Lactic acid bacterial extracts as anti-Helicobacter pylori: a molecular approach

BACKGROUND

Helicobacter pylori (H. pylori) infection, the main cause of chronic gastritis, increases gastric cancer risk. Antibiotics-based H. pylori eradication treatment is 90% effective. However, it is expensive and causes side effects and antibiotic resistance. Lactic acid bacteria (LAB) could present a low-cost, large-scale alternative solution to prevent or decrease H. pylori colonization.

AIM

This work aimed to study the inhibitory effects of LAB strains on the growth and pathogenic activity of H. pylori stains. To this end, we have selected the most virulent H. pylori strains (out of 20 mucosal antral biopsies) regarding cellular vacuolization and induction of apoptosis/necrosis.

METHOD

The selection of H. pylori pathogenic strains (clinically pre-isolated) were based on their impact of VacA activities on Hep-2 cell line, induction of apoptosis and necrosis in Caco-2 cell line. The Inhibitory effect of LAB strains on the invasion was carried out using the Caco-2 and Hela cell lines, where, they were co-cultured with the pathogenic H. pylori in the presence or absence of LAB extracts. The effect of LAB extracts on TNF-α secretion which induced by H. pylori-LPS was carried out by RT-qPCR.

RESULTS

L. bulgaricus DSMZ 20080, L. acidophilus and L. plantarum (studied previously and reported as high antioxidant candidate strains) showed the highest anti-pylori activities with inhibition ranged from 51.46 to 88.19%, they preventing the adhesion, invasion and DNA fragmentation of cell lines. In addition, they could reduce the TNF-α expression by 62.13%.

CONCLUSION

LAB extracts could inhibit the bacterial adhesion and invasion, gastric inflammation and DNA fragmentation induced by Helicobacter pylori.

Downregulation of K(+) channel genes expression in type I diabetic cardiomyopathy

Type I diabetic cardiomyopathy has consistently been shown to be associated with decrease of repolarising K(+) currents, but the mechanisms responsible for the decrease are not well defined. We investigated the streptozotocin (STZ) rat model of type I diabetes. We utilized RNase protection assay and Western blot analysis to investigate the message expression and protein density of key cardiac K(+) channel genes in the diabetic rat left ventricular (LV) myocytes. Our results show that message and protein density of Kv2.1, Kv4.2, and Kv4.3 are significantly decreased as early as 14 days following induction of type I diabetes in the rat. The results demonstrate, for the first time, that insulin-deficient type I diabetes is associated with early downregulation of the expression of key cardiac K(+) channel genes that could account for the depression of cardiac K(+) currents, I(to-f) and I(to-s). These represent the main electrophysiological abnormality in diabetic cardiomyopathy and is known to enhance the arrhythmogenecity of the diabetic heart. The findings also extend the extensive list of gene expression regulation by insulin.

Overexpression of protein disulfide isomerase in Aspergillus

One of the major problems with the production of biotechnologically valuable proteins has been the purification of the product. For Escherichia coli and Saccharomyces cerevisiae, there are several techniques for the purification of intracellular proteins, but these are time consuming and often result in poor yields. Purification can be considerably facilitated, if the product is secreted from the host cell. In the work presented, we have constructed an expression vector (pSGNH2) for the secretion of protein disulfide isomerase (PDI; EC 5.3.4.1) from Aspergillus niger, in which the retention signal His-Asp-Glu-Leu (H-D-E-L) was modified to Ala-Leu-Glu-Gln (A-L-E-Q) via the polymerase chain reaction (PCR) method. The PDI gene was placed under the control of the A. oryzae alpha-amylase promoter. This expression vector was transformed into A. niger NRRL3, resulting in PDI secretion into the medium. The catalytic activity of overexpressed PDI from A. niger was indistinguishable from that of PDI isolated from bovine liver. With further strain improvement and optimization of culture conditions, it could be possible to raise the PDI production to the bioprocessing scale.