Contribution of Immune Responses to the Cardiotoxicity and Hepatotoxicity of Deltamethrin in Early Life Stage Zebrafish (Danio rerio).

Deltamethrin (DM) is a widely used insecticide that has demonstrated developmental toxicity in the early life stages of fish. To better characterize the underlying mechanisms, embryos from Tg(cmlc2:RFP), Tg(apo14:GFP), and Tg(mpx:GFP) transgenic strains of zebrafish were exposed to nominal DM concentrations of 0.1, 1, 10, 25, and 50 µg/L until 120 h post-fertilization (hpf). Heart size increased 56.7%, and liver size was reduced by 17.1% in zebrafish exposed to 22.7 and 24.2 µg/L DM, respectively. RNA sequencing and bioinformatic analyses predicted that key biological processes affected by DM exposure were related to inflammatory responses. Expression of IL-1 protein was increased by 69.0% in the 24.4 µg/L DM treatment, and aggregation of neutrophils in cardiac and hepatic histologic sections was also observed. Coexposure to resatorvid, an anti-inflammatory agent, mitigated inflammatory responses and cardiac toxicity induced by DM and also restored liver biomass. Our data indicated a complex proinflammatory mechanism underlying DM-induced cardiotoxicity and hepatotoxicity which may be important for key events of adverse outcomes and associated risks of DM to early life stages of fish.

Ecological effects of wastewater treatment modifications on infauna communities off the coast of Orange County, California.

The Orange County Sanitation District (OCSD) is a public agency that provides treatment of wastewater for residents in Orange County, California. The final effluent characteristics at OCSD have been altered in the last 18 years due to the ~20-fold increase of sodium hypochlorite usage for disinfecting waste streams from 2002 to 2010, implementation of the Ground Water Replenishment System (GWRS) in 2008, and conversion to full secondary treatment, together with a major reduction of sodium hypochlorite usage in 2011. This study analyzed infauna data gathered from 1994 to 2016 at the zone of initial dilution (ZID) and reference stations located on the San Pedro Shelf to assess the effects of these treatment process changes on biota in the receiving water. Impacts to the infauna community within the ZID were observed during the period of high chlorine usage, including the increased proportion of the pollution tolerant polychaete Capitella capitata complex from 6.2% in 2003 to nearly 60% in 2010, the lowest Infaunal Trophic Index score in 2009, and the highest Benthic Response Index score in 2006. The degradation of the infauna community in the ZID was correlated with chlorination and was coincidental with the initiation of the GWRS. The infauna community at the ZID recovered rapidly after the implementation of full secondary treatment as indicated by the significant reduction of the relative abundance of C. capitata complex from 59.8% in 2010 to less than 0.1% after 2012, and by the markedly improved community health index scores. This study demonstrated the composition and biointegrity of the infauna community at the ZID varied in response to changes in the wastewater treatment process. Caution should be exercised at wastewater treatment plants when relatively higher dosages of sodium hypochlorite are used over a multi-year period, as this may negatively impact aquatic biota in the receiving water.

Metabolomic Profiles in the Brains of Juvenile Steelhead (Oncorhynchus mykiss) Following Bifenthrin Treatment.

The pyrethroid insecticide, bifenthrin, is frequently measured at concentrations exceeding those that induce acute and chronic toxicity to several invertebrate and fish species residing in the Sacramento-San Joaquin Delta of California. Since the brain is considered to be a significant target for bifenthrin toxicity, juvenile steelhead trout (Oncorhynchus mykiss) were treated with concentrations of bifenthrin found prior to (60 ng/L) and following (120 ng/L) major stormwater runoff events with nontargeted metabolomics used to target transcriptomic alterations in steelhead brains following exposure. Predicted responses were involved in cellular apoptosis and necrosis in steelhead treated with 60 ng/L bifenthrin using the software Ingenuity Pathway Analysis. These responses were predominately driven by decreased levels of acetyl-l-carnitine (ALC), docosahexaenoic acid (DHA), and adenine. Steelhead treated with 120 ng/L bifenthrin had reductions of lysophosphatidylcholines (LPC), lysophosphatidylethanolamines (LPE), and increased levels of betaine, which were predicted to induce an inflammatory response. Several genes predicted to be involved in apoptotic (caspase3 and nrf2) and inflammatory (miox) pathways had altered expression following exposure to bifenthrin. There was a significantly increased expression of caspase3 and miox in fish treated with 120 ng/L bifenthrin with a significant reduction of nrf2 in fish treated with 60 ng/L bifenthrin. These data indicate that bifenthrin may have multiple targets within the brain that affect general neuron viability, function, and signaling potentially through alterations in signaling fatty acids.

Novel Disinfection Byproducts Formed from the Pharmaceutical Gemfibrozil Are Bioaccumulative and Elicit Increased Toxicity Relative to the Parent Compound in Marine Polychaetes (Neanthes arenaceodentata).

Formation of halogenated disinfection byproducts (DBPs) from pharmaceutically active compounds has been observed in water supply systems following wastewater chlorination. Although research has been limited thus far, several studies have shown that halogenated DBPs may elicit increased toxicity compared to their parent compounds. For example, the lipid regulator gemfibrozil has been shown to form chlorogemfibrozil (Cl-gemfibrozil) and bromogemfibrozil (Br-gemfibrozil) following chlorination, which are more potent antiandrogens in male Japanese medaka (Oryzias latipes) compared to their parent compounds. In the present study, we aimed to characterize the bioaccumulative ability of halogenated gemfibrozil DBPs in marine polychaetes via chronic sediment exposures and, consequently, to assess the chronic and acute toxicity of halogenated gemfibrozil DBPs through sediment (in vivo) and aqueous (in vivo and in silico) toxicity evaluations. Following 28 day sediment exposures, Cl-gemfibrozil and Br-gemfibrozil bioaccumulated within Neanthes arenaceodentata, with both compounds reducing survival and growth. The biota-sediment accumulation factors determined for Cl-gemfibrozil and Br-gemfibrozil were 2.59 and 6.86, respectively. Furthermore, aqueous 96 h toxicity tests with N. arenaceodentata indicated that gemfibrozil DBPs elicited increased toxicity compared to the parent compound. While gemfibrozil had an acute LC50 value of 469.85 ± 0.096 mg/L, Cl-gemfibrozil and Br-gemfibrozil had LC50 values of 12.34 ± 0.085 and 9.54 ± 0.086 mg/L, respectively. Although acute toxicity is relatively low, our results indicate that halogenated gemfibrozil DBPs are bioaccumulative and may elicit effects in apex food web organisms prone to accumulation following lifelong exposures.

Recessivity of pyrethroid resistance and limited interspecies hybridization across Hyalella clades supports rapid and independent origins of resistance.

Several populations of the amphipod, Hyalella azteca, have developed resistance to pyrethroid insecticides due to non-target exposure, but the dominance of the resistance trait is unknown. The current study investigated the dominance level of point mutations in natural populations of insecticide-resistant H. azteca and determined whether H. azteca from different clades with and without resistant alleles can hybridize and produce viable offspring. A parent generation (P0) of non-resistant homozygous wild type H. azteca was crossbred with pyrethroid-resistant homozygous mutant animals and the tolerance of the filial 1 (F1) generation to the pyrethroid insecticide, permethrin, was measured. Then the genotypes of the F1 generation was examined to assure heterozygosity. The resistant parents had permethrin LC50 values that ranged from 52 to 82 times higher than the non-resistant animals and both crossbreeding experiments produced heterozygous hybrid offspring that had LC50 values similar to the non-resistant H. azteca parent. Dominance levels calculated for each of the crosses showed values close to 0, confirming that the L925I and L925V mutations were completely recessive. The lack of reproduction by hybrids of the C x D breeding confirmed that these clades are reproductively isolated and therefore introgression of adaptive alleles across these clades is unlikely. Potential evolutionary consequences of this selection include development of population bottlenecks, which may arise leading to fitness costs and reduced genetic diversity of H. azteca.

Transcriptomic Responses of Bisphenol S Predict Involvement of Immune Function in the Cardiotoxicity of Early Life-Stage Zebrafish (Danio rerio).

Bisphenol S (BPS), an alternative for bisphenol A (BPA) that is present in thermal paper and numerous consumer products, has been linked to estrogenic, cytotoxic, genotoxic, neurotoxic, and immunotoxic responses. However, the mechanisms of BPS toxicity remain poorly understood. Here, following exposure to environmentally relevant concentrations ranging from 0.1 to 100 µg/L BPS, transcriptional changes evaluated by enriched gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Ingenuity Pathway Analysis (IPA) predicted cardiac disease and impairment of immune function in zebrafish at the embryo-to-larvae stage. Consistent with impacts predicted by transcriptional changes, significant sublethal impacts were observed ranging from reduced heart rate [8.7 ± 2.4% reductions at 100 µg/L BPS treatment; P < 0.05] to abnormal cardiac morphology [atrial/ventricle area significantly increased; 36.2 ± 9.6% at 100 µg/L BPS treatment; P < 0.05]. RNA-sequencing analysis results also indicated changes in nitric oxide synthetase (NOS2) and interleukin 12 (IL12) after BPS treatment, which was confirmed at the protein level. Increased expression of other cytokine genes was observed in larvae, suggesting inflammatory responses may be contributing to cardiac impairment by BPS. BPS caused cardiotoxicity, which temporally corresponded with inflammatory responses as predicted from RNA sequencing and confirmed at the protein and cellular levels of biological organization. Additional study is needed to find causal linkages between these responses.

Examining the role of estrogenic activity and ocean temperature on declines of a coastal demersal flatfish population near the municipal wastewater outfall of Orange County, California, USA.

Wastewater treatment plant effluent introduces a mixture of pollutants into marine environments; however, the impacts of chronic sublethal exposures on populations are often unclear. Presence of estrogenic agents in sediments and uptake of these compounds by demersal flatfishes has been reported at the Orange County Sanitation District (OCSD) wastewater outfall. Furthermore, estrogenic activity has been identified in male flatfish in the area, potentially contributing to observed population declines in the OCSD region. Rising ocean temperatures may further contribute to flatfish declines as relationships between temperature and abundance have been reported in the Southern California Bight. To investigate declines, sex ratios, condition factor, organ health indices, hormones, and vitellogenin were quantified in flatfish collected at OCSD outfall and reference sites. Additionally, historical temperature data was examined for trends with population abundances. Rather than being linked to estrogenic activity, results indicated that population declines were more correlated to increases in ocean temperature.