Association between polymorphisms in the csrRS two-component regulatory system and invasive group A streptococcal infection.

The csrRS two-component regulatory system is an important element in the pathogenesis of group A Streptococcus (GAS). The main goal of this study is to understand the association between csrRS polymorphisms and GAS infection. We sequenced the csrRS genes from 172 clinical isolates, including 81 invasive and 91 noninvasive isolates, and then employed phylogenetic analyses to determine the consequences of the csrRS polymorphisms. In total, 13 and 26 polymorphic loci were detected in the csrR and csrS genes, respectively. These polymorphisms constituted 14 csrR and 25 csrS alleles, producing two CsrR and seven CsrS variants, respectively. Three invasive isolates contained an indel in csrS, but no indel was identified in csrR. The frequency and distribution of polymorphisms in csrR and csrS was significantly different between the invasive and noninvasive infection isolates (p < 0.001). For CsrR, only one noninvasive isolate was identified to have a V29I mutation. The amino acid substitutions in CsrS included S32P (0.6 %), E265G (0.6 %), E265K (0.6 %), I332V (1.7 %), and N498K (82.6 %). Isolates with an N498K single mutation were more likely to be associated with invasive infections (p < 0.001). The dN/dS ratio indicated that both csrR and csrS were under purifying selection. The fixation index suggested a moderate evolutionary differentiation of the csrR and csrS alleles between invasive and noninvasive isolates. The identification of these genetic differences within the csrRS loci will provide a better understanding of the pathogenesis of GAS.

Amoxicillin resistance with beta-lactamase production in Helicobacter pylori.

BACKGROUND: Amoxicillin-resistant Helicobacter pylori with minimal inhibitory concentration (MIC) >or= 256 mg L(-1) was isolated from a gastritis patient. The aims were to investigate the mechanism of high-level amoxicillin resistance in H. pylori. MATERIALS AND METHODS: The beta-lactamase production was determined by means of nitrocefin sticks and the presence of gene encoding the beta-lactam antibiotic resistance enzyme TEM beta-lactamase was analysed by polymerase chain reaction (PCR), sequencing and dot-blot hybridization. Sequencing analysis of pbp1A gene was performed and amoxicillin-susceptible isolate was transformed with pbp1A PCR products from the resistant isolate. The expression of hefC efflux system was analysed using real-time quantitative PCR. RESULTS: Activity of beta-lactamase was detected. Sequence analysis showed that the PCR product derived from H. pylori 3778 was identical to the bla(TEM-1) (GenBank accession EU726527). Dot-blot hybridization confirmed the presence of beta-lactamase gene bla(TEM-1.) By transformation of PCR product of mutated pbp1A gene from H. pylori 3778 into amoxicillin-susceptible strain showed that substitutions in Thr(556)-->Ser, Lys(648)-->Gln, Arg(649)-->Lys and Arg(656)-->Pro contribute to low-level amoxicillin resistance. The MIC of amoxicillin for the transformants was 0.75 mg L(-1). Over-expression of hefC was not found. CONCLUSIONS: High-level amoxicillin resistance is associated with beta-lactamase production in H. pylori. Low-level amoxicillin resistance is linked to a point mutation on pbp1A. Because H. pylori can exchange DNA through natural transformation, spreading of bla(TEM-1) amoxicillin resistance gene among H. pylori is a potential threat when treating H. pylori infection.

Omega-3 polyunsaturated fatty acid inhibits the malignant progression of hepatocarcinoma by inhibiting the Wnt/ß-catenin pathway.

OBJECTIVE: Omega-3 polyunsaturated fatty acid (ω-3 PUFA) has been found to possess anti-cancer potential in previous studies. However, the underlying mechanism of ω-3 PUFA in protecting hepatocarcinoma has not been fully elucidated. This study aims to explore the function of ω-3 PUFA in the development of hepatocarcinoma and its potential mechanism. PATIENTS AND METHODS: In this study, human hepatocarcinoma cell line Hep G2 was treated with ω-3 PUFA. Cell counting kit-8 (CCK-8) and cell cloning assay were applied to detect the proliferation of Hep G2 cells. In addition, flow cytometry was performed to analyze the cell cycle and apoptosis rate. At the same time, the effect of ω-3 PUFA on invasion and metastasis of hepatocarcinoma cells were analyzed by transwell assay. Moreover, protein levels of key factors in Wnt/ß-catenin pathway were detected by Western blot. RESULTS: Cell proliferation of Hep G2 cells was decreased after ω-3 PUFA treatment in a time- and dose-dependent manner. CCK-8 assay showed that the IC50 value was 12.8 ± 0.67 µmol/L, 8.8 ± 0.43 µmol/L and 4.6 ± 0.42 µmol/L after ω-3 PUFA treatment for 24 h, 48 h and 72 h, respectively. Besides, ratio of Hep G2 cells blocked at G2/M phase after ω-3 PUFA treatment (5 µmol/L, 10 µmol/L and 20 µmol/L) was increased in a dose-dependent manner (p<0.05). Meanwhile, ω-3 PUFA could increase cell apoptosis (p<0.05) and inhibit cell proliferation. In addition, ω-3 PUFA reduced protein expressions of total, cytoplasmic and nuclear ß-catenin in Hep G2 cells, indicating that the Wnt/ß-catenin pathway is inhibited. Decreased expression levels of Dvl-2, Dvl-3, GSK-3ß (p-ser9), c-myc and survivin, and increased expression levels of GSK-3 (p-tyr216) and Axin-2 were observed in Hep G2 cells treated with ω-3 PUFA, but no significant alteration in total GSK-3ß protein level was observed (p>0.05). CONCLUSIONS: Omega-3 PUFA regulates the malignant progression of hepatocarcinoma by inhibiting proliferation and promoting apoptosis of hepatocarcinoma cells via Wnt/ß-catenin signaling pathway.

Persistent mechanical allodynia positively correlates with an increase in activated microglia and increased P-p38 mitogen-activated protein kinase activation in streptozotocin-induced diabetic rats.

BACKGROUND: In experimental early painful diabetic neuropathy, persistent hyperglycaemia induces dys-regulated sodium channel (Navs) expression in the dorsal root ganglion (DRG) and activates microglia in the spinal dorsal horn (SDH). However, information on diabetes-induced chronic neuropathic pain is limited. Therefore, we investigated abnormal Navs in the DRG and activated glial cells in the SDH of diabetic rats with chronic neuropathic pain. METHODS: Sixty-six rats were divided into diabetic and control groups: control rats (n = 18; 1 mL of normal saline via the right femoral vein) and diabetic rats [n = 48; 60 mg/kg streptozotocin (STZ) via the right femoral vein]. Hindpaw behavioural tests, Navs expression in the DRG, activation of glial cells in the SDH and the number of neurons in the SDH were measured at 1 and 2 weeks, and 1, 2, 3 and 6 months following saline and STZ administration. RESULTS: All diabetic rats exhibited hyperglycaemia from day 7 to 6 months. The diabetic rats decreased withdrawal threshold to mechanical stimuli but had blunted responses to thermal stimuli. Consistent up-regulation of Nav1.3 and down-regulation of Nav1.8 was observed. Microglial cells were activated early in the SDH and lasted for 6 months. A positive correlation between mechanical allodynia, Nav1.3 and microglial activation was observed. In addition, microglia activation in the SDH of STZ-induced diabetes was mediated, in part, by phosphorylation of p-38 mitogen-activated protein kinase. CONCLUSIONS: Diabetic rats showed hindpaw mechanical allodynia for 6 months. Persistent mechanical allodynia was positively associated with sustained increased activation of Nav1.3 and increased p38 phosphorylation in activated microglia.