Methodological considerations when using immortal cell lines as an in vitro model to investigate mitochondrial diseases, with respect to the malignant nature of these deviant cells.

Abstract

While the etiology of Parkinson's disease (PD) is multi-faceted, a foremost feature involves mitochondrial impairment. Likewise, mitochondrial toxins can trigger a sequence of events that mimic the biochemical and pathological features of PD. Hence, a common experimental model to study mitochondrial toxins in vitro is immortal cell lines. However, these cells are derived from malignant origin and have inherent biochemical metabolic features consistent with cancer, including a non-requirement for mitochondrial oxidative phosphorylation to derive energy from glucose. The data obtained in this study indicate that PC12 cells, SH-SY5Y and N2A neuroblastoma produce enormous amounts of lactic acid (in the absence of mitochondrial toxins), have a preference for anaerobic metabolism, a non-requirement for mitochondrial function, a preference for CO2 rather than O2 to metabolize glucose and an adverse reaction to substances that optimize aerobic mitochondrial respiration and / complex I/ IV function. In the presence of mitochondrial toxins or the absence of oxygen, these cells appear to survive indefinitely, unless depletion of glucose occurs via compensatory potentiated anaerobic glycolysis. In conclusion, glucose supply should always be controlled when examining the apoptotic effects of mitochondrial toxins in immortal cell lines in vitro. In addition, caution should be exercised in experimental design since the pathology of cancer and Parkinson's disease appear to be inversely relevant to mitochondrial activity. (Supported by NIH Grant NCRR 03020)