Società Italiana Tossicologia
martedì 11 gennaio 2005		Last Update 20/11/2004

XII Congresso della Società Italiana di Tossicologia [Bologna, 23-26 febbraio 2000]	Back
Intervento Dott. Uwe Rudolph	Commento del nostro Inviato
Genetically modified animals in pharmacological and toxicological research: future trends Uwe Rudolph, Hanns Möhler, Florence Crestani Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland The analysis of physiological, pharmacological and toxicological functions of individual genes in the context of a living animal has been made possible by the introduction of transgenes into mammals and the possibility to mutate the mouse genome in sophisticated ways. In addition to standard knockouts, it is now possible to generate mice with point mutations, tissue-specific knockouts and inducible knockouts, thus significantly enhancing the precision of analysis. In pharmacological and toxicological research, four major areas have emerged where transgenic and targeted mutant mice have had a significant impact: 1) Generation of animal models for human disease, 2) Identification and validation of drug targets (e.g. identification of novel drug targets, identification of the function of multiple receptor subtypes, generation of "humanized" drug targets in animals), 3) Analysis of the function of drug metabolizing enzymes or receptors for toxic substances and 4) Chemical and drug safety assessment (e.g. assessment of genotoxic, nongenotoxic and/or carcinogenic actions). In the following, an example for the use of targeted mutant animals for drug target identification is given. It concerns the attribution of the pharmacological spectrum of benzodiazepines to defined GABAA receptor subtypes (a1, a2, a3, a5) by point mutation. A point mutation was introduced into the a1 subunit of the GABAA receptor in vivo [a1(H101R) "knock-in"], which rendered a1 receptors insensitive to modulation by diazepam, while the regulation by the physiological neurotransmitter GABA was left intact. In a1(H101R) mice, diazepam displayed its anxiolytic action, its myorelaxant action, its motor coordination impairing action and its ethanol-potentiating action, but did not impair motor activity or induce anterograde amnesia, while its anticonvulsant action was partially impaired. These data demonstrate that the sedative and anterograde amnesic actions of diazepam are mediated by a1-receptors, whereas the anxiolytic, myorelaxant, motor coordination impairing and ethanol-potentiating actions of diazepam are mediated by GABAA-receptor subtypes other than those containing the a1-subunit. Thus, our results provide a rational basis for the development of novel subtype-specific anxiolytics which do not bind to a1-GABAA-receptors but bind to a2-, a3-, and/or a5-GABAA-receptors. These drugs would lack the sedative and anterograde amnesic actions of diazepam, which are major undesired side effects of classical benzodiazepines. References: · Rudolph, U. & Möhler, H. (1999) Genetically modified animals in pharmacological research: future trends. European Journal of Pharmacology 375, 327-337. · Rudolph, U., Crestani, F., Benke, D., Brünig, I., Benson, J.A., Fritschy, J.-M., Martin J.R., Bluethmann, H. & Möhler, H. (1999) Benzodiazepine actions mediated by specific g-aminobutyric acidA receptor subtypes. Nature 401, 796-800
Lettura Magistrale del Dott. Uwe Rudolph Parlare di "Biotecnologie" o delle sue applicazioni al giorno d’oggi suscita sempre molto scalpore. I fantasmi evocati da una informazione scandalistica che mira a disinformare piuttosto che tutelare l’opinione pubblica hanno contribuito a creare una grossa diffidenza verso questa realtà emergente. Il XII Congresso della SITOX ha voluto affrontare queste tematiche, anche proponendo una lettura magistrale che fornisse una adeguata introduzione all’impiego di animali geneticamente modificati che possono essere utilizzati sia nella ricerca farmacologica sia tossicologica. Nella sua brillante relazione, di cui di seguito è riportato un breve riassunto, il Dr. Rudolph ha introdotto i concetti di "transgenico" e "knockout", le più moderne tecniche di sviluppo di questi animali geneticamente modificati ed il loro utilizzo nella ricerca in vivo ed in vitro. Sebbene questo campo della ricerca ancora attenda un consenso adeguato a livello internazionale, si può dire che questi modelli se pur non completamente accettati sono di grande utilità nella sperimentazione. Forse proprio grazie a questi "mosaici" potremo cercare di far luce su quei meccanismi che nel classico animale da laboratorio mancano di convincere gli addetti, proprio per la distanza filogenetica che esiste con l’uomo. Andrea Sapone