Effect of dry-sausage starter culture and endogenous yeasts on Aspergillus westerdijkiae and Penicillium nordicum growth and OTA production

Processed meat products frequently suffer from fungal and mycotoxin contamination, mostly ochratoxin A (OTA). Penicillium nordicum is considered responsible for this contamination, but Aspergillus westerdijkiae has recently been associated with high levels of OTA in meat products. Several biocontrol agents have been tested against P. nordicum growth and OTA production in meat products, but A. westerdijkiae has not been considered. The aim of this work was to evaluate in vitro the effect of a commercial starter culture used in sausage fermentation and of sausage-native yeasts on OTA production by A. westerdijkiae, as compared with the highly studied P. nordicum, in meat-based culture media. Four representative yeasts isolated from dry-cured sausage and a commercial starter culture were co-inoculated with both fungi in different meat-based media, under varying conditions. Fungal growth was determined by measuring colony diameter, and OTA production was quantified by HPLC-FLD. A. westerdijkiae was significantly stimulated to produce OTA under all tested conditions, and, in ham, OTA production by P. nordicum was stimulated by co-culture with the starter culture. In conclusion, endogenous or added microorganisms enrolled in fermentation or in biocontrol in meat products seem to exert varying responses on different ochratoxigenic fungi, thus leading to unforeseen safety problems.This work was supported by the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO [UID/AGR/00690/2013]info:eu-repo/semantics/publishedVersio

Induction of cytotoxicity of Pelagia noctiluca venom causes reactive oxygen species generation, lipid peroxydation induction and DNA damage in human colon cancer cells

<p>Abstract</p> <p>Background</p> <p>The long-lasting and abundant blooming of <it>Pelagia noctiluca </it>in Tunisian coastal waters compromises both touristic and fishing activities and causes substantial economic losses. Determining their molecular mode of action is, important in order to limit or prevent the subsequent damages. Thus, the aim of the present study was to investigate the propensity of <it>Pelagia noctiluca </it>venom to cause oxidative damage in HCT 116 cells and its associated genotoxic effects.</p> <p>Results</p> <p>Our results indicated an overproduction of ROS, an induction of catalase activity and an increase of MDA generation. We looked for DNA fragmentation by means of the comet assay. Results indicated that venom of <it>Pelagia noctiluca </it>induced DNA fragmentation. SDS-PAGE analysis of <it>Pelagia noctiluca </it>venom revealed at least 15 protein bands of molecular weights ranging from 4 to 120 kDa.</p> <p>Conclusion</p> <p>Oxidative damage may be an initiating event and contributes, in part, to the mechanism of toxicity of <it>Pelagia noctiluca </it>venom.</p

Metabolism of triflumuron in the human liver: Contribution of cytochrome P450 isoforms and esterases.

Abstract Triflumuron (TFM) is a benzoylurea insecticide commonly used in Tunisian agriculture and around the world to control crop pests and flies as a promising alternative to conventional insecticides for its arthropod specificity and low toxicity. From the evidence available in animal models, it can be expected that the metabolism of TFM is catalyzed by cytochrome P450 (CYP) and esterases. However, no data are available on human metabolism of TFM with regards to phase I metabolism and CYP isoform specificity. Hence, this manuscript describes experimental investigations to underpin in vitro phase I TFM metabolism in human samples for the first time. TFM biotransformation by recombinant human CYPs was characterized, then human liver microsomes (HLM) and chemical specific inhibitors have been used to identify the relative contribution of CYPs and esterases. Our results showed that all CYP isoforms were able to metabolize TFM with different affinity and efficiency. The relative contribution based both on the kinetic parameters and the CYP hepatic content was 3A4 > >2C9 > 2C8 > 2A6 > 1A2 > 2B6 > 2D6 > 2C19 > 2C18 > 1A1 at low TFM concentration, whilst at high TFM concentration it was 1A2 > >2C9 = 3A4 = 2A6 > 2C19 > 2B6 = 2C8 > 2D6 > 1A1 > 2C18. Experiments with HLMs confirmed the involvement of the most relevant CYPs in the presence of specific chemical inhibitors with a catalytic efficiency (Cliapp) lower by an order of magnitude compared with recombinant enzymes. Esterases were also relevant to the overall TFM kinetics and metabolism, with catalytic efficiency higher than that of CYPs. It is foreseen that such isoform-specific information in humans will further support in silico models for the refinement of the human risk assessment of single pesticides or mixtures

Mechanisms underlying the effect of commercial starter cultures and a native yeast on ochratoxin A production in meat products

Processed meat products are of worldwide importance, but they are highly prone to fungal and ochratoxin A (OTA) contamination. In previous studies, several Lactic Acid Bacteria (LAB) and yeasts have been tested as biocontrol agents against P. nordicum growth and OTA production in meat products, with promising results. However, A. westerdijkiae has been poorly studied for this matrix. The aim of this work was to evaluate in vitro the mechanisms underlying the effects of a commercial starter culture and of a meat-native Candida zeylanoides strain on the growth and OTA production of P. nordicum and A. westerdijkiae, by co-culture in ham and sausage-based media under different conditions. In ham medium, C. zeylanoides live cells, cell broth and diffused compounds significantly inhibited OTA production by P. nordicum, but live cells of the starter culture significantly increased it. For A. westerdijkiae strong and significant stimulation was observed by direct contact in both media. In conclusion, ochratoxigenic fungi do not all respond to antagonistic microorganisms in the same way. This study sheds some light on the mechanisms behind the different effects of microorganisms.This work was supported by the Foundatiion for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO [UID/AGR/00690/2019].info:eu-repo/semantics/publishedVersio

The implication of ROS production on triflumuron-induced oxidative stress and genotoxicity in human colon carcinoma (HCT-116) cells

The aim of this study is to evaluate the cytotoxic and the genotoxic effects of triflumuron (TFM) on human colon carcinoma cells (HCT-116). Indeed, TFM is used to protect vegetables, fruits, and domestic animals against a large spectrum of parasites causing animal and human disorders. However, studies revealing its toxicity and its mode of action in mammalian systems remain very limited. We monitored our work with the cytotoxicity assay starting with the cell viability test, the ROS generation, the malondialdehyde (MDA) production, the DNA fragmentation, and the measurement of some antioxidant enzymes activities such as catalase, superoxide dismutase, and the glutathione S-transferase. Also, we measured the mitochondrial transmembrane potential. We showed that TFM induced a dose-dependent cell death. This decrease in cell viability was accompanied by a significant reduction in the mitochondrial membrane potential. We also have shown that TFM induced oxidative stress as revealed by the generation of reactive oxygen species, the increase of the MDA levels, and the activation of the antioxidant enzymes. Moreover, our results indicated that TFM induced DNA damage in HCT-116 cells as monitored by the comet assay. We demonstrate, for the first time, the cytotoxic and the genotoxic potentials of TFM on human cultured cells

In vitro interaction of the pesticides flupyradifurone, bupirimate and its metabolite ethirimol with the ATP-binding cassette transporter G2 (ABCG2)

[EN] ABCG2 is an ATP-binding cassette efflux transporter that is expressed in absorptive and excretory organs such as liver, intestine, kidney, brain and testis where it plays a crucial physiological and toxicological role in protecting cells against xenobiotics, affecting pharmacokinetics of its substrates. In addition, the induction of ABCG2 expression in mammary gland during lactation is related to active secretion of many toxicants into milk. In this study, the in vitro interactions between ABCG2 and three pesticides flupyradifurone, bupirimate and its metabolite ethirimol were investigated to check whether these compounds are substrates and/or inhibitors of this transporter. Using in vitro transepithelial assays with cells transduced with murine, ovine and human ABCG2, we showed that ethirimol and flupyradifurone were transported efficiently by murine Abcg2 and ovine ABCG2 but not by human ABCG2. Bupirimate was not found to be an in vitro substrate of ABCG2 transporter. Accumulation assays using mitoxantrone in transduced MDCK-II cells suggest that none of the tested pesticides were efficient ABCG2 inhibitors, at least in our experimental conditions. Our studies disclose that ethirimol and flupyradifurone are in vitro substrates of murine and ovine ABCG2, opening the possibility of a potential relevance of ABCG2 in the toxicokinetics of these pesticides.S

Moringa oleifera Protects SH-SY5YCells from DEHP-Induced Endoplasmic Reticulum Stress and Apoptosis

Moringa oleifera (MO) is a medicinal plant that has been shown to possess antioxidant, anticarcinogenic and antibiotic activities. In a rat model, MO extract (MOe) has been shown to have a protective effect against brain damage and memory decline. As an extending study, here, we have examined the protective effect of MOe against oxidative stress and apoptosis caused in human neuroblastome (SH-SY5Y) cells by di-(2-ethylhexyl) phthalate (DEHP), a plasticizer known to induce neurotoxicity. Our data show that MOe prevents oxidative damage by lowering reactive oxygen species (ROS) formation, restoring mitochondrial respiratory chain complex activities, and, in addition, by modulating the expression of vitagenes, i.e., antioxidant proteins Nrf2 and HO-1. Moreover, MOe prevented neuronal damage by partly inhibiting endoplasmic reticulum (ER) stress response, as indicated by decreased expression of CCAAT-enhancer-binding protein homologous protein (CHOP) and Glucose-regulated protein 78 (GRP78) proteins. MOe also protected SH-SY5Y cells from DEHP-induced apoptosis, preserving mitochondrial membrane permeability and caspase-3 activation. Our findings provide insight into understanding of molecular mechanisms involved in neuroprotective effects by MOe against DEHP damag

Effect of commercial starter cultures and native yeasts on Ochratoxin A production in meat products

Ochratoxin A (OTA) is one of the most important mycotoxins in animal and human food chains, and its distribution is universal. Increased oxidative stress, inhibition of protein synthesis, and DNA damage are some of OTA’s mechanisms of action. It is nephrotoxic, teratogenic, immunotoxigenic and carcinogenic. OTA is produced by several strains of Penicillium and Aspergillus species. In dry-cured and fermented meat products, it is strongly associated with Penicillium nordicum, but Aspergillus westerdijkiae, a strong OTA producer usually associated with contamination of coffee beans, has also been found to be responsible for high OTA levels in cured meat products. Because of its harmful effects, many efforts have been put on the development of strategies able to reduce the accumulation of OTA in food products, either by inhibition of fungal growth, inhibition of OTA production or OTA degradation. This work aimed to evaluate the role of yeasts, previously isolated from meat products, and of a commercial starter culture, on the growth of OTA-producing fungi as well as on OTA production, by using meat-based culture media as model systems. A commercial starter culture and 2 yeasts (Candida zeylanoides and Rhodotorula mucilaginosa) isolated from pork sausage were co-inoculated with P. nordicum and A. westerdijkiae separately in three meat-based culture media - ham, traditional sausage and industrial sausage - at different conditions: 15 °C and 20 °C; water activity 0.99, 0.98 and 0.96, for 15 days. Fungal growth was determined by measuring colony diameter and OTA was quantified by HPLC-FLD after extraction with methanol. Results showed that P. nordicum was only able to produce OTA in ham-based medium, with significant reduction of OTA production caused by all co-cultures, being C. zeylenoides the most effective. On the other hand, all co-cultures of A. westerdijkiae lead to a significant stimulation of OTA production, when compared with the control (A. westerdijkiae only). This is the first study evaluating the effects of either native or commercial starter cultures on the OTA-producing fungus A. westerdijkiae in meat products, and it highlights the need to account for all mycotoxigenic fungi potentially present in food products. Studies are currently being developed to try to understand the mechanism behind these unexpected results.N/

Paired comparison or exhaustive classification to explain consumers' preferences

Based on experimental designs, conjoint analysis is a statistical methodwidely used in data analysis. Its main objective is to explain consumers’ preferencesfor a product according to its attributes.We are interested by the full profile method in conjoint analysis under its two forms:exhaustive classification and paired comparison which is more realistic. One of themajor problems encountered while performing theses methods is the abundance ofproducts presented to the interviewee. The number of pairs is much more importantthan the number of products which causes a theoretical loss of efficiency.We show, empirically, through several real cases an equivalence between both formsof full profile in terms of model adjustment, market shares and importance’s ofutilities.We tested these results on several examples and several numbers of products. Weconfirm our findings by simulations