Biology subjects

Oliveira, P. L.

Publications and source records attributed to Oliveira, P. L..

12 recordsLinked to original sources

bioRxiv2026

Small Heat Shock Proteins have a Paramount Role inTrypanosoma cruzi Infection Impacting Intestinal Homeostasis of an Insect Vector of Chagas Disease

Rhodnius prolixus, an insect vector of Chagas disease, ingests blood meals several-fold its own body weight. This nutritional overload triggers specific adaptive responses that prevent or remediate damage from multiple stressors, including oxidative, osmotic, and microbial challenges. Transcriptomic analysis of first-instar nymph guts revealed five members of the Small Heat-Shock Protein (sHSP) family that were highly expressed after blood meals but were downregulated upon Trypanosoma cruzi infection. sHSPs are proteins involved in cellular homeostasis and stress responses. Simultaneous knockdown of all five sHSPs profoundly disrupted insect physiology, causing decreased actin filament network formation, interrupted peristalsis, blocked ER expansion, and reduced ER-mitochondria association, while increasing reactive oxygen species generation and inducing premature epithelial cell mitosis. This apparent loss of gut homeostasis was recapitulated by trypanosome infection and, conversely, sHSP silencing in infected insects increased parasite numbers. Taken together, our data reveal a paramount role for sHSPs in gut cell homeostasis following blood meals and support the hypothesis that sHSP expression down regulation represents an adaptive manipulation of the insect host by the parasite. Significance StatementThis study demonstrates that sHSPs serve as critical regulators of digestive physiology and intestinal homeostasis in a Chagas disease vector. These proteins orchestrate key processes including ROS production and cytoskeletal and endoplasmic reticulum organization, directly influencing T. cruzi proliferation. Conversely, the parasite manipulates their expression, revealing sHSPs as novel determinants of vector competence. Between 6 and 7 million people worldwide suffer from Chagas Disease, with 10,000 deaths annually. Although vector-borne transmission has declined, oral transmission is increasing, underscoring the urgent need to understand molecular factors governing vector competence. Our findings position sHSPs as promising targets for developing innovative strategies to control disease transmission.

microbiology↗

bioRxiv2025

Loss of Vitellogenin Receptor Function Results in Yolk Depletion, Virome Expansion and Reduced Bacterial Load Within the Oocytes of Rhodnius prolixus

The vitellogenin receptor (VgR) mediates yolk protein uptake during oogenesis and is essential for embryogenesis in oviparous species. Here we characterize the single Rhodnius prolixus VgR isoform and uncover an unexpected role in microbial regulation within the reproductive system. The receptor displays a conserved LDLR-like structure and is highly expressed in early oocytes. RNAi-mediated VgR silencing caused defective yolk granule biogenesis, leading to the accumulation of the main yolk protein precursors, Vg and RHBP, in the hemolymph, yet oviposition and fertilization proceeded normally. The resulting eggs were yolk-depleted and non-viable. Remarkably, VgR knockdown reduced bacterial 16S rRNA levels in oocytes while promoting the expansion of several members of the core virome, a phenotype not reproduced by Vg silencing. Neither purified Vg nor changes in immune (defensin) or RNA interference pathways explained the microbial shifts. These findings indicate that VgR governs not only yolk endocytosis but also the trafficking of microbial components into developing oocytes. We propose that VgR contributes to the linking of yolk endocytic dynamics and microbial homeostasis, influencing the balance of microbial components within developing oocytes. This connection broadens the functional scope of the VgR and provides new insight into how vertical transmission processes are shaped in this major Chagas disease vector. Author summaryEgg-laying animals must load their eggs with enough nutrients to support early development. In insects, this process depends on a receptor that brings yolk proteins into the growing egg. Here, we studied this receptor in Rhodnius prolixus, a major vector of Chagas disease, and uncovered an unexpected link between yolk uptake and the microorganisms that enter the egg. When we blocked the receptor, females continued to produce and lay eggs, but these eggs failed to accumulate yolk and could not support embryonic development. Strikingly, the absence of the receptor also shifted the microbial community inside the oocyte: bacterial levels dropped, while several viruses expanded. These changes did not result from differences in yolk proteins, immune activation, or direct antimicrobial effects, indicating that the receptor itself influences microbial entry or persistence in the egg. Our findings reveal that this yolk receptor plays a dual role, providing nutrients and shaping the microbial community that is passed from mother to offspring. This work highlights an unrecognized layer of interaction between reproduction and microbial transmission in an important disease vector, offering new perspectives for understanding and potentially disrupting vertical transmission pathways.

cell biology↗

bioRxiv2024

Deployment and transcriptional evaluation of nitisinone, an FDA-approved drug, to control bed bugs

Bed bugs are blood-feeders that rapidly proliferate into large indoor infestations. Their bites can cause allergies, secondary infections and psychological stress, among other problems. Although several tactics for their management have been used, bed bugs continue to spread worldwide wherever humans reside. This is mainly due to human-mediated transport and their high resistance to several classes of insecticides. New treatment options with novel modes of action are required for their control. In this study, we evaluated the use of nitisinone (NTBC), an FDA-approved drug, for bed bug control in an insecticide-susceptible (HH) and an insecticide-resistant (CIN) population. Although NTBC was lethal to both populations when administered orally or applied topically in very low doses, we observed a slight but significant resistance in the CIN population. Transcriptomic analysis in both populations indicated that NTBC treatment elicited a broad suppression of genes associated with RNA post-transcriptional modifications, translation, endomembrane system, protein post-translational modifications and protein folding. The CIN population exhibited higher ATP production and xenobiotic detoxification. Feeding studies on a mouse model highlight that NTBC could be used as a control method of bed bugs by host treatment. The results demonstrate that NTBC can be used as a new active ingredient for bed bug control by topical or oral treatment and shed light on the molecular mechanisms of suppressed tyrosine metabolism following NTBC treatment.

physiology↗

bioRxiv2023

Heme exporter FLVCR regulates mitochondrial biogenesis and redox balance in the hematophagous insect Rhodnius prolixus

Heme is a prosthetic group of proteins involved in vital physiological processes in aerobic organisms. It participates in redox reactions crucial for cell metabolism due to the variable oxidation state of its central iron atom. However, excessive heme can be cytotoxic due to its prooxidant properties. Therefore, the control of intracellular heme levels ensures the survival of organisms, especially those that deal with high concentrations of heme during their lives, such as hematophagous insects. The feline leukemia virus C receptor (FLVCR) is a membrane protein responsible for heme transport in mammalian cells. In our study, we found that RpFLVCR serves as a heme exporter in the midgut of the hematophagous insect Rhodnius prolixus, a vector for Chagas disease. Silencing RpFLVCR decreased hemolymphatic heme levels and increased the levels of intracellular dicysteinyl-biliverdin, a product of R. prolixus heme degradation, indicating heme retention inside midgut cells. FLVCR silencing led to increased expression of heme oxygenase (HO), ferritin, and mitoferrin mRNAs while downregulating the iron importers Malvolio 1 and 2. In contrast, HO gene silencing increased FLVCR and Malvolio expression and downregulated ferritin, revealing crosstalk between heme degradation/export and iron transport/storage pathways. Furthermore, RpFLVCR silencing strongly increased oxidant production and lipid peroxidation, reduced cytochrome c oxidase activity and activated mitochondrial biogenesis, effects not observed in RpHO-silenced insects. These data support FLVCR function as a heme exporter, playing a pivotal role in heme/iron metabolism and maintenance of redox balance, especially in an organism adapted to face extremely high concentrations of heme.

biochemistry↗

bioRxiv2022

Exploring dose-response relationships in Aedes aegypti survival upon bacteria and arbovirus infection.

A detailed understanding of host fitness changes upon variation in microbe density is a central aim of infection biology. Here, we applied dose-response curves to study Aedes aegypti survival upon exposure to different microbes. We challenged female mosquitoes with Listeria monocytogenes, a model bacterial pathogen, Dengue 4 virus and Zika virus, two medically relevant arboviruses, to understand the distribution of mosquito susceptibility and net fitness (survival) following microbe exposure. By correlating microbe loads and host health, we found that a blood meal promotes survival in our systemic bacterial infection model and that mosquitoes orally infected with bacteria had an enhanced defensive capacity than insects infected through injection. We also showed that Aedes aegypti has a higher survival profile upon arbovirus infection but, under the conditions tested, was more susceptible to Zika virus when compared to Dengue virus. Here, we applied a framework for the study of microbe-induced mosquito mortality detailing how Aedes aegypti lifespan varies upon different inoculum sizes of bacteria and arboviruses.

microbiology↗

bioRxiv2022

eIF3 subunit M regulates blood meal digestion in Rhodnius prolixus affecting ecdysis, reproduction and survival.

In triatomines, blood-feeding triggers many physiological processes, including post-embryonic development and reproduction. Different feeding habits, such as hematophagy, can shape gene functions to meet the challenges of each type of diet. A comparison of transcriptomic and proteomic data indicates that post-transcriptional regulation of gene expression is crucial in triatomines, so we evaluated the impact of RNAi silencing of the eukaryotic translation initiation factors 3 subunit m (eIF3m) in R. prolixus physiology. We showed that eIF3m is essential for correct digestion, affecting the processes triggered by a blood meal. The silencing of this gene inhibited moulting and caused the premature death of nymphs, while in adult females inhibited oviposition and increased resistance to starvation. Male survival was not affected by eIF3m knockdown. The information regarding the eIF3m function in insects is scarce. The phenotypes observed in R. prolixus upon eIF3m gene silencing are different and more severe than those described in Drosophila melanogaster, pointing to the particular importance of this gene in triatomines. Summary statementThe information provided here indicates the importance of mRNA translation in modulating growth, reproduction, lifespan and starvation resistance in triatomine vectors.

molecular biology↗

bioRxiv2022

The Aedes aegypti peritrophic matrix controls arbovirus vector competence through HPx1, a heme induced peroxidase.

Aedes aegypti mosquitoes are the main vectors of arboviruses. The peritrophic matrix (PM) is an extracellular layer that surrounds the blood bolus and acts as an immune barrier that prevents direct contact of bacteria with midgut epithelial cells during blood digestion. Here, we describe a heme-dependent peroxidase, hereafter referred to as heme peroxidase 1 (HPx1). HPx1 promotes PM assembly and antioxidant ability, modulating vector competence. Mechanistically, the heme presence in a blood meal induces HPx1 transcriptional activation mediated by the E75 transcription factor. HPx1 knockdown increases midgut reactive oxygen species (ROS) production by the DUOX NADPH oxidase. Elevated ROS levels reduce microbiota growth while enhancing epithelial mitosis, a response to tissue damage. However, simultaneous HPx1 and DUOX silencing was not able to rescue bacterial population growth, as explained by increased expression of antimicrobial peptides (AMPs), which occurred only after double knockdown. This result revealed hierarchical activation of ROS and AMPs to control microbiota. HPx1 knockdown produced a 100-fold decrease in Zika and Dengue 2 midgut infection, demonstrating the essential role of the mosquito PM in the modulation of arbovirus vector competence. Our data show that the PM connects blood digestion to midgut immunological sensing of the microbiota and viral infections.

microbiology↗

bioRxiv2020

Repurposing the orphan drug nitisinone to control the transmission of African trypanosomiasis

Tsetse transmit African trypanosomiasis, which is a disease fatal to both humans and animals. A vaccine to protect against this disease does not exist so transmission control relies on eliminating tsetse populations. Although neurotoxic insecticides are the gold standard for insect control, they negatively impact the environment and reduce insect pollinator species. Here we present a promising, environment-friendly alternative that targets insect tyrosine metabolism pathway. A bloodmeal contains high levels of tyrosine, which is toxic to haematophagous insects if it is not degraded. RNAi silencing of either the first two enzymes in the tyrosine degradation pathway (TAT and HPPD) was lethal to tsetse. Furthermore, nitisinone (NTBC), an FDA-approved tyrosine catabolism inhibitor, killed tsetse regardless if the drug was orally or topically applied. However, it did not affect bumblebee survival. A mathematical model shows that NTBC could reduce the transmission of African trypanosomiasis in sub-Saharan Africa, thus accelerating current elimination programmes.

biochemistry↗

bioRxiv2020

Pigmentation loci as markers for genome editing in the Chagas disease vector Rhodnius prolixus

The kissing bug Rhodnius prolixus is a major vector for Chagas disease in the Americas, and also considered as the primary model for functional studies. Prospective transgenic approaches and genome editing strategies hold great promise for controlling insect populations as well as disease propagation. In this context, identifying visible genetic markers for transgenic methodologies is of paramount importance to advance the field. Here we have identified and analyzed the function of putative cuticle and eye color genes by investigating the effect of gene knockdown on fertility, viability, and the generation of visible phenotypes. Synthesis of the dark, yellow and tan pigments present in the cuticle of most insects depends on the function of key genes encoding enzymes in the tyrosine pathway. Knockdown of the R. prolixus yellow and aaNAT/pro orthologs produces striking alterations in cuticle color. Surprisingly, knockdown of ebony does not generate visible phenotypes. Since loss of ebony function results in a dark cuticle in several insect orders, we conclude that R. prolixus evolved alternative strategies for cuticle coloration, possibly including the loss of a pigmentation function for an entire branch of the tyrosine pathway. Knockdown of the scarlet and brown genes - encoding ABC transporters - alters cuticle and eye pigmentation, implying that the transport of pigment into proper organelles is an important process both for cuticle and eye coloration in this species. Therefore, this analysis identifies for the first time potential visible markers for transgenesis in a hemipteran vector for a debilitating human disease. Author SummaryThe hemipteran Rhodnius prolixus - also known as a kissing bug - is a main vector transmitting the parasite Trypanosoma cruzi, the causative agent of Chagas disease, a debilitating infection estimated to affect more than 6 million people in Central and South America. In order to limit disease spread, an important measure is insect vector control. However, kissing bugs - like other insects - develop resistance to insecticides. Alternative strategies based on transgenesis and the recently developed CRISPR- based genome edition hold great promise to control vector population or generate parasite-resistant insects. For these approaches to be feasible in R. prolixus, it is critical to identify visible phenotypic markers. Here we identify and describe several genes controlling cuticle and eye pigmentation that are well-suited putative landing sites for transformation strategies. Among these, loss-of-function mutations in the ABC transporter encoding scarlet and the tyrosine pathway enzyme encoding aaNAT/pro generate striking and easily visible phenotypes. Importantly, the knockdown of these genes does not affect insect viability and fertility under laboratory conditions. Our results suggest that R. prolixus has developed alternative strategies for cuticle coloration involving the loss of an entire branch of tanning loci, while the other branch producing cuticle patterns by generating non-pigmented areas has gained critical importance.

genetics↗

bioRxiv2019

On the use of inhibitors of 4-hydroxyphenylpyruvate dioxygenase as a vector-selective insecticide in the control of mosquitoes

Blood-sucking insects incorporate many times their body weight of blood in a single meal. As proteins are the major component of vertebrate blood, its digestion in the gut of hematophagous insects generates extremely high concentrations of free amino acids. Previous reports showed that the tyrosine degradation pathway plays an essential role in adapting these animals to blood feeding. Inhibiting 4-hydroxyphenylpyruvate dioxygenase (HPPD), the rate-limiting step of tyrosine degradation, results in the death of insects after a blood meal. Therefore, it was suggested that compounds that block the catabolism of tyrosine could act selectively on blood-feeding insects. Here we have evaluated the toxicity against mosquitoes of three HPPD inhibitors currently used as herbicides and in human health. Among the compounds tested, nitisinone (NTBC) proved to be more potent than mesotrione (MES) and isoxaflutole (IFT) in Aedes aegypti. NTBC was lethal to Ae. aegypti in artificial feeding assays (LD50: 4.36 {micro}M), as well as in topical application (LD50: 0.0033 nmol/mosquito). NTBC was also lethal to Ae. aegypti populations that were resistant to neurotoxic insecticides, and it was lethal to other mosquito species (Anopheles and Culex). Therefore, HPPD inhibitors, particularly NTBC, represent promising new drugs for mosquito control. Since they only affect blood-feeding organisms, they would represent a safer and more environmentally friendly alternative to conventional neurotoxic insecticides.\n\nAuthor SummaryThe control of mosquitoes has been pursued in the last decades by the use of neurotoxic insecticides to prevent the spreading of dengue, zika and malaria, among other diseases. However, the selection and propagation of different mechanisms of resistance hinder the success of these compounds. New methodologies are needed for their control. Hematophagous arthropods, including mosquitoes, ingest quantities of blood that represent many times their body weight in a single meal, releasing huge amounts of amino acids during digestion. Recent studies showed that inhibition of the tyrosine catabolism pathway could be a new selective target for vector control. Thus we tested three different inhibitors of the second enzyme in the tyrosine degradation pathway as tools for mosquito control. Results showed that Nitisinone (NTBC), an inhibitor used in medicine, was the most potent of them. NTBC was lethal to Aedes aegypti when it was administered together with the blood meal and when it was topically applied. It also caused the death of Anopheles aquasalis and Culex quinquefasciatus mosquitoes, as well as field-collected Aedes populations resistant to neurotoxic insecticides, indicating that there is no cross-resistance. We discuss the possible use of NTBC as a new insecticide.

physiology↗

bioRxiv2019

Analysis of the testis transcriptome of the Chagas’ disease vector Rhodnius prolixus

Rhodnius prolixus is amongst the most important vectors of Trypanosoma cruzi in the Americas, putting thousands of people at risk of contracting Chagas Disease. This insect is also one of the most important models in insect physiology, especially regarding the blood-feeding process. However, studies on R. prolixus genetics lagged, and our understanding on the regulation of gene expression is incipient. Transcriptomes have the power to study the expression of thousands of genes in a single experiment. A comprehensive R. prolixus transcriptome was performed in 2014, sequencing RNA from different tissues (anterior gut, midgut, posterior gut, rectum, ovaries, fat body, maphigian tubules, and testicles). However, on that occasion, only the gut transcriptome was deeply analysed. Here we evaluated the results of the testicles transcriptome of R. prolixus with the objective to find and understand genes that could have an important role in male reproduction. We found, that from the 25,673 transcripts assembled in the whole transcriptome, 5,365 have a testicle specific expression pattern. As expected, amongst the most abundant families of transcripts, are those related to spermatogenesis and male fertility, such as myosins, actins, and dyneins. To our surprise, lipocalins, serine protease inhibitors (serpins), and lysozymes also were highly abundant in testicles. The role of these classes of genes are well known in other tissues, such as salivary glands and gut, but very little is known on their role in male reproduction (and we proposed here a few hypothesis that could be tested to address the role of these genes in male fertility). It would be interesting to study further the role of these genes on R. prolixus male fertility. Finally, as a reflection of the lack of knowledge on triatomine genetics, we found that almost half of the transcripts in R. prolixus testicles have no similarities to any other genes on reference databases. Our study shows that we still have a lot to know and to understand about reproduction in triatomine, especially in males. Besides the large number of genes without described function (possibly novel genes), there are those in which the function is known for other tissues, and we can only guess, at best, the role and importance of such genes for triatomine male fertility. Author SummaryThe understanding of the biology of insects vectors of parasitic diseases is key to the development of strategies of public health. For decades, the studies on the biology of male insects vectors of diseases was neglected, since in many cases female insects are those with relevant role in the spread of diseases. With the development of genomics, large scale studies to compare differential gene expression (transcriptomics) among different tissues, developmental stages, and sex became accessible. In this study, we looked at the physiology of the male reproductive organs of the vector of Chagas disease Rhodnius prolixus. This is a first glimpse, from a perspective of genes differentially expressed in male gonads, in such insects. We also performed an effort to link all identified genes with the insect genome published in 2015. We found ~14,000 genes expressed in the testicles, from which 5,635 genes are expressed exclusively in male reproductive organs. From the ~14,000 genes, we were able to attribute putative biological functions to 6,372 genes, which allowed us to draw a bigger picture on how these genes contribute to male fertility. This study now opens the door for further in-depth studies to find key genes for R. prolixus reproductive biology.

genomics↗

bioRxiv2018

Regulation of midgut cell proliferation impacts Aedes aegypti susceptibility to dengue virus

Aedes aegypti is the vector of some of the most important vector-borne diseases like Dengue, Chikungunya, Zika and Yellow fever, affecting millions of people worldwide. The cellular processes that follow a blood meal in the mosquito midgut are directly associated with pathogen transmission. We studied the homeostatic response of the midgut against oxidative stress, as well as bacterial and dengue virus (DENV) infections, focusing on the proliferative ability of the intestinal stem cells (ISC). Inhibition of the peritrophic matrix (PM) formation led to an increase in ROS production by the epithelial cells in response to contact with the resident microbiota, suggesting that maintenance of low levels of ROS in the intestinal lumen is key to keep ISCs division in balance. We show that dengue virus infection induces midgut cell division in both DENV susceptible (Rockefeller) and refractory (Orlando) mosquito strains. However, the susceptible strain delays the activation of the regeneration process compared with the refractory strain. Impairment of the Delta/Notch signaling, by silencing the Notch ligand Delta using RNAi, significantly increased the susceptibility of the refractory strains to DENV infection of the midgut. We propose that this cell replenishment is essential to control viral infection in the mosquito. Our study demonstrates that the intestinal epithelium of the blood fed mosquito is able to respond and defend against different challenges, including virus infection. In addition, we provide unprecedented evidence that the activation of a cellular regenerative program in the midgut is important for the determination of the mosquito vectorial competence.

cell biology↗