Inhibitors of N-linked glycosylation induce systemic acquired resistance in cucumber

Localized treatment of cucumber (Cucumis sativus L. cv. Wisonsin) cotyledons with inhibitors of N-glycosylation such as tunicamycin or amphomycin resulted in systemic acquired resistance in the first leaf to the fungal pathogen Colletotrichum lagenarium. Resistance was maximal as early as 2 days after application and best results were observed when the inhibitor was used at 100 μ . The same treatment also induced salicylic acid accumulation as well as the expression of chitinase and a PR1-like protein. The systemic effect is not caused by the transport of tunicamycin, since tunicamycin was not detected in the leaves. Within 2 h after application tunicamycin inhibited N-glycosylation, but not protein synthesis as indicated by labelling experiments. The amount of large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase decreased after tunicamycin treatment and after pathogen inoculation and the expression of BiP, a protein localized in the endoplasmic reticulum was enhanced. The activation of defense reactions seems to be dependent and sensitive to N-linked glycosylation.     

Development of a toxin-binding agent as a treatment for tunicaminyluracil toxicity: protection against tunicamycin poisoning of sheep

Objective To assess the ability of certain derivatives of beta-cyclodextrin to treat sheep affected by tunicaminyluracil toxicity, using tunicamycin poisoning as a model system.
Design Controlled treatment trial.
Animals One hundred and sixty Merino wethers were used in the studies.
Procedure Groups of sheep were experimentally poisoned with tunicamycin. Derivatives of beta-cyclodextrin, with or without magnesium sulphate and magnesium gluconate, were administered to treatment groups daily for 2 to 3 days. Treatment groups were compared with untreated groups in terms of survival.
Results A significant increase in survival was observed following treatment of tunicamycin-affected sheep with hydroxypropyl-beta-cyclodextrin (HPb -CD) and magnesium sulphate in solution (P < 0.05). In subsequent trials, formula tion of the cyclodextrin in the form of a magnesium gluconate gel suspension demonstrated significant protection (P < 0.01) and was equally as effective as the cyclodextrin in solution, but required half the frequency of administration, even when the treatment was not commenced until 24 h after the final toxin dose. Beta-cyclodextrin-epichlorohydrin copolymer also improved the survival rate. After toxin administration, the sheep lost significantly less weight if treatment with HPb -CD was commenced early (P < 0.001).
Conclusion Protection studies using these two beta-cyclodextrin derivatives suggest that they may be effective in increasing the survival of sheep poisoned by tunicamycin and warrant further testing in field outbreaks of annual ryegrass toxicity.     

Retinal photoreceptor damage produced in guinea pigs by tunicamycin

Corynetoxins, members of the tunicamycin group of antibiotics, produce a severe and frequently fatal neurological disorder in ruminant livestock, and guinea pigs are a useful model to study the pathology and pathogenesis of this disease. The aim of this study was to determine whether tunicamycin produced ocular damage in this species, which could have pharmacotherapeutic and diagnostic value. Four 8-week-old guinea pigs were treated with tunicamycin, and two control animals were given the drug vehicle only. Guinea pigs were injected subcutaneously with 400 μg/kg of tunicamycin, in dimethyl sulphoxide, and killed 48 h post-injection. The eyes were then examined by light microscopy. Immunohistochemistry for rhodopsin was also performed. The principal pathological finding was marked retinal photoreceptor damage, which was characterised by disruption and disorganisation of rods, sometimes progressing to necrosis and separation of the outer segment. The cytoplasm of some rods was focally distended by accumulated, proteinaceous material. Rhodopsin immunopositivity in injured rods was markedly diminished and associated with shrinkage and shortening of the injured rod's outer segment. Ocular pathology, in the form of reproducible and extensive retinal photoreceptor damage, was found in guinea pigs given tunicamycin, extending the range of species found to be susceptible to this toxic injury. The guinea pig could prove to be a good animal model to test potential therapeutic interventions, and as brain lesions are often minimal and liver pathology non-specific in intoxicated ruminants, any spontaneously arising ophthalmic injury found in these species could be diagnostically useful.     

猪肝星状细胞内质网应激模型的建立及对泛素化的影响

试验对衣霉素（tunicamycin,TM）处理猪肝星状细胞的浓度和培养时间进行筛选,以期成功构建内质网应激（endoplasmic reticulum stress,ERS）模型,并在此基础上探究ERS下猪肝星状细胞泛素化的变化。试验采用浓度为0、1、2、5、10和15 μg/mL的TM处理猪肝星状细胞,培养2、4、8、16、24和36 h。通过检测细胞抑制率对TM浓度和培养时间进行初筛;通过检测细胞周期及ERS标志基因和蛋白表达对TM浓度和培养时间进行终选,以确定是否成功构建ERS模型,同时,在ERS下检测猪肝星状细胞泛素化相关基因的表达变化。结果表明：由细胞抑制率检测结果初步确定TM浓度5 μg/mL、培养8或24 h后有可能出现ERS。5 μg/mL TM在培养8或24 h时,ERS标志基因表达均极显著上调（P < 0.01）。在培养8 h时,ERS标志蛋白中仅ATF4显著上调（P < 0.05）,细胞周期中仅G2/M期细胞比例显著下降（P < 0.05）;在培养24 h时,ERS标志蛋白均显著上调（P < 0.05）,细胞周期在G1期出现阻滞,并导致S期和G2/M期细胞比例极显著下降（P < 0.01）。以上结果说明,5 μg/mL TM培养24 h可成功构建细胞ERS模型。在ERS下,细胞泛素化相关基因UBA2和UBE2E的表达均极显著升高（P < 0.01）。综上,猪肝星状细胞经5 μg/mL TM处理24 h,可成功建立ERS模型,并启动泛素化机制。