Biodentine and mineral trioxide aggregate induce similar cellular responses in a fibroblast cell line.

INTRODUCTION: The aim of this study was to assess the cell viability and messenger RNA expression of interleukin (IL)-1α and IL-6 in 3T3 fibroblast cells when in direct contact with Biodentine (Septodont, Saint Maur de Fossés, France) and mineral trioxide aggregate (MTA). METHODS: Biodentine and MTA were coated onto coverslips and allowed to set. An uncoated coverslip and one coated with GC Fuji IX (GC Corporation, Tokyo, Japan) were used as controls. Coverslips were cultured with 3T3 fibroblast cells. Cell viability was assessed quantitatively using AlamarBlue dye (Serotec, Oxford, UK) after 3, 6, 24, and 72 hours. Morphologic cell changes of 3T3 cells in contact with BD and MTA were observed by scanning electron microscopy, and cytokine expression was assessed at the messenger RNA level by semiquantitative reverse-transcription polymerase chain reaction after 3 and 24 hours of direct contact with the materials. RESULTS: Cells in contact with Biodentine and MTA showed similar viability to untreated control cells at all time points, with the exception of 6 hours when viability was decreased with both treatments. Examination by scanning electron microscopy revealed cells adhering to most of the Biodentine surface after 24 hours. However, for MTA samples, significantly fewer cells were observed. The messenger RNA expression of IL-1α and IL-6 by cells in contact with Biodentine was similar to cells in contact with MTA. CONCLUSIONS: Biodentine and MTA showed similar cytotoxicity and induced a similar pattern of cytokine expression.

Altered expression of ZnT10 in Alzheimer's disease brain.

There is an increasing body of evidence suggesting that metal homeostasis is dysregulated in the pathology of Alzheimer's disease (AD). Although expression levels of several transporters belonging the SLC30 family, which comprises predominantly zinc transporters, have been studied in the AD brain, SLC30A10 (ZnT10) has not been studied in this context. To determine if dysregulated expression of ZnT10, which may transport both Zn and Mn, could be a factor that contributes to AD, we investigated if there were differences in ZnT10 mRNA levels in specimens of frontal cortex from AD patients and controls and also if brain tissue from the APP/PS1 transgenic (Tg) mouse model showed abnormal levels of ZnT10 mRNA expression. Our results show that ZnT10 is significantly (P<0.01) decreased in the frontal cortex in AD. Furthermore, we observed a significant decrease in ZnT10 mRNA levels in the APP/PS1-Tg mice compared with wild-type controls (P<0.01). Our results suggest that this dysregulation in ZnT10 could further contribute to disease progression.

Effects of Sirt1 on DNA methylation and expression of genes affected by dietary restriction.

Changes in DNA methylation across the life course may contribute to the ageing process. We hypothesised that some effects of dietary restriction to extend lifespan and/or mitigate against features of ageing result from changes in DNA methylation, so we determined if genes that respond to dietary restriction also show age-related changes in DNA methylation. In support of our hypothesis, the intersection of lists of genes compiled from published sources that (1) were differentially expressed in response to dietary restriction and (2) showed altered methylation with increased age was greater than expected. We also hypothesised that some effects of Sirt1, which may play a pivotal role in beneficial effects of dietary restriction, are mediated through DNA methylation. We thus measured effects of Sirt1 overexpression and knockdown in a human cell line on DNA methylation and expression of a panel of eight genes that respond to dietary restriction and show altered methylation with age. Six genes were affected at the level of DNA methylation, and for six expressions were affected. In further support of our hypothesis, we observed by DNA microarray analysis that genes showing differential expression in response to Sirt1 knockdown were over-represented in the complied list of genes that respond to dietary restriction. The findings reveal that Sirt1 has effects on DNA methylation across the genome and affects, in particular, the expression of genes that respond to dietary restriction. Sirt1-mediated effects on DNA methylation and, consequently, gene expression may thus be one of the mechanisms underlying the response to dietary restriction.

Identification of the human zinc transcriptional regulatory element (ZTRE): a palindromic protein-binding DNA sequence responsible for zinc-induced transcriptional repression.

Many genes with crucial roles in zinc homeostasis in mammals respond to fluctuating zinc supply through unknown mechanisms, and uncovering these mechanisms is essential to understanding the process at cellular and systemic levels. We detected zinc-dependent binding of a zinc-induced protein to a specific sequence, the zinc transcriptional regulatory element (ZTRE), in the SLC30A5 (zinc transporter ZnT5) promoter and showed that substitution of the ZTRE abrogated the repression of a reporter gene in response to zinc. We identified the ZTRE in other genes, including (through an unbiased search) the CBWD genes and (through targeted analysis) in multiple members of the SLC30 family, including SLC30A10, which is repressed by zinc. The function of the CBWD genes is currently unknown, but roles for homologs in metal homeostasis are being uncovered in bacteria. We demonstrated that CBWD genes are repressed by zinc and that substitution of the ZTRE in SLC30A10 and CBWD promoter-reporter constructs abrogates this response. Other metals did not affect expression of the transcriptional regulator, binding to the ZTRE or promoter-driven reporter gene expression. These findings provide the basis for elucidating how regulation of a network of genes through this novel mechanism contributes to zinc homeostasis and how the cell orchestrates this response.

Efflux function, tissue-specific expression and intracellular trafficking of the Zn transporter ZnT10 indicate roles in adult Zn homeostasis.

Zn is essential to the structure and function of numerous proteins and enzymes so requires tight homeostatic control at both the systemic and cellular level. Two families of Zn transporters - ZIP (SLC39) and ZnT (SLC30) - contribute to Zn homeostasis. There are at least 10 members of the human ZnT family, and the expression profile and regulation of each varies depending on tissue type. Little is known about the role and expression pattern of ZnT10; however in silico data predict restricted expression to foetal tissue. We show a differential expression profile for ZnT10 in adult human tissue by RT-qPCR and detect highest levels of expression in small intestine, liver and brain tissues. We present data revealing the functional activity of ZnT10 to be in the efflux direction. Using a plasmid construct to express ZnT10 with an N-terminal FLAG-epitope tag, we reveal subcellular localisation in a neuroblastoma cell line (SH-SY5Y) to be at the Golgi apparatus under standard conditions of culture, with trafficking to the plasma membrane observed at higher extracellular Zn concentrations. We demonstrate down-regulation by Zn of ZnT10 mRNA levels in cultured intestinal and neuroblastoma cell lines and demonstrate reduced transcription from the ZnT10 promoter at an elevated extracellular Zn concentration. These features of ZnT10 localisation, regulation and function, together with the discovery that ZnT10 is expressed a high levels in brain tissue, indicate that ZnT10 has a role in regulating Zn homeostasis in the brain so may have relevance to the development of neurodegenerative disease.