Inflammatory activity in river-water samples

Contamination of the urban aquatic environment with chemical and biological substances could have a long-term impact on human health because these substances threaten the integrity of the urban ecosystem and the availability of high-quality water for recreation and consumption. In light of this, the aim of the present study was to assess the potential immunological effects of water sampled at various sites along the River Saale near the city of Halle (in the state of Sachsen-Anhalt, Germany). For the control, Ficoll-separated peripheral blood mononuclear cells (PBMC) of healthy donors were cultured for 24 h in either filter-sterilized river water or drinking-water samples. Cell vitality was assessed using the MTT bioassay. Cytokines in culture supernatants were measured by ELISA. Endotoxin concentrations in the water samples were assessed by the limulus amoebocyte lysate (LAL) test. River water and drinking water showed comparably weak cytotoxic effects on PBMC. Drinking water did not exert any effect on cytokine secretion. In contrast, all river-water samples triggered secretion of proinflammatory cytokines, as shown for TNF-alpha, IL-1beta, and IL-6. Free endotoxin was detected in all river-water samples. However, the highest inflammatory activity regarding induction of all three cytokines, as well as the highest endotoxin content as determined by LAL, was found in a water sample taken immediately downstream of a wastewater treatment plant. Inhibition studies using the monoclonal anti-CD14 antibody biG14, which is known to suppress binding of lipopolysaccharide (LPS) to CD14 via binding CD14 itself, revealed that free endotoxin was indeed the major inducer of proinflammatory cytokines in the river-water samples. Taken together, the results suggest that the microorganism-derived endotoxin is a widely distributed contaminant in the urban aquatic environment that should be considered in routine monitoring and in assessing ecosystem and human health.