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First published online November 28, 2008
Journal of Experimental Biology 211, 3816-3825 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.021303

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Hypotaurine and sulfhydryl-containing antioxidants reduce H₂S toxicity in erythrocytes from a marine invertebrate

J. A. Ortega, J. M. Ortega and D. Julian^*

University of Florida, P.O. Box 118525, Department of Zoology, Gainesville, FL 32611, USA

^* Author for correspondence (e-mail: djulian{at}ufl.edu)

Accepted 16 October 2008

Hypotaurine (HT) has been proposed to reduce sulfide toxicity in some deep-sea invertebrates by scavenging free radicals produced from sulfide oxidation or by scavenging sulfide via the reaction of HT with sulfide, forming thiotaurine (ThT). We tested whether HT or several antioxidants could reduce the total dissolved sulfide concentration in buffered seawater exposed to H₂S, and whether HT, ThT or antioxidants could increase the viability of Glycera dibranchiata erythrocytes exposed to H₂S in vitro. We found that 5 and 50 mmol l^–1 HT reduced the dissolved sulfide in cell-free buffer exposed to H₂S by up to 80% whereas the antioxidants glutathione ethyl ester (GEE), N-acetylcysteine (NAC), L-ascorbic acid (ASC), Tempol and Trolox had no consistent effect. Exposure of erythrocytes to 0.10%–3.2% H₂S (producing 0.18–4.8 mmol l^–1 sulfide) decreased the fraction of viable cells, as evidenced by loss of plasma membrane integrity, with virtually no cells remaining viable at 1.0% or more H₂S. Addition of HT (0.5–50 mmol l^–1) significantly increased the fraction of viable cells (e.g. from 0.01 to 0.84 at 0.32% H₂S) whereas ThT (0.5 and 5 mmol l^–1) decreased cell viability. GEE (0.03–3 mmol l^–1) and NAC (0.001–1 mmol l^–1), which contain sulfhydryl groups, increased cell viability during H₂S exposure but to a lesser extent than HT whereas ASC, Tempol and Trolox, which do not contain sulfhydryl groups, decreased viability or had no effect. These data show that HT can protect cells from sulfide in vitro and suggest that sulfide scavenging, rather than free radical scavenging, is the most important mechanism of protection.

Key words: antioxidants, hydrogen sulfide, hypotaurine, invertebrate, oxidative stress

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