Oxidative damage, neuroinflammation, and mitochondrial dysfunction contribute to the pathogenesis of ALS, and these pathologic processes are tightly regulated by the Nrf2/ARE (NF-E2 related factor 2/antioxidant response element) signaling program. Therefore, modulation of the Nrf2/ARE pathway is an attractive therapeutic target for neurodegenerative diseases such as ALS. We examined two triterpenoids, CDDO (2-cyano-3, 12-dioxooleana-1,9-dien-28-oic acid) ethylamide (CDDO-EA) and CDDO-trifluoroethylamide (CDDO-TFEA), that potently activate Nrf2/ARE in a cell culture model of ALS and in the G93A SOD1 mouse model of ALS. Treatment of NSC-34 cells stably expressing mutant G93A SOD1 with CDDO-TFEA upregulated Nrf2 expression, and resulted in translocation of Nrf2 into the nucleus. Western blot analysis showed an increase in the expression of Nrf2/ARE-regulated proteins. When treatment started at a “presymptomatic age”, of 30 days both of these compounds significantly attenuated weight loss, enhanced motor performance and extended the survival of G93A SOD1 mice. Treatment started at a “symptomatic age”, as assessed by impaired motor performance was neuroprotective and slowed disease progression. These findings provide further evidence that compounds which activate the Nrf2/ARE signaling pathway may be useful in the treatment of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease which is currently untreatable. Inflammation plays a major role in the pathogenesis of motor neuron death in ALS. Pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and Fas ligand (FasL) are amongst the most important mediators of neuro-inflammation. We have previously demonstrated that elevation of these proinflammatory cytokines occurs in both ALS transgenic mice and in human ALS postmortem spinal cord tissues. Lenalidomide is a potent immunomodulatory agent, with the ability to down-regulate proinflammatory cytokines and up-regulate anti-inflammatory cytokines. We previously reported the neuroprotective effects of lenalidomide, when treatment was started 2 months prior to onset of disease in the G93A SOD1 transgenic mouse model of ALS. Since in ALS patients, treatment can only begin after the appearance of symptoms, we sought to determine the efficacy of lenalidomide administration starting at symptom onset in the G93A SOD1 mice. We found that lenalidomide treatment extended the survival interval from the age of onset by 18.3 days (~45%). Additionally, lenalidomide treatment improved rotarod performance, reduced weight loss, and attenuated neuronal cell death in the lumbar spinal cord. Qualitative histological analysis showed that lenalidomide treatment modestly reduced the expression of the proinflammatory cytokines Fas Ligand, IL-1β, TNF-α and CD40 ligand. RNA protection Assay (RPA) on a pre-selected panel of cytokines showed that proinflammatory cytokines were reduced and anti-inflammatory cytokines were up-regulated. These data encourage further clinical evaluation of lenalidomide as therapeutic strategy to block or slow disease progression in human ALS patients.