Pergamon Toxicology in Vitro 12 (1998) 191-196 zyxwvutsrqponmlkjihgfedcbaZYXWVU Lead Acetate Toxicity In Vitro: Dependence on the Cell Composition of the Cultures zyxwvutsrqponm M. G. ZURICH, F. MONNET-TSCHUDI*, M. l3lkRODE’ and P. HONEGGER Institute of Physiology and ‘Institute of Occupational Health Sciences, University of Lausanne, CH-1005 Lausanne, Switzerland (Accepted 10 April 1997) Abstract-It is well known that exposure to low doses of lead causes long-lasting neurobehavioural def- icits, but the cellular changes underlying these behavioural changes remain to be elucidated. A protec- tive role of glial cells on neurons through lead sequestration by astrocytes has been proposed. The possible modulation of lead neurotoxicity by neuron-glia interactions was examined in three-dimen- sional cultures of foetal rat telencephalon. Mixed-brain cell cultures or cultures enriched in either neur- ons or glial cells were treated for IO days with lead acetate (lo@ M ), a concentration below the limit of cytotoxicity. Intracellular lead content and cell type-specific enzyme activities were determined. It was found that in enriched cultures neurons stored more lead than glial cells, and each cell type alone stored more lead than m co-culture. Moreover, glial cells but not neurons were more affected by lead in enriched culture than in co-culture. These results show that neuron-glia interactions attenuate the cellu- lar lead uptake and the glial susceptibility to lead, but they do not support the idea of a protective role of astrocytes. 0 1998 Elsevier Srience Ltd. All rights reserved Abbreviations: ChAT = choline acetyltransferase; CNP = 2’3’-cyclic necleotide 3’-phosphohydrolase; G r glia-enriched: GAD = glutamic acid decarboxylase; GS = glutamine synthetase; MIX = mixed- cell cultures; N = neuron-enriched; PBS = phosphate buffered saline. INTRODUCTION Lead (Ph) is known as one of the most toxic en- vironmental pollutants affecting primarily the ner- vous system (for review, see Angle, 1993; Clarkson, 1993; Riess and Needleman, 1992). Exposure of children to very low doses of lead can cause long- lasting neurobehavioural deficits (Riess and Needleman, 1992). Alterations of long-term poten- tiation could be related to these behavioural deficits (Altmann et al., 1991), but several studies described that all types of neural cells may be affected by lead, with a higher sensitivity for myelinating cells, followed by neurons, and then astroglia (for review, see Tiffany-Castiglioni, 1993). Lead could enter the neurons through calcium channels (Simons and Pocock, 1987). Astrocytes have also been described to take up Ph and to store it intracellulariy, both in vivo (Holtzman et al., 1984; Thomas et al., 1973) and in vitro (Holtzman et ui., 1987; Rowles et al., 1989; Tiffany-Castiglioni et al., 1986 and 1987). Furthermore, astrocytes have been proposed as an important lead target, based on their biochemical responses to Ph (Aschner et al., *Author for correspondence at: Institute of Physiology, 7 rue du Bugnon, CH-1005 Lausanne, Switzerland. 1991; Holtzman et al., 1984; Tiffany-Castiglioni et al., 1989). An hypothesis according to which astrocytes sequester Ph and thus protect the more sensitive neurons has been advanced (Holtzman ef al., 1984). The present study was undertaken to test the pro- tective role of glial cells on neurons. Aggregating brain cell cultures of rat telencephalon were used as a model for neurotoxicological studies (Honegger and Werffeli, 1988 and 1995; Zurich et al., 1994; Honegger and Schilter, 1992; Monnet-Tschudi et al., 1993 and 1995a,b). Besides the ordinary mixed brain cell aggregates, composed of both neurons and glial cells, cultures highly enriched in either neurons or glial cells were prepared (Honegger and Werffeli, 1988). The uptake of lead as well as cell type-specific enzyme activities were compared between controls and Pb-treated cultures of mixed- and cell type-enriched aggregates. MATERIALS AND METHODS Cell culture Serum-free, rotation-mediated aggregating cell cultures of foetal rat telencephalon were prepared as described previously (Honegger and Monnet- Tschudi, 1996). In brief, the forebrains of 16-day- old foetal rats (OFA/SPF; BRL, Fiillinsdorf, 0887-2333/98/$19.00+0.00 ~0 1998 Elsevier Science Ltd. All rights reserved. Printed in Great Britain PII: SO887-2333(97)00089-l