NAC antagonizes arsenic-induced neurotoxicity through TMEM179 by inhibiting oxidative stress in Oli-neu cells

Arsenic is one of the most common environmental pollutants. Neurotoxicity induced by arsenic has become a major public health concern. However, the effects of arsenic-induced neurotoxicity in the brain and the underlying molecular mechanisms are not well understood. N-acetyl-cysteine (NAC) is a thiol-based antioxidant that can antagonize heavy metal-induced neurotoxicity by scavenging reactive oxygen species (ROS). Here, we used the mouse oligodendrocyte precursor cell (OPC) line Oli-neu to explore the neurotoxic effects of arsenic and the protective effects of NAC. We found that arsenic exposure decreased cell viability, increased oxidative stress, caused mitochondrial dysfunction, and led to apoptosis of Oli-neu cells. Furthermore, we revealed that NAC treatment reversed these neurotoxic effects of arsenic. TMEM179, a key membrane protein, was found highly expressed in OPCs and to be an important factor in maintaining mitochondrial functions. We found that TMEM179 played a critical role in mediating the neurotoxic effects of arsenic and the protective role of NAC. PKCβ is a downstream factor through which TMEM179 regulates the expression of apoptosis-related proteins. This study improves our understanding of the neurotoxic effects and mechanisms of arsenic exposure and the protective effects of NAC. It also identifies a potential molecular target, TMEM179, for the treatment of arsenic-induced neurotoxicity.

Oxidative stress, lysosomal damage and dysfunctional autophagy in molluscan hepatopancreas (digestive gland) induced by chemical contaminants

Autophagy is a highly conserved evolutionary survival or defence process that enables cells and organisms to survive periods of environmental stress by breaking down cellular organelles and macromolecules in autolysosomes to provide a supply of nutrients for cell maintenance. However, autophagy is also a part of normal cellular physiology that facilitates the turnover of cellular constituents under normal conditions: it can be readily augmented by mild environmental stress; but becomes dysfunctional with severe oxidative stress leading to cellular pathology. The molluscan hepatopancreas or digestive gland provides a versatile and environmentally relevant model to investigate lysosomal autophagy and stress-induced dysfunctional autophagy. This latter process has been implicated in many animal and human disease conditions, including degenerative and neurodegenerative diseases, as well as obesity related conditions. Many environmental pollutants have also been found to induce dysfunctional autophagy in molluscan hepatopancreatic digestive cells, and in this study, the marine blue mussel Mytilus galloprovincialis was exposed for 7 days to: 0.1 μM, 1 μM and 10 μM concentrations of fluoranthene and phenanthrene (PAHs); chlorpyrifos and malathion (organophosphorus compounds); atrazine (triazine herbicide); copper (transition metal) and dodecylbenzene sulphonic acid (LAS, surfactant). The marine snail or periwinkle, Littorina littorea, was also exposed to phenanthrene, chlorpyrifos and copper. Indices of oxidative stress, cell injury and dysfunctional autophagy were measured (i.e., lysosomal membrane stability, protein carbonyls, lipofuscin, and lysosomal accumulation of lipid or lipidosis). Evidence of oxidative stress, based on the elevation of lipofuscin and protein carbonyls, was found for all compounds tested; with chlorpyrifos being the most toxic to both species. Dysfunctional autophagy was induced by all of the compounds tested in both species, except for atrazine in mussels. This failure of normal autophagy was consistently associated with oxidative stress. Autophagic dysfunction is an important emerging feature in the aetiology of many disease conditions in animals and humans; and an explanatory conceptual mechanistic model has been developed for dysregulation of autophagy in response to oxidative stress.

Analysis of variants and mutations in the human winged helix FOXA3 gene and associations with metabolic traits

BACKGROUND/OBJECTIVES

The forkhead factor Foxa3 is involved in the early transcriptional events controlling adipocyte differentiation and plays a critical function in fat depot expansion in response to high-fat diet regimens and during aging in mice. No studies to date have assessed the potential associations of genetic variants in FOXA3 with human metabolic outcomes.

SUBJECTS/METHODS

In this study, we sequenced FOXA3 in 392 children, adolescents and young adults selected from several cohorts of subjects recruited at the National Institute of Child Health and Human Development of the National Institutes of Health based on the availability of dual-energy X-ray absorptiometry data, magnetic resonance imaging scans and DNA samples. We assessed the association between variants present in these subjects and metabolic traits and performed in vitro functional analysis of two novel FOXA3 missense mutations identified.

RESULTS

Our analysis identified 14 novel variants and showed that the common single-nucleotide polymorphism (SNP) rs28666870 is significantly associated with greater body mass index, lean body mass and appendicular lean mass (P values 0.009, 0.010 and 0.013 respectively). In vitro functional studies showed increased adipogenic function for the FOXA3 missense mutations c.185C>T (p.Ser62Leu) and c.731C>T (p.Ala244Val) compared with FOXA3-WT.

CONCLUSIONS

Our study identified novel FOXA3 variants and mutations, assessed the adipogenic capacity of two novel missense alterations in vitro and demonstrated for the first time the associations between FOXA3 SNP rs28666870 with metabolic phenotypes in humans.

Brain-derived neurotrophic factor in human subjects with function-altering melanocortin-4 receptor variants

Background

In rodents, hypothalamic brain-derived neurotrophic factor (BDNF) expression appears to be regulated by melanocortin-4 receptor (MC4R) activity. The impact of MC4R genetic variation on circulating BDNF in humans is unknown.

Objective

To compare BDNF concentrations of subjects with loss-of-function (LOF) and gain-of-function (GOF) MC4R variants to those of controls with common sequence MC4R.

Methods

Circulating BDNF was measured in two cohorts with known MC4R sequence: 148 subjects of Pima Indian heritage ([mean±SD]: age 15.7±6.5y, BMI-Z 1.63±1.03), and 69 subjects of Hispanic heritage (10.8±3.6y, BMI-Z 1.57±1.07). MC4R variants were characterized in vitro by cell surface expression, receptor binding, and cAMP response after agonist administration. BDNF single nucleotide polymorphisms (SNPs) rs12291186, rs6265, and rs7124442 were also genotyped.

Results

In the Pima cohort, no significant differences in serum BDNF was observed for 43 LOF-subjects versus 65 LOF-matched controls [age-, sex-, and BMI-matched] (P=0.29), or 20 GOF-subjects versus 20 GOF-matched controls (P=0.40). Serum BDNF was significantly associated with genotype for BDNF rs12291186 (P=0.006) and rs6265 (P=0.009), but not rs7124442 (P=0.99); BDNF SNPs did not interact with MC4R status to predict serum BDNF. In the Hispanic cohort, plasma BDNF was not significantly different among 21 LOF-subjects, 20 GOF-subjects, and 28 controls (P=0.79); plasma BDNF was not predicted by BDNF genotype or BDNF-x-MC4R genotype interaction.

Conclusions

Circulating BDNF concentrations were not significantly associated with MC4R functional status, suggesting that peripheral BDNF does not directly reflect hypothalamic BDNF secretion and/or that MC4R signaling is not a significant regulator of the bulk of BDNF expression in humans.

Association between TIM-1 gene polymorphisms and allergic rhinitis in a Han Chinese population

BACKGROUND

TIM-1, a member of the T cell immunoglobulin and mucin (TIM) domain family, is involved in T-cell differentiation and has been implicated in allergic diseases. An association between TIM-1 and allergic rhinitis, however, has not been established.

OBJECTIVE

To investigate whether TIM-1 gene polymorphisms were associated with allergic rhinitis in a Han Chinese population.

METHODS

Two TIM-1 promoter single nucleotide polymorphisms (SNPs), -416G>C and -1454G>A, were examined in 185 allergic rhinitis patients of Han Chinese ethnicity using polymerase chain reaction (PCR) and restriction fragment length polymorphism. Additionally, exon 4 insertion/deletion polymorphisms in the TIM-1 gene were analyzed by PCR, polyacrylamide gel electrophoresis, and silver staining. The relationship between gene polymorphisms and serum specific IgE levels in this Han Chinese population was also evaluated.

RESULTS

We found that the -416G>C and -1454G>A SNPs were associated with allergic rhinitis susceptibility in this Han Chinese population. No statistically significant differences in the distribution of genotype or allele frequencies of 5383_5397ins/del and 5509_5511delCAA in exon 4 were observed. The -416G>C and -1454G>A SNPs were associated with the level of serum IgE specific to house dust mites in patients with allergic rhinitis.

CONCLUSIONS

These results suggest that TIM-1 gene polymorphisms (-416G>C and -1454G>A) are associated with allergic rhinitis susceptibility in a Han Chinese population.

[Expression of alpha and beta subunit isoforms of Na, K-ATPase in the guinea pig endolymphatic sac]

OBJECTIVE

To investigate the expression and significance of alpha and beta subunit isoforms of Na, K-ATPase in the guinea pig endolymphatic sac.

METHODS

The distribution of alpha and beta subunit isoforms of Na, K-ATPase in endolymphatic sac of guinea pig was identified by immunocytochemistry and in situ hybridization.

RESULTS

The expression of Na, K-ATPase alpha and beta subunit isoforms varied among different cell regions of the endolymphatic sac. Epithelial cells of the endolymphatic sac were observed to contain the alpha 1, beta 1 and beta 2 subunit isoforms, and the expression of beta 2 was stronger than that of beta 1. Subepithelial cells contained alpha 1 and alpha 2 subunit isoforms and the expression of alpha 1 was stronger than that of alpha 2. No expression of alpha 3 subunit isoform was observed in endolymphatic sac.

CONCLUSION

Na, K-ATPase of endolymphatic sac consists of different alpha and beta subunit isoforms which, working in concert, serve to maintain homeostasis in inner ear.

Deficiency in fatty acid synthase leads to premature cell death and dramatic alterations in plant morphology

An Arabidopsis mosaic death1 (mod1) mutant, which has premature cell death in multiple organs, was isolated. mod1 plants display multiple morphological phenotypes, including chlorotic and curly leaves, distorted siliques, premature senescence of primary inflorescences, reduced fertility, and semidwarfism. The phenotype of the mod1 mutant results from a single nuclear recessive mutation, and the MOD1 gene was isolated by using a map-based cloning approach. The MOD1 gene encodes an enoyl-acyl carrier protein (ACP) reductase, which is a subunit of the fatty acid synthase complex that catalyzes de novo synthesis of fatty acids. An amino acid substitution in the enoyl-ACP reductase of the mod1 mutant causes a marked decrease in its enzymatic activity, impairing fatty acid biosynthesis and decreasing the amount of total lipids in mod1 plants. These results demonstrate that a deficiency in fatty acid biosynthesis has pleiotropic effects on plant growth and development and causes premature cell death.

Deficiency in fatty acid synthase leads to premature cell death and dramatic alterations in plant morphology

An Arabidopsis mosaic death1 (mod1) mutant, which has premature cell death in multiple organs, was isolated. mod1 plants display multiple morphological phenotypes, including chlorotic and curly leaves, distorted siliques, premature senescence of primary inflorescences, reduced fertility, and semidwarfism. The phenotype of the mod1 mutant results from a single nuclear recessive mutation, and the MOD1 gene was isolated by using a map-based cloning approach. The MOD1 gene encodes an enoyl-acyl carrier protein (ACP) reductase, which is a subunit of the fatty acid synthase complex that catalyzes de novo synthesis of fatty acids. An amino acid substitution in the enoyl-ACP reductase of the mod1 mutant causes a marked decrease in its enzymatic activity, impairing fatty acid biosynthesis and decreasing the amount of total lipids in mod1 plants. These results demonstrate that a deficiency in fatty acid biosynthesis has pleiotropic effects on plant growth and development and causes premature cell death.

[mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs]

OBJECTIVE

To detect the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs.

METHODS

After consulting gene bank, we analyzed conservative sequence of hyaluronan synthases in different species, detected the mRNA expression of hyaluronan synthase in the endolymphatic sac cells of guinea pigs with oligonucleotide probe by hybridization in situ.

RESULTS

mRNA of hyaluronan synthase was strongly expressed in some epithelial cells of endolymphatic sac, coupled with negative expression in negative control groups.

CONCLUSION

It confirms that endolymphatic sac cells can synthesize hyaluronan.