Inactivation of the cytotoxic activity of repin, a sesquiterpene lactone from Centaurea repens.

This study examined how the toxic effects of a chemical compound called repin, found in certain species of the Centaurea plant, can be deactivated. The researchers found that the reaction of repin with glutathione, a naturally occurring antioxidant, can neutralize its toxicity, potentially shedding light on the mechanism of a deadly disorder in horses associated with prolonged ingestion of these plants.

Identification of Repin as a Contributing Agent in Equine Nigropallidal Encephalomalacia

• The researchers started by acknowledging the fatal neurodegenerative disorder equine nigropallidal encephalomalacia (ENE), known to affect horses that consume large quantities of Yellow Starthistle (Centaurea solstitialis) and Russian Knapweed (Centaurea repens).
• Through studying extracts from these Centaurea species on the PC12 cell line, they identified a chemical compound, sesquiterpene lactone (SQL) repin, as one of several potential contributors to the development of ENE.

Exploration of Repin-Induced Neurotoxicity Mechanism

• Repin’s neurotoxic impacts were investigated further to understand its molecular basis. The aim was to identify which functional groups of the molecule were contributing to the overall toxicity.
• It was found that repin becomes toxic when it reacts with glutathione (GSH), a natural antioxidant in the body, creating a GSH conjugate, which was not toxic when tested on the PC12 cell line.
• Furthermore, elimination of the alpha-methylenebutyrolactone double bond in repin resulted in a toxic-free derivative, which proved the essential role of this particular functional group for its toxicity.
• This derivative, referred to as analogue 2, did not decrease cellular dopamine levels in PC12 cells, unlike the parent compound repin.

Implication and Conclusions

• The results of this study suggest that the reaction of repin with glutathione, leading to the depletion of glutathione, may be a key event in the development of ENE.
• When GSH is depleted by repin, this could make the subject more vulnerable to oxidative damage, which links to neurodegenerative diseases.
• This study provides a better understanding of the molecular basis of repin-induced ENE and may lead to potential therapeutic approaches for preventing or treating this disorder in horses.