Marcela Figueiredo - Academia.edu (original) (raw)

Papers by Marcela Figueiredo

Anais da Academia Brasileira de Ciências, 2022

Rhodnius prolixus interaction with Trypanosoma rangeli: modulation of the immune system and micro... more Rhodnius prolixus interaction with Trypanosoma rangeli: modulation of the immune system and microbiota population

Journal of Insect Physiology, 2017

Methods in molecular biology

RNA interference (RNAi) has emerged as a widely used approach for reverse genetic analysis in euk... more RNA interference (RNAi) has emerged as a widely used approach for reverse genetic analysis in eukaryotes. In insects, RNAi also has an application in the control of insect pests. Several methods have been developed for delivery of interfering RNA in insects, with varying outcomes for different species. Here we describe how a bacterial symbiont can be exploited for continuous synthesis of interfering double-stranded RNA (dsRNA) in its insect host. This approach, termed symbiont-mediated RNAi (SMR), can overcome problems associated with instability of dietary dsRNA due to action of salivary or foregut nucleases. As insects do not possess RNA-dependent RNA polymerase activity that can amplify and extend RNAi in other organisms, SMR also offers the possibility of long-term systemic RNAi not afforded by single applications of dsRNA to insects by other delivery methods. Here, we describe how SMR can be applied in a globally distributed agricultural pest species, western flower thrips (Fra...

© 2009 Garcia et al; licensee BioMed Central Ltd. This is an Open Access article distributed unde... more © 2009 Garcia et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License

Developmental and comparative immunology, 2020

Rhodnius prolixus is an insect vector of two flagellate parasites, Trypanosoma rangeli and Trypan... more Rhodnius prolixus is an insect vector of two flagellate parasites, Trypanosoma rangeli and Trypanosoma cruzi, the latter being the causative agent of Chagas disease in Latin America. The R. prolixus neuroendocrine system regulates the synthesis of the steroid hormone ecdysone, which is essential for not only development and molting but also insect immunity. Knowledge for how this modulates R. prolixus midgut immune responses is essential for understanding interactions between the vector, its parasites and symbiotic microbes. In the present work, we evaluated the effects of ecdysone inhibition on R. prolixus humoral immunity and homeostasis with its microbiota, using the triterpenoid natural product, azadirachtin. Our results demonstrated that azadirachtin promoted a fast and lasting inhibitory effect on expression of both RpRelish, a nuclear factor kappa B transcription factor (NF-kB) component of the IMD pathway, and several antimicrobial peptide (AMP) genes. On the other hand, RpD...

International Journal of Molecular Sciences

Chagas disease is a human infectious disease caused by Trypanosoma cruzi and can be transmitted b... more Chagas disease is a human infectious disease caused by Trypanosoma cruzi and can be transmitted by triatomine vectors, such as Rhodnius prolixus. One limiting factor for T. cruzi development is the composition of the bacterial gut microbiota in the triatomine. Herein, we analyzed the humoral immune responses of R. prolixus nymphs treated with antibiotics and subsequently recolonized with either Serratia marcescens or Rhodococcus rhodnii. The treatment with antibiotics reduced the bacterial load in the digestive tract, and the recolonization with each bacterium was successfully detected seven days after treatment. The antibiotic-treated insects, recolonized with S. marcescens, presented reduced antibacterial activity against Staphylococcus aureus and phenoloxidase activity in hemolymph, and lower nitric oxide synthase (NOS) and higher defensin C gene (DefC) gene expression in the fat body. These insects also presented a higher expression of DefC, lower prolixicin (Prol), and lower NO...

Background: Schistosomiasis is a neglected tropical disease and affects over 200 million people w... more Background: Schistosomiasis is a neglected tropical disease and affects over 200 million people worldwide. The snail Biomphalaria glabrata is one of the intermediate hosts of S. mansoni. The aim of this work was to verify the action of Euphorbia milii var. hislopii latex in the hemocytes profile and histopathology of B. glabrata infected by S. mansoni. Methods: Uninfected and infected snails were exposed to sublethal concentrations of E. milii latex for 24 hours (1.0 mg/l less than the LC 50) and after this time were analysed. Results: The survival rate was 88.5% for the uninfected snails and 66.6% for the infected and exposed snails. In the snails infected by S. mansoni , the exposure to E. milii latex promoted proliferation of hemocytes in the tentacles, mantle, digestive gland, kidney and ovotestis. In the digestive gland and the kidney, granulomatous reactions occurred around the sporocysts and caused their destruction. Proliferation of hemocytes in the kidney and digestive gland and edema in the mantle area were also observed in the uninfected and exposed snails. The number of circulating hemocytes from the group infected and exposed to E. milii latex was significantly higher than in the other groups. Three types of hemocytes were found: hyalinocytes, granulocytes and blast-like cells, and in all the groups the proportion of hyalinocytes was higher than the other types. There was no significant difference among the cell types and the different groups analyzed. Conclusions: We conclude that the sublethal concentration of E. milii latex influenced the cellular immune response of the susceptible B. glabrata strain to infection by S. mansoni , promoting the destruction of parasites.

Memórias do Instituto Oswaldo Cruz, 2017

The aim of this study was to identify the composition of the essential oil from leaves of Lippia ... more The aim of this study was to identify the composition of the essential oil from leaves of Lippia sidoides (EOLS), a typical shrub commonly found in the dry northeast of Brazil, popularly known as "alecrim-pimenta". Additionally, we investigated the nymphicidal, ovicidal, phagoinhibitory and excretion effects of EOLS, its major constituent thymol and its isomer carvacrol, on fourth instar nymphs and eggs of Rhodnius prolixus, the Chagas' disease vector. The nymphicidal and ovicidal activity of thymol, carvacrol, and EOLS was assessed by tests using impregnated Petri dishes. The lethal concentration values (LC 50) for EOLS, carvacrol, and thymol were 54.48, 32.98, and 9.38 mg/cm 2 , respectively. The ovicidal test showed that both carvacrol and thymol (50 mg/cm 2) inhibited hatching (50% and 23.3%, respectively), while treatments with 10 mg/cm 2 or 50 mg/cm 2 EOLS did not affect the hatching rate at all (80% and 90%, respectively). We observed an anti-feeding effect in insects fed with blood containing natural products at the higher concentrations (100 µg/ mL). Finally, excretion rate was affected by EOLS and carvacrol, but not by thymol. These findings offer novel insights into basic physiological processes that make the tested natural compounds interesting candidates for new types of insecticides.

Parasites & Vectors, 2015

Background: Trypanosoma rangeli is a protozoan that infects a variety of mammalian hosts, includi... more Background: Trypanosoma rangeli is a protozoan that infects a variety of mammalian hosts, including humans. Its main insect vector is Rhodnius prolixus and is found in several Latin American countries. The R. prolixus vector competence depends on the T. rangeli strain and the molecular interactions, as well as the insect's immune responses in the gut and haemocoel. This work focuses on the modulation of the humoral immune responses of the midgut of R. prolixus infected with T. rangeli Macias strain, considering the influence of the parasite on the intestinal microbiota. Methods: The population density of T. rangeli Macias strain was analysed in different R. prolixus midgut compartments in long and short-term experiments. Cultivable and non-cultivable midgut bacteria were investigated by colony forming unit (CFU) assays and by 454 pyrosequencing of the 16S rRNA gene, respectively. The modulation of R. prolixus immune responses was studied by analysis of the antimicrobial activity in vitro against different bacteria using turbidimetric tests, the abundance of mRNAs encoding antimicrobial peptides (AMPs) defensin (DefA, DefB, DefC), prolixicin (Prol) and lysozymes (LysA, LysB) by RT-PCR and analysis of the phenoloxidase (PO) activity. Results: Our results showed that T. rangeli successfully colonized R. prolixus midgut altering the microbiota population and the immune responses as follows: 1-reduced cultivable midgut bacteria; 2-decreased the number of sequences of the Enterococcaceae but increased those of the Burkholderiaceae family; the families Nocardiaceae, Enterobacteriaceae and Mycobacteriaceae encountered in control and infected insects remained the same; 3-enhanced midgut antibacterial activities against Serratia marcescens and Staphylococcus aureus; 4-downregulated LysB and Prol mRNA levels; altered DefB, DefC and LysA depending on the infection (short and longterm); 5-decreased PO activity. Conclusion: Our findings suggest that T. rangeli Macias strain modulates R. prolixus immune system and modifies the natural microbiota composition.

Spectrochimica Acta Part B: Atomic Spectroscopy, 2012

In recent years, the effects of pollution on the health of humans and other vertebrates were exte... more In recent years, the effects of pollution on the health of humans and other vertebrates were extensively studied. However, the effects on some invertebrates are comparatively unknown. Recent studies have demonstrated that toxic metals interfere with the reproduction, development and immune defenses of some terrestrial and marine invertebrates. Some environmental conditions including pollution produce chronic and acute effects on different animal's organs and systems. In this work, we investigated changes in the concentrations of Cl, K, Ca, Fe and Zn in Rhodnius prolixus as insect model. The elements were quantified using urine and hemolymph samples collected on different days after feeding the insects with blood containing HgCl 2. The synchrotron radiation total reflection X-ray fluorescence measurements were carried at the X-ray fluorescence beamline facility in Brazilian Synchrotron Light Laboratory. The observation reveals that the calcium level was higher in the hemolymph than in urine. On the other hand, the urine collected from insects treated with HgCl 2 showed higher level of Cl than hemolymph samples. Ca, Fe and Zn concentrations decrease drastically in urine samples collected after 2 days of HgCl 2 treatment. The regulation of triatomines excretion was discussed pointing out the importance of trace elements.

Journal of Insect Physiology, 2006

In this paper we investigate in vivo and in vitro effects of orally administered azadirachtin and... more In this paper we investigate in vivo and in vitro effects of orally administered azadirachtin and ecdysone on the phagocytic responses of Rhodnius prolixus 5th-instar larval hemocytes to the yeast Saccharomyces cerevisiae. Groups of insects fed non-treated blood (control) and insects that received azadirachtin plus ecdysone in the blood meal were inoculated with yeast cells in the hemocele. The injected yeast cells disappeared rapidly from the hemolymph, being removed completely by 90min after inoculation. In the insects treated only with azadirachtin the clearance of free yeast circulating particles was significantly delayed compared to the two previously mentioned groups. It was demonstrated that the binding of yeast cells to hemocytes was reduced in the insects treated only with azadirachtin in comparison to both non-treated control and azadirachtin plus ecdysone-treated groups. Phagocytosis occurred when yeast cells were added to hemocyte monolayers prepared with hemolymph from blood fed insects, treated or not with azadirachtin plus ecdysone, so that yeast cells were rapidly bound to hemocytes and internalized in high numbers. By contrast, insects treated with azadirachtin exhibited a drastic reduction in the quantity of yeast cell-hemocyte binding and subsequent internalization. In all groups, the hemocytes attached to the glass slides were predominantly plasmatocytes. The magnitude and speed of the cellular response suggests that hemocyte phagocytosis is one of the main driving forces for the clearance of free circulating yeast cells from the hemolymph. We propose that ecdysone modulates phagocytosis in R. prolixus larvae, and that this effect is antagonized by azadirachtin.

Journal of Insect Physiology, 2008

A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (... more A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (Solanaceae), on the immune reactions of R. prolixus was carried out. Ecdysis and mortality were not affected by treatment with physalins B, D, F or G (1-10 mg/ml of blood meal). R. prolixus larvae fed with blood containing physalins and inoculated with 1 ml of Enterobacter cloacae b12 (5 Â 10 3 /insect) exhibited mortality rates three times higher than controls. The insects treated with physalin B, and F (1 mg/ml) and inoculated with E. cloacae b12 showed significant differences on lysozyme activity in the hemolymph compared to untreated insects. Furthermore, physalin D (1 mg/ml) significantly reduced the antibacterial activity. Concerning cellular immune reactions, all insects treated with physalins (1 mg/ml), exhibited drastic reductions in the quantity of yeast cell-hemocyte binding and subsequent internalization. Insects inoculated with bacteria and treated with physalins B, F and G showed reductions of microaggregate formation but physalin D did not. Physalins B and F also reduced total hemocyte count in the hemolymph. These results suggest that, in different ways, probably due to their different chemical structures, physalin B, D, F and G are immunomodulatory substances for the bloodsucking insect, R. prolixus.

Journal of Insect Physiology, 2008

The hemocytes phagocytosis in response to microorganisms may play an important role in the cellul... more The hemocytes phagocytosis in response to microorganisms may play an important role in the cellular immune responses of insects. Here, we have evaluated the effects of the platelet-activating factor (PAF) and eicosanoids in the phagocytosis of hemocyte monolayers of Rhodnius prolixus to the yeast Saccharomyces cerevisiae. Experiments showed that the phagocytosis of yeast cells by Rhodnius hemocytes is very efficient in both controls and cells treated with PAF and arachidonic acid. Phagocytosis of yeast particles is significantly blocked when the specific phopholipase A 2 inhibitor, dexamethasone, is applied on the hemocytes. By contrast, dexamethasone-pretreated hemocyte monolayers exhibit a drastic increase in the quantity of yeast cell-hemocyte internalization when the cells are treated by arachidonic acid. In addition, phagocytosis presents significant reduction in hemocyte monolayers treated with a specific PAF receptor antagonist, WEB 2086. Nevertheless, inhibition of phagocytosis with WEB 2086 is counteracted by the treatment of the hemocyte monolayers with PAF. In conclusion, phagocytosis of yeast cells by hemocytes is related to the activation of PAF receptors and eicosanoid pathways in the bloodsucking bug, R. prolixus.

Trypanosoma rangeli is a protozoan that is non-pathogenic for humans and other mammals but causes... more Trypanosoma rangeli is a protozoan that is non-pathogenic for humans and other mammals but causes pathology in the genus Rhodnius. T. rangeli and R. prolixus is an excellent model for studying the parasite-vector interaction, but its cycle in invertebrates remains unclear. The vector becomes infected on ingesting blood containing parasites, which subsequently develop in the gut, hemolymph and salivary glands producing short and large epimastigotes and metacyclic trypomastigotes, which are the infective forms. The importance of the T. rangeli cycle is the flagellate penetration into the gut cells and invasion of the salivary glands. The establishment of the parasite depends on the alteration of some vector defense mechanisms. Herein, we present our understanding of T. rangeli infection on the vector physiology, including gut and salivary gland invasions, hemolymph reactions and behavior alteration.

Bacteria, fungi and parasites are in constant contact with the insect gut environment and can inf... more Bacteria, fungi and parasites are in constant contact with the insect gut environment and can influence different aspects of the host gut physiology. Usually, some of these microorganisms develop and survive in the digestive tract. Therefore, the gut environment must be able to tolerate certain populations of these organisms for the establishment of interactions between non-pathogenic bacteria, parasites and the gut. This review provides a brief overview of the biological and molecular mechanisms that microorganisms use to interact with the gut epithelia in mosquitoes and speculates on their significances for the development of bacteria and Trypanosoma cruzi in the guts of triatomines.

Insects are exposed to a wide range of microorganisms (bacteria, fungi, parasites and viruses) an... more Insects are exposed to a wide range of microorganisms (bacteria, fungi, parasites and viruses) and have interconnected powerful immune reactions. Although insects lack an acquired immune system they have well-developed innate immune defences that allow a general and rapid response to infectious agents. Over the last few decades we have observed a dramatic increase in the knowledge of insect innate immunity, which relies on both humoral and cellular responses. However, innate reactions to natural insect pathogens and insect-transmitted pathogens, such as parasites, still remain poorly understood. In this review, we briefly introduce the general immune system of insects and highlight our current knowledge of these reactions focusing on the interactions of Trypanosoma rangeli with Rhodnius prolixus, an important model for innate immunity investigation.

Anais da Academia Brasileira de Ciências, 2022

Rhodnius prolixus interaction with Trypanosoma rangeli: modulation of the immune system and micro... more Rhodnius prolixus interaction with Trypanosoma rangeli: modulation of the immune system and microbiota population

Journal of Insect Physiology, 2017

Methods in molecular biology

RNA interference (RNAi) has emerged as a widely used approach for reverse genetic analysis in euk... more RNA interference (RNAi) has emerged as a widely used approach for reverse genetic analysis in eukaryotes. In insects, RNAi also has an application in the control of insect pests. Several methods have been developed for delivery of interfering RNA in insects, with varying outcomes for different species. Here we describe how a bacterial symbiont can be exploited for continuous synthesis of interfering double-stranded RNA (dsRNA) in its insect host. This approach, termed symbiont-mediated RNAi (SMR), can overcome problems associated with instability of dietary dsRNA due to action of salivary or foregut nucleases. As insects do not possess RNA-dependent RNA polymerase activity that can amplify and extend RNAi in other organisms, SMR also offers the possibility of long-term systemic RNAi not afforded by single applications of dsRNA to insects by other delivery methods. Here, we describe how SMR can be applied in a globally distributed agricultural pest species, western flower thrips (Fra...

© 2009 Garcia et al; licensee BioMed Central Ltd. This is an Open Access article distributed unde... more © 2009 Garcia et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License

Developmental and comparative immunology, 2020

Rhodnius prolixus is an insect vector of two flagellate parasites, Trypanosoma rangeli and Trypan... more Rhodnius prolixus is an insect vector of two flagellate parasites, Trypanosoma rangeli and Trypanosoma cruzi, the latter being the causative agent of Chagas disease in Latin America. The R. prolixus neuroendocrine system regulates the synthesis of the steroid hormone ecdysone, which is essential for not only development and molting but also insect immunity. Knowledge for how this modulates R. prolixus midgut immune responses is essential for understanding interactions between the vector, its parasites and symbiotic microbes. In the present work, we evaluated the effects of ecdysone inhibition on R. prolixus humoral immunity and homeostasis with its microbiota, using the triterpenoid natural product, azadirachtin. Our results demonstrated that azadirachtin promoted a fast and lasting inhibitory effect on expression of both RpRelish, a nuclear factor kappa B transcription factor (NF-kB) component of the IMD pathway, and several antimicrobial peptide (AMP) genes. On the other hand, RpD...

International Journal of Molecular Sciences

Chagas disease is a human infectious disease caused by Trypanosoma cruzi and can be transmitted b... more Chagas disease is a human infectious disease caused by Trypanosoma cruzi and can be transmitted by triatomine vectors, such as Rhodnius prolixus. One limiting factor for T. cruzi development is the composition of the bacterial gut microbiota in the triatomine. Herein, we analyzed the humoral immune responses of R. prolixus nymphs treated with antibiotics and subsequently recolonized with either Serratia marcescens or Rhodococcus rhodnii. The treatment with antibiotics reduced the bacterial load in the digestive tract, and the recolonization with each bacterium was successfully detected seven days after treatment. The antibiotic-treated insects, recolonized with S. marcescens, presented reduced antibacterial activity against Staphylococcus aureus and phenoloxidase activity in hemolymph, and lower nitric oxide synthase (NOS) and higher defensin C gene (DefC) gene expression in the fat body. These insects also presented a higher expression of DefC, lower prolixicin (Prol), and lower NO...

Background: Schistosomiasis is a neglected tropical disease and affects over 200 million people w... more Background: Schistosomiasis is a neglected tropical disease and affects over 200 million people worldwide. The snail Biomphalaria glabrata is one of the intermediate hosts of S. mansoni. The aim of this work was to verify the action of Euphorbia milii var. hislopii latex in the hemocytes profile and histopathology of B. glabrata infected by S. mansoni. Methods: Uninfected and infected snails were exposed to sublethal concentrations of E. milii latex for 24 hours (1.0 mg/l less than the LC 50) and after this time were analysed. Results: The survival rate was 88.5% for the uninfected snails and 66.6% for the infected and exposed snails. In the snails infected by S. mansoni , the exposure to E. milii latex promoted proliferation of hemocytes in the tentacles, mantle, digestive gland, kidney and ovotestis. In the digestive gland and the kidney, granulomatous reactions occurred around the sporocysts and caused their destruction. Proliferation of hemocytes in the kidney and digestive gland and edema in the mantle area were also observed in the uninfected and exposed snails. The number of circulating hemocytes from the group infected and exposed to E. milii latex was significantly higher than in the other groups. Three types of hemocytes were found: hyalinocytes, granulocytes and blast-like cells, and in all the groups the proportion of hyalinocytes was higher than the other types. There was no significant difference among the cell types and the different groups analyzed. Conclusions: We conclude that the sublethal concentration of E. milii latex influenced the cellular immune response of the susceptible B. glabrata strain to infection by S. mansoni , promoting the destruction of parasites.

Memórias do Instituto Oswaldo Cruz, 2017

The aim of this study was to identify the composition of the essential oil from leaves of Lippia ... more The aim of this study was to identify the composition of the essential oil from leaves of Lippia sidoides (EOLS), a typical shrub commonly found in the dry northeast of Brazil, popularly known as "alecrim-pimenta". Additionally, we investigated the nymphicidal, ovicidal, phagoinhibitory and excretion effects of EOLS, its major constituent thymol and its isomer carvacrol, on fourth instar nymphs and eggs of Rhodnius prolixus, the Chagas' disease vector. The nymphicidal and ovicidal activity of thymol, carvacrol, and EOLS was assessed by tests using impregnated Petri dishes. The lethal concentration values (LC 50) for EOLS, carvacrol, and thymol were 54.48, 32.98, and 9.38 mg/cm 2 , respectively. The ovicidal test showed that both carvacrol and thymol (50 mg/cm 2) inhibited hatching (50% and 23.3%, respectively), while treatments with 10 mg/cm 2 or 50 mg/cm 2 EOLS did not affect the hatching rate at all (80% and 90%, respectively). We observed an anti-feeding effect in insects fed with blood containing natural products at the higher concentrations (100 µg/ mL). Finally, excretion rate was affected by EOLS and carvacrol, but not by thymol. These findings offer novel insights into basic physiological processes that make the tested natural compounds interesting candidates for new types of insecticides.

Parasites & Vectors, 2015

Background: Trypanosoma rangeli is a protozoan that infects a variety of mammalian hosts, includi... more Background: Trypanosoma rangeli is a protozoan that infects a variety of mammalian hosts, including humans. Its main insect vector is Rhodnius prolixus and is found in several Latin American countries. The R. prolixus vector competence depends on the T. rangeli strain and the molecular interactions, as well as the insect's immune responses in the gut and haemocoel. This work focuses on the modulation of the humoral immune responses of the midgut of R. prolixus infected with T. rangeli Macias strain, considering the influence of the parasite on the intestinal microbiota. Methods: The population density of T. rangeli Macias strain was analysed in different R. prolixus midgut compartments in long and short-term experiments. Cultivable and non-cultivable midgut bacteria were investigated by colony forming unit (CFU) assays and by 454 pyrosequencing of the 16S rRNA gene, respectively. The modulation of R. prolixus immune responses was studied by analysis of the antimicrobial activity in vitro against different bacteria using turbidimetric tests, the abundance of mRNAs encoding antimicrobial peptides (AMPs) defensin (DefA, DefB, DefC), prolixicin (Prol) and lysozymes (LysA, LysB) by RT-PCR and analysis of the phenoloxidase (PO) activity. Results: Our results showed that T. rangeli successfully colonized R. prolixus midgut altering the microbiota population and the immune responses as follows: 1-reduced cultivable midgut bacteria; 2-decreased the number of sequences of the Enterococcaceae but increased those of the Burkholderiaceae family; the families Nocardiaceae, Enterobacteriaceae and Mycobacteriaceae encountered in control and infected insects remained the same; 3-enhanced midgut antibacterial activities against Serratia marcescens and Staphylococcus aureus; 4-downregulated LysB and Prol mRNA levels; altered DefB, DefC and LysA depending on the infection (short and longterm); 5-decreased PO activity. Conclusion: Our findings suggest that T. rangeli Macias strain modulates R. prolixus immune system and modifies the natural microbiota composition.

Spectrochimica Acta Part B: Atomic Spectroscopy, 2012

In recent years, the effects of pollution on the health of humans and other vertebrates were exte... more In recent years, the effects of pollution on the health of humans and other vertebrates were extensively studied. However, the effects on some invertebrates are comparatively unknown. Recent studies have demonstrated that toxic metals interfere with the reproduction, development and immune defenses of some terrestrial and marine invertebrates. Some environmental conditions including pollution produce chronic and acute effects on different animal's organs and systems. In this work, we investigated changes in the concentrations of Cl, K, Ca, Fe and Zn in Rhodnius prolixus as insect model. The elements were quantified using urine and hemolymph samples collected on different days after feeding the insects with blood containing HgCl 2. The synchrotron radiation total reflection X-ray fluorescence measurements were carried at the X-ray fluorescence beamline facility in Brazilian Synchrotron Light Laboratory. The observation reveals that the calcium level was higher in the hemolymph than in urine. On the other hand, the urine collected from insects treated with HgCl 2 showed higher level of Cl than hemolymph samples. Ca, Fe and Zn concentrations decrease drastically in urine samples collected after 2 days of HgCl 2 treatment. The regulation of triatomines excretion was discussed pointing out the importance of trace elements.

Journal of Insect Physiology, 2006

In this paper we investigate in vivo and in vitro effects of orally administered azadirachtin and... more In this paper we investigate in vivo and in vitro effects of orally administered azadirachtin and ecdysone on the phagocytic responses of Rhodnius prolixus 5th-instar larval hemocytes to the yeast Saccharomyces cerevisiae. Groups of insects fed non-treated blood (control) and insects that received azadirachtin plus ecdysone in the blood meal were inoculated with yeast cells in the hemocele. The injected yeast cells disappeared rapidly from the hemolymph, being removed completely by 90min after inoculation. In the insects treated only with azadirachtin the clearance of free yeast circulating particles was significantly delayed compared to the two previously mentioned groups. It was demonstrated that the binding of yeast cells to hemocytes was reduced in the insects treated only with azadirachtin in comparison to both non-treated control and azadirachtin plus ecdysone-treated groups. Phagocytosis occurred when yeast cells were added to hemocyte monolayers prepared with hemolymph from blood fed insects, treated or not with azadirachtin plus ecdysone, so that yeast cells were rapidly bound to hemocytes and internalized in high numbers. By contrast, insects treated with azadirachtin exhibited a drastic reduction in the quantity of yeast cell-hemocyte binding and subsequent internalization. In all groups, the hemocytes attached to the glass slides were predominantly plasmatocytes. The magnitude and speed of the cellular response suggests that hemocyte phagocytosis is one of the main driving forces for the clearance of free circulating yeast cells from the hemolymph. We propose that ecdysone modulates phagocytosis in R. prolixus larvae, and that this effect is antagonized by azadirachtin.

Journal of Insect Physiology, 2008

A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (... more A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (Solanaceae), on the immune reactions of R. prolixus was carried out. Ecdysis and mortality were not affected by treatment with physalins B, D, F or G (1-10 mg/ml of blood meal). R. prolixus larvae fed with blood containing physalins and inoculated with 1 ml of Enterobacter cloacae b12 (5 Â 10 3 /insect) exhibited mortality rates three times higher than controls. The insects treated with physalin B, and F (1 mg/ml) and inoculated with E. cloacae b12 showed significant differences on lysozyme activity in the hemolymph compared to untreated insects. Furthermore, physalin D (1 mg/ml) significantly reduced the antibacterial activity. Concerning cellular immune reactions, all insects treated with physalins (1 mg/ml), exhibited drastic reductions in the quantity of yeast cell-hemocyte binding and subsequent internalization. Insects inoculated with bacteria and treated with physalins B, F and G showed reductions of microaggregate formation but physalin D did not. Physalins B and F also reduced total hemocyte count in the hemolymph. These results suggest that, in different ways, probably due to their different chemical structures, physalin B, D, F and G are immunomodulatory substances for the bloodsucking insect, R. prolixus.

Journal of Insect Physiology, 2008

The hemocytes phagocytosis in response to microorganisms may play an important role in the cellul... more The hemocytes phagocytosis in response to microorganisms may play an important role in the cellular immune responses of insects. Here, we have evaluated the effects of the platelet-activating factor (PAF) and eicosanoids in the phagocytosis of hemocyte monolayers of Rhodnius prolixus to the yeast Saccharomyces cerevisiae. Experiments showed that the phagocytosis of yeast cells by Rhodnius hemocytes is very efficient in both controls and cells treated with PAF and arachidonic acid. Phagocytosis of yeast particles is significantly blocked when the specific phopholipase A 2 inhibitor, dexamethasone, is applied on the hemocytes. By contrast, dexamethasone-pretreated hemocyte monolayers exhibit a drastic increase in the quantity of yeast cell-hemocyte internalization when the cells are treated by arachidonic acid. In addition, phagocytosis presents significant reduction in hemocyte monolayers treated with a specific PAF receptor antagonist, WEB 2086. Nevertheless, inhibition of phagocytosis with WEB 2086 is counteracted by the treatment of the hemocyte monolayers with PAF. In conclusion, phagocytosis of yeast cells by hemocytes is related to the activation of PAF receptors and eicosanoid pathways in the bloodsucking bug, R. prolixus.

Trypanosoma rangeli is a protozoan that is non-pathogenic for humans and other mammals but causes... more Trypanosoma rangeli is a protozoan that is non-pathogenic for humans and other mammals but causes pathology in the genus Rhodnius. T. rangeli and R. prolixus is an excellent model for studying the parasite-vector interaction, but its cycle in invertebrates remains unclear. The vector becomes infected on ingesting blood containing parasites, which subsequently develop in the gut, hemolymph and salivary glands producing short and large epimastigotes and metacyclic trypomastigotes, which are the infective forms. The importance of the T. rangeli cycle is the flagellate penetration into the gut cells and invasion of the salivary glands. The establishment of the parasite depends on the alteration of some vector defense mechanisms. Herein, we present our understanding of T. rangeli infection on the vector physiology, including gut and salivary gland invasions, hemolymph reactions and behavior alteration.

Bacteria, fungi and parasites are in constant contact with the insect gut environment and can inf... more Bacteria, fungi and parasites are in constant contact with the insect gut environment and can influence different aspects of the host gut physiology. Usually, some of these microorganisms develop and survive in the digestive tract. Therefore, the gut environment must be able to tolerate certain populations of these organisms for the establishment of interactions between non-pathogenic bacteria, parasites and the gut. This review provides a brief overview of the biological and molecular mechanisms that microorganisms use to interact with the gut epithelia in mosquitoes and speculates on their significances for the development of bacteria and Trypanosoma cruzi in the guts of triatomines.

Insects are exposed to a wide range of microorganisms (bacteria, fungi, parasites and viruses) an... more Insects are exposed to a wide range of microorganisms (bacteria, fungi, parasites and viruses) and have interconnected powerful immune reactions. Although insects lack an acquired immune system they have well-developed innate immune defences that allow a general and rapid response to infectious agents. Over the last few decades we have observed a dramatic increase in the knowledge of insect innate immunity, which relies on both humoral and cellular responses. However, innate reactions to natural insect pathogens and insect-transmitted pathogens, such as parasites, still remain poorly understood. In this review, we briefly introduce the general immune system of insects and highlight our current knowledge of these reactions focusing on the interactions of Trypanosoma rangeli with Rhodnius prolixus, an important model for innate immunity investigation.