Objectives: 

The protective effects of estrogens in certain neurodegenerative disorders, such as Alzheimer's disease (AD), have been widely reported. Even though the molecular mechanisms of this neuroprotective activity are not well understood, experimental data suggest that the transcriptional factor NFkB actively participates in the protective response against neurodegeneration. We have investigated the effect of estrogen pre-treatment on amyloid-b peptide-induced expression of NFkB and its translocation to the nucleus.

Materials: 

Cell lines SN56 and HT22, derived respectively from mouse septum and hippocampus, were used in this study. Nuclear lysates were processed by western-blotting with specific antibodies against p50, p65, cRel and RelB to analyze the expression of different NFkB subunits. To determine intracellular localization of the different subunits, we performed immunocytochemical experiments that were analyzed by confocal microscopy. In addition, NFkB transcriptional activity was detected on nuclear lysates by ELISA.

Results: 

The presence of p50, p65, cRel and RelB was confirmed by western-blotting in both cell lines. By immunocytochemistry we found that exposure to amyloid-b peptide (Ab,10mM) for 20 min induced an increase of p50 and RelB in the nucleus of SN56, while p65 and cRel were increased in the nucleus of HT22. Pretreatment with estradiol (10nM) for 15 min reduced these effects. Using nuclear extracts we studied the activity of NFkB by detection of DNA binding. Exposure to Ab induced the activation of p50, p65 and cRel in both SN56 and HT22 cells, while pretreatment with estradiol inhibited the activation of the three subunits in SN56, and that of p65 and cRel in HT22.

Conclusions: 

These findings suggest, first, that the activation of some members of the NFkB family might constitute one of the mechanisms underlying Ab toxicity in HT22 and SN56 cells, and second, that estradiol neuroprotective activity may rely, at least partially, by blocking the translocation of NFkB proteins to the nucleus.