Vero-toxin

A. Yamada, K. Hatano, K. Matsuoka, T. Koyama, Y. Esumi, H. Koshino, K. Hino, K. Nishikawa, Y. Natori, and D. Terunuma, Syntheses and Vero toxin-binding activities of carbosilane, Tetrahedron, 62 (2006) 5074—5083. 

These dendritic dumbbells bearing up to six galabiose units (Galal-4Gal) in the periphery could serve as artificial inhibitors of the Shiga toxin (Vero toxin). 

Scheme 5.52. Structure of vero-toxin recognized RNA sequence (left) and preparation of its peptidic mimetic (right) using LTA (L-threonine aldolase).

Endo, Y., Tsurugi, K., Yutsudo, T., Takeda, Y., Ogasawara, T. and Igarashi, K. (1988b) Site of action of a Vero toxin (VT2) from Escherichia coli O157 H7 and of Shiga toxin on eukaryotic ribosomes. RNA A-glycosidase activity of the toxins. Eur J Biochem, 171, 45-50. 

Nakata, K., Totsu, T, Tanaka, N., Akashi, T, and Kanega.saki, S. (1998). Inhibitory effects of macrolide antibiotics at low concentrations on vero toxin production by pathogenic E. coli 0157. Jpn. J. Antibiot. 51 (Suppl.), 146-150. 

The entry of CL into cells may be essential for the cellular entry [232] or secretion [233] of some macromolecules such as diphtheria toxin and modeccin. Sandvig and Olsnes [232] studied the entry of diphtheria toxin and modeccin into Vero cells in pH 7.2 media containing 20 mM Hepes, 1 mM Ca(OH)2, 5 mM glucose,a sufficient amount of mannitol to ensure isotonicity, and varying concentrations of NaCl. The cellular uptake of 0.1 nM diphtheria toxin at the end of 50 min was strongly dependent on CL concentration. It was 0% at 0 mM NaCl, 25% of the 140 mM NaCl control at 2 mM NaCl, and 60% of the control at 70 mM NaCl. A similar trend was observed for modeccin, i.e., no transport at 0 mM NaCl, 20% of control at 0.05 mM NaCl, 60% of control at 0.1 mM NaCl, 80% of control at 0.5 mM NaCl, and 100% of control at 2 mM NaCl. 

The use of CL-free media required 100 times higher concentrations of the toxins for any cellular uptake. Furthermore, the entry of both toxins was denied when Vero cells were incubated in normal medium with inhibitors of CL entry, including 4-acetamido-4 -isothiocyanostilbene-2,2 -disulfonate (SITS), pyridoxal... 

Umata T, Moriyama Y, Futai M, Mekada E. The cytotoxic action of diphtheria toxin and its degradation in intact Vero cells are inhibited by bafilo-mycin Al, a specific inhibitor of vacuolar-type H(+)-ATPase. J Biol Chem 1990 265(35) 21940-21945. 

Later, Suri Iyer et al. synthesized similar Gb3-AuNPs but with different length of linkers and surface glycan densities [66], They conducted luciferase assay to measure the toxin-mediated inhibition of protein synthesis and found that Gb3-AuNPs were nontoxic to Vero monkey kidney cells and protected Vero cells from Shiga toxin in a dose-dependent manner. 

Rao, EYE., Bhattacharya, R., Gupta, N., Farida, M.M., Bhaskar, A.S.B., and Dubey, R. 2002b. Involvement of caspase and reactive oxygen species in cyanobacterial toxin anatoxin-a-induced cytotoxicity and apoptosis in rat thymocytes and Vero cells. Archiv Toxicol 76, 227-235. 

More effective uptake of C3 has been achieved by making a fusion protein of C3 transferase with the subunit of diphtheria toxin involved in binding and transport across membranes (Aullo ef a/., 1993). Unfortunately this delivery system does not work for all cell types since mouse and rat cells do not bind diphtheria toxin. Vero cells appear to be the cells most sensitive to this construct (Aullo ef al., 1993 Boquet efal., 1995). 

Middlebrook JL, Dorland R B, Leppla SH (1978) Association of diphtheria toxin with Vero cells Demonstration of a receptor. J Biol Chem 253 7325-7330. 

Moskaug J0, Sandvig K, Olsnes S (1988) Low pH-induced release of diphtheria toxin A-fragment in Vero cells. Biochemical evidence for transfer to the cytosol. J Biol Chem 263 2518-2525. 

Olsnes S, Carvajal E, Sandvig K (1986) Interactions between diphtheria toxin entry and anion transport in Vero cells. III. Effect on toxin binding and anion transport of tumor-promoting phorbol esters, vanadate, fluoride and salicylate. J Biol Chem 261 1562-1569. 

Production of toxin chimeras is possible by applying similar technology to recombine isolated A- and B-chains from closely related type 2 RlPs (Olsnes and Pihl, 1986). For example, hybrid toxins composed of the modeccin A-chain and RTB have been produced and found to be even more toxic to Vero cells than are native ricin or modeccin (Sundan et al., 1983). Isolated abrin A-chain can be combined with RTB, or abrin B-chain with RTA, to produce chimeras with almost the same toxicity as the native toxins (Olsnes et al., 1974a). Similar experiments have been conducted combining viscumin A-chain and RTB to produce a chimera with cytotoxicity intermediate between that of viscumin and ricin (Tonevitskii et al., 1994). 

In 1982 in the USA, two outbreaks of severe colitis were associated with eating of nndercooked meat contaminated by E. coli 0157 H7 serotype (Riley et al. 1983). Strains of this serotype were found to produce a toxin similar to that of Shigella dysenteria the shiga-toxin also called verotoxin due to its cytotoxic activity on Vero cells (KarmaU et al. 1983). 

However, the presence of cytotoxicity in the extract could be due to other toxins or bacterial products, it is necessary to perform a neutralization assay with specific antisera to confirm that the cytopathic effect is due to the production of Shiga toxins. Moreover, in absence of neutralization assay, VGA lacks specificity (Rahn et al. 1996). Therefore, the Vero Cells assay have been largely supplanted by immunologically-based and DNA-based method for the detection of STEC, but is still used for confirmation of Shiga toxin production from pure cultures. 

Kehl KS, Havens P, Behnke CE, Acheson DW (1997) Evaluation of the premier EHEC assay for detection of Shiga toxin-producing Escherichia coli. J Clin Microbiol 35 2051-2054 Konowalchuk J, Speirs Jl, Stavric S (1977) Vero response to a cytotoxin of Escherichia coli. Infect Immun 18 775-779... 

Scotland SM, Smith HR, Rowe B (1985) Two distinct toxins active on Vero cells from Escherichia coli 0157. Lancet 2 885-886... 

Substantial inhibition of ribonucleic acid (RNA) synthesis (86% inhibition) by trichothecene myco-toxin was observed in human (HeLa) cells,47 but T-2 toxin had minor effects (15% inhibition) on RNA synthesis in Vero cells.46 The trichothecene myco-toxin-related inhibition of RNA synthesis is probably a secondary effect of the inhibition of protein synthesis. Scheduled DNA synthesis is strongly inhibited in various types of cells that are exposed to trichothecene mycotoxins. In mice or rats treated with trichothecene mycotoxins, DNA synthesis in all tissues studied was suppressed, although to a lesser degree than protein synthesis.49 The pattern by which DNA synthesis is inhibited by the trichothecene mycotoxins is consistent with the primary effect of these toxins on protein synthesis. In appropriate cell models, for the most part, trichothecene mycotoxins demonstrate neither mutagenic activity nor the capacity to damage DNA.50... 

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