Exposure to Maghemite Nanoparticles Induces Epigenetic Alterations in Human Submandibular Gland Cells.

Even though nanotechnology has revolutionized the biomedical research, a plethora of studies debate the nanoparticles safety. In order to contribute to these studies, we evaluated the cytotoxic and epigenetic effects of maghemite nanoparticles covered with citric acid on human submandibular gland cells. Objective: This work objective was to evaluate the cytotoxic effects and epigenetic alterations induced in human salivary gland cells after treatment with maghemite nanoparticles covered with citric acid. Methods: For that, human submandibular gland cells were cultured and treated with nanoparticles for 24 or 48 hours. To assess cytotoxicity we used lactate dehydrogenase, a general oxidative stress indicator assay and microscopy. Epigenetic status was detected by colorimetric assays and the results were confirmed by quantitative polymerase chain reaction. Results: No cytotoxic effects were detected on cells exposed to up 3.0 mgFemL-1 for 48 hours, although cytoplasmic vacuoles formation was detected by light microscopy analyses. An increased generation of reactive oxygen species in cells exposed to nanoparticles was evidenced and iron clusters accumulated in the cytoplasm of treated cells. Global DNA methylation and histones H3 and H4 acetylation were also altered in response to nanoparticles exposure, thus suggesting a reprogramming of the epigenome. Transcripts accumulation analyses showed that genes related to iron metabolism and oxidative stress were upregulated, while the gene related to epigenetic reprogramming presented reduced transcript accumulation after treatment. Conclusion: We concluded that maghemite nanoparticles covered with citric acid exposure provoked several biological responses without impairment of human submandibular gland cells viability. This is the first report on the epigenetic effects of maghemite nanoparticles on this cell lineage.

Photodynamic therapy inhibits cell growth and enhances the histone deacetylase-mediated viability impairment in Cryptococcus spp. in vitro.

Cryptococcosis is a disseminated infection caused mainly by C. neoformans and C. gattii. Limitations for the treatment involve the selection of isolates resistant to conventional antifungal drugs, prolonged treatment time and drugs side effects. This study evaluated the combined effect of histone deacetylase inhibitors (HDACi) and photodynamic therapy (PDT) on the growth of C. neoformans and C. gattii in vitro. Results showed that PDT inhibited yeasts proliferation and enhanced the HDACi-mediated cell viability impairment in Cryptococcus spp.

The DNA-methyltransferase inhibitor 5-aza-2-deoxycytidine affects Humicola grisea enzyme activities and the glucose-mediated gene repression.

Humicola grisea var. thermoidea (Hgvt) is a thermophilic ascomycete that produces lignocellulolytic enzymes and it is proposed for the conversion of agricultural residues into useful byproducts. Drugs that inhibit the DNA methyltransferases (DNMTs) activity are employed in epigenetic studies but nothing is known about a possible effect on the production of fungal enzymes. We evaluated the effect of 5-aza-2'-deoxycytidine (5-Aza; a chemical inhibitor of DNMTs activity) on the secreted enzyme activity and on the transcription of cellulase and xylanase genes from Hgvt grown in agricultural residues and in glucose. Upon cultivation on wheat bran (WB), the drug provoked an increase in the xylanase activity at 96 h. When Hgvt was grown in glucose (GLU), a repressor of Hgvt glycosyl hydrolase genes, 5-Aza led to increased transcript accumulation for the cellobiohydrolases and for the xyn2 xylanase genes. In WB, 5-Aza enhanced the expression of the transcription factor CreA gene. Growth on WB or GLU, in presence of 5-Aza, led to a significant increase in transcripts of the pH-response regulator PacC gene. To our knowledge, this is the first report on the effect of a DNMT inhibitor in the production of fungal plant cell wall degradation enzymes.

The Relation Between Promoter Chromatin Status, Xyr1 and Cellulase Ex-pression in Trichoderma reesei.

The ascomycete Trichoderma reesei is used for the production of plant cell wall-degrading enzymes in industrial scale. The interplay of the transactivator Xyr1 and the repressor Cre1 mainly regulates the expression of these enzymes. During induc-ing conditions, such as in the presence of sophorose, the transcription of the two major cellulase-encoding genes, cbh1 and cbh2, is activated as well as the expression of xyr1. In the presence of D-glucose carbon catabolite repression mediated by Cre1 takes place and the expression of Xyr1 and the plant cell wall-degrading enzymes is down-regulated. In this study we compare the chromatin status of xyr1, cbh1, and cbh2 promoters in the wild-type strain and the Cre1-deficient strain Rut-C30. Chromatin rearrangement occurs in the xyr1 promoter during induction on sophorose. Chromatin opening and protein-DNA interactions in the xyr1 promoter were detected especially in a region located 0.9 kb upstream the translation start co-don, which bears several putative Cre1-binding sites and a CCAAT-box. Moreover, the xyr1 promoter is overall more acces-sible in a cre1-truncated background, no matter which carbon source is present. This makes the xyr1 regulatory sequence a good target for promoter engineering aiming at the enhancement of cellulase production.

Thermophilic molds: Biology and applications.

Thermophilic molds thrive in a variety of natural habitats including soils, composts, wood chip piles, nesting materials of birds and other animals, municipal refuse and others, and ubiquitous in their distribution. These molds grow in simple media containing carbon and nitrogen sources and mineral salts. Polyamines are synthesized in these molds and the composition of lipids varies considerably, predominantly containing palmitic, oleic and linoleic acids with low levels of lauric, palmiotoleic and stearic acids. Thermophilic molds are capable of efficiently degrading organic materials by secreting thermostable enzymes, which are useful in the bioremediation of industrial wastes and effluents that are rich in oil, heavy metals, anti-nutritional factors such as phytic acid and polysaccharides. Thermophilic molds synthesize several antimicrobial substances and biotechnologically useful miscellaneous enzymes. The analysis of genomes of thermophilic molds reveals high G:C contents, shorter introns and intergenic regions with lesser repetitive sequences, and further confirms their ability to degrade agro-residues efficiently. Genetic engineering has aided in ameliorating the characteristics of the enzymes of thermophilic molds. This review is aimed at focusing on the biology of thermophilic molds with emphasis on recent developments in the analysis of genomes, genetic engineering and potential applications.

The impact of chromatin remodelling on cellulase expression in Trichoderma reesei.

BACKGROUND: Trichoderma reesei is used for industry-scale production of plant cell wall-degrading enzymes, in particular cellulases, but also xylanases. The expression of the encoding genes was so far primarily investigated on the level of transcriptional regulation by regulatory proteins. Otherwise, the impact of chromatin remodelling on gene expression received hardly any attention. In this study we aimed to learn if the chromatin status changes in context to the applied conditions (repressing/inducing), and if the presence or absence of the essential transactivator, the Xylanase regulator 1 (Xyr1), influences the chromatin packaging. RESULTS: Comparing the results of chromatin accessibility real-time PCR analyses and gene expression studies of the two prominent cellulase-encoding genes, cbh1 and cbh2, we found that the chromatin opens during sophorose-mediated induction compared to D-glucose-conferred repression. In the strain bearing a xyr1 deletion the sophorose mediated induction of gene expression is lost and the chromatin opening is strongly reduced. In all conditions the chromatin got denser when Xyr1 is absent. In the case of the xylanase-encoding genes, xyn1 and xyn2, the result was similar concerning the condition-specific response of the chromatin compaction. However, the difference in chromatin status provoked by the absence of Xyr1 is less pronounced. A more detailed investigation of the DNA accessibility in the cbh1 promoter showed that the deletion of xyr1 changed the in vivo footprinting pattern. In particular, we detected increased hypersensitivity on Xyr1-sites and stronger protection of Cre1-sites. Looking for the players directly causing the observed chromatin remodelling, a whole transcriptome shotgun sequencing revealed that 15 genes encoding putative chromatin remodelers are differentially expressed in response to the applied condition and two amongst them are differentially expressed in the absence of Xyr1. CONCLUSIONS: The regulation of xylanase and cellulase expression in T. reesei is not only restricted to the action of transcription factors but is clearly related to changes in the chromatin packaging. Both the applied condition and the presence of Xyr1 influence chromatin status.

Histone deacetylases inhibitors effects on Cryptococcus neoformans major virulence phenotypes.

Cryptococcus neoformans undergoes phenotypical changes during host infection in order to promote persistence and survival. Studies have demonstrated that such adaptations require alterations in gene transcription networks by distinct mechanisms. Drugs such as the histone deacetylases inhibitors (HDACi) Sodium Butyrate (NaBut) and Trichostatin A (TSA) can alter the chromatin conformation and have been used to modulate epigenetic states in the treatment of diseases such as cancer. In this work, we have studied the effect of NaBut and TSA on the expression of C. neoformans major virulence phenotypes and on the survival rate of an animal model infected with drugs-treated yeasts. Both drugs affected fungal growth at 37°C more intensely than at 30°C; nonetheless, drugs did not affect cell viability at the concentrations we studied. HDACi also provoked the reduction of the fungal capsule expansion. Phospholipases enzyme activity decreased; mating process and melanin synthesis were also affected by both inhibitors. NaBut led to an increase in the population of cells in G2/M. Treated yeast cells, which were washed in order to remove the drugs from the culture medium prior to the inoculation in the Galleria mellonela infection model, did not cause significant difference at the host survival curve when compared to non-treated cells. Overall, NaBut effects on the impairment of C. neoformans main virulence factors were more intense and stable than the TSA effects.

A truncated form of the Carbon catabolite repressor 1 increases cellulase production in Trichoderma reesei.

BACKGROUND: Rut-C30 is a cellulase-hyperproducing Trichoderma reesei strain and, consequently, became the ancestor of most industry strains used in the production of plant cell wall-degrading enzymes, in particular cellulases. Due to three rounds of undirected mutagenesis its genetic background differs from the wild-type QM6a in many ways, of which two are the lack of a 83 kb large sequence in scaffold 15 and the partial lack of the gene encoding the Carbon catabolite repressor 1 (CREI). However, it is still unclear, what exactly enhances cellulase production in Rut-C30. RESULTS: The investigation of the expression of two genes encoding cellulases (cbh1 and cbh2) and the gene encoding their main transactivator (xyr1) revealed that the presence of the truncated form of CREI (CREI-96) contributes more to the Rut-C30 phenotype than a general loss of CREI-mediated carbon catabolite repression (cre1 deletion strain) or the deletion of 29 genes encoded in the scaffold 15 (83 kb deletion strain). We found that the remaining cre1 in Rut-C30 (cre1-96) is transcribed into mRNA, that its putative gene product (Cre1-96) is still able to bind DNA, and that the CREI-binding sites in the upstream regulatory regions of the chosen CREI-target genes are still protected in Rut-C30. As it was previously reported that CREI acts on the nucleosome positioning, we also analyzed chromatin accessibility of the core promoters of CREI-target genes and found them open even on D-glucose in the presence of CREI-96. CONCLUSIONS: The lack of the full version of CREI in Rut-C30 corresponds with a partial release from carbon catabolite repression but is not completely explained by the lack of CREI. In contrast, the truncated CREI-96 of Rut-C30 exerts a positive regulatory influence on the expression of target genes. Mechanistically this might be explained at least partially by a CREI-96-mediated opening of chromatin.

From an electrophoretic mobility shift assay to isolated transcription factors: a fast genomic-proteomic approach.

BACKGROUND: Hypocrea jecorina (anamorph Trichoderma reesei) is a filamentous ascomycete of industrial importance due to its hydrolases (e.g., xylanases and cellulases). The regulation of gene expression can influence the composition of the hydrolase cocktail, and thus, transcription factors are a major target of current research. Here, we design an approach for identifying a repressor of a xylanase-encoding gene. RESULTS: We used streptavidin affinity chromatography to isolate the Xylanase promoter-binding protein 1 (Xpp1). The optimal conditions and templates for the chromatography step were chosen according to the results of an electrophoretic mobility shift assay performed under repressing conditions, which yielded a DNA-protein complex specific to the AGAA-box (the previously identified, tetranucleotide cis-acting element). After isolating AGAA-box binding proteins, the eluted proteins were identified with Nano-HPLC/tandem MS-coupled detection. We compared the identified peptides to sequences in the H. jecorina genome and predicted in silico the function and DNA-binding ability of the identified proteins. With the results from these analyses, we eliminated all but three candidate proteins. We verified the transcription of these candidates and tested their ability to specifically bind the AGAA-box. In the end, only one candidate protein remained. We generated this protein with in vitro translation and used an EMSA to demonstrate the existence of an AGAA-box-specific protein-DNA complex. We found that the expression of this gene is elevated under repressing conditions relative to de-repressing or inducing conditions. CONCLUSIONS: We identified a putative transcription factor that is potentially involved in repressing xylanase 2 expression. We also identified two additional potential regulatory proteins that bind to the xyn2 promoter. Thus, we succeeded in identifying novel, putative transcription factors for the regulation of xylanase expression in H. jecorina.

Interaction of bracken-fern extract with vitamin C in human submandibular gland and oral epithelium cell lines.

The consumption of bracken-fern (Pteridium aquilinum) as food is associated with a high incidence of cancer in humans and animals. Thus far, the carcinogenic effects of bracken-fern consumption could be related to chromosome aberrations verified in animal and in human peripheral lymphocytes. We tested the in vitro effects of vitamin C (10 and 100 microg/ml) on the reversibility of DNA damage caused by bracken-fern on human submandibular gland (HSG) cells and on oral epithelium cells (OSCC-3) previously exposed to bracken-fern extract. DNA damage (i.e. nuclei with increased levels of DNA migration) was determined by comet assay, cell morphology was evaluated by light microscopy and cellular degeneration was assessed by the acridine orange/ethidium bromide fluorescent-dyeing test. Results showed that vitamin C alone did not reduce DNA damage caused by bracken-fern in HSG and OSSC-3 cells. However, at a higher concentration (100 microg/ml), vitamin C induced DNA damage in both cell lines. Moreover, vitamin C (10 and 100 microg/ml) together with bracken-fern extract showed synergistic effects on the frequency of DNA damage in HSG cells. In addition, cells treated with bracken-fern extract or vitamin C alone, or with their association, showed apoptosis morphological features, such as chromatin condensation, cytoplasmic volume loss, changes in membrane symmetry and the appearance of vacuoles; these alterations were observed in both cell lines. These results demonstrate that bracken-fern extract was cytotoxic to HSG and OSCC-3 cells, causing cell death by apoptosis, and that vitamin was not able to revert these effects.

Functional genome of the human pathogenic fungus Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis is a dimorphic and thermo-regulated fungus which is the causative agent of paracoccidioidomycosis, an endemic disease widespread in Latin America. Pathogenicity is assumed to be a consequence of the cellular differentiation process that this fungus undergoes from mycelium to yeast cells during human infection. In an effort to elucidate the molecular mechanisms involved in this process a network of Brazilian laboratories carried out a transcriptome project for both cell types. This review focuses on the data analysis yielding a comprehensive view of the fungal metabolism and the molecular adaptations during dimorphism in P. brasiliensis from analysis of 6022 groups, related to expressed genes, which were generated from both mycelium and yeast phases.

Transcriptional profiles of the human pathogenic fungus Paracoccidioides brasiliensis in mycelium and yeast cells.

Paracoccidioides brasiliensis is the causative agent of paracoccidioidomycosis, a disease that affects 10 million individuals in Latin America. This report depicts the results of the analysis of 6,022 assembled groups from mycelium and yeast phase expressed sequence tags, covering about 80% of the estimated genome of this dimorphic, thermo-regulated fungus. The data provide a comprehensive view of the fungal metabolism, including overexpressed transcripts, stage-specific genes, and also those that are up- or down-regulated as assessed by in silico electronic subtraction and cDNA microarrays. Also, a significant differential expression pattern in mycelium and yeast cells was detected, which was confirmed by Northern blot analysis, providing insights into differential metabolic adaptations. The overall transcriptome analysis provided information about sequences related to the cell cycle, stress response, drug resistance, and signal transduction pathways of the pathogen. Novel P. brasiliensis genes have been identified, probably corresponding to proteins that should be addressed as virulence factor candidates and potential new drug targets.