A histological, histochemical and biochemical study of the effect of the toxin of lupinosis on murine liver

Ustiloxin A inhibits proliferation of renal tubular epithelial cells in vitro and induces renal injury in mice by disrupting structure and respiratory function of mitochondria

Recently, we found that Ustiloxin A (UA, a mycotoxin) was widely detected in paddy environment and rice samples from several countries, and was also detected in human urine samples from China. However, the current knowledge about the health risks of UA are limited. In this research, the cytotoxicity of UA in mice renal tubular epithelial cells (mRTECs) was evaluated, and the results indicated that UA arrested cell cycle in G2/M phase via altering cellular morphology and microtubule, and inhibited the proliferation and division of mRTECs. Furthermore, UA could inhibit mitochondrial respiration via binding to the CoQ-binding site in dihydro-orotate dehydrogenase (DHODH) protein, and resulted in mitochondrial damage. These adverse effects of UA on mitochondria might be responsible for the cytotoxicity observed in vitro. In vivo, UA at concentrations that were comparable to the realistic concentrations of human exposure induced renal insufficiency in mice, and this might be associated with the renal mitochondrial damage in mice. However, exposure to UA at those realistic concentrations did not promote the progression from renal insufficiency to renal fibrosis and chronic kidney disease was not observed in mice.

Phomopsins: an overview of phytopathological and chemical aspects, toxicity, analysis and occurrence

Phomopsis leptostromiformis, and its teleomorph Diaporthe toxica, is a lupin pathogen that causes stem blight in young lupins and, as a saprophyte, has been detected on dead lupine material. Under favourable conditions, the fungus produces phomopsins (PHOs), a family of macrocyclic hexapeptide mycotoxins capable of binding tubulin through the tripeptide side chain. The toxic effects appear largely confined to the liver. In particular, the ingestion of PHO contaminated lupin stubble has been linked to lupinosis, a debilitating disease of sheep (the most sensitive animal) characterised by disorientation, blindness, lethargy, and eventually death. The chemical structures of PHO A, B and D have been identified. Analytical methods to determine PHOs are mainly enzyme-linked immunosorbent assays or chromatographic separations, in combination with ultraviolet and mass spectrometric detection. The data about the PHOs occurrence are limited to Australia, restricted to lupin seed. Only one survey has been carried out on lupin seeds and flours from the Swiss market. Not many strategies have been developed to limit lupin seed contamination. Efforts devoted to control lupinosis in Australia focused on the development of cultivars resistant to Phomopsis infection. There are few examples in literature of decontamination or detoxification of PHOs; moreover, they have been shown to be resistant to extensive processing, including cooking. Australia and New Zealand are the only countries that included PHOs in their mycotoxin regulations, with a limit of 5 µg/kg in lupin seeds and derived products. Phomopsins are poorly studied mycotoxins and risk assessment on PHOs has not been done at the European level. The collection of all available scientific data was requested by EFSA in a specific project and partners involved considered it of general interest preparing this review to highlight the limited available information, which indicate that the assessment of potential risk related to PHOs is currently not feasible.

"Lupinosis"-like lesions in mice caused by ustiloxin, produced by Ustilaginoieda virens: a morphological study

A crude toxin, obtained by methanol-extraction of a water extract of false smut balls (INA-KOUJI in Japanese) caused by Ustilaginoidea virens on rice panicles, was injected into mice intraperitoneally. Single injection of 100 or 200 mg/kg body weight of the extract was not lethal but caused acute, occasional necrosis of hepatocytes and renal tubular cells, followed by increased number of mitotic figures with occasional multinuclear giant cells. Erosions and ulceration of the forestomach and atrophy of the thymus were observed a week later. Repeated intraperitoneal injection of the crude toxin at the levels of 12 and 25 mg/kg body weight induced more severe necrosis of the liver and kidneys, with delayed occurrence of mitosis. Forestomach erosion also occurred. Serial injection for 10-12 days of either 3 or 6 mg/kg of the crude extract or 400 micrograms/kg of ustiloxin A, using the purified crystals, caused relatively mild but definite liver and kidney lesions similar to those described above. The lesions in the liver and kidney were quite similar to those observed in lupinosis caused by phomopsin A, a mycotoxin produced by Phomopsis leptostromiformis. Isolation of the toxic substance indicates that the contaminated rice panicles may cause toxicosis of cattle, although no field outbreaks have occurred yet.

Biliary hyperplasia and carcinogenesis in chronic liver damage induced in rats by phomopsin

Phomopsin, a hexapeptide mycotoxin contaminant of lupin plant and seed materials, was administered subcutaneously to adult rats at a daily dose rate of 30 micrograms/kg body weight (approximately 0.005 median lethal dose) for 2, 6 or 17 wks and the development of liver damage was observed during treatment and for up to 2 yr after. All rats injected for 17 wks developed permanent liver damage characterized by nodular cirrhosis and extensive biliary hyperplasia. Cholangiomas developed in 60% of these rats and cholangiocarcinomas and hepatocellular carcinomas in 13%. Similar effects were produced in some rats injected for 6 wks, while in others the cessation of treatment was followed by almost complete regression of the liver lesions. Livers damaged by 2 wks of injection had fully recovered within a few wks. The permanence of the liver damage is relevant to the management of stock exposed seasonally to the toxin, while its carcinogenic potential in rats, although not high, indicates the need for monitoring of the phomopsin content of lupin seed or flour prepared for human consumption.

The pathogenesis of lupinosis in the rat

The morphological, histochemical and biochemical changes in the liver of rats challenged with a single intraperitoneal injection of the toxin of lupinosis were investigated. The resulting injury is biphasic. The initial non-specific phase lasts for a few days, affects mainly the centrilobular region and is characterised by mitochondrial swelling, lipid accummulation and autophagosome formation. In addition, the hepatic concentrations of OCT, LDH, SDH, and AST fall while that for ALP increase. This is accompanied by a rise in the serum concentration of many of these enzymes. The second phase lasts longer and is characterised by phenomena indicative of abnormalities in hepatocytic division. Normal and abnormal metaphase as well as multinucleated hepatocytes falls. The possibility that the toxin of lupinosis interferes with microtubular units is considered.