Further evidence for photoinduced genotoxicity of dictamnine as shown by prophage induction.

Photobiological activity of dictamnine, a furoquinoline alkaloid, to induce lytic phage development in a lysogen of Escherichia coli was measured as a line of evidence for the photoinduced genotoxicity. Since dictamnine forms the monoadducts to DNA but not the diadducts (DNA cross-links) by photoirradiation, the photobiological activity was compared with that of a cross-linking agent 5-methoxypsoralen, a structural analog, on the basis of relative quantum yield. The activity of dictamnine with respect to both phage induction and photoinduced lethal activity was weaker than the psoralen derivative. Any lethal DNA damage including monoadducts and diadducts of 5-methoxypsoralen appeared to contribute to prophage induction at the same level of efficiency.

Evidence for uptake of 8-methoxypsoralen and 5-methoxypsoralen by cellular nuclei.

The fluorescent appearance of oral mucosa cells treated with 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP) was observed by means of fluorescence microscopy. Fluorescence at the nuclei was weakened in 8-MOP-treated cells, while it was intensified in 5-MOP-treated cells. These findings were consistent with changes in the fluorescence intensities on association of the psoralen derivatives with DNA in aqueous solution. This intensity change of fluorescence and also the blue shift of the fluorescence maximum of the derivatives on association suggested that the environment around the psoralen molecules is as little polar as methanol. From the results of these fluorescence microscopic observations and spectroscopic analysis of fluorescence of derivatives interacting with DNA during equilibrium dialysis, we concluded that 8-MOP, as well as 5-MOP, is incorporated by nuclei of human cells.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (3) Evaluation of the haemolysis test.

The haemolysis test using sheep red blood cells (RBC) was evaluated as an alternative method to the Draize rabbit eye irritation test (Draize test) by six to nine laboratories. The participating laboratories performed the test according to the standard operating procedure (SOP). Thirty-eight cosmetic ingredients and isotonic sodium chloride solution were used as test substances in this validation study. The concentrations of the test substances that induced 50% haemolysis (HC(50) value) was obtained to serve as a toxicological index and compared with in vivo Draize scores. HC(50) values were not obtained for coloured or water-insoluble (turbid) substances. Three acids caused denaturation of haemoglobin leaked from RBC and consequently interfered with the determination of the HC(50) value. Interlaboratory reproducibility was relatively good except in the case of water-insoluble substances. The average values of coefficient of variation (CV) was 37%. The correlation coefficient and Spearman's rank correlation between the HC(50) value and maximum average Draize total score (MAS) were -0.631 and 0.641, respectively. The equivalence ratio between the haemolysis test and MAS was 70.0% when MAS 15 was set as the in vivo cut-off point. On the other hand, strong irritants (MAS50) could be correctly classified by this method. These results suggest that the haemolysis test might be applied to cosmetic ingredients as a screening method to distinguish strong irritants that directly affect the cell membrane permeability and do not disturb spectrophotometrical determination of haemoglobin. In order to evaluate the potential for eye irritation of cosmetic ingredients, a combination of haemolysis with other methods based on different mechanism should be employed to improve the predictability.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (10) Evaluation of cytotoxicity test on CHL cells.

The present interlaboratory validation study was performed in order to evaluate the use of Chinese hamster lung cell lines that employs crystal violet staining (CHL-CVS) as an alternative cytotoxicity test to the Draize eye irritation test (Draize test) for cosmetic ingredients. Ten substances, nine of which were surfactants, were evaluated at seven laboratories in the first phase of the validation study; 15 substances including dyes and lipids were evaluated at seven laboratories in the second phase of the validation study; 14 substances including acids and alkalis were evaluated at four laboratories in the third phase of the validation study. The logEC(50) values obtained for CHL-CVS were compared with the maximal average Draize total score (MAS) for a 10% (w/v) solution of 38 cosmetic ingredients as well as isotonic sodium chloride solution. The interlaboratory coefficient of variation (CV) for EC(50)s was 35.6%, which was considered to be within a tolerable range. The correlation coefficient and the Spearman's rank correlation coefficient between the in vitro and in vivo tests were -0.729 and 0.709, respectively. The prediction ability of the proposed method was assessed from the linear regression line for a MAS cut-off point of 15. According to this analysis, four substances (two alcohols and two acids) were determined to be false negative. The present study revealed the following characteristic factors of this method: (1) CHL-CVS could be applied to all the test substances including dyes and lipids in this study; (2) The results for medium-insoluble substances varied according to the laboratory; (3) The correlation between the in vivo and in vitro data for acids and alcohols (lower mono-ol) differed from that of the other substances. These results suggested that the CHL-CVS might have a potential to predict the Draize MAS if definite criteria can be established for the compounds to be applicable.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (11) EYTEX(TM).

EYTEX(TM) is an in vitro test system for predicting the ocular irritation potential of chemicals and formulations. This method was evaluated as an alternative method to the Draize eye irritation test (Draize test) for the eye irritation potential of several cosmetic ingredients in a three-phase validation study conducted at five to seven laboratories. Thirty-nine test substances were used as coded samples. The test procedures were controlled under the same standard operating procedure (SOP) at all participating laboratories. The interlaboratory coefficient of variation (CV) was 20.8%. The correlation coefficient between EYTEX scores and the maximal average Draize total score (MAS) was 0.313. Irritancy classifications were established based on the results of 54 EYTEX tests and the EYTEX/Draize equivalent was calculated. Thirty-eight EYTEX test results concurred with the results of the Draize test, substantial equivalence was 70.4%. These results indicate that EYTEX provides a rough method of classification rather than providing absolute values. The present results also indicate that EYTEX has the following characteristics: (1) intensely coloured substance may not be compatible; (2) some cationic surfactants may be underestimated; (3) EYTEX can be applied to most test substances under the same conditions as the in vivo tests.

Interlaboratory Validation of the in vitro Eye Irritation Tests for Cosmetic Ingredients. (4) Haemoglobin Denaturation Test.

Interlaboratory validation of the haemoglobin denaturation (HD) test on 38 cosmetic ingredients was conducted by five to eight participating laboratories. The HD test was evaluated as an alternative method to the Draize eye irritation test (Draize test) based on three indices of protein denaturation: the test substance concentration that induces 50% HD of the positive control (RDC(50)), a relative HD rate at 1% of the test substance (1%RDR) and a relative change in maximum absorption wavelength (1% lambdamax). The coefficients of variation associated with a positive HD test among the participating laboratories were within an acceptable range for practical application. The in vitro test results were in relatively good agreement with the Draize test. The correlation coefficient (r) between the in vivo maximal average Draize total score (MAS) and log (RDC(50)), 1%RDR and 1% lambdamax were -0.91, 0.67 and 0.79, respectively. The results revealed several limitations associated with the HD test: (1) the HD test cannot be applied to coloured test substances with a strong absorption, around 418nm; (2) water-insoluble test substances cannot be evaluated by RDC(50) or 1%RDR; (3) the HD test cannot be applied to strong acids that exceed the buffering capacity of a phosphate buffer solution; (4) the HD test cannot be used to determine the potential for eye irritation caused by factors other than protein denaturation, for example, polyoxyethylene octylphenylether (10 E.O.). Thus, the HD test alone is not appropriate for predicting eye irritation potential. Nevertheless, the good agreement between the HD test results and in vivo irritation scores as well as the ease of application suggest that this test may play an important role in a test system to determine eye irritation potential.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients (9). Evaluation of cytotoxicity test on HeLa cells.

The cytotoxicity test using MTT on HeLa cells (HeLa-MTT) was evaluated as an alternative method to the Draize eye irritation test (Draize test) by six to eight laboratories. The 50% inhibition concentration (EC(50)) for MTT reduction was calculated. A total of thirty-nine test chemicals were examined. The average interlaboratory coefficient of variation (CV) of the present assay was 25%. Comparison of the in vitro test results with those of the Draize test revealed a correlation coefficient of -0.799 between the log(EC(50)) value and the maximum average total score (MAS) for a 10% solution or suspension. The following characteristics of HeLa-MTT have become apparent through this validation: (1) HeLa-MTT could be applied to all substances including water-insoluble substances, esters, a colour additive, and a substance which is known to directly reduce MTT; (2) there is good interlaboratory reproducibility and strong correlation between HeLa-MTT and Draize MAS; (3) results for strong acids, alkanolamines and alcohols (lower mono-ol) clearly deviate from other samples with respect to the correlation between HeLa-MTT and Draize MAS. These results suggest that HeLa-MTT may be useful for predicting the Draize MAS if definite criteria can be established for applicable compounds.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (1) Overview of the validation study and Draize scores for the evaluation of the tests.

A three-step interlaboratory validation of alternative methods to the Draize eye irritation test (Draize test) was conducted by the co-operation of 27 organizations including national research institutes, universities, cosmetic industries, kit suppliers and others. Twelve alternative methods were evaluated using 38 cosmetic ingredients and isotonic sodium chloride solution. Draize tests were conducted according to the OECD guidelines using the same lot of test substances as was evaluated in the alternative tests. Results were as follows. (1) Variation in Draize scores was large near the critical range (maximal average Draize total scores (MAS)=15-50) for the evaluation of cosmetic ingredients. (2) Interlaboratory variation was relatively small for the alternative tests. The mean coefficients of variation (CV%) were less than 50 for all assays except for the hen's egg-chorioallantoic membrane test (HET-CAM), chorioallantoic membrane-trypan blue staining test (CAM-TB) and haemoglobin denaturation test (HD). The CV% of these three methods came into the same range as the other tests when non-irritants were excluded from the data analysis. (3) Results for acids (pH of 10% solution <2.5), alkalis (pH of 10% solution >11.5) and alcohols (lower mono-ol) in cytotoxicity tests clearly deviated from the other samples in the comparison of cytotoxicity with Draize results. (4) Pearson's correlation coefficients (r) between results from cytotoxicity tests using serum and MAS were -0.86 to -0.92 for samples excluding acids, alkalis and alcohols. (5) When the samples were divided into liquids and powders, r of CAM-TB increased from 0.71 for all samples to 0.80 and 0.92, respectively. (6) Spearman's rank correlation coefficients between the results of alternative methods and MAS were relatively high (r>0.8) in the case of HET-CAM and CAM-TB. Those for cytotoxicity tests were high if the data for acids, alkalis and alcohols were excluded (SIRC-CVS: r=0.945, SIRC-NRU: r=0.931, HeLa-MTT: r=0.926, CHL-CVS: r=0.880). Exclusion of data for powdered samples also increased the coefficient of HET-CAM and CAM-TB to 0.831 and 0.863, respectively. These results suggest that no single method can constitute an evaluation system applicable to all types of test substances by itself. However, several methods will be useful for the prediction of eye irritation potential of cosmetic ingredients if they are used with clear understanding of the characteristics of those methods.

Interlaboratory Validation of the In Vitro Eye Irritation Tests for Cosmetic Ingredients. (6) Evaluation of MATREX((TM)).

MATREX(TM) is a test system for evaluating eye irritation potential, using the living dermal model (LDM). The LDM consists of normal human dermal fibroblasts in a contracted collagen lattice, which eventually forms a three-dimensional structure. This system has several advantages. It can be applied to insoluble substances and does not require sterile conditions for operation. In the present study, MATREX was introduced as an alternative to the Draize eye irritation test (Draize test) for cosmetics ingredients. MATREX was evaluated through a three-phase series interlaboratory validation as part of a joint project of the National Institute of Health Sciences (NIHS) and Japan Cosmetic Industry Association (JCIA). Toxicity for LDM was mainly evaluated by cytotoxicity, the indicator was EC(50) (concentration that inhibits the viability of the cell to 50% of control) value. Additionally, MATREX score indicating the grade of cytotoxicity was also introduced in the third phase of the validation study. Both test procedures were controlled under the same standard operating procedure (SOP), at all the participating laboratories. A total of 39 test substances both water-soluble and -insoluble were examined. LDM was applicable to almost all substances that could be evaluated by the Draize test. Furthermore interlaboratory variance was relatively low. The correlation coefficient between the EC(50) value and the maximal average Draize total score (MAS) was -0.672. The MATREX score was closely related to the EC(50) value. Moreover, the MATREX scoring method showed a similar prediction ability for eye irritation potential to the EC(50) method. Thus, the MATREX scoring method, a simplified EC(50) method, appears to be a viable alternative to the current EC(50) measurement method. The present results demonstrate the possibility that the MATREX system would form part of a prediction system of Draize test results.

Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (5) Skin(2TM) ZK1100 and tissue equivalent assay.

Skin(2TM) ZK1100 (ZK1100) assay and tissue equivalent assay (TEA, Skin(2TM) ZK1200) are human dermal models. These assays were evaluated as alternatives to the Draize eye irritation test (Draize test) in rabbits. Thirty-nine cosmetic ingredients were selected and used as test substances. The ZK1100 assay was conducted according to an original protocol provided by Advanced Tissue Sciences, a kit supplier. The TEA assay followed a protocol developed by Osborne et al., (1995a). Coefficients of variation (CV) ranged from 11.7 to 133 in results from the ZK1100 assay; three test substances showed the CVs more than 100. These were cetyltrimethylammonium chloride (S3-7), domiphen bromide (S3-11) and di(2-ethylhexyl) sodium sulfosuccinate (S3-14). Acid Red 92 (S2-3) was excluded from data analysis because its absorbance interfered with the endpoint of ZK1100 assay. The CVs from the TEA assay ranged from 31.8 to 119; two test substances showed the CVs more than 100. These were acetic acid and glycolic acid (S3-13). Butanol (S3-9) was excluded from the analysis because it was assumed to volatilize during a sample preparation. Pearson's coefficient of correlation with maximum average Draize total score (MAS) and 24hr score from the Draize tests were -0.71 and -0.72 for the ZK1100 results and -0.63 and -0.60 for the TEA results. When a MAS of 15 was set as a breakpoint for the classification of eye irritancy on Cooper's plots comparing the in vitro and the Draize data, the ZK1100 results showed five false positives and four false negatives; the TEA results showed three false positives and no false negatives.

[Analysis of contact dermatitis by cytokines. I].

The study of the participation of T cells and the kinetic studies of cytokines by the RT-PCR method in the challenge phase of contact hypersensitivity reaction (CHR) were performed using skin tissues collected at regular intervals from mice sensitized with 2,4-dinitro-1-fluorobenzene (DNFB). The results obtained from these studies and the further analyses using anti-CD4 and CD8 antibodies showed that the revelation of phenotype of lymph node cells at the reaction site and T lymphocytes at the CHR site were found to play important roles. Furthermore, we examined cytokines formed at the CHR site on the mRNA level. Consequently, it was found that 24 h after the challenge IFN-gamma, IL-6 and IL-1 beta were expressed and 48 h after the challenge IL-2, IL-4 and TNF-alpha were expressed in addition to these cytokines. The results of the expression of IL-12 and those of the examination using IFN-gamma knock out mice suggested that the expression of IFN-gamma among several Th1 types of cytokine is especially important for the formation of CHR.

[Analysis of contact dermatitis by cytokines. II].

We examined the mechanism of the onset of contact hypersensitivity reaction (CHR) induced by several kinds of chemical substances in mice, focusing on cytokines. Before doing this experiment, we investigated the involvement of T cells in the formation of CHR using each primer of CD4 and CD8 (surface markers of lymphocytes) positive cells. It was suggested that both cells participate in the formation of CHR. On the basis of these results we analyzed cytokines produced in the reaction site on the mRNA level in with or without the presensitization of two kinds of strong contactants. Consequently, there was a tendency that the expression of mRNA of Th1 types of cytokines was commonly observed around 24 h after the reaction irrespective of the presence or the absence of presensitization. These date suggested that CHR can be presumed on the genetic level by the only one priming of strong contactants.

[Analysis of contact dermatitis by cytokines. III.--Sensitization and crossreaction of phenolic compounds].

We examined sensitization and crossreaction by the guinea pig maximization test (GPMT) with phenolic compounds. Skin specimens were collected from earlobes of BALB/c mice on 24 h after elicitation phase of contact hypersensitivity reaction (CHR) with phenolic compounds. The expression of cytokines of skin specimens was examined by the reverse transcriptase/polymerase chain reaction (RT-PCR) method. Consequently, phenolic compounds which showed positive reaction in GPMT expressed IL-2 and IFN-gamma on 24 h after elicitation, and some phenolic compounds showed marked crossreaction. Therefore, it was found that on several phenolic compounds, dimerization of these compounds from monomer to dimer decrease sensitization.

[Analysis of contact dermatitis by cytokines 4--Skin sensitization of biphenyl compounds].

Clove buds oil is one of very important natural essential oil with a typical spicy note and also known as a source of eugenol. These phenol compounds, which have the strong perfume of clove, are widely used not only as an analgesic and antiseptic agent in dentistry. However, the problem is that the phenol compounds caused sensitization on the skin occasionally. We reported that the skin sensitization by eugenol and its derivatives was detected in the guinea pig maximization test (GPMT) and also confirmed that dehydrodi-eugenol, a biphenyl compound of eugenol, did not show the skin sensitization. To discuss more, we examined the skin sensitization by several phenol compounds and its biphenyl ones. Consequently, we confirmed that the skin sensitization by biphenyl compounds more remarkably decreased than that by phenol compounds (monomer).

Salivary bisphenol-A levels detected by ELISA after restoration with composite resin.

Bisphenol-A diglycidylether methacrylate (Bis-GMA), which is synthesized from bisphenol-A (BPA), a compound with exogenous endocrine disrupter action, is widely used as a dental material. During clinical filling with sealants and composite resins, the compounds are solidified by polymerization and then used. However, it has been noted that unpolymerized monomers may become dissolved in saliva. In this study using a competitive ELISA system, we investigated the changes in the BPA concentration in saliva after restoration with composite resins. Commercial composite resins from nine companies were tested. Mixed saliva was collected from 21 subjects. Based on the dynamics of salivary BPA detected by this ELISA system, we concluded that several tens to 100 ng/ml of BPA were contained in saliva after filling teeth with composite resin but that sufficient gargling can remove it from the oral cavity. Our data suggest that sufficient gargling after treatment is important for risk management.