What is driving the NF-κB response in environmental water extracts?

Abstract

In vitro bioassays are increasingly applied for water quality monitoring, with assays indicative of adaptive stress responses commonly included in test batteries. The NF-κB assay is responsive to surface water and wastewater extracts, but the causative compounds are unknown and micropollutants typically found in water do not activate the NF-κB assay. The current study aimed to investigate if co-extracted organic matter and/or endotoxins could cause the NF-κB response in surface water extracts. The effect of model bacterial lipopolysaccharides (LPS) and dissolved organic carbon (DOC) was evaluated in the NF-κB assay both before and after solid-phase extraction (SPE), with 7% effect recovery for LPS and between 7 and 52% effect recovery for DOC observed. The NF-κB response, endotoxin activity, micropollutant concentration and total organic carbon concentration was measured in four surface water extracts. All water extracts showed a response in the NF-κB assay, but the detected micropollutants could not explain the effect. Comparison of predicted bioanalytical equivalent concentrations based on micropollutant, DOC and endotoxin concentrations in surface water with experimental bioanalytical equivalent concentrations suggest that co-extracted endotoxins are the most important drivers of the observed effect, with DOC only having a minor contribution. While in vitro bioassays typically detect mixtures of organic micropollutants, the current study shows that the NF-κB assay can integrate the effects of co-extracted endotoxins. Given that endotoxins can pose a risk for human health, the NF-κB assay is a valuable inclusion in bioanalytical test batteries used for water quality monitoring.

Bioanalytical Tools in Water Quality Assessment

“…Although effects are often observed at low enrichment factors in NF-κB GeneBLAzer, the assay may not be suitable to evaluate the effects of micropollutants. Endotoxins activate NF-κB and a recent study showed that co-extracted endotoxins likely explained most of the effects in surface water extracts in the NF-κB GeneBLAzer assay (Neale et al, 2018b).…”

In vitro bioanalytical evaluation of removal efficiency for bioactive chemicals in Swedish wastewater treatment plants

“…In that study, Neale et al . 37 also report that the majority of the observed NFĸB effect in four Australian environmental water samples was caused by endotoxins and not environmental pollutants.…”

“…NFĸB activity in water samples can be caused by either environmental pollutants or by the presence of endotoxins in the water. It has recently been demonstrated that bacterial lipopolysaccharides (LPS), and potentially other endotoxins, can be co-extracted from the water to the extract when using solid phase extraction methods 37 . In that study, Neale et al .…”

Thioredoxin relieves lipopolysaccharide‑induced acute kidney injury in mice by reducing inflammation, oxidative stress and apoptosis

“…Inflammatory bowel disease, glomerulonephritis and septic shock have been identified as inflammatory diseases closely associated with NF-κB (31). Studies have shown that NF-κB can be activated by endotoxin to enter the nucleus and regulate the gene expression of various inflammatory mediators, particularly the increase of TNF-α and IL-1β, which further acts on macrophages and other inflammatory mediators and cytokines (32,33). These cytokines further activate NF-κB, thus forming a positive feedback cascade amplification effect, producing an excessive inflammatory response and causing extensive tissue and cell injury (33).…”