Gen. Pharmac. Vol. 27, No. 8, pp. 1373-1376, 1996 Copyright © 1996 Elsevier Science Inc. Printed in the USA. ELSEVIER ISSN 0306-3623/96 $15.00 + .00 PII S0306-3623(96)00072-9 All rights reserved Selective Effect of 2-(Polyhydroxyalkyl)-Thiazolidine-4-Carboxylic Acids on Nonprotein Sulfhydryl Groups in Tumor Bearing Mice L. Wtodek,* M. Wr6bel, and J. Czubak INSTITUTE OF MEDICALBIOCHEMISTRY, COLLEGIUMMEDICUM, JAGIELLONIAN UNIWRSITY, 7 KOI'ERNI~ STREET, 31-034 KRAKdw, POLAND [FAx: (48-12) 21-46-64] ABSTRACT. 1. Thiazolidine derivatives (TD), the products of condensation of L-cysteine (cys) with sugars (D-glucose, D-xylose, D-arabinose, D-galactose, and D-mannose), successfully elevated non- protein sulfhydryl (NPSH) levels in livers of Ehrlich ascites tumor (EAT)-bearing mice. 2. At the same time, TD promoted a significant drop of NPSH in EAT cells. 3. Thus, TD, through their selective influence on the levels of NPSH in liver and cancer cells ap- pear to be promising compounds for anticancer therapy. Copyright © 1996 Elsevier Science Inc. GEN eHARMAC 27;8:1373--1376, 1996. KEY WORDS. L-Cysteine, nonprotein sulfhydryl groups, thiazolidine derivatives, Ehrlich ascites tumor INTRODUCTION Glutathione (GSH) constitutes an almost complete pool of nonpro- tein sulfhydryl compounds (NPSH) in the cells; it plays an impor- tant role as a cellular protector (Meister, 1989; Reed, 1990). GSH is known as a substrate for glutathione S-transferase (EC 2.5.1.18) and glutathione peroxidase (EC 1.11.1.9), enzymes catalyzing reac- tions of detoxification of xenobiotic compounds and antioxidation of reactive species and free radicals (Bray and Taylor, 1993; Meister, 1991). Cellular GSH alters the toxicity of many chemotherapy drugs and radiation (Bray and Taylor, 1993; Durand and Olive, 1989; Meister, 1991). It has been suggested that a modulation of GSH levels would be a promising therapeutic strategy (Anderson and Meister, 1987; Meister, 1985; Meister, 1991). This is the reason for the intensive search for such compounds which, through the in- crease of GSH levels in normal cells, protect them but at the same time offer no protection for tumor cells. Obviously, the ideal drugs would be those compounds that could simultaneously elevate the GSH level in normal cells and decrease it in tumor cells. GSH alone cannot be used as a drug because it does not enter the cell (Hahn et al., 1978). Free L-cysteine (cys), as an amino acid lim- iting the biosynthesis of GSH, is very toxic to the central nervous system (Karlsen et al., 1981; Olney et al., 1971). Methionine, being a source of cys through the cystathionine pathway, decreases the level of ATP in the cells (Hardwick et al., 1970), and is not a good source of cys for GSH synthesis in the liver (Stipanuk et al., 1992). As shown in our previous studies, thiazolidine derivatives (TD) are able to increase the concentration of NPSH in the livers of healthy mice (Wtodek et al., 1993). These compounds can gradually release cys by enzymatically controlled processes or by nonenzymatic hydro- lysis (Cavallini et al., 1956; Nagasawa et al., 1984, Roberts and Francetic, 1991; Wtodek et al., 1993) (Scheme 1). Furthermore, as reported by Roberts and Francetic (1991), the condensation product of t-cysteine with D-ribose selectively ele- vated GSH levels in numerous organs of tumor-bearing mice. This is why we investigated the effect of several 2-(polyhydroxyalkyl)- thiazolidine-4-carboxylicacids, condensation products of i.-cysteine *To whom correspondence should be addressed. Received 26 October 1995; accepted 9 January 1996. with sugars, on the level of NPSH and cys in EAT cells and in the livers of tumor-bearing mice. MATERIALS AND METHODS Chemicals The following thiazolidine derivatives (TD), the condensation products of c-cysteine with sugars (D-glucose, D-xylose, D-arabinose, D-galactose, D-mannose), were used in our experiments. 1. 2-D-glucopentahydroxypentyl)-thiazolidine-4-carboxyiic acid (CGlc). 2. 2-(D-xylotetrahydroxybutyl)-thiazolidine-4-carboxylic acid (CXyl). 3. 2-(D-arabinotetmhydroxybutyl)-thiazolidine-4-carboxylic acid (CAm). 4. 2-(D-galactopentahydroxypentyl)-thiazolidine-4-carboxylic acid (CGal). 5. 2-(D-mamaopentahydroxypentyl)-thiazolidine-4-carboxylic acid (CMan). Compound numbers 3, 4, and 5 were synthesized by method A, described by Radomski and Temeriusz (1989). Compound numbers 1 and 2 were synthesized by a modified method of Weitzel et al. (1959) in the Laboratory of Organic Synthesis, Jagiellonian Univer- sity (Krak6w, Poland). c-Cysteine, reduced glutathione, 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB), and bovine serum albumin were provided by Sigma Chemical Co., and ninhydrin was from Fluka AG. The EATC were maintained in Swiss female mice, 3 months of age, with an approximate weight of 20 g, kept on a standard mouse diet. Seven days after implantation of EATC, the animals were given intraperitoneal injections of thiazolidine derivatives at the dose of 1.2 minol/kg, once a day for 3 days. The control animals were injected with the same volume of isotonic saline. At day 4, the mice were killed and their livers were dissected. EATC were collected and washed by repeat suspensions in saline. Subsequently, the livers and EATC were frozen at -30°C until needed. After thawing, tu- mor cells and livers were homogenized with 0.1 M phosphate buffer, pH 7.4 (1 g:4 mL), and centrifuged at 650 g for 15 rain to determine the levels of NPSH and cys in the supernatant fractions. NPSH was measured by reaction with 5,5-dithiobis-(2-nitroben- zoic acid) (DTNB) to yield a compound that absorbs at 412 nm (Moron et al., 1979). Cysteine was determined according to Gai- tonde (1967). Protein content was measured according to the