|Ph.D Student||Vainshtein Alexander|
|Subject||Regulation of Differentiation and Programmed Cell Death|
of Neuronal and Glial Cells by TSPO Ligands
|Department||Department of Medicine||Supervisor||Professor Emeritus Moshe Gavish|
Expanding on a quinazoline scaffold, we have developed tricyclic compounds with biological activity. These compounds bind to the 18 kDa translocator protein (TSPO) and protect U118MG (glioblastoma cell line of glial origin) cells from glutamate-induced cell death. Fascinating, they can induce neuronal differentiation of PC12 cells (cell line of pheochromocytoma origin with neuronal characteristics) known to display neuronal characteristics, this includes outgrowth of neurites, tubulin expression, and NeuN (antigen known as ‘neuronal nuclei’, also known as Rbfox3) expression. In parallel to the neurodifferentiation process, they can amplify cell death induced by glutamate by 2.5 fold. Interestingly, the compounds MGV-1 and 2-Cl-MGV-1 can induce expansive neurite sprouting on their own and also in synergy with nerve growth factor and or glutamate. We found that exposure of U118MG cells to glutamate elevates TSPO by 3.4 fold and cyclic adenosine monophosphate (cAMP) levels by 6 fold. 2-Cl-MGV-1 mitigated this up-regulation. 24 Hour exposure to glutamate created two populations of U118MG cells, one with hyperpolarized mitochondrial membrane potential and another one with depolarized membrane potential. The depolarized population showed twice as much TSPO as the hyperpolarized one and 4.2 times more than the control. The moderate rise in TSPO levels in hyperpolarized cells could be part of the cells survival mechanism. Dimethyl sulfoxide (DMSO) was found to protect U118MG cells from glutamate but in contrast to 2-Cl-MGV-1 did not reduce the rise of cAMP levels. 2-Cl-MGV-1 also protected the microglia BV-2 mouse cells from cell death induced by hydrogen peroxide (H2O2) and sodium nitroprusside (SNP) but cell death induced by 50 mM ammonia was enhanced. These diverse effects on cells of glial origin and on cells with neuronal characteristics induced in culture by MGV-1 and 2-Cl-MGV-mimic the diverse events that take place during embryonic development of the brain (maintenance of glial integrity, differentiation of progenitor cells to mature neurons, and weeding out of non-differentiating progenitor cells). In adult animals, such mechanisms are considered important for protective, curative, and restorative processes that occur during and after brain injury and brain disease.