LogD-based modelling and ΔlogD as a proxy for pH-dependent action of ionizable chemicals reveal the relevance of both neutral and ionic species for fish embryotoxicity and possess great potential for practical application in the regulation of chemicals.

Depending on the ambient pH, ionizable substances are present in varying proportions in their neutral or charged form. The extent to which these two chemical species contribute to the pH-dependant toxicity of ionizable chemicals and whether intracellular ion trapping has a decisive influence in this context is controversially discussed. Against this background, we determined the acute toxicity of 24 ionizable substances at up to 4 different pH values on the embryonic development of the zebrafish, Danio rerio, and supplemented this dataset with additional data from the literature. The LC50 for some substances (diclofenac, propranolol, fluoxetine) differed by a factor of even >103 between pH5 and pH9. To simulate the toxicity of 12 acids and 12 bases, six models to calculate a pH-dependant logD value as a proxy for the uptake of potentially toxic molecules were created based on different premises for the trans-membrane passage and toxic action of neutral and ionic species, and their abilities to explain the real LC50 data set were assessed. Using this approach, we were able to show that both neutral and charged species are almost certainly taken up into cells according to their logD-based distribution, and that both species exert toxicity. Since two of the models that assume all intracellular molecules to be neutral overestimated the real toxicity, it must be concluded, that the toxic effect of a single charged intracellularly present molecule is, on the average, lower than that of a single neutral molecule. Furthermore, it was possible to attribute differences in toxicity at different pH values for these 24 ionizable substances to the respective deltas in logD at these pH levels with high accuracy, enabling particularly a full logD-based model on the basis of logPow as a membrane passage descriptor to be used for predicting potential toxicities in worst-case scenarios from existing experimental studies, as stipulated in the process of registration of chemicals and the definition of Environmental Quality Standards (EQS).

Echinococcus multilocularis specific antibody, systemic cytokine, and chemokine levels, as well as antigen-specific cellular responses in patients with progressive, stable, and cured alveolar echinococcosis: A 10-year follow-up.

BACKGROUND: The infestation with Echinococcus multilocularis larvae may persist in humans for up to decades without evident clinical symptoms. Longitudinal investigations are needed to understand the dynamic immunological processes in alveolar echinococcosis (AE) patients associated with an active and progressive, a stable or a regressive course of disease. METHODOLOGY/PRINCIPAL FINDINGS: This study evaluated the E. multilocularis specific antibody responses, systemic cytokine, and chemokine serum levels over a 10-year follow-up period, as well as cellular responsiveness in AE patients. Our results demonstrate a rapid decrease in antibodies against E. multilocularis specific antigen Em2+. Especially in cured patients, these antibodies remained negative, making them a significant predictor for cured AE. E. multilocularis specific IgG4, and indirect hemagglutination IHA decreased later in time, after around 5 years. While total IgE did not show significant dynamics over the course of disease, E. multilocularis specific IgE decreased after one to two years, and increasing levels were a significant predictor of progressive disease. There was no significant change in systemic IL-8, IL-9, CCL18 or CCL20 serum levels over time. Univariate analysis across groups indicated lower IL-8 levels in cured patients; however, this result could not be confirmed by multivariate analysis. Levels of CCL17 decreased during treatment, especially in cured patients, and thus might serve as a predictive or risk factor for progressive disease. Levels of IL-10 and CCL13 decreased during disease, especially after five and ten years of intervention. The E. multilocularis antigen (EmAg) inducible cellular productions of MCP1(CCL13), TARC(CCL17) and PARC(CCL18) were lowest in patients with cured AE and infection-free controls, while the EmAg inducible cellular production of IFN-γ increased after cure. Significant positive cytokine and chemokine correlations were observed in AE patients for IL-9, IL-10, CCL13(MCP-4), CCL17(TARC) and CCL20(LARC)(for all p<0.001). E. multilocularis specific IgG4 response correlated positively with TARC (p<0.001). Both markers enhanced over time in progressive disease and decreased after cure. The levels of IL-8, IL-10, MCP4 and LARC enhanced with AE regression. CONCLUSIONS/SIGNIFICANCE: Repeated biomarker surveys are advisable to evaluate progression or regression of disease during longitudinal follow-up and such analyses can support imaging techniques and improve staging of AE patients.