VOLTAGE-GATED CALCIUM CHANNELS AS A POSSIBLE NEW APPROACH FOR NEURODEGENERATIVE DISEASES

Brain-derived neurotrophic factor (BDNF) is essential for neuronal survival and synaptic plasticity. In neurodegenerative conditions such as Alzheimer’s disease (AD), amyloid-beta accumulation drives excessive calcium influx via NMDA receptors, leading to calpain-mediated TrkB-FL cleavage and generation of the pathological intracellular fragment TrkB-ICD. Voltage-gated calcium channels (VGCC), particularly L-type, are expressed in excitable cell membranes and mediate calcium influx upon depolarization; their inhibition is widely used in hypertension, but their contribution to BDNF receptor cleavage remains unclear.
This work investigated novel calcium sources as potential triggers of TrkB-FL cleavage. DIV7 neocortical neurons were incubated with KCl to induce depolarization and/or EGTA, a calcium chelator, to evaluate extracellular calcium contribution. In parallel, VGCC involvement in calpain-mediated TrkB-FL cleavage was assessed by co-incubating KCl with Nifedipine (L-type), ω-Agatoxine (P/Q-type), ω-Conotoxin (N-type), SNX-482 (R-type) or Ethosuximide (T-type). Neuron homogenates were collected 24 h post-treatment and TrkB-FL, TrkB-ICD and their ratio quantified by western-blot; a time-chase assay with KCl ± Nifedipine at 8, 16 and 24 h was also performed.
KCl-depolarized neurons showed increased TrkB-ICD versus controls (p<0.05, n=4–8), with unchanged TrkB-FL, an effect rescued by EGTA (p<0.05). Among VGCC blockers, only Nifedipine reduced TrkB-ICD formation and TrkB-ICD/TrkB-FL ratio at 24 h (p<0.05, n=3–5), an effect reproduced in the time-chase assay at 16 h and 24 h (p<0.05, n=4). Altogether, these findings suggest that TrkB-FL cleavage is driven not only by NMDA-mediated calcium entry but also by L-type VGCC, supporting repurposing of approved VGCC blockers as a strategy in excitotoxicity-related disease.