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Presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes encode the major component of y-secretase, which is responsible for sequential proteolytic cleavages of amyloid precursor proteins and the subsequent formation of amyloid-β peptides. 150 RNA samples from the entorhinal cortex, auditory cortex and hippocampal regions of individuals with Alzheimer's disease (AD) and controls elderly subjects were analyzed with using real-time rtPCR. There were no differences between groups for PSEN1 expression. PSEN2 was significantly downregulated in the auditory cortex of AD patients when compared to controls and when compared to other brain regions of the patients. Alteration in PSEN2 expression may be a risk factor for AD.

Alzheimer's disease (AD) is a progressive neurodegenerative disease that takes the form of a local overexpression of cytokines and other inflammatory molecules. We investigated three single-nucleotide polymorphisms (SNP) of the interleukin 6 gene (IL-6) promoter region [-174G/C (rs 1800795), -572C/G (rs 1800796), and -597G/A (rs 1800797)] in 200 patients with late-onset AD and 165 elderly controls in a Brazilian case-control population sample. Genotyping was carried out from blood cells using PCR-RFLP techniques. Statistical analysis was performed to evaluate the Hardy-Weinberg equilibrium and to compare frequencies between groups. No association was found between any IL-6 polymorphism and AD; however the haplotype composed of the -597 A allele and the -174G allele indicated a crude odds ratio (OR) of 0.15 (p = 0.0021) and a significantly adjusted OR (adjusted for the APOE E4 allele value) of 0.15 (p = 0.00294). Linkage disequilibrium was D' = 0.68 among the three SNPs. Our findings revealed a protective effect of AG (-597A, -174G) haplotype, which worked independently of the APOE E4 allele in our Brazilian population sample. Thus, the promoter region of IL-6 gene probably exerts an effect through gene linkage and/or gene interaction.

Helicobacter pylori (H. pylori) induces an intense inflammatory response, mediated by proinflammatory cytokines, including interleukin (IL)-6 and its membrane receptor (IL-6R), which activates important signaling pathways in the development of gastric disease and cancer. We investigated the gene and protein expression of IL-6 and IL-6R and the influence of polymorphisms rs1800795, rs1800796, and rs1800797 on its gene expression together with H. pylori infection. Furthermore, an in-silico analysis was performed to support our results. Gastric biopsies were obtained from patients with gastric symptoms and patients with gastric cancer (GC) and were divided into groups (Control, Gastritis, and Cancer). H. pylori was detected by PCR. Realtime-qPCR was employed to determine gene expression, and western blot assay was used to analyze protein expression levels. PCR-RFLP was used to characterize IL-6 polymorphisms. Bioinformatics analyses were performed using the Gene Expression Omnibus (GEO) database and GEO2R to screen out differentially expressed genes (DEGs). H. pylori was detected in 43.3% of the samples. Statistically significant differences were found for IL-6 (P=0.0001) and IL-6R (P=0.0005) genes among the three groups, regardless of the presence of H. pylori. Among patients with H. pylori infection, the IL-6 and IL-6R gene and protein expressions were significantly increased, highlighting IL-6 gene overexpression in patients with GC. No statistically significant differences were found for the rs1800795, rs1800796, and rs1800797 polymorphisms compared to IL-6 gene expression. The results indicated that the IL-6 polymorphisms do not influence its expression, but IL-6 and IL-6R expression seems to be altered by the presence of H. pylori.

Helicobacter pylori (H. pylori) is one of the main causes of gastric gancer. TNF-related apoptosis-inducing ligand (TRAIL) is a protein able to promote apoptosis in cancer cells, however not in gastric cancer, which presents resistance to apoptosis via TRAIL. It is believed that MicroRNA-106b-5p might be involved in this resistance, although its role in Gastric Cancer is unclear. We aimed to determine the expression of microRNA-106b-5p and TRAIL in patients with gastric diseases, infected by H. pylori, and understand the relationship between these genes and their role in apoptosis and the gastric cancer pathways. H. pylori was detected by PCR, gene expression analysis was performed by real-time-qPCR, and bioinformatics analysis was performed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Cytoscape software. A total of 244 patients were divided into groups (Control, Gastritis, and Cancer); H. pylori was detected in 42.2% of the samples. The cancer group had a poor expression of TRAIL (p < 0.0001) and overexpression of microRNA-106b-5p (p = 0.0005), however, our results confirmed that these genes are not directly related to each other although both are apoptosis-related regulators. Our results also indicated that H. pylori decreases microRNA-106b-5p expression and that this is a carcinogenic bacterium responsible for gastric diseases.

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