It is proposed to integrate the screening phases of drug acting on nuclear receptors by generating mice that bear a hormonally responsive transgene which expression is regulated by estrogens or progestagens. The mice will be utilized for the combined secondary and tertiary screening of synthetic molecules acing on progesterone and/or estrogen receptor.
Synthetic ligands for female sex steroid receptors represent a widely employed class of drugs of ever growing importance in the fertility control and for the therapy of a large variety of pathologies (neoplasia, osteoporosis, endometriosis, premenstrual tension). It has been calculated that in industrialized countries more than one third of the total female population will be prescribed to take sex steroid hormones for about 30-40 years of their life. The side effects of these treatments (increased risk of uterine and breast cancer, increased risk of cardiovascular accidents, osteoporosis, degenerative diseases of the nervous system, etc.) have been a major source of discussion since the commercialisation of the first birth control pill. The undesired effects are linked to a) the widespread distribution of the intracellular receptors and b) the lack of tissue-specific activity displayed by synthetic agonists and antagonists of estrogen and progesterone receptor.
In additions, recent studies revealed the existence of mechanisms of cross-coupling between membrane receptors and intracellular receptors, further augmenting the possibility of undesired effects linked to the activation of intracellular receptors. Well aware of the difficulties in designing molecules endowed with tissue specificity, we proposed in BRIDGE (t-Project Animal Cell Biotechnology Programme, BIOT CT920308) to establish a series of cell lines of various origin, each expressing the receptor of interest for the screening of new molecules. The present proposal extends the previous work12 by including the design of a streamline model system, which should substantially accelerate and simplify the screening procedures for drugs acting on intracellular receptors.
Specifically, we propose to generate a transgenic animal model which will allow to test at once:
I) the tissue specificity of action of synthetic ligands;
II) their pharmacodynamics and;
III) their pharmacokinetics. While these transgenic mouse lines are initially aimed at the identification of ligands of progesterone and estrogen receptor, they are expected to decrease the costs of screening for new, more tissue-specific ligands for nuclear receptors. Besides providing a new tool for the screening of drugs, the present project proposal will generate new reagents and systems to pursue investigations on the mechanism of action of intracellular receptors. References: 1. Ma ZQ, Spreafico E., Pollio G., Maggi A., Proc.Natl.Acad.Sci. (USA) 90: 3740, 1993 2. Magalini A, Ferrari F, SavoldiG, Maggi A, DiLorenzo D. DNA and Cell Biol. 14:665671, 1995. 010107
Funding SchemeCSC - Cost-sharing contracts