The Mesoionic 1,3,4-thiadiazolium Derivative, MI-D, is a Potential Drug for Treating Glioblastoma by Impairing Mitochondrial Functions Linked to Energy Provision in Glioma Cells

Background: Mesoionic compound MI-D possesses important biological activities, such as antiinflammatory and antitumoral against melanoma and hepatocarcinoma. Glioblastoma is the most aggressive and common central nervous system tumor in adults. Currently, chemotherapies are not entirely effective, and the survival of patients diagnosed with glioblastoma is extremely short.

Objective: In this study, we aimed to evaluate the cytotoxicity of MI-D in noninvasive A172 glioblastoma cells and establish which changes in functions linked to energy provision are associated with this effect.

Methods: Cells A172 were cultured under glycolysis and phosphorylation oxidative conditions and evaluated: viability by the MTT method, oxygen consumption by high-resolution respirometry, levels of pyruvate, lactate, citrate, and ATP, and glutaminase and citrate synthase activities by spectrophotometric methods.

Results: Under glycolysis-dependent conditions, MI-D caused significant cytotoxic effects with impaired cell respiration, reducing the maximal capacity of the electron transport chain. However, A172 cells were more susceptible to MI-D effects under oxidative phosphorylation-dependent conditions. At the IC25, inhibition of basal and maximal respiration of A172 cells was observed, without stimulation of the glycolytic pathway or Krebs cycle, along with inhibition of the activity of glutaminase enzyme, resulting in a 30% ATP deficit. Additionally, independent of metabolic conditions, MI-D treatment induced cell death in A172 cells by apoptosis machinery/ processes.

Conclusion: The impairment of mitochondrial respiration by MI-D under the condition sustained by oxidative phosphorylation may enhance the cytotoxic effect on A172 glioma cells, although the mechanism of cell death relies on apoptosis.