Cyanobacterial bloom-associated lipopolysaccharides induce pro-inflammatory processes in keratinocytes in vitro.

Our previous studies have shown that CyanoHAB LPS (lipopolysaccharides) and LPS from cyanobacterial cultures induce pro-inflammatory effects on intestinal epithelial and immune cells in vitro. To expand our understanding, we investigated their impact on human keratinocytes, which are targeted during water recreational activities. LPS samples were isolated from CyanoHAB biomasses dominated by Microcystis, Aphanizomenon, Planktothrix, and Dolichospermum, or from axenic cultures of these genera. We identified two CyanoHAB biomasses containing a high proportion of Gram-negative bacteria, including potentially pathogenic genera. These biomasses showed the highest induction of interleukin (IL) 8, IL-6, C-C motif chemokine ligand (CCL) 2 (also known as MCP-1), and CCL20 production by HaCaT cells. Interestingly, all CyanoHAB-derived LPS and LPS from axenic cultures (except for Microcystis) accelerated cell proliferation and migration. Our findings highlight the role of G- bacteria composition and LPS structural disparities in influencing these effects, with implications for skin health during recreational activities.

Cyanobacterial harmful bloom lipopolysaccharides: pro-inflammatory effects on epithelial and immune cells in vitro.

Cyanobacterial harmful blooms (CyanoHABs) pose a global ecological problem, and their lipopolysaccharides (LPS) are among the bioactive compounds they release. Previous studies on CyanoHAB-LPS from single cyanobacterial species have shown varying bioactivities in different in vitro cell models. In this study, we isolated LPS from 19 CyanoHAB samples collected at 18 water bodies in the Czech Republic over two consecutive seasons. The proportions of cyanobacteria, Gram-negative bacteria (G-), and other bacteria in the biomass were determined by qPCR, while the cyanobacterial genera were identified using light microscopy. In vitro models of keratinocytes (HaCaT), the intestinal epithelium (co-culture of differentiated Caco-2 cells and peripheral blood mononuclear cells - PBMC), and PBMC alone were treated with isolated LPS at concentrations of 50, 100, and 1 µg/ml, respectively. The endotoxin activities of these concentrations were within the range measured in the aquatic environment. Approximately 85-90% of the samples displayed biological activity. However, the potency of individual LPS effects and response patterns varied across the different in vitro models. Furthermore, the observed activities did not exhibit a clear correlation with the taxonomic composition of the phytoplankton community, the relative share of microbial groups in the biomass, endotoxin activity of the LPS, or LPS migration and staining pattern in SDS-PAGE. These findings suggest that the effects of CyanoHAB-LPS depend on the specific composition and abundance of various LPS structures within the complex environmental sample and their interactions with cellular receptors.

Effects of clofibric acid alone and in combination with 17ß-estradiol on mRNA abundance in primary hepatocytes isolated from rainbow trout.

Clofibric acid (CA) is the active substance of lipid lowering drugs. It is resistant to degradation, polar in nature, and has been found ubiquitously in the aquatic environment. Though CA is classified as a peroxisomal proliferator in rodents and is considered as a potential endocrine disruptor, little information exists on the effects of CA in aquatic organisms, such as fish. In the present study, we examined the mRNA levels of peroxisome proliferator- and estrogen-sensitive genes on the exposure of primary rainbow trout (Oncorhynchus mykiss) hepatocytes to CA alone and in combination with the natural female sex hormone, 17ß-estradiol (E2). Our results demonstrate that rainbow trout hepatocytes are relatively refractory to the effects of CA on the PPAR signaling pathway and lipid metabolism. Moreover, CA did not show recognizable estrogenic activity, but after the induction of vitellogenesis by E2, CA significantly reduced vitellogenin (VTG) mRNA abundance. Apparently, the indirect repression of VTG transcription, independent of estrogen receptors, occurred. The mechanism is not yet clearly understood but may involve disruption of the stabilization of VTG mRNA known to be induced by E2.

Postnatal development of the serotonin signaling system in the mucosa of the guinea pig ileum.

BACKGROUND: Serotonin is an important neurohumoral molecule in the gut but its signaling system is not fully developed in the neonatal gastrointestinal (GI) tract. This study aimed to evaluate the postnatal maturation of serotonin signaling in the small intestine. METHODS: In vitro amperometry for real-time measurement of serotonin at the mucosal surface, immunoblot, immunohistochemistry and high-performance liquid chromatography (HPLC) were used to examine serotonin handling in ileal segments from guinea pigs of different ages. KEY RESULTS: Extracellular serotonin levels significantly declined over the first three postnatal weeks, after which the levels increased and reached their maximum at 9 weeks postnatally. Serotonin levels were insensitive to the inhibition of the serotonin transporter (SERT) until the animals reached 3 weeks old. Measurement of serotonin and its metabolite 5-hydroxyindole acetic acid (5-HIAA) in the mucosa revealed that the serotonin turnover was significantly lower in neonates. Immunoblot and immunohistochemistry showed that SERT expression was extremely low in the neonatal period. Serotonin staining in cross-section showed that enterochromaffin (EC) cells were preferentially localized in the crypt region in neonates and the number of EC cells was significantly higher in 9-week-old animals. CONCLUSIONS & INFERENCES: SERT expression is low in the neonatal intestine and serotonin signaling matures postnatally. Extracellular serotonin levels decrease during the first three neonatal weeks as SERT expression increases. Extracellular serotonin levels increase after 3 weeks (weaning) possibly due to an increase in EC cell numbers. Postnatal maturation of serotonin signaling coincides with dietary changes in the developing guinea pig.