Potency classification of isothiazolinone compounds based on defined approaches of skin sensitization in OECD GL 497.

Regulatory decisions for skin sensitization are now based on adverse outcome pathway (AOP) and integrated approaches to testing and assessment (IATA). Based on these, Organisation for Economic Co-operation and Development (OECD) guidelines on defined approaches for skin sensitization were adopted with a fixed data interpretation procedure (DIP). In the guidelines, "Defined Approaches" (DA) on skin sensitization uses the results from multiple information sources of in chemico, in vitro, and in silico data to achieve an equivalent predictive capacity as those of the animal tests. In this review, we evaluated the skin sensitization of eleven isothiazolinone compounds including 4,5-Dichloro-2-octyl-3(2H)-isothiazolone (DCOIT), 2-n-Octyl-4-isothiazolin-3-one (OIT), 2-Methyl-4-isothiazolin-3-one (MIT), 1,2-Benzisothiazolin-3-one (BIT), 1,2-Benzisothiazolin-3-one, 2-butyl (BBIT), 5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4,5-trimethylene-4-isothiazolin-3-one (MTMIT), 2-methyl-1,2-benzothiazol-3-one (MBIT), 2-methyl-1,2-benzothiazole-3-thione (MBIT-S), 1,2-benzisothiazolin-3-one, 2-methyl-, 1,1-dioxide (BBIT-O), and a mixture of CMIT/MIT. Data from direct peptide reactivity assay (DPRA), human cell line activation (h-CLAT) test, and quantitative structure activity relationship (QSAR) Toolbox were evaluated and were applied to the DIP to derive a prediction of hazard identification and a potency classification. Among the evaluated chemicals, six isothiazolinone compounds were classified to be UN GHS 1A, one compound to be UN GHS 1, and four compounds could not be classified due to lack of data. The results of sensitizer chemicals were found to coincide well with those of in vivo test.

The MEK1/2 Pathway as a Therapeutic Target in High-Grade Serous Ovarian Carcinoma.

High-grade serous ovarian carcinoma (HGSOC) is the deadliest of gynecological cancers due to its high recurrence rate and acquired chemoresistance. RAS/MEK/ERK pathway activation is linked to cell proliferation and therapeutic resistance, but the role of MEK1/2-ERK1/2 pathway in HGSOC is poorly investigated. We evaluated MEK1/2 pathway activity in clinical HGSOC samples and ovarian cancer cell lines using immunohistochemistry, immunoblotting, and RT-qPCR. HGSOC cell lines were used to assess immediate and lasting effects of MEK1/2 inhibition with trametinib in vitro. Trametinib effect on tumor growth in vivo was investigated using mouse xenografts. MEK1/2 pathway is hyperactivated in HGSOC and is further stimulated by cisplatin treatment. Trametinib treatment causes cell cycle arrest in G1/0-phase and reduces tumor growth rate in vivo but does not induce cell death or reduce fraction of CD133+ stem-like cells, while increasing expression of stemness-associated genes instead. Transient trametinib treatment causes long-term increase in a subpopulation of cells with high aldehyde dehydrogenase (ALDH)1 activity that can survive and grow in non-adherent conditions. We conclude that MEK1/2 inhibition may be a promising approach to suppress ovarian cancer growth as a maintenance therapy. Promotion of stem-like properties upon MEK1/2 inhibition suggests a possible mechanism of resistance, so a combination with CSC-targeting drugs should be considered.

Population genetic structure of Semisulcospira gottschei: simultaneous examination of mtDNA and microsatellite markers.

Semisulcospira gottschei is an Asian endemic species inhabiting Korea and China. However, genetic structure analysis of the resource management of this species has not been performed. To investigate the genetic diversity among populations, microsatellites can be used to determine the geographic origins of marine and freshwater species. This study investigated the genetic structures of the Korean and Chinese populations of S. gottschei based on mitochondrial DNA (mtDNA) Cytochrome oxidase subunit I (COI) and polymorphic microsatellite loci developed from Semisulcospira coreana. Analysis of the mtDNA COI sequence revealed 43 haplotypes, which indicated no gene flow between the Korean and Chinese populations. To further elucidate the genetic structures of the Korean and Chinese populations, the population genetics of S. gottschei were analyzed using nine microsatellite markers. The genetic diversity analysis showed an average of 5.25 alleles per locus, with an average allelic richness of 4.02. Excessive homozygosity was found at all loci, which was expected to be due to the presence of null alleles at all loci. Populations of S. gottschei formed two separate clusters according to pairwise FST and AMOVA. Also, the UPGMA tree, PCA, STRUCTURE, and GeneClass indicated separation of the 11 populations into two clusters: Korea and China. These results have potential use in the management, restoration, and distinction of the origin country of populations.

A cadmium toxicity assay using stress responsive Caenorhabditis elegans mutant strains.

To test the applicability of Caenorhabditis elegans mutant for toxicity screening, the sensitivity of cadmium (Cd) in C. elegans was investigated on 14 mutant strains using median lethal concentration (LC50) tests, with further analysis on growth and reproduction conducted on five selected strains. The 24h LC50 of Cd observed on the wildtype and mutant strains of C. elegans was in the order of age-1(hx546)>mtl-2(gk125)>sod-3(gk235)>daf-21(p673)>cyp35a2(gk317)>skn-1(or13)>daf-12(rh62rh157)>hsp-16.2(gk249)>daf-18(e1375)>ctl-2(ok1137)>wildtype(N2)>sod-1(or13)>daf-16(mu86)>cep-1(gk138)>cdr-2(ok1996). Compared to the wildtype response, a decreased reproduction potential was observed in mtl-2(gk125), sod-3(gk235), cdr-2(ok1996) and cep-1(gk138) strains. To gain a mechanistic understanding of different sensitivities of the mutant strains, a time-course gene expression analysis was also performed on the five genes. A dramatic increase in the expression of the mtl-2 gene due to Cd exposure confirmed the importance of this gene in C. elegans Cd toxicity. An increased expression of the sod-3 gene at the longer exposure time period (48h) suggests that oxidative stress may not be a direct toxic mechanism, but may rather be a consequence of Cd toxicity. Even though, LC50 values for the age-1(hx546) mutant strain were the highest among the tested strains, the response on the reproduction potential in age-1(hx546) mutant was unchanged compared to the wildtype, and the age-1 gene expression remained unaltered on exposure to Cd, which may be interpreted as the maintenance of age-1 expression level is needed for the exertion of Cd toxicity; however, the role of the age-1 gene in Cd toxicity may not be via a reproduction-related pathway. The overall results suggest that the C. elegans mutant assay seems to be a promising tool for the study of toxic mechanisms, as well as for toxicity screening in ecotoxicological research.