Antibacterial, antibiofilm, and cytotoxic activities and chemical compositions of Peruvian propolis in an in vitro oral biofilm.

Background: Natural products with antibacterial potential have begun to be tested on biofilm models, bringing us closer to understanding the response generated by the complex microbial ecosystems of the oral cavity. The objective of this study was to evaluate the antibacterial, antibiofilm, and cytotoxic activities and chemical compositions of Peruvian propolis in an in vitro biofilm of Streptococcus gordonii and Fusobacterium nucleatum. Methods: The experimental work involved a consecutive, in vitro, longitudinal, and double-blinded study design. Propolis samples were collected from 13 different regions of the Peruvian Andes. The disk diffusion method was used for the antimicrobial susceptibility test. The cytotoxic effect of propolis on human gingival fibroblasts was determined by cell viability method using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay, and the effect of propolis on the biofilm was evaluated by confocal microscopy and polymerase chain reaction (PCR). Results: The 0.78 mg/mL and 1.563 mg/mL concentrations of the methanolic fraction of the chloroform residue of Oxapampa propolis showed effects on biofilm thickness and the copy numbers of the srtA gene of S. gordonii and the radD gene of F. nucleatum at 48 and 120 hours, and chromatography (UV, λ 280 nm) identified rhamnocitrin, isorhamnetin, apigenin, kaempferol, diosmetin, acacetin, glycerol, and chrysoeriol. Conclusions: Of the 13 propolis evaluated, it was found that only the methanolic fraction of Oxapampa propolis showed antibacterial and antibiofilm effects without causing damage to human gingival fibroblasts. Likewise, when evaluating the chemical composition of this fraction, eight flavonoids were identified.

Iron responsive-like elements in the parasite Entamoeba histolytica.

In Entamoeba histolytica, iron modulates virulence and gene expression via unknown regulatory mechanisms. The existence of a posttranscriptional iron regulatory system parallel with the iron-responsive element (IRE)/iron regulatory protein (IRP) system in the protozoan Trichomonas vaginalis has recently been reported. Due to their evolutionary closeness and the importance of iron for growth and virulence in these protozoa, we hypothesized the existence of an IRE/IRP-like mechanism in E. histolytica. To determine the presence of IRE-like elements in some mRNAs from this parasite, we performed in silico analyses of the 5'- and 3'-UTRs of mRNAs encoding virulence factors and cytoskeleton, ribosomal and metabolism proteins. The Zuker mfold software predicted IRE-like secondary structures in 52 of the 135 mRNAs analysed. However, only nine structures shared sequence similarity with the apical loop sequence (CAGUGN) of the previously reported human IRE-ferritin, whereas the GUU/UUG protozoan-specific motif was detected in 23 stem-loop structures. A new motif, AUU/AUUU, was also observed in 23 structures, suggesting the possible existence of an amoeba-specific motif. Additionally, cross-linking and RNA electrophoretic mobility shift assays showed specific RNA-protein interactions, using as a model two amoebic IRE-like elements from iron-regulated mRNAs and HeLa, T. vaginalis and E. histolytica cytoplasmic proteins. Our data suggest the presence of a posttranscriptional iron regulatory IRE/IRP-like mechanism in E. histolytica.

Corrigendum to "α-Actinin TvACTN3 of Trichomonas vaginalis Is an RNA-Binding Protein That Could Participate in Its Posttranscriptional Iron Regulatory Mechanism".

[This corrects the article DOI: 10.1155/2014/424767.].

α -Actinin TvACTN3 of Trichomonas vaginalis is an RNA-binding protein that could participate in its posttranscriptional iron regulatory mechanism.

Trichomonas vaginalis is a sexually transmitted flagellated protist parasite responsible for trichomoniasis. This parasite is dependent on high levels of iron, favoring its growth and multiplication. Iron also differentially regulates some trichomonad virulence properties by unknown mechanisms. However, there is evidence to support the existence of gene regulatory mechanisms at the transcriptional and posttranscriptional levels that are mediated by iron concentration in T. vaginalis. Thus, the goal of this study was to identify an RNA-binding protein in T. vaginalis that interacts with the tvcp4 RNA stem-loop structure, which may participate in a posttranscriptional iron regulatory mechanism mediated by RNA-protein interactions. We performed RNA electrophoretic mobility shift assay (REMSA) and supershift, UV cross-linking, Northwestern blot, and western blot (WB) assays using cytoplasmic protein extracts from T. vaginalis with the tvcp4 RNA hairpin structure as a probe. We identified a 135-kDa protein isolated by the UV cross-linking assays as α-actinin 3 (TvACTN3) by MALDI-TOF-MS that was confirmed by LS-MS/MS and de novo sequencing. TvACTN3 is a cytoplasmic protein that specifically binds to hairpin RNA structures from trichomonads and humans when the parasites are grown under iron-depleted conditions. Thus, TvACTN3 could participate in the regulation of gene expression by iron in T. vaginalis through a parallel posttranscriptional mechanism similar to that of the IRE/IRP system.