Journal Image
CNS & Neurological Disorders - Drug Targets
(Formerly Current Drug Targets - CNS & Neurological Disorders)
ISSN (Print): 1871-5273
ISSN (Online): 1996-3181
DOI: 10.2174/18715273113126660194      Price:  $58

Concentration-Dependent Bimodal Effect of Specific 18 kDa Translocator Protein (TSPO) Ligands on Cell Death Processes Induced by Ammonium Chloride: Potential Implications for Neuropathological Effects Due to Hyperammonemia

Author(s): Beatriz Caballero, Leo Veenman, Julia Bode, Svetlana Leschiner and Moshe Gavish
Pages 574-592 (19)
The role of the 18-kDa Translocator Protein (TSPO) in cell death induced by NH4Cl (1-50 mM) for 24-72 hours to human glioblastoma U118MG cells was investigated. Cell death was already observed after 48 hours of treatment with NH4Cl at 5 mM. Dose and time-responses curves indicated that 15 mM of NH4Cl applied for 72 hours was the optimal condition for our viability assays. For example, 72 hours of 15 mM of NH4Cl caused a 50.3% increase in propidium iodide uptake, and lactate dehydrogenase release was 41.2% of the positive control, indicating significant increases in cell death. Furthermore, compared to vehicle control, these experimental conditions resulted in a significant decrease of 44.9% of the mitochondrial activity, a 62.3% increase in incidence of collapse of mitochondrial membrane potential, and an increase of 49.0% of cardiolipin peroxidation. In addition, a significant 4.3 fold increase in the maximal binding capacity (Bmax) of TSPO was found in NH4Cl-exposed cells. Surprisingly, western blot analysis and real-time PCR did not demonstrate changes in TSPO expression. We also found that neither NH4Cl nor glutamine (a metabolic product of enhanced NH4Cl levels) inhibited binding of the TSPO ligand [3H]PK 11195. Interestingly, we observed a bimodal effect of the TSPO ligands PK 11195, Ro5-4864, and FGIN-1-27 on the toxicity of NH4Cl; such that 1-100 nM concentrations of TSPO ligands were protective, while concentrations above 1 μM enhanced NH4Cl-induced cell death processes. In conclusion, TSPO takes part in a bimodal way in the lethal effects induced by NH4Cl in glial type cells.
Ammonium chloride, cell death, cell swelling, mitochondria, oxidative stress, 18 kDa Translocator Protein (TSPO), neuropathology.
Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Department of Molecular Pharmacology, Ephron Street, P.O. Box 9649, Bat-Galim, Haifa 31096, Israel;.