Biomarkers for ragwort poisoning in horses: identification of protein targets

One dimensional gel electrophoresis revealed a significant alteration in the equine plasma protein profile following pyrrole exposure and the formation of a high molecular weight protein aggregate. Using mass spectrometry and confirmation by western blotting the major components of this aggregate were identified as fibrinogen, serum albumin and transferrin.These findings demonstrate that pyrrolic metabolites can modify equine plasma proteins. The high molecular weight aggregate may result from extensive inter- and intra-molecular cross-linking of fibrinogen with the pyrrole. This model has the potential to form the basis of a novel proteomic strategy aimed at identifying surrogate protein biomarkers of ragwort exposure in horses and other livestock.Ragwort (Senecio jacobea) is a poisonous weed found growing on riverbanks, roadsides and pasture and is toxic to most grazing livestock. Horses are particularly sensitive to the toxic effects of ragwort and typically avoid the weed, but poisoning can occur when the animals graze on poorly maintained pastures or when feedstuff such as hay or silage is contaminated. Ragwort poisoning leads to complete liver failure, however the clinical signs can be slow to develop and may only manifest after prolonged dietary exposure. Prognosis is poor once the liver disease is advanced and current treatments are only palliative [1]. The early diagnosis of ragwort poisoning is extremely difficult as many conventional biochemical and histopathological indicators of the disease are non-specific and do not discriminate ragwort poisoning from other immune, infectious or toxic diseases [2].The toxic precursors in ragwort are pyrrolizidine alkaloids [3-5]. Amongst the most prominent pyrrolizidine alkaloids found in ragwort are jacobine, erucifoline and senecionine [6,7]. Following ingestion of ragwort the pyrrolizidine alkaloids are absorbed from the gastrointestinal tract and pass to the liver where they can be rapidly metabolised by the cytoc