Relationship between glutathione S-transferase, catalase, oxygen consumption, lipid peroxidation and oxidative stress in eggs and larvae of Boophilus microplus (Acarina: Ixodidae)

High toxicity of agro-industrial wastewater on aquatic fauna of a South American stream: Mortality of aquatic turtles and amphibian tadpoles as bioindicators of environmental health

The aim of this study was to characterize an aquatic system of Santa Fe province (Argentina) receiving wastewater from agro-industrial activities (mainly dairy) by in situ assessment (fauna mortality, physicochemical, microbiological, and pesticide residues measurement), and ecotoxicity bioassays on amphibian tadpoles. Water and sediment samples were obtained from the Los Troncos Stream (LTS), previous to the confluence with the "San Carlos" drainage channel (SCC), and from the SCC. Biological parameters (mortality and sublethal biomarkers) were used to evaluate ecotoxicity during 10-day exposure of Rhinella arenarum tadpoles to LTS and SCC samples. Nine pesticides were detected in both LTS and SCC. Chemical and biochemical oxygen demand, ammonia, and coliform count recorded in SCC greatly exceeded limits for aquatic life protection. At SCC and LTS after the confluence with SCC, numerous dying and dead aquatic turtles (Phrynops hilarii) were recorded. In the ecotoxicity assessment, no mortality of tadpoles was observed in LTS treatment, whereas total mortality (100%) was observed in SCC treatments in dilution higher than 50% of water and sediment. For SCC, median lethal concentration and the 95% confidence limits was 18.30% (14.71-22.77) at 24 h; lowest-observed and no-observed effect concentrations were 12.5% and 6.25%, respectively. Oxidative stress and neurotoxicity were observed in tadpoles exposed to 25% SCC dilution treatment. In addition, there was a large genotoxic effect (micronuclei test) in all sublethal SCC dilution treatments (6.25%, 12.5%, and 25%). These results alert about the high environmental quality deterioration and high ecotoxicity for aquatic fauna of aquatic ecosystems affected by agro-industrial wastewater. PRACTITIONER POINTS: Great mortality of turtles was observed in a basin with a high load of agro-industrial wastewater. San Carlos Channel (SCC), where effluents are spilled, is environmentally deteriorated. The water-sediment matrix of SCC caused 100% lethality in tadpoles. SCC dilutions caused neurotoxicity, oxidative stress, and genotoxicity on tadpoles.

A longitudinal transcriptomic analysis of Rhipicephalus microplus midgut upon feeding

Rhipicephalus microplus, a highly host-specific tick that primarily feeds on cattle, posing a significant threat to livestock production. The investigation of tick physiology is crucial for identifying potential targets in tick control. Of particular interest adult female ticks undergo a significant expansion of the midgut during feeding, leading to an over 100-fold increase in body weight. Beyond the functions of storing and digesting blood meals, the tick midgut plays a crucial role in acquiring and transmitting pathogens. However, our understanding of tick midgut physiology remains limited. In this study we conducted a comprehensive longitudinal transcriptome analysis of the midgut from adult female R. microplus ticks collected at various feeding stages, providing an overview of the transcriptional modulation in this organ as feeding progress. By employing a de novo assembly approach followed by coding-sequences (CDS) extraction, 60,599 potential CDS were identified. In preparation for functional annotation and differential expression analysis, transcripts that showed an average transcript per million (TPM) ≥ 3 in at least one of the biological conditions were extracted. This selection process resulted in a total of 10,994 CDS, which were categorized into 24 functional classes. Notably, our differential expression analysis revealed three main transcriptional profiles. In the first one, representing the slow-feeding stage, the most abundant functional classes were the "protein synthesis" and "secreted" groups, reflecting the highly active state of the tick midgut. The second profile partially accounts for the rapid-feeding stage, in which a high number of differentially expressed transcripts was observed. Lastly, the third transcriptional profile represents post-detached ticks. Notably the highest number of modulated transcripts was observed up to 48 h post-detachment (hpd), however no major differences was observed up to 168 hpd. Overall, the data presented here offers a temporal insight into tick midgut physiology, contributing to the identification of potential targets for the development of anti-tick control strategies.

The role of P450 enzymes in malaria and other vector-borne infectious diseases

Vector-borne infectious diseases are still an important global health problem. Malaria is the most important among them, mainly pediatric, life-threatening disease. Malaria and other vector-borne disorders caused by parasites, bacteria, and viruses have a strong impact on public health and significant economic costs. Most vector-borne diseases could be prevented by vector control, with attention to the ecological and biodiversity conservation aspects. Chemical control with pesticides and insecticides is widely used as a measure of prevention although increasing resistance to insecticides is a serious issue in vector control. Metabolic resistance is the most common mechanism and poses a big challenge. Insect enzyme systems, including monooxygenase CYP P450 enzymes, are employed by vectors mainly to metabolize insecticides thus causing resistance. The discovery and application of natural specific inhibitors/blockers of vector P450 enzymes as synergists for commonly used pesticides will contribute to the "greening" of insecticides. Besides vector CYPs, host CYP enzymes could also be exploited to fight against vector-borne diseases: using mostly their detoxifying properties and involvement in the immune response. Here, we review published research data on P450 enzymes from all players in vector-borne infections, that is, pathogens, vectors, and hosts, regarding the potential role of CYPs in disease. We discuss strategies on how to exploit cytochromes P450 in vector-borne disease control.

In Silico Exploration and Experimental Validation of Camellia sinensis Extract against Rhipicephalus microplus and Sarcoptes scabiei: An Integrated Approach

Sarcoptes scabiei is an ectoparasite of humans and animals that causes scabies. The Rhipicephalus (Boophilus) microplus is a blood-sucking ectoparasite that transmits various pathogens. These two parasites have caused great losses to a country's dairy and agriculture sectors. The aim of this study was to determine the in vitro and in silico efficacy of Camellia sinensis plant extracts. Different concentrations of C. sinensis ethanolic plant extracts were prepared using the maceration method and were used against mites and ticks (in adult immersion test AIT and larval packet test LPT) to evaluate their in vitro acaricidal activity. Additionally, in silico molecular docking was performed to investigate the inhibitory interactions between the phytochemicals of the plant and S. scabiei and R. microplus glutathione transferase proteins (SsGST and RmGST). This study observed that the plant extract showed high efficacy in vitro against mites and different tick stages in adult immersion and larval packet tests. Additionally, the in silico study revealed a strong binding interaction between ellagic acid and SsGST protein, with a binding energy of -7.3 kcal/mol, with respect to permethrin (-6.7 kcal/mol), whereas quercetin and RmGST resulted in a docking score of -8.6 kcal/mol compared to deltamethrin (-8.2 kcal/mol). Overall, this study explored the potential of C. sinensis as a natural alternative for controlling tick and mite infestations and provided insights into the inhibitory mechanisms of its phytochemicals.

Purification, characterization, and enzyme kinetics of a glutathione S transferase from larvae of the camel tick Hyalomma dromedarii

BACKGROUND

Glutathione s-transferases (GSTs) perform an essential role in detoxification of xenobiotics and endogenous compounds via their conjugation to reduce glutathione.

RESULTS

A GST enzyme, designated tick larvae glutathione S transferase (TLGST), was purified from larvae of the camel tick Hyalomma dromedarii via ammonium sulfate precipitation, glutathione-Sepharose affinity column and Sephacryl S-300 chromatography. TLGST-specific activity was found to be 1.56 Umg^-1 which represents 39 folds and 32.2% recovery. The molecular weight of TLGST purified from camel tick larvae was found as 42 kDa by gel filtration. TLGST has a pI value of 6.9 and was found a heterodimeric protein of 28 and 14 kDa subunits as detected on SDS-PAGE. The Lineweaver-Burk plot calculated the km for CDNB to be 0.43 mM with Vmax value of 9.2 Umg^-1. TLGST exhibited its optimal activity at pH 7.9. Co²⁺, Ni²⁺ and Mn²⁺ increased the activity of TLGST while Ca²⁺, Cu²⁺, Fe²⁺ and Zn²⁺ inhibited it. TLGST was inhibited by cumene hydroperoxide, p-hydroxymercuribenzoate, lithocholic acid, hematin, triphenyltin chloride, p-chloromercuribenzoic acid (pCMB), N-p-Tosyl-L-phenylalanine chloromethyl ketone (TPCK), iodoacetamide, EDTA and quercetin. pCMB inhibited TLGST competitively with Ki value of 0.3 mM.

CONCLUSIONS

These findings will help to understand the various physiologic conditions of ticks and targeting TLGST could be significant tool for development of prospective vaccines against ticks as a bio-control strategy to overcome the rapid grows in pesticide-resistant tick populations.

Ixodicidal effect of extracts from Cordia boissieri, Artemisia ludoviciana and Litchi chinensis on Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

The ixodicidal activity of the methanolic extracts of Artemisia ludoviciana (Astereceae), Cordia boissieri (Boraginaceae) and Litchi chinensis (Sapindaceae) against two field populations of Rhipicephalus (Boophilus) microplus from the state of Nuevo Leon (NL) and Veracruz (VER) was evaluated. The extract of L. chinensis in the concentration of 150 mg/ml showed efficacies of 100% and 99% against engorged females and mortalities of 98% and 99% against larvae. C. boissieri in the same concentration showed efficacies of 71% and 37% against engorged adults and mortalities of 33.04% and 10.33% against larvae and A. ludoviciana had efficacies of 94% and 83% in adults and mortalities of 89.39% and 89.21% against larvae in both populations respectively. The enzymatic activity of Acetylcholinesterase (AChE), Carboxylesterase (CaE), Glutathione-S-Transferase (GST) and Alkaline Phosphatase (ALP) was measured in both populations of ticks. As a result, a significant difference between both populations was shown, being the VER population the one that exhibited a higher enzymatic activity (p ≤ 0.05). It can be concluded that the methanolic extract of the seed of L. chinensis shows potential ixodicidal activity and can be used as an alternative source of tick control, however, prior characterization, toxicity and formulation studies are necessary.

Adverse Effects of Toxic Metal Pollution in Rivers on the Physiological Health of Fish

Toxic metal pollution influences the lives of diverse aquatic organisms and humans who consume contaminated aquatic products. However, its potential impacts on aquatic organism health and, thus, ecological health, have been neglected in many regions. This research was carried out to contribute to filling that knowledge gap. Three freshwater fish species in the Nhue−Day River basin, Vietnam, have been chosen to study the bioaccumulation of metals (Zn, Cu, Pb, and Cd) in the tissues (livers, kidneys, gills) and their effects on fish physiological health (changes in the oxidative-GST activity, and physiological biomarkers-energy reserves, respectively) from 2013 to 2017. The extensive results revealed significant spatial and temporal variations in metal concentrations in tissues of common carp (Cyprinus carpio), silver carp (Hypothalmic molitrix), and tilapia (Oreochromis niloticus), and well correlated to their concentration in the water (p < 0.05). Fish bioaccumulated metals in the following order: Zn > Cu > Pb > Cd, with more in the kidneys and livers (spring and summer) than in other tissues. Metal accumulation in O. niloticus and C. carpio was higher than in H. molitrix. Biomarker responses (except for glycogen variation) were also higher during warm seasons. Changes in metal levels in water and fish tissues caused variations in biomarkers in the respective fish tissues, particularly in the livers, as demonstrated by significant correlations of metal concentrations in water and fish tissues to biochemical and physiological responses (p < 0.05). The findings suggest that metal pollution in the river basin adversely impacts the physiological health of both wild and cultured fish. Seasonal shifts in the levels of metal accumulation and biomarkers could be connected to species-specific differences in physiology and the levels of metals in environments. This biomarker set is simple but effective in assessing the impact of metal pollution on fish health and, hence, the aquatic ecosystem. This is one of the first biomonitoring studies to assist in designing better water management strategies for the Nhue−Day River basin.

Molecular targets for the development of new acaricides against Rhipicephalus microplus: a review

The cattle tick Rhipicephalus microplus is an ectoparasite with high economic importance to bovine culture, mainly in tropical and subtropical regions. The resistance of the tick from the commercial acaricides has hindered its control, thus motivating the search for new strategies. The purpose of this study was to perform a critical review about the main molecular targets of R. microplus that are useful for the discovery of new acaricides. Bibliographic search was conducted in the databases PubMed, ScienceDirect and CAB Direct, using the following descriptors: ‘Rhipicephalus microplus’, ‘Boophilus microplus’, ‘molecular targets’ and ‘action’, published between 2010 and 2021. Out of the 212 publications identified, 17 articles were selected for study inclusion. This review described 14 molecular targets and among these 4 are targets from commercial acaricides. Most of them are enzymes to catalyse important reactions to tick survival, related to energetic metabolism, mechanisms of biotransformation and neurotransmission. The data will be helpful in the development of new more effective and selective acaricides.

Ambivalent Roles of Oxidative Stress in Triangular Relationships among Arthropod Vectors, Pathogens and Hosts

Blood-feeding arthropods, particularly ticks and mosquitoes are considered the most important vectors of arthropod-borne diseases affecting humans and animals. While feeding on blood meals, arthropods are exposed to high levels of reactive oxygen species (ROS) since heme and other blood components can induce oxidative stress. Different ROS have important roles in interactions among the pathogens, vectors, and hosts. ROS influence various metabolic processes of the arthropods and some have detrimental effects. In this review, we investigate the various roles of ROS in these arthropods, including their innate immunity and the homeostasis of their microbiomes, that is, how ROS are utilized to maintain the balance between the natural microbiota and potential pathogens. We elucidate the mechanism of how ROS are utilized to fight off invading pathogens and how the arthropod-borne pathogens use the arthropods’ antioxidant mechanism to defend against these ROS attacks and their possible impact on their vector potentials or their ability to acquire and transmit pathogens. In addition, we describe the possible roles of ROS in chemical insecticide/acaricide activity and/or in the development of resistance. Overall, this underscores the importance of the antioxidant system as a potential target for the control of arthropod and arthropod-borne pathogens.

Protein profiling of hemolymph in Haemaphysalis flava ticks

Background

Tick hemolymph bathes internal organs, acts as an exchange medium for nutrients and cellular metabolites, and offers protection against pathogens. Hemolymph is abundant in proteins. However, there has been limited integrated protein analysis in tick hemolymph thus far. Moreover, there are difficulties in differentiating tick-derived proteins from the host source. The aim of this study was to profile the tick/host protein components in the hemolymph of Haemaphysalis flava.

Methods

Hemolymph from adult engorged H. flava females was collected by leg amputation from the Erinaceus europaeus host. Hemolymph proteins were extracted by a filter-aided sample preparation protocol, digested by trypsin, and assayed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). MS raw data were searched against the UniProt Erinaceidae database and H. flava protein database for host- and tick-derived protein identification. Protein abundance was further quantified by intensity-based absolute quantification (iBAQ).

Results

Proteins extracted from hemolymph unevenly varied in size with intense bands between 100 and 130 kDa. In total, 312 proteins were identified in the present study. Therein 40 proteins were identified to be host-derived proteins, of which 18 were high-confidence proteins. Top 10 abundant host-derived proteins included hemoglobin subunit-α and subunit-β, albumin, serotransferrin-like, ubiquitin-like, haptoglobin, α-1-antitrypsin-like protein, histone H2B, apolipoprotein A-I, and C3-β. In contrast, 169 were high-confidence tick-derived proteins. These proteins were classified into six categories based on reported functions in ticks, i.e., enzymes, enzyme inhibitors, transporters, immune-related proteins, muscle proteins, and heat shock proteins. The abundance of Vg, microplusin and α-2-macroglobulin was the highest among tick-derived proteins as indicated by iBAQ.

Conclusions

Numerous tick- and host-derived proteins were identified in hemolymph. The protein profile of H. flava hemolymph revealed a sophisticated protein system in the physiological processes of anticoagulation, digestion of blood meal, and innate immunity. More investigations are needed to characterize tick-derived proteins in hemolymph.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05287-7.

Can Wolf Spider Mothers Detect Insecticides in the Environment? Does the Silk of the Egg-Sac Protect Juveniles from Insecticides?

The use of pesticides for plague control in agroecosystems generates a threat to wildlife and a major problem for human health. Pesticide compounds are also an important source of water and atmosphere contamination. Although insecticides are effective on their target organisms, they often affect organisms that are not their target. The aim of the present study was to research the effects of 3 types of neurotoxic insecticides-a pyrethroid (cypermethrin), a neonicotinoid (imidacloprid), and an organophosphate (chlorpyrifos)-on behavioral and physiological parameters of Pardosa saltans spider (Lycosidae). Our study analyzed for the first time the exploratory behavior of the spider mothers in the presence of these 3 insecticides on their egg-sacs and also on the ground. We also evaluated the oxidative stress effects on the juveniles hatched in the egg-sac protected by silk in relation to variations in detoxification enzymes (catalase, glutathione reductase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase) and lipid peroxidation (reactive oxygen species [ROS]). The results show that these insecticides are repellents for mothers (cypermethrin is the most repellent), and maternal behavior is modified after detection of an insecticide on their egg-sac but mothers do not abandon their egg-sacs. These neurotoxic insecticides affect the juveniles inside their egg-sac. Cypermethrin and chlorpyrifos caused more oxidative stress in juveniles than did imidacloprid. The ROS generated by these insecticides seemed to be adequately eliminated by the juveniles' antioxidant systems. Environ Toxicol Chem 2021;40:2861-2873. © 2021 SETAC.

Acaricidal activity of the essential oil from Senecio cannabifolius and its constituents eucalyptol and camphor on engorged females and larvae of Rhipicephalus microplus (Acari: Ixodidae)

The objective of this experiment was to evaluate the acaricidal activity of Senecio cannabifolius essential oil, and two of its constituents, eucalyptol and camphor. Efficacy against females and larvae of Rhipicephalus (Boophilus) microplus was assessed by the adult immersion test (AIT) and the larval immersion test (LIT). The oil was analyzed by gas chromatography-flame ionization detection (GC-FID) and GC-mass spectrometry (MS) and in total 68 components were identified representing 99.2% of the essential oil. AIT revealed that the oil, eucalyptol, and camphor at the highest concentration presented efficacy of 68.9, 57.1, and 71.9%, respectively. LIT revealed that the essential oil and camphor achieved 100% mortality at concentration of 1.6% wt/vol, whereas eucalyptol showed moderate inhibitory activity. Biochemical assays indicated that the essential oil and camphor can reduce significantly overall detoxification enzyme activities in engorged females and larvae at high concentration (≥ 0.4% wt/vol), whereas the inhibitory effect of eucalyptol is weaker than that of the oil and camphor. Taken together our results indicated that the S. cannabifolius essential oil and its isolated constituent had potential for the development of a new and safe acaricide for the control of R. microplus ticks.

An Ixodes scapularis glutathione S-transferase plays a role in cell survival and viability during Langat virus infection of a tick cell line

Ticks are important vectors of diseases affecting both humans and animals. To be an efficient vector, ticks have to survive infection by pathogens such as the Langat virus (LGTV). One method utilized by ticks is their complex antioxidant mechanism. Included in the vast antioxidant processes are several enzymes involved in redox homeostasis. The ubiquitous glutathione S-transferases (GSTs) belong to the antioxidant family of enzymes. In this study, we evaluated the role of a GST during LGTV infection. ISE6 cells were infected with LGTV with a multiplicity of infection (MOI) of 0.01 and observed daily. The infection success was monitored via indirect immunofluorescent antibody test (IFAT) for LGTV for up to 4 days. The gene expression of IsGST1 was determined by real-time polymerase chain reaction (PCR) using IsGST1 gene-specific primers. Knockdown of the IsGST1 gene with subsequent LGTV infection was also performed. Afterward, ISE6 cell mortality and viability were checked daily until the fourth day. The virus titer from supernatants of IsGST1-knockdown cells was quantified using a focus-formation assay. IFAT data showed that LGTV infects ISE6 cells in a time-dependent manner with increasing infection from day 0 to day 4. The IsGST1 genes showed an increasing expression until day 2 of infection, while decreased expression was observed from day 3 to day 4 post-infection. Knockdown of the IsGST1 resulted in increased mortality on the third day of infection, while the cell viability was also negatively affected by the knockdown of the IsGST1 genes from day 0 to day 4 post-infection. Knockdown of the IsGST1 genes also resulted in a decreased viral titer from the supernatants of the ISE6 cells infected with LGTV. Based on the results, GSTs are possibly utilized both by cells and the virus for mutual survival and proliferation.

An insight into the functional role of antioxidant and detoxification enzymes in adult Rhipicephalus microplus female ticks

Ticks have developed physiological adaptations to transport, store, metabolize and secrete toxic components from the diet and environment. Different classes of enzymes are involved in these processes, however, the role of several of them is not yet characterized in Rhipicephalus microplus. In this context, this work investigated the action of antioxidant and detoxification enzymes, as well as the levels of essential cellular reductants in R. microplus partially engorged females (PEF) and fully engorged females (FEF). Results demonstrated that enzymes transcriptional levels and enzymatic activity from ovary and fat body were higher in PEF than in FEF, except for ovary Glutathione peroxidase (GPx), which was the only enzyme showing highest activity in the FEF stage. These results indicated a higher demand for antioxidant potential in these organs at the initial feeding phase than during egg-laying. In midgut, however, there was more variability in the transcriptional levels and activity of the different enzymes between the PEF and FEF phases. Similar NADPH levels were found in PEF and FEF phases, suggesting a remarkable capacity to maintain a regular supply of reducing power, despite the developmental changes and large intake of heme and iron. However, reduced glutathione (GSH) levels were variable between PEF and FEF when distinct organs were compared. Taken together, our data suggest a higher demand for reducing potential in FEF ticks. The silencing of catalase (CAT) or thioredoxin reductase (TRx) genes in females did not impair feeding, egg-laying capacity, or larvae hatching. CAT-silenced ticks had increased ovary peroxidase activity, a possible compensatory antioxidant mechanism. Altogether, the results shed light on the complexity of the antioxidant and detoxification enzyme system in ticks and its involvement in different physiological mechanisms.

Expression analysis of glutathione S-transferases and ferritins during the embryogenesis of the tick Haemaphysalis longicornis

In the tick life cycle, embryogenesis is the only stage of development wherein no blood meal is required. Nevertheless, even in the absence of a blood meal, which is the source of nutrients as well as the ferrous iron and heme that could cause oxidative stress in ticks, malondialdehyde (MDA) has been reported to increase during this period. Additionally, the knockdown of some oxidative stress-related molecules such as ferritin has resulted in abnormal eggs and embryonic death. Here, we investigate the gene and protein expression profiles of the identified glutathione S-transferases (GSTs) and ferritins (Fers) of the tick H. longicornis during embryogenesis through quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blotting, respectively. We also confirm the lipid peroxidation and ferrous iron concentration level using a thiobarbituric acid reactive substances (TBARS) assay. Finally, we attempt to correlate these findings with the events occurring by establishing a staging process in H. longicornis embryos. Lipid peroxidation increased during the course of embryogenesis, as does the amount of GST proteins. On the other hand, the GST genes have high expression at the 1st day post-oviposition, during the early stage of embryogenesis and at day 10 during the period wherein the germ band is observable. Fer gene expression also starts to increase at day 10 and peaks at day 15. In the ferritin proteins, only the secretory ferritin (Fer2) is detected and constitutively expressed during embryogenesis. Events occurring during embryogenesis, such as energy production and iron metabolism for cellular proliferation and differentiation cause oxidative stress in the embryo. To counteract oxidative stress, it is possible that the embryo may utilize oxidative stress-related molecules such as GSTs and Fer2, which could be either maternally or embryo-derived.

The case for oxidative stress molecule involvement in the tick-pathogen interactions -an omics approach

The blood-feeding behavior of ticks has resulted in them becoming one of the most important vectors of disease-causing pathogens. Ticks possess a well-developed innate immune system to counter invading pathogens. However, the coevolution of ticks with tick-borne pathogens has adapted these pathogens to the tick's physiology and immune response through several mechanisms including transcriptional regulation. The recent development in tick and tick-borne disease research greatly involved the "omics" approach. The omics approach takes a look en masse at the different genes, proteins, metabolomes, and the microbiome of the ticks that could be differentiated during pathogen infection. Data from this approach revealed that oxidative stress-related molecules in ticks are differentiated and possibly being exploited by the pathogens to evade the tick's immune response. In this study, we review and discuss transcriptomic and proteomic data for some oxidative stress molecules differentially expressed during pathogen infection. We also discuss metabolomics and microbiome data as well as functional genomics in order to provide insight into the tick-pathogen interaction.

Carbohydrate Metabolic Compensation Coupled to High Tolerance to Oxidative Stress in Ticks

Reactive oxygen species (ROS) are natural byproducts of metabolism that have toxic effects well documented in mammals. In hematophagous arthropods, however, these processes are not largely understood. Here, we describe that Rhipicephalus microplus ticks and embryonic cell line (BME26) employ an adaptive metabolic compensation mechanism that confers tolerance to hydrogen peroxide (H2O2) at concentrations too high for others organisms. Tick survival and reproduction are not affected by H2O2 exposure, while BME26 cells morphology was only mildly altered by the treatment. Furthermore, H2O2-tolerant BME26 cells maintained their proliferative capacity unchanged. We evaluated several genes involved in gluconeogenesis, glycolysis, and pentose phosphate pathway, major pathways for carbohydrate catabolism and anabolism, describing a metabolic mechanism that explains such tolerance. Genetic and catalytic control of the genes and enzymes associated with these pathways are modulated by glucose uptake and energy resource availability. Transient increase in ROS levels, oxygen consumption, and ROS-scavenger enzymes, as well as decreased mitochondrial superoxide levels, were indicative of cell adaptation to high H2O2 exposure, and suggested a tolerance strategy developed by BME26 cells to cope with oxidative stress. Moreover, NADPH levels increased upon H2O2 challenge, and this phenomenon was sustained mainly by G6PDH activity. Interestingly, G6PDH knockdown in BME26 cells did not impair H2O2 tolerance, but generated an increase in NADP-ICDH transcription. In agreement with the hypothesis of a compensatory NADPH production in these cells, NADP-ICDH knockdown increased G6PDH relative transcript level. The present study unveils the first metabolic evidence of an adaptive mechanism to cope with high H2O2 exposure and maintain redox balance in ticks.

Characterization and expression analysis of a newly identified glutathione S-transferase of the hard tick Haemaphysalis longicornis during blood-feeding

Background

Ticks are obligate hematophagous parasites important economically and to health. Ticks consume large amounts of blood for their survival and reproduction; however, large amounts of iron in blood could lead to oxidative stress. Ticks use several molecules such as glutathione S-transferases (GSTs), ferritins, and peroxiredoxins to cope with oxidative stress. This study aimed to identify and characterize the GSTs of the hard tick Haemaphysalis longicornis in order to determine if they have a role in coping with oxidative stress.

Methods

Genes encoding GSTs of H. longicornis were isolated from the midgut CDNA library. Genes have been cloned and recombinant GSTs have been expressed. The enzymatic activities, enzyme kinetic constants, and optimal pH of the recombinant GSTs toward 1-chloro-2,4-dinitrobenzene (CDNB) were determined. The gene transcription and protein expression profiles were determined in the whole ticks and internal organs, and developmental stages using real time RT-PCR and Western blotting during blood feeding. The localization of GST proteins in organs was also observed using immunofluorescent antibody test (IFAT).

Results

We have isolated two genes encoding GSTs (HlGST and HlGST2). The enzymatic activity toward CDNB is 9.75 ± 3.04 units/mg protein for recombinant HlGST and 11.63 ± 4.08 units/mg protein for recombinant HlGST2. Kinetic analysis of recombinant HlGST showed K_m values of 0.82 ± 0.14 mM and 0.64 ± 0.32 mM for the function of CDNB and GSH, respectively. Meanwhile, recombinant HlGST2 has K_m values of 0.61 ± 0.20 mM and 0.53 ± 0.02 mM for the function of CDNB and GSH, respectively. The optimum pH of recombinant HlGST and recombinant HlGST2 activity was 7.5–8.0. Transcription of both GSTs increases in different developmental stages and organs during blood-feeding. GST proteins are upregulated during blood-feeding but decreased upon engorgement in whole ticks and in some organs, such as the midgut and hemocytes. Interestingly, salivary glands, ovaries, and fat bodies showed decreasing protein expression during blood-feeding to engorgement. Varying localization of GSTs in the midgut, salivary glands, fat bodies, ovaries, and hemocytes was observed depending on the feeding state, especially in the midgut and salivary glands.

Conclusions

In summary, a novel GST of H. longicornis has been identified. Characterization of the GSTs showed that GSTs have positive correlation with the degree and localization of oxidative stress during blood-feeding. This could indicate their protective role during oxidative stress.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2667-1) contains supplementary material, which is available to authorized users.

Ironing out the Details: Exploring the Role of Iron and Heme in Blood-Sucking Arthropods

Heme and iron are essential molecules for many physiological processes and yet have the ability to cause oxidative damage such as lipid peroxidation, protein degradation, and ultimately cell death if not controlled. Blood-sucking arthropods have evolved diverse methods to protect themselves against iron/heme-related damage, as the act of bloodfeeding itself is high risk, high reward process. Protective mechanisms in medically important arthropods include the midgut peritrophic matrix in mosquitoes, heme aggregation into the crystalline structure hemozoin in kissing bugs and hemosomes in ticks. Once heme and iron pass these protective mechanisms they are presumed to enter the midgut epithelial cells via membrane-bound transporters, though relatively few iron or heme transporters have been identified in bloodsucking arthropods. Upon iron entry into midgut epithelial cells, ferritin serves as the universal storage protein and transport for dietary iron in many organisms including arthropods. In addition to its role as a nutrient, heme is also an important signaling molecule in the midgut epithelial cells for many physiological processes including vitellogenesis. This review article will summarize recent advancements in heme/iron uptake, detoxification and exportation in bloodfeeding arthropods. While initial strides have been made at ironing out the role of dietary iron and heme in arthropods, much still remains to be discovered as these molecules may serve as novel targets for the control of many arthropod pests.

Mesoporous silica nanoparticles SBA-15 loaded with emodin upregulate the antioxidative defense of Euproctis chrysorrhoea (L.) larvae

The study presented here aims to elucidate the effects of emodin (EO = 1,3,8-trihydroxy-6-methylanthraquinone) in its free form and when loaded into a mesoporous silica nanocarrier SBA-15 (→ SBA-15|EO) on the activities of the main antioxidative enzymes, superoxide dismutase, catalase, glutathione S-transferase, and glutathione reductase, in larvae of a polyphagous insect pest, the browntail moth Euproctis chrysorrhoea (L.). The results show that only SBA-15|EO upregulates the activities of the tested antioxidative enzymes. These results point to significant differences in the effectiveness of the compound in the free versus the loaded form.

Activity of carboxylesterases, glutathione-S-transferase and monooxygenase on Rhipicephalus microplus exposed to fluazuron

The objective of this study was to assess the effect of the exposure to fluazuron on the activity of common pesticide detoxification enzyme groups in the cattle tick (Rhipicephalus microplus). Engorged females of a susceptible strain (POA) and a resistant strain (Jaguar) were exposed in vitro to fluazuron and their eggs and larvae were used to compare the activities of the general esterases, mixed-function oxidases (MFO) and glutathione-S-transferase (GST). The results showed significant elevation in MFO contents and esterases activity in the resistant strain when compared with the susceptible strain, in eggs and larvae respectively. In the POA strain, the MFO activity in eggs was down-regulated by fluazuron exposure. Based on these results, it can be concluded that different detoxification enzymes can act in distinct pathways depending on the tick's development stage, and may be related to fluazuron detoxification in resistant strains.

Multibiomarker toxicity characterization of uranium mine drainages to the fish Carassius auratus

The release of acidic effluents, naturally enriched in metals and radionuclides, is the main legacy of uranium mines. Generally, metals dissolved by these acidic effluents can cause significant alterations in exposed organisms, with distinct toxicological outcomes. In this study, 72 individuals of the freshwater fish species Carassius auratus were exposed in situ for different periods (8, 16, 24, and 48 h) to water from a pond (treatment pond (TP)) with a chemically treated effluent and a reference pond (PRP), in the vicinity of the Cunha Baixa uranium mine (Portugal). Comparing the water of the two ponds, the PRP pond was characterized by higher pH and oxygen values and lower conductivity and hardness values. Regarding total metal concentrations, among others, magnesium (56,000 μg/L), sodium (17,400 μg/L), zinc (86 μg/L), manganese (6340 μg/L), and uranium (1380 μg/L) concentrations in the TP pond were above the values obtained for the PRP pond. The values of manganese and uranium exceeded the values of quality criteria established for surface waters for cyprinids and for irrigation purposes. After exposure to pond water, significant differences were recorded for several biomarkers: (i) between ponds for acetylcholinesterase (AChE) with higher activities for animals from the PRP and glutathione-S-transferase (GST) activities that were particularly enhanced in animals from the TP pond; (ii) between ponds and exposure periods for lactate dehydrogenase (LDH) activity, since organisms from PRP pond presented always higher values than those from the TP pond, and among these, organisms exposed for the longer period presented a further depression in LDH activity; and (iii) between exposure periods for erythrocyte micronucleus. GSTs and LDH were the most sensitive biomarkers within the timeframe of the in situ assay performed. Despite the alleged efficacy of the chemical treatment (evidenced by a significantly lower pH), some metals persisted in the treated effluent (TP pond), potentially contributing to the induction of oxidative stress or increased conjugation metabolic activity in fish.

Influence of non-steroidal anti-inflammatory drugs on Drosophila melanogaster longevity

Most age-related diseases and aging itself are associated with chronic inflammation. Thus pharmacological inhibition of inflammatory processes may be effective antiaging strategy. In this study we demonstrated that treatment of Drosophila melanogaster with 10 non-steroidal anti-inflammatory drugs (NSAIDs: CAY10404, aspirin, APHS, SC-560, NS-398, SC-58125, valeroyl salicylate, trans-resveratrol, valdecoxib, licofelone) leads to extension of lifespan, delays age-dependent decline of locomotor activity and increases stress resistance. The effect of the lifespan increase was associated with decrease of fecundity. Depending on the concentration, NSAIDs demonstrated both anti- and pro-oxidant properties in Drosophila tissues. However, we failed to identify clear correlation between antioxidant properties of NSAIDs and their pro-longevity effects. The lifespan extending effects of APHS, SC-58125, valeroyl salicylate, trans-resveratrol, valdecoxib, and licofelone were more pronounced in males, valdecoxib and aspirin - in females. We demonstrated that lifespan extension effect of NSAIDs was abolished in flies with defective genes involved in Pkh2-ypk1-lem3-tat2 pathway.

Catalase from larvae of the camel tick Hyalomma dromedarii

Catalase plays a major role in protecting cells against toxic reactive oxygen species. Here, Catalase was purified from larvae of the camel tick Hyalomma dromedarii and designated TLCAT. It was purified by ammonium sulfate precipitation and chromatography on DEAE-cellulose, Sephacryl S-300 and CM-cellulose columns. Gel filtration and SDS-PAGE of the purified TLCAT indicated that the protein has a native molecular weight of 120 kDa and is most likely a homodimer with a subunit of approximately 60 kDa. The Km value of TLCAT is 12 mM H2O2 and displayed its optimum activity at pH 7.2. CaCl2, MgCl2, MnCl2 and NiCl2 increased the activity of TLCAT, while FeCl2, CoCl2, CuCl2 and ZnCl2 inhibited the activity of TLCAT. Sodium azide inhibited TLCAT competitively with a Ki value of 0.28 mM. The presence of TLCAT in cells may play a role in protecting H. dromedarii ticks against oxidative damage. This finding will contribute to our understanding of the physiology of these ectoparasites and the development of untraditional methods to control them.

Saliva from nymph and adult females of Haemaphysalis longicornis: a proteomic study

BACKGROUND

Haemaphysalis longicornis is a major vector of Theileria spp., Anaplasma phagocytophilum, Babesia spp. and Coxiella burnetti in East Asian countries. All life stages of ixodid ticks have a destructive pool-feeding style in which they create a pool-feeding site by lacerating host tissue and secreting a variety of biologically active compounds that allows the tick to evade host responses, enabling the uptake of a blood meal. The identification and functional characterization of tick saliva proteins can be useful to elucidate the molecular mechanisms involved in tick development and to conceive new anti-tick control methods.

METHODS

H. longicornis tick saliva was collected from fully engorged nymphs and fully engorged adults induced by dopamine or pilocarpine, respectively. Saliva was digested with trypsin for LC-MS/MS sequencing and peptides were searched against tick and rabbit sequences.

RESULTS

A total of 275 proteins were identified, of which 135 were tick and 100 were rabbit proteins. Of the tick proteins, 30 proteins were identified exclusively in fully engorged nymph saliva, 74 in fully engorged adult females, and 31 were detected in both stages. The identified tick proteins include heme/iron metabolism-related proteins, oxidation/detoxification proteins, enzymes, proteinase inhibitors, tick-specific protein families, and cytoskeletal proteins. Proteins involved in signal transduction, transport and metabolism of carbohydrate, energy, nucleotide, amino acids and lipids were also detected. Of the rabbit proteins, 13 were present in nymph saliva, 48 in adult saliva, and 30 were present in both. The host proteins include immunoglobulins, complement system proteins, antimicrobial proteins, serum albumin, peroxiredoxin, serotransferrin, apolipoprotein, hemopexin, proteinase inhibitors, and hemoglobin/red blood cells-related products.

CONCLUSIONS

This study allows the identification of H. longicornis saliva proteins. In spontaneously detached tick saliva various proteins were identified, although results obtained with saliva of fully engorged ticks need to be carefully interpreted. However, it is interesting to note that proteins identified in this study were also described in other tick saliva proteomes using partially engorged tick saliva, including hemelipoprotein, proteases, protease inhibitors, proteins related to structural functions, transporter activity, metabolic processes, and others. In conclusion, these data can provide a deeper understanding to the biology of H. longicornis.

Identification of 24h Ixodes scapularis immunogenic tick saliva proteins

Ixodes scapularis is arguably the most medically important tick species in the United States. This tick transmits 5 of the 14 human tick-borne disease (TBD) agents in the USA: Borrelia burgdorferi, Anaplasma phagocytophilum, B. miyamotoi, Babesia microti, and Powassan virus disease. Except for the Powassan virus disease, I. scapularis-vectored TBD agents require more than 24h post attachment to be transmitted. This study describes identification of 24h immunogenic I. scapularis tick saliva proteins, which could provide opportunities to develop strategies to stop tick feeding before transmission of the majority of pathogens. A 24h fed female I. scapularis phage display cDNA expression library was biopanned using rabbit antibodies to 24h fed I. scapularis female tick saliva proteins, subjected to next generation sequencing, de novo assembly, and bioinformatic analyses. A total of 182 contigs were assembled, of which ∼19% (35/182) are novel and did not show identity to any known proteins in GenBank. The remaining ∼81% (147/182) of contigs were provisionally identified based on matches in GenBank including ∼18% (27/147) that matched protein sequences previously annotated as hypothetical and putative tick saliva proteins. Others include proteases and protease inhibitors (∼3%, 5/147), transporters and/or ligand binding proteins (∼6%, 9/147), immunogenic tick saliva housekeeping enzyme-like (17%, 25/147), ribosomal protein-like (∼31%, 46/147), and those classified as miscellaneous (∼24%, 35/147). Notable among the miscellaneous class include antimicrobial peptides (microplusin and ricinusin), myosin-like proteins that have been previously found in tick saliva, and heat shock tick saliva protein. Data in this study provides the foundation for in-depth analysis of I. scapularis feeding during the first 24h, before the majority of TBD agents can be transmitted.

Evaluation and comparison of the potential of two ferritins as anti-tick vaccines against Haemaphysalis longicornis

BACKGROUND

Tick control is an essential aspect of controlling the spread of tick-borne diseases affecting humans and animals, but it presently faces several challenges. Development of an anti-tick vaccine is aimed at designing cost-effective and environmentally friendly protection against ticks and tick-borne diseases as an alternative to the use of chemical acaricides. A single vaccine from the tick midgut protein Bm86 is currently available for field applications, but its efficacy is limited to only some tick species. Identification of candidate vaccine antigens that can affect multiple tick species is highly desirable. The hard tick Haemaphysalis longicornis has two kinds of the iron-binding protein ferritin (HlFER), an intracellular HlFER1 and a secretory HlFER2, and RNA interference experiments showed that these are physiologically important in blood feeding and reproduction and in protection against oxidative stress. Here we investigated the potential of targeting HlFERs for tick control by immunizing the host with recombinant HlFERs (rHlFER1 and rHlFER2).

METHODS

Rabbits were immunized with rHlFERs three times subcutaneously at two-week intervals. Antisera were collected before the first immunization and a week after each immunization to confirm the antigen-specific serum antibody titer by serum ELISA. Two weeks after the final immunization, the rabbits were challenged with tick infestation. After dropping, tick feeding and reproduction parameters were evaluated to determine vaccine efficacy. To demonstrate the effects of antibodies, oxidative stress was detected in the eggs and larvae.

RESULTS

The antibody titer of rHlFER-immunized rabbits greatly increased after the second immunization. Antibodies exhibited cross-reactivity with rHlFERs and reacted with tick native HlFERs in Western blot analysis. Significantly lower bodyweight was observed in the ticks infested from the rHlFER2-immunized rabbit compared to those from the control rabbit. Reduced oviposition and hatching rate were observed in both rHlFER-immunized groups. rHlFER2 showed a higher vaccine efficacy. The antibodies against rHlFERs were detected in the eggs, and higher levels of oxidative stress biomarkers in the eggs and larvae, of ticks from rHlFER vaccinated rabbits.

CONCLUSION

Collectively, these results showed that HlFER2 has a good potential as an anti-tick vaccine antigen that may affect multiple tick species.

A 24-48 h fed Amblyomma americanum tick saliva immuno-proteome

BACKGROUND

Multiple tick saliva proteins, the majority of which are unknown, confer tick resistance in repeatedly infested animals. The objective of this study was to identify the 24-48 h fed Amblyomma americanum tick saliva immuno-proteome. The 24-48 h tick-feeding phase is critical to tick parasitism as it precedes important events in tick biology, blood meal feeding and disease agent transmission. Fed male, 24 and 96 h fed female phage display cDNA expression libraries were biopanned using rabbit antibodies to 24 and 48 h fed A. americanum female tick saliva proteins. Biopanned immuno-cDNA libraries were subjected to next generation sequencing, de novo assembly, and bioinformatic analysis.

RESULTS

More than 800 transcripts that code for 24-48 h fed A. americanum immuno-proteins are described. Of the 895 immuno-proteins, 52% (464/895) were provisionally identified based on matches in GenBank. Of these, ~19% (86/464) show high level of identity to other tick hypothetical proteins, and the rest include putative proteases (serine, cysteine, leukotriene A-4 hydrolase, carboxypeptidases, and metalloproteases), protease inhibitors (serine and cysteine protease inhibitors, tick carboxypeptidase inhibitor), and transporters and/or ligand binding proteins (histamine binding/lipocalin, fatty acid binding, calreticulin, hemelipoprotein, IgG binding protein, ferritin, insulin-like growth factor binding proteins, and evasin). Others include enzymes (glutathione transferase, cytochrome oxidase, protein disulfide isomerase), ribosomal proteins, and those of miscellaneous functions (histamine release factor, selenoproteins, tetraspanin, defensin, heat shock proteins).

CONCLUSIONS

Data here demonstrate that A. americanum secretes a complex cocktail of immunogenic tick saliva proteins during the first 24-48 h of feeding. Of significance, previously validated immunogenic tick saliva proteins including AV422 protein, calreticulin, histamine release factor, histamine binding/lipocalins, selenoproteins, and paramyosin were identified in this screen, supporting the specificity of the approach in this study. While descriptive, this study opens opportunities for in-depth tick feeding physiology studies.

Knockdown of the Rhipicephalus microplus cytochrome c oxidase subunit III gene is associated with a failure of Anaplasma marginale transmission

Rhipicephalus microplus is an obligate hematophagous ectoparasite of cattle and an important biological vector of Anaplasma marginale in tropical and subtropical regions. The primary determinants for A. marginale transmission are infection of the tick gut, followed by infection of salivary glands. Transmission of A. marginale to cattle occurs via infected saliva delivered during tick feeding. Interference in colonization of either the tick gut or salivary glands can affect transmission of A. marginale to naïve animals. In this study, we used the tick embryonic cell line BME26 to identify genes that are modulated in response to A. marginale infection. Suppression-subtractive hybridization libraries (SSH) were constructed, and five up-regulated genes {glutathione S-transferase (GST), cytochrome c oxidase sub III (COXIII), dynein (DYN), synaptobrevin (SYN) and phosphatidylinositol-3,4,5-triphosphate 3-phosphatase (PHOS)} were selected as targets for functional in vivo genomic analysis. RNA interference (RNAi) was used to determine the effect of tick gene knockdown on A. marginale acquisition and transmission. Although RNAi consistently knocked down all individually examined tick genes in infected tick guts and salivary glands, only the group of ticks injected with dsCOXIII failed to transmit A. marginale to naïve calves. To our knowledge, this is the first report demonstrating that RNAi of a tick gene is associated with a failure of A. marginale transmission.

Inorganic polyphosphates regulate hexokinase activity and reactive oxygen species generation in mitochondria of Rhipicephalus (Boophilus) microplus embryo

The physiological roles of polyphosphates (poly P) recently found in arthropod mitochondria remain obscure. Here, the possible involvement of poly P with reactive oxygen species generation in mitochondria of Rhipicephalus microplus embryos was investigated. Mitochondrial hexokinase and scavenger antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione reductase were assayed during embryogenesis of R. microplus. The influence of poly P₃ and poly P₁₅ were analyzed during the period of higher enzymatic activity during embryogenesis. Both poly Ps inhibited hexokinase activity by up to 90% and, interestingly, the mitochondrial membrane exopolyphosphatase activity was stimulated by the hexokinase reaction product, glucose-6-phosphate. Poly P increased hydrogen peroxide generation in mitochondria in a situation where mitochondrial hexokinase is also active. The superoxide dismutase, catalase and glutathione reductase activities were higher during embryo cellularization, at the end of embryogenesis and during embryo segmentation, respectively. All of the enzymes were stimulated by poly P₃. However, superoxide dismutase was not affected by poly P₁₅, catalase activity was stimulated only at high concentrations and glutathione reductase was the only enzyme that was stimulated in the same way by both poly Ps. Altogether, our results indicate that inorganic polyphosphate and mitochondrial membrane exopolyphosphatase regulation can be correlated with the generation of reactive oxygen species in the mitochondria of R. microplus embryos.

Superoxide dismutases from larvae of the camel tick Hyalomma dromedarii

Three superoxide dismutases (EC 1.15.1.1) (TLSOD1, TLSOD2 and TLSOD3) were purified from larvae of the camel tick Hyalomma dromedarii by ammonium sulfate precipitation, ion exchange and gel filtration columns. SDS-PAGE revealed that the subunit molecular masses of the SODs are 40±2 kDa, 67±1.5 kDa and 45±2.6 kDa for TLSOD1, TLSOD2 and TLSOD3, respectively. TLSOD1 and TLSOD2 are monomeric proteins, while TLSOD3 isoenzyme exhibits dimeric structure with native molecular mass of 90 kDa. The pI values are estimated at pH 8.0, pH 7.2 and pH 6.6 for the three SODs which displayed pH optima at 7.6, 8.0 and 7.8, respectively. CuCl(2) and ZnCl(2) increase the activity of TLSOD2 and TLSOD3, while MnCl(2) increases the activity of TLSOD1. KCN inhibits the activity of TLSOD2 and TLSOD3, while a remarkable resistance of TLSOD1 isoenzyme was detected. TLSOD1 is suggested to be a manganese containing isoenzyme while TLSOD2 and TLSOD3 are suggested to be copper/zinc-containing isoenzymes. These results indicate the presence of three different forms of SODs in the larval stage of camel tick. This finding will contribute to our understanding of the physiology of these ectoparasites and the development of non-traditional methods to control them.

Biomarker responses as indication of contaminant effects in Oreochromis niloticus

The current study investigated oxidative stress parameters (enzymes activities, metallothionein content and lipid peroxidation) in freshwater fish, Oreochromis niloticus, tilapia exposure to Monjolinho River (in 4 months of year: January, April, July and November). One critical site in Monjolinho River (site B) was assessed in comparison to a reference site (site A). Water pH and oxygen concentration was lower than that recommended by CONAMA (Brazilian National Environmental Committee), resolution 357/2005 for protection of aquatic communities, and ammonium and the metals Cu, Zn, Mn and Fe (on all months) concentrations were higher than the maximum concentration recommended. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly decreased in liver and muscle in tilapia from Monjolinho River, throughout the year, in relation to reference except in gills that SOD activity increased. Glutathione S-transferase (GST) activity was significantly increased in liver of the tilapia from Monjolinho River in all sites, in relation to reference except in gills that GST activity increased in July and decreased in November, suggesting that GST activity could be induced to neutralize the pollutants toxicity. On the other hand, GST activity was significantly decreased in white muscle indicating a toxic effect of pollutants, resulting in a decreased ability of tilapia to perform defense reactions associated to GSTs. The decrease of catalase (CAT) activity in gills of the O. niloticus together with the increase of SOD activity, could explain the increased lipid peroxidation (LPO) level in this organ. Metallothionein levels in liver and gills were significantly high in all sites. Results indicate that the exposure to metals caused severe damage to tissues; despite the consensually assumed antioxidant induction as a sign of exposure to contaminants the effects seem in part to be mediated by suppression of antioxidant system with SOD, CAT and GPx as potential candidates for tissues toxicity biomarkers of pollutants.

Reactive oxygen species scavenging by catalase is important for female Lutzomyia longipalpis fecundity and mortality

The phlebotomine sand fly Lutzomyia longipalpis is the most important vector of American visceral leishmaniasis (AVL), the disseminated and most serious form of the disease in Central and South America. In the natural environment, most female L. longipalpis are thought to survive for less than 10 days and will feed on blood only once or twice during their lifetime. Successful transmission of parasites occurs when a Leishmania-infected female sand fly feeds on a new host. Knowledge of factors affecting sand fly longevity that lead to a reduction in lifespan could result in a decrease in parasite transmission. Catalase has been found to play a major role in survival and fecundity in many insect species. It is a strong antioxidant enzyme that breaks down toxic reactive oxygen species (ROS). Ovarian catalase was found to accumulate in the developing sand fly oocyte from 12 to 48 hours after blood feeding. Catalase expression in ovaries as well as oocyte numbers was found to decrease with age. This reduction was not found in flies when fed on the antioxidant ascorbic acid in the sugar meal, a condition that increased mortality and activation of the prophenoloxidase cascade. RNA interference was used to silence catalase gene expression in female Lu. longipalpis. Depletion of catalase led to a significant increase of mortality and a reduction in the number of developing oocytes produced after blood feeding. These results demonstrate the central role that catalase and ROS play in the longevity and fecundity of phlebotomine sand flies.

Identification of anhydrobiosis-related genes from an expressed sequence tag database in the cryptobiotic midge Polypedilum vanderplanki (Diptera; Chironomidae)

Some organisms are able to survive the loss of almost all their body water content, entering a latent state known as anhydrobiosis. The sleeping chironomid (Polypedilum vanderplanki) lives in the semi-arid regions of Africa, and its larvae can survive desiccation in an anhydrobiotic form during the dry season. To unveil the molecular mechanisms of this resistance to desiccation, an anhydrobiosis-related Expressed Sequence Tag (EST) database was obtained from the sequences of three cDNA libraries constructed from P. vanderplanki larvae after 0, 12, and 36 h of desiccation. The database contained 15,056 ESTs distributed into 4,807 UniGene clusters. ESTs were classified according to gene ontology categories, and putative expression patterns were deduced for all clusters on the basis of the number of clones in each library; expression patterns were confirmed by real-time PCR for selected genes. Among up-regulated genes, antioxidants, late embryogenesis abundant (LEA) proteins, and heat shock proteins (Hsps) were identified as important groups for anhydrobiosis. Genes related to trehalose metabolism and various transporters were also strongly induced by desiccation. Those results suggest that the oxidative stress response plays a central role in successful anhydrobiosis. Similarly, protein denaturation and aggregation may be prevented by marked up-regulation of Hsps and the anhydrobiosis-specific LEA proteins. A third major feature is the predicted increase in trehalose synthesis and in the expression of various transporter proteins allowing the distribution of trehalose and other solutes to all tissues.

Selection of reference genes for quantitative RT-PCR studies in Rhipicephalus (Boophilus) microplus and Rhipicephalus appendiculatus ticks and determination of the expression profile of Bm86

Background

For accurate and reliable gene expression analysis, normalization of gene expression data against reference genes is essential. In most studies on ticks where (semi-)quantitative RT-PCR is employed, normalization occurs with a single reference gene, usually β-actin, without validation of its presumed expression stability. The first goal of this study was to evaluate the expression stability of commonly used reference genes in Rhipicephalus appendiculatus and Rhipicephalus (Boophilus) microplus ticks. To demonstrate the usefulness of these results, an unresolved issue in tick vaccine development was examined. Commercial vaccines against R. microplus were developed based on the recombinant antigen Bm86, but despite a high degree of sequence homology, these vaccines are not effective against R. appendiculatus. In fact, Bm86-based vaccines give better protection against some tick species with lower Bm86 sequence homology. One possible explanation is the variation in Bm86 expression levels between R. microplus and R. appendiculatus. The most stable reference genes were therefore used for normalization of the Bm86 expression profile in all life stages of both species to examine whether antigen abundance plays a role in Bm86 vaccine susceptibility.

Results

The transcription levels of nine potential reference genes: β-actin (ACTB), β-tubulin (BTUB), elongation factor 1α (ELF1A), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), glutathione S-transferase (GST), H3 histone family 3A (H3F3A), cyclophilin (PPIA), ribosomal protein L4 (RPL4) and TATA box binding protein (TBP) were measured in all life stages of R. microplus and R. appendiculatus. ELF1A was found to be the most stable expressed gene in both species following analysis by both geNorm and Normfinder software applications, GST showed the least stability. The expression profile of Bm86 in R. appendiculatus and R. microplus revealed a more continuous Bm86 antigen abundance in R. microplus throughout its one-host life cycle compared to the three-host tick R. appendiculatus where large variations were observed between different life stages.

Conclusion

Based on these results, ELF1A can be proposed as an initial reference gene for normalization of quantitative RT-PCR data in whole R. microplus and R. appendiculatus ticks. The observed differences in Bm86 expression profile between the two species alone can not adequately explain the lack of a Bm86 vaccination effect in R. appendiculatus.

Silencing of genes involved in Anaplasma marginale-tick interactions affects the pathogen developmental cycle in Dermacentor variabilis

BACKGROUND

The cattle pathogen, Anaplasma marginale, undergoes a developmental cycle in ticks that begins in gut cells. Transmission to cattle occurs from salivary glands during a second tick feeding. At each site of development two forms of A. marginale (reticulated and dense) occur within a parasitophorous vacuole in the host cell cytoplasm. However, the role of tick genes in pathogen development is unknown. Four genes, found in previous studies to be differentially expressed in Dermacentor variabilis ticks in response to infection with A. marginale, were silenced by RNA interference (RNAi) to determine the effect of silencing on the A. marginale developmental cycle. These four genes encoded for putative glutathione S-transferase (GST), salivary selenoprotein M (SelM), H+ transporting lysosomal vacuolar proton pump (vATPase) and subolesin.

RESULTS

The impact of gene knockdown on A. marginale tick infections, both after acquiring infection and after a second transmission feeding, was determined and studied by light microscopy. Silencing of these genes had a different impact on A. marginale development in different tick tissues by affecting infection levels, the densities of colonies containing reticulated or dense forms and tissue morphology. Salivary gland infections were not seen in any of the gene-silenced ticks, raising the question of whether these ticks were able to transmit the pathogen.

CONCLUSION

The results of this RNAi and light microscopic analyses of tick tissues infected with A. marginale after the silencing of genes functionally important for pathogen development suggest a role for these molecules during pathogen life cycle in ticks.

Purification and partial characterization of glutathione S-transferase from insecticide-resistant field populations of Liposcelis paeta Pearman (Psocoptera: Liposcelididae)

Enzymes that possess glutathione S-transferase (GST) activity were purified to homogeneity by glutathione-agarose affinity chromatography from three field populations of Liposcelis paeta (Pearman). These populations were collected from Nanyang city of Henan Province (NY), Wuzhou (WZ) and Hezhou (HZ) cities of Guangxi Province, China, and had different susceptibilities to dichlorvos [LC(50)s of the NY (281.48 mg/m(2)), the WZ (285.07 mg/m(2)), and the HZ (243.52 mg/m(2)), respectively]. The specific activities of purified enzymes from these three populations increased 32.24-, 99.81-, and 42.52-fold, respectively. Kinetic analyses showed that the catalytic activity of purified GST from NY population towards GSH was much higher than the others, while WZ population reached the highest in V(max) (CDNB). SDS-polyacrylamide electrophoresis revealed that the purified GST had two subunits with a molecular mass of 23.31 and 20.43 kDa for NY, 53.14 and 20.13 kDa for WZ, and 50.79 and 19.42 kDa for HZ, respectively. The in vitro inhibition studies of GSTs indicated that three kinds of insecticides (chlorpyrifos, carbosulfan, and cypermethrin) and five metallic ions (Zn(2+), Ba(2+), Ca(2+), Hg(2+), Mn(2+), and Mg(2+)) all possessed inhibitory effects on purified GST, and ethacrynic acid (EA, a specific inhibitor of GST) expressed inhibitory effects. In the bioassay, three populations of L. paeta had different susceptibilities to different insecticides, even after they were reared on diets consisting of 25% EA. The GST activities of L. paeta from different areas also showed different temperature and pH stabilities. The differences in GST among the three populations may be attributed partially to the differences in control practices for psocids between Henan and Guangxi Provinces. (c) 2009 Wiley Periodicals, Inc.

[Expression and enzymatic activity of glutathione s-transferase in tissues of Boophilus microplus females]

Cellular detoxification and excretion enzymes are important to the maintenance of cellular homeostasis. In this work mRNA transcription, protein expression and enzymatic activity of Glutathione S-transferases (GSTs), enzymes involved in the excretion of endo and xenobiotic compounds were analyzed. These parameters are elements believed to protect cells against chemical toxicity and oxidative stress in different tissues (salivary gland, ovary and synganglion) from partially engorged females and engorged females of Boophilus microplus. The results presented showed elevated GST activity in partially engorged females. The enzymatic activity decreased during the preoviposition period in engorged females. GST mRNA transcription was detected in salivary glands and synganglion from partially engorged and engorged females, but not in ovary. The results of this work help to elucidate the role of GST in tick development and assist in the understanding of the importance of GST in tick females during the preparation for oviposition.

Oxidative stress as a mediator of life history trade-offs: mechanisms, measurements and interpretation

The concept of trade-offs is central to our understanding of life-history evolution. The underlying mechanisms, however, have been little studied. Oxidative stress results from a mismatch between the production of damaging reactive oxygen species (ROS) and the organism's capacity to mitigate their damaging effects. Managing oxidative stress is likely to be a major determinant of life histories, as virtually all activities generate ROS. There is a recent burgeoning of interest in how oxidative stress is related to different components of animal performance. The emphasis to date has been on immediate or short-term effects, but there is an increasing realization that oxidative stress will influence life histories over longer time scales. The concept of oxidative stress is currently used somewhat loosely by many ecologists, and the erroneous assumption often made that dietary antioxidants are necessarily the major line of defence against ROS-induced damage. We summarize current knowledge on how oxidative stress occurs and the different methods for measuring it, and highlight where ecologists can be too simplistic in their approach. We critically review the potential role of oxidative stress in mediating life-history trade-offs, and present a framework for formulating appropriate hypotheses and guiding experimental design. We indicate throughout potentially fruitful areas for further research.

Disruption of circulation by ethanol promotes fetal alcohol spectrum disorder (FASD) in medaka (Oryzias latipes) embryogenesis

Japanese medaka (Oryzias latipes) embryos exposed to ethanol have developed craniofacial, cardiovascular and skeletal defects which can be compared with the phenotypic features of fetal alcohol spectrum disorder (FASD) observed in human. The present experiment was designed to show that the disruption in circulation by ethanol during embryogenesis is a potential cause of FASD. Fertilized eggs were exposed to ethanol (0, 100 and/or 400 mM) for 24 or 48 h at various developmental stages (Iwamatsu stages 4-30) and were analyzed at 6 day post fertilization (dpf). It was observed that controls and the embryos exposed to 100 mM ethanol were in circulating state; however, a significant number of embryos of stages 4-24 exposed to 400 mM ethanol had disrupted circulation. Compared to controls, protein and RNA contents were significantly reduced in non-circulating embryos. Lipid peroxidation (LPO) analysis was made at 3, 6, 24, 48, 96 and 144 hour post fertilization (hpf). LPO was increased with the advancement of morphogenesis; however, ethanol or the circulation status had no effect. We further analyzed alcohol dehydrogenase (Adh 5 and adh8) and aldehyde dehydrogenase (Aldh9A and Aldh1A2) enzyme mRNAs in the embryos exposed to 400 mM ethanol for 24 h. A developmental stage-specific reduction in these enzyme mRNAs by ethanol was observed. We conclude that ethanol-induced disruption in circulation during embryogenesis is a potential cause of the development of FASD features in medaka.

Oxidative stress impairs heme detoxification in the midgut of the cattle tick, Rhipicephalus (Boophilus) microplus

In the cattle tick Rhipicephalus (Boophilus) microplus digestion of blood is intracellular, accomplished by the so-called digest cells that fill the midgut lumen. Hydrolysis of hemoglobin in the digestive vesicles of these cells results in the release of large amounts of heme, a pro-oxidant compound, whose iron atom, together with H(2)O(2), may participate in the Fenton reaction and lead to the production of hydroxyl radicals. Here, we investigated the role of catalase, an enzyme responsible for H(2)O(2) detoxification. Fully engorged female ticks injected with 3-amino-1,2,4-triazole (AT), a catalase inhibitor, showed increased H(2)O(2) in the gut, together with diminished life span and lower egg-laying rates. Increased mortality observed upon AT injection was reversed by further injection of exogenous catalase, 2 days after AT treatment, confirming that increased death was due to inhibition of this enzyme by AT. In primary cultures of digest cells, intracellular H(2)O(2) is limited to specific organelles, while treatment with AT in vitro resulted in increased H(2)O(2) spreading all over the cell, confirming the role of catalase in regulating H(2)O(2) levels. Ticks fed on a calf that had been injected with AT showed marked inhibition of catalase activity in the gut and diminished life span, oviposition and engorgement. Digest cells of these ticks had an altered morphology, showing heme spread all over the cytosol, instead of being limited to the hemosomes. The amount of aggregated heme found in isolated hemosome was also strongly decreased in AT-treated cattle. All together, our results indicate that catalase performs an important role in the control of redox balance in R. microplus, which dramatically affects hemosome formation and stability. This enzyme may be a target in the development of new methods for tick control.

The cost of Latin American science Introduction for the second issue of CBP-Latin America

Latin American researchers in science and engineering (S&E), including those in biology and biomedical sciences, are frequently exposed to unstable conditions of financial support, material and human resources, and a limited number of positions at public and private institutions. Such uncertainties impose continuous challenges for the scientific community which, in the best of cases, responds with careful planning and creativity, and in the worst scenario endures the migration of scientists to the USA or Europe. Still, the number of scientific publications from Latin American institutions in the last decade increased at a much faster rate than publications from the USA and Canada. A brief analysis per country of the gross domestic product (GDP) spent in research and development (R&D) and the S&E production reported by the Pascal bibliographic database suggests that the number and quality of S&E publications is directly proportional to the financial support for R&D. However, the investment in R&D in Latin America did not increase at the same rate (from 0.49 to 0.55% of GDP, from 1990 to 2003) at which S&E publications did in the same period (2.9-fold increase, from 1988 to 2001). In Latin America, the traditional financial support for scientific research continues to be from federal and state government funds, associated in some cases with institutional funds that are mostly directed towards administrative costs and infrastructure maintenance. The aim of this introduction is to briefly discuss the production cost of articles published in refereed S&E journals, including the cost of the scientific research behind them, and, at the same time, to increase the awareness of the high quality of scientific research in Latin American institutions despite the many challenges, especially financial constraints, faced by their scientists. The second issue of Comparative Biochemistry and Physiology dedicated to Latin America ("The Face of Latin American Comparative Biochemistry and Physiology") celebrates, by means of 26 manuscripts from five countries, the diversity and quality of biological science in the continent.