Divalent cation chelators citrate and EDTA unmask an intrinsic uncoupling pathway in isolated mitochondria

• Published in: Journal of bioenergetics and biomembranes 2017-02, Vol.49 (1), p.3-11
• Main Authors: Starkov, Anatoly A., Chinopoulos, Christos, Starkova, Natalia N., Konrad, Csaba, Kiss, Gergely, Stepanova, Anna, Popov, Vasily N.
• Format: Article
• Language: English
• Subjects: Adenosine diphosphate; Animal Anatomy; Animal Biochemistry; Animals; Biochemistry; Biological Transport; Bioorganic Chemistry; Brain - ultrastructure; Cations; Cations, Divalent - pharmacology; Chemistry; Chemistry and Materials Science; Chlorine; Citric Acid - pharmacology; Edetic Acid - pharmacology; Histology; Humans; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Ion Channels - metabolism; Magnesium Chloride - pharmacology; Melanoma; Melanoma - pathology; Melanoma - ultrastructure; Membranes; Mice; Mitochondria; Mitochondria - metabolism; Mitochondrial Membranes - metabolism; Morphology; Organic Chemistry; Oxygen; Protons; Rats; Reactive Oxygen Species - metabolism; Solutes
• ISSN: 0145-479X; 1573-6881
• DOI: 10.1007/s10863-016-9656-x

We demonstrate a suppression of ROS production and uncoupling of mitochondria by exogenous citrate in Mg 2+ free medium. Exogenous citrate suppressed H 2 O 2 emission and depolarized mitochondria. The depolarization was paralleled by the stimulation of respiration of mitochondria. The uncoupling action of citrate was independent of the presence of sodium, potassium, or chlorine ions, and it was not mediated by the changes in permeability of the inner mitochondrial membrane to solutes. The citrate transporter was not involved in the citrate effect. Inhibitory analysis data indicated that several well described mitochondria carriers and channels (ATPase, IMAC, ADP/ATP translocase, mPTP, mKATP) were not involved in citrate’s effect. Exogenous MgCl 2 strongly inhibited citrate-induced depolarization. The uncoupling effect of citrate was demonstrated in rat brain, mouse brain, mouse liver, and human melanoma cells mitochondria. We interpreted the data as an evidence to the existence of a hitherto undescribed putative inner mitochondrial membrane channel that is regulated by extramitochondrial Mg 2+ or other divalent cations.