Immunomodulatory effects of selected cyanobacterial peptides in vitro
Introduction
Cyanobacteria are photosynthetic organism frequently found in the aquatic environment. Due to their potency to produce biologically active secondary metabolites, their massive growth became one of the serious environmental and health problems worldwide. Globally, cyanobacterial dominance in freshwater habitat is increasing and it is expected that a warming climate will exacerbate the frequency and duration of such blooms (Paerl and Huisman, 2009). The communities of the people living the areas with high cyanobacterial densities may be long term exposed to cyanobacterial toxins via poorly treated or untreated water and consumption of contaminated food such as fish and mussels (Chen and Xie, 2007, Henry, 2014, Poste et al., 2011). Cyanobacteria produce many biologically active peptides that are classified into families according to their structural features and include cyclic microcystins (MCs) and linear aeruginosins (Aer) (Welker and von Dohren, 2006). MCs gained public and scientific attention over last three decades due to their common presence in the environment, high concentrations and toxicity (Rastogi et al., 2014). Recent studies documented presence of MCs in blood of people living near contaminated localities (Chen et al., 2009, Li et al., 2011). MC family contains more than hundred structurally similar congeners in which MC-LR, -RR and -YR are the most produced peptides and represent toxins of concern (Carmichael and Boyer, 2016). The hepatotoxic and tumor-promotional potency of MCs has been investigated extensively in the past but other potential chronic impacts of MCs, e.g. on immune system, have been studied to a much lesser extent. The imbalanced immune system is a cause of many inflammatory diseases, hyperactivity and autoimmune reactions and it was also shown to contribute to cancer development (Didonato et al., 2012). Our recent study (Adamovsky et al., 2015) revealed a high potency of MC-LR to stimulate the innate immunity cells macrophages in vitro and suggested the possible mechanism of action. The non-physiological modulation of macrophages functions plays an important role in chronic inflammation. In contrast to acute inflammation, which is usually suppressed after removal of pathogens, long-term activation of macrophages may contribute to diverse local and systemic deleterious effects on cells and tissues. Although MC-LR is the most commonly occurring MC variant, the study of Chen et al. (2009) indicated that other MC variants (-RR and -YR) could have cumulative serum levels higher than the level of MC-LR (Chen et al., 2009). However, no information is currently available on immunomodulatory effects of other variants of MCs.
In addition to MCs, other cyanobacterial peptides become of general interest. For example, Aer-865 has been an attractive research topic because of its potential anti-inflammatory activity together with the inhibitory activity against trypsin-like serine proteases (Ersmark et al., 2008, Kapuścik et al., 2013). Although the anti-inflammatory potency of Aer-865 has been evaluated on human lung microvascular endothelial cells _3rdcrjn (Kapuścik et al., 2013), the interaction of this cyanobacterial peptide with the immune cells has not been studied so far.
The present study aimed to investigate and compare the in vitro effects of two abundant MC variants and Aer-865 (Table 1) on macrophages, which represent one of the key effector cells within the innate immune responses. Specifically, our study includes macrophage activation associated with production of cytotoxic and cytostatic products such as nitric oxide (NO), as well as pro-inflammatory mediators (e.g. tumor necrosis factor α, TNFα and interleukin 6, IL-6). Murine macrophage RAW 264.7 cells have been selected because of broad utilization of this immune model in a range of pharmacological (Tweedie et al., 2009) as well as environmental toxicological studies (Jalava et al., 2007).
Section snippets
Reagents and cell culture
MC-RR and MC-YR was obtained from Enzo Life Sciences, New York with purity ≥95% (HPLC). The stock solution (1 mg/ml) was dissolved in methanol (50%). Aer-865 (MW = 865) was isolated from the cyanobacterial strain Nostoc sp. Lukešová 30/93 and purified in the Institute of Microbiology, Třeboň, Czech Republic (Kapuścik et al., 2013). Sterile phosphate-buffered saline (PBS) was used for preparation of testing concentration. Lyophilized powder of lipopolysaccharide (LPS) from Escherichia coli
Results and discussion
Concentration of tested MCs (MC-RR and MC-YR) were selected in order to describe the effects of MCs in the levels that were detected in sera of individuals living on a lake with high cyanobacterial density (Chen et al., 2009, Li et al., 2011), i.e. adult fishermen (min.-max. 0.045–1.83 nM) and their children (0.4–1.3 nM MC-LR eq.).
All tested substances were initially tested on cell viability with and without co-exposures to a model activator LPS (Fig. 1). In agreement with previous studies (
Acknowledgment
The research was supported by the grant from the Czech National Science Foundation GAČR GP13-27695P. Infrastructure of the RECETOX Centre is supported by the Czech Ministry of Education, Youth and Sports projects No. LO1214 and LM2015051.
References (26)
- et al.
Health impacts from cyanobacteria harmful algae blooms : implications for the North American Great lakes
Harmful Algae
(2016) - et al.
First identification of the hepatotoxic microcystins in the serum of a chronically exposed human population together with indication of hepatocellular damage
Toxicol. Sci.
(2009) - et al.
The role of organic anion transporting polypeptides (OATPs/SLCOs) in the toxicity of different microcystin congeners in vitro: a comparison of primary human hepatocytes and OATP-transfected HEK293 cells
Toxicol. Appl. Pharmacol.
(2010) - et al.
Organic anion transporting polypeptides expressed in liver and brain mediate uptake of microcystin
Toxicol. Appl. Pharmacol.
(2005) - et al.
Pitfalls in microcystin extraction and recovery from human blood serum
Chem. Biol. Interact.
(2014) - et al.
Acute and subacute toxic effects produced by microcystin-YR on the fish cell lines RTG-2 and PLHC-1
Toxicol. Vitr.
(2007) - et al.
The use of the fish cell lines RTG-2 and PLHC-1 to compare the toxic effects produced by microcystins LR and RR
Toxicol. Vitr.
(2005) - et al.
Comparison of the toxicity induced by microcystin-RR and microcystin-YR in differentiated and undifferentiated Caco-2 cells
Toxicon
(2009) - et al.
A cellular model of inflammation for identifying TNF-alpha synthesis inhibitors
J. Neurosci. Methods
(2009) - et al.
Immunomodulatory potency of microcystin, an important water-polluting cyanobacterial toxin
Environ. Sci. Technol.
(2015)
Toll-like receptors: function and roles in lung disease
Am. J. Physiol. Lung Cell Mol. Physiol.
Microcystin accumulation in freshwater bivalves from Lake Taihu, China, and the potential risk to human consumption
Environ. Toxicol. Chem.
NF-κB and the link between inflammation and cancer
Immunol. Rev.
Cited by (8)
Neither microcystin, nor nodularin, nor cylindrospermopsin directly interact with human toll-like receptors
2021, ChemosphereCitation Excerpt :Additionally, episodes of human poisonings have been recorded after short-term exposure (Azevedo et al., 2002; Teixeira et al., 1993), but the effects of chronic exposure to cyanotoxins specifically on a key aspect of health, the immune system, remains largely unexplored. Recent pilot studies revealed that MC-LR and CYN have the potential to affect innate immune responses and suggested that these toxins may interact with Toll-like receptors (TLRs); key triggers of inflammatory processes (Adamovsky et al., 2015; Moosova et al, 2018, 2019). TLRs are pathogen recognition receptors expressed on the cell surface or within endosomes of innate immune cells.
Immunomodulatory effects of cyanobacterial toxin cylindrospermopsin on innate immune cells
2019, ChemosphereCitation Excerpt :Based on apparent risk to human health and suspected genotoxicity, a provisional guideline value for CYN in drinking water was set at 1 μg/L (Australia, New Zealand), 15 μg/L (Brazil) or 0.7–3 μg/L (USA) (US EPA, 2015b). Importantly, there is a growing evidence, that besides the above-mentioned toxicity, exposure to cyanotoxins (including CYN) may also induce deregulation and chronic activation of immune system (Adamovsky et al., 2015; Chen et al., 2013; Gao et al., 2017; Juhas et al., 2015; Moosova et al., 2018; Poniedziałek et al., 2012, 2014; Sieroslawska and Rymuszka, 2015a). Since contaminated foods and water represent one the most important route of exposure for cyanotoxins, intestine represents an important part of the organism where cyanotoxins enter the tissues/blood and may affect the immune cell functions.
Cyanobacterial peptides as a tour de force in the chemical space of antiparasitic agents
2019, Archives of Biochemistry and BiophysicsCitation Excerpt :In addition, the dual role of the macrophage as mastermind for the organization of the immune response against Leishmania, as well as the executioner of the leishmanicidal mechanisms, is missed. The effects of other Cy-AMPs on the macrophage functionality have been described [139–142], but none of them were assayed for their outcome on the leishmanicidal activity. Other example is the inhibition of human cathepsin L by symplostatin 4 (gallinamide A) with an IC50 at the nanomolar range [143].
Microbiome Composition and Function in Aquatic Vertebrates: Small Organisms Making Big Impacts on Aquatic Animal Health
2021, Frontiers in Microbiology