Defining Mechanisms of Toxicity for Linoleic Acid Monoepoxides and Diols in Sf-21 Cells

• Published in: Chemical research in toxicology 2001-04, Vol.14 (4), p.431-437
• Main Authors: Moran, Jeffery H, Mon, Thetsu, Hendrickson, Tina L, Mitchell, Lex A, Grant, David F
• Format: Article
• Language: English
• Subjects: Animals; Cell Line; diols; epoxides; Epoxy Compounds - chemistry; Linoleic Acid - chemistry; Linoleic Acid - toxicity; Mitochondria - drug effects; Noctuidae; Oligomycins - pharmacology; Oxygen - metabolism; Oxygen Consumption - drug effects; Spodoptera; Spodoptera frugiperda
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/tx000200o

Linoleic acid monoepoxides have been correlated with many pathological conditions. Studies using insect cells derived from Spodoptera frugiperda (Sf-21 cells) have suggested that conversion of the epoxides to the diols is required for toxicity. However, more recent studies using rabbit renal proximal tubules have suggested that linoleic acid monoepoxides are direct mitochondrial toxins. To better understand these discrepancies, we compared the toxicity of these linoleic acid metabolites in Sf-21 cells using mitochondrial respiration as an end point. Linoleic acid (100 μM) and 12,13-epoxy-9-octadecenoic acid (12,13-EOA, 100 μM) increased the rate of oligomycin-insensitive respiration by approximately 3.5- and 3-fold, respectively, decreased the rate of oligomycin-sensitive respiration by approximately 52 and 68%, respectively, and had no effect on the integrity of the electron transport chain. These effects were concentration-dependent, occurred within 1 min, and recovered to basal levels within 45 min. 12,13-Dihydroxy-9-octadecenoic acid (12,13-DHOA, 100 μM) had no effect on oligomycin-insensitive respiration but decreased the rate of oligomycin-sensitive respiration and uncoupled respiration in a concentration-dependent manner. Approximately 79 and 68% of oligomycin-sensitive respiration and uncoupled respiration was inhibited by 12,13-DHOA (100 μM), respectively. These effects occurred within 1 min and were not reversible in 6 h. Effects similar to those induced by 12,13-DHOA (100 μM) were observed using 12,13-EOA (100 μM) in Sf-21 cells expressing human soluble epoxide hydrolase. These data suggest that in this Sf-21 model linoleic acid and linoleic monoepoxides have transient uncoupling effects, whereas the primary mechanism of toxicity for linoleic acid diols in this model is inhibition of the electron transport chain.