Cytotoxic activity of extracts from Hypochaeris radicata.

The research investigates the cytotoxic activity of extracts from Hypochaeris radicata, a plant associated with a nerve disorder in horses, particularly during drought conditions. The results suggest that drought stress in the plant could lead to increased production of toxins that cause the disease.

Understanding the Research

• The research focuses on a disease known as pasture-associated stringhalt in horses. This is a peripheral neuropathy, a condition resulting from damage to peripheral nerves, which causes an abnormal walking pattern due to hyperflexion of the pelvic limbs.
• The disease is often observed in horses during periods of drought, when they graze on pastures heavily infected with Hypochaeris radicata. The study, therefore, hypothesizes that H. radicata might produce neurotoxins under drought stress leading to the disease.

The Experimental Procedure

• The investigation procedures involve collecting exudates from H. radicata either exposed to stress (using copper chloride solution) or not. The extracts from these plants (stressed and unstressed) were then incubated with cultures of spinal cord and spinal ganglion derived from mice, as well as fibroblast cultures taken from newborn mouse tissues.
• The team observed the cytotoxicity in culture monolayers under a microscope and measured the release of lactate dehydrogenase, an enzyme which when detected at high levels, indicates damage to cells.
• They also used repin – a known plant-derived nerve toxin – as a positive control for comparison.

Key Findings of the Study

• The researchers observed significant dose-dependent cytotoxicity within 24 hours in all culture types when exposed to extracts from stressed plants (SE) or repin.
• The cytotoxic effect of extracts from stressed H. radicata was significantly greater than that from unstressed samples. The team further established that the cytotoxicity was not due to contamination with copper.
• This study confirms that H. radicata releases a cytotoxic substance when under stress, which is potentially responsible for causing the peripheral neuropathy condition in horses.

Study Implications

• This research sheds light on the likely cause of pasture-associated stringhalt in horses, which has been a long-standing puzzle. With this understanding, better prevention strategies and treatment options for the condition could potentially be developed.
• The revelation also alerts pastoralists about the dangers posed by the plant, especially during drought periods.