Immunomodulatory Effects of Pure Cylindrospermopsin in Rats Orally Exposed for 28 Days

Quercetin counteracts monosodium glutamate to mitigate immunosuppression in the thymus and spleen via redox-guided cellular signaling

BACKGROUND

Chronic inflammation brought on by oxidative stress can result in several immunopathologies. Natural compounds with antioxidant characteristics, like quercetin, have shown effectiveness in reducing oxidative damage and regulating the immune response.

PURPOSE

The commonly used food additive monosodium glutamate (M) causes immunosuppression by disrupting redox equilibrium and inducing oxidative stress. The goal of this work is to examine the therapeutic potential of quercetin against immunotoxicity brought on by M, revealing the molecular route implicated in such immunopathology by targeting the thymus and spleen, to support the development of future anti-inflammatory and antioxidant therapies.

STUDY DESIGN AND METHODS

M-fed rats were employed as an immunotoxicity model and were supplemented with quercetin for four weeks. Hematological and biochemical parameters were measured; H&E staining, immunohistochemistry, flow cytometry, real-time quantitative PCR, and western blotting were performed.

RESULTS

Based on the findings, TLR4 was activated by M to cause oxidative stress-mediated inflammation, which was alleviated by the supplementation of quercetin by modulating redox homeostasis to neutralize free radicals and suppress the inflammatory response. To prevent M-induced inflammation, quercetin demonstrated anti-inflammatory functions by blocking NF-kB activation, lowering the production of pro-inflammatory cytokines, and increasing the release of anti-inflammatory cytokines. By normalizing lipid profiles and lowering the potential risk of immunological deficiency caused by M, quercetin also improves lipid metabolism. Additionally, it has shown potential for modifying insulin levels, suggesting a possible function in controlling M-induced alteration in glucose metabolism. The addition of quercetin to M enhanced the immune response by improving immunoglobulin levels and CD4/CD8 expression in the thymus and spleen. Additionally, quercetin inhibited apoptosis by controlling mitochondrial caspase-mediated cellular signaling, suggesting that it may be able to halt cell death in M-fed rats.

CONCLUSION

The results of this study first indicate that quercetin, via modulating redox-guided cellular signaling, has a promising role in reducing immune disturbances. This study illuminates the potential of quercetin as a safe, natural remedy for immunopathology caused by M, including thymic hypoplasia and/or splenomegaly, and paves the way for future anti-inflammatory and antioxidant supplements.

The two-way immunotoxicity in native fish induced by exudates of Microcystis aeruginosa: Immunostimulation and immunosuppression

Secondary metabolites of cyanobacterial blooms have caused serious risks to aquatic animals. The immune system is an important barrier for fish against pollutants in aquatic systems. The immunetoxic mechanism of the exudates of Microcystis aeruginosa (MaE) on fish was lacking due to the complex components of MaE. In this project, Sinocyclocheilus grahami was used as the model to study the immunotoxic effects of MaE and PHS (one of the main components of the MaE) in fish. The immunosuppression effects of MaE are mainly in, decreased head-kindey index, damaged tissue structure of head-kidney and downregulated NF-κB, IL-1β. PHS induce immunostimulation via, increasing spleen index, apparently increasing leucocytes, increasing the IgM and lysozyme levels in serum and skin mucus, upregulating protease in skin mucus, increasing pro-immunologic factors (IL-1β, IL-6, IL-8, IL-10, TNF-α and NF-κB), probably activating the TLRs/NF-κB, MAPK, FoxO1 and PPARγ signaling pathways. Therefore, our research identified potential data gaps that how the exudates of cyanobacteria induces immunostimulation and immunosuppression from immune organs level to skin mucus to blood cells to inflammatory factors to potential molecular initiating event of MaE and PHS. Further research is needed to obtain a deeper view of the molecular mechanisms involved in MaE and PHS immunotoxicity and its consequences in long-time exposures.

Risk assessment and environmental consequences of the use of the Allium-derived compound propyl-propane thiosulfonate (PTSO) in agrifood applications

The organosulfur compound propyl-propane thiosulfonate (PTSO), mainly found in Allium cepa, has a promising use in the agrifood industry. To confirm its safety for livestock, consumers, and environment, toxicological assessment is needed. In this regard, endocrine-disrupting chemicals (EDCs) are in the spotlight of research. Therefore, as part of the risk assessment of PTSO, in the present work, an in vivo study was performed in mice exposed to PTSO to investigate its potential reproductive toxicity considering fertility, genetic and endocrine endpoints. Five-weeks-old CD1 mice (80 males, 80 females) were exposed for 11 or 16 weeks (males or females, respectively) to different doses of PTSO (0, 14, 28 and 55 mg PTSO/kg b.w./day; 20 animals per group and sex) through the food pellets. No clinical observations or mortality and no changes in absolute organ weights and relative organ weights/body weight or brain ratios occurred during the study. The estrous cycle did not undergo any significant toxicologically relevant change. Most of the sex hormones displayed normal values. Some alterations in the expression of some genes related to reproduction is only observed in females, but they do not appear to have consequences in the development of sex organs. Docking results showed the impossibility of stable binding to estrogen and androgen receptors. Considering all the results obtained, the safe profile of PTSO can be confirmed for different agrifood applications at the conditions assayed.

Potential oestrogenic effects (following the OECD test guideline 440) and thyroid dysfunction induced by pure cyanotoxins (microcystin-LR, cylindrospermopsin) in rats

Potential endocrine-disrupting properties of cyanotoxins, such as microcystin-LR (MC-LR) and cylindrospermopsin (CYN) are of concern due to their increasing occurrence, the scarcity of reports on the topic (particularly for CYN) and the impact of human's health at different levels. Thus, this work performed for the first time the uterotrophic bioassay in rats, following the Organization for Economic Cooperation and Development (OECD) Test Guideline 440, to explore the oestrogenic properties of CYN and MC-LR (75, 150, 300 μg/kg b.w./day) in ovariectomized (OVX) rats. Results revealed neither changes in the wet and blotted uterus weights nor in the morphometric study of uteri. Moreover, among the steroid hormones analysed in serum, the most remarkable effect was the dose-dependent increase in progesterone (P) levels in rats exposed to MC-LR. Additionally, a histopathology study of thyroids and serum levels of thyroids hormones were determined. Tissue affectation (follicular hypertrophy, exfoliated epithelium, hyperplasia) was observed, as well as increased T3 and T4 levels in rats exposed to both toxins. Taken together, these results point out that CYN and MC-LR are not oestrogenic compounds at the conditions tested in the uterotrophic assay in OVX rats, but, however, thyroid disruption effects cannot be discarded.

Immunomodulatory Effects of Cylindrospermopsin in Human T Cells and Monocytes

Cylindrospermopsin (CYN) is a cyanotoxin with an increasing occurrence, and therefore it is important to elucidate its toxicity profile. CYN has been classified as a cytotoxin, although the scientific literature has already revealed that it affects a wide range of organs and systems. However, research on its potential immunotoxicity is still limited. Thus, this study aimed to evaluate the impact of CYN on two human cell lines representative of the immune system: THP-1 (monocytes) and Jurkat (lymphocytes). CYN reduced cell viability, leading to mean effective concentrations (EC50 24 h) of 6.00 ± 1.04 µM and 5.20 ± 1.20 µM for THP-1 and Jurkat cells, respectively, and induced cell death mainly by apoptosis in both experimental models. Moreover, CYN decreased the differentiation of monocytes to macrophages after 48 h of exposure. In addition, an up-regulation of the mRNA expression of different cytokines, such as interleukin (IL) 2, IL-8, tumor necrosis factor-alpha (TNF-α) and interferon-gamma (INF-γ), was also observed mainly after 24 h exposure in both cell lines. However, only an increase in TNF-α in THP-1 supernatants was observed by ELISA. Overall, these results suggest the immunomodulatory activity of CYN in vitro. Therefore, further research is required to evaluate the impact of CYN on the human immune system.

Effect of cold food storage techniques on the contents of Microcystins and Cylindrospermopsin in leaves of spinach (Spinacia oleracea) and lettuce (Lactuca sativa)

The presence of Cylindrospermopsin (CYN) and Microcystins (MCs) in vegetables is considered as a significant worldwide toxicological risk. Thus, this work aims to assess for the first time the impact of refrigeration (4 °C) and freezing (-20 °C) on the levels of CYN, MCs and their mixtures (CYN + MCs) in lettuce and spinach. Samples were spiked with 750 μg cyanotoxins/g dry weight (d.w.). Several storage conditions were studied: refrigeration after 24, 48 h and 7 days, and freezing for 7 days, 1 and 3 months. Cyanotoxin concentrations were determined by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). For CYN, refrigeration at 48 h and 7 days was effective to decrease its concentrations up to 26% and 32%, respectively, in spinach. For MCs, refrigeration was only effective in lettuce compared to spinach, showing an important decrease of 80.3% MC-LR and 85.1% MC-YR. In spinach, CYN was stable after 3 months freezing, whereas MC contents were still reduced up to 44%. Overall, cyanotoxins were less stable in the mixture compared to individual toxins for both processes, and the effect of these storage techniques were toxin and food-specific. Further studies of cyanotoxins in foods are required for evaluating the risk for humans.

A Novel Freshwater Cyanophage Mae-Yong1326-1 Infecting Bloom-Forming Cyanobacterium Microcystis aeruginosa

Microcystis aeruginosa is a major harmful cyanobacterium causing water bloom worldwide. Cyanophage has been proposed as a promising tool for cyanobacterial bloom. In this study, M. aeruginosa FACHB-1326 was used as an indicator host to isolate cyanophage from Lake Taihu. The isolated Microcystis cyanophage Mae-Yong1326-1 has an elliptical head of about 47 nm in diameter and a slender flexible tail of about 340 nm in length. Mae-Yong1326-1 could lyse cyanobacterial strains across three orders (Chroococcales, Nostocales, and Oscillatoriales) in the host range experiments. Mae-Yong1326-1 was stable in stability tests, maintaining high titers at 0–40 °C and at a wide pH range of 3–12. Mae-Yong 1326-1 has a burst size of 329 PFU/cell, which is much larger than the reported Microcystis cyanophages so far. The complete genome of Mae-Yong1326-1 is a double-stranded DNA of 48, 822 bp, with a G + C content of 71.80% and long direct terminal repeats (DTR) of 366 bp, containing 57 predicted ORFs. No Mae-Yong1326-1 ORF was found to be associated with virulence factor or antibiotic resistance. PASC scanning illustrated that the highest nucleotide sequence similarity between Mae-Yong1326-1 and all known phages in databases was only 17.75%, less than 70% (the threshold to define a genus), which indicates that Mae-Yong1326-1 belongs to an unknown new genus. In the proteomic tree based on genome-wide sequence similarities, Mae-Yong1326-1 distantly clusters with three unclassified Microcystis cyanophages (MinS1, Mwe-Yong1112-1, and Mwes-Yong2). These four Microcystis cyanophages form a monophyletic clade, which separates at a node from the other clade formed by two independent families (Zierdtviridae and Orlajensenviridae) of Caudoviricetes class. We propose to establish a new family to harbor the Microcystis cyanophages Mae-Yong1326-1, MinS1, Mwe-Yong1112-1, and Mwes-Yong2. This study enriched the understanding of freshwater cyanophages.