Fluorescent cellular assay for screening agents inhibiting Pseudomonas aeruginosa adherence.

Antibodies against Pseudomonas aeruginosa (PA) lectin, PAIIL, which is a virulence factor mediating the bacteria binding to epithelium cells, were prepared in chickens and purified from egg yolks. To examine these antibodies as a prophylactic agent preventing the adhesion of PA we developed a well plate assay based on fluorescently labeled bacteria and immortalized epithelium cell lines derived from normal and cystic fibrosis (CF) human lungs. The antibodies significantly inhibited bacteria adhesion (up to 50%) in both cell lines. In agreement with in vivo data, our plate assay showed higher susceptibility of CF cells towards the PA adhesion as compared to normal epithelium. This finding proved the reliability of the developed experimental system.

A study on 17alpha-ethinylestradiol metabolism in rat and Pleurotus ostreatus.

OBJECTIVES: 17α-Ethinylestradiol (EE2) is an endocrine disruptor that is an ingredient of oral contraceptives. Here, EE2 metabolism catalyzed by cytochromes P450 (CYP) was studied. Two model organisms, rat and ligninolytic fungus Pleurotus ostreatus, were used. METHODS: To resolve the role of rat and/or fungal CYPs in EE2 oxidation, microsomes were incubated with EE2 and NADPH or cumene hydroperoxide. Using Supersomes™, we examined which of rat CYPs oxidize EE2. RESULTS: EE2 is effectively degraded by P. ostreatus in vivo. In vitro, EE2 is metabolized by CYPs by the NADPH-dependent and organic hydroperoxide-dependent mechanisms. Rat hepatic microsomes metabolize EE2 in the presence of NADPH to three products; two of them are hydroxylated EE2 derivatives. Using rat Supersomes™ we found that EE2 is hydroxylated by several rat CYPs, among them CYP2C6 and 2C11 are most efficient in 2-hydroxy-EE2 formation, while CYP2A and 3A catalyze EE2 hydroxylation to the second product. On the contrary, the products of the NADPH-dependent hydroxylating reactions were not detected in Pleurotus ostreatus. During the reaction of EE2 in microsomes isolated from rat and P. ostreatus in the presence of the alternate oxidant, cumene hydroperoxide, another metabolite, different from the above mentioned products, is generated. Rat CYP1A1 is the most efficient enzyme catalyzing formation of this EE2 product. CONCLUSION: The results suggest that CYPs play a role in EE2 metabolism in rat and P. ostreatus. To our knowledge this is the first finding describing ligninolythic fungal metabolism of EE2 by CYP in the presence of cumene hydroperoxide.

Effect of chicken antibodies on inflammation in human lung epithelial cell lines.

OBJECTIVES: As an alternative therapeutic approach for the prevention and treatment of bacterial infections with P. aeruginosa of cystic fibrosis (CF) patients, chicken yolk antibodies (IgY) could be used. The most significant advantage of IgY, in contrast to mammalian IgG, consists in the fact, that when bound to the antigen, they usually do not induce inflammatory reaction. In addition, the simplicity of egg production and the ease of IgY preparation makes this kind of antibody an excellent tool for passive immunization. Thus, the aim of our project was to study the effect of IgY and its Fab fragment on the potential induction of pro-inflammatory reactions in lung epithelial cells. METHODS: Chicken IgY were prepared from pooled egg yolks. Fab fragmens of IgY were purified from the papain digest of IgY using DEAE-Sephacel ion exchange chromatography. Their purity was verified by SDS electrophoresis in polyacrylamide gel. Immortalized human cell lines, CuFi (CF patient) and NuLi (healthy subject), and A549 (human adenocarcinoma cells) were exposed to IgY, Fab, OVA, LPS (positive control), PBS (negative control), and human and goat IgG for 24 hours. The concentration of pro-inflammatory cytokines TNF-α, IL-1ß, IL-6 and GM-CSF were determined in cell media using the BioPlex method, which enables the quantification of multiple analytes simultaneously in one sample. RESULTS: Our results show that i) the Fab fragment induced levels of some proinflammatory cytokines, when compared to the PBS control, whereas ii) chicken IgYs did not induce any notable production of pro-inflammatory cytokines in contrast to intense effect of LPS on TNF-α and GM-CSF. In summary, our data show that levels of all cytokines are comparable with physiological values in human serum except of IL-1ß, which concentration in cell medium was markedly elevated by Fab fragment. CONCLUSIONS: The present data indicate that IgY are not inflammatory for lung cells and thus they are possibly applicable for prevention of airway bacterial infections.

Effects of cytochrome P450 inhibitors on peroxidase activity.

OBJECTIVES: Of several enzymes metabolizing xenobiotics, cytochrome P450 (CYP) and peroxidase enzymes seem to be most important. One of the major challenges in studies investigating metabolism of xenobiotics is to resolve which of these two groups of enzymes is predominant to metabolize individual xenobiotic compounds. Utilization of selective inhibitors of CYP and peroxidase enzymes might be a useful tool to identify the contribution of these enzymes to metabolism of xenobiotics in samples, where both types of enzymes are present. The aim of this study was to investigate specificities of several known CYP inhibitors to these enzymes; whether they inhibit only the CYP enzymes and do not inhibit peroxidases. METHODS: Since the oxidation of o-anisidine catalyzed by a model peroxidase used, horseradish peroxidase (HRP), is a two-substrate reaction, the inhibition potential of tested chemicals was studied with respect to both peroxidase substrates, o-anisidine and hydrogen peroxide. Initial velocities of o-anisidine oxidation by HRP under various conditions were determined spectrophotometrically. RESULTS: The CYP inhibitors metyrapone, troleandomycine, disulfiram, sulfaphenazole, quinidine and 1-aminobenzotriazole do not inhibit o-anisidine oxidation catalyzed by HRP. In contrast, ketoconazole, diethyldithiocarbamate, ellipticine, α-naphtoflavone, proadifen SKF525A, piperonylbutoxide, were found to inhibit not only the CYPs, but also the HRP-mediated oxidation of o-anisidine. Interestingly, α-naphtoflavone inhibits oxidation of o-anisidine by HRP with respect to H2O2, but not with respect to o-anisidine. Diethyldithiocarbamate is the most potent peroxidase inhibitor of o-anisidine oxidation with Ki with respect to o-anisidine of 10 µM and Ki with respect to H2O2 of 60 µM, being even the better peroxidase inhibitor than the classical "peroxidase inhibitor" - propyl gallate (Ki with respect to o-anisidine of 60 µM and Ki with respect to H2O2 of 750 µM). CONCLUSIONS: The results of the present study demonstrate that 1-aminobenzotriazole, a potent inhibitor of various CYP enzymes, seems to be the best candidate suitable for utilization in studies evaluating participation of CYP enzymes in metabolism of xenobiotics in various complex biological materials containing both CYP and peroxidase enzymes. Moreover, precaution to prevent misinterpretation of results is necessary in cases when proadifen SKF525A, piperonylbutoxide, diethyldithiocarbamate, ketoconazole, α-naphtoflavone and ellipticine are used in similar studies (as CYP inhibitors in various complex biological materials containing both CYP and peroxidase enzymes), since these chemicals can except of CYP enzymes inhibit also peroxidase-mediated reactions.

Comparison of activation of aristolochic acid I and II with NADPH:quinone oxidoreductase, sulphotransferases and N-acetyltranferases.

OBJECTIVES: Ingestion of aristolochic acid (AA) is associated with development of urothelial tumors linked with aristolochic acid nephropathy, and is implicated in the development of Balkan endemic nephropathy-associated urothelial tumors. Aristolochic acid I (AAI), the major toxic component of AA, is more toxic than its demethoxylated derivate AAII. A different enzymatic conversion of both carcinogens might be one of the reasons explaining this feature. Therefore, the present study has been designed to compare efficiency of human NAD(P)H:quinone oxidoreductase (NQO1) and phase II enzymes such as sulfotransferases (SULTs) and N,O-acetyltransferases (NATs) to activate AAI and AAII in vitro. In addition, to investigate the molecular mechanisms of AAI and AAII reduction by human NQO1, molecular modeling was used to compare interactions of AAI and AAII with the active site of this enzyme. METHODS: DNA adduct formation by AAI and AAII was investigated by the nuclease P1 version of the 32P-postlabeling method. In silico docking, employing soft-soft (flexible) docking procedure, was used to study the interactions of AAI and AAII with the active site of human NQO1. RESULTS: Human NQO1 activated AAI and AAII, generating DNA adduct patterns reproducing those found in several species including human exposed to these compounds. These results demonstrate that NQO1 is capable of reducing both AAs to reactive species binding to DNA. However, concentrations required for half-maximum DNA binding mediated by NQO1 were higher for AAII (158 µM) than for AAI (17 µM). One of the reasons causing this phenomenon is a lower efficiency of NQO1 to reduce AAII than AAI we found in this work; although both AAI and AAII are bound with similar binding affinities to the NQO1 active site, the binding orientation of AAII in the active site of NQO1 does not favor the effective reduction of its nitro group. Because reduced nitro-aromatics are often further activated by SULTs or NATs, their roles in AAI and AAII activation were investigated. Our results indicate that phase II reactions do not stimulate the bioactivation of AAs; neither enzymes present in human hepatic cytosols nor human SULT1A1, 1A2, 1A3, 1E, or 2A nor NAT1 or NAT2 further enhanced DNA adduct formation by AAs. In contrast, human SULT1A1, 1A2 and 1A3 as well as NAT1 and NAT2 enzymes even inhibited NQO1-mediated bioactivation of AAII. Therefore, under the in vitro conditions used, DNA adducts arise by enzymatic reduction of AAs through the formation of N-hydroxyaristolactams that are spontaneously decomposed to the reactive species forming DNA adducts. CONCLUSION: The results found in this study emphasize the importance of NQO1 in the metabolic activation of AAI and AAII and provide the evidence that initial nitroreduction is the rate limiting step in their activation. This enzyme is more effective in activation of AAI relative to AAII, which might contribute to its lower binding to DNA found both in vitro and in vivo, Moreover, inhibition effects of conjugation reactions on AAII activation might further contribute to its decreased capability of forming DNA adducts and its lower toxicity comparing with AAI.