Low-Concentration Tributyltin Decreases GluR2 Expression via Nuclear Respiratory Factor-1 Inhibition.

Tributyltin (TBT), which has been widely used as an antifouling agent in paints, is a common environmental pollutant. Although the toxicity of high-dose TBT has been extensively reported, the effects of low concentrations of TBT are relatively less well studied. We have previously reported that low-concentration TBT decreases α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptor subunit 2 (GluR2) expression in cortical neurons and enhances neuronal vulnerability to glutamate. However, the mechanism of this TBT-induced GluR2 decrease remains unknown. Therefore, we examined the effects of TBT on the activity of transcription factors that control GluR2 expression. Exposure of primary cortical neurons to 20 nM TBT for 3 h to 9 days resulted in a decrease in GluR2 mRNA expression. Moreover, TBT inhibited the DNA binding activity of nuclear respiratory factor-1 (NRF-1), a transcription factor that positively regulates the GluR2. This result indicates that TBT inhibits the activity of NRF-1 and subsequently decreases GluR2 expression. In addition, 20 nM TBT decreased the expression of genes such as cytochrome c, cytochrome c oxidase (COX) 4, and COX 6c, which are downstream of NRF-1. Our results suggest that NRF-1 inhibition is an important molecular action of the neurotoxicity induced by low-concentration TBT.

Bioequivalence Evaluations of Generic Dry Powder Inhaler Drug Products: Similarities and Differences Between Japan, USA, and the European Union.

In Japan, the development of generic oral dry powder inhaler (DPI) drug products for marketing approval has recently increased. The Pharmaceuticals and Medical Devices Agency (PMDA) considers the required data for each drug product in the consultation meeting. However, guidelines for DPI drug products have been published by the US Food and Drug Administration and the European Medicines Agency. Recently, the basic principles of bioequivalence evaluations of generic DPI drug products were published in March 2016 by the Ministry of Health, Labour and Welfare. The document mainly outlines the current understanding regarding the bioequivalence evaluations of generic DPI drug products based on knowledge from PMDA consultation meetings. In this review, we compared the bioequivalence evaluations of DPI drug products among Japan, USA, and the European Union and discuss future development of generic DPI drug products in Japan.

Similarities and Differences of International Practices and Procedures for the Regulation for Active Substance Master Files/Drug Master Files of Human Use: Moving Toward Regulatory Convergence.

PURPOSE: A gap analysis survey of international practices for Active Substance Master Files (ASMFs)/Drug Master Files (DMFs) of human use was conducted as a project of the ASMF/DMF working group of the International Generic Drug Regulators Pilot (IGDRP) to identify similarities and differences among ASMF/DMF procedures of 10 IGDRP members and 2 observers. METHODS: We conducted a questionnaire survey and compared the following aspects: overall ASMF/DMF procedures, submission requirements for ASMFs/DMFs, assessment processes for ASMFs/DMFs, the technical requirements for active pharmaceutical ingredients (APIs), generation of assessment reports for ASMFs/DMFs, procedures for changing ASMF/DMF details, and Good Manufacturing Practice (GMP) inspection/certification of API manufacturers. Twelve organizations participated in this project: the Brazilian Health Surveillance Agency (Anvisa), the European Union (EU), Health Canada (HC), the Singapore Health Sciences Authority (HSA), the South African Medicines Control Council (MCC), the South Korean Ministry of Food and Drug Safety (MFDS), the Japanese Pharmaceuticals and Medical Devices Agency (PMDA), the Swiss Agency for Therapeutic Products (Swissmedic), the Taiwan Food and Drug Administration (TFDA), the Australian Therapeutic Goods Administration (TGA), the European Directorate for the Quality of Medicines & HealthCare (EDQM) (Observer) and the Prequalification Team (PQT) of the World Health Organization (WHO), which includes the PQT-Medicines (Observer). RESULTS: Although there were many similarities among the participating agencies surveyed, there were also differences that should be discussed such as assessment processes of ASMFs/DMFs and Technical requirements for APIs. CONCLUSIONS: These differences revealed by this survey will be key considerations in order to facilitate the filing of ASMFs/DMFs globally and to establish a framework for sharing and utilizing information related to ASMFs/DMFs among IGDRP members in the future. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Regulatory Considerations of Bioequivalence Studies for Oral Solid Dosage Forms in Japan.

Bioequivalence (BE) studies are used to infer the therapeutic equivalence of generic drug products to original drug products throughout the world. In BE studies, bioavailability (BA) should be compared between the original and generic drug products, with BA defined as the rate and extent of absorption of active pharmaceutical ingredients or active metabolites from a product into the systemic circulation. For most of BE studies conducted during generic drug development, BA comparisons are performed in single-dose studies. In Japan, the revised "Guideline for Bioequivalence Studies of Generic Products" was made available in 2012 by the Ministry of Health, Labour, and Welfare, and generic drug development is currently conducted based on this guideline. Similarly, the U.S. Food and Drug Administration and European Medicines Agency have published guidance and guideline on generic drug development. This article introduces the guideline on Japanese BE studies for oral solid dosage forms and the dissolution tests for the similarity and equivalence evaluation between the original and generic drug products. Additionally, we discuss some of the similarities and differences in guideline between Japan, the United States, and the European Union.

Long-term exposure to endogenous levels of tributyltin decreases GluR2 expression and increases neuronal vulnerability to glutamate.

Tributyltin (TBT), an endocrine-disrupting chemical, has been used commercially as a heat stabilizer, agricultural pesticide and component of antifouling paints. In this study, we investigated the effect of long-term exposure to endogenous levels of TBT on neuronal glutamate receptors. Cultured rat cortical neurons were exposed to 1-50 nM TBT for 9 days (from day 2 to day 10 in vitro). The number of neurons was reduced by long-term exposure to 50 nM TBT, but not to 1-20 nM TBT. Long-term exposure to 20 nM TBT decreased the mRNA expression of glutamate receptors NR1, NR2A, GluR1 and GluR2, and increased that of NR2B, GluR3 and GluR4. GluR2 protein was also reduced by long-term exposure to TBT. Because AMPA receptor lacking GluR2 exhibits Ca2+ permeability, we investigated whether Ca2+ influx or glutamate toxicity was affected. Indeed, glutamate-induced Ca2+ influx was increased in TBT-treated neurons. Consistent with this, neurons became more susceptible to glutamate toxicity as a result of long-term exposure to TBT and this susceptibility was abolished by an antagonist of GluR2-lacking AMPA receptor. Thus, it is suggested that long-term exposure to endogenous levels of TBT induces a decrease of GluR2 protein, causing neurons become more susceptible to glutamate toxicity.