Effects of mitochondrial poisons on glutathione redox potential and carotid body chemoreceptor activity

Abstract

a b s t r a c tLow oxygen sensing in chemoreceptor cells involves the inhibition of specific plasma membrane K + channels, suggesting that mitochondria-derived reactive oxygen species (ROS) link hypoxia to K + channel inhibition, subsequent cell depolarization and activation of neurotransmitter release. We have used several mitochondrial poisons, alone and in combination with the antioxidant N-acetylcysteine (NAC), and quantify their capacity to alter GSH/GSSG levels and glutathione redox potential (E GSH ) in rat diaphragm. Selected concentrations of mitochondrial poisons with or without NAC were tested for their capacity to activate neurotransmitter release in chemoreceptor cells and to alter ATP levels in intact rat carotid body (CB). We found that rotenone (1 M), antimycin A (0.2 g/ml) and sodium azide (5 mM) decreased E GSH ; NAC restored E GSH to control values. At those concentrations mitochondrial poisons activated neurotransmitter release from CB chemoreceptor cells and decreased CB ATP levels, NAC being ineffective to modify these responses. Additional experiments with 3-nitroprionate (5 mM), lower concentrations of rotenone and dinitrophenol revealed variable relationships between E GSH and chemoreceptor cell neurotransmitter release responses and ATP levels. These findings indicate a lack of correlation between mitochondrialgenerated modifications of E GSH and chemoreceptor cells activity. This lack of correlation renders unlikely that alteration of mitochondrial production of ROS is the physiological pathway chemoreceptor cells use to signal hypoxia.

Guinea Pig Oxygen-Sensing and Carotid Body Functional Properties

“…Only the non-specific depolarizing high extracellular K + stimulus was able to induce a 3 H-CA release response comparable in both species. However, when all those stimuli were applied to normoxic or chronic hypoxic rat CB a significant increase of CA release response was observed (Gomez-Niño et al, 2009a). …”

“…Incubating solutions were renewed and collected every 10 min and their content in 3 H-CA measured by scintillation counter. Experimental protocols and analytical procedures for measurement of 3 H-CA release have been described in detail in previous publications (Gomez-Niño et al, 2009a). …”

Nerve Growth Factor Induces Axonal Filopodia through Localized Microdomains of Phosphoinositide 3-Kinase Activity That Drive the Formation of Cytoskeletal Precursors to Filopodia

“…Sodium azide inhibits mitochondrial respiration through inhibition of cytochrome c oxidase (Duncan and Mackler, 1966) and ATP synthetase (Herweijer et al, 1985) resulting in dissipation of mitochondrial potential and shape changes (25 mM, 15 min treatment; Kaasik et al, 2007) and depleting ATP levels by approximately 60% within 10 min of treatment (5 mM; Gomez-Niño et al, 2009). We therefore determined the effects of sodium azide (25 mM 15–20 min treatment) on the rate of formation of axonal F-actin patches using neurons cultured in the presence or absence of NGF.…”

S-Glutathionylation: From Molecular Mechanisms to Health Outcomes

“…Another complex I inhibitor, rotenone, is used in vitro and in vivo as an experimental model for PD. Rotenone decreased the GSH redox potential, and the antioxidant and GSH precursor, NAC, reversed the rotenone-induced change in the redox potential (103). The authors used carotid body chemoreceptor cells as a model to determine the impact of mitochondrial respiratory chain blockers and a mitochondrial uncoupler on ROS production by measuring GSH, GSSG, and the redox potential.…”