The antioxidant action of taurine, hypotaurine and their metabolic precursors

Abstract

It has been suggested that taurine, hypotaurine and their metabolic precursors (cysteic acid, cysteamine and cysteinesulphinic acid) might act as antioxidants in vivo. The rates of their reactions with the biologically important oxidants hydroxyl radical (.OH), superoxide radical (O2.-), hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) were studied. Their ability to inhibit iron-ion-dependent formation of .OH from H2O2 by chelating iron ions was also tested. Taurine does not react rapidly with O2.-, H2O2 or .OH, and the product of its reaction with HOCl is still sufficiently oxidizing to inactivate alpha 1-antiproteinase. Thus it seems unlikely that taurine functions as an antioxidant in vivo. Cysteic acid is also poorly reactive to the above oxidizing species. By contrast, hypotaurine is an excellent scavenger of .OH and HOCl and can interfere with iron-ion-dependent formation of .OH, although no reaction with O2.- or H2O2 could be detected within the limits of our assay techniques. Cysteamine is an excellent scavenger of .OH and HOCl; it also reacts with H2O2, but no reaction with O2.- could be measured within the limits of our assay techniques. It is concluded that cysteamine and hypotaurine are far more likely to act as antioxidants in vivo than is taurine, provided that they are present in sufficient concentration at sites of oxidant generation.

Antioxidant Effect of Taurine Against Lead-Induced Oxidative Stress

“…Therefore, a molecule can inhibit the reactions by quenching ROSs. Although several studies (Cozzi et al 1995;Redmond et al 1996) reported that taurine scavenges ROSs, this finding has not been supported by several other groups (Aruoma et al 1988;Shi et al 1997). Taurine is known to be a powerful scavenger of hypochlorous acid (HOCl) (Thomas et al 1986).…”

“…The following mechanisms have been proposed for the antioxidant effects of taurine: (1) As a direct antioxidant, taurine would quench and detoxify some reactive intermediates such as hypochlorous acid generated by myeloperoxidase (Wright et al 1986;Huxtable 1992;Timbrell et al 1995), nitric oxide (Redmond et al 1996), and H 2 O 2 (Cozzi et al 1995). Taurine was also reported to have scavenged HO • , but this scavenging activity has been shown to be weak compared to that of glucose and mannitol (Aruoma et al 1988). (2) As an indirect antioxidant, taurine may protect cells via intercalating into the membrane and stabilizing it (Nakashima et al 1982;Gordon et al 1992;Timbrell et al 1995).…”

“…Some of the recent data indicate that taurine can act as a direct antioxidant by scavenging reactive oxygen species (ROS) (Cozzi et al 1995;Redmond et al 1996) and/or as an indirect antioxidant by preventing changes in membrane permeability due to oxidant injury (Nakashima et al 1982;Banks et al 1992;Gordon et al 1992). However, some contradictory data have also been reported (Aruoma et al 1988;Shi et al 1997).…”

Protective Effect of Seleno-l-Methionine on Cyclophosphamide-Induced Urinary Bladder Toxicity in Rats

“…Previous studies have shown that CP toxicity is associated with oxidative cell damage [27]; thus, therapeutic strategies aim to limit free radical-mediated urinary bladder injury [28].…”

Organic osmolytes as compatible, metabolic and counteracting cytoprotectants in high osmolarity and other stresses

“…Of all solutes accumulated at relatively high concentrations in some situations, hypotaurine, with its reactive sulfur atom ( Fig.·2), is one of the strongest antioxidants, able to scavenge OH radicals (which bond to the sulfur atom, converting hypotaurine into taurine) as well as HOCl (Aruoma et al, 1988). Hypotaurine is known to occur at osmotically P. H. Yancey 2822 significant levels in two situations: mammalian reproductive fluids (where it appears to act as an osmolyte and may protect sperm and eggs from oxygen radicals; Setchell et al, 1993) and marine animals living in sulfide-laden waters (see Sulfide detoxification, below).…”