A Putative Role for the BCL2 Family of Proteins in the Pathophysiology of ALS.

Introduction: Although motor neuron inclusions that contain hyperphosphorylated TDP- 43 protein (p-TDP-43) are considered an important clue in the pathophysiology of ALS, the main determinants of the neuronal dysfunction remain unknown.

Method: The spinal cords and motor cortex of 17 people (n=60 tissues) who died of ALS, with 10 controls were tested for p-TDP-43/neurofibrillary tangles (NFTs), biomarkers of neuroinflammation (GFAP, TMEM 119, miR-155, IL6, TNFα, IL1β, NF-κβ), neurodegeneration (NeuN, myelin basic protein) and BCL2 family proteins (BCL2, BCLW, BCLXL, and MCL1 each pro-survival as well as BIM, PUMA, NOXA, BAK, BAX each anti-survival) using in situ based methods including immunohistochemistry.

Results: p-TDP-43 detection was strongly correlated with neuroinflammation and neurodegeneration in both humans and in a mouse model of ALS with the mutant human TDP-43 gene (B6.Cg- Tg(Prnp-TARDBP*A315T)95Balo/J). The expression of each BCL2 family protein was significantly increased compared to the controls and co-localized with p-TDP-43 in both human and mouse models.

Discussion: To test whether altering BCL2 activity affects ALS pathophysiology, the FDAapproved drug venetoclax, which blocks BCL2, was started at age 3 mo IP in these mice and prevented clinical motor neuron dysfunction (n=5), whereas the untreated littermates (n=4) each died of end-stage paralysis at 5-7 mo. Blocking Bcl2 in the ALS mice reduced neurodegeneration 5-fold and neuroinflammation by 81%.

Conclusion: It is concluded that: 1) dysregulation of BCL2 family proteins is implicated in ALS, and 2) blocking Bcl2 alone in the mouse ALS model can markedly reduce the neurodegeneration.