Organic Solvent-Induced Cell Death in Rat Cerebellar Granule Cells: Structure Dependence of C10 Hydrocarbons and Relationship to Reactive Oxygen Species Formation

Previously, increased formation of reactive oxygen species (ROS) has been demonstrated in cultured rat cerebellar granule cells (CGCs) exposed to t-butylcyclohexane, n-decane, and n-butylbenzene (Dreiem et al. Relationship between lipophilicity of C6-10 hydrocarbon solvents and their ROS-inducing potency in rat cerebellar granule cells. Neurotoxicology 2002;23:701-9). In the present paper, we have studied the effects of these hydrocarbons on the viability of CGCs. Cell death was assessed by measurement of lactate dehydrogenase (LDH) release and trypan blue staining. t-Butylcyclohexane and n-butylbenzene induced cell death in rat CGCs in a time-dependent and concentration-dependent manner. In contrast, n-decane did not cause release of LDH from rat CGCs even at 1 mM. Morphological studies revealed apoptotic morphology characterized by cell shrinkage and chromatin condensation after exposure to low concentrations of t-butylcyclohexane and n-butylbenzene. However, there was no internucleosomal DNA fragmentation and no protection by the pan-caspase inhibitor Boc-D-FMK or the protein synthesis inhibitor cycloheximide. This indicates that cell death after t-butylcyclohexane and n-butylbenzene exposure is an intermediate between classical apoptosis and necrosis. Treatment with the antioxidant α-tocopherol ameliorated hydrocarbon-induced cell death, indicating involvement of reactive oxygen species in the mechanism of hydrocarbon toxicity. The significance of ROS formation in relation to cell death is discussed.