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Raj K. Puri - One of the best experts on this subject based on the ideXlab platform.
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interleukin 4 cytotoxin therapy synergizes with gemcitabine in a mouse model of pancreatic ductal adenocarcinoma
Cancer Research, 2007Co-Authors: Takeshi Shimamura, Mitomu Kioi, Syed R. Husain, Richard E Royal, Atsushi Nakajima, Raj K. PuriAbstract:Targeting cell surface receptors with cytotoxins or immunotoxins provides a unique opportunity for tumor therapy. Here, we show the efficacy of the combination therapy of gemcitabine with an interleukin-4 (IL-4) cytotoxin composed of IL-4 and truncated Pseudomonas exotoxin in animal models of pancreatic ductal adenocarcinoma (PDA). We have observed that 42 of 70 (60%) tumor samples from patients with PDA express moderate- to high-density surface IL-4 receptor (IL-4R), whereas normal pancreatic samples express no or low-density IL-4R. IL-4 cytotoxin was specifically and highly Cytotoxic [50% protein synthesis inhibition (IC50) ranging from >0.1 to 13 ng/mL] to six of eight pancreatic cancer cell lines, whereas no Cytotoxicity (IC50>1,000 ng/mL) was observed in normal human pancreatic duct epithelium cells, fibroblasts, and human umbilical vein endothelial cells (HUVEC). We also showed that IL-4 cytotoxin in combination with gemcitabine exhibited synergistic antitumor activity in vitro. To confirm synergistic antitumor activity in vivo and monitor precise real-time disease progression, we used a novel metastatic and orthotopic mouse model using green fluorescent protein-transfected cancer cells and whole-body imaging system. The combination of both agents caused complete eradication of tumors in 40% of nude mice with small established PDA tumors. In addition, combined treatment significantly prolonged the survival of nude mice bearing day 14 advanced distant metastatic PDA tumors. Similar results were observed in mice xenografted with PDA obtained from a patient undergoing surgical resection. These results indicate that IL-4 cytotoxin combined with gemcitabine may provide effective therapy for the treatment of patients with PDA.
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interleukin 13 receptor α2 chain
Cancer, 2006Co-Authors: Mitomu Kioi, Mariko Kawakami, Takeshi Shimamura, Syed R. Husain, Raj K. PuriAbstract:BACKGROUND Epithelial ovarian cancer demonstrates high mortality due to diagnosis at an advanced stage. In the search for a biomarker for early diagnosis and a target for therapy, the issue of whether interleukin-13 receptor (IL-13R), shown to be expressed on a variety of human cancers, is expressed in ovarian tumor samples was explored. In addition, whether this receptor serves as a biomarker and can be targeted by IL-13 cytotoxin was examined. METHODS IL-13R expression in 15 normal and 68 ovarian tumor tissue samples was determined by immunohistochemistry. Correlation between clinicopathologic features and IL-13R expression was analyzed. The efficacy of IL-13R-directed cytotoxin was determined in mice with subcutaneous, orthotopic, and peritoneal metastatic ovarian cancer. RESULTS Immunohistochemical analyses revealed that 83% of ovarian cancer specimens express IL-13Rα2, a high-affinity IL-13R subunit chain, whereas normal ovary samples expressed none or very low levels. The majority of clear cell ovarian carcinomas with the worst prognosis showed strong staining for IL-13Rα2. IL-13 cytotoxin was highly Cytotoxic to the IGROV-1 ovarian cancer cell line in vitro, and it mediated significant antitumor activity against a xenografted tumor model. The antitumor effects were confirmed by treating orthotopically implanted or peritoneal metastatic ovarian tumors, which showed significant extension of survival in immunodeficient mice. IL-13 cytotoxin also prevented cachexia in treated mice. The soluble form of IL-13Rα2 was detected in the serum of mice with peritoneal metastasis, and the level decreased to baseline in the treated group. CONCLUSIONS IL-13Rα2 is a promising target for ovarian cancer therapy, and the soluble form of IL-13R may be a possible surrogate marker for disease monitoring. Cancer. Published 2006 by the American Cancer Society.
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Interleukin-13 receptor-directed cytotoxin for malignant glioma therapy: from bench to bedside.
Journal of neuro-oncology, 2003Co-Authors: Syed R. Husain, Raj K. PuriAbstract:Central nervous system malignant neoplasias, in particular, glioblastoma multiforme (GBM) have defied all current therapeutic modalities. New therapies involving tumor targeting approach are being explored. This approach relies on the identification of unique or over-expressed cell surface receptors or antigens on tumor cells. In that regard, we have identified receptor for an immune regulatory cytokine, interleukin-13 (IL-13), which is over-expressed on human malignant glioma cell lines and primary tumor cell cultures. To target IL-13 receptors (IL-13R) for cancer therapy, we have developed a recombinant fusion protein composed of IL-13 and a mutated form of Pseudomonas exotoxin (IL13-PE38QQR or IL-13 cytotoxin). The IL-13 cytotoxin was found to be highly selective and potent in killing human GBM cells in vitro while normal cells including immune cells, endothelial cells and normal brain cells were generally spared the Cytotoxic effect of IL-13 cytotoxin. This is because these cells either expressed none or expressed low levels of IL-13R. Consistent with in vitro Cytotoxic activity, IL-13 cytotoxin mediated remarkable anti-tumor activity to human glioma in animal xenograft models. The direct injection of IL-13 cytotoxin into subcutaneous human GBM tumors grown in nude mice produced complete and durable regression of established tumors. Intravenous and intraperitoneal administration of IL-13 cytotoxin also reduced tumor burden significantly with fewer complete responders. All animals tolerated therapy well with minimal toxicity to vital organs. Pre-clinical safety and toxicity studies were performed in mice, rats and monkeys. Systemic administration of IL-13 cytotoxin appeared to be well tolerated at high doses (up to 50 microg/kg). Intrabrain parenchyma administration of IL-13 cytotoxin at doses up to 100 microg/ml was very well tolerated without any evidence of gross or microscopic necrosis, whereas at 500 microg/ml dose, localized necrosis was observed in normal rat brain. Based on these encouraging pre-clinical studies, three Phase I/II clinical trials in adults with malignant glioma have been initiated. The first clinical trial involves convection-enhanced delivery (CED) of IL-13 cytotoxin into recurrent malignant glioma. This route of IL-13 cytotoxin administration appears to be fairly well tolerated with no neurotoxicity. The second clinical trial involves infusion of IL-13 cytotoxin by CED following tumor resection. The initial stage of the second study assessed histologic effect of drug administered prior to resection. In third one, IL-13 cytotoxin is infused by CED followed by tumor resection. All three clinical trials are currently ongoing.
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Intratumor administration of interleukin 13 receptor-targeted cytotoxin induces apoptotic cell death in human malignant glioma tumor xenografts.
Molecular cancer therapeutics, 2002Co-Authors: Mariko Kawakami, Koji Kawakami, Raj K. PuriAbstract:Apoptosis is not only essential for homeostasis in normal cells but also in cancer cells, in which it is associated with cell death mechanisms caused by novel therapeutics. We have previously reported that interleukin-13 receptors (IL-13R) are constitutively overexpressed on a majority of human malignant glioma cell lines and primary cell cultures. In addition, we have reported that IL-13 cytotoxin, comprised of human IL-13 and a mutated form of Pseudomonas exotoxin, is highly and specifically Cytotoxic to these cells and can lead to pronounced antitumor activity in malignant glioma tumors in animal models. However, the molecular mechanisms of tumor Cytotoxicity induced by IL-13 cytotoxin are poorly understood. In this study, we demonstrate that glioma tumors undergo apoptotic cell death on intratumoral administration of IL-13 cytotoxin. This conclusion was made based on (a) time-dependent induction of several proapoptotic molecules, such as caspases (caspase-3, -8, and -9) in tumors; (b) cleavage of procaspase-3 and poly(ADP-ribose) polymerase (PARP); and (c) the release of cytochrome c from mitochondria to the cytosol on injection of IL-13 cytotoxin in U251 glioblastoma tumors established in immunodeficient animals. These indicators of two major pathways of apoptosis were detected in tumors even though IL-13 cytotoxin was no longer present in tumors. In addition, we found that inducible nitric oxide was expressed in tumors in a time-dependent manner with primary localization in infiltrating phagocytes after treatment with IL-13 cytotoxin. These studies demonstrate that IL-13 cytotoxin mediates apoptotic death of glioma cells, resulting in regression of established tumors. Our studies will help unravel the molecular pathways of cell death associated with tumor regression and provide additional insight and define apoptosis as possible surrogate marker of tumor response.
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suppression of an il 13 autocrine growth loop in a human hodgkin reed sternberg tumor cell line by a novel il 13 antagonist
Cellular Immunology, 2001Co-Authors: Yasuo Oshima, Raj K. PuriAbstract:Abstract IL-13 has been proposed to be an autocrine growth factor for Hodgkin/Reed-Sternberg tumor cells (H/RS cells). Since we have recently identified and produced a novel IL-13 antagonist (IL-13E13K) that can suppress the biological activity of IL-13, here we examined whether IL-13E13K can inhibit growth of Hodgkin lymphoma (HL)-derived cell lines. IL-13E13K not only inhibited the growth of an unstimulated H/RS cell line (L1236) but also cells that were stimulated by exogenous IL-13 in a dose-dependent manner. Several HL-derived cell lines expressed IL-13 message and protein and message for various chains of IL-13R. H/RS cell lines expressed mRNA for the IL-13Rα1, IL-4Rα, and IL-2Rγ chains. However, none of these cell lines expressed the IL-13Rα2 chain. An H/RS cell line (L1236) internalized the ligand–receptor complex after binding to a fusion protein composed of IL-13 and a mutated form of Pseudomonas exotoxin A (IL-13-PE38QQR, or IL-13 cytotoxin), as IL-13 cytotoxin was specifically Cytotoxic to H/RS cells in vitro. These results indicate that IL-13E13K and IL-13 cytotoxin can effectively suppress growth of a L1236 H/RS cell line. Therefore, additional studies should be performed to determine the expression of IL-13 and IL-13R in primary clinical samples of Hodgkin's lymphoma and both agents should be further tested in vitro and in vivo as possible therapeutic agents for HL.
Herbert Schmidt - One of the best experts on this subject based on the ideXlab platform.
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subtilase contributes to the Cytotoxicity of a shiga toxin producing escherichia coli strain encoding three different toxins
International Journal of Food Microbiology, 2016Co-Authors: Elisabeth Hauser, Joschua Funk, Matthias Bruederle, Carolin Reich, Annette Bruckbauer, Herbert SchmidtAbstract:Food-borne Shiga toxin-producing Escherichia coli (STEC) O113:H21 strain TS18/08, that has previously been isolated from mixed minced meat, harbors the Shiga toxin (Stx) encoding allele stx2a, the plasmid-located subtilase cytotoxin encoding allele subAB1 and the cytolethal distending toxin type V encoding gene cdt-V. In the current study, it could be shown that each of these toxin genes was transcribed with different transcription levels at different time points by RT real time PCR under laboratory batch conditions in LB-broth. The transcription maximum for cdt-V and subAB1 was observed after 3h while stx2a transcription was highest after 6h of incubation. During this time the mean relationship of the amount of stx2a:subAB1:cdt-V transcripts was 1:26:100. Furthermore, isogenic stx2a and cdt-V chromosomal deletion mutants were constructed to measure the contribution of SubAB1 to the overall Cytotoxicity of this strain. In this context, a further copy of stx2 was detected in this strain and was also deleted. Comparing the Cytotoxicity of supernatants of the resulting mutant strains TS18/08-3 (Δstx2-1Δstx2-2Δcdt-V) and TS18/08-4 (Δstx2-1Δstx2-2Δcdt-VΔsubAB1) on Vero cells demonstrated a contribution of SubAB1 to the overall Cytotoxic effect while the 4-fold isogenic deletion mutant did not show any Cytotoxic effect and that was comparable to the non-toxic laboratory E. coli strain C600. The Cytotoxic effect could be restored by complementation with the recombinant low copy plasmid pWSK29 harboring subAB1 under the control of its own promoter. In addition, the Cytotoxicity of wild type strain TS18/08 to Vero cells was in the same range as the EHEC O157:H7 strain EDL933. Therefore, food-borne STEC O113:H21 strain TS18/08 can be considered as a putative human pathogen.
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Cytotoxic and apoptotic effects of recombinant subtilase cytotoxin variants of shiga toxin producing escherichia coli
Infection and Immunity, 2015Co-Authors: Joschua Funk, N Biber, M Schneider, Elisabeth Hauser, Stefanie Enzenmuller, C Fortsch, Holger Barth, Herbert SchmidtAbstract:ABSTRACT In this study, the Cytotoxicity of the recently described subtilase variant SubAB 2-2 of Shiga toxin-producing Escherichia coli was determined and compared to the plasmid-encoded SubAB 1 and the chromosome-encoded SubAB 2-1 variant. The genes for the respective enzymatic active (A) subunits and binding (B) subunits of the subtilase toxins were amplified and cloned. The recombinant toxin subunits were expressed and purified. Their Cytotoxicity on Vero cells was measured for the single A and B subunits, as well as for mixtures of both, to analyze whether hybrids with toxic activity can be identified. The results demonstrated that all three SubAB variants are toxic for Vero cells. However, the values for the 50% Cytotoxic dose (CD 50 ) differ for the individual variants. Highest Cytotoxicity was shown for SubAB 1 . Moreover, hybrids of subunits from different subtilase toxins can be obtained which cause substantial Cytotoxicity to Vero cells after mixing the A and B subunits prior to application to the cells, which is characteristic for binary toxins. Furthermore, higher concentrations of the enzymatic subunit SubA 1 exhibited Cytotoxic effects in the absence of the respective B 1 subunit. A more detailed investigation in the human HeLa cell line revealed that SubA 1 alone induced apoptosis, while the B 1 subunit alone did not induce cell death.
Adrienne W Paton - One of the best experts on this subject based on the ideXlab platform.
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ouabain protects human renal cells against the Cytotoxic effects of shiga toxin type 2 and subtilase cytotoxin
Toxins, 2017Co-Authors: Maria Marta Amaral, Adrienne W Paton, James C. Paton, Horacio A Repetto, Magali Celeste Girard, Romina Soledad Alvarez, Flavia Sacerdoti, Cristina IbarraAbstract:Hemolytic uremic syndrome (HUS) is one of the most common causes of acute renal failure in children. The majority of cases are associated with Shiga toxin (Stx)-producing Escherichia coli (STEC). In Argentina, HUS is endemic and presents the highest incidence rate in the world. STEC strains expressing Stx type 2 (Stx2) are responsible for the most severe cases of this pathology. Subtilase cytotoxin (SubAB) is another STEC virulence factor that may contribute to HUS pathogenesis. To date, neither a licensed vaccine nor effective therapy for HUS is available for humans. Considering that Ouabain (OUA) may prevent the apoptosis process, in this study we evaluated if OUA is able to avoid the damage caused by Stx2 and SubAB on human glomerular endothelial cells (HGEC) and the human proximal tubule epithelial cell (HK-2) line. HGEC and HK-2 were pretreated with OUA and then incubated with the toxins. OUA protected the HGEC viability from Stx2 and SubAB Cytotoxic effects, and also prevented the HK-2 viability from Stx2 effects. The protective action of OUA on HGEC and HK-2 was associated with a decrease in apoptosis and an increase in cell proliferation. Our data provide evidence that OUA could be considered as a therapeutic strategy to avoid the renal damage that precedes HUS.
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systemic effects of subtilase cytotoxin produced by escherichia coli o113 h21
Toxicon, 2017Co-Authors: Abril E Seyahian, Adrienne W Paton, James C. Paton, Gisela Oltra, Federico Ochoa, Santiago Melendi, Ricardo Hermes, Nestor Lago, Mauricio Castro Parodi, Alicia E DamianoAbstract:Abstract Subtilase cytotoxin (SubAB) is a member of the AB 5 cytotoxin family and is produced by certain strains of Shiga toxigenic Escherichia coli . The toxin is known to be lethal to mice, but the pathological mechanisms that contribute to Uremic Hemolytic Syndrome (HUS) are poorly understood. In this study we show that intraperitoneal injection of a sublethal dose of SubAB in rats triggers a systemic response, with ascitic fluid accumulation, heart hypertrophy and damage to the liver, colon and kidney. SubAB treated rats presented microalbuminuria 20 days post inoculation. At this time we found disruption of the glomerular filtration barrier and alteration of the protein reabsorption mechanisms of the proximal tubule. In the kidney, SubAB also triggered an epithelial to mesenchymal transition (Wuyts et al., 1996). These findings indicate that apart from direct Cytotoxic effects on renal tissues, SubAB causes significant damage to the other organs, with potential consequences for HUS pathogenesis. Importance Uremic Hemolytic Syndrome is an endemic disease in Argentina, with over 400 hundred new cases each year. We have previously described renal effects of Shiga Toxin and its ability to alter renal protein handling. Bearing in mind that Subtilase Cytotoxin is an emerging pathogenic factor, that it is not routinely searched for in patients with HUS, and that to the date its systemic effects have not been fully clarified we decided to study both its systemic effects, and its renal effects to assess whether SubAB could be contributing to pathology seen in children.
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effects of escherichia coli subtilase cytotoxin and shiga toxin 2 on primary cultures of human renal tubular epithelial cells
PLOS ONE, 2014Co-Authors: Laura B Marquez, Adrienne W Paton, James C. Paton, Natalia Velazquez, Horacio A Repetto, Cristina Ibarra, Claudia SilbersteinAbstract:Shiga toxin (Stx)-producing Escherichia coli (STEC) cause post-diarrhea Hemolytic Uremic Syndrome (HUS), which is the most common cause of acute renal failure in children in many parts of the world. Several non-O157 STEC strains also produce Subtilase cytotoxin (SubAB) that may contribute to HUS pathogenesis. The aim of the present work was to examine the Cytotoxic effects of SubAB on primary cultures of human cortical renal tubular epithelial cells (HRTEC) and compare its effects with those produced by Shiga toxin type 2 (Stx2), in order to evaluate their contribution to renal injury in HUS. For this purpose, cell viability, proliferation rate, and apoptosis were assayed on HRTEC incubated with SubAB and/or Stx2 toxins. SubAB significantly reduced cell viability and cell proliferation rate, as well as stimulating cell apoptosis in HRTEC cultures in a time dependent manner. However, HRTEC cultures were significantly more sensitive to the Cytotoxic effects of Stx2 than those produced by SubAB. No synergism was observed when HRTEC were co-incubated with both SubAB and Stx2. When HRTEC were incubated with the inactive SubAA272B toxin, results were similar to those in untreated control cells. Similar stimulation of apoptosis was observed in Vero cells incubated with SubAB or/and Stx2, compared to HRTEC. In conclusion, primary cultures of HRTEC are significantly sensitive to the Cytotoxic effects of SubAB, although, in a lesser extent compared to Stx2.
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clathrin dependent trafficking of subtilase cytotoxin a novel ab5 toxin that targets the endoplasmic reticulum chaperone bip
Cellular Microbiology, 2008Co-Authors: Damien C Chong, Cheleste M Thorpe, James C. Paton, Adrienne W PatonAbstract:Subtilase cytotoxin (SubAB) is the prototype of a new family of AB5 cytotoxins produced by Shiga toxigenic Escherichia coli. Its Cytotoxic activity is due to its capacity to enter cells and specifically cleave the endoplasmic reticulum (ER) chaperone BiP. However, its trafficking within target cells has not been investigated previously. In Vero cells, fluorescence colocalization with subcellular markers established that SubAB is trafficked from the cell surface to the ER via a retrograde pathway similar, but not identical, to those of Shiga toxin (Stx) and cholera toxin (Ctx), with their pathways converging at the Golgi. The clathrin inhibitor phenylarsine oxide prevented SubAB entry and BiP cleavage in SubAB-treated Vero, HeLa and N2A cells, while cholesterol depletion did not, demonstrating that, unlike either Stx or Ctx, SubAB internalization is exclusively clathrin-dependent.
James C. Paton - One of the best experts on this subject based on the ideXlab platform.
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ouabain protects human renal cells against the Cytotoxic effects of shiga toxin type 2 and subtilase cytotoxin
Toxins, 2017Co-Authors: Maria Marta Amaral, Adrienne W Paton, James C. Paton, Horacio A Repetto, Magali Celeste Girard, Romina Soledad Alvarez, Flavia Sacerdoti, Cristina IbarraAbstract:Hemolytic uremic syndrome (HUS) is one of the most common causes of acute renal failure in children. The majority of cases are associated with Shiga toxin (Stx)-producing Escherichia coli (STEC). In Argentina, HUS is endemic and presents the highest incidence rate in the world. STEC strains expressing Stx type 2 (Stx2) are responsible for the most severe cases of this pathology. Subtilase cytotoxin (SubAB) is another STEC virulence factor that may contribute to HUS pathogenesis. To date, neither a licensed vaccine nor effective therapy for HUS is available for humans. Considering that Ouabain (OUA) may prevent the apoptosis process, in this study we evaluated if OUA is able to avoid the damage caused by Stx2 and SubAB on human glomerular endothelial cells (HGEC) and the human proximal tubule epithelial cell (HK-2) line. HGEC and HK-2 were pretreated with OUA and then incubated with the toxins. OUA protected the HGEC viability from Stx2 and SubAB Cytotoxic effects, and also prevented the HK-2 viability from Stx2 effects. The protective action of OUA on HGEC and HK-2 was associated with a decrease in apoptosis and an increase in cell proliferation. Our data provide evidence that OUA could be considered as a therapeutic strategy to avoid the renal damage that precedes HUS.
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systemic effects of subtilase cytotoxin produced by escherichia coli o113 h21
Toxicon, 2017Co-Authors: Abril E Seyahian, Adrienne W Paton, James C. Paton, Gisela Oltra, Federico Ochoa, Santiago Melendi, Ricardo Hermes, Nestor Lago, Mauricio Castro Parodi, Alicia E DamianoAbstract:Abstract Subtilase cytotoxin (SubAB) is a member of the AB 5 cytotoxin family and is produced by certain strains of Shiga toxigenic Escherichia coli . The toxin is known to be lethal to mice, but the pathological mechanisms that contribute to Uremic Hemolytic Syndrome (HUS) are poorly understood. In this study we show that intraperitoneal injection of a sublethal dose of SubAB in rats triggers a systemic response, with ascitic fluid accumulation, heart hypertrophy and damage to the liver, colon and kidney. SubAB treated rats presented microalbuminuria 20 days post inoculation. At this time we found disruption of the glomerular filtration barrier and alteration of the protein reabsorption mechanisms of the proximal tubule. In the kidney, SubAB also triggered an epithelial to mesenchymal transition (Wuyts et al., 1996). These findings indicate that apart from direct Cytotoxic effects on renal tissues, SubAB causes significant damage to the other organs, with potential consequences for HUS pathogenesis. Importance Uremic Hemolytic Syndrome is an endemic disease in Argentina, with over 400 hundred new cases each year. We have previously described renal effects of Shiga Toxin and its ability to alter renal protein handling. Bearing in mind that Subtilase Cytotoxin is an emerging pathogenic factor, that it is not routinely searched for in patients with HUS, and that to the date its systemic effects have not been fully clarified we decided to study both its systemic effects, and its renal effects to assess whether SubAB could be contributing to pathology seen in children.
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effects of escherichia coli subtilase cytotoxin and shiga toxin 2 on primary cultures of human renal tubular epithelial cells
PLOS ONE, 2014Co-Authors: Laura B Marquez, Adrienne W Paton, James C. Paton, Natalia Velazquez, Horacio A Repetto, Cristina Ibarra, Claudia SilbersteinAbstract:Shiga toxin (Stx)-producing Escherichia coli (STEC) cause post-diarrhea Hemolytic Uremic Syndrome (HUS), which is the most common cause of acute renal failure in children in many parts of the world. Several non-O157 STEC strains also produce Subtilase cytotoxin (SubAB) that may contribute to HUS pathogenesis. The aim of the present work was to examine the Cytotoxic effects of SubAB on primary cultures of human cortical renal tubular epithelial cells (HRTEC) and compare its effects with those produced by Shiga toxin type 2 (Stx2), in order to evaluate their contribution to renal injury in HUS. For this purpose, cell viability, proliferation rate, and apoptosis were assayed on HRTEC incubated with SubAB and/or Stx2 toxins. SubAB significantly reduced cell viability and cell proliferation rate, as well as stimulating cell apoptosis in HRTEC cultures in a time dependent manner. However, HRTEC cultures were significantly more sensitive to the Cytotoxic effects of Stx2 than those produced by SubAB. No synergism was observed when HRTEC were co-incubated with both SubAB and Stx2. When HRTEC were incubated with the inactive SubAA272B toxin, results were similar to those in untreated control cells. Similar stimulation of apoptosis was observed in Vero cells incubated with SubAB or/and Stx2, compared to HRTEC. In conclusion, primary cultures of HRTEC are significantly sensitive to the Cytotoxic effects of SubAB, although, in a lesser extent compared to Stx2.
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clathrin dependent trafficking of subtilase cytotoxin a novel ab5 toxin that targets the endoplasmic reticulum chaperone bip
Cellular Microbiology, 2008Co-Authors: Damien C Chong, Cheleste M Thorpe, James C. Paton, Adrienne W PatonAbstract:Subtilase cytotoxin (SubAB) is the prototype of a new family of AB5 cytotoxins produced by Shiga toxigenic Escherichia coli. Its Cytotoxic activity is due to its capacity to enter cells and specifically cleave the endoplasmic reticulum (ER) chaperone BiP. However, its trafficking within target cells has not been investigated previously. In Vero cells, fluorescence colocalization with subcellular markers established that SubAB is trafficked from the cell surface to the ER via a retrograde pathway similar, but not identical, to those of Shiga toxin (Stx) and cholera toxin (Ctx), with their pathways converging at the Golgi. The clathrin inhibitor phenylarsine oxide prevented SubAB entry and BiP cleavage in SubAB-treated Vero, HeLa and N2A cells, while cholesterol depletion did not, demonstrating that, unlike either Stx or Ctx, SubAB internalization is exclusively clathrin-dependent.
Dario Neri - One of the best experts on this subject based on the ideXlab platform.
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Antibody-Drug Conjugates and Small Molecule-Drug Conjugates: Opportunities and Challenges for the Development of Selective Anticancer Cytotoxic Agents
Journal of Medicinal Chemistry, 2015Co-Authors: Giulio Casi, Dario NeriAbstract:Conventional cancer chemotherapy heavily relies on the use of Cytotoxic agents, which typically do not preferentially localize at the tumor site and cause toxicity to normal organs, preventing dose escalation to therapeutically active regimens. In principle, antibodies and other ligands could be used for the selective pharmacodelivery of Cytotoxic agents to the neoplastic mass. For many years, the availability of ligands, capable of selective internalization into tumor cells, has been considered to be an essential requirement for the development of targeted Cytotoxics. This assumption, however, has recently been challenged on the basis of therapeutic data obtained with noninternalizing drug conjugates. Moreover, quantitative evaluations of the tumor targeting properties of antibodies and of small organic ligands have provided new insights for the implementation of optimal strategies for the development of targeted Cytotoxics. In this article, we highlight opportunities and challenges associated with the c...
