Glutathione Depletion Increases Tyrosinase Activity in Human Melanoma Cells

Véronique del Marmol¹, Francisco Solano², André Sels³, Georges Huez³, Anita Libert¹, Ferdinand Lejeune¹ and Ghanem Ghanem¹

1. ¹L.O.C.E, Faculty of Medicine, University of Brussels, Belgium
2. ²Department of Biochemistry, Faculty of Medicine, University of Murcia, Spain
3. ³Department of Molecular Biology, University of Brussels, Belgium

Received 16 October 1992; Accepted 10 July 1993. Journal of Investigative Dermatology (1993) 101, 871–874; doi:10.1111/1523-1747.ep12371709

Abstract

The aim of the present work was to estimate the effect of intracellular glutathione depletion on melanogenesis in human melanoma cells. We determined tyrosine hydroxylation activity, the rate-limiting step of the pathway, and ¹⁴C-melanin formation, an assay reflecting the global eumelanogenic pathway. Intracellular glutathione was depleted by treatment with buthionine-S-sulfoximine, a well-known inhibitor of -glutamylcysteine synthetase.

The intracellular depletion of glutathione was substantial after 20 h of incubation with 50 M buthionine-S-sulfoximine, although a significant effect could be observed after 6 h. Tyrosine hydroxylase activity increased in parallel with glutathione depletion, to reach 160% with respect to the control values during 24 h of buthionine-S-sulfoximine treatment. We have found the response to buthionine-S-sulfoximine to be dose dependent and the two different human cell lines HBL and LND1 to have similar, if not identical, responses. ¹⁴C-melanin formation assay revealed even greater activation, up to 400% of the control values. This indicates that glutathione depletion may have two distinct effects: first, a direct one on tyrosinase activity and, second, an effect on the promotion of eumelanogenesis. The stimulation of tyrosine hydroxylase can be explained by a possible inactivation of the enzyme by endogenous thiol compounds rather than by a direct effect of buthionine-S-sulfoximine itself on tyrosinase. The data suggest that thiol compounds may play a role for stimulation of melanogenesis by ultraviolet radiation.

Glutathione as a Depigmenting Agent: An Overview

• C. D. Villarama*,†*School of Medicine, University of California, San Francisco, CA, USA†College of Medicine, University of the Philippines Manila, Philippines and
• H. I. Maibach**School of Medicine, University of California, San Francisco, CA, USA

International Journal of Cosmetic Science

Volume 27 Issue 3 Page 147-153, June 2005

To cite this article: C. D. Villarama, H. I. Maibach (2005)
Glutathione as a depigmenting agent: an overview
International Journal of Cosmetic Science 27 (3), 147–153.
doi:10.1111/j.1467-2494.2005.00235.x

Abstract

Glutathione is an ubiquitous compound found in our bodies. Aside from its many ascribed biologic functions, it has also been implicated in skin lightening. We review in vitro and in vivo studies that show evidence of its involvement in the melanogenic pathway and shed light on the its anti-melanogenic effect. Proposed mechanisms of action include: (a) direct inactivation of the enzyme tyrosinase by binding with the copper-containing active site of the enzyme; (b) mediating the switch mechanism from eumelanin to phaeomelanin production; (c) quenching of free radicals and peroxides that contribute to tyrosinase activation and melanin formation; and d) modulation of depigmenting abilities of melanocytotoxic agents. These concepts supported by the various experimental evidence presented form basis for future research in the use of glutathione in the treatment of pigmentary disorders.

Opposite Regulation of Tyrosinase and Glutathione Peroxidase by Intracellular Thiols in Human Melanoma Cells

Journal Archives of Dermatological Research
Publisher Springer Berlin / Heidelberg
ISSN 0340-3696 (Print) 1432-069X (Online)
Issue Volume 289, Number 6 / May, 1997
Category Original Paper
DOI 10.1007/s004030050202
Pages 341-346
Subject Collection Medicine
SpringerLink Date Thursday, February 19, 2004

Authors
M. Benathan1
1Department of Dermatology, Centre Hospitalier Universitaire Vaudois (CHUV), 1011 Lausanne, Switzerland Fax 21-3140-378

Abstract

Conditions of oxidative stress lead to downregulation of glutathione (GSH) and glutathione peroxidase (GPO), which could be responsible for tyrosinase induction in pigment cells. To address this question, the effects of selective modulation of GSH metabolism on melanogenic parameters of slightly and highly melanized melanoma cells were examined. Under standard culture conditions (100 7M cystine, 100 7M tyrosine), the levels of GSH and the activities of glutathione reductase (GR) and GPO were found to be directly related to the pigmentation of melanoma cells. Exposure to 50 7M buthionine sulfoximine for 72 h decreased tyrosinase activity by 30-50% and GSH levels by more than 95%. In contrast, inhibition of GR activity with bis(chloroethyl)nitrosourea or stimulation of GPO activity with sodium selenite did not affect tyrosinase activity nor pigment formation in the melanoma cells tested. Since cysteine (CysH) is a precursor of the GSH tripeptide, the modulation of tyrosinase and GPO activity by the extracellular cystine concentration was also examined. When the cystine concentration was increased from 0 to 200 7M, a dose-dependent decrease in tyrosinase activity was associated with dose-dependent increases in GPO activity and in cell levels of CysH and GSH. The results indicate that cellular thiols coregulate the activities of tyrosinase and GPO in opposite directions. These interdependent processes could provide melanoma cells with protection against oxidative stress at low as well as at high thiol concentration.

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