A Study of the Potential of the Pig as a Model for the Vaginal Irritancy of Benzalkonium Chloride in Comparison to the Nonirritant Microbicide PHI-443 and the Spermicide Vanadocene Dithiocarbamate

A porcine model was established to test the mucosal toxicity potential of a thiophene thiourea (PHI-443)-based anti-HIV microbicide and a vanadocene-based spermicide, vanadocene dithiocarbamate (VDDTC) in comparison to benzalkonium chloride (BZK). Nine domestic pigs (Duroc) in nonestrus stage received a single intravaginal application of 2% BZK, 2% PHI-443, or 0.1% VDDTC-containing gel. At various times after gel application, cell differentials and levels of inflammatory cytokines (IL-1 β, IL-4, IL-6, IL-8, IL-10, IL-18, IFN- γ, and TNF- α) in cervicovaginal lavage (CVL) fluid were monitored by flow cytometry and ELISA, respectively. Eight pigs were exposed intravaginally to a gel with and without BZK or VDDTC for 4 consecutive days and vaginal tissues were scored histologically for inflammation using a new scoring system. Only CVL fluid from pigs exposed to BZK showed a significant increase of IL-1 β, IL-8, and also IL-18 production when compared to the controls, PHI-443 or VDDTC-treated groups. Maximum levels of BZK-induced IL-1 β (100-fold), IL-8 (2,500-fold), IL-18 (80-fold), and IFN- γ(10-fold) were found at 24 hours. In the in vivo porcine vaginal irritation model, increased levels of vaginal IL-1 β, IL-8, and IL-18 were associated with histological changes consistent with vaginal inflammation. These results demonstrate that key cervicovaginal inflammatory cytokines are useful in vivo biomarkers for predicting the mucosal toxicity potential of vaginal products in the physiologically relevant and sensitive porcine model.

Carcinogenicity classification of vanadium pentoxide and inorganic vanadium compounds, the NTP study of carcinogenicity of inhaled vanadium pentoxide, and vanadium chemistry

It is argued that, because of inherent weaknesses in design and procedure, the U.S. National Toxicology Program study of the carcinogenicity of inhaled vanadium pentoxide does not provide adequate evidence to support the classification by regulatory authorities of vanadium pentoxide as a Group 2B (possible) human carcinogen. The extension by one regulatory authority of the carcinogenicity classification for vanadium pentoxide to cover all vanadium compounds is also questioned. Such an extension implies that the toxic effect of some unknown vanadium species is more powerful than that of any oxygen species generated from the oxygen atoms in vanadium pentoxide, and that vanadium in any form can be converted in vivo to an undefined toxic species. There is no experimental or theoretical basis supporting this hypothesis. For oxygen-containing compounds like vanadium pentoxide, there is a need for some form of toxicity classification related to their oxygen content since it is likely to be the most reactive component of such compounds. For all particulates, such as those of crystalline vanadium pentoxide, the special toxicity of particulates, and especially nanoparticles, also needs separate consideration and classification.

The permeability and cytotoxicity of insulin-mimetic vanadium compounds

PURPOSE

The aim of this study was to investigate the mechanism of permeation and cytotoxicity of vanadium compounds, [VO(acac)2], [VO(ma)2], and vanadate.

METHODS

Absorptive transport were carried out in Caco-2 monolayers grown on transwell inserts. Vanadium was quantified using inductively coupled plasma atomic emission spectrometry (ICP-AES). The change of Caco-2 cells in the microvilli morphology and F-actin structure was visualized by transmission electron microscopy and confocal laser scanning microscopy.

RESULTS

The three vanadium compounds were taken up by Caco-2 cells via simple passive diffusion. [VO(acac)2] were mainly transcellularly transported and exhibited the highest apparent permeabilty coefficients (8.2 x 10(-6) cm(-1)). The cell accumulation of [VO(acac)2] was found to be greater than that of [VO(ma)2], and vanadate caused much less accumulation than the other two compounds. Vanadium compounds induced intracellular reactive oxygen species, reduced the transepithelial electric resistance, caused morphological change in microvilli, and led to different perturbation of F-actin structure.

CONCLUSIONS

The three compounds exhibited different permeability due to different diffusion process and cellular uptake. The toxicity of vanadium complexes on Caco-2 monolayer involved F-actin-related change of tight junction and impairment of microvilli. The toxicity was also related to elevated intracellular reactive oxygen species (ROS) and their cellular accumulation.