Cyanotoxins at low doses induce apoptosis and inflammatory effects in murine brain cells: Potential implications for neurodegenerative diseases

Abstract

Cyanotoxins have been shown to be highly toxic for mammalian cells, including brain cells. However, little is known about their effect on inflammatory pathways. This study investigated whether mammalian brain and immune cells can be a target of certain cyanotoxins, at doses approximating those in the guideline levels for drinking water, either alone or in mixtures. We examined the effects on cellular viability, apoptosis and inflammation signalling of several toxins on murine macrophage-like RAW264.7, microglial BV-2 and neuroblastoma N2a cell lines. We tested cylindrospermopsin (CYN), microcystin-LR (MC-LR), and anatoxin-a (ATX-a), individually as well as their mixture. In addition, we studied the neurotoxins β-N-methylamino-l-alanine (BMAA) and its isomer 2,4-diaminobutyric acid (DAB), as well as the mixture of both. Cellular viability was determined by the MTT assay. Apoptosis induction was assessed by measuring the activation of caspases 3/7. Cell death and inflammation are the hallmarks of neurodegenerative diseases. Thus, our final step was to quantify the expression of a major proinflammatory cytokine TNF-α by ELISA. Our results show that CYN, MC-LR and ATX-a, but not BMAA and DAB, at low doses, especially when present in a mixture at threefold less concentrations than individual compounds are 3–15 times more potent at inducing apoptosis and inflammation. Our results suggest that common cyanotoxins at low doses have a potential to induce inflammation and apoptosis in immune and brain cells. Further research of the neuroinflammatory effects of these compounds in vivo is needed to improve safety limit levels for cyanotoxins in drinking water and food.

Neurotoxic Anatoxin-a Can Also Exert Immunotoxicity by the Induction of Apoptosis on Carassius auratus Lymphocytes in vitro When Exposed to Environmentally Relevant Concentrations

“…Data represent the mean ± SD, and a significant difference from the control was determined as **p < 0.01. FIGURE 10 | The intracellular GPx activity in carp immunocytes was determined after cells were treated with ANTX-a (0.01, 0.1, 1, and 10 mg/L) for 12 h. Data represent the mean ± SD, and a significant difference from the control was determined as **p < 0.01. functional tissues of animals involve lymphocytes, such as low-dose ANTX-a-induced inflammation and apoptosis of immune cells and mouse brain cells (Takser et al, 2016). Although ANTX-a shows widespread occurrence and is highly toxic to animals, little is known about its mechanism of action and biotransformation in vertebrates, especially its toxic mechanisms underlying its impact on the fish immune system.…”

Microcystin-LR Does Not Alter Cell Survival and Intracellular Signaling in Human Bronchial Epithelial Cells

“…To compare with other epithelial cell lines, a decreased viability of rat Sertoli cells was found after 24-h exposure to 8-32 µM MC-LR [61]. Additionally, a time-dependent reduction in survival was observed in a series of murine RAW246.7 macrophage-like, BV-2 immortalized microglial, and N2a neuroblastoma-derived cells exposed to 10 µM MC-LR for 24-72 h [62]. However, 10 µM MC-LR did not decrease the viability of human adult liver stem cells HL1-hT1 [56,63], human hepatocellular carcinoma cells HepG2, human colorectal carcinoma cells Caco-2 or monkey kidney epithelial Vero-E6 line [64][65][66].…”

Microbial BMAA elicits mitochondrial dysfunction, innate immunity activation, and Alzheimer’s disease features in cortical neurons

“…Interestingly, BMAA elicited a pronounced decrease in oxidative phosphorylation, impaired calcium homeostasis, and exacerbated ROS production in cells of the NSC-34 neuronal cell line [ 62 ]. In addition, BMAA also dramatically affected the viability of N2a neuronal cell line, inferred from the drop in the activity of the mitochondrial succinate dehydrogenase (SD) [ 63 ]. The common origin of mitochondria and bacteria may facilitate the direct import of certain bacterial metabolites into mitochondria.…”