Use of an Ex Vivo Porcine Mucosal Model to Study Superantigen Penetration.

In vitro perfusion studies are frequently used to determine the penetration of compounds through skin and mucosa. Porcine tissue has been shown to be an excellent model for human tissue in terms of structure, function, and reactivity. We describe the use of porcine tissue ex-vivo in a continuous flow perfusion system to study the behavior of superantigens in this model.

Use of porcine vaginal tissue ex-vivo to model environmental effects on vaginal mucosa to toxic shock syndrome toxin-1.

Menstrual toxic shock syndrome (mTSS) is a rare, recognizable, and treatable disease that has been associated with tampon use epidemiologically. It involves a confluence of microbial risk factors (Staphylococcus aureus strains that produce the superantigen-TSST-1), as well as environmental characteristics of the vaginal ecosystem during menstruation and host susceptibility factors. This paper describes a series of experiments using the well-characterized model of porcine vaginal mucosa ex-vivo to assess the effect of these factors associated with tampon use on the permeability of the mucosa. The flux of radiolabeled TSST-1 and tritiated water ((3)H2O) through porcine vaginal mucosa was determined at various temperatures, after mechanical disruption of the epithelial surface by tape stripping, after treatment with surfactants or other compounds, and in the presence of microbial virulence factors. Elevated temperatures (42, 47 and 52°C) did not significantly increase flux of (3)H2O. Stripping of the epithelial layers significantly increased the flux of labeled toxin in a dose-dependent manner. Addition of benzalkonium chloride (0.1 and 0.5%) and glycerol (4%) significantly increased the flux of (3)H2O but sodium lauryl sulfate at any concentration tested did not. The flux of the labeled toxin was significantly increased in the presence of benzalkonium chloride but not Pluronic® L92 and Tween 20 and significantly increased with addition of α-hemolysin but not endotoxin. These results show that the permeability of porcine vagina ex-vivo to labeled toxin or water can be used to evaluate changes to the vaginal environment and modifications in tampon materials, and thus aid in risk assessment.

Effect of menthol on the penetration of tobacco carcinogens and nicotine across porcine oral mucosa ex vivo.

INTRODUCTION: Menthol is a flavored tobacco additive claimed to mask the bitter taste and reduce the harshness of cigarette smoke. (Azzi, C., Zhang, J., Purdon, C. H., Chapman, J. M., Nitcheva, D., Hebert, J. R., et al., 2006, Permeation and reservoir function of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P) across porcine esophageal tissue in the presence of ethanol and menthol. Carcinogenesis, 27, 137-145). have shown that menthol increased the flux of tobacco carcinogens (TC) across porcine esophagus. As oral mucosa is exposed to both smoke and smokeless tobacco in tobacco users, the objective of this study was to determine whether menthol influenced the penetration of the TC nitrosonornicotine (NNN) across porcine buccal (BM) and floor of mouth (FM) mucosa. METHODS: Porcine BM and FM were collected at slaughter, mounted in perfusion chambers (n = 7/group), and exposed to tritiated NNN ((3)H-NNN; Amersham, activity 1 muCi/ml) and tritiated nicotine ((3)H-nicotine; Sigma) in 3% nicotine/phosphate-buffered saline (0.01 M, pH 7.4) containing 0.01% unlabeled NNN (National Cancer Institute Chemical Carcinogen Repository) +/- 0.08% menthol for 0.5, 1, 2, or 12 hr. K(p) values (cm/min) were determined and statistically analyzed (analysis of variance, Tukey's, p < .05). RESULTS: FM and BM permeability to both (3)H-NNN and (3)H-nicotine was significantly increased (p < .05) with addition of menthol over that of nicotine alone regardless of exposure times. Even short 30-min menthol exposure significantly increased the flux of both compounds, and this was maintained throughout the experiment. DISCUSSION: Menthol enhances penetration of NNN and nicotine through FM and BM in vitro, even after short exposure. This may reflect loading of a superficial epithelial reservoir (Squier, C. A., Kremer, M. J., Bruskin, A., Rose, A., & Haley, J. D., 1999. Oral mucosal permeability and stability of transforming growth factor beta-3 in vitro. Pharmaceutical Research, 16, 1557-1563.), thus delivering menthol and enhancing flux for several hours. Practical implications are for a potentially increased oral exposure to carcinogens among users of menthol-flavored cigarettes and chewing tobacco.

Cytolysins augment superantigen penetration of stratified mucosa.

Staphylococcus aureus and Streptococcus pyogenes colonize mucosal surfaces of the human body to cause disease. A group of virulence factors known as superantigens are produced by both of these organisms that allows them to cause serious diseases from the vaginal (staphylococci) or oral mucosa (streptococci) of the body. Superantigens interact with T cells and APCs to cause massive cytokine release to mediate the symptoms collectively known as toxic shock syndrome. In this study we demonstrate that another group of virulence factors, cytolysins, aid in the penetration of superantigens across vaginal mucosa as a representative nonkeratinized stratified squamous epithelial surface. The staphylococcal cytolysin alpha-toxin and the streptococcal cytolysin streptolysin O enhanced penetration of toxic shock syndrome toxin-1 and streptococcal pyrogenic exotoxin A, respectively, across porcine vaginal mucosa in an ex vivo model of superantigen penetration. Upon histological examination, both cytolysins caused damage to the uppermost layers of the vaginal tissue. In vitro evidence using immortalized human vaginal epithelial cells demonstrated that although both superantigens were proinflammatory, only the staphylococcal cytolysin alpha-toxin induced a strong immune response from the cells. Streptolysin O damaged and killed the cells quickly, allowing only a small release of IL-1beta. Two separate models of superantigen penetration are proposed: staphylococcal alpha-toxin induces a strong proinflammatory response from epithelial cells to disrupt the mucosa enough to allow for enhanced penetration of toxic shock syndrome toxin-1, whereas streptolysin O directly damages the mucosa to allow for penetration of streptococcal pyrogenic exotoxin A and possibly viable streptococci.

Novel toxic shock syndrome toxin-1 amino acids required for biological activity.

Superantigens interact with T lymphocytes and macrophages to cause T lymphocyte proliferation and overwhelming cytokine production, which lead to toxic shock syndrome. Staphylococcus aureus superantigen toxic shock syndrome toxin-1 is a major cause of menstrual toxic shock syndrome. In general, superantigen-secreting S. aureus remains localized at the vaginal surface, and the superantigen must therefore penetrate the vaginal mucosa to interact with underlying immune cells to cause toxic shock syndrome. A dodecapeptide region (toxic shock syndrome toxin-1 amino acids F119-D130), relatively conserved among superantigens, has been implicated in superantigen penetration of the epithelium. The purpose of this study was to determine amino acids within this dodecapeptide region that are required for interaction with vaginal epithelium. Alanine mutations were constructed in S. aureus toxic shock syndrome toxin-1 amino acids D120 to D130. All mutants maintained superantigenicity, and selected mutants were lethal when given intravenously to rabbits. Toxic shock syndrome toxin-1 induces interleukin-8 from immortalized human vaginal epithelial cells; however, three toxin mutants (S127A, T128A, and D130A) induced low levels of interleukin-8 compared to wild type toxin. When carboxy-terminal mutants (S127A to D130A) were administered vaginally to rabbits, D130A was nonlethal, while S127A and T128A demonstrated delayed lethality compared to wild type toxin. In a porcine ex vivo permeability model, mutant D130A penetrated the vaginal mucosa more quickly than wild type toxin. Toxic shock syndrome toxin-1 residue D130 may contribute to binding an epithelial receptor, which allows it to penetrate the vaginal mucosa, induce interleukin-8, and cause toxic shock syndrome.

Porcine vagina ex vivo as a model for studying permeability and pathogenesis in mucosa.

The vaginal mucosa is commonly exposed to a variety of topical agents, including chemical contraceptives, drugs for the treatment of specific pathological conditions, and pathogenic microorganisms. In vitro models can provide important information regarding the penetration and efficacy of topical compounds as well as the pathogenesis of various diseases such a menstrual toxic shock syndrome. Realistic and reproducible test systems are important if new agents are to fulfill their therapeutic potential in human populations. The selection of appropriate animal species and tissue and the use of valid in vitro systems can avoid many of the shortcomings of current animal and cell culture test systems. This review provides information about the factors that should be considered when selecting the best model to study the permeability of the human vagina. The characteristics of an ex vivo porcine model are explored and the validity of this model is demonstrated in terms of its histology, ultrastructure and composition and organization of the permeability barrier; data indicate excellent correlation of permeability and tissue response between human and porcine vaginal tissue.