Sublethal Levels Research Articles

Life in a contaminant milieu: PPCP mixtures generate unpredictable outcomes across trophic levels and life stages

AbstractNearly all aquatic ecosystems are affected by sublethal levels of anthropogenic chemical contamination, but other agents of large‐scale anthropogenic disruption of ecosystems have received more attention. Consequently, ecologists do not fully appreciate how sublethal contaminant exposure affects ecosystems. Sublethal contaminants can affect ecological systems directly via their impacts on an organism's fitness or indirectly by changing the strengths of species interactions. This study investigated how an emerging class of contaminants—pharmaceuticals and personal care products (PPCPs)—influences food webs by affecting the biology of organisms and by interfering with predator–prey interactions. Specifically, we investigated how three common PPCPs—caffeine, DEET (N, N‐diethyl‐meta‐toluamide), and triclosan—affect the strength of the interaction between a common mosquito predator (i.e., mosquito fish) and mosquito larvae as well as how these PPCPS affect mosquito survival, life history traits, and oviposition site choices. We found that all three PPCPs, individually and combined as a mixture, reduced predator consumption rates. Relative to a contaminant‐free control, the presence of predator cues reduced mosquito oviposition and larval abundance for all PPCP treatments except for DEET. Predator cues reduced mosquito adult emergence across PPCP treatments; however, mosquitoes that were exposed to caffeine did not emerge as adults even in the absence of predator cues. This study shows that the effects of PPCPs are diverse and can interact with mosquitoes and their predators in ways that cannot be predicted by their individual effects. In a contaminated world, ecologists need to better understand how sublethal concentrations of ubiquitous, biologically active pollutants might challenge what we think we know about how ecological systems function.

Genome-wide survey of cytochrome P450 genes in the salmon louse Lepeophtheirus salmonis (Kr\xf8yer, 1837)

BackgroundThe salmon louse (Lepeophtheirus salmonis) infests farmed and wild salmonid fishes, causing considerable economic damage to the salmon farming industry. Infestations of farmed salmon are controlled using a combination of non-medicinal approaches and veterinary drug treatments. While L. salmonis has developed resistance to most available salmon delousing agents, relatively little is known about the molecular mechanisms involved. Members of the cytochrome P450 (CYP) superfamily are typically monooxygenases, some of which are involved in the biosynthesis and metabolism of endogenous compounds, while others have central roles in the detoxification of xenobiotics. In terrestrial arthropods, insecticide resistance can be based on the enhanced expression of CYPs. The reported research aimed to characterise the CYP superfamily in L. salmonis and assess its potential roles in drug resistance.MethodsLepeophtheirus salmonis CYPs were identified by homology searches of the genome and transcriptome of the parasite. CYP transcript abundance in drug susceptible and multi-resistant L. salmonis was assessed by quantitative reverse transcription PCR, taking into account both constitutive expression and expression in parasites exposed to sublethal levels of salmon delousing agents, ecdysteroids and environmental chemicals.ResultsThe above strategy led to the identification of 25 CYP genes/pseudogenes in L. salmonis, making its CYP superfamily the most compact characterised for any arthropod to date. Lepeophtheirus salmonis possesses homologues of a number of arthropod CYP genes with roles in ecdysteroid metabolism, such as the fruit fly genes disembodied, shadow, shade, spook and Cyp18a1. CYP transcript expression did not differ between one drug susceptible and one multi-resistant strain of L. salmonis. Exposure of L. salmonis to emamectin benzoate or deltamethrin caused the transcriptional upregulation of certain CYPs. In contrast, neither ecdysteroid nor benzo[a]pyrene exposure affected CYP transcription significantly.ConclusionsThe parasite L. salmonis is demonstrated to possess the most compact CYP superfamily characterised for any arthropod to date. The complement of CYP genes in L. salmonis includes conserved CYP genes involved in ecdysteroid biosynthesis and metabolism, as well as drug-inducible CYP genes. The present study does not provide evidence for a role of CYP genes in the decreased susceptibility of the multiresistant parasite strain studied.

Effects of Monocrotophos on Some Biochemical Parameters in Fresh Water Fish Oreochromis Mossambicus (Tilapia)

The toxic effect of Monocrotophos on some biochemical parameters such as Protein and Amino acid in freshwater fish Oreochromis mossambicus were studied. The fishes exposed to 1/10th, 1/20th, and 1/30th sublethal concentration of Monocrotophos for 30 days. The tissue samples of gill, liver were analysed at the end of the 30th day exposure period. A decreased value of Protein and Amino acid were observed in 1/10th, 1/20th, and 1/30th sub lethal concentration of Monocrotophos at the exposure period of 30 days while comparing with the control group. The high variation observed in the 1/10th sublethal level of 30thday exposure. While compare with control group the effects of Monocrotophos on fish found during this experiment showed that the level of protein and amino acid level in various tissues (gill and liver) of Oreochromis mossambicus decreased.

Blue Light Sensing in Listeria monocytogenes Is Temperature-Dependent and the Transcriptional Response to It Is Predominantly SigB-Dependent

Listeria monocytogenes is an important food-borne pathogen that is tolerant to many of the stresses commonly used during food preservation. Outside the host, the bacterium has a saprophytic lifestyle that includes periodic exposure to solar irradiance. The blue component of this light is known to influence the activity of the stress-inducible sigma factor Sigma B (σB). In this study, the influence of temperature and growth phase on the response of L. monocytogenes to blue light was investigated and the global transcriptional response to blue light was elucidated using an RNAseq-based approach. Stationary phase cells were found to be significantly more resistant to killing by blue light (470 nm) than exponential phase cells. Temperature also had a marked effect on blue light resistance with cells cultured at 37°C being much more sensitive than cells grown at 30°C. The role of σB in light tolerance was confirmed but this effect was observed only at 30°C. σB activation by blue light was assessed by measuring the transcriptional response of known σB-dependent genes (sigB, lmo2230, and opuCA) to light. The transcripts were induced by blue light only at 30°C suggesting that blue light fails to activate σB at 37°C. The light-induced transcription at 30°C was dependent on a functional blue light sensor, Lmo0799 (which we rename herein as RsbL). A transcriptomic analysis of the response to sub-lethal levels of blue light found that the changes in transcription were almost entirely σB-dependent. A mutant where the light sensing mechanism of RsbL was inactivated through an amino acid substitution (Cys56Ala) was found to have an attenuated response to blue light, but residual activation of σB-dependent genes suggested that alternative routes for activation of σB by light are likely to exist. Overall, the study highlights the central role of σB in the response of this pathogen to visible light and further shows that light sensing is absent at temperatures that exist within the mammalian host.

Effects of cadmium, inorganic mercury and methyl-mercury on the physiology and metabolomic profiles of shoots of the macrophyte Elodea nuttallii

Macrophytes are known to bioaccumulate metals, but a thorough understanding of tolerance strategies and molecular impact of metals in aquatic plants is still lacking. The present study aimed to compare Hg and Cd effects in a representative macrophyte, Elodea nuttallii using physiological endpoints and metabolite profiles in shoots and cytosol.Exposure 24 h to methyl-Hg (30 ng L−1), inorganic Hg (70 ng L−1) and Cd (280 μg L−1) did not affect photosynthesis, or antioxidant enzymes despite the significant accumulation of metals, confirming a sublethal stress level. In shoots, Cd resulted in a higher level of regulation of metabolites than MeHg, while MeHg resulted in the largest number of regulated metabolites and IHg treatment regulated no metabolites significantly. In cytosol, Cd regulated more metabolites than IHg and only arginine, histidine and mannose were reduced by MeHg exposure. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of data suggested that exposure to MeHg resulted in biochemical changes including aminoacyl-tRNA biosynthesis, glycine, serine and threonine metabolism, nitrogen metabolism, arginine and proline metabolism, cyanoamino acid metabolism, while the treatment of Cd stress caused significant variations in aminoacyl-tRNA biosynthesis and branched-chain amino acids pathways. Data supports an impact of MeHg on N homeostasis, while Cd resulted in an osmotic stress-like pattern and IHg had a low impact. Marked differences in the responses to MeHg and IHg exposure were evidenced, supporting different molecular toxicity pathways and main impact of MeHg on non-soluble compartment, while main impact of IHg was on soluble compartment. Metabolomics was used for the first time in this species and proved to be very useful to confirm and complement recent knowledge gained by transcriptomics and proteomics, highlighting the high interest of multi-omics approaches to identify early impact of environmental pollution.

Assessment of hematological, hepato-renal, antioxidant, and hormonal responses of Clarias gariepinus exposed to sub-lethal concentrations of oxyfluorfen

Little is known about the effects of oxyfluorfen, a diphenyl ether herbicide, exposure on the African catfish (Clarias gariepinus) health. Consequently, the existing investigation was designed to highlight the impacts of oxyfluorfen exposure on C. gariepinus hematological indices, liver and kidney functions, reproductive hormones, and oxidative status. Furthermore, a consequent 10-day depuration period was adopted to evaluate the recovery of the disturbed indicators to normal values. In the first experiment, the 96-h lethal concentration 50 (LC50) of oxyfluorfen for C. gariepinus was determined using probit analysis. Next, in a second experiment, 180 healthy fish (average initial body weight: 164.23 ± 0.24) were randomly assigned to 4 experimental groups exposed to 0, 1/10, 1/8, or 1/5 96-h LC50 of oxyfluorfen. The hematological profile, hepatic enzymes, kidney damage byproducts, reproductive hormones, oxidative stress, and lipid peroxidation indicators together with acetylcholinesterase (AChE) content were assessed. A histopathological examination of the hepatic, renal, brain, and testicular tissues was accomplished. Moreover, the expression of the oxidative stress-related gene was carried out. The results showed that 96-h LC50 of oxyfluorfen for C. gariepinus was 11.698 mg/L. Exposure to sublethal levels of oxyfluorfen induced macrocytic hypochromic anemia, leukopenia, lymphopenia, monocytopenia, and eosinopenia. Also, a concentration-dependent increase in alanine transaminase, alkaline phosphatase, aspartate transaminase, urea, creatinine, catalase, and malondialdehyde was detected following oxyfluorfen exposure together with upregulation of catalase gene. But, significant concentration-dependent reductions in AChE, glutathione transferase, reduced to oxidized glutathione ratio, estradiol, and testosterone activities were recorded. These biochemical alterations were accompanied by pathological perturbations in hepatic, renal, brain, and testicular tissues. Following 10 days of recovery, only the hematological impairments were abolished. Conclusively, the herbicides oxyfluorfen could induce multiple negative impacts on C. gariepinus with oxidative stress as a probable underlying mechanism. Additionally, a recovery period of 10 days was not enough to restore these impairments.

Chronic exposure to sub-lethal concentrations of antibiotics in rural population and consequent health risks

TPS 751: Farms, antibiotics, infections, Exhibition Hall, Ground floor, August 26, 2019, 3:00 PM - 4:30 PM Background: Chronic exposure to sub-lethal concentrations of antibiotic is mostly ignored. The rural environment receives antibiotics and their residues from agriculture, livestock and human that may persist for long-time. Hence public exposure in rural world to antibiotics is multifaceted and need health risk assessment. Aims: This study aimed to (i) quantify ethical and unethical antibiotic usage, their concentrations and residues in rural environment (ii) assess chronic exposure of rural population to antibiotics and consequent health risks among rural population. Methods: Field soil, fecal and irrigation water samples were analyzed for fluoroquinolones and quinolone antibiotics. Target rural population (n=234) were surveyed which includes livestock handlers, agricultural farmers, field workers, female households and children, to assess extent of exposure to antibiotic persist in their immediate environment and epidemiological symptoms. Results: Significant use of ciprofloxacin as self-medication (unethical) was strongly correlated with flu and gastrointestinal infections. Among females gastro (OR=1.51; 95% CI=1.16–1.95) whereas in livestock workers both flu (OR=1.39; 95% CI=1.07–1.80) and gastro (OR=2.11; 95% CI=1.62–2.74) incidences were recorded as consequent impact of chronic exposure to antibiotics. In feces wide range of ciprofloxacin was detected (97.5–188.2 mg kg–1) whereas amount of levofloxacin and ofloxacin were within the WHO regulatory limits. Wastewater channels from rural dwellings and livestock farms were identified as potential hotspots for chronic exposure. Indiscriminate use of antibiotics to enhance dairy produce has forced rural people to indulge in unethical drug administration which has increased their susceptibility to further exposure to antibiotics and their residues in rural environment. Conclusions: We conclude that chronic exposure of rural population to antibiotics and their residues provoke health risks and this exposure is on rise due to continuous add-up of sub-lethal levels linked with self-administrated usage which must be strictly checked to minimize their release in environment.

Ethanol Adaptation Strategies in Salmonella enterica Serovar Enteritidis Revealed by Global Proteomic and Mutagenic Analyses.

Salmonella enterica subsp. enterica serovar Enteritidis is able to adapt to sublethal concentrations of ethanol, which subsequently induce tolerance of this pathogen to normally lethal ethanol challenges. This work aims to elucidate the underlying ethanol adaptation mechanisms of S Enteritidis by proteomic and mutagenic analyses. The global proteomic response of S Enteritidis to ethanol adaptation (5% ethanol for 1 h) was determined by isobaric tags for relative and absolute quantification (iTRAQ), and it was found that a total of 138 proteins were differentially expressed in ethanol-adapted cells compared to nonadapted cells. A total of 56 upregulated proteins were principally associated with purine metabolism and as transporters for glycine betaine, phosphate, d-alanine, thiamine, and heme, whereas 82 downregulated proteins were mainly involved in enterobactin biosynthesis and uptake, the ribosome, flagellar assembly, and virulence. Moreover, mutagenic analysis further revealed the functions of two highly upregulated proteins belonging to purine metabolism (HiuH, 5-hydroxyisourate hydrolase) and glycine betaine transport (ProX, glycine betaine-binding periplasmic protein) pathways. Deletion of either hiuH or proX resulted in the development of a stronger ethanol tolerance response, suggesting negative regulatory roles in ethanol adaptation. Collectively, this work suggests that S Enteritidis employs multiple strategies to coordinate ethanol adaptation.IMPORTANCE Stress adaptation in foodborne pathogens has been recognized as a food safety concern since it may compromise currently employed microbial intervention strategies. While adaptation to sublethal levels of ethanol is able to induce ethanol tolerance in foodborne pathogens, the molecular mechanism underlying this phenomenon is poorly characterized. Hence, global proteomic analysis and mutagenic analysis were conducted in the current work to understand the strategies employed by Salmonella enterica subsp. enterica serovar Enteritidis to respond to ethanol adaptation. It was revealed that coordinated regulation of multiple pathways involving metabolism, ABC transporters, regulators, enterobactin biosynthesis and uptake, the ribosome, flagellar assembly, and virulence was responsible for the development of ethanol adaptation response in this pathogen. Such knowledge will undoubtedly contribute to the development and implementation of more-effective food safety interventions.

Histopathological Changes Induced by Chronic, Sub- Lethal Diazinon Exposure in Alligator Gar (Atractosteus Spatula) Tissues

Diazinon is a widely used household and agricultural pesticide that accumulates in the aquatic environment and adversely affects non-target organisms such as mammals, birds, and fish. Sub-lethal pesticide levels occur in natural waters, and can impact the health, physiology and fitness of fish populations. This study was conducted to assess the effects of chronic, sub-lethal diazinon exposure to skin, liver, kidney, spleen, heart, gut, intestine, and gas bladder tissues of alligator gar, Atractosteus spatula. In two studies, gar were exposed to sub-lethal concentrations of 0.01, and 0.1 mg/L diazinon for 15 and 30 day periods. Skin, gills, liver, and kidney of exposed fish demonstrated remarkable microscopic lesions. These changes included skin lesions in the head and body, which started as white spots and progressed into deep ulcerations, hepatic vacuolation, swollen hepatocytes, steatosis, aggregation of macrophages, necrosis, and hepatic fibrosis. Gill tissues demonstrated epithelial hyperplasia in the secondary lamellae. Vacuolar degeneration was also present in the hematopoietic tissues of the kidney. Lesion occurrence and severity were correlated to increased diazinon dose and exposure time. Our findings revealed the harmful effects of chronic, sub-lethal diazinon exposure on alligator gar, and suggest other aquatic organisms may also be affected by sub-lethal concentrations of pollutants in their environment.

Effects of Chlorpyrifos Exposure on Acetylcholine Metabolism across a Model Blood-Brain Barrier

Organophosphate (OP) compounds, used throughout the agricultural industry as insecticides, are known to directly and irreparably alter brain function in humans. Exposure to OPs decreases acetylcholinesterase activity and leads to a buildup of acetylcholine, with chronic exposure to sub-lethal levels inducing neuropathy. This buildup of acetylcholine can be monitored through electrochemical methods to study the effects of OP toxicity. The microclinical analyzer (µCA), an in vitro microfluidic device allowing for electrochemical analysis using a screen-printed electrode, can be modified with enzymes to detect acetylcholine. Using the µCA in combination with the neurovascular unit (NVU), an organotypic model of the blood-brain barrier (BBB), can provide a better understanding of the BBB forms, functions, and responds to insults. The NVU supports all the cell types necessary for proper BBB formation (endothelial cells, astrocytes, pericytes, and neurons) and provides the flow-created shear forces for mature tight junction formation. The µCA and NVU were used study the effects of chlorpyrifos on acetylcholine concentrations present across the BBB. Understanding the effects of OP like chlorpyrifos on neurotoxicity can contributes to the assessment and treatment of chronic and acute exposure and inform policy decisions around the uses of OP pesticides in the agricultural industry.

Synergistic effects of three sterol biosynthesis inhibiting fungicides on the toxicity of a pyrethroid and neonicotinoid insecticide to bumble bees

Understanding how different pesticides influence bee health is inhibited by a limited knowledge about the interactions between different compounds to which bees are simultaneously exposed. Although research has demonstrated synergistic effects of some sterol biosynthesis inhibiting (SBI) fungicides on the toxicity of certain insecticides to bees, a high degree of variability exists in the relatively few SBI fungicide-insecticide interactions tested. Furthermore, most research has been conducted on honey bees, Apis mellifera, limiting our understanding of pesticide synergisms in native wild bees. We tested the effects of the SBI fungicides difenoconazole, myclobutanil, and fenhexamid on acute contact toxicity of the insecticides thiamethoxam (neonicotinoid) and bifenthrin (pyrethroid) to the common eastern bumble bee, Bombus impatiens. Based on range-finding trials, we selected a single dosage of each pesticide, with insecticides approximating LD20 values and fungicides approximating their maximum sublethal levels. We found that the triazole SBI fungicide difenoconazole interacted synergistically with bifenthrin, with a maximum synergy ratio of 1.48, while the triazole myclobutanil interacted synergistically with both bifenthrin and thiamethoxam, with maximum synergy ratios of 11.0 and 2.38, respectively. However, the hydroxyanilide SBI fungicide fenhexamid did not exhibit a synergistic effect on either insecticide. Our results suggest that certain SBI fungicides, and potentially those from particular SBI classes, may be particularly harmful to bumble bee health when co-exposure to insecticides occurs, despite their low toxicity when experienced in isolation.

Deletion of the benzoxazinoid detoxification gene NAT1 in Fusarium graminearum reduces deoxynivalenol in spring wheat.

Benzoxazinoid (Bx) metabolites produced by wheat and other members of the Poaceae have activity against Fusarium sp. that cause cereal diseases including Fusarium head blight (FHB) on wheat and barley. Certain Bx metabolites can be detoxified by Fusarium sp. with the arylamine N-acetyltransferase NAT1. Investigation of this pathway may reveal strategies for increasing FHB resistance, such as selection for higher levels of Bx metabolites within existing germplasm and/or engineering fungal susceptibility via host induced silencing of NAT1. We assessed the reactions of fifteen wheat cultivars or breeding lines adapted to the Northwestern United States to infection with F. graminearum Δnat1 mutants that should be sensitive to Bx metabolites. Significant differences were noted in disease severity and deoxynivalenol (DON) among the cultivars 21 d after inoculation with either mutant or wildtype (PH1) strains. Mutant vs. wildtype strains did not result in significant variation for infection severity (as measured by % infected florets), but inoculation with Δnat1 mutants vs. wildtype resulted in significantly lower DON concentrations in mature kernels (p < 0.0001). Of the cultivars tested, HRS3419 was the most resistant cultivar to PH1 (severity = 62%, DON = 45 ppm) and Δnat1 mutants (severity = 61%, DON = 30 ppm). The cultivar most susceptible to infection was Kelse with PH1 (severity = 100%, DON = 292 ppm) and Δnat1 mutants (severity = 100%, DON = 158 ppm). We hypothesized that sub-lethal Bx metabolite levels may suppress DON production in F. graminearum Δnat1 mutants. In vitro assays of Bx metabolites BOA, MBOA, and DIMBOA at 30 μM did not affect growth, but did reduce DON production by Δnat1 and PH1. Although the levels of Bx metabolites are likely too low in the wheat cultivars we tested to suppress FHB, higher levels of Bx metabolites may contribute towards reductions in DON and FHB.

How glyphosate and its associated acidity affect early development in zebrafish (Danio rerio).

BackgroundGlyphosate is among the most extensively used pesticides worldwide. Following the ongoing highly controversial debate on this compound, its potential impact on non-target organisms is a fundamental scientific issue. In its pure compound form, glyphosate is known for its acidic properties.MethodsWe exposed zebrafish (Danio rerio) embryos to concentrations between 10 μM and 10 mM glyphosate in an unbuffered aqueous medium, as well as at pH 7, for 96 hours post fertilization (hpf). Furthermore, we investigated the effects of aqueous media in the range of pH 3 to 8, in comparison with 1 mM glyphosate treatment at the respective pH levels. Additionally, we exposed zebrafish to 7-deoxy-sedoheptulose (7dSh), another substance that interferes with the shikimate pathway by a mechanism analogous to that of glyphosate, at a concentration of one mM. The observed endpoints included mortality, the hatching rate, developmental delays at 24 hpf, the heart rate at 48 hpf and the malformation rate at 96 hpf. LC10/50, EC10 and, if reasonable, EC50 values were determined for unbuffered glyphosate.ResultsThe results revealed high mortalities in all treatments associated with low pH, including high concentrations of unbuffered glyphosate (>500 μM), low pH controls and glyphosate treatments with pH < 3.4. Sublethal endpoints like developmental delays and malformations occurred mainly at higher concentrations of unbuffered glyphosate. In contrast, effects on the hatching rate became particularly prominent in treatments at pH 7, showing that glyphosate significantly accelerates hatching compared with the control and 7dSh, even at the lowest tested concentration. Glyphosate also affected the heart rate, resulting in alterations both at pH 7 and, even more pronounced, in the unbuffered system. In higher concentrations, glyphosate tended to accelerate the heart rate in zebrafish embryos, again, when not masked by the decelerating influence of its low pH. At pH > 4, no mortality occurred, neither in the control nor in glyphosate treatments. At 1 mM, 7dSh did not induce any mortality, developmental delays or malformations; only slightly accelerated hatching and a decelerated heart rate were observed. Our results demonstrate that lethal impacts in zebrafish embryos can be attributed mainly to low pH, but we could also show a pH-independent effect of glyphosate on the development of zebrafish embryos on a sublethal level.

Does winter oilseed rape grown from clothianidin-coated seeds affect experimental populations of mason bees and bumblebees? A semi-field and field study

Impacts of neonicotinoid-containing pesticides on pollinators have been heavily debated in recent years. While bees in the field get rarely exposed to lethal concentrations of neonicotinoids applied as seed coating, sublethal levels found in pollen and nectar may affect bee population development. We assessed a realistic and a worst-case scenario of clothianidin exposure to mason bees (Osmia bicornis) and bumblebees (Bombus terrestris) by conducting a small-scale field and semi-field experiment at sites planted with winter oilseed rape. Flight activity, mortality and population development (brood, colony strength and weight) of bumblebees and number of mason bee brood cells were assessed at three locations. We also analysed clothianidin residues in bee-collected pollen and nectar. We detected clothianidin at low concentrations in nectar and pollen; residues in pollen were higher than in nectar but did not exceed a maximum field concentration of 2.7 µg/kg for bumblebees and 4.7 µg/kg for mason bees. Exposure did not result in significant negative impacts on bumblebee colony development and potential reproductive success of mason bees in either semi-field or field setup. During exposure bumblebees in semi-field treatment tunnels were flying less actively than in control tunnels. Bumblebee colonies in treatment tunnels weighed more than control colonies at the end of the experiment. Our findings suggest that field-realistic exposure to oilseed rape grown from clothianidin-treated seeds (10 g clothianidin/kg seeds) poses little risks to mason bees, bumblebees and their population development. However, an impairment of flower visitation under a worst-case scenario may have implications for pollination services and crop production.

Autophagic degradation of stromal interaction molecule 2 mediates disruption of neuronal dendrites by endoplasmic reticulum stress.

Endoplasmic reticulum (ER) stress has been highlighted as one of the factors involved in axon/dendrite degeneration, which is an early event in Alzheimer's, Parkinson's diseases as well as in acute disorders such as ischemia and axotomy-induced retinal ganglion cell degeneration. These lines of evidence suggest critical roles of ER stress at the early stage of neurodegeneration, but the relevant mechanism is rarely exploited. In this study, we report that treatment with sublethal level of ER stressors, tunicamycin or brefeldin A, in primary rat neuronal cultures, significantly reduced dendrite arbor. Under the same treatment, either stressor reduced store-operated calcium entry (SOCE) and cytosolic calcium, [Ca2+ ]i , which were associated with autophagic degradation of stromal interaction molecule 2 (STIM2). Knockdown of ATG7 or activating transcription factor 4 completely reversed the reduction of STIM2 and significantly reversed the inhibition of SOCE under ER stress. Overexpression of STIM2 in neurons significantly prevented the ER stress-induced disruption of dendrite arbor. Altogether, our data reveal an unprecedented mechanism by which ER stress induces dendrite degeneration, that is, ER stress induces autophagic degradation of STIM2, leading to ensued SOCE inhibition and reduced [Ca2+ ]i , resulting in trimming effect on dendrites.

Tropodithietic acid induces oxidative stress response, cell envelope biogenesis and iron uptake in Vibrio vulnificus.

The Roseobacter group is a widespread marine bacterial group, of which some species produce the broad-spectrum antibiotic tropodithietic acid (TDA). A mode of action for TDA has previously been proposed in Escherichia coli, but little is known about its effect on non-producing marine bacteria at in situ concentrations. The purpose of this study was to investigate how a sub-lethal level of TDA affects Vibrio vulnificus at different time points (30 and 60 min) using a transcriptomic approach. Exposure to TDA for as little as 30 min resulted in the differential expression of genes associated with cell regeneration, including the up-regulation of those involved in biogenesis of the cell envelope. Defence mechanisms including oxidative stress defence proteins and iron uptake systems were also up-regulated in response to TDA, while motility-related genes were down-regulated. Gene expression data and scanning electron microscopy imaging revealed a switch to a biofilm phenotype in the presence of TDA. Our study shows that a low concentration of this antibiotic triggers a defence response to reactive oxygen species and iron depletion in V. vulnificus, which indicates that the mode of action of TDA is likely more complex in this bacterium than what is known for E. coli.

Heavy Metals in Biota in Delaware Bay, NJ: Developing a Food Web Approach to Contaminants.

Understanding the relationship between heavy metal and selenium levels in biota and their foods is important, but often difficult to determine because animals eat a variety of organisms. Yet such information is critical to managing species populations, ecological integrity, and risk to receptors (including humans) from consumption of certain prey. We examine levels of cadmium, lead, mercury, and selenium in biota from Delaware Bay (New Jersey, USA) to begin construction of a “springtime” food web that focuses on shorebirds. Horseshoe crab (Limulus polyphemus) eggs are one of the key components at the base of the food web, and crab spawning in spring provides a food resource supporting a massive stopover of shorebirds. Fish and other biota also forage on the crab eggs, and a complex food web leads directly to top-level predators such as bluefish (Pomatomus saltatrix) and striped bass (Morone saxatilis), both of which are consumed by egrets, eagles, ospreys (Pandion haliaetus), and humans. Metal levels in tissues were generally similar in algae, invertebrates, and small fish, and these were similar to those in blood of shorebirds (but not feathers). There was a significant direct relationship between the levels of metals in eggs of horseshoe crabs and mean metal levels in the blood of four species of shorebirds. Metal levels in shorebird feathers were higher than those in blood (except for selenium), reflecting sequestration of metals in feathers during their formation. Levels in feathers of laughing gulls (Leucophaeus atricilla) were similar to those in feathers of shorebirds (except for selenium). Selenium bears special mention as levels were significantly higher in the blood of all shorebird species than in other species in the food web, and were similar to levels in their feathers. Levels of metals in bluefish and striped bass were similar or higher than those found in the blood of shorebirds (except for selenium). The mean levels of cadmium, lead, and mercury in the blood and feathers of shorebirds were below any effect levels, but selenium levels in the blood and feathers of shorebirds were higher than the sublethal effect levels for birds. This is a cause for concern, and warrants further examination.

Antioxidant enzyme cycling over reproductive lunar cycles in Pocillopora damicornis.

The impacts of continued degradation of watersheds on coastal coral reefs world-wide is alarming, and action addressing anthropogenic stressors and subsequent rehabilitation of watersheds and adjacent reefs is an urgent priority. The aim of this study is to develop and improve the use of antioxidant enzymes as bioindicators of stress in coral species. In order to fully develop such tools, it is necessary to first understand baseline cycling of these enzymes within coral tissues. Due to inherent links between reproduction and oxidative stress, these aims may be facilitated by sampling coral tissues over reproductively-linked lunar cycles to determine variations from baseline. By developing a greater understanding of biochemical markers of stress in corals, specifically antioxidant defense enzymes catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in Hawaiian Pocillopora damicornis, we have provided molecular tools that identify thresholds of stress on coral reefs. Our results suggest that the coral reproductive state is a significant factor affecting the activity of antioxidant enzymes. Specifically, CAT and GR display maximum activity during peak reproductive state. Whereas significant maximal Se-independent GPx and SOD activity was measured during off-peak reproductive cycles. Such insight into the cyclical variation of the activity of these enzymes should be applied towards differentiating the influence of natural biological activity cycling in diagnostic tests identifying the effects of different physical environmental factors and chemical pollutants on coral health. Through the development and application of these molecular biomarkers of stress, we look to improve our ability to identify problems at the sub-lethal level, when action can be taken to mitigate a/biotic impacts.

Modulation of oxidative damage by lipopolysaccharides and antioxidant responses in the freshwater crab Sinopotamon henanense Bott 1967 (Decapoda: Brachyura: Potamonidae) during cadmium exposure

AbstractCadmium (Cd) is a toxic pollutant that exerts adverse effects on organisms. We examined oxidative damage and antioxidative parameters in hemocytes of the freshwater crab Sinopotamon henanense Bott 1967 exposed to sublethal levels of Cd for 21 d. We also examined the immunomodulation of lipopolysaccharides (LPS) on oxidation caused by Cd in the crab. Cd induced higher reactive oxygen species (ROS) levels but ROS production in crab hemocytes was down-regulated after LPS injection. The contents of malondialdehyde (MDA) and protein carbonyl derivatives (PCO), DNA-protein crosslinks (DPCs) coefficient in the hemocytes of crabs exposed to Cd increased. LPS injection could decrease these oxidative parameters. The total antioxidant capacity (T-AOC) was significantly inhibited by Cd and LPS enhanced the activity of T-AOC in crab hemocytes. Cd treatment also up-regulated activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Only CAT activity decreased when crabs were exposed to Cd followed by LPS stimulation. Peroxidase (POD) activities showed little change after Cd or LPS treatments. The oxidative damage caused by Cd exposure may be reduced by LPS, suggesting its possible use in aquaculture as an immunostimulant for crustaceans.

Reporting from outside the lab: attending the ASH conference

Postgraduate, Early Career, Full and Emeritus Members of the Biochemical Society can apply for a General Travel Grant. These grants support attendance at scientific meetings, training courses, lab visits or any other event relevant to your career and encourage lifelong learning. James Hillier is currently investigating the role of the aminotransferase BCAT1 in acute myeloid leukaemia (AML) development. BCAT1 contains a CXXC motif, a feature of many antioxidant enzymes such as thioredoxin that are able to metabolize reactive oxygen species (ROS). His research focuses how altered expression of BCAT1 affects redox homeostasis and how this impacts processes dysregulated in cancer such as proliferation, differentiation and apoptosis. Cancer cells are known to favour pro-oxidative states that induce proliferative signalling yet maintain ROS at sub-lethal levels, therefore targeting the antioxidant capacity of BCAT1 to induce cell death, which may open a promising treatment option for patients with aberrant BCAT1 expression.