Cytotoxicity and Effects on the Synapsis Induced by Pure Cylindrospermopsin in an E17 Embryonic Murine Primary Neuronal Culture in a Concentration- and Time-Dependent Manner

miR-484 in Hippocampal Astrocytes of Aged and Young Rats Targets CSF-1 to Regulate Neural Progenitor/Stem Cell Proliferation and Differentiation Into Neurons

AIM

Aging-related cognitive decline is closely linked to the reduced function of neural progenitor/stem cells (NPSCs), which can be influenced by the neural microenvironment, particularly astrocytes. The aim of this study was to explore how astrocytes affect NPSCs and cognitive function during aging.

METHODS

H2O2-treated astrocytes were used to mimic the aging phenotype of astrocytes. Proteomic analysis identified altered protein expression, revealing high levels of colony-stimulating factor-1 (CSF-1) in the supernatant of H2O2-treated astrocytes. Primary NPSCs were isolated and cultured in vitro, then stimulated with varying concentrations of recombinant CSF-1 protein to assess its effects on NPSC proliferation, differentiation, and apoptosis. Transcriptome sequencing identified miR-484 related to CSF-1 in H2O2-treated astrocytes, and a dual-luciferase assay verified the interaction between miR-484 and CSF-1. The impact of miR-484 overexpression on NPSC function and cognitive restoration was evaluated both in vitro and in vivo (in 20-month-old rats).

RESULTS

High concentration of CSF-1 inhibited the NPSC proliferation and differentiation into neurons while inducing apoptosis. Overexpression of miR-484 downregulated CSF-1 expression by binding to its 3' untranslated region, thereby promoting the NPSC proliferation and differentiation into neurons. In 20-month-old rats, miR-484 overexpression improved spatial learning and memory in the Morris water maze, increased NPSC proliferation, and reduced apoptosis.

CONCLUSION

Our findings reveal that miR-484 regulates CSF-1 to influence NPSC proliferation, differentiation into neurons, and apoptosis, consequently improving cognitive function in 20-month-old rats. This study provides a foundation for developing therapeutic strategies targeting age-related hippocampal cognitive impairments.

Alterations in acetylcholinesterase activity and oxidative stress parameters induced by pure cylindrospermopsin in brain of orally exposed rats and determination of potential metabolites

Cylindrospermopsin (CYN) is a secondary metabolite produced by cyanobacteria. In view of its toxic effects, CYN is frequently classified as a cytotoxin, although it has been associated with neurotoxicological effects. Despite this, few studies have explored the impact of CYN on the nervous system and none of them have been conducted in mammals. Therefore, the objective of the present work was to evaluate the effect of different doses of pure CYN (7.5-75.0 µg/kg body weight) on the brain of rats after gavage exposure for 48 h. For this purpose, the activity of acetylcholinesterase (AChE) enzyme and different biomarkers of oxidative stress were assessed. A significant inhibition of AChE activity was observed at all doses tested. Additionally, the results showed a dose-dependent increase in lipid peroxidation (LPO) levels, as well as alterations in superoxide dismutase (SOD) and catalase (CAT) activities. These changes could be produced by CYN metabolites detected in brain samples by ultra-high-performance liquid chromatography coupled to a tandem mass spectrometry system (UHPLC-MS/MS). These findings suggest that metabolites of pure CYN could cause alterations in the brain of rats after oral exposure and highlight the need for further studies focusing on CYN's neurotoxicity and its potential role in neurodegenerative diseases.

Effects of cylindrospermopsin, chlorpyrifos and their combination in a SH-SY5Y cell model concerning developmental neurotoxicity

The cyanotoxin cylindrospermopsin (CYN) has been postulated to cause neurotoxicity, although the studies in this concern are very few. In addition, some studies in vitro indicate its possible effects on development. Furthermore, pesticides can be present in the same environmental samples as cyanotoxins. Therefore, chlorpyrifos (CPF) has been one of the most common pesticides used worldwide. The aim of this report was to study the effects of CYN, isolated and in combination with CPF, in a developmental neurotoxicity in vitro model. The human neuroblastoma SH-SY5Y cell line was exposed during 6 days of differentiation to both toxics to study their effects on cell viability and neurite outgrowth. To further evaluate effects of both toxicants on cholinergic signaling, their agonistic and antagonistic activities on the α7 homomeric nicotinic acetylcholine receptor (nAChR) were studied upon acute exposure. Moreover, a transcriptomic analysis by qPCR was performed after 6 days of CYN-exposure during differentiation. The results showed a concentration-dependent decrease on both cell viability and neurite outgrowth for both toxics isolated, leading to effective concentration 20 (EC20) values of 0.35 µM and 0.097 µM for CYN on cell viability and neurite outgrowth, respectively, and 100 µM and 58 µM for CPF, while the combination demonstrated no significant variations. In addition, 95 µM and 285 µM CPF demonstrated to act as an antagonist to nicotine on the nAChR, although CYN up to 2.4 µM had no effect on the efficacy of these receptors. Additionally, the EC20 for CYN (0.097 µM) on neurite outgrowth downregulated expression of the 5 genes NTNG2 (netrin G2), KCNJ11 (potassium channel), SLC18A3 (vesicular acetylcholine transporter), APOE (apolipoprotein E), and SEMA6B (semaphorin 6B), that are all important for neuronal development. Thus, this study points out the importance of studying the effects of CYN in terms of neurotoxicity and developmental neurotoxicity.

Cytotoxic Effects and Oxidative Stress Produced by a Cyanobacterial Cylindrospermopsin Producer Extract versus a Cylindrospermopsin Non-Producing Extract on the Neuroblastoma SH-SY5Y Cell Line

The incidence and interest of cyanobacteria are increasing nowadays because they are able to produce some toxic secondary metabolites known as cyanotoxins. Among them, the presence of cylindrospermopsin (CYN) is especially relevant, as it seems to cause damage at different levels in the organisms: the nervous system being the one most recently reported. Usually, the effects of the cyanotoxins are studied, but not those exerted by cyanobacterial biomass. The aim of the present study was to assess the cytotoxicity and oxidative stress generation of one cyanobacterial extract of R. raciborskii non-containing CYN (CYN-), and compare its effects with those exerted by a cyanobacterial extract of C. ovalisporum containing CYN (CYN+) in the human neuroblastoma SH-SY5Y cell line. Moreover, the analytical characterization of potential cyanotoxins and their metabolites that are present in both extracts of these cultures was also carried out using Ultrahigh Performance Liquid Chromatography-Mass Spectrometry, in tandem (UHPLC-MS/MS). The results show a reduction of cell viability concentration- and time-dependently after 24 and 48 h of exposure with CYN+ being five times more toxic than CYN-. Furthermore, the reactive oxygen species (ROS) increased with time (0-24 h) and CYN concentration (0-1.11 µg/mL). However, this rise was only obtained after the highest concentrations and times of exposure to CYN-, while this extract also caused a decrease in reduced glutathione (GSH) levels, which might be an indication of the compensation of the oxidative stress response. This study is the first one performed in vitro comparing the effects of CYN+ and CYN-, which highlights the importance of studying toxic features in their natural scenario.

Toxic effects of the cylindrospermopsin and chlorpyrifos combination on the differentiated SH-SY5Y human neuroblastoma cell line

Due to climate change and anthropogenic activities, the levels of pollution of aquatic and terrestrial environments have increased in the last decades. In this sense, the rise of cyanobacterial blooms, which release secondary metabolites with toxic properties, and the global use of pesticides for agricultural purposes have a negative impact on ecosystems. Thus, it would be interesting to study the concomitance of both types of toxicants in the same sample, since it is possible that they appear together. The aim of the present work was to state the effects of the interaction between the cyanotoxin cylindrospermopsin and the pesticide chlorpyrifos in differentiated SH-SY5Y neuronal cells to assess how they could affect the nervous system. To this end, cytotoxicity, morphological, and acetylcholinesterase activity studies were performed during 24 and 48 h. The results revealed a concentration-dependent decrease in viability and interaction between both toxicants, together with clear signs of apoptosis and necrosis induction. In this sense, different stages on the differentiation process would lead to differences in the toxicity exerted by the compounds both isolated as in combination, which it is not observed in non-differentiated cells. Additionally, the acetylcholinesterase activity appeared not to be affected, which is a clear difference compared to non-differentiated cells. These results show the importance of studying not only the toxicants themselves, but also in combination, to assess their possible effects in a more realistic scenario.

Recent Advances in Aptasensing Strategies for Monitoring Phycotoxins: Promising for Food Safety

Phycotoxins or marine toxins cause massive harm to humans, livestock, and pets. Current strategies based on ordinary methods are long time-wise and require expert operators, and are not reliable for on-site and real-time use. Therefore, it is urgent to exploit new detection methods for marine toxins with high sensitivity and specificity, low detection limits, convenience, and high efficiency. Conversely, biosensors can distinguish poisons with less response time and higher selectivity than the common strategies. Aptamer-based biosensors (aptasensors) are potent for environmental monitoring, especially for on-site and real-time determination of marine toxins and freshwater microorganisms, and with a degree of superiority over other biosensors, making them worth considering. This article reviews the designed aptasensors based on the different strategies for detecting the various phycotoxins.