Many neurodegenerative diseases, including ALS, are characterized by mitochondrial dysfunction and defects
in the ubiquitin-proteasome pathway. However, why the central nervous system is more prone to these defects
than other tissues is unknown. In addition, several of the CNS-associated diseases show sexual disparity but,
again, the mechanistic source of this observation is unclear. The current application addresses both the
increased sensitivity of the CNS to proteostasis and mitochondrial defects and sex disparity. The Germain group
first described an estrogen receptor alpha (ERa) driven axis of the mitochondria unfolded protein response
(UPRmt), which promotes the activity of the proteasome, as well as the transcription of mitochondrial genes. More
recently, the Germain and Manfredi labs characterized this pathway in the SOD1-G93A model of familial ALS, a
model in which males show earlier disease onset than females. We found that females maintain the ability to
activate the ER axis of the UPRmt longer than males. These observations raise the possibility that interventions
aimed at activating the ERa axis of the UPRmt early on in the disease course may delay the progression of ALS
and potentially other CNS-associated diseases. Data presented in this application demonstrate that treatment
with the FDA-approved selective estrogen modulator (SERM) raloxifene, but not estrogen or tamoxifen up-
regulates expression of both the activity of the proteasome at multiple levels and mitochondria genes. Further,
we found that raloxifene delays disease progression in this model, in females specifically, despite the fact that
the serum level achieved in our trial was 10-fold lower than what is possible to achieve clinically in humans
treated chronically with raloxifene. This suggests that raloxifene is unique in its remarkable ability to increase
two of the key pathways associated with diseases affecting the spinal cord, such as ALS, and possibly other
components of the CNS. Moreover, our findings also suggest that if levels of raloxifene closer to those achieved
with human regimens can be achieve in mice, the protective effect of raloxifene could be much improved. Based
on these results, we propose the three following specific aims. Aim 1: Understanding the molecular basis of the
differential effect of estrogen, tamoxifen and raloxifene on the transcriptional activity of the ER in the spinal cord
and expand the analysis of their effects on other parts of the CNS. Aim 2: Optimize raloxifene delivery,, alone
or in combination with the proteasome activator oleuropein and extend the beneficial effect to males. Aim 3:
Extending raloxifene-based therapy to a mutant Ubiquilin2 mouse model of ALS/FTD. The program proposed
here is an aggressive and ambitious attempt at testing the neuroprotective effects of raloxifene in ALS. As
thousands of Americans suffer from this devastating disease, which has no effective therapy, we feel that the
ambitious approaches proposed are well justified.