H2O2-mediated modulation of cytosolic signaling and organelle function in rat hippocampus

• Published in: Pflügers Archiv Vol. 458; no. 5; pp. 937 - 952
• Main Authors: Gerich, Florian J., Funke, Frank, Hildebrandt, Belinda, Faßhauer, Martin, Müller, Michael
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2009; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Biomedicine; Cell Biology; Cells; Human Physiology; Molecular Medicine; Neurosciences; Proteins; Receptors; Signaling and Cell Physiology; Oxidative stress; Mitochondrial dysfunction; Metabotropic signaling; Intracellular calcium stores; Redox signaling; Autofluorescence
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s00424-009-0672-0

Reactive oxygen species (ROS) released from (dys-)functioning mitochondria contribute to normal and pathophysiological cellular signaling by modulating cytosolic redox state and redox-sensitive proteins. To identify putative redox targets involved in such signaling, we exposed hippocampal neurons to hydrogen peroxide (H 2 O 2 ). Redox-sensitive dyes indicated that externally applied H 2 O 2 may oxidize intracellular targets in cell cultures and acute tissue slices. In cultured neurons, H 2 O 2 (EC 50 118 µM) induced an intracellular Ca 2+ rise which could still be evoked upon Ca 2+ withdrawal and mitochondrial uncoupling. It was, however, antagonized by thapsigargin, dantrolene, 2-aminoethoxydiphenyl borate, and high levels of ryanodine, which identifies the endoplasmic reticulum (ER) as the intracellular Ca 2+ store involved. Intracellular accumulation of endogenously generated H 2 O 2 —provoked by inhibiting glutathione peroxidase—also released Ca 2+ from the ER, as did extracellular generation of superoxide. Phospholipase C (PLC)-mediated metabotropic signaling was depressed in the presence of H 2 O 2 , but cytosolic cyclic adenosine-5′-monophosphate (cAMP) levels were not affected. H 2 O 2 (0.2–5 mM) moderately depolarized mitochondria, halted their intracellular trafficking in a Ca 2+ - and cAMP-independent manner, and directly oxidized cellular nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH 2 ). In part, the mitochondrial depolarization reflects uptake of Ca 2+ previously released from the ER. We conclude that H 2 O 2 releases Ca 2+ from the ER via both ryanodine and inositol trisphosphate receptors. Mitochondrial function is not markedly impaired even by millimolar concentrations of H 2 O 2 . Such modulation of Ca 2+ signaling and organelle interaction by ROS affects the efficacy of PLC-mediated metabotropic signaling and may contribute to the adjustment of neuronal function to redox conditions and metabolic supply.