Generation of an Obese Diabetic Mouse Model upon Conditional Atrx Disruption

Atrx loss was recently ascertained as insufficient to drive pancreatic neuroendocrine tumour (PanNET) formation in mice islets. We have identified a preponderant role of Atrx in the endocrine dysfunction in a Rip-Cre;Atrx^KO genetically engineered mouse model (GEMM). To validate the impact of a different Cre-driver line, we used similar methodologies and characterised the Pdx1-Cre;Atrx^KO (P.Atrx^KO) GEMM to search for PanNET formation and endocrine fitness disruption for a period of up to 24 months. Male and female mice presented different phenotypes. Compared to P.Atrx^WT, P.Atrx^HOM males were heavier during the entire study period, hyperglycaemic between 3 and 12 mo., and glucose intolerant only from 6 mo.; in contrast, P.Atrx^HOM females started exhibiting increased weight gains later (after 6 mo.), but diabetes or glucose intolerance was detected by 3 mo. Overall, all studied mice were overweight or obese from early ages, which challenged the histopathological evaluation of the pancreas and liver, especially after 12 mo. Noteworthily, losing Atrx predisposed mice to an increase in intrapancreatic fatty infiltration (FI), peripancreatic fat deposition, and macrovesicular steatosis. As expected, no animal developed PanNETs. An obese diabetic GEMM of disrupted Atrx is presented as potentially useful for metabolic studies and as a putative candidate for inserting additional tumourigenic genetic events.

Characterisation of an Atrx Conditional Knockout Mouse Model: Atrx Loss Causes Endocrine Dysfunction Rather Than Pancreatic Neuroendocrine Tumour

Simple Summary

ATRX and DAXX mutations occur in 30–40% of pancreatic neuroendocrine tumours (PanNETs), and there are no reports in the literature of any genetically engineered mouse model (GEMM) evaluating the effect of Atrx disruption as a putative driver event on PanNET initiation. We created a novel GEMM with Atrx conditional disruption in β cells. We observed that this genetic alteration, per se, was not tumourigenic, but we reported novel roles of Atrx on endocrine function, which resulted in dysglycaemia and the exacerbation of inflammageing (increased pancreatic inflammation and hepatic steatosis).

Abstract

ATRX is a chromatin remodeller that maintains telomere homeostasis. Loss of ATRX is described in approximately 10% of pancreatic neuroendocrine tumours (PanNETs) and associated with poorer prognostic features. Here, we present a genetically engineered mouse model (GEMM) addressing the role of Atrx loss (Atrx^KO) in pancreatic β cells, evaluating a large cohort of ageing mice (for up to 24 months (mo.)). Atrx loss did not cause PanNET formation but rather resulted in worsening of ageing-related pancreatic inflammation and endocrine dysfunction in the first year of life. Histopathological evaluation highlighted an exacerbated prevalence and intensity of pancreatic inflammation, ageing features, and hepatic steatosis in Atrx^KO mice. Homozygous floxed mice presented hyperglycaemia, increased weights, and glucose intolerance after 6 months, but alterations in insulinaemia were not detected. Floxed individuals presented an improper growth of their pancreatic endocrine fraction that may explain such an endocrine imbalance. A pilot study of BRACO-19 administration to Atrx^KO mice resulted in telomere instability, reinforcing the involvement of Atrx in the maintenance of β cell telomere homeostasis. Thereby, a non-obese dysglycaemic GEMM of disrupted Atrx is here presented as potentially useful for metabolic studies and putative candidate for inserting additional tumourigenic genetic events.

Redox mechanisms of conversion of Cr(VI) to Cr(III) by graphene oxide-polymer composite

Alternative methods of aqueous chromium removal have been of great research interest in recent years as Cr (VI) is a highly toxic compound causing severe human health effects. To achieve better removal of Cr (VI), it is essential to understand the chemical reactions that lead to the successful removal of Cr species from the solution. Recent studies have demonstrated that graphene oxide (GO) based polymer beads cannot only adsorb Cr (VI) via electrostatic attractions but also reduce it to Cr (III), which is a much less toxic form of chromium. This conversion and the functional groups involved in this conversion, until now, were not elucidated. In the present study, we employed X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy to investigate the conversion pathway of Cr (VI) to Cr (III) in graphene-based polymer beads. The results showed that alcoholic groups are converted to carboxylic groups while reducing Cr (VI) to Cr (III). The inclusion of GO in the polymer beads dramatically increased the potential of Cr (VI) uptake and conversion to Cr (III), indicating polymers and nanomaterials containing alcohol groups can remove and convert chromium in water. Other functional groups present in the polymer bead play an important role in adsorption but are not involved in the conversion of Cr (VI) to Cr (III).

Correction to: In vitro mechanistic studies on α-amanitin and its putative antidotes

In the original publication of the article.

In vitro mechanistic studies on α-amanitin and its putative antidotes

α-Amanitin plays a key role in Amanita phalloides intoxications. The liver is a major target of α-amanitin toxicity, and while RNA polymerase II (RNA Pol II) transcription inhibition is a well-acknowledged mechanism of α-amanitin toxicity, other possible toxicological pathways remain to be elucidated. This study aimed to assess the mechanisms of α-amanitin hepatotoxicity in HepG2 cells. The putative protective effects of postulated antidotes were also tested in this cell model and in permeabilized HeLa cells. α-Amanitin (0.1-20 µM) displayed time- and concentration-dependent cytotoxicity, when evaluated through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and neutral red uptake assays. Additionally, α-amanitin decreased nascent RNA synthesis in a concentration- and time-dependent manner. While α-amanitin did not induce changes in mitochondrial membrane potential, it caused a significant increase in intracellular ATP levels, which was not prevented by incubation with oligomycin, an ATP synthetase inhibitor. Concerning the cell redox status, α-amanitin did not increase reactive species production, but caused a significant increase in total and reduced glutathione, which was abolished by pre-incubation with the inhibitor of gamma-glutamylcysteine synthase, buthionine sulfoximine. None of the tested antidotes [N-acetyl cysteine, silibinin, benzylpenicillin, and polymyxin B (PolB)] conferred any protection against α-amanitin-induced cytotoxicity in HepG2 cells or reversed the inhibition of nascent RNA caused by the toxin in permeabilized HeLa cells. Still, PolB interfered with RNA Pol II activity at high concentrations, though not impacting on α-amanitin observed cytotoxicity. New hepatotoxic mechanisms of α-amanitin were described herein, but the lack of protection observed in clinically used antidotes may reflect the lack of knowledge on their true protection mechanisms and may explain their relatively low clinical efficacy.

An effective antidotal combination of polymyxin B and methylprednisolone for α-amanitin intoxication

Amanita phalloides is one of the most toxic mushrooms worldwide, and it is involved in the majority of human fatal cases of mushroom poisoning. α-Amanitin, the most deleterious toxin of A. phalloides to humans, inhibits RNA polymerase II (RNAPII), causing hepatic and renal failure. Previously, we have shown that polymyxin B (polB) reverts α-amanitin inhibition of RNAPII, although it was not able to guarantee the full survival of α-amanitin-intoxicated mice or prevent α-amanitin pro-inflammatory effects. α-Amanitin is also a substrate of the organic-anion-transporting polypeptide 1B3 (OATP1B3) and Na(+)-taurocholate cotransporter polypeptide (NTCP) transporters. Therefore, in the present work, we used a combination of polB [(2.5 mg/kg intraperitoneal (i.p.)] with the anti-inflammatory and NTCP inhibitor drug, methylprednisolone (MP) (10 mg/kg i.p.), as an attempt to fully revert α-amanitin-induced toxicity (0.33 mg/kg i.p.) in CD-1 mice. Results showed that the administration of the polB + MP combination, 4 h after α-amanitin, led to the full survival of the intoxicated animals, with a significant attenuation of α-amanitin-induced renal and hepatic necrosis. Also, the combination polB + MP led to a decrease of aminotransferase plasma levels, of the renal myeloperoxidase activity and of renal inflammatory cell infiltrate promoted by α-amanitin, although not preventing any of the hepatic pro-inflammatory effect of the toxin. The obtained results indicate that this combination may represent an important and valuable therapeutic approach to be used against α-amanitin intoxication.

Molecular identification and microbiological evaluation of isolates from equipments and food contact surfaces in a hospital Food and Nutrition Unit

The hygienic and sanitary control in Food and Nutrition Units (FNU) is considered a standard procedure to produce adequate meals and reduce the risk of foodborne diseases and hospital infections. This study aimed to evaluate the isolation and identification of bacteria from equipment and food contact surfaces in a hospital FNU as well as to evaluate the sanitary condition. Likewise, it was analyzed the adhesion of the microorganisms on polyethylene cutting boards. The presence of aerobic mesophilic microorganisms, yeasts, molds, coagulase-positive staphylococci, coliform and fecal coliform, and Escherichia coli were analyzed on eating tables, countertop surfaces and cutting boards used for meat or vegetable handling, and equipment such as microwaves and refrigerators. The molecular identification it was done by 16S rRNA gene sequencing. The adhesion of the microorganisms (biofilm formation) on meat and vegetable cutting boards was also evaluated by scanning electron microscopy. The results showed high numbers of all microorganisms, except for E. coli , which was not observed in the samples. The molecular analysis identified species of the Enterobacteriaceae family and species of the Pseudomonadaceae family. Scanning electron microscopy analyses revealed bacterial adhesion on the cutting board surfaces. The results obtained in this study indicated that the hygienic conditions of surfaces like plastic cutting boards and equipment in this hospital FNU were inadequate. The achievement and application of standard operating procedures could positively help in the standardization of sanitary control, reducing the microbial contamination and providing a safe food to hospitalized patients.

Diversity of hydrocarbon-degrading Klebsiella strains isolated from hydrocarbon-contaminated estuaries

AIMS

To investigate the diversity and the catabolic capacity of oil-degrading Klebsiella strains isolated from hydrocarbon-contaminated sediments in Santos-São Vicente estuary systems in Brazil.

METHODS AND RESULTS

Klebsiella strains obtained from the estuary were characterized using 16S rRNA gene sequencing and BOX-PCR patterns, testing their catabolic capacity to degrade toluene, xylene, naphthalene and nonane, and identifying the catabolic genes present in the oil-degrading strains. Results show that Klebsiella strains were widespread in the estuary. Twenty-one isolates from the Klebsiella genus were obtained; 14 had unique BOX patterns and were further investigated. Among four distinct catabolic genes tested (todC1, ndoB, xylE and alkB1), only the todC1 gene could be amplified in two Klebsiella strains. The biodegradation assay showed that most of the strains had the ability to degrade all of the tested hydrocarbons; however, the strains displayed different efficiencies.

CONCLUSIONS

The oil-degrading Klebsiella isolates obtained from the estuary were closely related to Klebsiella pneumoniae and Klebsiella ornithinolytica. The isolates demonstrated a substantial degree of catabolic plasticity for hydrocarbon degradation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study show that several strains from the Klebsiella genus are able to degrade diverse hydrocarbon compounds. These findings indicate that Klebsiella spp. can be an important part of the oil-degrading microbial community in estuarine areas exposed to sewage.

Viability and sporulating capability of Coelomycetes preserved under a range of different storage regimes

The viability and sporulating capability of 45 Coelomycetes strains were evaluated. Strain subcultures were maintained under mineral oil, in soil and on agar slant for different periods of time lasting as long as 50 years, 39 years and 2 years, respectively. Of the 34 strains preserved under mineral oil, 20 maintained their viability but lost the sporulating capability with exception of one strain of Pestalotiopsis guepinii. Of the 16 strains also preserved in soil only one was viable and it was not able to sporulate. All 12 endophytic strains, 11 preserved on agar slant and one under mineral oil remained viable; however, the strain preserved under mineral oil lost its sporulating capability, while the strains on agar slant were only able to sporulate after culturing on sterilized alfalfa twigs. The results demonstrate that routine monitoring, and the use of different preservation methods, specially with the addition of sterilized plant tissue on the culture media for promoting conidiomata formation, is necessary for the success of the Coelomycetes long-term preservation.