The biggest drawback of a current diabetes therapy is the treatment of the consequences not the cause of the disease. Regardless of the diabetes type, preservation and recovery of functional pancreatic beta cells stands as the biggest challenge in the treatment of diabetes. Free radicals and oxidative stress are among the major mediators of autoimmune destruction of beta cells in type 1 diabetes (T1D) or beta cell malfunction and death provoked by glucotoxicity and insulin resistance in type 2 diabetes (T2D). Additionally, oxidative stress reduces functionality of beta cells in T2D by stimulating their de-/trans-differentiation through the loss of transcription factors critical for beta cell development, maturity and regeneration. This review summarizes up to date clarified redox-related mechanisms involved in regulating beta cell identity and death, underlining similarities and differences between T1D and T2D. The protective effects of natural antioxidants on the oxidative stress-induced beta cell failure were also discussed. Considering that oxidative stress affects epigenetic regulatory mechanisms involved in the regulation of pancreatic beta cell survival and insulin secretion, this review highlighted huge potential of epigenetic therapy. Special attention was paid on application of the state-of-the-art CRISPR/Cas9 technology, based on targeted epigenome editing with the purpose of changing the differentiation state of different cell types, making them insulin-producing with ability to attenuate diabetes. Clarification of the above-mentioned mechanisms could provide better insight into diabetes etiology and pathogenesis, which would allow development of novel, potentially more efficient therapeutic strategies for the prevention or reversion of beta cell loss.
Background Poly(ADP-ribosyl)ation (PARylation), a posttranslational modification introduced by PARP-1 and PARP-2, has first been implicated in DNA demethylation due to its role in base excision repair. Recent evidence indicates a direct influence of PARP-dependent PARylation on TET enzymes which catalyse hydroxymethylation of DNA—the first step in DNA demethylation. However, the exact nature of influence that PARylation exerts on TET activity is still ambiguous. In our recent study, we have observed a negative influence of PARP-1 on local TET-mediated DNA demethylation of a single gene and in this study, we further explore PARP–TET interplay. Results Expanding on our previous work, we show that both TET1 and TET2 can be in vitro PARylated by PARP-1 and PARP-2 enzymes and that TET1 PARylation negatively affects the TET1 catalytic activity in vitro. Furthermore, we show that PARylation inhibits TET-mediated DNA demethylation at the global genome level in cellulo. Conclusions According to our findings, PARP inhibition can positively influence TET activity and therefore affect global levels of DNA methylation and hydroxymethylation. This gives a strong rationale for future examination of PARP inhibitors' potential use in the therapy of cancers characterised by loss of 5-hydroxymethylcytosine.
An efficient transfection is a crucial step for the introduction of epigenetic modification in host cells, and there is a need for an optimized transfection process for individual model systems separately. Mouse pancreatic αTC1-6 cells, which act as an attractive model system for epigenetic cell reprogramming and diabetes treatment, were transiently transfected with two different transfection methods: the chemical method with polyethyleneimine (PEI) and nucleofection as a physical transfection method. Flow cytometry and fluorescent microscopy examination of GFP expression showed that transfection efficiency was affected by the size of plasmids using both transfection methods. Subsequently, the Cas9 mRNA expression confirmed successful transfection with EpiCRISPR plasmid, whereas the cell physiology remained unchanged. The adjusted nucleofection protocol for αTC1-6 cells transfected with an EpiCRISPR mix of plasmids reached 71.1% of GFP-positive transfected cells on the fifth post-transfection day and proved to be much more efficient than the 3.8% GFP-positive PEI transfected cells. Modifying the protocol, we finally specify CM-156 program and SF 4D-Nucleofector X Solutions for Amaxa™ nucleofection as a method of choice for alpha TC1-6 cell line transfection.
Epithelial to mesenchymal transition (EMT) contributes to fibrosis associated pathologies including scarring of different ocular tissues. Recently targeting EMT is seen as an appropriate therapeutic approach for different fibrosis related eye diseases such as macular degeneration or glaucoma surgery related fibrosis. Nevertheless, for ocular surface diseases, target genes specific for particular cell type or condition are still undefined. This study aimed to expose the complex regulatory mechanisms that trigger EMT in human conjunctival epithelial (HCjE) cells. EMT was induced by prolonged treatment with two TGF-β isoforms, TGF-β1 and TGF-β2, and their combination. TGF-β1 showed the strongest potential for initiating EMT in HCjE cells, reflected on morphological changes, cell migration and the levels of mRNA expression of different epithelial (CDH1, OCLN, DSP) and mesenchymal (CDH2, FN1, VIM, SNAI1, ZEB2, TWIST1) marker genes. Co-treatment with the DNA demethylating agent 5-Azacytidine (5-AzaC) was capable of stopping the transition of HCjE cells towards a mesenchymal phenotype, based on morphological features, reduced cell mobility and mRNA and protein expression levels of epithelial and mesenchymal marker genes. An EMT qRT-PCRbased array revealed that EMT induced considerable alterations in gene expression, with downregulation of the majority of epithelial marker genes and upregulation of genes specific for the mesenchymal state. The major effect of 5-AzaC treatment was observed as a suppression of mesenchymal marker genes, suggesting the involvement of upstream negative regulator(s) whose promoter demethylation and subsequent expression will in turn promote EMT switch off. The expression level of miRNAs potentially important for EMT induction was determined using qRT-PCRbased array which pointed at members of miR-200 family as main regulators of EMT process in HCjE cells. 5-AzaC treatment induced increased expression of miR-200a, -200b, -200c and miR-141 towards the control level, indicating important role of DNA methylation in their regulation. The DNA methylation status of both miR-200 family clusters, analyzed with high-resolution melting (HRM) and bisulfite sequencing (Bis-Seq), revealed that TGF-β1-induced EMT was accompanied by increase in promoter CpG methylation of both miR-200 loci, which was reverted after 5-AzaC treatment. In conclusion, our results indicate that DNA demethylation of promoters of miR-200 loci is critically important for stopping and reverting the EMT in human conjunctival epithelial cells, suggesting the potential for the development of novel epigenetic-based therapeutic strategies for treating conjunctival conditions associated with EMT.
The aim of this research was to determine the relations of fitness parameters and morphological characteristics of seven-year-old obese children. The sample of participants consisted of 103 obese children (63 girls and 40 boys), first grade students (mean age 7,04 years) of the elementary schools in Nis. The following fitness parameters were measured: HR in load, VO2max, resting HR, bend forward -bend backward -throw test, hand taping, 20m dash with a standing start, Abalakov test and forward bend on the bench test. Morphological characteristics were determined by measuring 13 parameters of longitudinal and transversal dimensions of the skeleton, volume and body weight, as well as subcutaneous fat tissue. For all of the data we calculated the Mean and standard deviation (SD). A canonical correlation analysis was used to determine the relations between the set of variables representing fitness parameters and the set of variables of morphological characteristics. Based on the coefficients of the canonical correlation analysis, it can be concluded that the spaces of morphological characteristics and fitness parameters are interconnected with two pairs of statistically significant canonical factors (p˂.05 and p˂.01). The general analysis of the relationships between the first pair of canonical factors suggests that participants with higher circular dimensionalities of the body, accentuated adiposity and body mass tend to have poorer results in motoring tasks requiring body flexibility, explosive leg strength and running speed, and also have poorer results in the parameters of cardiorespiratory fitness. It can be concluded that obesity in younger school age has negative implications on the fitness parameters in children, and therefore on their overall growth and development.
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