Trichothecenes are lipophilic and thus easily absorbed through the skin, gut, and pulmonary mucosa. They are metabolized mainly by cytochrome P-450 and trichothecene-specific carboxylesterase activity in the liver, although other tissues such as the kidney, spleen, and intestine also show some metabolic activity. Trichothecenes are metabolically transformed to less toxic metabolites by such reactions as hydrolysis, hydroxylation, de-epoxidation, and glucuronidation. Deoxynivalenol is metabolized mainly to the de-epoxy metabolite. Metabolites are excreted in the urine and feces. (L1910, L1949, A738)
Unlike many other mycotoxins, trichothecenes do not require metabolic activation to exert their biological activity, instead directly reacting with cellular components. Trichothecenes are cytotoxic to most eukaryotic cells due to their powerful ability to inhibit protein synthesis. They do this by freely moving across the plasma membrane and binding specifically to ribosomes with high-affinity. Specifically, they interfere with the active site of peptidyl transferase at the 3'-end of large 28S ribosomal RNA and inhibit the initiation, elongation or termination step of protein synthesis, as well as cause polyribosomal disaggregation. Protein synthesis is an essential function in all tissues, but tissues where cells are actively and rapidly growing and dividing are very susceptible to the toxins. Additionally, binding to ribosomes is thought to activate proteins in downstream signalling events related to immune response and apoptosis, such as mitogen-activated protein kinases. This is known as ribotoxic stress response. Trichothecenes may also induce some alterations in membrane structure, leading to increased lipid peroxidation and inhibition of electron transport activity in the mitochondria. They can further induce apoptosis through generation of reactive oxygen species. Further secondary effects of trichothecenes include inhibition of RNA and DNA synthesis, and also inhibition of mitosis. (L1948, L1949, A2962, A2963, A2964, A2980)
来源:Toxin and Toxin Target Database (T3DB)
毒理性
致癌物分类
3, 其对人类致癌性无法分类。
3, not classifiable as to its carcinogenicity to humans. (L135)
After direct dermal application or oral ingestion, the trichothecene mycotoxins can cause rapid irritation to the skin or intestinal mucosa, including skin irritation, burning and itching, rash or blisters, and bleeding. Eye contact can cause tearing, eye pain, conjunctivitis, burning sensations about the eyes, and blurred vision for up to 1 week. Symptoms also include nausea, vomiting, fatigue, dyspnea, and acute vascular effects leading to hypotension and shock. (L1948, L1949)
