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Abstract: The broad application of paraquat (PQ) has given rise to wide public concern over its potential to damage the nigrostriatal dopaminergic system because its chemical structure closely resembles that of the well-known dopaminergic neurotoxicant MPP+. However, little is known about the relevance of dopamine homeostasis changes in response to PQ exposure as the underlying mechanism of the neurotoxicity. We used the PC12 cell, a popular in vitro cell model system for characterizing the dopaminergic neuron to examine the effects of PQ on dopamine homeostasis. After 24h treatment with different concentrations of PQ (from 0 to 1000μmol/l), MTT tests showed that cell viability decreased with increasing PQ concentrations. Flow cytometry analysis also showed that PQ induced cell apoptosis in a dose-dependent manner. An enzyme-linked immunosorbent assay revealed that the intracellular dopamine content increased after PQ treatment. The mRNA expression of genes associated with dopamine synthesis (TH), storage (VMAT2), transportation (DAT and D2R) and degradation (MAO) was assessed using real-time PCR. Results showed that the expression of TH and COMT were unaffected while the expression of MAO was suppressed after PQ treatment. In addition, exposure to PQ reduced the expression of VMAT2 but up-regulated the expression of D2R. Moreover, the expression of DAT was up-regulated at a lower dose of PQ, and then decreased at a higher dose. These alterations of gene expression of MAO, D2R and DAT are consistent with an increase of intracellular dopamine content. Together, these findings suggest that PQ exposure can influence dopamine homeostasis, which may be partly related to the neurotoxicity of PQ. [Copyright &y& Elsevier]

Abstract Both epidemiological investigations and animal studies have linked arsenic-contaminated water to cancers, including skin, liver and lung cancers. Besides genotoxicity, arsenic exposure-related pathogenesis of disease is widely considered through epigenetic mechanisms; however, the underlying mechanism remains to be determined. Herein we explore the initial epigenetic changes via acute sodium arsenite (As) exposures of mouse embryonic fibroblast (MEF) cells and histone H3K79 methyltransferase Dot1L knockout (Dot1L−/−) MEF cells. Our RNA-seq and Western blot data demonstrated that, in both cell lines, acute As exposure abolished histone acetyltransferase p300 at the RNA level and subsequent protein level. Consequently, p300-specific main target histone H3K27ac, a marker separating active from poised enhancers, decreased dramatically as validated by both Western blot and ChIP-qPCR/seq analyses. Concomitantly, H3K4me1 as another well-known marker for enhancers also showed significant decreases, suggesting an underappreciated crosstalk between H3K4me1 and H3K27ac involved in As exposure. Significantly, As exposure-reduced H3K27ac and H3K4me1 inhibited the expression of genes including EP300 itself and Kruppel Like Factor 4(Klf4) that both are tumor suppressor genes. Collectively, our investigations identified p300 as an internal bridging factor within cells to sense external environmental As exposure to alter chromatin, thereby changing gene transcription for disease pathogenesis. Highlights • Acuate arsenite exposure abolished histone acetyltransferase p300. • A crosstalk between H3K4me1 and H3K27ac involved in arsenite exposure. • Attenuated H3K27ac and H3K4me1 repressed the expression of tumor suppressor genes upon arsenite exposure. [ABSTRACT FROM AUTHOR]

Abstract Mitochondrial dysfunction is considered as a critical mechanism in the pathogenesis of Parkinson's disease (PD). Increasing evidence supports the notion of mitochondria-associated membranes (MAMs) in mitochondrial dysfunction; yet little is known about the role of MAMs-related proteins in the pathogenesis of PD. Herein we exposed the nematode Caenorhabditis elegans to 0.5–10.0 μM rotenone (RO) or 0.2–1.6 mM paraquat (PQ) for 3 days. Our results showed that both RO and PQ induced similar Parkinsonism including motor deficits and dopaminergic degeneration. RO/PQ caused mitochondrial damages characterized by the increase of vacuole areas and autophagy vesicles, but the decrease of mitochondrial cristae. RO/PQ-impacted mitochondrial function was also demonstrated by the decrease of ATP level and mitochondrial membrane potential. Additionally, the attachment or surrounding of endoplasmic reticulum to the damaged mitochondria indicates ultrastructural alterations in MAMs. Using fluorescently labeled transgenic nematodes, we further found that the expression of tomm-7 and genes of Complex I, II and III was reduced, whereas the expression of pink-1 was increased in the exposed animals. To determine MAMs in toxicity toward PD, we investigated the mutants of hop-1 and pink-1 , encoding presenilin and PTEN-induced putative kinase 1 (PINK1) in mitochondria-associated membranes, respectively. Results demonstrated that the mutation of both hop-1 and pink-1 reduced the vulnerability of lethal, behavioral, and mitochondrial toxicity induced by RO/PQ. These findings suggest that presenilin and PINK1 play important roles in the RO/PQ-induced neurotoxicity through the mechanisms involved in mitochondria-associated membranes. Highlights • Rotenone (RO) and paraquat (PQ) induced Parkinsonism in Caenorhabditis elegans. • RO/PQ caused mitophagy and mitochondria-associated membrane (MAM) damages. • RO/PQ reduced tomm-7 and Complex I, II, III gene, but increased pink-1 expression. • Mutation of hop-1 and pink-1 reduced vulnerability of RO/PQ-induced toxicity. • Presenilin and PINK1 play key roles in Parkinsonism-related toxicity through MAMs. [ABSTRACT FROM AUTHOR]

Abstract: Rab GTPases, which belong to the Ras superfamily, represent a group of small molecular weight GTP binding proteins that are involved in various steps along the exocytic and endocytic pathways. We first identified mRabL5 (GenBank Accession No. NP_080349), a novel Mus musculus Rab-like protein, present as a Golgi-associated protein. Here we presented the results of the cloning, prokaryotic expression, purification, and polyclonal antibody production of the novel Rab-like protein. In order to obtain a specific antibody against mRabL5, we prepared two GST fusion proteins, full-length mRabL5 GST fusion protein and mRabL5 C terminus GST fusion protein, to immunize rabbits. Western blot analysis showed that both antibodies prepared against full length of mRabL5 and its C terminus, respectively, can recognize mRabL5 protein. Immunofluorescence of mRabL5 in NIH3T3 cells using the two antibodies showed its perinuclear clustering distribution pattern. The polyclonal antibodies preparation against mRabL5 provided a good tool for us to study the functional involvement of mRabL5. [Copyright &y& Elsevier]