1. Investigation of microcystin conformation and binding towards PPP1 by molecular dynamics simulation
Sabrina Jaeger-Honz, Jahn Nitschke, Stefan Altaner, Karsten Klein, Daniel R Dietrich, Falk Schreiber Chem Biol Interact. 2022 Jan 5;351:109766. doi: 10.1016/j.cbi.2021.109766. Epub 2021 Nov 30.
Microcystins (MC) are a group of structurally similar cyanotoxins with currently 279 described structural variants. Human exposure is frequent by consumption of contaminated water, food or food supplements. MC can result in serious intoxications, commensurate with ensuing pathology in various organs or in rare cases even mortality. The current WHO risk assessment primarily considers MC-LR, while all other structural variants are treated as equivalent to MC-LR, despite that current data strongly suggest that MC-LR is not the most toxic MC, and toxicity can be very different for MC congeners. To investigate and analyse binding and conformation of different MC congeners, we applied for the first time Molecular Dynamics (MD) simulation to four MC congeners (MC-LR, MC-LF, [Enantio-Adda5]MC-LF, [β-D-Asp3,Dhb7]MC-RR). We could show that ser/thr protein phosphatase 1 is stable in all MD simulations and that MC-LR backbone adopts to a second conformation in solvent MD simulation, which was previously unknown. We could also show that MC congeners can adopt to different backbone conformation when simulated in solvent or in complex with ser/thr protein phosphatase 1 and differ in their binding behaviour. Our findings suggest that MD Simulation of different MC congeners aid in understanding structural differences and binding of this group of structurally similar cyanotoxins.
2. Multi-class secondary metabolites in cyanobacterial blooms from a tropical water body: Distribution patterns and real-time prediction
Luhua You, Xuneng Tong, Shu Harn Te, Ngoc Han Tran, Nur Hanisah Bte Sukarji, Yiliang He, Karina Yew-Hoong Gin Water Res. 2022 Apr 1;212:118129. doi: 10.1016/j.watres.2022.118129. Epub 2022 Jan 29.
Cyanobacterial blooms that produce toxins occur in freshwaters worldwide and yet, the occurrence and distribution patterns of many cyanobacterial secondary metabolites particularly in tropical regions are still not fully understood. Moreover, predictive models for these metabolites by using easily accessible water quality indicators are rarely discussed. In this study, we investigated the co-occurrence and spatiotemporal trends of 18 well-known and less-studied cyanobacterial metabolites (including [D-Asp3] microcystin-LR (DM-LR), [D-Asp3] microcystin-RR (DM-RR), microcystin-HilR (MC-HilR), microcystin-HtyR (MC-HtyR), microcystin-LA (MC-LA), microcystin-LF (MC-LF), microcystin-LR (MC-LR), microcystin-LW (MC-LW), microcystin-LY (MC-LY), microcystin-RR (MC-RR) and microcystin-WR (MC-WR), Anatoxin-a (ATX-a), homoanatoxin-a (HATX-a), cylindrospermospin (CYN), nodularin (NOD), anabaenopeptin A (AptA) and anabaenopeptin B (AptB)) in a tropical freshwater lake often plagued with blooms. Random forest (RF) models were developed to predict MCs and CYN and assess the relative importance of 22 potential predictors that determined their concentrations. The results showed that 11 MCs, CYN, ATX-a, HATX-a, AptA and AptB were found at least once in the studied water body, with MC-RR and CYN being the most frequently occurring, intracellularly and extracellularly. AptA and AptB were detected for the first time in tropical freshwaters at low concentrations. The metabolite profiles were highly variable at both temporal and spatial scales, in line with spatially different phytoplankton assemblages. Notably, MCs decreased with the increase of CYN, possibly revealing interspecific competition of cyanobacteria. The rapid RF prediction models for MCs and CYN were successfully developed using 4 identified drivers (i.e., chlorophyll-a, total carbon, rainfall and ammonium for MCs prediction; and chloride, total carbon, rainfall and nitrate for CYN prediction). The established models can help to better understand the potential relationships between cyanotoxins and environmental variables as well as provide useful information for making policy decisions.
3. Microcystins activate nuclear factor erythroid 2-related factor 2 (Nrf2) in human liver cells in vitro - Implications for an oxidative stress induction by microcystins
Johan Lundqvist, Heidi Pekar, Agneta Oskarsson Toxicon. 2017 Feb;126:47-50. doi: 10.1016/j.toxicon.2016.12.012. Epub 2016 Dec 23.
Microcystins, a potential threat to drinking water quality, are hepatotoxic but it has remained unclear if microcystins induce oxidative stress. We investigated if four microcystins could activate the Nrf2 pathway, a regulator of oxidative stress response. Nrf2 activity was significantly increased by microcystin-LR and -RR at 10 μM, by microcystin-LY at 3 μM, by [D-Asp3]-LR and by microcystin-LR at 1 μM. Our results lend support to the suggestion that microcystins may induce oxidative stress response.