Methylene blue is more toxic to erythroleukemic cells than to normal peripheral blood mononuclear cells: a possible use in chemotherapy

Abstract

Methylene blue (MB) is a phenothiazine with radio and photosensitizing properties and anti-tumoral activity. Our group has shown that MB was capable of inhibiting the in vitro growth of erythroleukemic cells with multidrug resistance (MDR). However, there are no studies comparing the cytotoxicity of this molecule for normal and tumoral cells. In this work, the cytotoxicity of MB was measured by MTT method in erythroleukemic and melanoma lineages, comparing it with that of normal cells:lymphocytes and melanocytes. MB was more cytotoxic for tumoral cells; however, there was no difference between erytroleukemic cells with or without MDR phenotype. Lymphocytes and erythroleukemic cells were much more sensitive to the effects of MB than melanoma cells and melanocytes. The proliferation of phytohemagglutinin-activated lymphocytes was inhibited when 3H-thymidine incorporation to DNA was measured. We tried to analyze whether the cells were dying, via apoptosis or necrosis, using Anexin-V and propidium iodide. Despite higher levels of Anexin-V, it was not possible to distinguish necrosis from apoptosis, as the fluorescence of MB is in the same channel as propidium iodide. The production of hydrogen peroxide was measured by cytometry using dihydrorhodamine 123 (DHR). Despite the erythroleukemic cells and lymphocytes being capable of producing free radicals, there was no relation between the production and the sensitivity of various cells to MB. Our results suggest that MB should be used as a chemotherapeutic agent, because of its preferential cytotoxic effects over tumor cells, considering the fact that MDR cells are also sensitive, and due to its radio and photosensitizing activities.

NQO1-activated phenothiazinium redox cyclers for the targeted bioreductive induction of cancer cell apoptosis

“…Importantly, MB is currently used systemically for the treatment of urinary bladder infections and as an intravenous emergency medication for cyanide poisoning and the reversal of druginduced methemoglobinemia [19] suggesting the feasibility of administering these agents as systemic chemotherapeutic agents. Earlier reports have described cytotoxic effects of selected PRC compounds, which occur independent of their action as light-activated photodynamic agents [23,25]. Interestingly, some PRC compounds have high affinity for human tumor tissue in vivo, an effect that has been used earlier for experimental melanoma radiotherapy using single injections of 131 I-labeled MB [46].…”

“…Phenothiazinium redox dyes have diverse applications as biological redox indicators, vital stains and diagnostic dyes [17], modulators of mitochondrial respiration [18], infusional antidotes against cyanide poisoning and methemoglobinemia [19], antiinfective agents [20,21], and photosensitizers [22][23][24], but their therapeutic potential and mechanism of action as anti-cancer redox chemotherapeutics are largely unexplored [23,25]. Compounds containing the 3,7-diaminophenothiazinium redox pharmacophore including thionine (T, 3,7-diamino-phenothiazinium acetate), methylene blue (MB, 3,7-bis (dimethylamino)-phenothiazinium chloride), and toluidine blue O (TB, 2-methyl-3-amino-7-dimethylamino-phenothiazinium chloride) are two-electron redox systems with standard reduction potentials [e.g.…”

Redox-Directed Cancer Therapeutics: Molecular Mechanisms and Opportunities

“…4-14) selectively target melanoma and other cancer cells with induction of mitochondrial apoptosis based on bioreductive activation and redox cycling (194,379). Remarkably, the phenothiazinium redox cycler (PRC) methylene blue is in clinical use worldwide as infusional redox antidote against cyanide poisoning and methemoglobinemia, a therapeutic application that suggests feasibility of systemic administration for investigational evaluation of potential oncological applications (48,219).…”

Inativação fotodinâmica de microrganismos

“…Um estudo comparativo da citotoxicidade do AM no escuro em células normais e tumorais verificou que esse corante é mais citotóxico em células tumorais 58,59 . O fato de que tanto células MDR como cepas de bactérias resistentes a múltiplos antibióticos também são sensíveis ao corante 6 sugere que AM pode ser usado como um agente quimioterapêutico.…”