Genetically Modifying the Insect Gut Microbiota to Control Chagas Disease Vectors through Systemic RNAi

Technologies based on RNA interference may be used for insect control. Sustainable strategies are needed to control vectors of Chagas disease such as Rhodnius prolixus. The insect microbiota can be modified to deliver molecules to the gut. Here, Escherichia coli HT115(DE3) expressing dsRNA for the Rhodnius heme-binding protein (RHBP) and for catalase (CAT) were fed to nymphs and adult triatomine stages. RHBP is an egg protein and CAT is an antioxidant enzyme expressed in all tissues by all developmental stages. The RNA interference effect was systemic and temporal. Concentrations of E. coli HT115(DE3) above 3.35 × 10⁷ CFU/mL produced a significant RHBP and CAT gene knockdown in nymphs and adults. RHBP expression in the fat body was reduced by 99% three days after feeding, returning to normal levels 10 days after feeding. CAT expression was reduced by 99% and 96% in the ovary and the posterior midgut, respectively, five days after ingestion. Mortality rates increased by 24-30% in first instars fed RHBP and CAT bacteria. Molting rates were reduced by 100% in first instars and 80% in third instars fed bacteria producing RHBP or CAT dsRNA. Oviposition was reduced by 43% (RHBP) and 84% (CAT). Embryogenesis was arrested in 16% (RHBP) and 20% (CAT) of laid eggs. Feeding females 10⁵ CFU/mL of the natural symbiont, Rhodococcus rhodnii, transformed to express RHBP-specific hairpin RNA reduced RHBP expression by 89% and reduced oviposition. Modifying the insect microbiota to induce systemic RNAi in R. prolixus may result in a paratransgenic strategy for sustainable vector control.     

The effect of inducing agents on the metabolism of ethidium bromide by isolated rat hepatocytes

The metabolism of ethidium bromide by isolated rat hepatocytes is significantly enhanced by pre-treatment of animals with phenobarbitone (PB) and 3-methylcholanthrene (3-MC). Pre-treatment with PB and 3-MC results in a 2.5- and 1.5-fold increase, respectively in the amount of the principal metabolite, ethidium 8-N-glucuronide, compared with that formed by hepatocytes from untreated rats. The formation of ethidium 3-N-glucuronide is not enhanced by pre-treatment with either PB or 3-MC. Two new metabolites, hydroxyethidium glucuronide and a transient unidentified species, have been detected by HPLC and are formed only by hepatocytes from animals pre-treated with 3-MC.     

Physicochemical characterization of fructooligosaccharides and evaluation of their suitability as a potential sweetener for diabetics

Fructooligosaccharides (FOSs) were prepared from sucrose using fungal fructosyl transferase (FTase) obtained from Aspergillus oryzae MTCC 5154. The resulting mixture consisted of glucose (28-30%), sucrose (18-20%) and fructooligosaccharides (50-54%) as indicated by HPLC analysis. Identification of oligomers present in the mixture of fructooligosaccharides was carried out using NMR spectroscopy and LC-MS. No compounds other than mono-, di-, tri-, tetra- and pentasaccharides were identified in the FOS mixture prepared using FTase. NMR and LC-MS spectra proved the absence of any toxic microbial metabolites of Aspergillus species in FOS thereby emphasizing its safe use as a food ingredient. Animal studies conducted on streptozotocin-induced diabetic rats suggested that the use of FOS as an alternative non-nutrient sweetener is without any adverse effects on various diabetes-related metabolic parameters. Despite the high free-sugar content associated with it, FOS did not further aggravate the hyperglycemia and glucosuria in diabetic animals, even at 10% levels. On the other hand, by virtue of its soluble fibre effect, it has even alleviated diabetic-related metabolic complications to a certain degree.     

Histone acetylation and chromatin remodeling are required for UV-B-dependent transcriptional activation of regulated genes in maize

The nuclear proteomes of maize (Zea mays) lines that differ in UV-B tolerance were compared by two-dimensional gel electrophoresis after UV light treatment. Differential accumulation of chromatin proteins, particularly histones, constituted the largest class identified by mass spectrometry. UV-B-tolerant landraces and the B73 inbred line show twice as many protein changes as the UV-B-sensitive b, pl W23 inbred line and transgenic maize expressing RNA interference constructs directed against chromatin factors. Mass spectrometic analysis of posttranslational modifications on histone proteins demonstrates that UV-B-tolerant lines exhibit greater acetylation on N-terminal tails of histones H3 and H4 after irradiation. These acetylated histones are enriched in the promoter and transcribed regions of the two UV-B-upregulated genes examined; radiation-sensitive lines lack this enrichment. DNase I and micrococcal nuclease hypersensitivity assays indicate that chromatin adopts looser structures around the selected genes in the UV-B-tolerant samples. Chromatin immunoprecipitation experiments identified additional chromatin factor changes associated with the nfc102 test gene after UV-B treatment in radiation-tolerant lines. Chromatin remodeling is thus shown to be a key process in acclimation to UV-B, and lines deficient in this process are more sensitive to UV-B.     

New ultra-short acting hypnotic: synthesis, biological evaluation, and metabolic profile of ethyl 8-oxo-5,6,7,8-tetrahydro-thiazolo[3,2-a][1,3]diazepin-3-carboxylate (HIE-124)

Ethyl 8-oxo-5,6,7,8-tetrahydro-thiazolo[3,2-a][1,3]diazepin-3-carboxylate (HIE-124, 4) is a member of a new generation of ultra-short acting hypnotics. HIE-124 (4) exhibited potent in vivo activity with a rapid onset of action and a short duration of action, with no acute tolerance or noticeable side effects. The metabolic profile of 4 is also performed. HIE-124 (4) has the potential use as a preanesthetic medication, anesthesia inducer, and could be used with thiopental sodium to maintain anesthesia for longer duration.     

Qualitative differences in T‐cell activation by dendritic cell‐derived extracellular vesicle subtypes

Exosomes, nano‐sized secreted extracellular vesicles (EVs), are actively studied for their diagnostic and therapeutic potential. In particular, exosomes secreted by dendritic cells (DCs) have been shown to carry MHC‐peptide complexes allowing efficient activation of T lymphocytes, thus displaying potential as promoters of adaptive immune responses. DCs also secrete other types of EVs of different size, subcellular origin and protein composition, whose immune capacities have not been yet compared to those of exosomes. Here, we show that large EVs (lEVs) released by human DCs are as efficient as small EVs (sEVs), including exosomes, to induce CD4⁺ T‐cell activation in vitro. When released by immature DCs, however, lEVs and sEVs differ in their capacity to orient T helper (Th) cell responses, the former favouring secretion of Th2 cytokines, whereas the latter promote Th1 cytokine secretion (IFN‐γ). Upon DC maturation, however, these functional differences are abolished, and all EVs become able to induce IFN‐γ. Our results highlight the need to comprehensively compare the functionalities of EV subtypes in all patho/physiological systems where exosomes are claimed to perform critical roles.     

Natural antioxidants attenuate mycolactone toxicity to RAW 264.7 macrophages

Mycobacterium ulcerans produces a macrolide exotoxin, mycolactone which suppresses immune cells activity, is toxic to most cells and the key virulence factor in the pathogenesis of Buruli ulcer disease. Mycolactone is reported to mediate the production of reactive oxygen species in keratinocytes; cells that play critical role in wound healing. Increased levels of reactive oxygen species have been shown to disrupt the well-ordered process of wound repair; hence, the function of wound-healing cells such as macrophages, keratinocytes, and fibroblast could be impaired in the presence of the reactive oxygen species mediator, mycolactone. To ensure regeneration of tissues in chronic ulcers, with proper and timely healing of the wounds, natural antioxidants that can combat the effects of induced reactive oxygen species in wound-healing cells ought to be investigated. Reactive oxygen species activity was determined in mycolactone-treated RAW 264.7 macrophages and the scavenging ability of the antioxidants (ascorbic acid, gallic acid, and green tea kombucha) against mycolactone-induced reactive oxygen species (superoxide anions) was assessed using fluorescein probe (DCF-DA) and nitroblue tetrazolium dye. Cytotoxicity of the antioxidants, mycolactone, and the protective effect of the antioxidants on the cells upon treatment with mycolactone were determined using the Alamar blue assay. The expression levels of endogenous antioxidant enzyme genes (superoxide dismutase, catalase, and glutathione peroxidase) in response to mycolactone-mediated reactive oxygen species were determined using RT-qPCR. Mycolactone induced the production of reactive oxygen species in RAW 264.7 macrophages, and the resulting superoxide anions were scavenged by some of the antioxidants. The selected endogenous antioxidant enzyme genes in the macrophages were upregulated in the presence of the antioxidants and mycolactone. The exogenously supplied ascorbic acid and green tea kombucha offered moderate protection to the macrophages against the toxicity of mycolactone. We conclude that the results provide insights into alternate and adjunct therapeutic approaches in Buruli ulcer treatment, which could significantly attenuate the toxicity of the pathogenic factor; mycolactone.