It is well established that platinum-based drugs, including oxaliplatin (L-OHP) and cisplatin (CDDP), as well as microtubule inhibitors paclitaxel (PTX) and vincristine (VCR), are associated with chemotherapy-induced peripheral neuropathy (CIPN). In this study, we examined and compared the characteristics of neuropathies induced by L-OHP, CDDP, PTX, and VCR to evaluate whether Caenorhabditis elegans (C. elegans) could serve as a model organism for human CIPN. Worms were cultured on nematode growth medium plates, and L1 larvae synchronized by gel filtration were employed. We then performed bioassays and examined motility. In the motility test, exposure was performed for 2, 24, and 48 hr, and time-dependent effects were measured for each exposure time and 24 hr after terminating exposure. Herein, we observed that L-OHP and CDDP exerted concentration-dependent effects above a certain concentration, and PTX and VCR exerted concentration-dependent negative effects in the bioassay. Motility recovered in L-OHP-, PTX-, and VCR-treated worms on terminating exposure. However, CDDP exposure tended to reduce motility even 24 hr after terminating exposure. L-OHP exposure could decrease motility 2 hr after exposure, with a trend toward recovery 24 hr after terminating drug exposure. The findings of the present study revealed that C. elegans could exhibit neuropathy characteristics suggested to be similar to those observed in humans, indicating that this organism could be a suitable model to explore human CIPN.

We have developed an early detection method for bladder carcinogens with high sensitivity and specificity using immunohistochemistry of γ-H2AX, a well-known marker of DNA damage. To investigate the potential application of γ-H2AX as a biomarker for early detection of hepatocarcinogens, we examined γ-H2AX formation in the liver of rats treated with several different chemicals for 28 days. Six-week-old male F344 rats were orally treated for 28 days with five hepatocarcinogens: N-nitrosodiethylamine (DEN), di(2-ethylhexyl) phthalate, 1,4-dioxane (DO), 3,3’-dimethylbenzidine dihydrochloride, or thioacetamide (TAA), or with two non-hepatocarcinogens: 4-chloro-o-phenylenediamine and N-ethyl-N-nitrosourea. At the end of the treatment period, immunohistochemistry for γ-H2AX and Ki67 and expression analysis of DNA repair-related genes were performed. Significant increases in γ-H2AX-positive hepatocytes with upregulation of Rad51 mRNA expression were induced by three of five hepatocarcinogens (DEN, DO, and TAA), whereas no changes were seen for the other two hepatocarcinogens and the two non-hepatocarcinogens. Significant increases in Ki67 expression with upregulation of Brip1, Xrcc5, and Lig4 were observed in rats treated with TAA, a nongenotoxic hepatocarcinogen, suggesting that both direct DNA damage and secondary DNA damage due to cell replication stress may be associated with γ-H2AX formation. These results suggest that γ-H2AX immunostaining has potential value for early detection of hepatocarcinogens, but examination of the effects of more chemicals is needed, as is whether γ-H2AX immunostaining should be combined with other markers to increase sensitivity. γ-H2AX immunostaining using formalin-fixed paraffin-embedded specimens can be easily incorporated into existing 28-day repeated-dose toxicity studies, and further improvements in this method are expected.

Several studies revealed that gut microbiota affects the hepatic drug-metabolizing enzyme cytochrome P450 (Cyp). We hypothesized that individual gut microbiota variations could contribute to CYP activity. Human flora-associated (HFA) mice are established from germ-free mice using human feces and are often used to determine the effect of the human gut microbiota on the host. This study generated two groups of HFA mice using feces from two healthy individuals. Then, the composition of gut microbiota and hepatic Cyp activity was compared to analyze the effects of gut microbiota in healthy individuals on hepatic Cyp activity. A principal coordinate analysis based on the UniFrac distance for the composition of the cecal and fecal microbiota revealed apparent differences between the recipient groups. Hepatic Cyp, which is a marked difference in Cyp3a activity and Cyp3a11 gene expression, was observed between the recipient groups. Cyp2c and Cyp1a activities did not differ between recipient groups, with significantly lower enzymatic activities in recipients than in germ-free mice. These results indicate that the human gut microbiota affects hepatic Cyp activity. Especially, human gut microbiota composition differences have a pronounced effect on Cyp3a activity via Cyp3a11 gene expression regulation. Therefore, human gut microbiota variations among individuals may affect numerous drug metabolism, leading to drug efficacy and toxicity.

Liver ischemia reperfusion (IR) injury induces hepatic stellate cell (HSC) activation and liver fibrosis. Propofol (PRO) possesses a positive protective effect on liver ischemia reperfusion injury. We aimed to investigate PRO function and mechanism in IR-induced liver fibrosis. A mice model of liver IR was established. Hematoxylin-eosin (HE) staining was utilized to evaluate liver tissue’s pathological changes. Masson staining was applied to evaluate liver fibrosis. The expression level of α-SMA was measured by immunohistochemical (IHC). The expressions of lncRNA HOXA11-AS (HOXA11-AS), PTBP1, HDAC4, α-SMA, COL1A1 and Fibronectin were tested by qRT-PCR or Western blot. The commercial kits detected alanine aminotransferase (ALT) and aspartate aminotransferase (AST) concentrations in serum. Enzyme-linked immunosorbent assay (ELISA) measured TNF-α and IL-6 levels. The binding relationship between HOXA11-AS, PTBP1 and HDAC4 was verified by RNA immunoprecipitation (RIP). Our results showed that PRO alleviated liver fibrosis and the inflammation in IR-induced mice. PRO decreased the expression levels of HOXA11-AS, PTBP1 and HDAC4. Furthermore, HOXA11-AS overexpression abolished the protective effect of PRO against liver fibrosis in mice with IR-disposed. HOXA11-AS interacted with PTBP1 to regulate HDAC4 level and prevented its degradation in JS-1 cells. HDAC4 silencing eliminated the regulatory of HOXA11-AS overexpression on fibrosis and inflammation in IR-induced mice PRO inhibited HOXA11-AS expression to regulate HDAC4, thereby influencing liver fibrosis and inflammation induced by IR. It suggesting that PRO plays a protective role in liver fibrosis induced by ischemia-reperfusion in mice by regulating HOXA11-AS/PTBP1/HDAC4 axis.

Methylmercury (MeHg), an environmental pollutant, disrupts and impairs cellular function. MeHg binds to various cellular proteins, causing dysfunction and misfolding, which are considered underlying causes of MeHg toxicity. The p62 protein, also termed SQSTM1, is a ubiquitin-binding protein that targets ubiquitinated substrates to undergo autophagy and plays a key role in ameliorating MeHg toxicity. p62 also delivers ubiquitinated substrates to proteasomes. However, the role of these degradation systems in mitigating MeHg toxicity remains unknown. Herein, we explored the impact of the proteasome inhibitor MG132 on MeHg toxicity and examined the toxicity of co-treatment with MG132 and MeHg in p62KO mouse embryonic fibroblasts (MEFs) by analyzing cell viability, immunoblotting, mRNA levels, immunofluorescence, and the mercury content. The proteasome inhibitor MG132 enhanced MeHg-induced cytotoxicity while reducing intracellular mercury levels in MEFs. Co-treatment with MG132 and MeHg markedly increased levels of p62 and ubiquitinated proteins. Furthermore, co-treatment with MG132 and MeHg reduced p62KO MEF viability compared to that of wild-type MEFs. Our findings suggest that the proteasome participates in mitigating MeHg cytotoxicity, while p62 may play an important role in transporting MeHg-induced ubiquitinated proteins to the proteasome, as well as in autophagy. Collectively, these results imply that p62, and proteasome, and autophagy are vital for cytoprotection against MeHg toxicity.

The Short Time Exposure (STE) test evaluates eye irritation potential using a 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. MTT assays may underpredict results for some substances that directly reduce MTT (i.e., MTT reducers) or interfere with absorbance because of their strong color (i.e., strongly colored substances). Based on previous research, we selected 25 substances as MTT reducers. Of these, 13 were expected to be MTT reducers at 5% dilution (5% MTT reducers) of the STE test condition. These 13 substances were then tested to determine whether the results were interfered from direct MTT reduction. Those 5% MTT reducers that were classified as irritants based on in vivo data were identified as irritants by the STE test. In addition, the low cell viability results at 5% dilution suggested that direct MTT reduction had not occurred. Next, the remaining 5% MTT reducers that were classified as non-irritants based on in vivo data were identified as non-irritants by the STE test. We then examined two strongly colored substances. One was classified as an irritant based on in vivo data and was confirmed as an irritant by the STE test. The other was classified as a non-irritant by the STE test. This was further evaluated using a medium that did not contain MTT; the result indicated that it was a non-irritant correctly. In conclusion, the STE test is useful for evaluating eye irritation potential without the drawback of underprediction for MTT reducers and strongly colored substances.

Editor’s Announcement

In utero-exposed di(n-butyl) phthalate induce dose dependent, age-related changes of morphology and testosterone-biosynthesis enzymes/associated proteins of Leydig cell mitochondria in rats

Masaya Motohashi, Michael F. Wempe, Tomoko Mutou, Yuya Okayama, Norio Kansaku, Hiroyuki Takahashi, Masahiro Ikegami, Masao Asari, Shin Wakui

(The Journal of Toxicological Sciences, 41, 195-206, 2016)

I have retracted the above paper as Editor-in-Chief of The Journal of Toxicological Sciences since I have serious concerns about it, primarily due to inappropriate authorship on a non-negligible scale.

When it was brought to my attention that there was inappropriate authorship in this paper, I contacted the co-authors to confirm this point. I found out that the majority of them considered their listing as co-authors to be inappropriate. In addition, the majority agreed to the retraction of this paper.

These facts raise concerns about the paper. From the standpoint of maintaining the integrity of the research community, I felt that such a paper should be retracted at once.

Accordingly, I sent a summary of my concerns about the paper to the corresponding author, Dr. Shin Wakui. I also had an online interview with him to discuss this matter. I told Dr. Wakui that inappropriate authorship on a non-negligible scale is a serious problem that raises concerns about the paper.

I prepared a draft of this Editor’s Announcement and sent it to Dr. Wakui for review prior to revision and release. Although he did not agree to the retraction, I have decided to take this action from the standpoint of maintaining the integrity of the research community.

I coordinated my response to this issue with Dr. Akira Naganuma, Editor-in-Chief of Fundamental Toxicological Sciences, a sister journal of The Journal of Toxicological Sciences.

Toshiyuki Kaji, Ph.D.

Editor-in-Chief

The Journal of Toxicological Sciences