Investigation of In Vitro Endocrine Activities of Microcystis and Planktothrix Cyanobacterial Strains

Abstract

Cyanobacteria are cosmopolitan photosynthetic prokaryotes that can form dense accumulations in aquatic environments. They are able to produce many bioactive metabolites, some of which are potentially endocrine disrupting compounds, i.e., compounds that interfere with the hormonal systems of animals and humans. Endocrine disruptors represent potential risks to both environmental and human health, making them a global challenge. The aim of this study was to investigate the potential endocrine disrupting activities with emphasis on estrogenic effects of extracts from cultures of Microcystis or Planktothrix species. We also assessed the possible role of microcystins, some of the most studied cyanobacterial toxins, and thus included both microcystin-producing and non-producing strains. Extracts from 26 cyanobacterial cultures were initially screened in estrogen-, androgen-, and glucocorticoid-responsive reporter-gene assays (RGAs) in order to identify endocrine disruption at the level of nuclear receptor transcriptional activity. Extracts from selected strains were tested repeatedly in the estrogen-responsive RGAs, but the observed estrogen agonist and antagonist activity was minor and similar to that of the cyanobacteria growth medium control. We thus focused on another, non-receptor mediated mechanism of action, and studied the 17β-estradiol (natural estrogen hormone) biotransformation in human liver microsomes in the presence or absence of microcystin-LR (MC-LR), or an extract from the MC-LR producing M. aeruginosa PCC7806 strain. Our results show a modulating effect on the estradiol biotransformation. Thus, while 2-hydroxylation was significantly decreased following co-incubation of 17β-estradiol with MC-LR or M. aeruginosa PCC7806 extract, the relative concentration of estrone was increased.

Understanding the Risks of Diffusion of Cyanobacteria Toxins in Rivers, Lakes, and Potable Water

“…Phytotoxicity diffusion is the process of producing toxic exudates on the cell walls of Planktothrix species due to dense blooms that decompose. Due to the pigments (such as carotenoids) they produce, Planktothrix blooms can also cause water to become discolored [ 43 ]. In addition, Planktothrix is renowned for its capacity to multiply quickly and, under the right circumstances, to create dense aggregates or mats at the water’s surface.…”

Potential Endocrine Disruption of Cyanobacterial Toxins, Microcystins and Cylindrospermopsin: A Review

“…In addition to this study, it is important to highlight that only a few studies have determined the potential endocrine disruption activity of cyanobacterial cells or pure cyanotoxins through interactions with the signaling pathways of the estrogen receptor (ER), androgen receptor (AR), glucocorticoid receptor (GR), and retinoid receptor (RAR) [43,49,51,52]. None of them were performed following the requirements of the OECD guidelines [53][54][55].…”

“…All of these findings highlight the importance of investigating the activity of estrogens, androgens, retinoids, and other bioactive compounds present in cyanobacterial blooms. In contrast, more recently, Mallia et al [52] investigated the in vitro endocrine activities of 26 cyanobacterial cultures of Microcystis or Planktothrix species by screening them in estrogen-, androgen-, and glucocorticoid-responsive reporter gene assay (RGA), and the results were not conclusive.…”

Characterization of microbial communities associated with cyanoalgal bloom in a dam from León, Gto. México by sequencing of variable regions of the rRNA genes16S and 18S

“…Las cianobacterias son procariotes fotosínteticos que al formar floraciones pueden liberar metabolitos bioactivos, conocidos como cianotoxinas, dentro de las más estudiadas se encuentran las microcistinas, potentes hepatotóxinas, producidas generalmente por el género Planktothrix spp. (Catherine et al, 2008;Vasas et al, 2013;Mallia et al, 2020).…”