Diethylene glycol and its metabolites induce cell death in SH-SY5Y neuronal cells in vitro.

Diethylene glycol (DEG) intoxication results in metabolic acidosis, renal and hepatic dysfunction, and late-stage neurotoxicity. Though the renal and hepatic toxicity of DEG and its metabolites 2-hydroxyethoxyacetic acid (2-HEAA) and diglycolic acid (DGA) have been well characterized, the resultant neurotoxicity has not. SH-SY5Y neuroblastoma cells were incubated with all 3 compounds at increasing concentrations for 24, 48, or 120 h. At all 3 time points, 50 mmol/L DGA and 100 mmol/L DEG showed significant Annexin V and propidium iodide (PI) staining with additional concentrations showing similar staining patterns at 24 h (100 mmol/L DGA) and 48 h (50 mmol/L DEG, 100 mmol/L DGA). Only the 200 mmol/L 2-HEAA concentration induced SH-SY5Y cell death. Interestingly at 24 and 48 h, 100 mmol/L DEG induced significant increases in apoptotic cell death markers, which progressed to necrosis at 120 h. Similar to DEG, 50 mmol/L DGA induced significant increases in SH-SY5Y cell apoptosis and necrosis markers at both 24 and 48 h. As expected, high DGA concentrations (100 mmol/L) at 120 h induced significant SH-SY5Y cell necrosis with no apoptosis detected. However, at 120 h lower DGA concentrations (20 mmol/L) significantly increased oligonucleosome formation alone and in combination with 2-HEAA or DEG. Taken together, these results indicate that DGA and DEG at threshold concentrations induce neurotoxicity in SH-SY5Y cells.