Rotenone is a neurotoxin that is an active component of many pesticides which has been shown to induce Parkinsonism in animal models. We show that the cytotoxicity of exposure to nanomolar concentrations of rotenone in cultures of mature cerebellar granule neurons (CGN) in serum-free medium is not due to phagocytosis by glial contamination. A concentration as low as 5.65 ± 0.51 nM of rotenone was enough to trigger 50% cell death of mature CGN in culture after 12 h. The addition of serum proteins to the culture medium attenuated rotenone neurotoxicity, and this can account at least in part for the requirement of higher rotenone concentrations to elicit neuronal cytotoxicity reported in previous works. Creatine partial protection against CGN death promoted by 5 nM rotenone correlated with creatine protection against rotenone-induced mitochondrial depolarization and oxidative stress. Furthermore, creatine largely attenuated the early dysregulation of cytosolic Ca2+ concentration after acute rotenone treatment. Noteworthy, our results also revealed that the sustained alteration of Ca2+ homeostasis induced by rotenone takes place at the onset of the enhancement of intracellular oxidative stress and before mitochondrial depolarization, pointing out that cytosolic Ca2+ dysregulation is a very early event in the rotenone toxicity to CGN.
Keywords: Cerebellar granule neurons; Creatine; Intracellular calcium homeostasis; Mitochondrial depolarization; Oxidative stress; Rotenone.