Reactive oxygen species detoxification by catalase is a major determinant of fecundity in the mosquito Anopheles gambiae

Glucose and trehalose metabolism through the cyclic pentose phosphate pathway shapes pathogen resistance and host protection in Drosophila

Activation of immune cells requires the remodeling of cell metabolism in order to support immune function. We study these metabolic changes through the infection of Drosophila larvae by parasitoid wasp. The parasitoid egg is neutralized by differentiating lamellocytes, which encapsulate the egg. A melanization cascade is initiated, producing toxic molecules to destroy the egg while the capsule also protects the host from the toxic reaction. We combined transcriptomics and metabolomics, including 13C-labeled glucose and trehalose tracing, as well as genetic manipulation of sugar metabolism to study changes in metabolism, specifically in Drosophila hemocytes. We found that hemocytes increase the expression of several carbohydrate transporters and accordingly uptake more sugar during infection. These carbohydrates are metabolized by increased glycolysis, associated with lactate production, and cyclic pentose phosphate pathway (PPP), in which glucose-6-phosphate is re-oxidized to maximize NADPH yield. Oxidative PPP is required for lamellocyte differentiation and resistance, as is systemic trehalose metabolism. In addition, fully differentiated lamellocytes use a cytoplasmic form of trehalase to cleave trehalose to glucose and fuel cyclic PPP. Intracellular trehalose metabolism is not required for lamellocyte differentiation, but its down-regulation elevates levels of reactive oxygen species, associated with increased resistance and reduced fitness. Our results suggest that sugar metabolism, and specifically cyclic PPP, within immune cells is important not only to fight infection but also to protect the host from its own immune response and for ensuring fitness of the survivor.

A computational strategy for systematic virtual screening of plasmodium falciparum heme detoxification protein inhibitors from the Drugbank database

Antimalarial drug resistance poses one of the greatest threats to malaria treatment, resulting in increased morbidity and mortality. Heme Detoxification Protein (HDP) is among the essential hemoglobinases of P. falciparum (Pf), a vital molecular target for the treatment of malaria. In this study, we utilized the virtual screening workflow tool of the Schrodinger suite to find the best hits for the PfHDP from the DrugBank library. A total of 14,942 compounds were identified against the PfHDP. The top compounds with the highest docking scores and least energy scores were subjected to molecular simulations for 500 nanosecond to check the stability of the protein-drug complexes. The top three DrugBank compounds were found to be stable over 500 ns, namely DB09298 (silibinin), DB07426 (1-Hydroxy-2-(1,1':3',1''-Terphenyl-3-Yloxy) Ethane-1,1-Diyl] Bis (Phosphonic Acid), and DB07410 [(2-(3-Dibenzofuran-4-yl-Phenyl)-1-Hydroxy-1-Phosphono-Ethyl]-Phosphonic Acid). Overall analysis suggests that the top three compounds, DB09298, DB07426, and DB07410, have good stability for 500 ns. Their scaffolds can be used to design and develop new analogs of the target HDP protein. Silibinin, the anti-cancer drug, was found to be highly stable for the entire simulation period as compared to the other compounds. DB07426 shows its therapeutic effect on bones, especially in the treatment of osteoporosis, and DB07410 has anti-tumor, antibacterial, anti-oxidative, and anti-viral activities. All three compounds can be considered for repurposing as antimalarial drugs to evaluate the binding capacity or inhibition potential of these compounds. Further in-vivo and in-vitro analysis against the PfHDP protein should be conducted.Communicated by Ramaswamy H. Sarma.

Histopathological observations and comparative transcriptome analysis of Ophiocordyceps sinensis infection of Hepialus xiaojinensis in the early stage

Hepialus xiaojinensis is a Lepidopteran insect and one of the hosts for the artificial cultivation of Cordyceps. Ophiocordyceps sinensis can infect and coexist with H. xiaojinensis larvae for a long time. Little studies focused on the interaction process through its early infection stage. In this research, we particularly study the interaction of infected and uninfected larvae in the 3rd (OS-3, CK-3) and 4th (OS-4, CK-4) instars. O. sinensis was distributed within the larvae and accompanied by pathological changes in some tissue structures. In response to O. sinensis infection, OS-3 enhanced the antioxidant defense ability, while OS-4 decreased. The transcriptome analysis showed that OS-3 resisted the invasion of O. sinensis by the immune and nervous systems. Correspondingly, OS-4 reduced immune response and utilized more energy for growth and development. This study provides a comprehensive resource for analyzing the mechanism of H. xiaojinensis and O. sinensis interaction.

How to eliminate pathogen without killing oneself? Immunometabolism of encapsulation and melanization in Drosophila

Cellular encapsulation associated with melanization is a crucial component of the immune response in insects, particularly against larger pathogens. The infection of a Drosophila larva by parasitoid wasps, like Leptopilina boulardi, is the most extensively studied example. In this case, the encapsulation and melanization of the parasitoid embryo is linked to the activation of plasmatocytes that attach to the surface of the parasitoid. Additionally, the differentiation of lamellocytes that encapsulate the parasitoid, along with crystal cells, is accountable for the melanization process. Encapsulation and melanization lead to the production of toxic molecules that are concentrated in the capsule around the parasitoid and, at the same time, protect the host from this toxic immune response. Thus, cellular encapsulation and melanization represent primarily a metabolic process involving the metabolism of immune cell activation and differentiation, the production of toxic radicals, but also the production of melanin and antioxidants. As such, it has significant implications for host physiology and systemic metabolism. Proper regulation of metabolism within immune cells, as well as at the level of the entire organism, is therefore essential for an efficient immune response and also impacts the health and overall fitness of the organism that survives. The purpose of this "perspective" article is to map what we know about the metabolism of this type of immune response, place it in the context of possible implications for host physiology, and highlight open questions related to the metabolism of this important insect immune response.

Time-series analysis of transcriptomic changes due to permethrin exposure reveals that Aedes aegypti undergoes detoxification metabolism over 24 h

Insecticide resistance is a multifaceted response and an issue across taxa. Aedes aegypti, the mosquito that vectors Zika, dengue, chikungunya, and yellow fever, demonstrates high levels of pyrethroid resistance across the globe, presenting a challenge to public health officials. To examine the transcriptomic shifts across time after exposure to permethrin, a 3'Tag-Seq analysis was employed on samples 6, 10, and 24 h after exposure along with controls. Differential expression analysis revealed significant shifts in detoxifying enzymes and various energy-producing metabolic processes. These findings indicate significant alterations in gene expression associated with key energy mobilization pathways within the system. These changes encompass a coordinated response involving lipolysis, beta-oxidation, and the citric acid cycle, required for the production of energetic molecules such as ATP, NADH, NADPH, and FADH. These findings highlight a complex interplay of metabolic processes that may have broader implications for understanding insect physiology and response to environmental stimuli. Among the upregulated detoxifying enzymes are cytochrome P450s, glutathione s-transferases and peroxidases, and ATP-binding cassette transporters. Additionally, eight heat shock genes or genes with heat shock domains exhibit the highest fold change across time. Twenty-four hours after exposure, samples indicate a global downregulation of these processes, though principal component analysis suggests lasting signatures of the response. Understanding the recovery response to insecticide exposure provides information on possible new genetic and synergist targets to explore.

Chikungunya virus infection in Aedes aegypti is modulated by L-cysteine, taurine, hypotaurine and glutathione metabolism

BACKGROUND

Blood meal and infections cause redox imbalance and oxidative damage in mosquitoes which triggers the mosquito's system to produce antioxidants in response to increased oxidative stress. Important pathways activated owing to redox imbalance include taurine, hypotaurine and glutathione metabolism. The present study was undertaken to evaluate the role of these pathways during chikungunya virus (CHIKV) infection in Aedes aegypti mosquitoes.

METHODOLOGY

Using a dietary L-cysteine supplement system, we upregulated these pathways and evaluated oxidative damage and oxidative stress response upon CHIKV infection using protein carbonylation and GST assays. Further, using a dsRNA based approach, we silenced some of the genes involved in synthesis and transport of taurine and hypotaurine and then evaluated the impact of these genes on CHIKV infection and redox biology in the mosquitoes.

CONCLUSIONS

We report that CHIKV infection exerts oxidative stress in the A. aegypti, leading to oxidative damage and as a response, an elevated GST activity was observed. It was also observed that dietary L-cysteine treatment restricted CHIKV infection in A. aegypti mosquitoes. This L-cysteine mediated CHIKV inhibition was coincided by enhanced GST activity that further resulted in reduced oxidative damage during the infection. We also report that silencing of genes involved in synthesis of taurine and hypotaurine modulates CHIKV infection and redox biology of Aedes mosquitoes during the infection.

The microbiota, the malarial parasite, and the mosquito [MMM] - A three-sided relationship

The mosquito gut microbiota is vital to the proper functioning of the host organism. Mosquitoes may benefit from this microbiota in their guts because it promotes factors including blood digestion, fecundity, metamorphosis, and living habitat and inhibits malarial parasites (Plasmodium) growth or transmission. In this overview, we analyzed how mosquitoes acquire their gut microbiota, characterized those bacteria, and discussed the functions they provide. We also investigated the effects of microbiota on malaria vectors, with a focus on the mosquito species Anopheles, as well as the relationship between microbiota and Plasmodium, the aspects in which microbiota influences Plasmodium via immune response, metabolism, and redox mechanisms, and the strategies in which gut bacteria affect the life cycle of malaria vectors and provide the ability to resist insecticides. This article explores the difficulties in studying triadic interactions, such as the interplay between Mosquitoes, Malarial parasite, and the Microbiota that dwell in the mosquitoes' guts, and need additional research for a better understanding of these multiple connections to implement an exact vector control strategies using Gut microbiota in malaria control.

Identifying metabolic shifts in Crohn's disease using' omics-driven contextualized computational metabolic network models

Crohn's disease (CD) is a chronic inflammatory disease of the gastrointestinal tract. A clear gap in our existing CD diagnostics and current disease management approaches is the lack of highly specific biomarkers that can be used to streamline or personalize disease management. Comprehensive profiling of metabolites holds promise; however, these high-dimensional profiles need to be reduced to have relevance in the context of CD. Machine learning approaches are optimally suited to bridge this gap in knowledge by contextualizing the metabolic alterations in CD using genome-scale metabolic network reconstructions. Our work presents a framework for studying altered metabolic reactions between patients with CD and controls using publicly available transcriptomic data and existing gene-driven metabolic network reconstructions. Additionally, we apply the same methods to patient-derived ileal enteroids to explore the utility of using this experimental in vitro platform for studying CD. Furthermore, we have piloted an untargeted metabolomics approach as a proof-of-concept validation strategy in human ileal mucosal tissue. These findings suggest that in silico metabolic modeling can potentially identify pathways of clinical relevance in CD, paving the way for the future discovery of novel diagnostic biomarkers and therapeutic targets.

Genomic analyses provide insights into the genome evolution and environmental adaptation of the tobacco moth Ephestia elutella

Ephestia elutella is a major pest responsible for significant damage to stored tobacco over many years. Here, we conduct a comparative genomic analysis on this pest, aiming to explore the genetic bases of environmental adaptation of this species. We find gene families associated with nutrient metabolism, detoxification, antioxidant defense and gustatory receptors are expanded in the E. elutella genome. Detailed phylogenetic analysis of P450 genes further reveals obvious duplications in the CYP3 clan in E. elutella compared to the closely related species, the Indianmeal moth Plodia interpunctella. We also identify 229 rapidly evolving genes and 207 positively selected genes in E. elutella, respectively, and highlight two positively selected heat shock protein 40 (Hsp40) genes. In addition, we find a number of species-specific genes related to diverse biological processes, such as mitochondria biology and development. These findings advance our understanding of the mechanisms underlying processes of environmental adaptation on E. elutella and will enable the development of novel pest management strategies.

Transcriptome analysis of aphids exposed to glandular trichomes in tomato reveals stress and starvation related responses

Understanding the responses of insect herbivores to plant chemical defences is pivotal for the management of crops and pests. However, the mechanisms of interaction are not entirely understood. In this study, we compared the whole transcriptome gene expression of the aphid Macrosiphum euphorbiae grown on two different varieties of tomato that differ in their inducible chemical defences. We used two isogenic lines of tomato with a shared genetic background that only differ in the presence of type IV glandular trichomes and their associated acylsucrose excretions. This works also reports a de novo transcriptome of the aphid M. euphorbiae. Subsequently, we identified a unique and distinct gene expression profile for the first time corresponding to aphid´s exposure to type IV glandular trichomes and acylsugars. The analysis of the aphid transcriptome shows that tomato glandular trichomes and their associated secretions are highly efficient in triggering stress-related responses in the aphid, and demonstrating that their role in plant defence goes beyond the physical impediment of herbivore activity. Some of the differentially expressed genes were associated with carbohydrate, lipid and xenobiotic metabolisms, immune system, oxidative stress response and hormone biosynthesis pathways. Also, the observed responses are compatible with a starvation syndrome. The transcriptome analysis puts forward a wide range of genes involved in the synthesis and regulation of detoxification enzymes that reveal important underlying mechanisms in the interaction of the aphid with its host plant and provides a valuable genomic resource for future study of biological processes at the molecular level using this aphid.

Investigating the Antibacterial Activity and Safety of Zinc Oxide Nanoparticles versus a Commercial Alcohol-Based Hand-Sanitizer: Can Zinc Oxide Nanoparticles Be Useful for Hand Sanitation?

Hand hygiene is the key factor to control and prevent the spread of infections, for example, hospital-acquired infections (HAIs). People commonly use alcohol-based hand sanitizers to assure hand hygiene. However, frequent use of alcohol-based hand sanitizers in a pandemic situation (e.g., COVID-19) was associated with serious drawbacks such as skin toxicity including irritation, skin dermatitis, and skin dryness or cracking, along with peeling, redness, or itching with higher possibility of infection. This demands the development of alternative novel products that are effective as alcohol-based hand sanitizers but have no hazardous effects. Zinc oxide nanoparticles (ZnO-NPs) are known to have broad-spectrum antimicrobial activity, be compatible with the biological system and the environment, and have applicable and economic industrial-scale production. Thus, ZnO-NPs might be a good candidate for hand sanitation. To the best of our knowledge, the antibacterial activity of ZnO-NPs in comparison to alcohol-based hand sanitizers has not yet been studied. In the present work, a comparative study of the antibacterial activity of ZnO-NPs vs. Sterillium, a commercial alcohol-based hand sanitizer that is commonly used in Egyptian hospitals, was performed against common microorganisms known to cause HAIs in Egypt, including Acinetobacter baumannii, Klebsiella pneumoniae, Methicillin-resistant Staphylococcus aureus (MRSA), and Staphylococcus aureus. The safety profiles of ZnO-NPs and Sterillium were also assessed. The obtained results demonstrated the superior antibacterial activity and safety of ZnO-NPs compared to Sterillium. Therefore, ZnO-NPs could be a promising candidate for hand sanitation in comparison to alcohol-based hand sanitizers; however, several studies related to long-term toxicity and stability of ZnO-NPs and investigations into their antimicrobial activity and safety in healthcare settings are still required in the future to ascertain their antimicrobial activity and safety.

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.

Beyond the eye: Kynurenine pathway impairment causes midgut homeostasis dysfunction and survival and reproductive costs in blood-feeding mosquitoes

Insect ommochrome biosynthesis pathways metabolize tryptophan to generate eye-color pigments and wild-type alleles of pathway genes are useful phenotypic markers in transgenesis studies. Pleiotropic effects of mutations in some genes exert a load on both survival and reproductive success in blood-feeding species. Here, we investigated the challenges imposed on mosquitoes by the increase of tryptophan metabolites resulting from blood meal digestion and the impact of disruptions of the ommochrome biosynthesis pathway. Female mosquitoes with spontaneous and induced mutations in the orthologs of the genes encoding kynurenine hydroxylase in Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus exhibited impaired survival and reproductive phenotypes that varied in type and severity among the species. A compromised midgut permeability barrier function was also observed in An. stephensi. Surprisingly, mutant mosquitoes displayed an increase in microbiota compared to controls that was not accompanied by a general induction of immune genes. Antibiotic treatment rescued some deleterious traits implicating a role for the kynurenine pathway (KP) in midgut homeostasis. Supplemental xanthurenic acid, a KP end-product, rescued lethality and limited microbiota proliferation in Ae. aegypti. These data implicate the KP in the regulation of the host/microbiota interface. These pleiotropic effects on mosquito physiology are important in the development of genetic strategies targeting vector mosquitoes.

Assessment of Sex-Specific Toxicity and Physiological Responses to Thymol in a Common Bean Pest Acanthoscelides obtectus Say

Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae: Bruchinae), is one of the most important pests of the common bean Phaseolus vulgaris L. Without appropriate management it may cause significant seed loss in storages. In search for means of environmentally safe and effective protection of beans we assessed biological activity of thymol, an oxygenated monoterpene present in essential oils of many aromatic plants. We studied contact toxicity of thymol on bean seeds and its effects on adult longevity and emergence in F1 generation. Furthermore, we determined acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), mixed-function oxidase (MFO), carboxylesterases (CarE) and glutathione S-transferase (GST) activities in response to 24 h exposure of beetles to sublethal and lethal thymol concentrations. Our results showed that thymol decreased adult survival, longevity and percentage of adult emergence. Higher median lethal concentration (LC50) was recorded in females indicating their higher tolerance comparing to males. Overall, activities of SOD, CAT and CarE increased at sublethal and MFO increased at both sublethal and lethal thymol concentrations. On the other hand, GST and AChE activities decreased along with the increase in thymol concentrations from sublethal (1/5 of LC50, 1/2 of LC50) to lethal (LC50). Enzyme responses to the presence of thymol on bean seed were sex-specific. In the control group females had lower CarE and higher SOD, CAT and GST activity than males. In treatment groups, females had much higher CAT activity and much lower CarE activity than males. Our results contribute to deeper understanding of physiological mechanisms underlying thymol toxicity and tolerance which should be taken into account in future formulation of a thymol-based insecticide.

Epigenetic regulations enhance adaptability and valorization efficiency in Eisenia fetida and Eudrilus eugeniae during vermicomposting of textile sludge: Insights on repair mechanisms of metal-induced genetic damage and oxidative stress

Genotoxicity-based assessments of vermitechnology for textile-sludge valorization have rarely been attempted. Therefore, waste sanitization and epigenetic stress-regulation efficiency of Eisenia fetida and Eudrilus eugeniae were evaluated in silk (DSPS) and cotton (CPWS) processing sludge-based vermibeds. Vermicomposting resulted in greater C, N, and P recovery than composting. Earthworm population reduced by 6-50% in DSPS/CPWS, while it significantly increased in cow dung (CD) mixed DSPS/CPWS. The Cr, Cd, Pb, and Zn accumulation efficiency of earthworms was higher in DSPS-based feedstocks than CPWS. However, metal-rich sludge elevated oxidative stress, causing greater inhibition of cell viability and DNA damage in Eudrilus than in Eisenia. Although histo-architecture of chloragogenous tissues was perturbed, earthworms combatted metal-induced lipid peroxidation via the activation of catalase, superoxide-dismutase, and reduced-glutathione. Correlation statistics revealed that genetic integrity in earthworms was restored through DNA-methyltransferase activity, especially in DSPS/CPWS + CD vermibeds. Overall, Eisenia was a healthier choice than Eudrilus for sustainable valorization of textile-sludge.

Anopheles gambiae Actively Metabolizes Uric Acid Following Plasmodium Infection to Limit Malaria Parasite Survival

Characterizing the physiological changes that accompany malaria parasite infection of the mosquito host is crucial to our understanding of vectorial capacity in Anopheles mosquitoes, yet has not fully been explored. In this study, we examine the role of uric acid metabolism in the mosquito, Anopheles gambiae, following malaria parasite infection. We demonstrate that levels of uric acid are significantly decreased in the excreta and the mosquito at 24 and 48 h post-Plasmodium infection when compared to controls fed on naïve mouse blood. When we examine the expression of well-known enzymes responsible for uric acid metabolism, we see a significant increase in both urate oxidase (UO) and allatoicase (ALLC) expression following Plasmodium infection. Targeting the essential first step in uric acid metabolism by silencing UO resulted in elevated levels of uric acid, enhancing malaria parasite survival. With implications from other insect systems that bacteria can modulate UO expression, we examined the possibility that the mosquito microbiota and its expansion following blood-feeding may contribute to increased UO levels. However, there was no difference in uric acid metabolism between septic and aseptic mosquitoes, indicating that the mosquito microbiome is not associated with the manipulation of UO expression. Together, our study provides new evidence that Plasmodium infection causes the mosquito host to actively metabolize uric acid by increasing UO expression to limit Plasmodium oocyst survival, suggesting that nitrogen metabolism is an essential pathway in defining mosquito vector competence.

Monitoring Mitochondrial Function in Aedes albopictus C6/36 Cell Line during Dengue Virus Infection

Simple Summary

Dengue is an important and growing public health problem. To date, no specific therapeutic or effective prophylactic measures exist. Therefore, vector control remains the primary approach to prevent dengue virus (DENV) infection in humans. Recent findings highlight that viruses regulate mitochondrial function and dynamics to facilitate viral proliferation. In this study, we report that DENV infection modulates mitochondrial physiology in C6/36 mosquito cells. Our results revealed that DENV alters redox metabolism and mitochondrial membrane potential without any significant change in cellular ATP pool or viability. In addition, we observed preservation of the respiratory control ratio and translocation of mitofusins to mitochondria. These results suggest that mitochondrial fusion could be required for the maintenance of mitochondrial function in C6/36 mosquito cells infected with DENV.

Abstract

Aedes aegypti and Aedes albopictus mosquitoes are responsible for dengue virus (DENV) transmission in tropical and subtropical areas worldwide, where an estimated 3 billion people live at risk of DENV exposure. DENV-infected individuals show symptoms ranging from sub-clinical or mild to hemorrhagic fever. Infected mosquitoes do not show detectable signs of disease, even though the virus maintains a lifelong persistent infection. The interactions between viruses and host mitochondria are crucial for virus replication and pathogenicity. DENV infection in vertebrate cells modulates mitochondrial function and dynamics to facilitate viral proliferation. Here, we describe that DENV also regulates mitochondrial function and morphology in infected C6/36 mosquito cells (derived from Aedes albopictus). Our results showed that DENV infection increased ROS (reactive oxygen species) production, modulated mitochondrial transmembrane potential and induced changes in mitochondrial respiration. Furthermore, we offer the first evidence that DENV causes translocation of mitofusins to mitochondria in the C6/36 mosquito cell line. Another protein Drp-1 (Dynamin-related protein 1) did not localize to mitochondria in DENV-infected cells. This observation therefore ruled out the possibility that the abovementioned alterations in mitochondrial function are associated with mitochondrial fission. In summary, this report provides some key insights into the virus–mitochondria crosstalk in DENV infected mosquito cells.

Molecular characterization of a catalase gene from the green peach aphid (Myzus persicae)

The green peach aphid, Myzus persicae (Sulzer), is a serious agricultural pest with a worldwide distribution. Catalase (CAT), which is encoded by the catalase (Cat) gene, is an extremely important antioxidant enzyme that plays a pivotal role in protecting cells against the toxic effects of hydrogen peroxide. The Cat gene has not been characterized in M. persicae; therefore, this study describes the identification of the Cat (MpCat) gene from M. persicae. MpCat contains an open reading frame of 1515 bp and encodes a MpCAT protein consisting of 504 amino-acid residues. MpCAT possesses features typical of other insect catalases, including 7 conserved amino acids involved in binding heme and 15 involved in binding nicotinamide adenine dinucleotide phosphate. Phylogenetic analysis showed that MpCAT was closely related to orthologs from other aphid species. MpCat consisted of nine exons and eight introns, and the number and insertion sites of introns are consistent with those of Cat genes from Acyrthosiphon pisum (Harris) and Aphis gossypii Glover. The mRNA transcripts of MpCat were detected at all tested developmental stages, with the highest mRNA level in alate adults. The expression of MpCat was significantly upregulated when M. persicae was exposed to low and high temperatures, ultraviolet radiation, Beauveria bassiana, and permethrin. The transcription of MpCat and the activity of catalase were suppressed by RNA interference, and knockdown of MpCat significantly reduced the survival rate in M. persicae under heat stress. The results provide valuable information for further study on the physiological functions of MpCat.

Aedes aegypti Infection With Trypanosomatid Strigomonas culicis Alters Midgut Redox Metabolism and Reduces Mosquito Reproductive Fitness

Aedes aegypti mosquitoes transmit arboviruses of important global health impact, and their intestinal microbiota can influence vector competence by stimulating the innate immune system. Midgut epithelial cells also produce toxic reactive oxygen species (ROS) by dual oxidases (DUOXs) that are essential players in insect immunity. Strigomonas culicis is a monoxenous trypanosomatid that naturally inhabits mosquitoes; it hosts an endosymbiotic bacterium that completes essential biosynthetic pathways of the parasite and influences its oxidative metabolism. Our group previously showed that S. culicis hydrogen peroxide (H₂O₂)-resistant (WTR) strain is more infectious to A. aegypti mosquitoes than the wild-type (WT) strain. Here, we investigated the influence of both strains on the midgut oxidative environment and the effect of infection on mosquito fitness and immunity. WT stimulated the production of superoxide by mitochondrial metabolism of midgut epithelial cells after 4 days post-infection, while WTR exacerbated H₂O₂ production mediated by increased DUOX activity and impairment of antioxidant system. The infection with both strains also disrupted the fecundity and fertility of the females, with a greater impact on reproductive fitness of WTR-infected mosquitoes. The presence of these parasites induced specific transcriptional modulation of immune-related genes, such as attacin and defensin A during WTR infection (11.8- and 6.4-fold, respectively) and defensin C in WT infection (7.1-fold). Thus, we propose that A. aegypti oxidative response starts in early infection time and does not affect the survival of the H₂O₂-resistant strain, which has a more efficient antioxidant system. Our data provide new biological aspects of A. aegypti–S. culicis relationship that can be used later in alternative vector control strategies.

Interplay Between Oxytetracycline and the Homozygote kdr (L1014F) Resistance Genotype on Fecundity in Anopheles gambiae (Diptera: Culicidae) Mosquitoes

The insecticide resistance in Anopheles gambiae mosquitoes has remained the major threat for vector control programs but the fitness effects conferred by these mechanisms are poorly understood. To fill this knowledge gap, the present study aimed at testing the hypothesis that antibiotic oxytetracycline could have an interaction with insecticide resistance genotypes and consequently inhibit the fecundity in An. gambiae. Four strains of An. gambiae: Kisumu (susceptible), KisKdr (kdr (L1014F) resistant), AcerKis (ace-1 (G119S) resistant) and AcerKdrKis (both kdr (L1014F) and ace-1 (G119S) resistant) were used in this study. The different strains were allowed to bloodfeed on a rabbit previously treated with antibiotic oxytetracycline at a concentration of 39·10-5 M. Three days later, ovarian follicles were dissected from individual mosquito ovaries into physiological saline solution (0.9% NaCl) under a stereomicroscope and the eggs were counted. Fecundity was substantially lower in oxytetracycline-exposed KisKdr females when compared to that of the untreated individuals and oxytetracycline-exposed Kisumu females. The exposed AcerKis females displayed an increased fecundity compared to their nontreated counterparts whereas they had reduced fecundity compared to that of oxytetracycline-exposed Kisumu females. There was no substantial difference between the fecundity in the treated and untreated AcerKdrKis females. The oxytetracycline-exposed AcerKdrKis mosquitoes had an increased fecundity compared to that of the exposed Kisumu females. Our data indicate an indirect effect of oxytetracycline in reducing fecundity of An. gambiae mosquitoes carrying kdrR (L1014F) genotype. These findings could be useful for designing new integrated approaches for malaria vector control in endemic countries.

Characterization of life-history parameters of an Anopheles funestus (Diptera: Culicidae) laboratory strain

The colonization of the African malaria vector Anopheles funestus has been hampered by inadequate knowledge of its mating and development under laboratory conditions. Life-tables are routinely used to provide baseline biological characteristics needed for colonization. This study characterized age-specific life-table attributes of an existing An. funestus laboratory strain to gain insight into factors that are critical for its colonization. To achieve this, the An. funestus laboratory strain was reared from eggs to adulthood under standard insectary conditions, monitoring and characterizing each developmental stage. The mean insemination rate of females was 74.8% with an average egg load of 67.1 eggs/female and a mean fertility of 86.7%. The mean developmental time from 1^st instar larvae (L1) to pupation was 16.4 days. The mean proportion of L1 that survived to pupation was 72.9%. On average, 78.8% of the pupae successfully eclosed as adults. The median longevity for adult males and females was 44 and 28 days, respectively. This work constitutes the first report on life-table characterization of an An. funestus strain. The larval developmental time was within the range reported for wild An. funestus while adult longevity was higher compared to survivorship observed in wild populations. These data demonstrate that the colonized An. funestus strain has potential to be re-colonized under standard insectary conditions. The study provides base-line information for further studies on identifying critical parameters for the maintenance of An. funestus under artificial conditions.

Mild Abiotic Stress Affects Development and Stimulates Hormesis of Hemp Aphid Phorodon cannabis

The hemp aphid Phorodon cannabis Passerini is a well- known (Asia, Europe) or newly emerging (North America) insect. It is a monophagous insect pest causing considerable damage in field and glasshouse cultivations. The aim of this work was to study the effects of meteorological (temperature) and agronomical (herbicide) factors on the biology of the hemp aphid. In one experiment, hemp plants were kept at constant temperatures ranging from 20 to 30 °C, and aphid survival and fecundity were measured. In a related experiment conducted at 20 °C, plants were treated with field-appropriate rates of a selective graminicide containing quizalofop-P-tefuryl (40 gL-1, 4.38%, HRAC group 1), commonly used to control weeds in hemp, and aphid enzyme activity was measured in addition to population parameters. We found that hemp aphids could live, feed and reproduce within the whole studied range of temperatures, demonstrating its great evolutionary plasticity. However, the optimal temperature for development was 25 °C, at which the insect lived and reproduced for 25 and 15 days, respectively, with an average fecundity of 7.5 nymphs per reproduction day. The herbicide treatment increased the activity of superoxide dismutase (SOD), catalase (CAT), β-glucosidase, S-glutathione transferase (GST), oxidoreductive peroxidase (POD), and polyphenol oxidase (PPO) in the aphids, but only on certain days after treatment, which indicates a mild stress in aphid tissues, related to a higher reproduction and changed feeding behavior; aphids moved from the actively growing tips compared to untreated plants. The results of these experiments are discussed in terms of the impact on the future management of this pest.

When bacteria meet mitochondria: The strange case of the tick symbiont Midichloria mitochondrii†

Mitochondria are key eukaryotic organelles that perform several essential functions. Not surprisingly, many intracellular bacteria directly or indirectly target mitochondria, interfering with innate immunity, energy production or apoptosis, to make the host cell a more hospitable niche for bacterial replication. The alphaproteobacterium Midichloria mitochondrii has taken mitochondrial targeting to another level by physically colonising mitochondria, as shown by transmission electron micrographs of bacteria residing in the mitochondrial intermembrane space. This unique localization provokes a number of questions around the mechanisms allowing, and reasons driving intramitochondrial tropism. We suggest possible scenarios that could lead to this peculiar localization and hypothesize potential costs and benefits of mitochondrial colonisation for the bacterium and its host.

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.

Proteome of the Triatomine Digestive Tract: From Catalytic to Immune Pathways; Focusing on Annexin Expression

Rhodnius prolixus, Panstrongylus megistus, Triatoma infestans, and Dipetalogaster maxima are all triatomines and potential vectors of the protozoan Trypanosoma cruzi responsible for human Chagas' disease. Considering that the T. cruzi's cycle occurs inside the triatomine digestive tract (TDT), the analysis of the TDT protein profile is an essential step to understand TDT physiology during T. cruzi infection. To characterize the protein profile of TDT of D. maxima, P. megistus, R. prolixus, and T. infestans, a shotgun liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach was applied in this report. Most proteins were found to be closely related to metabolic pathways such as gluconeogenesis/glycolysis, citrate cycle, fatty acid metabolism, oxidative phosphorylation, but also to the immune system. We annotated this new proteome contribution gathering it with those previously published in accordance with Gene Ontology and KEGG. Enzymes were classified in terms of class, acceptor, and function, while the proteins from the immune system were annotated by reference to the pathways of humoral response, cell cycle regulation, Toll, IMD, JNK, Jak-STAT, and MAPK, as available from the Insect Innate Immunity Database (IIID). These pathways were further subclassified in recognition, signaling, response, coagulation, melanization and none. Finally, phylogenetic affinities and gene expression of annexins were investigated for understanding their role in the protection and homeostasis of intestinal epithelial cells against the inflammation.

Loss of control of the culturable bacteria in the hindgut of Bombyx mori after Cry1Ab ingestion

Bt protein, produced by Bacillus thuringiensis, can bind receptors to destroy the physiological functions of the insect midgut. It is unknown whether Bt can also target the hindgut and influence its defense against fecal bacteria. Here we show that Crystal protein 1Ab (Cry1Ab), a Bt protein, was detected in the larval hindgut contents of Bombyx mori after ingestion of this toxin protein. The number of fecal bacteria that can be inhibited by the hindgut prophenoloxidase-induced melanization was significantly enhanced after oral ingestion of Cry1Ab. Although the hindgut contents became brown, the activity of hindgut phenoloxidase was decreased. LC-MS/MS analysis of the hindgut lumen contents revealed that many new proteins including several proteases were newly secreted. The enhanced secretion of proteases cleaved prophenoloxidase to decrease its activity, including the corresponding activity to inhibit the fecal bacteria. In addition, after ingestion of Cry1Ab, the pylorus (between the midgut and hindgut) could not autonomously contract due to the physical detachment of the acellular cuticle-like membrane from the epidermal cells, which prevented the movement of food from the midgut to the hindgut. Some cells in the cryptonephry of the hindgut became swollen and degraded, possibly due to the presence of Cry1Ab in the hindgut. These findings demonstrate that the inhibition of feces bacteria by the hindgut prophenoloxidase-induced melanization is out of control after Cry1Ab ingestion.

Anopheles metabolic proteins in malaria transmission, prevention and control: a review

The increasing resistance to currently available insecticides in the malaria vector, Anopheles mosquitoes, hampers their use as an effective vector control strategy for the prevention of malaria transmission. Therefore, there is need for new insecticides and/or alternative vector control strategies, the development of which relies on the identification of possible targets in Anopheles. Some known and promising targets for the prevention or control of malaria transmission exist among Anopheles metabolic proteins. This review aims to elucidate the current and potential contribution of Anopheles metabolic proteins to malaria transmission and control. Highlighted are the roles of metabolic proteins as insecticide targets, in blood digestion and immune response as well as their contribution to insecticide resistance and Plasmodium parasite development. Furthermore, strategies by which these metabolic proteins can be utilized for vector control are described. Inhibitors of Anopheles metabolic proteins that are designed based on target specificity can yield insecticides with no significant toxicity to non-target species. These metabolic modulators combined with each other or with synergists, sterilants, and transmission-blocking agents in a single product, can yield potent malaria intervention strategies. These combinations can provide multiple means of controlling the vector. Also, they can help to slow down the development of insecticide resistance. Moreover, some metabolic proteins can be modulated for mosquito population replacement or suppression strategies, which will significantly help to curb malaria transmission.

Candidate stress biomarkers for queen failure diagnostics

Background

Queen failure is a persistent problem in beekeeping operations, but in the absence of overt symptoms it is often difficult, if not impossible, to ascertain the root cause. Stressors like heat-shock, cold-shock, and sublethal pesticide exposure can reduce stored sperm viability and lead to cryptic queen failure. Previously, we suggested candidate protein markers indicating heat-shock in queens. Here, we further investigate these heat-shock markers and test new stressors to identify additional candidate protein markers.

Results

We found that heat-shocking queens for upwards of 1 h at 40 °C was necessary to induce significant changes in the two strongest candidate heat-shock markers, and that relative humidity significantly influenced the degree of activation. In blind heat-shock experiments, we tested the efficiency of these markers at assigning queens to their respective treatment groups and found that one marker was sufficient to correctly assign queens 75% of the time. Finally, we compared cold-shocked queens at 4 °C and pesticide-exposed queens to controls to identify candidate markers for these additional stressors, and compared relative abundances of all markers to queens designated as ‘healthy’ and ‘failing’ by beekeepers. Queens that failed in the field had higher expression of both heat-shock and pesticide protein markers, but not cold-shock markers.

Conclusions

This work offers some of the first steps towards developing molecular diagnostic tools to aid in determining cryptic causes of queen failure. Further work will be necessary to determine how long after the stress event a marker’s expression remains elevated, and how accurate these markers will be for field diagnoses.

Evaluation of antifungal activity of cinnamaldehyde against Cryptococcus neoformans var. grubii

Cryptococcosis is a potentially fatal fungal disease which has aggrandized with the emergence of AIDS and antifungal resistance. The currently used antifungals lack the broad-spectrum activity and result in several toxicities during long treatment regimens. Thus, the present study aims to evaluate the antifungal activity of cinnamaldehyde against Cryptococcus neoformans var. grubii, the etiological agent of the disease. Quantitative and qualitative in vitro fungal susceptibilities were carried out by minimum inhibitory concentration assay, flow cytometric analysis, and confocal microscopy. Micromorphological alterations were studied through scanning electron and light microscopies. "In vivo" antifungal efficacy of cinnamaldehyde was assessed. Cinnamaldehyde showed antifungal activity against C. neoformans in a dose-dependent manner. A concentration of 1.37 mg/mL of cinnamaldehyde was found to be inhibitory and fungicidal while the low concentration (0.68 mg/mL) was found to induce micromorphological changes and formation of giant/titan-like cells in this pathogen. The reparative activity of cinnamaldehyde and its ability to prolong the life even after the advent of cryptococcal meningitis in mice was also noticed. This study suggests potent anti-cryptococcal activity of cinnamaldehyde. Though, it has a couple of limitations like allergy and low bioavailability. However, these problems can be circumvented by developing suitable analogs of the compound. It, therefore, could be used as a therapeutic option against cryptococcosis and cryptococcal meningitis. Moreover, the evaluation of its pharmacokinetic and pharmacodynamic properties is desirable.

Elizabethkingia anophelis: Physiologic and Transcriptomic Responses to Iron Stress

In this study, we investigated the global gene expression responses of Elizabethkingia anophelis to iron fluxes in the midgut of female Anopheles stephensi mosquitoes fed sucrose or blood, and in iron-poor or iron-rich culture conditions. Of 3,686 transcripts revealed by RNAseq technology, 218 were upregulated while 112 were down-regulated under iron-poor conditions. Hemolysin gene expression was significantly repressed when cells were grown under iron-rich or high temperature (37°C) conditions. Furthermore, hemolysin gene expression was down-regulated after a blood meal, indicating that E. anophelis cells responded to excess iron and its associated physiological stress by limiting iron loading. By contrast, genes encoding respiratory chain proteins were up-regulated under iron-rich conditions, allowing these iron-containing proteins to chelate intracellular free iron. In vivo studies showed that growth of E. anophelis cells increased 3-fold in blood-fed mosquitoes over those in sucrose-fed ones. Deletion of siderophore synthesis genes led to impaired cell growth in both iron-rich and iron-poor media. Mutants showed more susceptibility to H2O2 toxicity and less biofilm formation than did wild-type cells. Mosquitoes with E. anophelis experimentally colonized in their guts produced more eggs than did those treated with erythromycin or left unmanipulated, as controls. Results reveal that E. anophelis bacteria respond to varying iron concentration in the mosquito gut, harvest iron while fending off iron-associated stress, contribute to lysis of red blood cells, and positively influence mosquito host fecundity.

Lethal and sublethal toxicity assessment of Bacillus thuringiensis var. israelensis and Beauveria bassiana based bioinsecticides to the aquatic insect Chironomus riparius

Despite being considered environmentally safe, a deeper environmental risk assessment is needed for microbial insecticides; special attention should be devoted to their sublethal toxicity to non-target species. This study evaluated effects of VectoBac® 12AS - VB (based on the bacterium Bacillus thurigiensis var. israelensis) and Naturalis®-L - NL (based on the fungus Beauveria bassiana) on the aquatic insect Chironomus riparius life-history and biochemical responses. Acute tests estimated a 48 h-LC₅₀ (median lethal concentration) of 1.85 μg/L (VB) and 34.7 mg/L (NL). Under sublethal exposure, VB decreased adults' emergence (LOEC - lowest observed effect concentration of 80 ng/L) while NL impaired larval growth (LOEC of 0.32 mg/L) and delayed emergence (LOEC of 2 mg/L for males and 0.8 mg/L for females). Despite not being monotonic, phenoloxidase activity increased (LOEC of 20 ng/L (VB) and 2 mg/L (NL)), suggesting activation of the immune system. There were no indications of oxidative damage nor neurotoxicity. Catalase activity was stimulated with all VB treatments, possibly associated with detoxification of immune response products. Under NL exposure, glutathione-S-transferase activity increased but did not show a dose-dependent response and, total glutathione decreased in the highest concentration. Exposure to both formulations caused the increase in protein content, while carbohydrate and lipids were not altered. This study revealed the susceptibility of C. riparius to VB and NL at concentrations below the ones recommended for field application, with potential population-level effects. These results add important information for the risk assessment of these microbial insecticides in aquatic ecosystems, considering relevant sublethal endpoints and raising concern about the adverse effects on non-target aquatic organisms.

Variation in Tolerance to Parasites Affects Vectorial Capacity of Natural Asian Tiger Mosquito Populations

Globally, diseases transmitted by arthropod vectors, such as mosquitoes, remain a major cause of morbidity and mortality [1]. The defense responses of mosquito and other arthropod vectors against parasites are important for understanding disease transmission dynamics and for the development of novel disease-control strategies. Consequently, the mechanisms by which mosquitoes resist parasitic infection (e.g., immune-mediated killing) have long been studied [2, 3]. However, the ability of mosquitoes to ameliorate the negative fitness consequences of infection through tolerance mechanisms (e.g., tissue repair) has been virtually ignored (but see [4, 5]). Ignoring parasite tolerance is especially taxing in vector biology because unlike resistance, which typically reduces vectorial capacity, tolerance is expected to increase vectorial capacity by reducing parasite-mediated mortality without killing parasites [6], contributing to the recurrent emergence of vector-borne diseases and its stabilization and exacerbation. Despite its importance, there is currently no evidence for the evolution of tolerance in natural mosquito populations. Here, we use a common-garden experimental framework to measure variation in resistance and tolerance to dog heartworm (Dirofilaria immitis) between eight natural Aedes albopictus mosquito populations representing areas of low and high transmission intensity. We find significant inter-population variation in tolerance and elevated tolerance where transmission intensity is high. Additionally, as expected, we find that increased tolerance is associated with higher vectorial capacity. Consequently, our results indicate that high transmission intensity can lead to the evolution of more competent disease vectors, which can feed back to impact disease risk.

Time-of-day of blood-feeding: effects on mosquito life history and malaria transmission

BACKGROUND

Biological rhythms allow organisms to compartmentalise and coordinate behaviours, physiologies, and cellular processes with the predictable daily rhythms of their environment. There is increasing recognition that the biological rhythms of mosquitoes that vector parasites are important for global health. For example, whether perturbations in blood foraging rhythms as a consequence of vector control measures can undermine disease control. To address this, we explore the impacts of altered timing of blood-feeding on mosquito life history traits and malaria transmission.

METHODS

We present three experiments in which Anopheles stephensi mosquitoes were fed in the morning or evening on blood that had different qualities, including: (i) chemical-induced or (ii) Plasmodium chabaudi infection-induced anaemia; (iii) Plasmodium berghei infection but no anaemia; or (iv) stemming from hosts at different times of day. We then compared whether time-of-day variation in blood meal characteristics influences mosquito fitness proxies relating to survival and reproduction, and malaria transmission proxies.

RESULTS

Mosquito lifespan is not influenced by the time-of-day they received a blood meal, but several reproductive metrics are affected, depending on other blood characteristics. Overall, our data suggest that receiving a blood meal in the morning makes mosquitoes more likely to lay eggs, lay slightly sooner and have a larger clutch size. In keeping with previous work, P. berghei infection reduces mosquito lifespan and the likelihood of laying eggs, but time-of-day of blood-feeding does not impact upon these metrics nor on transmission of this parasite.

CONCLUSION

The time-of-day of blood-feeding does not appear to have major consequences for mosquito fitness or transmission of asynchronous malaria species. If our results from a laboratory colony of mosquitoes living in benign conditions hold for wild mosquitoes, it suggests that mosquitoes have sufficient flexibility in their physiology to cope with changes in biting time induced by evading insecticide-treated bed nets. Future work should consider the impact of multiple feeding cycles and the abiotic stresses imposed by the need to forage for blood during times of day when hosts are not protected by bed nets.

Induction of endoplasmic reticulum stress might be responsible for defective autophagy in cadmium-induced prostate carcinogenesis

Earlier, we reported that chronic cadmium (Cd)-exposure to prostate epithelial (RWPE-1) cells causes defective autophagy, which leads to the transformation of a malignant phenotype in both in vitro and in vivo models. However, the upstream events responsible for defective autophagy are yet to be delineated. The present study suggests that chronic Cd exposure induces endoplasmic reticulum (ER) stress that triggers the phosphorylation of stress transducers [protein kinase R-like ER Kinase- (PERK), eukaryotic translation initiation factor 2-alpha- (eIF2-α) and Activating Transcription Factor 4 -(ATF-4)], resulting in defective autophagy that protects Cd-exposed RWPE-1 cells. On the other hand, inhibition of the ATF4 stress inducer by siRNA blocked the Cd-induced defective autophagy in transforming cells. While dissecting the upstream activators of ER stress, we found that increased expression of reactive oxygen species (ROS) is responsible for ER stress in Cd-exposed RWPE-1 cells. Overexpression of antioxidants (SOD1/SOD2) mitigates Cd-induced ROS that results in inhibition of ER stress and autophagy in prostate epithelial cells. These results suggest that the induction of ROS and subsequent ER stress are responsible for defective autophagy in Cd-induced transformation in prostate epithelial cells.

Influence of blood meal and age of mosquitoes on susceptibility to pyrethroids in Anopheles gambiae from Western Kenya

BACKGROUND

Physiological characteristics (age and blood feeding status) of malaria vectors can influence their susceptibility to the current vector control tools that target their feeding and resting behaviour. To ensure the sustainability of the current and future vector control tools an understanding of how physiological characteristics may contribute to insecticide tolerance in the field is fundamental for shaping resistance management strategies and vector control tools. The aim of this study was to determine whether blood meal and mosquito age affect pyrethroid tolerance in field-collected Anopheles gambiae from western Kenya.

METHODS

Wild mosquito larvae were reared to adulthood alongside the pyrethroid-susceptible Kisumu strain. Adult females from the two populations were monitored for deltamethrin resistance when they were young at 2-5 days old and older 14-16 days old and whether fed or unfed for each age group. Metabolic assays were also performed to determine the level of detoxification enzymes. Mosquito specimens were further identified to species level using the polymerase chain reaction (PCR) method.

RESULTS

Anopheles gambiae sensu stricto was the predominant species comprising 96% of specimens and 2.75% Anopheles arabiensis. Bioassay results showed reduced pyrethroid induced mortality with younger mosquitoes compared to older ones (mortality rates 83% vs. 98%), independently of their feeding status. Reduced mortality was recorded with younger females of which were fed compared to their unfed counterparts of the same age with a mortality rate of 35.5% vs. 83%. Older blood-fed females showed reduced susceptibility after exposure when compared to unfed females of the same age (mortality rates 86% vs. 98%). For the Kisumu susceptible population, mortality was straight 100% regardless of age and blood feeding status. Blood feeding status and mosquito age had an effect on enzyme levels in both populations, with blood fed individuals showing higher enzyme elevations compared to their unfed counterparts (P < 0.0001). The interaction between mosquito age and blood fed status had significant effect on mosquito mortality.

CONCLUSION

The results showed that mosquito age and blood feeding status confers increased tolerance to insecticides as blood feeding may be playing an important role in the toxicity of deltamethrin, allowing mosquitoes to rest on insecticide-treated materials despite treatment. These may have implications for the sustained efficacy of indoor residual spraying and insecticide-treated nets based control programmes that target indoor resting female mosquitoes of various gonotrophic status.

Redox state affects fecundity and insecticide susceptibility in Anopheles gambiae

Redox reactions play a central role in the metabolism of an organism. It is vital to maintain redox homeostasis in response to the fluctuation of redox shift in various biological contexts. NADPH-dependent reducing capacity is one of the key factors contributing to the redox homeostasis. To understand the redox capacity and its impact on mosquito fecundity and susceptibility to insecticides in Anopheles gambiae, we examined the dynamics of elevated oxidative state via induction by paraquat (PQ) and the inhibition of NADPH regeneration by 6-aminonicotinamide (6AN). In naïve conditions, inherent oxidative capacity varies between individuals, as measured by GSSG/GSH ratio. The high GSSG/GSH ratio was negatively correlated with fecundity. Both PQ and 6AN feeding increased GSSG/GSH ratio and elevated protein carbonylation, a marker of oxidative damage. Both pro-oxidants lowered egg production. Co-feeding the pro-oxidants with antioxidant lycopene attenuated the adverse effects on fecundity, implying that oxidative stress was the cause of this phenotype. Pre-feeding with 6AN increased insecticide susceptibility in DDT resistant mosquitoes. These results indicate that oxidative state is delicate in mosquitoes, manipulation of NADPH pool may adversely affect fecundity and insecticide detoxification capacity. This knowledge can be exploited to develop novel vector control strategies targeting fecundity and insecticide resistance.

Heme crystallization in a Chagas disease vector acts as a redox-protective mechanism to allow insect reproduction and parasite infection

Heme crystallization as hemozoin represents the dominant mechanism of heme disposal in blood feeding triatomine insect vectors of the Chagas disease. The absence of drugs or vaccine for the Chagas disease causative agent, the parasite Trypanosoma cruzi, makes the control of vector population the best available strategy to limit disease spread. Although heme and redox homeostasis regulation is critical for both triatomine insects and T. cruzi, the physiological relevance of hemozoin for these organisms remains unknown. Here, we demonstrate that selective blockage of heme crystallization in vivo by the antimalarial drug quinidine, caused systemic heme overload and redox imbalance in distinct insect tissues, assessed by spectrophotometry and fluorescence microscopy. Quinidine treatment activated compensatory defensive heme-scavenging mechanisms to cope with excessive heme, as revealed by biochemical hemolymph analyses, and fat body gene expression. Importantly, egg production, oviposition, and total T. cruzi parasite counts in R. prolixus were significantly reduced by quinidine treatment. These effects were reverted by oral supplementation with the major insect antioxidant urate. Altogether, these data underscore the importance of heme crystallization as the main redox regulator for triatomine vectors, indicating the dual role of hemozoin as a protective mechanism to allow insect fertility, and T. cruzi life-cycle. Thus, targeting heme crystallization in insect vectors represents an innovative way for Chagas disease control, by reducing simultaneously triatomine reproduction and T. cruzi transmission.

Chagas disease is a fatal illness caused by Trypanosoma cruzi parasites, which are transmitted by blood sucking triatomine insect vectors. Although blood is a natural food source for these insects, its digestion releases toxic products, which poses a dietary challenge for both triatomine insects and trypanosomes. To overcome this, triatomines eliminate these toxic blood products by a unique process of heme crystallization into hemozoin that take place in their digestive tract. Here we describe that this detoxification process represents the major mechanism for redox balance control, and is necessary to allow triatomine insect reproduction, and Trypanosoma cruzi infection. Disruption of heme crystallization in triatomine insects thus represents a new venue for Chagas disease control, by targeting at the same time insect reproduction and parasite transmission.

Rival seminal fluid induces enhanced sperm motility in a polyandrous ant

Background

Promiscuous mating and sperm competition often induce arms races between the sexes with detrimental outcomes for females. However, ants with multiply-inseminated queens have only a single time-window for sperm competition and queens are predicted to gain control over the outcome of sperm storage quickly. The seminal fluid of Acromyrmex leaf-cutting ants reduces the viability of rival sperm, but how confrontations between unrelated ejaculates affect sperm storage remains unknown.

Results

We investigated the effects of ejaculate admixture on sperm motility in A. echinatior and found that the proportion of motile spermatozoa, sperm swimming speed, and linearity of sperm movement increased when rival ejaculates were mixed in vitro. Major effects induced by the seminal fluid of rival males were of similar magnitude to those generated by queen reproductive tract secretions, whereas own seminal fluid induced lower sperm activation levels.

Conclusions

Our results suggest that ant sperm respond via a self–non-self recognition mechanism to similar or shared molecules expressed in the reproductive secretions of both sexes. Lower sperm motility in the presence of own seminal fluid indicates that enhanced motility is costly and may trade-off with sperm viability during sperm storage, consistent with studies in vertebrates. Our results imply that ant spermatozoa have evolved to adjust their energetic expenditure during insemination depending on the perceived level of sperm competition.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1144-y) contains supplementary material, which is available to authorized users.

Catalase and its mysteries

Catalase is one of the firsts in every realm of biological sciences. At the same time it also has a number of unusual features. It has one of the highest turnover numbers of all enzymes. It is essential for neutralizing the noxious hydrogen peroxide both in the nature and the various industries such as dairy, textile and pharmaceutics. It also has the merit of being one of the first protein crystals to be isolated. Ironically its three-dimensional structure was discerned some forty years later. However through the times this senile enzyme has continued to intrigue the scientists by surprising facts and phenomena, such as peculiar interweaving of subunits and remarkable thermal stability. It is also known for suicide inactivation by its own substrate. Catalase is known to be implicated in various medical scenarios and its levels have served as a marker in that capacity. It has even been incorporated into several pharmaceuticals. This review strives to clarify these perspectives. It also draws attention to the biophysical contributions offered by thermodynamics and kinetics in these discoveries. The ultimate aim of this review, however, is to state that the venerable catalase will continue to bewilder us with its mysteries well into the twenty-first century.

Molecular Mechanisms and Emerging Therapeutic Targets of Triple-Negative Breast Cancer Metastasis

Breast cancer represents a highly heterogeneous disease comprised by several subtypes with distinct histological features, underlying molecular etiology and clinical behaviors. It is widely accepted that triple-negative breast cancer (TNBC) is one of the most aggressive subtypes, often associated with poor patient outcome due to the development of metastases in secondary organs, such as the lungs, brain, and bone. The molecular complexity of the metastatic process in combination with the lack of effective targeted therapies for TNBC metastasis have fostered significant research efforts during the past few years to identify molecular “drivers” of this lethal cascade. In this review, the most current and important findings on TNBC metastasis, as well as its closely associated basal-like subtype, including metastasis-promoting or suppressor genes and aberrantly regulated signaling pathways at specific stages of the metastatic cascade are being discussed. Finally, the most promising therapeutic approaches and novel strategies emerging from these molecular targets that could potentially be clinically applied in the near future are being highlighted.

Interorgan Molecular Communication Strategies of "Local" and "Systemic" Innate Immune Responses in Mosquito Anopheles stephensi

Mosquitoes that transmit many deadly infectious diseases also need to keep fighting against many microbial infections. Constitutive expression of multiple antimicrobial peptides (AMPs) in almost all body tissues is believed to facilitate the effective management of these local infections. When any infection breaches the local barrier, AMPs are induced rapidly in non-target tissues such as hemocytes (HCs) and establish their co-ordination with systemic immune effectors to clear off the body infection. But how interorgan immune communication is managed during local and systemic infections remain largely unknown. To understand this interorgan molecular relationship, we identified, extensively profiled and compared the expression of AMPs in three important mosquito tissues viz. midgut, fat body (FB), and HCs. dsRNA-mediated AMPs silencing suggests that mosquito tissues are able to manage an optimal expression of AMPs at the physiological level. We also examined the possible contribution of two important immune regulator genes relish (REL) and nitric oxide synthase, controlling AMPs expression in these tissues during local or systemic infections. We show that each tissue has a unique ability to respond to local/systemic challenges, but HCs are more specialized to recognize and discriminate-specific antigens than gut and FB. Our investigation also revealed that both REL and NO participate in the overall management of the interorgan immune responses, but at the same time each tissue also has its own ability to maintain the interorgan flow of signals. In our knowledge, this is the first large-scale study examining the interorgan immune relationship in the mosquito.

Long-Lived Termite Queens Exhibit High Cu/Zn-Superoxide Dismutase Activity

In most organisms, superoxide dismutases (SODs) are among the most effective antioxidant enzymes that regulate the reactive oxygen species (ROS) generated by oxidative energy metabolism. ROS are considered main proximate causes of aging. However, it remains unclear if SOD activities are associated with organismal longevity. The queens of eusocial insects, such as termites, ants, and honeybees, exhibit extraordinary longevity in comparison with the nonreproductive castes, such as workers. Therefore, the queens are promising candidates to study the underlying mechanisms of aging. Here, we found that queens have higher Cu/Zn-SOD activity than nonreproductive individuals of the termite Reticulitermes speratus. We identified three Cu/Zn-SOD sequences and one Mn-SOD sequence by RNA sequencing in R. speratus. Although the queens showed higher Cu/Zn-SOD activity than the nonreproductive individuals, there were no differences in their expression levels of the Cu/Zn-SOD genes RsSOD1 and RsSOD3A. Copper (Cu2+ and Cu+) is an essential cofactor for Cu/Zn-SOD enzyme activity, and the queens had higher concentrations of copper than the workers. These results suggest that the high Cu/Zn-SOD activity of termite queens is related to their high levels of the cofactor rather than gene expression. This study highlights that Cu/Zn-SOD activity contributes to extraordinary longevity in termites.

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.

Loss of MKP-5 promotes myofiber survival by activating STAT3/Bcl-2 signaling during regenerative myogenesis

BACKGROUND

The mitogen-activated protein kinases (MAPKs) have been shown to be involved in regulating myofiber survival. In skeletal muscle, p38 MAPK and JNK are negatively regulated by MAPK phosphatase-5 (MKP-5). During muscle regeneration, MKP-5 is downregulated, thereby promoting p38 MAPK/JNK signaling, and subsequent repair of damaged muscle. Mice lacking MKP-5 expression exhibit enhanced regenerative myogenesis. However, the effect of MKP-5 on myofiber survival during regeneration is unclear.

METHODS

To investigate whether MKP-5 is involved in myofiber survival, skeletal muscle injury was induced by cardiotoxin injection, and the effects on apoptosis were assessed by TUNEL assay in wild type and MKP-5-deficient mice. The contribution of MKP-5 to apoptotic signaling and its link to this pathway through mitochondrial function were determined in regenerating skeletal muscle of MKP-5-deficient mice.

RESULTS

We found that loss of MKP-5 in skeletal muscle resulted in improved myofiber survival. In response to skeletal muscle injury, loss of MKP-5 decreased activation of the mitochondrial apoptotic pathway involving the signal transducer and activator of transcription 3 (STAT3) and increased expression of the anti-apoptotic transcription factor Bcl-2. Skeletal muscle of MKP-5-deficient mice also exhibited an improved anti-oxidant capacity as a result of increased expression of catalase further contributing to myofiber survival by attenuating oxidative damage.

CONCLUSIONS

Taken together, these findings suggest that MKP-5 coordinates skeletal muscle regeneration by regulating mitochondria-mediated apoptosis. MKP-5 negatively regulates apoptotic signaling, and during regeneration, MKP-5 downregulation contributes to the restoration of myofiber survival. Finally, these results suggest that MKP-5 inhibition may serve as an important therapeutic target for the preservation of skeletal muscle survival in degenerative muscle diseases.

Senecio brasiliensis impairs eclosion rate and induces apoptotic cell death in larvae of Drosophila melanogaster

Senecio brasilienis (Spreng) Less., is a species native from Brazil, popularly known as "Maria mole", and known to induce hepatotoxicity due to its high content of Pyrrolizidine alkaloids. Despite its toxicity, this plant is widely used in Brazilian folk medicine. Considering the antagonizing effects described for S. brasiliensis, we describe here molecular markers involved in the toxicity of hydroalcoholic extract from leaves of S. brasiliensis (HESB) in Drosophila melanogaster. Phytochemical analysis of HESB revealed the presence of phenolic acids and flavonoids. A significant antioxidant potential against ABTS⁺ and DPPH radical was found in parallel. Ingestion of extract did not alter the survival and locomotor activity of adult flies. However when ingested along the larval developmental phase, the eclosion rate of flies was interrupted at higher concentration of extract. To comprehend this phenomenon several analysis were conducted in larvae. HESB stimulated activity of antioxidant enzymes SOD and GST, and increased GSH/GSSG ratio and ROS production. Additionally, HESB caused a significant decrease of cell viability. The mRNA expression of Nrf2, TrxR, CAT, Drice and Dilp6 were also significantly up-regulated. HESB caused significant decrease on the phosphorylation of MAPKs and AKT. In parallel, PARP cleavage and caspases 3/7 activity were stimulated. In addition, glucose, glycogen and triglycerides levels were decreased. Taken together our study depicts a disruption in the eclosion of D. melanogaster possibly attributed to the inhibition of kinases implied in developmental process, energetic demand and induction of apoptotic cell death process.

Thermotolerance, oxidative stress, apoptosis, heat-shock proteins and damages to reproductive cells of insecticide-susceptible and -resistant strains of the diamondback moth Plutella xylostella

In this study, we investigated thermotolerance, several physiological responses and damage to reproductive cells in chlorpyrifos-resistant (Rc) and -susceptible (Sm) strains of the diamondback moth, Plutella xylostella subjected to heat stress. The chlorpyrifos resistance of these strains was mediated by a modified acetylcholinesterase encoded by an allele, ace1R, of the ace1 gene. Adults of the Rc strain were less heat resistant than those of the Sm strain; they also had lower levels of enzymatic activity against oxidative damage, higher reactive oxygen species contents, weaker upregulation of two heat shock protein (hsp) genes (hsp69s and hsp20), and stronger upregulation of two apoptotic genes (caspase-7 and -9). The damage to sperm and ovary cells was greater in Rc adults than in Sm adults and was temperature sensitive. The lower fitness of the resistant strain, compared with the susceptible strain, is probably due to higher levels of oxidative stress and apoptosis, which also have deleterious effects on several life history traits. The greater injury observed in conditions of heat stress may be due to both the stronger upregulation of caspase genes and weaker upregulation of hsp genes in resistant than in susceptible individuals.

Expression and Enzyme Activity of Catalase in Chilo suppressalis (Lepidoptera: Crambidae) Is Responsive to Environmental Stresses

Catalase (CAT) is an important antioxidant enzyme that protects organisms against oxidative stresses by eliminating hydrogen peroxide. In this study, we cloned and characterized a full-length cDNA of CAT from Chilo suppressalis (CsCAT) and examined the influence of environmental stresses on CsCAT expression and enzyme activity. The cDNA contains a 1659-bp open reading frame encoding a polypeptide of 553 amino acids most closely related (90.14%) to Papilio polytes catalases. The CsCAT was expressed in all developmental stages with the highest expression in the fat body, and the CsCAT enzyme activity closely mirrored its observed mRNA expression patterns. The CsCAT mRNA was up-regulated when the larvae were exposed to high temperature (≥30 °C), insecticides (abamectin and chlorantraniliprole), chemicals (H2O2, CHP, CdCl2, and CuSO4), and a dead-end trap plant (vetiver grass), and the CsCAT enzyme activity again mirrored the observed CsCAT expression patterns. These results suggest that up-regulation of CsCAT may enhance the defense response of C. suppressalis by weakening the effects of environmental stresses, and provide insight into the role of CsCAT during development of C. suppressalis.

Catalase is a determinant of the colonization and transovarial transmission of Rickettsia parkeri in the Gulf Coast tick Amblyomma maculatum

The Gulf Coast tick (Amblyomma maculatum) has evolved as a competent vector of the spotted-fever group rickettsia, Rickettsia parkeri. In this study, the functional role of catalase, an enzyme responsible for the degradation of toxic hydrogen peroxide, in the colonization of the tick vector by R. parkeri and transovarial transmission of this pathogen to the next tick generation, was investigated. Catalase gene (CAT) expression in midgut, salivary glands and ovarian tissues exhibited a 2-11-fold increase in transcription level upon R. parkeri infection. Depletion of CAT transcripts using an RNA-interference approach significantly reduced R. parkeri infection levels in midgut and salivary gland tissues by 53-63%. The role of CAT in transovarial transmission of R. parkeri was confirmed by simultaneously blocking the transcript and the enzyme by injecting double-stranded RNA for CAT and a catalase inhibitor (3-amino-1,2,4-triazole) into gravid females. Simultaneous inhibition of the CAT transcript and the enzyme significantly reduced the egg conversion ratio with a 44% reduction of R. parkeri transovarial transmission. These data suggest that catalase is required for rickettsial colonization of the tick vector and transovarial transmission to the next generation.

Early plant defence against insect attack: involvement of reactive oxygen species in plant responses to insect egg deposition

Pinus sylvestris responds to insect egg deposition by ROS accumulation linked with reduced activity of the ROS scavenger catalase. Egg mortality in needles with hypersensitive response (HR)-like symptoms is enhanced. Aggressive reactive oxygen species (ROS) play an important role in plant defence against biotic stressors, including herbivorous insects. Plants may even generate ROS in response to insect eggs, thus effectively fighting against future larval herbivory. However, so far nothing is known on how ROS-mediated plant defence against insect eggs is enzymatically regulated. Neither do we know how insects cope with egg-induced plant ROS. We addressed these gaps of knowledge by studying the activities of ROS-related enzymes in Pinus sylvestris deposited with eggs of the herbivorous sawfly Diprion pini. This species cuts a slit into pine needles and inserts its eggs into the needle tissue. About a quarter of egg-deposited needles show chlorotic tissue at the oviposition sites, indicating hypersensitive response-like direct defence responses resulting in reduced larval hatching from eggs. Hydrogen peroxide and peroxidase sensitive staining of sections of egg-deposited pine needles revealed the presence of hydrogen peroxide and peroxidase activity in needle tissue close to the eggs. Activity of ROS-producing NADPH-oxidase did not increase after egg deposition. However, the activity of the ROS-detoxifying enzyme catalase decreased after egg deposition and ovipositional wounding of needles. These results show that local ROS accumulation at the oviposition site is not caused by increased NADPH-oxidase activity, but reduced activity of pine needle catalase may contribute to it. However, our data suggest that pine sawflies can counteract the egg deposition-induced hydrogen peroxide accumulation in pine needles by high catalase activity in their oviduct secretion which is released with the eggs into pine tissue.

Metagenomic Sequencing of Diamondback Moth Gut Microbiome Unveils Key Holobiont Adaptations for Herbivory

Herbivore specialists adapt to feed on a specific group of host plants by evolving various mechanisms to respond to plant defenses. Insects also possess complex gut microbiotas but their potential role in adaptation is poorly understood. Our previous study of the genome of diamondback moth, Plutella xylostella, revealed an intrinsic capacity to detoxify plant defense compounds, which is an important factor in its success as a pest. Here we expand on that work with a complete taxonomic and functional profile of the P. xylostella gut microbiota obtained by metagenomic sequencing. Gene enrichment in the metagenome, accompanied by functional identification, revealed an important role of specific gut bacteria in the breakdown of plant cell walls, detoxification of plant phenolics, and synthesis of amino acids. Microbes participating in these pathways mainly belonged to three highly abundant bacteria: Enterobacter cloacae, Enterobacter asburiae, and Carnobacterium maltaromaticum. Results show that while the gut microbial community may be complex, a small number of functionally active species can be disproportionally important. The presence of specific enzymes in the microbiota community, such as supporting amino acid synthesis, digestion and detoxification functions, demonstrates the beneficial interactions between P. xylostella and its gut microbiota. These interactions can be potential targets for manipulation to provide novel pest management approaches.