Title

 

Authors

S. Merlo, M. A. Sortino

Department of Clinical and Molecular Biomedicine - Section of Pharmacology and Biochemistry, University of Catania, Catania, Italy.

 

Abstract

The neuroprotective action of estrogen in Alzheimer’s disease has been recently related also to regulation of both degradation and synthesis of the amyloyd beta peptide (Abeta) in neuronal cells. The mechanisms involved in these actions need further elucidation. In the present study, attention has been mainly focused on the effects of 17beta-estradiol (17E2) on the expression/activation of Abeta-degrading matrix metalloproteases (MMPs) 2 and 9. Treatment of human neuroblastoma SHSY5Y cells with 10 nM 17E2 for 18 h induces a significant increase in MMPs expression. In addition enzymatic activity is enhanced, as measured by gelatin zymography. These effects are mimicked by the estrogen receptor (ER) alpha selective agonist PPT (100 nM), but not by the ERbeta selective agonist DPN (1 nM). Accordingly, effects are reduced by treatment with 1 uM ICI 182,780 and by ERalpha selective antagonist MPP (100 nM), but not by the ERbeta selective antagonist PHTPP (100 nM). Conditioned medium from the engineered Abeta over-producing H4-APPSwe neuroglioma cell line, was transferred to SHSY5Y cells pre-treated for 18 h with 17E2 to induce MMP expression. After a subsequent 24 h incubation, levels of Abeta 40 and 42 were measured by ELISA. Results show that pre-treatment with 17E2 significantly reduces Abeta in the conditioned medium compared to control, an effect inhibited in the presence of selective MMP inhibitor GM6001 (5 uM). Similarly, when SHSY5Y cells were exposed to exogenous Abeta 42 (3 uM), peptide levels after 24 h were significantly reduced by pre-treatment with 17E2, an effect abolished in the presence of GM6001. In these conditions, the neuronal toxicity exerted by Abeta 42 exposure, evaluated by MTT, is accordingly reduced by 17E2 pre-treatment but reverted in the presence of GM6001. Overall, these results point to the involvement of MMP2 and 9 in the neuroprotective effects of estrogen against Abeta 42 toxicity, mainly through up-regulation of expression and function of these Abeta-degrading enzymes. Such action seems to be selectively mediated by ERalpha.