Construction and eukaryotic expression of a recombinant plasmid encoding Pseudomonas aeruginosa toxA and typeⅢsecretion system pcrV / 医学研究生学报

Objective Exotoxin A ( encoded by gene toxA ) , one of the most toxic protein secreted by pseudomonas aerugi-nosa(P.a.), and PcrV (encoded by gene pcrV), key component to type Ⅲsecretion system of P.a., both matter significantly to the virulence of P.a.The article was to construct a novel DNA vaccine encoding a mutated toxA gene and the pcrV gene of P .a.and i-dentify gene expressions in eukaryotic cells . Methods The genes of toxA and pcrV were amplified by PCR , and the toxA gene was mutated to reduce the toxicity of Exotoxin A .Then gene fragments toxA m and pcrV were inserted into eukaryotic expression plasmid pIRES simultaneously to construct a recombinant DNA vaccine pIRES-toxAm-pcrV.The novel plasmid was transfected into HEK-293 cells by lipofectamine 2000 .The expressions of toxA m and pcrV were detected by Western blot . Results Gel electrophoresis demon-strated the target gene fragments encoding Exotoxin A and PcrV .Western blot exhibited proteins encoded toxA and pcrV expressed by HEK 293 cells. Conclusion The recombinant plasmid pIRES-toxAm-pcrV was successfully constructed .Western blot analysis indi-cated the expressions of toxA m and pcrV in HEK-293 cells.It may be used as a potential candidate of preventive vaccine of Pseudo-monas aeruginosa .

Pseudomonas aeruginosa Exotoxin A Reduces Chemoresistance of Oral Squamous Carcinoma Cell via Inhibition of Heat Shock Proteins 70 (HSP70)

PURPOSE: Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9). MATERIALS AND METHODS: The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis. RESULTS: While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint. CONCLUSION: Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

A novel VEGF16S-PE38 fusion gene for anti-angiogenic therapy in malignant glioma of nude mice model / 中华神经医学杂志

Objective To evaluate the anti-angiogenic effect of eukaryotic vector containing human VEGF 165 and truncated pseudomonas exotoxin A (PE38) fusion gene on malignant glioma in nude mice, and explore a novel anti-angiogenic therapy for cancer. Methods The models were established through hypodermic injection of human U251 glioma cells into the nude mice and randomly divided into untreated group, PBS group, pIRES2-EGFP group and pIRES2-VEGF165-PE38-EGFP group on the 9th day. H&E staining was performed to observe the morphological changes of the glioma tissues; SP immunohistochemistry was employed to detect the expression of GFAP, CD31 andPE; quantitative pathologic image analysis system was used to investigate the microvessel density (MVD) in the tumor tissues. Results At day 16, the pIRES2-VEGF165PE38-EGFP group showed significantly lower tumor volume of mice and significantly decreased MVD than the other three groups (P<0.05). Positive expression of PE was shown in the pIRES2-VEGF165PE38-EGFP group, but negative in the other three groups. Conclusion The expression products of VEGFJ65-PE38 fusion gene can obviously inhibit the growth and angiogenesis of U2S1 cells in nude mouse flank tumor models, suggesting that it may be a novel therapeutic approach for anti-angiogenic therapy of cancer.

Experimental Study on Target Cells of Pseudomonas aeroginosa Exotoxin A / 第三军医大学学报

Pseudomonas aeroginosa exotoxin A(PEA) was purified from the strain PA103 and labelled with Ⅰ~(125).Then autoradiographic tracing,histopathological observations with light and electron microscopes,and antiserum protestion test were carried out on inbred mice BALB/C.The results indicate that the liver is the target organ of PEA,and both the hepatocytes and kupffer cells the target cells,on which the severe damage may be responsible for the acute death of the toxicated animals.

Construction of recombinant plasmid of Pseudomonas aeruginosa exotoxin A and its secreting expression in E. coli / 解放军医学杂志

Objective To clone and to express the full-length Pseudomonas aeruginosa exotoxin A gene and to purify the expressed protein using affinity chromatography. Methods Exotoxin A gene was amplified from the recombinant plasmid pSK/PEA-T vector and subcloned into the pMAL-P2X vector. Then the recombinant plasmid pMAL- PEA was transformed to E.coli BL21. After induction with IPTG, the expressed protein was analyzed by SDS-PAGE and purified with affinity chromatography. Results The recombinants expressed the fusion protein at a level of about 20% of total cell proteins, and 80% of the fusion protein was secreted into the supernatant. Conclusion Successful expression and purification of PEA are of significance for in-depth study of the pathogenic mechanism of Pseudomonas aeruginosa and preparing immunotoxin.