In our research, we used primary hippocampal neurons to study how therapeutically significant compounds modulate mitochondria-mediated cell death during excitotoxic stress. The cover image of the June 10 issue of Biophysical Reports illustrates primary hippocampal neurons subjected to various experimental treatments. Excessive glutamate release occurs in the brain during ischemia/reperfusion (I/R) injury. To mimic I/R ex vivo, hippocampal neurons were treated with glutamate to assess cell viability under excitotoxic conditions. The effect of the drug bedaquiline (BDQ) on modulating glutamate-induced cell death was assessed by concurrently treating neurons with glutamate and BDQ. We found that whereas glutamate treatment depolarizes the mitochondrial inner membrane potential, leading to excitotoxic cell death, BDQ rescues the mitochondrial membrane potential and protects against glutamate-induced excitotoxicity. Tetramethylrhodamine methyl ester staining was used to monitor mitochondrial membrane potential in neurons. BDQ, also known as Sirturo, is the only antimycobacterial drug approved by the US Food and Drug Administration for the treatment of pulmonary multidrug-resistant tuberculosis, because of its ability to inhibit the catalytic activity of Mycobacterium tuberculosis ATP synthase. In this study, we demonstrate a novel function of BDQ in inhibiting the leak channel activity of mammalian ATP synthase and suggest its potential repurposing for other therapeutic applications.
Mitochondrial ATP synthase is the world’s smallest molecular engine that uses the rotation of its own subunits to catalyze ATP production and fulfill its canonical function in all five kingdoms of life. Nevertheless, we and others have recently discovered a novel moonlighting function of ATP synthase in forming the mitochondrial uncoupling channel, which orchestrates cell death under various pathological conditions. The ATP synthase c-subunit leak channel (ACLC) is a large-conductance, voltage-gated, calcium-sensitive channel in the mitochondrial inner membrane that selectively opens during ischemia-reperfusion injury and degenerative diseases of the heart and brain. The gating and regulatory mechanisms of the ACLC remain poorly understood despite its key role in cell death and metabolism.
The research presented in this article indicates that BDQ inhibits the single-channel activity of ACLC in a dose-dependent manner in planar lipid bilayer recordings of purified ATP synthase and the leak channel activity of the mitochondrial inner membrane in patch-clamp recordings. Furthermore, BDQ treatment prevents glutamate-induced depolarization of the mitochondrial inner membrane and cell death in primary hippocampal neurons. Our results identify ACLC as an essential mediator of glutamate-induced neuronal death and BDQ as a potent inhibitor of this pathway.
You can find more information on our work at https://sites.ua.edu/hpark36/ and https://nellimnatsakanyan.wixsite.com/mnatsakanyan-lab
— Amrendra Kumar, Olesia Lunko, Erin Smith, Ikram Mezghani, Subhash Eedarapalli, Yangyu Wu, Khondoker Adeba Ferdous, Emma Amjad, Han-A Park, and Nelli Mnatsakanyan