Methylene blue modulates transendothelial migration of peripheral blood cells

Methylene blue: a controversial diagnostic acid and medication?

A narrative review of the literature was conducted to determine if the administration of methylene blue (MB) in humans has potential risks. Studies were identified from MEDLINE, Web of Science, Scopus, and Cochrane. MB is a diagnostic substance used during some diagnostic procedures and also a part of the treatment of several diseases including methemoglobinemia, vasoplegic syndrome, fosfamide-induced encephalopathy, and cyanide intoxication, and the detection of leaks or position of parathyroid corpuscles during surgery. Although the use of MB is historically justified, and it ought to be safe, because it originated as a diagnostic material, the basic toxicological characteristics of this substance are unknown. Despite reports of severe adverse effects of MB, which could significantly exceed any possible benefits evaluated for the given indication. Therefore, the clinical use of MB currently represents a controversial problem given the heterogeneity of available data and the lack of preclinical data. This is in conflict with standards of safe use of such substances in human medicinal practice. The toxic effects of the application of MB are dose-dependent and include serious symptoms such as hemolysis, methemoglobinemia, nausea and vomitus, chest pain, dyspnoea, and hypertension. Some countries regard MB as harmful because of the resulting skin irritation and triggering of an adverse inflammatory response. MB induced serotoninergic toxicity clinically manifests as neuromuscular hyperactivity. This review aims to summarize the current understanding concerning the indications for MB administration and define the potential adverse effects of MB.

Effect of Rewarming on Leukocyte-Endothelial Interaction After Deep Hypothermic Preservation

BACKGROUND The preservation of harvested organs plays an essential role in transplantation. Cold hypothermia is frequently applied but may lead to graft compromise resulting from reperfusion and rewarming injury. This study investigates the effect of deep hypothermia and posterior rewarming on leukocyte-endothelial interactions and junctional adhesion molecules. MATERIAL AND METHODS We established an in vitro model to investigate the transendothelial migration of leukocytes (TEM) during deep hypothermia (4°C) as well as during the post-hypothermic rewarming process. Additionally, leukocyte-endothelial interactions were analyzed by quantifying surface expression of the junctional adhesion molecules A (JAMA-A and JAM-B). RESULTS While deep hypothermia at 4°C was associated with reduced leukocyte infiltration, rewarming after hypothermic preservation resulted in a significant increase in TEM. This process is mainly triggered by activation of endothelial cells. Post-hypothermic rewarming caused a significant downregulation of JAM-A, whereas JAM-B was not altered through temperature modulation. CONCLUSIONS Hypothermia exerts a protective effect consisting of reduced leukocyte-endothelial interaction. Rewarming after hypothermic preservation, however, causes considerable upregulation of leukocyte infiltration. Downregulation of JAM-A may play a role in modulating TEM during hypothermia and rewarming. We conclude that the rewarming process is an essential but underestimated aspect during transplantation.

Assessment of effects of methylene blue on intestinal ischemia and reperfusion in a rabbit model: hemodynamic, histological and immunohistochemical study

BACKGROUND

Intestinal ischemia-reperfusion (IR) is an important clinical occurrence seen in common diseases, such as gastric dilatation-volvulus in dogs or colic in horses. Limited data is available on the use of methylene blue in veterinary medicine for intestinal ischemia-reperfusion. The present study aimed to compare the hemodynamic, histopathological, and immunohistochemical effects of two doses of methylene blue in two rabbit model groups In one group, 5 mg/kg IV was administered, and in another, 20 mg/kg IV was administered following a constant rate infusion (CRI) of 2 mg/kg/h that lasted 6 h. All the groups, including a control group had intestinal ischemia-reperfusion. Immunohistochemical analysis was performed using caspase-3.

RESULTS

During ischemia, hemodynamic depression with reduced perfusion and elevated lactate were observed. During reperfusion, methylene blue (MB) infusion generated an increase in cardiac output due to a positive chronotropic effect, an elevation of preload, and an intense positive inotropic effect. The changes in heart rate and blood pressure were significantly greater in the group in which methylene blue 5 mg/kg IV was administered (MB5) than in the group in which methylene blue 20 mg/kg IV dose was administered (MB20). In addition, lactate and stroke volume variations were significantly reduced, and vascular resistance was significantly elevated in the MB5 group compared with the control group and MB20 group. The MB5 group showed a significant decrease in the intensity of histopathological lesion scores in the intestines and a decrease in caspase-3 areas, in comparison with other groups.

CONCLUSIONS

MB infusion produced improvements in hemodynamic parameters in rabbits subjected to intestinal IR, with increased cardiac output and blood pressure. An MB dosage of 5 mg/kg IV administered at a CRI of 2 mg/kg/h exhibited the most protective effect against histopathological damage caused by intestinal ischemia-reperfusion. Further studies with MB in clinical veterinary pathologies are recommended to fully evaluate these findings.

Microfluidic assay for the on-chip electrochemical measurement of cell monolayer permeability

Cell monolayers, including endothelial cells lining the vasculature and blood-brain barrier, and epithelial cells lining the lung airways and gut, form a semipermeable barrier across which transport of biomolecules is tightly regulated. The assessment of barrier function is therefore critical in in vitro models of barrier-forming tissues, including microfluidic organ-on-a-chip models. Cell monolayer barrier function is commonly assessed using a fluorescent tracer-based permeability assay in both conventional Transwell and organ-on-a-chip models, but this method requires laborious manual sampling, bulky instrumentation and offline sample processing. In this work, we introduce a novel on-chip microfluidic permeability assay that replaces the traditional fluorescent tracer with an electroactive tracer. Similar to methods such as TEER, the electrochemical permeability assay eliminates the need for manual sampling and complex optical instrumentation. We validated the method by demonstrating close agreement between experimental and numerically-simulated diffusive and convective transport in the microfluidic device. Different electroactive tracers were screened for efficient electron transfer, stability and inertness relative to the cell monolayer. The assay was then used to measure the permeability of endothelial cells cultured under both static and flow culture conditions, and after exposure to a permeability mediator. In summary, the electrochemical permeability assay combines the simplicity of tracer-based permeability methods with the benefits of on-chip integration, which will ultimately facilitate the robust multiparametric characterization of barrier function in microfluidic organs-on-chips.

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.

Methylene Blue for Vasoplegic Syndrome After Cardiac Operation: Early Administration Improves Survival

BACKGROUND

Vasoplegic syndrome, defined by hypotension despite normal or increased cardiac output, is associated with high mortality rate after cardiopulmonary bypass. Methylene blue (MB) is reported to ameliorate vasoplegic syndrome through the nitric oxide pathway. We hypothesized that early administration of MB would improve outcomes in patients with vasoplegic syndrome after cardiopulmonary bypass.

METHODS

All patients that underwent cardiopulmonary bypass at our institution (Jan 1, 2011 to Jun 30, 2016) were identified through our Society of Thoracic Surgery database. Pharmacy records identified patients receiving MB within 72 hours of cardiopulmonary bypass. Multivariate logistic regression identified predictors of major adverse events among patients receiving MB.

RESULTS

A total of 118 cardiopulmonary bypass patients (3.3%) received MB for vasoplegic syndrome. These patients had a higher incidence of comorbidities, and these cases were more commonly reoperative (76.1% versus 41.2%, p < 0.0001) and complex (70.3% versus 31.8%, p < 0.0001). The only difference in preoperative medications was that MB patients had a higher rate of amiodarone use (15.3% versus 2.2%, p < 0.0001). MB patients had significantly higher rates of postoperative complications, except atrial fibrillation. Early (operating room, 40.7%) versus late (intensive care unit, 59.3%) administration of MB was associated with significantly reduced operative mortality rate (10.4% versus 28.6%, p = 0.018) and risk-adjusted major adverse events (odd ratio 0.35, p = 0.037).

CONCLUSIONS

Operative mortality rate is high in patients receiving MB for the treatment of vasoplegia after cardiopulmonary bypass. Early administration of MB improves survival and reduces the risk-adjusted rate of major adverse events in these patients.

Refractory Vasoplegic Syndrome in an Adult Patient with Infective Endocarditis: A Case Report and Literature Review

Postoperative vasoplegic syndrome (VS) is characterized by low systemic vascular resistance, normal or elevated cardiac output, and poor response to volume expansion. The incidence of VS after cardiac surgery requiring cardiopulmonary bypass is about 20%. Sometimes, VS becomes refractory and initial treatments do not work, rendering treatment a great challenge. In this study, we describe a young male patient with endocarditis undergoing tricuspid valve replacement. When being weaned off cardiopulmonary bypass, the patient experienced VS. The patient's blood pressure did not increase after the administration of a high dose of epinephrine and norepinephrine. Therefore, he was commenced on a low dose of vasopressin and gradually his blood pressure reached the normal range. Although the standard management of VS is a high dose of vasopressors, this patient was refractory to a combination of epinephrine and norepinephrine; only a vasopressin infusion was able to treat the patient. Eventually, he was weaned from bypass and the operation was terminated satisfactorily. Thereafter, the patient passed the recovery period in the cardiac intensive care unit and was discharged. It seems that vasopressin is an excellent option in refractory vasoplegia with minimal response to other vasopressors.

Influence of hypothermia and subsequent rewarming upon leukocyte-endothelial interactions and expression of Junctional-Adhesion-Molecules A and B

Patients with risks of ischemic injury, e.g. during circulatory arrest in cardiac surgery, or after resuscitation are subjected to therapeutic hypothermia. For aortic surgery, the body is traditionally cooled down to 18 °C and then rewarmed to body temperature. The role of hypothermia and the subsequent rewarming process on leukocyte-endothelial interactions and expression of junctional-adhesion-molecules is not clarified yet. Thus, we investigated in an in-vitro model the influence of temperature modulation during activation and transendothelial migration of leukocytes through human endothelial cells. Additionally, we investigated the expression of JAMs in the rewarming phase. Exposure to low temperatures alone during transmigration scarcely affects leukocyte extravasation, whereas hypothermia during treatment and transendothelial migration improves leukocyte-endothelial interactions. Rewarming causes a significant up-regulation of transmigration with falling temperatures. JAM-A is significantly modulated during rewarming. Our data suggest that transendothelial migration of leukocytes is not only modulated by cell-activation itself. Activation temperatures and the rewarming process are essential. Continued hypothermia significantly inhibits transendothelial migration, whereas the rewarming process enhances transmigration strongly. The expression of JAMs, especially JAM-A, is strongly modulated during the rewarming process. Endothelial protection prior to warm reperfusion and mild hypothermic conditions reducing the difference between hypothermia and rewarming temperatures should be considered.

Methylene blue modulates adhesion molecule expression on microvascular endothelial cells

OBJECTIVE AND DESIGN

As methylene blue (MB) has been recently proposed to preserve blood pressure in case of vasoplegic syndrome and shock, an entity directly related to systemic inflammation, we aimed to elucidate the effect of MB on the expression of adhesion-molecules in endothelial-cells.

MATERIALS AND TREATMENT

Human microvascular endothelial-cells (HuMEC-1) were treated with 10, 30 or 60 µM MB for 30 min and 2 h each. Additionally, the treated HuMEC-1 were co-cultured with either human peripheral blood mononuclear cells (PBMCs) or Jurkat cells (human T-lymphocytes) for 2 h.

METHODS

HuMEC-1 were analyzed after MB treatment and after co-culture experiments for expression of different adhesion-molecules (ICAM-1, VCAM-1, L-selectin, E-selectin) via FACS measurement and western blot analysis. The supernatants of the experiments were analyzed with regard to the soluble forms of the adhesion molecules.

RESULTS

We found that MB is able to modulate the expression of adhesion-molecules on EC. Administration of MB increases the expression of E-selectin and VCAM-1 depending on the dosage and time of exposure. ICAM-1 measurements provide evidence that different circulating blood cells can differently alter the adhesion-molecule expression on EC after MB exposure.

CONCLUSION

Our results provide evidence regarding the immunomodulatory effect of MB upon endothelial-cells after inflammation.