HRG-9 homologues regulate haem trafficking from haem-enriched compartments.

Haem is an iron-containing tetrapyrrole that is critical for a variety of cellular and physiological processes1-3. Haem binding proteins are present in almost all cellular compartments, but the molecular mechanisms that regulate the transport and use of haem within the cell remain poorly understood2,3. Here we show that haem-responsive gene 9 (HRG-9) (also known as transport and Golgi organization 2 (TANGO2)) is an evolutionarily conserved haem chaperone with a crucial role in trafficking haem out of haem storage or synthesis sites in eukaryotic cells. Loss of Caenorhabditis elegans hrg-9 and its paralogue hrg-10 results in the accumulation of haem in lysosome-related organelles, the haem storage site in worms. Similarly, deletion of the hrg-9 homologue TANGO2 in yeast and mammalian cells induces haem overload in mitochondria, the site of haem synthesis. We demonstrate that TANGO2 binds haem and transfers it from cellular membranes to apo-haemoproteins. Notably, homozygous tango2-/- zebrafish larvae develop pleiotropic symptoms including encephalopathy, cardiac arrhythmia and myopathy, and die during early development. These defects partially resemble the symptoms of human TANGO2-related metabolic encephalopathy and arrhythmias, a hereditary disease caused by mutations in TANGO24-8. Thus, the identification of HRG-9 as an intracellular haem chaperone provides a biological basis for exploring the aetiology and treatment of TANGO2-related disorders.

8:2 Fluorotelomer alcohol causes G1 cell cycle arrest and blocks granulocytic differentiation in HL-60 cells.

Fluorotelomer alcohols (FTOHs) are fluorinated intermediates used in manufacturing specialty polymer and surfactants, with 8:2 FTOH the homologue of largest production. FTOHs were found to pose acute toxicity, hepatotoxicity, nephrotoxicity, developmental toxicity and endocrine-disrupting risks, whereas research regarding immunotoxicity and its underlying mechanism, especially on specific immune cells is limited. Here, we investigated the immunotoxicity of 8:2 FTOH on immature immune cells in an in vitro system. We observed that exposure of HL-60 cells, a human promyelocytic leukemic cell line, to 8:2 FTOH reduced cell viability in a dose- and time-dependent manner. In addition, 8:2 FTOH exposure caused G1 cell cycle arrest in HL-60 cells, while it showed no effect on apoptosis. Exposure to 8:2 FTOH inhibited the mRNA expression of cell cycle-related genes, including CCNA1, CCNA2, CCND1, and CCNE2. Moreover, exposure to 8:2 FTOH inhibited the mRNA expression of granulocytic differentiation-related genes of CD11b, CSF3R, PU.1, and C/EPBε in HL-60 cells . Furthermore, 8:2 FTOH exhibited no effect on intracellular ROS level, while hydralazine hydrochloride (Hyd), one reactive carbonyl species (RCS) scavenger, partially blocked 8:2 FTOH-caused cytotoxicity in HL-60 cells. Overall, the results obtained in the study show that 8:2 FTOH poses immunotoxicity in immature immune cells and RCS may partially underline its mechanism.

ß-Cypermethrin and its metabolite 3-phenoxybenzoic acid exhibit immunotoxicity in murine macrophages.

ß-Cypermethrin (ß-CYP), one of most important pyrethroids, is widely used to control insects, and has been detected in organisms, including human. Pyrethroids have been shown to pose neurotoxicity, hepatotoxicity, endocrine disruption and reproductive risks in mammals. However, research in immunotoxicity of pyrethroids, especially their metabolites, is limited. A common metabolite of pyrethroids is 3-phenoxybenzoic acid (3-PBA) in mammals. Thus, in this study, we evaluated the immunotoxicity of ß-CYP and 3-PBA in mouse macrophages, RAW 264.7 cells. MTT assays showed that both ß-CYP and 3-PBA reduced cell viability in a concentration- and time-dependent manner. Flow cytometry with Annexin-V/PI staining demonstrated that both ß-CYP and 3-PBA induced RAW 264.7 cell apoptosis. Furthermore, our results also showed that N-acetylcysteine partially blocked ß-CYP- and 3-PBA-induced cytotoxicity and apoptosis. Intrinsic apoptotic pathway was stimulated by both ß-CYP and 3-PBA exposure. In addition, we found that ß-CYP and 3-PBA inhibited mRNA levels of pro-inflammatory cytokines with or without LPS stimulation. Phagocytosis assay showed that both ß-CYP and 3-PBA inhibited phagocytic ability of macrophages. Moreover, it was also found that both ß-CYP and 3-PBA increased reactive oxygen species (ROS) levels in RAW 264.7 cells. Accordingly, both ß-CYP and 3-PBA were found to regulate the mRNA levels of oxidative stress-related genes in RAW 264.7 cells. Taken together, the results obtained in this study demonstrated that ß-CYP and 3-PBA may have immunotoxic effect on macrophages and that elevated ROS may underlie the mechanism. The present study will help to understand the health risks caused by ß-CYP and other pyrethroids.