Evaluation of the cytotoxic and genotoxic effects by melamine and cyanuric acid co-exposure in human embryonic kidney 293 cells

The melamine and cyanuric acid (CA) complex has been suggested to cause the toxic effects observed in melamine-contaminated food or milk. However, the cytotoxic and genotoxic effects of co-exposure to melamine and CA are not fully clear. Therefore, the cytotoxic effects of melamine and CA were first examined by co‐exposure in human kidney 293 cells using the MTT assay. During a 24-h period for the three concentrations tested (0.5, 1, and 5 mg/mL), neither melamine nor CA alone showed significant toxic effects on 293 cells at 0.5 mg/mL, while higher concentrations led to decreased in cell viability. However, co-exposure to several combinations of melamine and CA [100:1, 10:1, 1:10, and 1:100 (v:v), at a final concentration of 0.5 mg/mL] did cause cytotoxicity with higher levels of CA leading to higher cytotoxicity. By contrast, while neither melamine nor CA alone induced phosphorylated-H2AX (γH2AX) foci formation, melamine and CA at a 100:1 ratio induced γH2AX foci 24 h post-treatment. The alkaline comet assay also revealed the presence of DNA damage following melamine and CA co-exposure. In vivo assay also revealed the presence of melamine-CA complex in the kidney. These data indicated that the cytotoxic and genotoxic effects of melamine and CA co-exposure differ from those of melamine or CA alone.

Preparation and Evaluation of Norcantharidin-encapsulated Liposomes Modified with a Novel CD19 Monoclonal Antibody 2E8 / 华中科技大学学报（医学）（英德文版）

In this study,norcanthridin(NCTD)-encapsulated liposomes were modified with a novel murine anti-human CD19 monoclonal antibody 2E8(2E8-NCTD-liposomes)and the targeting efficiency and specific cytotoxicity of 2E8-NCTD-liposomes to CD19+leukemia cells were evaluated.BALB/c mice were injected with 2E8 hybridoma cells to obtain 2E8 monoclonal antibody(mAb).NCTD-liposomes were prepared by using film dispersion method.2E8 mAbs were linked to NCTD-liposomes using post-incorporation technology.Flow cytometry showed that the targeting efficiency of purified 2E8 mAbs on CDI9+Nalm-6 cells was 99.93%.The purified 2E8 mAbs were conjugated with NCTD-liposomes to prepare 2E8-NCTD-liposomes whose targeting efficiency on CD19+Nalm-6 was also 95.82%.The average size of 2E8-NCTD-liposomes was 118.32 nm in diameter.HPLC showed that the encapsulation efficiency of NCTD was 46.51%.When the molar ratio of 2E8/MaI-PEG2000-DSPE reached 1:50,we obtained the liposomes with 9 2E8 molecules per liposome.The targeting efficiency of 2E8-NCTD-liposomes on CD19+leukemia cells was significantly higher than that on CD19-leukemia cells.Similarly,the targeting efficiency of the immunoliposomes was also higher than that of the NCTD-liposomes on CD 19+leukemia cells.Those results were consistent with those observed by laser scanning confocal microscopy.3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay demonstrated that 2E8-NCTD-liposomes specifically killed Nalm-6 cells in a dose-and time-dependent manner.The viability of Nalm-6 cells treated by 2E8-NCTD-liposomes was significantly lower than that of Molt-3cells and it was also significantly lower than that of Nalm-6 cells treated with the same concentration of NCTD-liposomes or free NCTD.We are led to concluded that 2E8 antigen can serve as a specific targeting molecule of B lineage hematopoietic malignancies for liposome targeting,and 2E8-NCTD-liposomes can be used as a new and effective means for the treatment of B lineage hematopoietic malignancies.

Effect of 2-(carboxyphenyl) retinamide and genistein on the formation of early lesions in 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

Aberrant crypt foci (ACF) are recognized as preneoplastic lesions for colon cancer, and ACF in rodents are widely used as an intermediate biomarker to predict tumorigenicity in the colon. However, a lack of correlations between the formation of ACF and the development of colonic tumors has been reported in several studies. For example, 2-(carboxyphenyl) retinamide (2-CPR) and genistein were reported to inhibit the carcinogen-induced formation of ACF, whereas both of them were later found to enhance colon tumorigenesis in rats treated with azoxymethane (AOM). Recently, we have identified b-catenin-accumulated crypts (BCAC) in the colon of rats shortly after administration of AOM, and provided evidence that these are independent early lesions of classical ACF, and BCAC might be direct precursors for colon cancers. In the present study, we performed a comparative analysis of the modifying effects of 2-CPR and genistein on 1,2-dimethylhydrazine (DMH)-induced BCAC and ACF in male F344 rats. Dietary administration of 2-CPR (315 ppm) significantly reduced the total number, multiplicity and size of ACF in DMH-exposed colonic mucosa, while genistein (250 ppm) had no significant effects on DMH-induced ACF formation. In contrast, both of 2-CPR and genistein significantly enhanced the multiplicity and size of DMH-induced BCAC when compared with DMH alone group. In addition, both 2-CPR and genistein significantly increased the proliferating cell nuclear antigen (PCNA) index preferentially in BCAC. Together with previous findings that 2-CPR and genistein are tumor promoters in the colon, our results support the concept that BCAC are precursors of colon tumors and suggest that these lesions are more reliable short-term biomarkers for colon carcinogenesis in rodents than ACF.