Methylene blue and normobaric hyperoxia combination therapy in experimental ischemic stroke

Normobaric hyperoxia therapy in acute ischemic stroke: A literature review

Background

Ischemic stroke is one of the most severe cerebrovascular diseases that leads to disability and death and seriously endangers health and quality of life. Insufficient oxygen supply is a critical factor leading to ischemic brain injury. However, effective therapies for ischemic stroke are lacking. Oxygen therapy has been shown to increase oxygen supply to ischemic tissues and improve prognosis after cerebral ischemia/reperfusion. Normobaric hyperoxia (NBHO) has been shown to have neuroprotective effects during ischemic stroke and is considered an appropriate neuroprotective therapy for ischemic stroke. Evidence indicates that NBHO plays a neuroprotective role through different mechanisms in acute ischemic stroke. Recent studies have also reported that combinations with other drug therapies can enhance the efficacy of NBHO in ischemic stroke. Here, we aimed to provide a summary of the potential mechanisms underlying the use of NBHO in ischemic stroke and an overview of the benefits of NBHO in ischemic stroke.

Methods

We screened 83 articles on PubMed and other websites. A quick review was conducted, including clinical trials, animal trials, and reviews of studies in the field of NBHO treatment published before July 1, 2023. The results were described and synthesized, and the bias risk and evidence quality of all included studies were assessed.

Results

The results were divided into four categories: the mechanism of NBHO, animal and clinical trials of NBHO, the clinical application and prospects of NBHO, and adverse reactions of NBHO.

Conclusion

NBHO is a simple, non-invasive therapy that may be delivered early after stroke onset, with promising potential for the treatment of acute ischemic stroke. However, the optimal therapeutic regimen remains uncertain. Further studies are needed to confirm its efficacy and safety.

Pretreatment with combined low-level laser therapy and methylene blue improves learning and memory in sleep-deprived mice

Low-level laser therapy (LLLT) and methylene blue (MB) were proved to have neuroprotective effects. In this study, we evaluated the preventive effects of LLLT and MB alone and in combination to examine their efficacy against sleep deprivation (SD)-induced cognitive impairment. Sixty Balb/c male mice were randomly divided into five groups as follows: wide platform (WP), SD, LLLT, MB, LMB (treatment with both LLLT and MB). Daily MB (0.5 mg/kg) was injected for ten consecutive days. An 810-nm, 10-Hz pulsed laser was used in LLLT every other day. We used the T-maze test, social interaction test (SIT), and shuttle box to assess learning and memory and PSD-95, GAP-43, and synaptophysin (SYN) markers to examine synaptic proteins levels in the hippocampus. Our results showed that SD decreased alternation rate in the T-maze test, sociability and social novelty in SIT, and memory index in the shuttle box. Single treatments were not able to reverse these in most of the behavioral parameters. However, behavioral tests showed a significant difference between combined therapy and the SD group. The levels of synaptic plasticity markers were also significantly reduced after SD. There was a significant difference between the MB group and SD animals in GAP-43 and SYN biomarkers. Combination treatment with LLLT and MB also increased GAP-43, PSD-95, and SYN compared to the SD group. We found that the combined use of LLLT and MB pretreatment is more effective in protecting SD-induced cognitive impairment, which may be imparted via modulation of synaptic proteins.

Rapid reduction of macular edema due to retinal vein occlusion with low-dose normobaric hyperoxia

PURPOSE

We investigated the effects of a relatively inexpensive, non-invasive, short-term treatment with low-dose normobaric hyperoxia (NBH) on macular edema in patients with retinal vein occlusion (RVO).

METHODS

Participants with macular edema associated with RVO were treated with 5 LPM of NBH via facemask (40% fraction of inspired oxygen, FIO2) for 3 h. Patients with non-fovea involving edema who elected to be observed returned for a second treatment 1 month later to test reproducibility.

RESULTS

A 3-h session of NBH (n = 45) resulted in decreased maximum macular thickness (MMT) (mean 7.10%, t₃₄=9.63 P<.001) and central macular thickness (CMT) (mean 4.64%, t₃₄=6.90, P<.001) when compared to untreated eyes with RVO measured over the same period of time (n = 12) or their healthy fellow eye (n = 34; MMT:t₃₄=-9.60, P<.001;CMT: t₃₄=-6.72, P<.001). Patients who had a second NBH treatment 1 month later experienced a recurrence of their edema, but demonstrated a similar significant reduction in MMT and CMT after the second NBH treatment.

CONCLUSIONS

Three-hour treatment with 40% FIO2 NBH results in a significant reduction in MMT and CMT. This study supports an ischemic mechanism for macular edema associated with retinal vein occlusion.

TRANSLATIONAL RELEVANCE

Short-term low-dose normobaric hyperoxia is a simple, inexpensive, and ubiquitous treatment that may provide an alternate or adjunctive approach to treating macular edema in patients who are resistant to or cannot afford anti-VEGF medications.

Normobaric oxygen: a novel approach for treating chronic cerebral circulation insufficiency

Chronic cerebral circulation insufficiency (CCCI) is viewed as an alarming state induced by long-term reduction in cerebral perfusion, which is associated with neurological deficits and high risk of stroke occurrence or recurrence. CCCI accounts for a large proportion of both outpatients and inpatients with cerebrovascular diseases, while management of CCCI remains a formidable challenge to clinicians. Normobaric oxygen (NBO) is an adjuvant hyperoxygenation intervention supplied with one atmosphere pressure (1 ATA =101.325 kPa). A plethora of studies have demonstrated the efficacy of NBO on the penumbra in acute stroke. NBO has been shown to increase the oxygen pressure, raise the intracranial blood flow, protect blood–brain barrier and enhance neuroprotective effects. As similar underlying mechanisms are shared by the penumbra in stroke and the ischemic–hypoxic brain tissues in CCCI, we speculate that NBO may serve as a promising therapeutic strategy for attenuating short-term symptoms or improving long-term clinical outcomes among patients with CCCI. Due to the scant research exploring the efficacy and safety of NBO for treating CCCI so far, both experimental and clinical studies are warranted to verify our hypothesis in the future.

Treadmill exercise and wheel exercise improve motor function by suppressing apoptotic neuronal cell death in brain inflammation rats

Brain inflammation is involved in many brain disorders, such as brain ischemic injury, Alzheimer diseases, and Parkinson disease. Physical exercise has been recommended for the prevention and treatment of many brain inflammatory diseases. In the present study, the effects of exercise on motor function in relation with apoptotic neuronal cell death following neuroinflammation were investigated. Moreover, we compared the effect of forced exercise with voluntary exercise on neuroinflammation-induced motor malfunction. For this study, rota-rod test, vertical pole test, foot fault test, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, immunohistochemistry for caspase-3, and western blot for Bcl-2 and Bax were performed. Lipopolysaccharide was intraventricular infused for induction of brain inflammation. Treadmill exercise and wheel exercise were conducted during 6 weeks. In the present results, Treadmill exercise and wheel exercise alleviated brain inflammation-induced motor impairments by suppressing apoptotic neuronal cell death in the motor cortex. These effects of treadmill exercise and wheel exercise were similarly appeared.

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.

Chronic oral methylene blue treatment in a rat model of focal cerebral ischemia/reperfusion

A single acute low-dose methylene blue (MB), an FDA-grandfathered drug, has been shown to ameliorate behavioral deficits and reduces MRI-defined infarct volume in experimental ischemic stroke when administered intravenously or intraperitoneally. The efficacy of chronic MB treatment in ischemic stroke remains unknown. In a randomized, double-blinded and vehicle-controlled design, we investigated the efficacy of chronic oral MB administration in ischemic stroke longitudinally up to 60 days post injury using MRI and behavioral tests, with end-point histology. The major findings were chronic oral MB treatment, compared to vehicle, i) improves functional behavioral outcomes starting on day 7 and up to 60 days, ii) reduces MRI-defined total lesion volumes from day 14 and up to 60 days where some initial abnormal MRI-defined core and perfusion-diffusion mismatch were salvaged, iii) reduces white-matter damage, iv) gray matter and white matter damages are consistent with Nissl stains and Black Gold stain histology. These findings provide further evidence that long-term oral administration of low-dose MB is safe and has positive therapeutic effects in chronic ischemic stroke.

Experimental neuroprotection in ischemic stroke: a concise review

Acute ischemic stroke (AIS) is a leading cause of disability and death worldwide. To date, intravenous tissue plasminogen activator and mechanical thrombectomy have been standards of care for AIS. There have been many advances in diagnostic imaging and endovascular devices for AIS; however, most neuroprotective therapies seem to remain largely in the preclinical phase. While many neuroprotective therapies have been identified in experimental models, none are currently used routinely to treat stroke patients. This review seeks to summarize clinical studies pertaining to neuroprotection, as well as the different preclinical neuroprotective therapies, their presumed mechanisms of action, and their future applications in stroke patients.

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.

Oxygen or cooling, to make a decision after acute ischemia stroke

The presence of a salvageable penumbra, a region of ischemic brain tissue with sufficient energy for short-term survival, has been widely agreed as the premise for thrombolytic therapy with tissue plasminogen activator (tPA), which remains the only United States Food and Drug Administration (FDA) approved treatment for acute ischemia stroke. However, the use of tPA has been profoundly constrained due to its narrow therapeutic time window and the increased risk of potentially deadly hemorrhagic transformation (HT). Blood brain barrier (BBB) damage within the thrombolytic time window is an indicator for tPA-induced HT and both normobaric hyperoxia (NBO) and hypothermia have been shown to protect the BBB from ischemia/reperfusion injury. Therefore, providing the O₂ as soon as possible (NBO treatment), freezing the brain (hypothermia treatment) to slow down ischemia-induced BBB damage or their combined use may extend the time window for the treatment of tPA. In this review, we summarize the protective effects of NBO, hypothermia or their use combined with tPA on ischemia stroke, based on which, the combination of NBO and hypothermia may be an ideal early stroke treatment to preserve the ischemic penumbra. Given this, there is an urge for large randomized controlled trials to address the effect.

Methylene blue and normobaric hyperoxia combination therapy in experimental ischemic stroke

INTRODUCTION

Ischemic stroke is a global burden that contributes to the disability and mortality of millions of patients. This study aimed to evaluate the efficacy of combined MB (methylene blue) and NBO (normobaric hyperoxia) therapy in experimental ischemic stroke.

METHODS

Rats with transient (60 min) MCAO (middle cerebral artery occlusion) were treated with: (1) air + vehicle (N = 8), (2) air + MB (N = 8), (3) NBO + vehicle (N = 7), and (4) NBO + MB (N = 9). MB (1 mg/kg) was administered at 30 min, again on days 2, 7, and 14 after stroke. NBO was given during MRI (30-150 min) on day 0, and again 1 h each during MRI on subsequent days. Serial diffusion, perfusion and T2 MRI were performed to evaluate lesion volumes. Foot-fault and cylinder tests were performed to evaluate sensorimotor function.

RESULTS

The major findings were: (1) NBO + MB therapy showed a greater decrease in infarct volume compared to NBO alone, but similar infarct volume compared to MB alone, (2) NBO + MB therapy accelerated sensorimotor functional recovery compared to NBO or MB alone, (3) Infarct volumes on day 2 did not change significantly from those on day 28 for all four groups, but behavioral function continued to show improved recovery in the NBO + MB group.

CONCLUSIONS

These findings support the hypothesis that combined NBO + MB further improves functional outcome and reduces infarct volume compared to either treatment alone and these improvements extended up to 28 days.