Biology subjects

Hollert, H.

Publications and source records attributed to Hollert, H..

10 recordsLinked to original sources

bioRxiv2025

Assessing the impact of carrier solvent and solid phase extraction blank toxicity on fish embryo testing

Bioassays are powerful tools to comprehensively understand the effects of complex environmental mixtures on humans and other animal species. In particular, the fish embryo test (FET) with zebrafish (Danio rerio) is one of the most used bioanalytical tools to test in vivo the effect of environmental extract. However, it is well known that the preparation technique of complex environmental samples for bioanalytical testing could have huge impact on the composition of exposure solutions and hence the corresponding toxicity Considering this, it is important to develop reliable environmental sample preparation procedures to obtain accurate and reproducible results in the zebrafish embryo toxicity studies. In the present study, we aimed to investigate how different experimental set-ups using a Solid Phase Extraction (SPE) extract of a complex water sample might influence the toxicity assessment using embryos of Danio rerio. Firstly, we assess the influence of two typical carrier solvents (methanol and dimethyl sulfoxide) for dosing environmental extracts. We further investigated the effect of increasing exposure media pH. Finally, we studied the effect of the SPE blank on lethal and sublethal effects in embryos of Danio rerio. Although no significant differences were observed for different solvents, we observed an adverse effect on hatching rate when testing the blank. This indicates the potential impact of background contamination in experimental setups, highlighting the need for appropriate blank correction methods. Furthermore, the differential effects observed with different pH correction methods highlight the importance of carefully selecting the appropriate pH adjustment strategy to accurately assess toxicity levels. Overall, our study enhances the knowledge base and methodology for accurate and comprehensive ecotoxicological assessments in aquatic ecosystems, aiding in the protection and conservation of these fragile environments.

developmental biology↗

bioRxiv2025

On the utilisation and characterisation of external biotransformation systems in in vitro toxicology: a critical review of the scientific literature with guidance recommendations

Incorporating biotransformation capabilities into in vitro assays represents one of the most critical challenges in toxicology, facilitating the transition from in vivo models to integrated in vitro strategies. Although emerging technologies show promise, their current limitations in scalability hinder high-throughput applications. In the short to mid-term, externally added biotransformation systems ("BTS": S9 and microsomal liver fractions) used together with in vitro assays offer viable alternatives. However, despite over fifty years of use, BTS are marred by reproducibility issues, raising concerns about their reliability, and raising the question: Are BTS inherently unreliable, or has their reputation been flawed by methodological oversights? This review critically evaluates BTS methodological rigour, applying a deep statistical analysis of the scientific literature. We employed Boolean operator searches across scientific literature repositories to curate a database on BTS research in conjunction with relevant in vitro assays, focusing on endocrine disruption, mutagenicity, and genotoxicity endpoints. Through systematic searches, screening, and eligibility criteria, we identified 229 bibliographic records. Data parameterisation and extraction were conducted across 24 domains of BTS relevance and reliability. Methodological reporting rigour was assessed via scoring (reported vs. non-reported data items) and revealed a lack of reproducible standards. Numerical measures associated with principal BTS reaction components were subjected to meta-regression analyses. No statistically significant correlations were found for BTS and related cofactor concentration-response relationships or time-related elements. Finally, descriptive statistics, multiple correspondence analysis, and Apriori algorithm-based relational networks identified qualitative patterns of methodological robustness and deficiencies. In conclusion, these results emphasise shortcomings across the scientific literature in complying with appropriate methodological reporting. We offer evidence-based recommendations, in the form of a conceptual regulatory guidance framework, to enhance research practices, quality, and reproducibility of BTS applications; designed to strengthen the robustness of BTS research and its integration into regulatory-relevant hazard and risk assessment of chemicals. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/677684v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@1a6dd9aorg.highwire.dtl.DTLVardef@1ecb22org.highwire.dtl.DTLVardef@1aa3ee3org.highwire.dtl.DTLVardef@6aaf6_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2025

Beyond acute toxicity: evolutionary response by rapid polygenic adaptation to a complex environmental stressor in Chironomus riparius

Anthropogenic stressors, such as pollution, habitat degradation, and climate change, are altering selective pressures on natural populations, but the evolutionary consequences of chronic exposure to complex mixtures of contaminants remain poorly understood. Addressing this knowledge gap is critical to the emerging field of evolutionary ecotoxicology, which aims to understand how long-term exposure to environmental contaminants shapes adaptive evolution and genome-wide variation. In this study, we employed urban runoff sediment as complex and environmentally realistic model stressor to investigate how multigenerational exposure affects fitness and potentially drives genomic adaptation in the freshwater midge Chironomus riparius. We combined an evolutionary life-cycle test with the Evolve and Resequence (E&R) approach, exposing replicate populations over seven generations to three treatments: an uncontaminated control and two concentrations of urban runoff sediment (0.5% and 10%). Key fitness traits, including mortality, mean emergence time (EmT50), fertility, and population growth rate (PGR), were measured, while allele frequency changes (AFC) were tracked to identify genomic signatures of selection. The results revealed distinct and non-linear fitness responses across treatments, including transgenerational effects, recovery of performance, and evidence of life-history trade-offs. Candidate haplotypes were enriched for genes involved in membrane transport, metabolism, and gene regulation, suggesting selection on general stress-response pathways consistent with polygenic adaptation. Signals of selection were also detected in control populations, underscoring the evolutionary influence of laboratory conditions. Overall, our findings demonstrate how evolutionary ecotoxicology can reveal both the potential and the constraints of rapid adaptation to realistic environmental stressors and highlight the importance of integrating evolutionary perspectives into ecological risk assessment.

evolutionary biology↗

bioRxiv2025

Temperature-dependence of Early Development of Zebrafish and the Consequences for Laboratory Use and Animal Welfare

Zebrafish (Danio rerio) are widely used in biological research, but the impact of incubation temperatures on developmental endpoints is still insufficiently studied. This study quantifies developmental differences in zebrafish embryos incubated at 26{degrees}C and 28{degrees}C, focusing on key endpoints (heartbeat onset, hatching time, eye size, yolk sac consumption, and body length). For this purpose, we recorded a high-resolution time series comprising hourly observations of early developmental stages and key events and bi-hourly observations of body length until 120 hours post fertilization. Additionally, we recorded a low-resolution time series at 72, 96, and 119 hours post fertilization for detailed measurements of eye size, yolk sac area, and body length. Embryos incubated at 26{degrees}C showed consistent delays in developmental stages compared to those at 28{degrees}C, with delays becoming more pronounced at later stages. Yolk sac consumption was delayed by about 19.8 hours at 26{degrees}C by 119 hours post fertilization, suggesting a delayed onset of independent feeding. These findings suggest that time-based regulatory limits for rearing zebrafish, such as the 120-hour threshold in German regulations (TierSchVerV), do not fully account for temperature-dependent development. The results emphasize the need for guidelines linking incubation temperatures to developmental progress. Summary StatementThis study highlights the impact of differences in incubation temperatures around the optimum (26 and 28{degrees}C) on zebrafish development. Results suggest reevaluation of animal welfare guidelines for temperature dependency.

developmental biology↗

bioRxiv2024

AI-aided chronic mixture risk assessment along a small European river reveals multiple sites at risk and pharmaceuticals being the main risk drivers

The vast amount of registered chemicals leads to a high diversity of substances occurring in the environment and the creation of new substances outpaces chemical risk assessment as well as monitoring strategies. Hence, risk assessment strategies need to be modified ensuring that they remain aligned with the rapid development and marketing of new substances. Here we performed a longitudinal chronic mixture risk assessment considering a real-world case study scenario with diverse anthropogenic impact types characterised by different land uses along a river in Central Germany. We sampled river water using large-volume solid phase extraction at six selected sampling sites. Following chemical analysis using liquid chromatography-high resolution mass spectrometry, we quantified 192 substances. For 34% of them, we obtained empirical chronic effect data for freshwater organisms. Furthermore, we used the open-source artificial intelligence (AI) model TRIDENT to predict chronic toxicity for all substances. A multi-scenario mixture risk assessment was conducted for three taxonomic groups, using the concentration-addition concept and considering various hazard and exposure scenarios. The results showed that the chronic risk estimates for all taxonomic groups were considerably higher when the empirical data was amended with data from in silico modelling. We identified hot spots of chemical pollution and our analysis indicated that fish were the most vulnerable taxonomic group, with pharmaceuticals being the most relevant risk drivers. Our study exemplifies the application of an AI model to predict chronic risk for aquatic organisms in combination with the consideration of multiple risk scenarios, that may complement future risk assessment strategies. HighlightsO_LI192 organic chemicals were quantified in six surface water samples along a river. C_LIO_LIMultiple hazard and exposure scenarios were considered in mixture risk assessment. C_LIO_LIArtificial intelligence was used to fill data gaps and predict chronic ecotoxicity. C_LIO_LIFish were identified as the most vulnerable taxonomic group for chronic toxicity. C_LIO_LIPharmaceuticals were the most prevalent mixture risk drivers. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/623722v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1836b85org.highwire.dtl.DTLVardef@107eeaaorg.highwire.dtl.DTLVardef@1c60caaorg.highwire.dtl.DTLVardef@16995d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2024

Exposure to complex mixtures of urban sediments containing Tyre and Road Wear Particles (TRWPs) increases the germ-line mutation rate in Chironomus riparius

Tyre and road wear particles (TRWPs) are a significant yet often underestimated source of environmental pollution, contributing to the accumulation of microplastics and a complex mixture of contaminants in both terrestrial and aquatic ecosystems. Despite their prevalence, the long-term evolutionary effects of TRWPs, beyond their immediate toxicity, remain largely unknown. In this study, we assessed mutagenicity in the non-biting midge Chironomus riparius, upon exposure to urban sediment collected from a runoff sedimentation basin. To assess the extent of mutagenic effects over multiple generations, we combined the urban sediment exposure model with short-term mutation accumulation lines (MALs) and subsequent whole genome sequencing (WGS). Our results reveal that the exposure to urban sediment significantly increases mutation rates compared to control groups by 50%, independent of concentration (0.5% and 10%). To infer potential causal processes, we conducted a comparative analysis with known mutational spectra from experiments with other studies. This comparison showed that the mutation profiles induced by urban sediment clearly clustered with those caused by Benzo[a]Pyrene (BaP), a known polycyclic aromatic hydrocarbon (PAH). A comprehensive chemical characterization of the sediment confirmed a considerable impact of road runoff and traffic-related contamination, including PAHs of primarily petrogenic origin. This suggests that PAH-like compounds present in urban sediments may play a significant role in the observed mutagenic effects. Our study shows that urban sediments influence mutation rates and alter mutational spectra in exposed organisms, potentially compromising genomic stability and shaping evolutionary trajectories. Additionally, we show that comparatively analysing mutational spectra may provide valuable insights into mutational processes. These genetic changes may have profound long-term effects on population dynamics and ecosystem health, underscoring the importance of understanding the evolutionary consequences of environmental pollution.

evolutionary biology↗

bioRxiv2024

Air-liquid interface exposure of A549 human lung cells to characterize the hazard potential of a gaseous bio-hybrid fuel blend

Gaseous and semi-volatile organic compounds emitted by the transport sector contribute to air pollution and have adverse effects on human health. To reduce harmful effects to the environment as well as to humans, renewable and sustainable bio-hybrid fuels are explored and investigated in the cluster of excellence "The Fuel Science Center" at RWTH Aachen University. However, data on the effects of bio-hybrid fuels on human health is scarce, leaving a data gap regarding their hazard potential. To help close this data gap, this study investigates potential toxic effects of a Ketone-Ester-Alcohol-Alkane (KEAA) fuel blend on A549 human lung cells. Experiments were performed using a commercially available air-liquid interface exposure system which was optimized beforehand. Then, cells were exposed at the air-liquid interface to 50-2000 ppm C3.7 of gaseous KEAA for 1 h. After a 24 h recovery period in the incubator metabolic activity and cytotoxicity of cells were assessed. Our data support the international occupational exposure limits of the single KEAA constituents and moreover indicate no adverse effect to A549 cells when exposed to a fuel mixture. This finding applies only to the exposure scenario tested in this study and is difficult to extrapolate to the complex in vivo situation.

pharmacology and toxicology↗

bioRxiv2024

Underlying molecular effects to behavioral consequences present line of evidence for zebrafish eye development and function alteration by crude oil exposure.

Crude oil can affect the normal eye development and swimming behavior of fish embryos. In this study 0-4 hours post fertilization (hpf) zebrafish (Danio rerio) embryos were exposed to low, sublethal concentrations of water-accommodated fractions (WAF) of a naphthenic North Sea crude oil alone and in combination with a third-generation chemical dispersant. Effects on eye development and function at the transcript, histological, morphological, and behavioral level were assessed relative to untreated control specimen at 119 hpf. Exposed embryos swam significantly less during the dark phases of the light/dark transition test. Eye size of zebrafish embryos was significantly smaller in groups exposed to crude oil WAFs. Zebrafish retina histology revealed that, among other structural alterations, the outer nuclear layer, containing photoreceptor cells relevant for normal visual functioning, was significantly thinner in exposed embryos. Transcriptome analysis revealed that several genes involved in eye development and function (opsins and crystallins) were dysregulated upon oil exposure. The molecular effects on gene expression and eye histology results form a novel line of evidence that explains the observed effects of crude oil on the swimming activity of exposed fish embryos. The present study is in line with recent findings highlighting the importance of ocular toxicity in developing embryos exposed to petroleum samples at environmentally relevant and non-lethal concentrations without visible malformations. The study suggests that oculotoxicity should be considered as a major toxicity pathway alongside to the well-established cardiotoxicity.

developmental biology↗

bioRxiv2023

100 years of anthropogenic impact causes changes in freshwater functional biodiversity

Despite efforts from scientists and regulators, biodiversity is declining at an alarming rate. Unless we find transformative solutions to preserve biodiversity, future generations may not be able to enjoy natures services. We have developed a conceptual framework that establishes the links between biodiversity dynamics and abiotic change through time and space using artificial intelligence. Here, we apply this framework to a freshwater ecosystem with a known history of human impact and study 100 years of community-level biodiversity, climate change and chemical pollution trends. We apply explainable network models with multimodal learning to community-level functional biodiversity measured with multilocus metabarcoding, to establish correlations with biocides and climate change records. We observed that the freshwater community assemblage and functionality changed over time without returning to its original state, even if the lake partially recovered in recent times. Insecticides and fungicides, combined with extreme temperature events and precipitation, explained up to 90% of the functional biodiversity changes. The community-level biodiversity approach used here reliably explained freshwater ecosystem shifts. These shifts were not observed when using traditional quality indices (e.g. Trophic Diatom Index). Our study advocates the use of high throughput systemic approaches on long-term trends over species-focused ecological surveys to identify the environmental factors that cause loss of biodiversity and disrupt ecosystem functions.

ecology↗

bioRxiv2023

Agricultural pesticides do not suppress infection of Biomphalaria (Gastropoda) by Schistosoma mansoni (Trematoda)

BackgroundSchistosomiasis is a neglected tropical disease caused by trematodes of the genus Schistosoma. The pathogen is transmitted via freshwater snails. These snails indirectly benefit from agricultural pesticides which affect their enemy species. Pesticide exposure of surface waters may thus increase the risk of schistosomiasis transmission unless it also affects the pathogen. MethodologyWe tested the tolerance of the free-swimming infective life stages (miracidia and cercariae) of Schistosoma mansoni to the commonly applied insecticides diazinon and imidacloprid. Additionally, we investigated whether these pesticides decrease the ability of miracidia to infect and further develop as sporocysts within the host snail Biomphalaria pfeifferi. Principal findingsExposure to imidacloprid for 6 and 12 hours immobilized 50% of miracidia at 150 and 16 g/L, respectively (nominal EC50); 50% of cercariae were immobilized at 403 and 284 g/L. Diazinon immobilized 50% of miracidia at 51 and 21 g/L after 6 and 12 hours; 50% of cercariae were immobilized at 25 and 13 g/L. This insecticide tolerance is lower than those of the host snail B. pfeifferi but comparable to those of other commonly tested freshwater invertebrates. Exposure for up to 6 hours decreased the infectivity of miracidia at high sublethal concentrations (48.8 g imidacloprid/L and 10.5 g diazinon/L, i.e. 20 - 33 % of EC50) but not at lower concentrations commonly observed in the field (4.88 g imidacloprid/L and 1.05 g diazinon/L). The development of sporocysts within the snail host was not affected at any of these test concentrations. ConclusionsInsecticides did not affect the performance of S. mansoni at environmentally relevant concentrations. Accordingly, pesticide exposure is likely to increase the risk of schistosomiasis transmission by increasing host snail abundance without affecting the pathogen. Our results illustrate how the ecological side effects of pesticides are linked to human health, emphasizing the need for appropriate mitigation measures. Author summarySchistosomiasis is a major public health problem in 51 countries worldwide. Transmission requires human contact with freshwater snails that act as intermediate hosts, releasing free-swimming life stages of the trematodes. The host snails are highly tolerant to agricultural pesticides used in plant protection products. Pesticides enter freshwaters via drift and runoff, and indirectly foster the spread of host snails via adverse effects on more sensitive competitor and predator species in the water. Increasing the abundance of intermediate hosts raises potential contact with the human definitive host while transmission of the pathogen is not affected. Here we show that pesticides do not affect the ability of the trematode Schistosoma mansoni to infect and develop within its host snail Biomphalaria pfeifferi at environmentally relevant concentrations. Consequently, risk of schistosomiasis increases when pesticide pollution favours the proliferation of snail hosts whilst not negatively affecting the free-living parasites nor their development in their snail hosts. Measures to mitigate pesticide pollution of freshwaters should be a concern in public health programs to sustainably roll back schistosomiasis. Intersectional collaborations are required to bridge the gap between the agricultural and the public health sector in search of sustainable and safe methods of crop production.

systems biology↗