Taurine inhibition of metal-stimulated catecholamine oxidation

Abstract

Taurine is an abundant amino acid found in mammalian tissues and it has been suggested to have cytoprotective functions. The aim of the present study was to determine if taurine had the potential to reduce oxidative stress associated with metal-stimulated catecholamine oxidation. Taurine and structural analogs of taurine were tested for their ability to inhibit metal-stimulated quinone formation from dopamine or L-dopa. Oxidative damage to proteins and lipids were also assessed in vitro and the effects of taurine were determined. Taurine (20 mM) was found to decrease significantly ferric iron (50-500 microM)- and manganese (10 microM)-stimulated L-dopa or dopamine oxidation. Taurine had no effect on zinc-induced dopamine oxidation and slightly potentiated copper- and NaIO(4)-stimulated quinone formation. Ferric iron-stimulated lipid peroxidation was not affected by taurine (1-20 mM). Protein carbonyl formation induced by ferric iron (500 microM) and L-dopa (500 microM) was significantly reduced by 10 mM taurine. The cytotoxicity of L-dopa (250 microM) and ferric chloride (75 microM) to LLC-PK(1) cells was attenuated by 10 mM taurine or hypotaurine. Homotaurine alone stimulated L-dopa oxidation and potentiated the cytotoxic effects of ferric iron. Homotaurine was found to be cytotoxic when combined with L-dopa or L-dopa/iron. In contrast, hypotaurine inhibited quinone formation and protected LLC-PK(1) cells. These studies suggest that taurine may exhibit cytoprotective effects against the oxidation products of catecholamines by acting as a scavenger for free radicals and cytotoxic quinones.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure.

“…The iron shielding hypothesis is also consistent with experimental observations showing that taurine can protect living cells and organisms against toxic effects of iron (39, 181–183), and that it can inhibit iron catalyzed catecholamine autoxidation in vitro (525, 526). However, these observations are not sufficient to be taken as proof that the iron shielding hypothesis is correct, and it is not clear if the experimental conditions in the in vitro catecholamine autoxidation experiments were similar enough to conditions in living cells that mixed phosphate-iron-taurine complexes could have been formed as abundantly as normally may happen in various intracellular compartments, when the concentrations of taurine and various organic phosphate compounds simultaneously are high.…”

Modulatory Effects of Melatonin on Cadmium-Induced Changes in Biogenic Amines in Rat Hypothalamus

“…Decreased DA concentration could be explained, at least partially, by an inhibition of the biogenic amine synthesis, or may be due to the metal-stimulated catecholamine oxidation, that results in quinone formation, closely linked to mitochondrial dysfunction, inflammation, and oxidative stress (Dawson et al 2000). The observed DA depletion could be related to the inhibitory cadmium effect on NE, as DA is a metabolic precursor of NE (Von Bohlen und Halbach and Dermietzel 2002).…”

Physio-Pharmacological Potentials of Taurine: A Review in Animal and Human Studies

“…Taurine, a 2-aminomethane sulfonic acid, is mostly found in almost all cells, especially excitable ones 1 . Its cytoprotective activities have a substantial impact on the health and nutritional state of numerous species, regulating essential cellular events and balancing life and death 2 .…”