spatial and recognition memory impairments assessed using the NOR and mEPM tests. Modulators of the NO-cGMP pathway affect animal behavior in these tests in a different way depending on what benzodiazepine is applied.

Effects of transcranial photobiomodulation and methylene blue on biochemical and behavioral profiles in mice stress model

The effectiveness of transcranial photobiomodulation (tPBM) and methylene Blue (MB) in treating learning and memory impairments is previously reported. In this study, we investigated the effect of tPBM and MB in combination or alone on unpredictable chronic mild stress (UCMS)-induced learning and memory impairments in mice. Fifty-five male BALB/c mice were randomly allocated to five groups: control, laser sham + normal saline (NS), tPBM + NS, laser sham + MB, and tPBM + MB. All groups except the control underwent UCMS and were treated simultaneously for 4 weeks. Elevated plus maze (EPM) was used to evaluate anxiety-like behaviors. Novel object recognition (NOR) test and Barnes maze tests were used to evaluate learning and memory function. The serum cortisol and brain nitric oxide (NO), reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels were measured by spectrophotometric methods. Behavioral tests revealed that UCMS impaired learning and memory, and treatment with PBM, MB, and their combination reversed these impairments. Levels of NO, ROS, SOD activity in brain, and serum cortisol levels significantly increased while brain GPx activity and total antioxidant capacity significantly decreased in the sham + NS animals when compared with the controls. A significant improvement was observed in treatment groups due to reversion of the aforementioned molecular analysis caused by UCMS when it was compared with control levels. Both tPBM and MB in combination or alone have significant therapeutic effects on learning and memory impairments in UCMS-received animals.

Adsorption of Methylene Blue Onto Acacia Modesta Carbon: Kinetic and Thermodynamic Study

The adsorption of methylene blue was carried out by adsorbent prepared from Acacia modesta. The sample wood was collected from Dir lower Khyber Pakhtunkhwa Pakistan. Chemical activation of the sample was conducted for surface efficiency. Surface of raw and activated sample was elucidated by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) techniques. Adsorption of methylene blue was studied on raw and activated samples by kinetics adsorption at different adsorption temperatures such as 20 °C, 30 °C and 40 °C. The adsorption equilibrium was established within 2 h. Elovich, Bhangam, and Parabolic diffusion equations were applied to the adsorption kinetics data and were found fit for adsorption. From adsorption kinetic data the parameters like ΔH≠, ΔS≠ and ΔE≠ were calculated and showed that the adsorption process was spontaneous process. Entropy in descending order shows that dye molecules adsorbed in an oriented position.

Dark Rearing Does Not Prevent Rod Oxidative Stress In Vivo in Pde6brd10 Mice

Purpose

In cyclic light-reared Pde6b^rd10 mice, rod cell oxidative stress contributes to the degenerative phenotype. Dark rearing Pde6b^rd10 mice slows but does not prevent atrophy. This suggests that outer retinal oxidative stress occurs in Pde6b^rd10 mice independent of light exposure, a hypothesis tested in this study.

Methods

Mouse strains Pde6b^rd10 and C57Bl/6 (wild type) were dark reared until postnatal day (P) 23 (P23) or P30. In subgroups of dark-reared mice, (1) layer-specific excessive free radical production (i.e., an oxidative stress biomarker) in vivo via QUEnch-assiSTed magnetic resonance imaging (QUEST MRI) was indicated by a significant reduction in the greater-than-normal spin-lattice relaxation rate R1 (1/T1) with methylene blue, (2) superoxide production was measured ex vivo in whole retina (lucigenin), and (3) retinal layer spacing and thickness were assessed in vivo (optical coherence tomography, MRI).

Results

In P23 male Pde6b^rd10 mice, only the outer superior retina showed oxidative stress in vivo, as measured by QUEST MRI; a lucigenin assay confirmed supernormal superoxide production. In contrast, at P30, no evidence for retinal oxidative stress was observed. In P23 female Pde6b^rd10 mice, no retinal oxidative stress was apparent; however, at P30, oxidative stress was observed in superior inner and outer nuclear layers. Male and female Pde6b^rd10 mice at P23 had normal retinal thicknesses, whereas at P30, modest thinning was noted in inferior and superior retina.

Conclusions

We confirmed that outer retinal oxidative stress occurs in male and female dark-reared Pde6b^rd10 mice. Male and female Pde6b^rd10 mice demonstrated similar degrees of retinal thinning, but with unexpectedly distinct spatial and temporal retinal oxidative stress patterns.

Repurposing an established drug: an emerging role for methylene blue in L-DOPA-induced dyskinesia

The nitric oxide (NO) system has been proven to be a valuable modulator of L-DOPA-induced dyskinesia in Parkinsonian rodents. NO activates the enzyme soluble guanylyl cyclase and elicits the synthesis of the second-messenger cGMP. Although we have previously described the anti-dyskinetic potential of NO synthase inhibitors on L-DOPA-induced dyskinesia, the effect of soluble guanylyl cyclase inhibitors remains to be evaluated. The aim of this study was to analyze whether the clinically available non-selective inhibitor methylene blue, or the selective soluble guanylyl cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one), could mitigate L-DOPA-induced dyskinesia in 6-hydroxydopamine-lesioned rats. Here, we demonstrated that methylene blue was able to reduce L-DOPA-induced dyskinesia incidence when chronically co-administered with L-DOPA during 3 weeks. Methylene blue chronic (but not acute) administration (2 weeks) was effective in attenuating L-DOPA-induced dyskinesia in rats rendered dyskinetic by a previous course of L-DOPA chronic treatment. Furthermore, discontinuous methylene blue treatment (e.g., co-administration of methylene blue and L-DOPA for 2 consecutive days followed by vehicle and L-DOPA co-administration for 5 days) was effective in attenuating dyskinesia. Finally, we demonstrated that microinjection of methylene blue or ODQ into the lateral ventricle effectively attenuated L-DOPA-induced dyskinesia. Taken together, these results demonstrate an important role of NO-soluble guanylyl cyclase-cGMP signaling on L-DOPA-induced dyskinesia. The clinical implications of this discovery are expected to advance the treatment options for patients with Parkinson's disease.

Methylene Blue (Tetramethylthionine Chloride) Influences the Mobility of Adult Neural Stem Cells: A Potentially Novel Therapeutic Mechanism of a Therapeutic Approach in the Treatment of Alzheimer's Disease

An interest in neurogenesis in the adult human brain as a relevant and targetable process has emerged as a potential treatment option for Alzheimer's disease and other neurodegenerative conditions. The aim of this study was to investigate the effects of tetramethylthionine chloride (methylene blue, MB) on properties of adult murine neural stem cells. Based on recent clinical studies, MB has increasingly been discussed as a potential treatment for Alzheimer's disease. While no differences in the proliferative capacity were identified, a general potential of MB in modulating the migratory capacity of adult neural stem cells was indicated in a cell mobility assay. To our knowledge, this is the first time that MB could be associated with neural mobility. The results of this study add insight to the spectrum of features of MB within the central nervous system and may be helpful for understanding the molecular mechanisms underlying a potential therapeutic effect of MB.

Targeting mitochondrial dysfunction in CNS injury using Methylene Blue; still a magic bullet?

Complex, multi-factorial secondary injury cascades are initiated following traumatic brain injury, which makes this a difficult disease to treat. The secondary injury cascades following the primary mechanical tissue damage, are likely where effective therapeutic interventions may be targeted. One promising therapeutic target following brain injury are mitochondria. Mitochondria are complex organelles found within the cell, which act as powerhouses within all cells by supplying ATP. These organelles are also necessary for calcium cycling, redox signaling and play a major role in the initiation of cell death pathways. When mitochondria become dysfunctional, there is a tendency for the cell to loose cellular homeostasis and can lead to eventual cell death. Targeting of mitochondrial dysfunction in various diseases has proven a successful approach, lending support to mitochondria as a pivotal player in TBI cell death and loss of behavioral function. Within this mixed mini review/research article there will be a general discussion of mitochondrial bioenergetics, followed by a brief discussion of traumatic brain injury and how mitochondria play an integral role in the neuropathological sequelae following an injury. We will also give an overview of one relatively new TBI therapeutic approach, Methylene Blue, currently being studied to ameliorate mitochondrial dysfunction following brain injury. We will also present novel experimental findings, that for the first time, characterize the ex vivo effect of Methylene Blue on mitochondrial function in synaptic and non-synaptic populations of mitochondria.

Daily consumption of methylene blue reduces attentional deficits and dopamine reduction in a 6-OHDA model of Parkinson's disease

Recently, alternative drug therapies for Parkinson's disease (PD) have been investigated as there are many shortcomings of traditional dopamine-based therapies including difficulties in treating cognitive and attentional dysfunction. A promising therapeutic avenue is to target mitochondrial dysfunction and oxidative stress in PD. One option might be the use of methylene blue (MB), an antioxidant and metabolic enhancer. MB has been shown to improve cognitive function in both intact rodents and rodent disease models. Therefore, we investigated whether MB might treat attentional deficits in a rat model of PD induced by 6-hydroxydopamine (6-OHDA). MB also has neuroprotective capabilities against neurotoxic insult, so we also assessed the ability of MB to provide neuroprotection in our PD model. The results show that MB could preserve some dopamine neurons in the substantia nigra par compacta when 6-OHDA was infused into the medial forebrain bundle. This neuroprotection did not yield a significant behavioral improvement when motor functions were measured. However, MB significantly improved attentional performance in the five-choice task designed to measure selective and sustained attention. In conclusion, MB might be useful in improving some attentional function and preserving dopaminergic cells in this model. Future work should continue to study and optimize the abilities of MB for the treatment of PD.

Preventing the return of fear using reconsolidation updating and methylene blue is differentially dependent on extinction learning

Many factors account for how well individuals extinguish conditioned fears, such as genetic variability, learning capacity and conditions under which extinction training is administered. We predicted that memory-based interventions would be more effective to reduce the reinstatement of fear in subjects genetically predisposed to display more extinction learning. We tested this hypothesis in rats genetically selected for differences in fear extinction using two strategies: (1) attenuation of fear memory using post-retrieval extinction training, and (2) pharmacological enhancement of the extinction memory after extinction training by low-dose USP methylene blue (MB). Subjects selectively bred for divergent extinction phenotypes were fear conditioned to a tone stimulus and administered either standard extinction training or retrieval + extinction. Following extinction, subjects received injections of saline or MB. Both reconsolidation updating and MB administration showed beneficial effects in preventing fear reinstatement, but differed in the groups they targeted. Reconsolidation updating showed an overall effect in reducing fear reinstatement, whereas pharmacological memory enhancement using MB was an effective strategy, but only for individuals who were responsive to extinction.

Entropy-Controlled Cu(II)-Catalyzed Oxidation of N-Acetyl-L-Cysteine by Methylene Blue in Acidic Medium

Kinetics of the oxidation of N-acetyl-L-cysteine (NAC) by methylene blue (MB) catalyzed by Cu(II) have been investigated in presence of HCl. The reaction follows a first order kinetics in MB while the concentration order in NAC is zero. Hydrogen ions retard the rate of reaction. The reaction involves the participation of nanoparticles as revealed by SEM, XRD and FTIR techniques and a gel-like Cu-NAC network acts like the effective catalyst. The reaction conforms to Eley-Rideal mechanism at lower [NAC] while at higher [NAC], the kinetics are explained by extended Eley-Rideal mechanism. The reaction is regulated by the size and morphology of the nanoparticles and is controlled by the entropy of activation.

Multimodal Randomized Functional MR Imaging of the Effects of Methylene Blue in the Human Brain

Purpose To investigate the sustained-attention and memory-enhancing neural correlates of the oral administration of methylene blue in the healthy human brain. Materials and Methods The institutional review board approved this prospective, HIPAA-compliant, randomized, double-blinded, placebo-controlled clinical trial, and all patients provided informed consent. Twenty-six subjects (age range, 22-62 years) were enrolled. Functional magnetic resonance (MR) imaging was performed with a psychomotor vigilance task (sustained attention) and delayed match-to-sample tasks (short-term memory) before and 1 hour after administration of low-dose methylene blue or a placebo. Cerebrovascular reactivity effects were also measured with the carbon dioxide challenge, in which a 2 × 2 repeated-measures analysis of variance was performed with a drug (methylene blue vs placebo) and time (before vs after administration of the drug) as factors to assess drug × time between group interactions. Multiple comparison correction was applied, with cluster-corrected P < .05 indicating a significant difference. Results Administration of methylene blue increased response in the bilateral insular cortex during a psychomotor vigilance task (Z = 2.9-3.4, P = .01-.008) and functional MR imaging response during a short-term memory task involving the prefrontal, parietal, and occipital cortex (Z = 2.9-4.2, P = .03-.0003). Methylene blue was also associated with a 7% increase in correct responses during memory retrieval (P = .01). Conclusion Low-dose methylene blue can increase functional MR imaging activity during sustained attention and short-term memory tasks and enhance memory retrieval. © RSNA, 2016 Online supplemental material is available for this article.

Methylene blue treatment in experimental ischemic stroke: a mini review

Stroke is a leading cause of death and long-term disability. Methylene blue, a drug grandfathered by the Food and Drug Administration with a long history of safe usage in humans for treating methemoglobinemia and cyanide poisoning, has recently been shown to be neuroprotective in neurodegenerative diseases and brain injuries. The goal of this paper is to review studies on methylene blue in experimental stroke models.

Alternative mitochondrial electron transfer for the treatment of neurodegenerative diseases and cancers: Methylene blue connects the dots

Brain has exceptional high requirement for energy metabolism with glucose as the exclusive energy source. Decrease of brain energy metabolism and glucose uptake has been found in patients of Alzheimer's, Parkinson's and other neurodegenerative diseases, providing a clear link between neurodegenerative disorders and energy metabolism. On the other hand, cancers, including glioblastoma, have increased glucose uptake and rely on aerobic glycolysis for energy metabolism. The switch of high efficient oxidative phosphorylation to low efficient aerobic glycolysis pathway (Warburg effect) provides macromolecule for biosynthesis and proliferation. Current research indicates that methylene blue, a century old drug, can receive electron from NADH in the presence of complex I and donates it to cytochrome c, providing an alternative electron transfer pathway. Methylene blue increases oxygen consumption, decrease glycolysis, and increases glucose uptake in vitro. Methylene blue enhances glucose uptake and regional cerebral blood flow in rats upon acute treatment. In addition, methylene blue provides protective effect in neuron and astrocyte against various insults in vitro and in rodent models of Alzheimer's, Parkinson's, and Huntington's disease. In glioblastoma cells, methylene blue reverses Warburg effect by enhancing mitochondrial oxidative phosphorylation, arrests glioma cell cycle at s-phase, and inhibits glioma cell proliferation. Accordingly, methylene blue activates AMP-activated protein kinase, inhibits downstream acetyl-coA carboxylase and cyclin-dependent kinases. In summary, there is accumulating evidence providing a proof of concept that enhancement of mitochondrial oxidative phosphorylation via alternative mitochondrial electron transfer may offer protective action against neurodegenerative diseases and inhibit cancers proliferation.

Nontoxic singlet oxygen generator as a therapeutic candidate for treating tauopathies

Methylene blue (MB) inhibits the aggregation of tau, a main constituent of neurofibrillary tangles. However, MB's mode of action in vivo is not fully understood. MB treatment reduced the amount of sarkosyl-insoluble tau in Drosophila that express human wild-type tau. MB concurrently ameliorated the climbing deficits of transgenic tau flies to a limited extent and diminished the climbing activity of wild-type flies. MB also decreased the survival rate of wild-type flies. Based on its photosensitive efficacies, we surmised that singlet oxygen generated through MB under light might contribute to both the beneficial and toxic effects of MB in vivo. We identified rose bengal (RB) that suppressed tau accumulation and ameliorated the behavioral deficits to a lesser extent than MB. Unlike MB, RB did not reduce the survival rate of flies. Our findings indicate that singlet oxygen generators with little toxicity may be suitable drug candidates for treating tauopathies.

Methylene Blue Reduces Acute Cerebral Ischemic Injury via the Induction of Mitophagy

The treatment of stroke is limited by a short therapeutic window and a lack of effective clinical drugs. Methylene blue (MB) has been used in laboratories and clinics since the 1890s. Few studies have reported the neuroprotective role of MB in cerebral ischemia-reperfusion injury. However, whether and how MB protects against acute cerebral ischemia (ACI) injury was unclear. In this study, we investigated the effect of MB on this injury and revealed that MB protected against ACI injury by augmenting mitophagy. Using a rat middle cerebral artery occlusion (MCAO) model, we demonstrated that MB improved neurological function and reduced the infarct volume and necrosis after ACI injury. These improvements depended on the effect of MB on mitochondrial structure and function. ACI caused the disorder and disintegration of mitochondrial structure, while MB ameliorated the destruction of mitochondria. In addition, mitophagy was inhibited at 24 h after stroke and MB augmented mitophagy. In an oxygen-glucose deprivation (OGD) model in vitro, we further revealed that the elevation of mitochondrial membrane potential (MMP) by MB under OGD conditions mediated the augmented mitophagy. In contrast, exacerbating the decline of MMP during OGD abolished the MB-induced activation of mitophagy. Taken together, MB promotes mitophagy by maintaining the MMP at a relatively high level, which contributes to a decrease in necrosis and an improvement in neurological function, thereby protecting against ACI injury.

Preventive methylene blue treatment preserves cognition in mice expressing full-length pro-aggregant human Tau

Introduction

Neurofibrillary tangles (NFT) composed of Tau are hallmarks of neurodegeneration in Alzheimer disease. Transgenic mice expressing full-length pro-aggregant human Tau (2N4R Tau-ΔK280, termed Tau^ΔK) or its repeat domain (TauRD-ΔK280, TauRD^ΔK) develop a progressive Tau pathology with missorting, phosphorylation, aggregation of Tau, loss of synapses and functional deficits. Whereas TauRD^ΔK assembles into NFT concomitant with neuronal death, Tau^ΔK accumulates into Tau pretangles without overt neuronal loss. Both forms cause a comparable cognitive decline (with onset at 10mo and 12mo, respectively), which is rescued upon switch-off of transgene expression. Since methylene blue (MB) is able to inhibit Tau aggregation in vitro, we investigated whether MB can prevent or rescue Tau-induced cognitive impairments in our mouse models. Both types of mice received MB orally using different preventive and therapeutic treatment protocols, initiated either before or after disease onset. The cognitive status of the mice was assessed by behavior tasks (open field, Morris water maze) to determine the most successful conditions for therapeutic intervention.

Results

Preventive and therapeutic MB application failed to avert or recover learning and memory deficits of TauRD^ΔK mice. Similarly, therapeutic MB treatment initiated after onset of cognitive impairments was ineffective in Tau^ΔK mice. In contrast, preventive MB application starting before onset of functional deficits preserved cognition of Tau^ΔK mice. Beside improved learning and memory, MB-treated Tau^ΔK mice showed a strong decrease of insoluble Tau, a reduction of conformationally changed (MC1) and phosphorylated Tau species (AT180, PHF1) as well as an upregulation of protein degradation systems (autophagy and proteasome). This argues for additional pleiotropic effects of MB beyond its properties as Tau aggregation inhibitor.

Conclusions

Our data support the use of Tau aggregation inhibitors as potential drugs for the treatment of AD and other tauopathies and highlights the need for preventive treatment before onset of cognitive impairments.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-015-0204-4) contains supplementary material, which is available to authorized users.

Effects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobia

OBJECTIVE

Preclinical studies have shown that low-dose methylene blue increases mitochondrial cytochrome oxidase activity in the brain and improves memory retention after learning tasks, including fear extinction. The authors report on the first controlled experiment to examine the memory-enhancing effects of posttraining methylene blue administration on retention of fear extinction and contextual memory following fear extinction training.

METHOD

Adult participants displaying marked claustrophobic fear were randomly assigned to double-blind administration of 260 mg of methylene blue (N=23) or administration of placebo (N=19) immediately following six 5-minute extinction trials in an enclosed chamber. Retesting occurred 1 month later to assess fear renewal as indexed by peak fear during exposure to a nontraining chamber, with the prediction that the effects of methylene blue would vary as a function of fear reduction achieved during extinction training. Incidental contextual memory was assessed 1 and 30 days after training to assess the cognitive-enhancing effects of methylene blue independent of its effects on fear attenuation.

RESULTS

Consistent with predictions, participants displaying low end fear posttraining showed significantly less fear at the 1-month follow-up if they received methylene blue posttraining compared with placebo. In contrast, participants displaying moderate to high levels of posttraining fear tended to fare worse at the follow-up if they received methylene blue posttraining. Methylene blue's enhancement of contextual memory was unrelated to initial or posttraining claustrophobic fear.

CONCLUSIONS

Methylene blue enhances memory and the retention of fear extinction when administered after a successful exposure session but may have a deleterious effect on extinction when administered after an unsuccessful exposure session.

Methylene blue modulates β-secretase, reverses cerebral amyloidosis, and improves cognition in transgenic mice

Amyloid precursor protein (APP) proteolysis is required for production of amyloid-β (Aβ) peptides that comprise β-amyloid plaques in the brains of patients with Alzheimer disease (AD). Here, we tested whether the experimental agent methylene blue (MB), used for treatment of methemoglobinemia, might improve AD-like pathology and behavioral deficits. We orally administered MB to the aged transgenic PSAPP mouse model of cerebral amyloidosis and evaluated cognitive function and cerebral amyloid pathology. Beginning at 15 months of age, animals were gavaged with MB (3 mg/kg) or vehicle once daily for 3 months. MB treatment significantly prevented transgene-associated behavioral impairment, including hyperactivity, decreased object recognition, and defective spatial working and reference memory, but it did not alter nontransgenic mouse behavior. Moreover, brain parenchymal and cerebral vascular β-amyloid deposits as well as levels of various Aβ species, including oligomers, were mitigated in MB-treated PSAPP mice. These effects occurred with inhibition of amyloidogenic APP proteolysis. Specifically, β-carboxyl-terminal APP fragment and β-site APP cleaving enzyme 1 protein expression and activity were attenuated. Additionally, treatment of Chinese hamster ovary cells overexpressing human wild-type APP with MB significantly decreased Aβ production and amyloidogenic APP proteolysis. These results underscore the potential for oral MB treatment against AD-related cerebral amyloidosis by modulating the amyloidogenic pathway.

Methylene blue is neuroprotective against mild traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Methylene blue (MB) has known energy-enhancing and antioxidant properties. This study tested the hypothesis that MB treatment reduces lesion volume and behavioral deficits in a rat model of mild TBI. In a randomized double-blinded design, animals received either MB (n=5) or vehicle (n=6) after TBI. Studies were performed on 0, 1, 2, 7, and 14 days following an impact to the primary forelimb somatosensory cortex. MRI lesion was not apparent 1 h after TBI, became apparent 3 h after TBI, and peaked at 2 days for both groups. The MB-treated animals showed significantly smaller MRI lesion volume than the vehicle-treated animals at all time points studied. The MB-treated animals exhibited significantly improved scores on forelimb placement asymmetry and foot fault tests than did the vehicle-treated animals at all time points studied. Smaller numbers of dark-stained Nissl cells and Fluoro-Jade(®) positive cells were observed in the MB-treated group than in vehicle-treated animals 14 days post-TBI. In conclusion, MB treatment minimized lesion volume, behavioral deficits, and neuronal degeneration following mild TBI. MB is already approved by the United States Food and Drug Administration (FDA) to treat a number of indications, likely expediting future clinical trials in TBI.

Methylene blue upregulates Nrf2/ARE genes and prevents tau-related neurotoxicity

Methylene blue (MB, methylthioninium chloride) is a phenothiazine that crosses the blood brain barrier and acts as a redox cycler. Among its beneficial properties are its abilities to act as an antioxidant, to reduce tau protein aggregation and to improve energy metabolism. These actions are of particular interest for the treatment of neurodegenerative diseases with tau protein aggregates known as tauopathies. The present study examined the effects of MB in the P301S mouse model of tauopathy. Both 4 mg/kg MB (low dose) and 40 mg/kg MB (high dose) were administered in the diet ad libitum from 1 to 10 months of age. We assessed behavior, tau pathology, oxidative damage, inflammation and numbers of mitochondria. MB improved the behavioral abnormalities and reduced tau pathology, inflammation and oxidative damage in the P301S mice. These beneficial effects were associated with increased expression of genes regulated by NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE), which play an important role in antioxidant defenses, preventing protein aggregation, and reducing inflammation. The activation of Nrf2/ARE genes is neuroprotective in other transgenic mouse models of neurodegenerative diseases and it appears to be an important mediator of the neuroprotective effects of MB in P301S mice. Moreover, we used Nrf2 knock out fibroblasts to show that the upregulation of Nrf2/ARE genes by MB is Nrf2 dependent and not due to secondary effects of the compound. These findings provide further evidence that MB has important neuroprotective effects that may be beneficial in the treatment of human neurodegenerative diseases with tau pathology.

Methylene blue potentiates stimulus-evoked fMRI responses and cerebral oxygen consumption during normoxia and hypoxia

Methylene blue USP (MB) at low doses has metabolic-enhancing and antioxidant properties and exhibits experimental neurotherapeutic benefits, but little is known about its in vivo effects on cerebral blood flow (CBF), functional evoked responses, and the associated changes in cerebral metabolic rate of oxygen (CMRO2). This study used magnetic resonance imaging (MRI) to evaluate the in vivo effects of a single intravenous MB therapeutic dose (0.5mg/kg) on basal CBF, blood oxygenation level-dependent (BOLD) and CBF responses to hypercapnic (5% CO2 in air) inhalation, as well as changes in BOLD, CBF, and CMRO2 during forepaw stimulation in the rat brain. MB did not have significant effects on arterial oxygen saturation, heart rate and fMRI responses to hypercapnia. However, MB significantly potentiated forepaw-evoked BOLD and CBF changes under normoxia. To further evaluate in vivo effects of MB under metabolic stress conditions, MRI measurements were also made under mild hypoxia (15% O2). Hypoxia per se increased evoked functional MRI responses. MB under hypoxia further potentiated forepaw-evoked BOLD, CBF and oxygen consumption responses relative to normoxia. These findings provide insights into MB's effects on cerebral hemodynamics in vivo and could help to optimize treatments in neurological diseases with mitochondrial dysfunction and oxidative stress.

Neuroprotective actions of methylene blue and its derivatives

Methylene blue (MB), the first lead chemical structure of phenothiazine and other derivatives, is commonly used in diagnostic procedures and as a treatment for methemoglobinemia. We have previously demonstrated that MB could function as an alternative mitochondrial electron transfer carrier, enhance cellular oxygen consumption, and provide protection in vitro and in rodent models of Parkinson's disease and stroke. In the present study, we investigated the structure-activity relationships of MB in vitro using MB and six structurally related compounds. MB reduces mitochondrial superoxide production via alternative electron transfer that bypasses mitochondrial complexes I-III. MB mitigates reactive free radical production and provides neuroprotection in HT-22 cells against glutamate, IAA and rotenone toxicity. Distinctly, MB provides no protection against direct oxidative stress induced by glucose oxidase. Substitution of a side chain at MB's 10-nitrogen rendered a 1000-fold reduction of the protective potency against glutamate neurototoxicity. Compounds without side chains at positions 3 and 7, chlorophenothiazine and phenothiazine, have distinct redox potentials compared to MB and are incapable of enhancing mitochondrial electron transfer, while obtaining direct antioxidant actions against glutamate, IAA, and rotenone insults. Chlorophenothiazine exhibited direct antioxidant actions in mitochondria lysate assay compared to MB, which required reduction by NADH and mitochondria. MB increased complex IV expression and activity, while 2-chlorphenothiazine had no effect. Our study indicated that MB could attenuate superoxide production by functioning as an alternative mitochondrial electron transfer carrier and as a regenerable anti-oxidant in mitochondria.

Targeting the mitochondrial electron transport chain in autism, a systematic review and synthesis of a novel therapeutic approach

Autism is a complex developmental disorder with an unknown etiology and without any curative treatment. The mitochondrial electron transfer chains play a major role in the production of ATP, and the generation and management of reactive oxidative stress (ROS). This paper is a systematic review of the role of the mitochondrial electron transport chain in autism, and a consequent hypothesis for treating autism is synthesized. An electronic search with pre-specified inclusion criteria was conducted in order to retrieve all the published articles about the mitochondrial electron transport chain in autism. The two databases of PUBMED and Google Scholar were searched. From one hundred twenty five retrieved titles, 12 (three case control study and 9 case reports) articles met inclusion criteria. All of the included studies indicated dysfunction of electron transport chain in autism. The mitochondrial electron transfer chain seems impaired in some children with autism and ROS production is additionally enhanced. It is hypothesized that interventions involving alternative electron shuttling may improve autism through lowering the production of ROS. In addition, it is expected that this alternative electron shuttling to cytochrome c might enhance the production of ATP which is impaired in the disorder.

Methylene blue modulates huntingtin aggregation intermediates and is protective in Huntington's disease models

Huntington's disease (HD) is a devastating neurodegenerative disorder with no disease-modifying treatments available. The disease is caused by expansion of a CAG trinucleotide repeat and manifests with progressive motor abnormalities, psychiatric symptoms, and cognitive decline. Expression of an expanded polyglutamine repeat within the Huntingtin (Htt) protein impacts numerous cellular processes, including protein folding and clearance. A hallmark of the disease is the progressive formation of inclusions that represent the culmination of a complex aggregation process. Methylene blue (MB), has been shown to modulate aggregation of amyloidogenic disease proteins. We investigated whether MB could impact mutant Htt-mediated aggregation and neurotoxicity. MB inhibited recombinant protein aggregation in vitro, even when added to preformed oligomers and fibrils. MB also decreased oligomer number and size and decreased accumulation of insoluble mutant Htt in cells. In functional assays, MB increased survival of primary cortical neurons transduced with mutant Htt, reduced neurodegeneration and aggregation in a Drosophila melanogaster model of HD, and reduced disease phenotypes in R6/2 HD modeled mice. Furthermore, MB treatment also promoted an increase in levels of BDNF RNA and protein in vivo. Thus, MB, which is well tolerated and used in humans, has therapeutic potential for HD.

Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue

This paper provides the first review of the memory-enhancing and neuroprotective metabolic mechanisms of action of methylene blue in vivo. These mechanisms have important implications as a new neurobiological approach to improve normal memory and to treat memory impairment and neurodegeneration associated with mitochondrial dysfunction. Methylene blue's action is unique because its neurobiological effects are not determined by regular drug-receptor interactions or drug-response paradigms. Methylene blue shows a hormetic dose-response, with opposite effects at low and high doses. At low doses, methylene blue is an electron cycler in the mitochondrial electron transport chain, with unparalleled antioxidant and cell respiration-enhancing properties that affect the function of the nervous system in a versatile manner. A major role of the respiratory enzyme cytochrome oxidase on the memory-enhancing effects of methylene blue is supported by available data. The memory-enhancing effects have been associated with improvement of memory consolidation in a network-specific and use-dependent fashion. In addition, low doses of methylene blue have also been used for neuroprotection against mitochondrial dysfunction in humans and experimental models of disease. The unique auto-oxidizing property of methylene blue and its pleiotropic effects on a number of tissue oxidases explain its potent neuroprotective effects at low doses. The evidence reviewed supports a mechanistic role of low-dose methylene blue as a promising and safe intervention for improving memory and for the treatment of acute and chronic conditions characterized by increased oxidative stress, neurodegeneration and memory impairment.

Functional interaction between the dorsal hippocampus and the striatum in visual discrimination learning

The hippocampus and the striatum have traditionally been considered as part of different and independent memory systems. However, there is evidence that supports a functional interaction between the hippocampus and the dorsal striatum at least in particular learning tasks. Here, we evaluated the functional contribution of both brain regions in a visual discrimination learning task using cytochrome c oxidase (CO) quantitative histochemistry. Compared with other brain metabolic mapping techniques, CO activity reflects steady-state neuronal energy demand. Rats were trained for 6 days in a water T-maze to find a hidden escape platform associated with an intramaze visual cue. A control group of animals swam for an equivalent amount of time compared as the trained group but without any escape platform available. After finishing the behavioral task, CO activity was measured in subdivisions of the dorsal hippocampus and the dorsal striatum in both groups. Results show significantly higher CO activity in the CA1 area and the dentate gyrus of the dorsal hippocampus in the trained rats compared with the control group. In addition, a significant negative functional cross-correlation between area CA1 of the dorsal hippocampus and the anterodorsal striatum was found. Our results support current theories on competitive interaction of different memory systems during visual discrimination learning.