Methylene blue attenuates renal ischemia-reperfusion injury in rats

The Proximal Tubule as the Pathogenic and Therapeutic Target in Acute Kidney Injury

BACKGROUND

In 2004, the term acute kidney injury (AKI) was introduced with the intention of broadening our understanding of rapid declines in renal function and to replace the historical terms of acute renal failure and acute tubular necrosis (ATN). Despite this evolution in terminology, the mechanisms of AKI have stayed largely elusive with the pathophysiological concepts of ATN remaining the mainstay in our understanding of AKI.

SUMMARY

The proximal tubule (PT), having the highest mitochondrial content in the kidney and relying heavily on oxidative phosphorylation to generate ATP, is vulnerable to ischaemic insults and mitochondrial dysfunction. Histologically, pathological changes in the PT are more consistent than changes to the glomeruli or the loop of Henle in AKI. Physiologically, activation of tubuloglomerular feedback due to PT dysfunction leads to an increase in preglomerular afferent arteriole resistance and a reduction in glomerular filtration. Pharmacologically, frusemide - a drug commonly used in the setting of oliguric AKI - is actively secreted by the PT and its diuretic effect is compromised by its failure to be secreted into the urine and thus be delivered to its site of action at the loop of Henle in AKI. Increases in the urinary, but not plasma biomarkers, of PT injury within 1 h of shock suggest that the PT as the initiation pathogenic target of AKI.

KEY MESSAGE

Therapeutic agents targeting specifically the PT epithelial cells, in particular its mitochondria - including amino acid ergothioneine and superoxide scavenger MitoTEMPO - show great promises in ameliorating AKI.

Oil-In-Water Microemulsion Encapsulation of Antagonist Drugs Prevents Renal Ischemia-Reperfusion Injury in Rats

Developing new therapeutic drugs to prevent ischemia/reperfusion (I/R)-induced renal injuries is highly pursued. Liposomal encapsulation of spironolactone (SP) as a mineralocorticoid antagonist increases dissolution rate, bioavailability and prevents the drug from degradation. In this context, this work develops a new formulation of oil-in-water type microemulsions to enhance the bioavailability of SP. The size of the SP-loaded microemulsion was about 6.0 nm by dynamic light scattering analysis. Briefly, we investigated the effects of nano-encapsulated SP (NESP) on renal oxidative stress, biochemical markers and histopathological changes in a rat model of renal I/R injury. Forty eight male Wistar rats were divided into six groups. Two groups served as control and injury model (I/R). Two groups received “conventional” SP administration (20 mg/kg) and NESP (20 mg/kg), respectively, for two days. The remaining two groups received SP (20 mg/kg) and NESP (20 mg/kg) two days before induction of I/R. At the end of the experiments, serum and kidneys of rats underwent biochemical, molecular and histological examinations. Our results showed that I/R induces renal oxidative stress, abnormal histological features and altered levels of renal biomarkers. Administration of SP in healthy animals did not cause any significant changes in the measured biochemical and histological parameters compared to the control group. However, SP administration in the I/R group caused some corrections in renal injury, although it could not completely restore I/R-induced renal oxidative stress and kidney damage. On the contrary, NESP administration restored kidney oxidative injury via decreasing renal lipid peroxidation and enhancing glutathione, superoxide dismutase and catalase in kidneys of the I/R group. The deviated serum levels of urea, creatinine, total proteins and uric acid were also normalized by NESP administration. Furthermore, NESP protected against renal abnormal histology features induced by I/R. Therefore, NESP has beneficial effects in preventing kidney damage and renal oxidative stress in a rat model of I/R, which deserves further evaluations in the future.

Effects of Methylene Blue on Ovarian Torsion-Detorsion Injury in a Rat Model

STUDY OBJECTIVES

Methylene blue (MB) is an antioxidant that ameliorates ischemia-reperfusion injury in several tissues. We analyzed the effects of MB as an inhibitor of torsion-detorsion injury in rat ovaries.

METHODS

Rats were randomly divided into 5 groups. Group 1 was the sham group, in which only laparotomy was performed. Group 2 was the torsion group, with 3 hours of ischemia. Group 3 was the torsion + MB group, with 3 hours of ischemia after MB administration. Group 4 was the torsion-detorsion group, with 3 hours of ischemia and reperfusion. Finally, group 5 was the torsion-detorsion + MB group, with 3 hours of ischemia and MB administration before detorsion/reperfusion. Ovary injuries were histopathologically scored. Malondialdehyde (MDA) and total protein levels in ovarian tissues were determined, and long pentraxin-3 (PTX3) levels were measured in ovarian tissue using an enzyme-linked immunosorbent assay.

RESULTS

In comparing group 4 with group 5 and group 2 with 3, histopathological parameters reflecting injury were significantly increased in groups 4 and 2. Group 3 generated increased MDA levels when compared with group 2 (P < .05). However, there was no significant difference between groups 2 and 3 in terms of plasma PTX3 levels. MDA and PTX3 levels decreased in group 5 in comparison with group 4 for MDA (P < .000) and PTX3 levels (P < .01).

CONCLUSIONS

MB alleviated ischemia-reperfusion ovary injury in our experimental model.

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.

Methylene blue and the NO/cGMP pathway in solid organs transplants

The nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway has a significative influence in hemodynamic changes that occur in transplants. Classically, the ischemia-reperfusion syndrome (IRS) is characterized by hypotension and low vascular resistance, when cGMP and nitric oxide (NO) are increased, contributing to oxidative stress, within an inflammatory context. These mechanisms occur in several types of transplants, such as liver, heart, lungs, kidney, which are a therapeutic choice in several clinical conditions when conventional treatments failed. It is well known the significant relation between graft dysfunction or rejection and ischemia-reperfusion injury that is linked to inflammatory response and NO/cGMP pathway activation. This review aims to study the NO/cGMP pathway in solid organ transplants. Finally, we inquire whether physicians do not underestimate the NO/cGMP pathway.

Ischemia/Reperfusion Injury Revisited: An Overview of the Latest Pharmacological Strategies

Ischemia/reperfusion injury (IRI) permeates a variety of diseases and is a ubiquitous concern in every transplantation proceeding, from whole organs to modest grafts. Given its significance, efforts to evade the damaging effects of both ischemia and reperfusion are abundant in the literature and they consist of several strategies, such as applying pre-ischemic conditioning protocols, improving protection from preservation solutions, thus providing extended cold ischemia time and so on. In this review, we describe many of the latest pharmacological approaches that have been proven effective against IRI, while also revisiting well-established concepts and presenting recent pathophysiological findings in this ever-expanding field. A plethora of promising protocols has emerged in the last few years. They have been showing exciting results regarding protection against IRI by employing drugs that engage several strategies, such as modulating cell-surviving pathways, evading oxidative damage, physically protecting cell membrane integrity, and enhancing cell energetics.

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

Objective

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

Methods

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

Results

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

Conclusion

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

Heme oxygnease-1 induction by methylene blue protects RAW264.7 cells from hydrogen peroxide-induced injury

Although methylene blue (MB) has showed strong antioxidant effect, its effect related with heme oxygenase-1 (HO-1) is still unclear. Thus, we investigated the effects of MB on HO-1 protein content and enzyme activity, and its protective effect against hydrogen peroxide (H₂O₂)-induced oxidative damage in RAW264.7 macrophage. The cell viability and the release of lactate dehydrogenase of RAW264.7 were determined. The mitochondrial functions were valuated through these indexes: content of adenosine triphosphate, superoxide dismutase, concentration of reactive oxygen species and mitochondrial membrane potential. Meanwhile, high content screening tested generation of ROS, MMP and intracellular concentration of calcium ion. qRT-PCR valuated macrophage phenotype markers expression. Lastly, flow cytometry and caspase-3 detection analyzed RAW264.7 apoptosis. Our data showed that (1) Both pretreatment and posttreatment of MB increased HO-1 protein content and enzyme activity; (2) MB rescued cells from H₂O₂-induced mitochondrial dysfunction; (3) High content screening revealed that MB alleviated the changes including generation of reactive oxygen species, mitochondrial membrane potential and intracellular concentration of calcium ion in H₂O₂ exposed RAW264.7; (4) MB attenuated H₂O₂-induced apoptosis; (5) MB pretreatment decreased the expression of M1 macrophage markers (Tnf and Nos2) while increasing the expression of M2 macrophage markers (Mrc1 and Il10); (6) The beneficial effect of MB was abolished by zinc protoporphyrin IX (HO-1 activity inhibitor) or HO-1 siRNA. In summary, MB protects RAW264.7 cells from H2O2-induced injury through up-regulation HO-1.

Methylene Blue Protects the Isolated Rat Lungs from Ischemia-Reperfusion Injury by Attenuating Mitochondrial Oxidative Damage

INTRODUCTION

Impaired mitochondrial function is a key factor attributing to the lung ischemia reperfusion injury (LIRI). Methylene blue (MB) has been reported to attenuate brain and renal ischemia-reperfusion injury. We hypothesized that MB also could have a protective effect against LIRI by preventing mitochondrial oxidative damage.

METHODS

Isolated rat lungs were assigned to the following four groups (n = 6): a sham group: perfusion for 105 min without ischemia; I/R group: shutoff of perfusion and ventilation for 45 min followed by reperfusion for 60 min; and I/R + MB group and I/R + glutathione (GSH) group: 2 mg/kg MB or 4 μM glutathione were intraperitoneally administered for 2 h, and followed by 45 min of ischemia and 60 min of reperfusion.

RESULTS

MB lessened pulmonary dysfunction and severe histological injury induced by ischemia-reperfusion injury. MB reduced the production of reactive oxygen species and malondialdehyde and enhanced the activity of superoxide dismutase. MB also suppressed the opening of the mitochondrial permeability transition pore and partly preserved mitochondrial membrane potential. Moreover, MB inhibited the release of cytochrome c from the mitochondria into the cytosol and decreased apoptosis. Additionally, MB downregulated the mRNA expression levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18).

CONCLUSION

MB protects the isolated rat lungs against ischemia-reperfusion injury by attenuating mitochondrial damage.