Bax inhibitor protects against apolipoprotein B-100-induced human motor neuron degeneration in vitro

 

Objective:

To investigate whether apolipoprotein B-100 (ApoB) in sporadic amyotrophic lateral sclerosis (sALS) cerebrospinal fluid (CSF) induces motor neuron death through the activation of pro-apoptotic cell death protein Bcl2-associated X-protein (Bax).

 

Background:

ALS is a progressive neurodegenerative disease characterized by motor neuron loss. Its sporadic form is the most prevalent, afflicting 90% of those with ALS. We previously showed that ApoB is a neurotoxic protein increased in sALS patient CSF that induces motor neuron degeneration. Mice injected intrathecally with ApoB exhibit the same motor neuron degeneration as those injected with sALS CSF, and cultured human motor neurons treated with pathogenic concentrations of ApoB undergo cell death. As Bax is a common pro-cell death regulator, we investigate in vitro whether ApoB-induced motor neuron death is Bax-dependent.

Design/Methods:

Human iPSC-derived motor neurons were cultured for 8 days, then incubated for 1 hour with 50 μM, 100 μM, or 200 μM Bax-inhibiting peptide V5 (Calbiochem). Motor neurons were then treated with 0.005 ng/μL ApoB. One day after treatment, cells were fixed for ChAT immunocytochemistry. Area of motor neuron clusters was quantified as a measure of motor neuron survival.

Results:

ApoB in sALS CSF induces human motor neuron death in vitro, as shown by significantly smaller ChAT⁺ clusters than motor neurons grown in media. However, treatment with the Bax-inhibiting peptide resulted in a dose-dependent protection against ApoB-induced motor neuron death. ChAT⁺ cluster size showed a direct positive correlation with Bax inhibitor concentration.

Conclusions:

Our in vitro studies show that ApoB-induced human motor neuron death is mediated by Bax activation, which can be prevented with a Bax inhibitor. This suggests Bax-dependent apoptosis is a likely mechanism of ApoB-induced motor neuron degeneration. Bax inhibitors may have therapeutic value in ALS.