A Low Selenium Level Is Associated with Lung and Laryngeal Cancers

Purpose

It has been suggested that selenium deficiency is a risk factor for several cancer types. We conducted a case-control study in Szczecin, a region of northwestern Poland, on 95 cases of lung cancer, 113 cases of laryngeal cancer and corresponding healthy controls.

Methods

We measured the serum level of selenium and established genotypes for four variants in four selenoprotein genes (GPX1, GPX4, TXNRD2 and SEP15). Selenium levels in the cases were measured after diagnosis but before treatment. We calculated the odds of being diagnosed with lung or laryngeal cancer, conditional on selenium level and genotype.

Results

Among lung cancer cases, the mean selenium level was 63.2 µg/l, compared to a mean level of 74.6 µg/l for their matched controls (p<0.0001). Among laryngeal cancer cases, the mean selenium level was 64.8 µg/l, compared to a mean level of 77.1 µg/l for their matched controls (p<0.0001). Compared to a serum selenium value below 60 µg/l, a selenium level above 80 µg/l was associated with an odds ratio of 0.10 (95% CI 0.03 to 0.34; p = 0.0002) for lung cancer and 0.23 (95% CI 0. 09 to 0.56; p = 0.001) for laryngeal cancer. In analysis of four selenoprotein genes we found a modest evidence of association of genetic variant in GPX1 with the risk of lung and laryngeal cancers.

Conclusion

A selenium level below 60 µg/l is associated with a high risk of both lung and laryngeal cancer.     

Polymorphism analysis of six selenoprotein genes: support for a selective sweep at the glutathione peroxidase 1 locus (3p21) in Asian populations

Background

There are at least 25 human selenoproteins, each characterized by the incorporation of selenium into the primary sequence as the amino acid selenocysteine. Since many selenoproteins have antioxidant properties, it is plausible that inter-individual differences in selenoprotein expression or activity could influence risk for a range of complex diseases, such as cancer, infectious diseases as well as deleterious responses to oxidative stressors like cigarette smoke. To capture the common genetic variants for 6 important selenoprotein genes (GPX1, GPX2, GPX3, GPX4, TXNRD1, and SEPP1) known to contribute to antioxidant host defenses, a re-sequence analysis was conducted across these genes with particular interest directed at the coding regions, intron-exon borders and flanking untranslated regions (UTR) for each gene in an 102 individual population representative of 4 major ethnic groups found within the United States.

Results

For 5 of the genes there was no strong evidence for selection according to the expectations of the neutral equilibrium model of evolution; however, at the GPX1 locus (3p21) there was evidence for positive selection. Strong confirmatory evidence for recent positive selection at the genomic region 3p21 in Asian populations is provided by data from the International HapMap project.

Conclusion

The SNPs and fine haplotype maps described in this report will be valuable resources for future functional studies, for population specific genetic studies designed to comprehensively explore the role of selenoprotein genetic variants in the etiology of various human diseases, and to define the forces responsible for a recent selective sweep in the vicinity of the GPX1 locus.     

Genetic polymorphism in selenoprotein P modifies the response to selenium-rich foods on blood levels of selenium and selenoprotein P in a randomized dietary intervention study in Danes

Background

Selenium is an essential trace element and is suggested to play a role in the etiology of a number of chronic diseases. Genetic variation in genes encoding selenoproteins, such as selenoprotein P and the glutathione peroxidases, may affect selenium status and, thus, individual susceptibility to some chronic diseases. In the present study, we aimed to (1) investigate the effect of mussel and fish intake on glutathione peroxidase enzyme activity and (2) examine whether single nucleotide polymorphisms in the GPX1, GPX4, and SELENOP genes modify the effect of mussel and fish intake for 26 weeks on whole blood selenium, plasma selenoprotein P concentrations, and erythrocyte GPX enzyme activity in a randomized intervention trial in Denmark.

Results

CC homozygotes of the SELENOP/rs3877899 polymorphism who consumed 1000 g fish and mussels per week for 26 consecutive weeks had higher levels of both selenoprotein P (difference between means ??4.68 ng/mL (95% CI ??8.49, ??0.871)) and whole blood selenium (difference between means ??5.76 (95% CI ??12.5, 1.01)) compared to fish and mussel consuming T-allele carriers although the effect in whole blood selenium concentration was not statistically significant.

Conclusions

Our study indicates that genetically determined variation in SELENOP leads to different responses in expression of selenoproteins following consumption of selenium-rich foods. This study also emphasizes the importance of taking individual aspects such as genotypes into consideration when assessing risk in public health recommendations.

     

Cell death caused by quinazolinone HMJ-38 challenge in oral carcinoma CAL 27 cells: dissections of endoplasmic reticulum stress,mitochondrial dysfunction and tumor xenografts

Background

This investigation clearly clarified the synthesized and antimitotic compound, 2-(3′-methoxyphenyl)-6-pyrrolidinyl-4-quinazolinone (HMJ-38), addressing its target and precise mechanism of action. We hypothesized that HMJ-38 might sensitize apoptotic death of human oral carcinoma CAL 27 cells in vitro and inhibit xenograft tumor growth in vivo.

Methods

Cell viability was assessed utilizing MTT assay. HMJ-38-treated cells represented DNA fragmentation using agarose gel electrophoresis as further evidenced using TUNEL staining. Flow cytometric analyses, immunoblotting and quantitative RT-PCR were applied for protein and gene expression. Antitumor xenograft study was employed.

Results

HMJ-38 concentration- and time-dependently reduced viability of CAL 27 cells. The effect of intrinsic molecules was signalized during HMJ-38 exposure with disruption of ΔΨm, MPT pore opening and the release of various events from mitochondria undergoing cell apoptosis. HMJ-38 also markedly facilitated G₂/M phase arrest. HMJ-38 stimulated the activation of CDK1 activity that modulated phosphorylation on Ser70 of Bcl-2-mediated mitotic arrest and apoptosis. HMJ-38 triggered intracellular Ca^2 + release and activated related pivotal hallmarks of ER stress. HMJ-38 in nude mice bearing CAL 27 tumor xenografts decreased tumor growth. Furthermore, HMJ-38 enhanced caspase-3 gene expression and protein level in xenotransplanted tumors.

Conclusions

Early roles of mitotic arrest, unfolded protein response and mitochondria-dependent signaling contributed to apoptotic CAL 27 cell demise induced by HMJ-38. In in vivo experiments, HMJ-38 also efficaciously suppressed tumor volume in a xenotransplantation model.

General significance

This finding might fully support a critical event for HMJ-38 via induction of apoptotic machinery and ER stress against human oral cancer cells.     

Genetic variants in selenoprotein P plasma 1 gene (SEPP1) are associated with fasting insulin and first phase insulin response in Hispanics

Context

Insulin resistance is not fully explained on a molecular level, though several genes and proteins have been tied to this defect. Knockdowns of the SEPP1 gene, which encodes the selenoprotein P (SeP) protein, have been shown to increase insulin sensitivity in mice. SeP is a liver-derived plasma protein and a major supplier of selenium, which is a proposed insulin mimetic and antidiabetic agent.

Objective

SEPP1 single nucleotide polymorphisms (SNPs) were selected for analysis with glucometabolic measures.

Participants and measures

The study included1424 Hispanics from families in the Insulin Resistance Atherosclerosis Family Study (IRASFS). Additionally, the multi-ethnic Insulin Resistance Atherosclerosis Study was used. A frequently sampled intravenous glucose tolerance test was used to obtain precise measures of acute insulin response (AIR) and the insulin sensitivity index (S_I).

Design

21 SEPP1 SNPs (tagging SNPs (n = 12) from HapMap, 4 coding variants and 6 SNPs in the promoter region) were genotyped and analyzed for association.

Results

Two highly correlated (r² = 1) SNPs showed association with AIR (rs28919926; Cys368Arg; p = 0.0028 and rs146125471; Ile293Met; p = 0.0026) while rs16872779 (intronic) was associated with fasting insulin levels (p = 0.0097). In the smaller IRAS Hispanic cohort, few of the associations seen in the IRASFS were replicated, but meta-analysis of IRASFS and all 3 IRAS cohorts (N = 2446) supported association of rs28919926 and rs146125471 with AIR (p = 0.013 and 0.0047, respectively) as well as rs7579 with S_I (p = 0.047).

Conclusions

Overall, these results in a human sample are consistent with the literature suggesting a role for SEPP1 in insulin resistance.     

Serum selenium and single-nucleotide polymorphisms in genes for selenoproteins: relationship to markers of oxidative stress in men from Auckland, New Zealand

There is controversy as to the recommended daily intake of selenium (Se), and whether current New Zealand diets are adequate in this nutrient. Various functional single-nucleotide polymorphisms (SNPs) polymorphisms may affect the efficacy of Se utilisation. These include the glutathione peroxidases GPx1 rs1050450, GPx4 rs713041, as well as selenoproteins SEPP1 rs3877899, SEL15 rs5845, SELS rs28665122 and SELS rs4965373. This cross-sectional study measured serum Se levels of 503 healthy Caucasian men in Auckland, New Zealand, between ages 20–81. The Se distribution was compared with activities of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase, and DNA damage as measured by the single cell gel electrophoresis assay, both without and with a peroxide-induced oxidative challenge. Serum Se was measured using inductively coupled plasma-dynamic reaction cell-mass spectrometry, while selenoprotein SNPs were estimated using TaqMan^® SNP genotyping assays. While antioxidant enzyme activities and DNA damage recorded after a peroxide challenge increased with increasing serum selenium, the inherent DNA damage levels in leukocytes showed no statistically significant relationship with serum selenium. However, these relationships and dietary Se requirements at the individual level were modified by several different SNPs in genes for selenoproteins. The GPx1 rs1050450 C allele was significantly associated with GPx activity. Significant correlations between serum Se level and GPX activity were seen with all genotypes except for homozygous minor allele carriers, while the GPx1 rs1050450 CT genotype showed the highest correlation. Several genotypes showed significant correlations between serum Se and TR activity with SEPP1 rs3877899 GG genotype showing the highest correlation. A significant decreasing trend in DNA damage with increasing serum Se was seen among GPx1 rs1050450 CC and GPx4 rs713041 TT genotype carriers up to a serum Se level of 116 and 149 ng/ml, respectively. In the absence of this genetic information, we would recommend a serum Se concentration in the region of 100–150 ng/ml as providing a useful compromise.     

Anti-miR-197 inhibits migration in HCC cells by targeting KAI 1/CD82

Aim

To investigate the metastatic effects and mechanisms of miR-197 in hepatocellular carcinoma (HCC).

Methods and results

The levels of miR-197 increased in HCC cells and tissues compared with a normal hepatic cell line (LO2) and adjacent nontumorous liver tissues, respectively. miR-197 expression negatively correlated with CD82 mRNA expression in these cell lines and tissues. Dual luciferase reporter assay and Western blot confirmed a direct interaction between miR-197 and CD82 3′UTR sequences. After miR-197 was silenced in HCC cells, CD82 expression increased. In the presence of human hepatocyte growth factor (HGF), cells silenced for anti-miR-197 exhibited elongated cellular tails and diminished lamellipodia due to reductions in both ROCK activity and the levels of Rac 1 protein. Downregulation of miR-197 along with the upregulation of CD82 in HCC cells resulted in the inhibition of HCC migration and invasion in vitro and in vivo.

Conclusion

Taken together, these data suggest that anti-miR-197 suppresses HCC migration and invasion by targeting CD82. The regulation of the miR-197/CD82 axis could be a novel therapeutic target in future HCC effective therapy.     

Impacts of TCF7L2 gene polymorphisms on the susceptibility of hepatogenous diabetes and hepatocellular carcinoma in cirrhotic patients

Background

Hepatogenous diabetes (HD) occurs as a complication of cirrhosis. Whether genetic factors, rather than only liver damage, play roles in the development of HD is unknown. TCF7L2 gene has been reported to be associated with type 2 diabetes and also cancer risks. We aim to evaluate the impact of TCF7L2 gene on the susceptibility of HD and hepatocellular carcinoma (HCC) in a Chinese Han population.

Patients and methods

A total of 367 adult liver transplant candidates with liver cirrhosis were included. Fifteen tag single nucleotide polymorphisms (SNPs) were selected from HapMap CHB database with a minor allele frequency of > 0.2 and r² of > 0.8. Another three SNPs were also chosen because of their close association with type 2 diabetes in East Asian.

Results

Patients with HD presented significantly poorer liver function, higher incidence of cirrhotic complications and higher insulin resistance compared with non-HD patients. Three SNPs were differentially distributed between HD patients and non-HD patients. In multivariate logistic analysis, TCF7L2 rs290487 and rs6585194 polymorphisms were independently associated with HD after adjustment of clinical factors. The TCF7L2 rs290487 C/C variant homozygote showed much higher insulin resistance and significantly increased HD risk comparing with T/T and T/C genotypes, while the genetic variant of rs6585194 was protectively against HD. Three SNPs (rs290481, rs290487 and rs290489) located near the 3′ end of TCF7L2 gene were associated with HCC risk with marginal significance. Patients carrying G-C-A haplotype had a significantly higher HCC risk than those with A-T-G.

Conclusions

TCF7L2 polymorphisms were associated with HD and maybe cancer risk as well. Further studies with large samples are needed to verify these results.     

Selenium supplementation shows protective effects against patulin-induced brain damage in mice via increases in GSH-related enzyme activity and expression

Aims

This study was designed to investigate the protective effects of selenium supplementation on patulin-induced neurotoxicity.

Main methods

Mice were subjected to patulin for 8 weeks. Sodium selenite (Na₂SeO₃) and selenium–methionine (Se–Met) were supplemented with the diet, and we investigated the effects of selenium on patulin-induced neurotoxicity. The animals were randomly divided into 4 groups containing 6–8 mice each. The first group was used as a control, and only physiological saline (0.9%) was injected. The second group was treated with patulin (1 mg/kg) intraperitoneally. The third group was treated with patulin (1 mg/kg) along with a dietary supplementation of Na₂SeO₃ (0.2 mg Se/kg of diet). The fourth group was treated with patulin (1 mg/kg) plus Se–Met (0.2 mg Se/kg of diet).

Key findings

Patulin treatment increased oxidative damage in the brain, as evidenced by a decrease in non-protein thiol and total thiol groups, along with significant increases in GSSG, reactive oxygen species, thiobarbituric acid reactive substances and protein carbonyl levels. Moreover, the activities of glutathione peroxidase (GPx) and glutathione reductase were inhibited with patulin treatment. Selenium supplementation significantly ameliorated these biological parameter changes. In addition, selenium treatments significantly increased the mRNA levels of GPx-1, GPx-4 and thioredoxin reductase.

Significance

Our data show that selenium supplementation increases the activity and expression of glutathione-related enzymes and offers significant protection against brain damage induced by patulin.     

5′-Nitro-indirubinoxime induces G1 cell cycle arrest and apoptosis in salivary gland adenocarcinoma cells through the inhibition of Notch-1 signaling

Background

5′-Nitro-indirubinoxime (5′-NIO) is a new derivative of indirubin that exhibits anti-cancer activity in a variety of human cancer cells. However, its mechanism has not been fully clarified.

Methods

Human salivary gland adenocarcinoma (SGT) cells were used in this study. Western blot and RT-PCR analyses were performed to determine cellular Notch levels. The cell cycle stage and level of apoptosis were analyzed using flow cytometry analysis.

Results

5′-NIO significantly inhibited the mRNA levels of Notch-1 and Notch-3 and their ligands (Delta1, 2, 3, and Jagged-2) in SGT cells. Immunocytochemistry analysis showed that 5′-NIO specifically decreased the level of Notch-1 in the nucleus. In addition, 5′-NIO induced G1 cell cycle arrest by reducing levels of CDK4 and CDK6 in SGT cells. Using flow cytometry and immunoblotting analysis, we found that 5′-NIO induces apoptosis following the secretion of cytochrome c and the activation of caspase-3 and caspase-7. Intracellular Notch-1 overexpression led to a decrease in G1 phase arrest and an inhibition of 5′-NIO-induced apoptosis.

Conclusion

These observations suggest that 5′-NIO induces cell cycle arrest and apoptosis by down-regulating Notch-1 signaling.

General significance

This study identifies a new mechanism of 5′-NIO-mediated anti-tumor properties. Thus, 5′-NIO could be used as a candidate for salivary gland adenocarcinoma therapeutics.     

The effects of selenium and the GPx-1 selenoprotein on the phosphorylation of H2AX

Background

Significant data supports the health benefits of selenium although supplementation trials have yielded mixed results. GPx-1, whose levels are responsive to selenium availability, is implicated in cancer etiology by human genetic data. Selenium's ability to alter the phosphorylation of the H2AX, a histone protein that functions in the reduction of DNA damage by recruiting repair proteins to the damage site, following exposure to ionizing radiation and bleomycin was investigated.

Methods

Human cell lines that were either exposed to selenium or were transfected with a GPx-1 expression construct were exposed to ionizing radiation or bleomycin. Phosphorylation of histone H2AX was quantified by flow cytometry and survival by the MTT assay. Phosphorylation of the Chk1 and Chk2 checkpoint proteins was quantified by western blotting.

Results

In colon-derived cells, selenium increases GPx-1 and attenuated H2AX phosphorylation following genotoxic exposures while the viability of these cells was unaffected. MCF-7 cells and transfectants that express high GPx-1 levels were exposed to ionizing radiation and bleomycin, and H2AX phosphorylation and cell viability were assessed. GPx-1 increased H2AX phosphorylation and viability following the induction of DNA damage while enhancing the levels of activated Chk1 and Chk2.

Conclusions

Exposure of mammalian cells to selenium can alter the DNA damage response and do so by mechanisms that are dependent and independent of its effect on GPx-1.

General significance

Selenium and GPx-1 may stimulate the repair of genotoxic DNA damage and this may account for some of the benefits attributed to selenium intake and elevated GPx-1 activity.     

Protein disulfide isomerase and glutathione are alternative substrates in the one Cys catalytic cycle of glutathione peroxidase 7

Background

Mammalian GPx7 is a monomeric glutathione peroxidase of the endoplasmic reticulum (ER), containing a Cys redox center (CysGPx). Although containing a peroxidatic Cys (C_P) it lacks the resolving Cys (C_R), that confers fast reactivity with thioredoxin (Trx) or related proteins to most other CysGPxs.

Methods

Reducing substrate specificity and mechanism were addressed by steady-state kinetic analysis of wild type or mutated mouse GPx7. The enzymes were heterologously expressed as a synuclein fusion to overcome limited expression. Phospholipid hydroperoxide was the oxidizing substrate. Enzyme–substrate and protein–protein interaction were analyzed by molecular docking and surface plasmon resonance analysis.

Results

Oxidation of the C_P is fast (k_+ 1 > 10³ M^− 1 s^− 1), however the rate of reduction by GSH is slow (k′_+ 2 = 12.6 M^− 1 s^− 1) even though molecular docking indicates a strong GSH–GPx7 interaction. Instead, the oxidized C_P can be reduced at a fast rate by human protein disulfide isomerase (HsPDI) (k_+ 1 > 10³ M^− 1 s^− 1), but not by Trx. By surface plasmon resonance analysis, a K_D = 5.2 μM was calculated for PDI–GPx7 complex. Participation of an alternative non-canonical C_R in the peroxidatic reaction was ruled out. Specific activity measurements in the presence of physiological reducing substrate concentration, suggest substrate competition in vivo.

Conclusions

GPx7 is an unusual CysGPx catalyzing the peroxidatic cycle by a one Cys mechanism in which GSH and PDI are alternative substrates.

General significance

In the ER, the emerging physiological role of GPx7 is oxidation of PDI, modulated by the amount of GSH.     

Powerful tumor cell growth-inhibiting activity of a synthetic derivative of atractyligenin: Involvement of PI3K/Akt pathway and thioredoxin system

Background

The semi-synthetic ent-kaurane 15-ketoatractyligenin methyl ester (SC2017) has been previously reported to possess high antiproliferative activity against several solid tumor-derived cell lines. Our study was aimed at investigating SC2017 tumor growth-inhibiting activity and the underlying mechanisms in Jurkat cells (T-cell leukemia) and xenograft tumor models.

Methods

Cell viability was evaluated by MTT assay. Cell cycle progression, reactive oxygen species (ROS) elevation and apoptotic hallmarks were monitored by flow cytometry. Inhibition of thioredoxin reductase (TrxR) by biochemical assays. Levels and/or activation status of signaling proteins were assessed by western blotting. Xenograft tumors were generated with HCT 116 colon carcinoma cells.

Results

SC2017 displayed cell growth-inhibiting activity against Jurkat cells (half maximal inhibitory concentration values (IC50) < 2 μM), but low cell-killing potential in human peripheral blood mononuclear cells (PBMC). The primary response of Jurkat cells to SC2017 was an arrest in G₂ phase followed by caspase-dependent apoptosis. Inhibition of PI3K/Akt pathway and TrxR activity by SC2017 was demonstrated by biochemical and pharmacological approaches. At least, SC2017 was found to inhibit xenograft tumor growth.

Conclusions

Our results demonstrate that SC2017 inhibits tumor cell growth in in vitro and in vivo models, but displays moderate toxicity against PBMC. We also demonstrate that SC2017 promotes caspase-dependent apoptosis in Jurkat cells by affecting Akt activation status and TrxR functionality.

General significance

Our observations suggest the semi-synthetic ent-kaurane SC2017 as a promising chemotherapeutic compound. SC2017 has, indeed, shown to possess tumor growth inhibiting activity and be able to counteract PI3K/Akt and Trx system survival signaling.     

Association Study of Polymorphisms in Selenoprotein Genes and Kashin–Beck Disease and Serum Selenium/Iodine Concentration in a Tibetan Population

Background

Kashin-Beck disease is a kind of degenerative osteoarthropathy. Genetic factors may play an important role in the pathogenesis of KBD.

Objective

To investigate the association of the selenoprotein genes GPX1 (rs1050450, rs1800668, and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) with Kashin-Beck disease (KBD) in a Tibetan population and to investigate the association of these SNPs with the serum iodine/selenium concentration in the Tibetan population.

Design

Five SNPs including rs1050450, rs1800668, and rs3811699 in the GPX1 gene, rs5748469 in the TrxR2 gene, and rs225014 in the DIO2 gene were analyzed in Tibetan KBD patients and controls using the SNaPshot method. P trend values of the SNPs were calculated using an additive model.

Results

None of the five SNPs in the three genes showed a significant association with KBD. Haplotypes TCC, TTC and TTT of rs1050450, rs1800668 and rs3811699 in GPX1 showed a significant association with KBD and controls with P value of 0.0421, 5.0E-4 and 0.0066, respectively. The GPX1 gene (rs1050450) showed a potential significant association with the iodine concentration in the Tibetan study population (P = 0.02726). However, no such association was detected with the selenium concentration (P = 0.2849).

Conclusion(s)

In this study, we showed that single SNPs in the genes GPX1 (rs1050450, rs1800668 and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) may not be significantly associated with KBD in a Tibetan population. However, haplotype analysis of SNPs rs1050450, rs1800668 and rs3811699 in GPX1 gene showed a significant association with KBD. The results suggested that GPX1 gene play a protective role in the susceptivity of KBD in Tibetans. Furthermore, the GPX1 gene (rs1050450) may be significantly associated with the serum iodine concentration in Tibetans.     

Selenoproteins and selenium status in bone physiology and pathology

Background

Emerging evidence supports the view that selenoproteins are essential for maintaining bone health.

Scope of review

The current state of knowledge concerning selenoproteins and Se status in bone physiology and pathology is summarized.

Major conclusions

Antioxidant selenoproteins including glutathione peroxidase (GPx) and thioredoxin reductase (TrxR), as a whole, play a pivotal role in maintaining bone homeostasis and protecting against bone loss. GPx1, a major antioxidant enzyme in osteoclasts, is up-regulated by estrogen, an endogenous inhibitor of osteoclastogenesis. TrxR1 is an immediate early gene in response to 1α,25-dihydroxyvitamin D3, an osteoblastic differentiation agent. The combination of 1α,25-dihydroxyvitamin D3 and Se generates a synergistic elevation of TrxR activity in Se-deficient osteoblasts. Of particular concern, pleiotropic TrxR1 is implicated in promoting NFκB activation. Coincidentally, TrxR inhibitors such as curcumin and gold compounds exhibit potent osteoclastogenesis inhibitory activity. Studies in patients with the mutations of selenocysteine insertion sequence-binding protein 2, a key trans-acting factor for the co-translational insertion of selenocysteine into selenoproteins have clearly established a causal link of selenoproteins in bone development. Se transport to bone relies on selenoprotein P. Plasma selenoprotein P concentrations have been found to be positively correlated with bone mineral density in elderly women.

General significance

A full understanding of the role and function of selenoproteins and Se status on bone physiology and pathology may lead to effectively prevent against or modify bone diseases by using Se.     

Cellular internalization and stress response of ingested amorphous silica nanoparticles in the midgut of Drosophila melanogaster

Background

Amorphous silica nanoparticles (aSNPs) are used for various applications including food industry. However, limited in vivo studies are available on absorption/internalization of ingested aSNPs in the midgut cells of an organism. The study aims to examine cellular uptake of aSNPs (< 30 nm) in the midgut of Drosophila melanogaster (Oregon R⁺) owing to similarities between the midgut tissue of this organism and human and subsequently cellular stress response generated by these nanoparticles.

Methods

Third instar larvae of D. melanogaster were exposed orally to 1–100 μg/mL of aSNPs for 12–36 h and oxidative stress (OS), heat shock genes (hsgs), membrane destabilization (Acridine orange/Ethidium Bromide staining), cellular internalization (TEM) and apoptosis endpoints.

Results

A significant increase was observed in OS endpoints in the midgut cells of exposed Drosophila in a concentration- and time-dependent manner. Significantly increased expression of hsp70 and hsp22 along with caspases activation, membrane destabilization and mitochondrial membrane potential loss was also observed. TEM analysis showed aSNPs-uptake in the midgut cells of exposed Drosophila via endocytic vesicles and by direct membrane penetration.

Conclusion

aSNPs after their internalization in the midgut cells of exposed Drosophila larvae show membrane destabilization along with increased cellular stress and cell death.

General significance

Ingested aSNPs show adverse effects on the cells of GI tract of the exposed organism thus their industrial use as a food-additive may raise concern to human health.     

Interaction of the retinoic acid signaling pathway with spicule formation in the marine sponge Suberites domuncula through activation of bone morphogenetic protein-1

Background

The formation of the spicules in siliceous sponges involves the formation of cylinder-like structures in the extraspicular space, composed of the enzyme silicatein and the calcium-dependent lectin.

Scope of review

Molecular cloning of the cDNAs (carotene dioxygenase, retinal dehydrogenase, and BMB-1 [bone morphogenic protein-1]) from the demosponge Suberites domuncula was performed. These tools were used to understand the retinoid metabolism in the animal by qRT-PCR, immunoblotting and TEM.

Major conclusions

We demonstrate that silintaphin-2, a silicatein-interacting protein, is processed from a longer-sized 15-kDa precursor to a truncated, shorter-sized 13 kDa calcium-binding protein via proteolytic cleavage at the dipeptide Ala↓Asp, mediated by BMP-1. The expression of this protease as well as the expression of two key enzymes of the carotinoid metabolism, the β,β-carotene-15,15′-dioxygenase and the retinal dehydrogenase/reductase, were found to be strongly up-regulated by retinoic acid. Hence retinoic acid turned out to be a key factor in skeletogenesis in the most ancient still existing metazoans, the sponges.

General significance

It is shown that retinoic acid regulates the formation of the organic cylinder that surrounds the axis of the spicules and enables, as a scaffold, the radial apposition of new silica layers and hence the growth of the spicules.