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Wang X, Yu D, Chui L, Zhou T, Feng Y, Cao Y, Zhi S. A Comprehensive Review on Shiga Toxin Subtypes and Their Niche-Related Distribution Characteristics in Shiga-Toxin-Producing E. coli and Other Bacterial Hosts. Microorganisms 2024; 12:687. [PMID: 38674631 PMCID: PMC11052178 DOI: 10.3390/microorganisms12040687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 04/28/2024] Open
Abstract
Shiga toxin (Stx), the main virulence factor of Shiga-toxin-producing E. coli (STEC), was first discovered in Shigella dysenteriae strains. While several other bacterial species have since been reported to produce Stx, STEC poses the most significant risk to human health due to its widespread prevalence across various animal hosts that have close contact with human populations. Based on its biochemical and molecular characteristics, Shiga toxin can be grouped into two types, Stx1 and Stx2, among which a variety of variants and subtypes have been identified in various bacteria and host species. Interestingly, the different Stx subtypes appear to vary in their host distribution characteristics and in the severity of diseases that they are associated with. As such, this review provides a comprehensive overview on the bacterial species that have been recorded to possess stx genes to date, with a specific focus on the various Stx subtype variants discovered in STEC, their prevalence in certain host species, and their disease-related characteristics. This review provides a better understanding of the Stx subtypes and highlights the need for rapid and accurate approaches to toxin subtyping for the proper evaluation of the health risks associated with Shiga-toxin-related bacterial food contamination and human infections.
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Affiliation(s)
- Xuan Wang
- School of Public Health, Ningbo University, Ningbo 315000, China; (X.W.); (T.Z.); (Y.F.)
| | - Daniel Yu
- School of Public Health, Univeristy of Alberta, Edmonton, AB T6G 2R3, Canada;
| | - Linda Chui
- Alberta Precision Laboratories-ProvLab, Edmonton, AB T6G 2J2, Canada;
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 2B7, Canada
| | - Tiantian Zhou
- School of Public Health, Ningbo University, Ningbo 315000, China; (X.W.); (T.Z.); (Y.F.)
| | - Yu Feng
- School of Public Health, Ningbo University, Ningbo 315000, China; (X.W.); (T.Z.); (Y.F.)
| | - Yuhao Cao
- School of Basic Medical Sciences, Ningbo University, Ningbo 315000, China;
| | - Shuai Zhi
- School of Public Health, Ningbo University, Ningbo 315000, China; (X.W.); (T.Z.); (Y.F.)
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Oloomi M, Moazzezy N, Bouzari S. Protein kinase signaling by Shiga Toxin subunits. JOURNAL OF MEDICAL SIGNALS & SENSORS 2022; 12:57-63. [PMID: 35265466 PMCID: PMC8804587 DOI: 10.4103/jmss.jmss_79_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 02/24/2021] [Accepted: 06/14/2021] [Indexed: 11/17/2022]
Abstract
Background: Escherichia coli produces Shiga toxin (Stx), a pentamer composed of one A subunit and four B subunits. The B subunit of Stx (StxB) mediated the attachment of the holotoxin to the cell surface while the A subunit (StxA) has N-glycosidase activity, resulting in protein synthesis and cell death inhibition. Stx-induced cytotoxicity and apoptosis have been observed in various cell lines, although the signaling effectors are not precisely defined. Activated by protein kinases (PK), the signaling pathway in human tumors plays an oncogenic role. Tumor proliferation, survival, and metastasis are promoted by kinase receptors. In this regard, PK regulatory effects on the cellular constituents of the tumor microenvironment can affect immunosuppressive purposes. Methods: In this study, kinase inhibitors were used to evaluate the influence of Stx and its subunits on HeLa and Vero cells. Selective inhibitors of protein kinase C (PKC), CaM kinase (calmodulin kinase), protein kinase A (PKA), and protein kinase G (PKG) were used to compare the signaling activity of each subunit. Results: The ribotoxic activity in the target cells will lead to rapid protein synthesis inhibition and cell death in the mammalian host. The expression of Bcl2 family members was also assessed. Protein kinase signaling by Stx and its A and B subunits was induced by PKA, PKG, and PKC in HeLa cells. CaM kinase induction was significant in Vero cells. StxB significantly induced the pro-apoptotic Bax signaling factor in HeLa cells. Conclusion: The assessment of different signaling pathways utilized by Stx and its subunits could help in a better understanding of various cell death responses. The use of inhibitors can block cell damage and disease progression and create therapeutic compounds for targeted cancer therapy. Inhibition of these pathways is the primary clinical goal.
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Nowicki D, Krause K, Karczewska M, Szalewska-Pałasz A. Evaluation of the Anti-Shigellosis Activity of Dietary Isothiocyanates in Galleria mellonella Larvae. Nutrients 2021; 13:nu13113967. [PMID: 34836222 PMCID: PMC8625812 DOI: 10.3390/nu13113967] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 11/03/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Cruciferous vegetables, widely present in daily diets, are a rich source of organosulfur compounds with proven health benefits, especially chemopreventive or antioxidative effects. Isothiocyanate derivatives (ITCs) exhibit a broad spectrum of biological and pharmacological activity and recently, their antibacterial properties have been of particular importance. Here, we have focused on the anti-shigellosis activity of sulforaphane (SFN) and phenethyl ITC (PEITC). The genus Shigella causes gastroenteritis in humans, which constitutes a threat to public health. Production of a potent Stx toxin by S. dysenteriae type 1 results not only in more severe symptoms but also in serious sequela, including the hemolytic uremic syndrome. Here, we present evidence that two aliphatic and aromatic ITCs derivatives, SFN and PEITC, have an effective antibacterial potency against S. dysenteriae, also negatively regulating the stx gene expression. The molecular mechanism of this effect involves induction of the global stress-induced stringent response. ITCs also inhibit bacterial virulence against the Vero and HeLa cells. We present evidence for the therapeutic effect of sulforaphane and phenethyl ITC against a S. dysenteriae infection in the Galleria mellonella larvae model. Thus, our results indicate that isothiocyanates can be effectively used to combat dangerous bacterial infections.
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Plavec TV, Zahirović A, Zadravec P, Sabotič J, Berlec A. Lectin-Mediated Binding of Engineered Lactococcus lactis to Cancer Cells. Microorganisms 2021; 9:microorganisms9020223. [PMID: 33499141 PMCID: PMC7911926 DOI: 10.3390/microorganisms9020223] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/14/2021] [Accepted: 01/20/2021] [Indexed: 12/28/2022] Open
Abstract
Lectins have been increasingly utilized as carriers for targeted drug delivery based on their specific binding to glycans located on mammalian cells. This study employed two lectins, B subunit of bacterial Shiga holotoxin (Stx1B) and fungal Clitocybe nebularis lectin (CNL), for surface display on the lactic acid bacterium Lactococcus lactis. The specific adhesion of these engineered, lectin-displaying L. lactis to cancer cells was evaluated. The expression and surface display of both lectins on L. lactis were demonstrated by western blotting and flow cytometry, respectively. MTS assays revealed that recombinant Stx1B had no effect on Caco-2 cell viability at concentrations of ≤25 µg/mL, whereas CNL was non-toxic even at relatively high concentrations of ≤250 µg/mL. Stx1B bound to Caco-2, HT-29 and HeLa cells after 1 h of incubation. CNL bound to Caco-2 cells and recognized several glycoproteins in HT-29 and Caco-2 cell homogenates of which a 70 kDa protein predominated. Confocal microscopy revealed adhesion of Stx1B-displaying L. lactis to HeLa, Caco-2, and, to a lesser extent, HT-29 cells; CNL-displaying L. lactis showed a relatively similar level of adherence to HT-29 and Caco-2 cells. Thus, lectin-displaying L. lactis might serve as a carrier in targeted drug delivery when coupled to a therapeutic moiety.
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Affiliation(s)
- Tina Vida Plavec
- Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia; (T.V.P.); (A.Z.); (P.Z.); (J.S.)
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia
| | - Abida Zahirović
- Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia; (T.V.P.); (A.Z.); (P.Z.); (J.S.)
| | - Petra Zadravec
- Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia; (T.V.P.); (A.Z.); (P.Z.); (J.S.)
- Lek d.d., Kolodvorska 27, 1234 Mengeš, Slovenia
| | - Jerica Sabotič
- Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia; (T.V.P.); (A.Z.); (P.Z.); (J.S.)
| | - Aleš Berlec
- Department of Biotechnology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia; (T.V.P.); (A.Z.); (P.Z.); (J.S.)
- Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia
- Correspondence:
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Escobar-Chavarría O, Cossío-Bayúgar R, Ramírez-Noguera P, Prado-Ochoa MG, Velázquez-Sánchez AM, Muñoz-Guzmán MA, Angeles E, Alba-Hurtado F. In vivo and in vitro apoptosis induced by new acaricidal ethyl-carbamates in Rhipicephalus microplus. Ticks Tick Borne Dis 2020; 12:101603. [PMID: 33221619 DOI: 10.1016/j.ttbdis.2020.101603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 10/15/2020] [Accepted: 10/16/2020] [Indexed: 10/23/2022]
Abstract
The ability of ethyl-4-bromophenylcarbamate (LQM 919) and ethyl-4-chlorophenylcarbamate (LQM 996) to induce in vivo apoptosis of Rhipicephalus microplus ovarian cells and in vitro apoptosis of tick and mammalian cell culture was evaluated. The ovaries of engorged females treated with 1 mg mL-1 LQM 919 or LQM 996 presented more (p < 0.001) peroxidase-TUNEL-positive labeled cells (apoptotic cells) in situ than their respective control groups, and this increase was time-dependent (p < 0.001). The majority of apoptotic cells were observed in the epithelium and ovarian pedicel. HepG2, Vero and Rm-sus cells, as well as cells from primary cultures of R. microplus salivary glands, intestine and ovaries were exposed to different concentrations of the ethyl-carbamates. Both ethyl-carbamates induced a concentration-dependent reduction in the viability of all cell types (p < 0.001). Exposure to the ethyl-carbamates increased caspase 3 activity (p < 0.01) in primary cultures and cell lines, except in HepG2 cells. Fluorescent TUNEL-positive cells were observed in all cell types treated with 600 μM LQM 919 or LQM 996. These results indicate that both ethyl-carbamates induce apoptosis of the ovarian, intestinal and salivary glands cells in R. microplus and strongly suggest that this is their main mechanism of acaricidal action.
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Affiliation(s)
- O Escobar-Chavarría
- Programa de Doctorado en Ciencias de la Producción y de la Salud Animal, Universidad Nacional Autónoma de México, Mexico
| | - R Cossío-Bayúgar
- Centro Nacional de Investigaciones Disciplinarias en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias (INIFAP), Mexico
| | - P Ramírez-Noguera
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico
| | - M G Prado-Ochoa
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico
| | - A M Velázquez-Sánchez
- Laboratorio de Química Medicinal, Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico
| | - M A Muñoz-Guzmán
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico
| | - E Angeles
- Laboratorio de Química Medicinal, Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico
| | - F Alba-Hurtado
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Mexico.
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Anti-tumor activity of Escherichia coli Shiga toxin A subunit delivered by SF9 insect cells. J Pharmacol Sci 2018; 138:71-75. [PMID: 30293960 DOI: 10.1016/j.jphs.2018.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 09/04/2018] [Accepted: 09/06/2018] [Indexed: 01/01/2023] Open
Abstract
Cancer remains a major health problem around the world. A Shiga toxin is a bacterial toxin often produced by Shigella dysenteriae and Escherichia coli. A subunit of the Shiga toxin (StxA) is a cytotoxic agent which could be used to induce death in cancer cells. StxA expressed from baculovirus was evaluated in a pTriEx™ expression vector. The baculovirus vector was used for the A subunit delivery of StxA. StxA cell cytotoxicity was induced by the virus and assessed in the MCF7 and HeLa cell lines. In addition, the breast cancer cytotoxicity of the expressed StxA was also assessed in a cancer induced in mice. The cytotoxicity of the recombinant StxA baculovirus with different multiplicities of infection (MOI) was measured. The results showed that significant cytotoxicity can be induced on the mammalian epithelial breast cancer cell lines, MCF7 and HeLa cells with MOI ≥ 2. The results also showed that a malignant tumor induced by MCF7 could be inhibited in a mouse cancer model. Therefore, it can be concluded that StxA, expressed by baculovirus, could be used for in vitro and in vivo gene delivery. In this study StxA, delivered by the baculovirus inhibited cell proliferation, and eliminated HeLa and MCF7 cells, in vitro. In conclusion, this method can be used as a safe alternative for anticancer drug delivery inside cancer cells.
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Isothiocyanates as effective agents against enterohemorrhagic Escherichia coli: insight to the mode of action. Sci Rep 2016; 6:22263. [PMID: 26922906 PMCID: PMC4770323 DOI: 10.1038/srep22263] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 02/10/2016] [Indexed: 12/12/2022] Open
Abstract
Production of Shiga toxins by enterohemorrhagic Escherichia coli (EHEC) which is responsible for the pathogenicity of these strains, is strictly correlated with induction of lambdoid bacteriophages present in the host's genome, replication of phage DNA and expression of stx genes. Antibiotic treatment of EHEC infection may lead to induction of prophage into a lytic development, thus increasing the risk of severe complications. This, together with the spread of multi-drug resistance, increases the need for novel antimicrobial agents. We report here that isothiocyanates (ITC), plant secondary metabolites, such as sulforaphane (SFN), allyl isothiocyanate (AITC), benzyl isothiocynanate (BITC), phenyl isothiocyanate (PITC) and isopropyl isothiocyanate (IPRITC), inhibit bacterial growth and lytic development of stx-harboring prophages. The mechanism underlying the antimicrobial effect of ITCs involves the induction of global bacterial stress regulatory system, the stringent response. Its alarmone, guanosine penta/tetraphosphate ((p)ppGpp) affects major cellular processes, including nucleic acids synthesis, which leads to the efficient inhibition of both, prophage induction and toxin synthesis, abolishing in this way EHEC virulence for human and simian cells. Thus, ITCs could be considered as potential therapeutic agents in EHEC infections.
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Phenethyl isothiocyanate inhibits shiga toxin production in enterohemorrhagic Escherichia coli by stringent response induction. Antimicrob Agents Chemother 2014; 58:2304-15. [PMID: 24492371 DOI: 10.1128/aac.02515-13] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The pathogenicity of enterohemorrhagic Escherichia coli (EHEC) depends on production of Shiga toxins, which are encoded by stx genes located in the genomes of lambdoid prophages. Efficient expression of these genes requires prophage induction and lytic development of phages. Treatment of EHEC infections is problematic due to not only the resistance of various strains to antibiotics but also the fact that many antibiotics cause prophage induction, thus resulting in high-level expression of stx genes. Here we report that E. coli growth, Shiga toxin-converting phage development, and production of the toxin by EHEC are strongly inhibited by phenethyl isothiocyanate (PEITC). We demonstrate that PEITC induces the stringent response in E. coli that is mediated by massive production of a global regulator, guanosine tetraphosphate (ppGpp). The stringent response induction arises most probably from interactions of PEITC with amino acids and from amino acid deprivation-mediated activation of ppGpp synthesis. In mutants unable to synthesize ppGpp, development of Shiga toxin-converting phages and production of Shiga toxin are significantly enhanced. Therefore, ppGpp, which appears at high levels in bacterial cells after stimulation of its production by PEITC, is a negative regulator of EHEC virulence and at the same time efficiently inhibits bacterial growth. This is in contrast to stimulation of virulence of different bacteria by this nucleotide reported previously by others.
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Moazzezy N, Oloomi M, Bouzari S. Effect of shiga toxin and its subunits on cytokine induction in different cell lines. INTERNATIONAL JOURNAL OF MOLECULAR AND CELLULAR MEDICINE 2014; 3:108-17. [PMID: 25035861 PMCID: PMC4082813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/22/2014] [Accepted: 05/20/2014] [Indexed: 11/01/2022]
Abstract
Shiga toxins (Stxs) are bacterial virulence factors produced by Shigella dysenteriae serotype 1 and Escherichia coli strains. Stxs are critical factors for the development of diseases such as severe bloody diarrhea and hemolytic uremic syndrome. Additionally, Stxs trigger the secretion of pro- inflammatory cytokines and chemokines, particularly in monocytes or macrophages. The inflammatory cytokines result in the modulation of the immune system, local inflammations and enhancement of cytotoxicity. In this study, stimulation of the pro- inflammatory cytokines IL-1α, IL-1β, IL-6, IL-8, and TNF-α was assessed by recombinant Stx (rStx) and its subunits (rStxA and rStxB). Cytokines expression at mRNA level was investigated by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) method in HeLa cells and THP1 monocyte/ macrophage cell lines. After incubation with rStx and its recombinant subunits, the expression of IL-1α, IL- 6 and IL- 8 mRNAs was strongly induced in HeLa cells. In HeLa cells, low expression of IL-1α mRNA was shown by rStxB induction. Furthermore, the expression of IL-1α and IL-1β mRNAs in undifferentiated THP1 cells was only induced by rStx. In differentiated THP1 cells, rStx and its recombinant subunits elicited the expression of IL-1α, IL-1β, IL-8 and IL- 6 mRNAs. On the other hand, expression of TNF-α mRNA was only induced by rStx. Based on the data, the profile of cytokine induction in response to the rStx, and its subunits differs depending on the cell types.
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Affiliation(s)
- Neda Moazzezy
- Molecular Biology Unit, Pasteur Institute of Iran, Pasteur Ave. 13164 Tehran, Iran.
| | - Mana Oloomi
- Molecular Biology Unit, Pasteur Institute of Iran, Pasteur Ave. 13164 Tehran, Iran.,Corresponding author: Molecular Biology Unit, Pasteur Institute of Iran, Pasteur Ave. 13164, Tehran, Iran. E. mail:
| | - Saeid Bouzari
- Molecular Biology Unit, Pasteur Institute of Iran, Pasteur Ave. 13164 Tehran, Iran.
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Oloomi M, Bouzari S, Imani M, Akhtarian N. Construction of a Baculovirus vector containing A subunit of Shiga toxin for protein delivery. IRANIAN JOURNAL OF MICROBIOLOGY 2013; 5:350-5. [PMID: 25848504 PMCID: PMC4385160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND AND OBJECTIVES Baculovirus can be used as a vector in gene delivery system. Viral envelope of baculovirus would display expressed protein/peptide and it could render as a potential vaccine delivery system. In this regard, the gene coding for A subunit of shiga toxin (StxA) from Escherichia coli (E. coli) strain was cloned in a baculovirus expression system. StxA subunit has the ability to inhibit protein synthesis and this ability applied in cancer therapy. In this study, expression of StxA in baculovirus as a protein delivery system was assessed in vitro. MATERIAL AND METHODS StxA gene was cloned in pTriEx™ multisystem expression vector. This vector enables the protein expression in multisystem, E. coli and baculovirus. This construct was used to express the gene in E. coli and baculovirus. The construct containing StxA gene was made in baculovirus and expression was confirmed, then baculovirus expressing STXA transfect HeLa cells. RESULTS The expression of STXA peptide (32kDa) was confirmed by SDS-PAGE and western blotting in both expression systems. The A subunit challenge to human cell Lines was applied as a delivery system by baculoviruses. On the other hand, the inhibition of cell proliferation was also demonstrated by baculovirus containing STXA subunit. CONCLUSION STXA peptide expression in baculovirus was shown in E. coli and baculovirus expression system. Furthermore, it was shown that A subunit of Shiga toxin delivered by baculovirus can inhibit cell proliferation in HeLa cells and leading to cell death. Therefore, this prototype system could be a promising model for in vivo cancer therapy and targeted protein delivery system.
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Affiliation(s)
- Mana Oloomi
- Corresponding author: Saeid Bouzari Ph.D, Mana Oloomi Ph.D, Address: Molecular Biology Department, Pasteur Institute of Iran, Pasteur Ave. 13164. Tel.:+98-21-66953311-20, Fax: +98-21-66492619, , saeid
| | - Saeid Bouzari
- Corresponding author: Saeid Bouzari Ph.D, Mana Oloomi Ph.D, Address: Molecular Biology Department, Pasteur Institute of Iran, Pasteur Ave. 13164. Tel.:+98-21-66953311-20, Fax: +98-21-66492619, , saeid
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Pellarín MG, Albrecht C, Rojas MJ, Aguilar JJ, Konigheim BS, Paraje MG, Albesa I, Eraso AJ. Inhibition of cytotoxicity of Shiga toxin of Escherichia coli O157:H7 on vero cells by Prosopis alba Griseb (Fabaceae) and Ziziphus mistol Griseb (Rhamnaceae) extracts. J Food Prot 2013; 76:1733-9. [PMID: 24112573 DOI: 10.4315/0362-028x.jfp-13-087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The capacity of Prosopis alba Griseb. and Ziziphus mistol Griseb. fruit extracts to inhibit the toxic action of Shiga toxin (Stx) was investigated. Purification of Stx from Escherichia coli O157:H7 was performed by saline precipitation and affinity chromatography using a column with globotriaosylceramide, while the fruits were subjected to ethanolic or aqueous extractions. The protective action of both fruits was determined by pre-, co-, and postincubation of one 50% cytotoxic dose per ml of Stx with different concentrations of ethanolic and aqueous extracts in confluent monolayers of Vero cells for 72 h at 37°C (5% CO2). The inhibition of the cytotoxic effect of Stx by fruit extracts was determined by the neutral red vital staining technique. The extraction of the polyphenols and flavonoids was effective, and more polyphenols per milligram of dissolved solids were obtained from P. alba than from Z. mistol. However, there were more flavonoids in Z. mistol than in P. alba. Components of both fruits increased the viability of cells treated with Stx when the extracts were preincubated with Stx for 1 h before being applied to the cell cultures, with the ethanolic extract of P. alba showing 95% cell viability at a concentration of 2.45 mg/ml. The extracts were less effective in protecting cells when Stx, extracts, and cells were coincubated together without a previous incubation of Stx; only the concentrations of 19.46 mg/ml for the P. alba aqueous extract and 3.75 mg/ml for the Z. mistol ethanolic extract resulted in the inhibition of cytotoxicity, with 52 and 56% cell viability occurring, respectively. Investigation into this difference in the protection of cells indicated that the protein molecule of Stx suffered degradation to advanced oxidative protein products during preincubation with extracts, principally with P. alba, which exhibited a greater amount of nonflavonoid polyphenols than Z. mistol. The prooxidant action on Stx favored the cells and enhanced the protective action of both fruits.
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Affiliation(s)
- M G Pellarín
- Escuela de Nutrición, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Enrique Barros s/n, Ciudad Universitaria, Córdoba, Argentina;,
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