The effects of the continuous administration of N,N-dimethyl-4-phenylazoaniline (DAB) on the activities and the inducibilities of some drug-metabolizing enzymes in rat liver

The emerging role of microplastics in systemic toxicity: Involvement of reactive oxygen species (ROS)

Plastic pollution is one of the most pressing environmental threats the world is facing currently. The degradation of macroplastics into smaller forms viz. microplastics (MPs) or Nanoplastics (NPs) is a potential threat to both terrestrial and marine ecosystems and also to human health by directly affecting the organs and activating a plethora of intracellular signaling, that may lead to cell death. There is accumulating evidence that supports the serious toxicity caused by MP/NPs at all levels of biological complexities (biomolecules, organelles, cells, tissues, organs, and organ systems) and the involvement of the reactive oxygen species (ROS) in this process. Studies indicate that MPs or NPs can accumulate in mitochondria and further disrupt the mitochondrial electron transport chain, cause mitochondrial membrane damage, and perturb the mitochondrial membrane potential or depolarization of the mitochondria. These events eventually lead to the generation of different types of reactive free radicals, which can induce DNA damage, protein oxidation, lipid peroxidation, and compromization of the antioxidant defense pool. Furthermore, MP-induced ROS was found to trigger a plethora of signaling cascades, such as the p53 signaling pathway, Mitogen-activated protein kinases (MAPKs) signaling pathway including the c-Jun N-terminal kinases (JNK), p38 kinase, and extracellular signal related kinases (ERK1/2) signaling cascades, Nuclear factor erythroid 2-related factor 2 (Nrf2)-pathway, Phosphatidylinositol-3-kinases (PI3Ks)/Akt signaling pathway, and Transforming growth factor-beta (TGF-β) pathways, to name a few. As a consequence of oxidative stress caused by the MPs/NPs, different types of organ damage are observed in living species, including humans, such as pulmonary toxicity, cardiotoxicity, neurotoxicity, nephrotoxicity, immunotoxicity, reproductive toxicity, hepatotoxicity, etc. Although presently, a good amount of research is going on to access the detrimental effects of MPs/NPs on human health, there is a lack of proper model systems, multi-omics approaches, interdisciplinary research, and mitigation strategies.

Study protocol of a phase IB/II clinical trial of metformin and chloroquine in patients with IDH1-mutated or IDH2-mutated solid tumours

INTRODUCTION

High-grade chondrosarcoma, high-grade glioma and intrahepatic cholangiocarcinoma are aggressive types of cancer with a dismal outcome. This is due to the lack of effective treatment options, emphasising the need for novel therapies. Mutations in the genes IDH1 and IDH2 (isocitrate dehydrogenase 1 and 2) occur in 60% of chondrosarcoma, 80% of WHO grade II-IV glioma and 20% of intrahepatic cholangiocarcinoma. IDH1/2-mutated cancer cells produce the oncometabolite D-2-hydroxyglutarate (D-2HG) and are metabolically vulnerable to treatment with the oral antidiabetic metformin and the oral antimalarial drug chloroquine.

METHODS AND ANALYSIS

We describe a dose-finding phase Ib/II clinical trial, in which patients with IDH1/2-mutated chondrosarcoma, glioma and intrahepatic cholangiocarcinoma are treated with a combination of metformin and chloroquine. Dose escalation is performed according to a 3+3 dose-escalation scheme. The primary objective is to determine the maximum tolerated dose to establish the recommended dose for a phase II clinical trial. Secondary objectives of the study include (1) determination of pharmacokinetics and toxic effects of the study therapy, for which metformin and chloroquine serum levels will be determined over time; (2) investigation of tumour responses to metformin plus chloroquine in IDH1/2-mutated cancers using CT/MRI scans; and (3) whether tumour responses can be measured by non-invasive D-2HG measurements (mass spectrometry and magnetic resonance spectroscopy) of tumour tissue, serum, urine, and/or bile or next-generation sequencing of circulating tumour DNA (liquid biopsies). This study may open a novel treatment avenue for IDH1/2-mutated high-grade chondrosarcoma, glioma and intrahepatic cholangiocarcinoma by repurposing the combination of two inexpensive drugs that are already approved for other indications.

ETHICS AND DISSEMINATION

This study has been approved by the medical-ethical review committee of the Academic Medical Center, Amsterdam, The Netherlands. The report will be submitted to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

This article was registered at ClinicalTrials.gov identifier (NCT02496741): Pre-results.

Molecular aspects and chemoprevention of dimethylaminoazobenzene-induced hepatocarcinogenesis: A review

The lipophilic azo dye dimethylaminoazobenzene (DAB) is a potent hepatocarcinogen accounted as a group-2B carcinogen causing risk to humans. DAB is commonly used as a coloring agent in food, pharmaceuticals, beverages, soap and polishes. The exploration of DAB-induced hepatocarcinogenesis in animal models helped to an extent to perceive the histological, biochemical and molecular mechanisms of DAB carcinogenesis and also the severity of DAB exposure to humans. In experimental animal models, it is well-proved that the procarcinogen DAB is predominantly metabolized by cytochrome P450 enzymes giving rise to the formation of toxic electrophiles and reactive oxygen species (ROS), which further forms DNA adducts leading to the development of hepatic tumors. Recently, research evidence suggests that dietary phytochemicals and plant polyphenols are promising agents to control the incidence of DAB-induced hepatocarcinogenesis by preventing the generation of toxic electrophiles and ROS thereby inhibiting the formation of DNA adducts. This review highlights the role of specific dietary factors, biotransformation of DAB, phenotypic and genotypic alterations, and significance of certain chemopreventive agents against DAB-induced hepatocarcinogenesis.

Some characteristics of two azoreductase systems in rat liver. Relevance to the activity of 2-[4'-di(2"-bromopropyl)-aminophenylazo]benzoic acid (CB10-252), a compound possessing latent cytotoxic activity

The system involved in the reduction of 2-[4'-di(2''-bromopropyl) aminophenylazolbenzoic acid (CB10-252), an agent designed for treating primary liver cell cancer, has been demonstrated to be localised mainly in the 108 000 X g supernatant fraction of rat liver homogenate. It is also present in other organs particularly in the spleen. DAB-azoreductase as shown previously is present almost entirely in the microsomal fraction and is found in high concentration only in liver. The pH maximum for CB10-252-azoreductase implying the importance of the 2'-carboxyl group in determining substrate specificity. The use of enzyme inhibitors and other additives showed that CB10-252 WAS NOT AXANTHINE OXIDASE OR DIHYDROFOLATE REDUCTASE. Its activity was not affected by carbon monoxide, phenobarbitone (PB), or 3-methylcholanthrene (MC) pretreatment. Enhancement of the activity by ferrous ions and FAD indicated that at least part of the reduction system could involve a flavoprotein with FAD as the prosthetic group. The activity of CB10-252-azoreductase and methylred-azoreductase was reduced by menadione (vitamin K3), cyanide and propylgallate. A diaphorase preparation from pig heart reduced both CB10-252 and methylred with both NADPH- and NADH-generating systems.