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Published on: May 19, 2019
Binding, aggregation and photochemical properties of methylene blue in mitochondrial suspensions
Dino Gabrielli1, Eduardo Belisle, Divinomar Severino
1Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Abstract:
Methylene Blue (MB) has well-established photochemical properties and has been used in a variety of photochemical applications including photodynamic therapy. Despite the fact that most of MB's cytotoxic effects in cells are attributed to mitochondrial damage, the interactions of this dye with mitochondria and the consequent effects on photochemical properties have not yet been fully determined. We monitored MB binding, aggregation and its ability to release singlet oxygen (1O2) on irradiation when interacting with mitochondrial suspensions. MB actively binds to mitochondria and enters the matrix in a manner stimulated by the mitochondrial proton potential and by the increase in mitochondrial concentrations. The greater accumulation of MB in mitochondria with elevated proton potentials or those treated with high concentrations of MB results in the formation of MB dimers, previously shown to be less effective generators of 1O2. Accumulation of MB within mitochondria with high membrane potentials also results in the reduction of MB to the photochemically inactive leuco-MB. Indeed, irradiation of mitochondria with high proton potentials in the presence of MB results in the generation of approximately half the quantity of 1O2 compared with 1O2 generated in mitochondria with low proton potentials. These differences in photochemical properties should influence the cytotoxic effects of photodynamic treatment in the presence of MB.
Insights
Mitochondrial proton potential affects Methylene Blue (MB) photochemistry. High potentials reduce singlet oxygen (1O2) generation due to MB dimerization and reduction, impacting photodynamic therapy efficacy.
Area of Science:
- Biochemistry
- Photochemistry
- Cell Biology
Background:
- Methylene Blue (MB) is utilized in photodynamic therapy, with its cytotoxic effects linked to mitochondrial damage.
- The precise interactions of MB with mitochondria and their impact on photochemical properties remain incompletely understood.
Purpose of the Study:
- To investigate Methylene Blue (MB) binding, aggregation, and singlet oxygen (1O2) generation within mitochondria under varying conditions.
- To elucidate how mitochondrial proton potential influences MB's photochemical activity and its potential for photodynamic therapy.
Main Methods:
- Monitoring MB binding and aggregation in mitochondrial suspensions.
- Measuring singlet oxygen (1O2) release upon irradiation of mitochondria with varying MB concentrations and proton potentials.
Main Results:
- Methylene Blue (MB) actively binds to and enters mitochondria, influenced by proton potential and concentration.
- Elevated mitochondrial proton potentials promote MB dimerization and reduction to inactive leuco-MB, decreasing 1O2 generation.
- Mitochondria with high proton potentials produced approximately 50% less 1O2 compared to those with low potentials.
Conclusions:
- Mitochondrial proton potential significantly modulates Methylene Blue's (MB) photochemical properties, specifically its ability to generate singlet oxygen (1O2).
- These findings suggest that variations in mitochondrial membrane potential can alter the effectiveness of MB-based photodynamic treatments.
