Effects of CMF and MET on glutamate and dopamine levels in the brain, and their impact on cognitive function

Chemotherapy can cause cognitive impairment in cancer survivors. CMF, the combination of cyclophosphamide (CYP), methotrexate (MTX), and 5-fluorouracil (5-FU), is employed for the treatment of several types of cancers, such as metastatic breast cancer. Metformin (MET) is an antidiabetic medication used to treat type 2 diabetes that can reportedly alleviate some toxic effects. In the current study, we investigated the ability of MET to alleviate the effects of CMF in neuronal toxicity.

Rats were treated with two doses of CMF (intraperitoneal injection) and MET (in the daily drinking water). Rats were subjected to fear conditioning memory tests to evaluate memory function following treatment, and brain samples were collected and homogenized using neuronal lysis buffer for assessment of glutamate and dopamine levels by high-performance liquid chromatography (HPLC).

Fear conditioning memory tests revealed a significant reduction in memory function in CMF and CMF+MET groups vs. controls, but no significant change in MET groups vs. controls was detected. Similarly, CMF and CMF+MET groups revealed a significant increase in glutamate and dopamine levels in the brain of MET, CMF, and MET+CMF groups vs. controls based on HPLC results. In addition, although glutamate and dopamine levels were increased, levels varied between groups, with highest levels in the CMF+MET group.

Our results demonstrate that cognitive impairment in CMF and CMF+MET groups could result from increased glutamate and dopamine levels in the brain, leading to brain toxicity and failure of MET to alleviate the toxic effects of CMF.