Flávia Borges Mury

On the mechanisms involved in biological heme crystallization

Blood-feeding organisms digest hemoglobin, releasing large quantities of heme inside their digestive tracts. Free heme is very toxic, and these organisms have evolved several mechanisms to protect against its deleterious effects. One of these adaptations is the crystallization of heme into the dark-brown pigment hemozoin (Hz). Here we review the process of Hz formation, focusing on organisms other than Plasmodium that have contributed to a better understanding of heme crystallization. Hemozoin has been found in several distinct classes of organisms including protozoa, helminths and insects and Hz formation is the predominant form of heme detoxification. The available evidence indicates that amphiphilic structures such as phospholipid membranes and lipid droplets accompanied by specific proteins play a major role in heme crystallization. Because this process is specific to a number of blood-feeding organisms and absent in their hosts, Hz formation is an attractive target for the development of novel drugs to control illnesses associated with these hematophagous organisms.

Toll signals regulate dorsal–ventral patterning and anterior–posterior placement of the embryo in the hemipteran Rhodnius prolixus

BackgroundInsect embryonic dorso-ventral patterning depends greatly on two pathways: the Toll pathway and the Bone Morphogenetic Protein pathway. While the relative contribution of each pathway has been investigated in holometabolous insects, their role has not been explored in insects with a hemimetabolous type of development. The hemimetabolous insect Rhodnius prolixus, an important vector of Chagas disease in the Americas, develops from an intermediate germ band and displays complex movements during katatrepsis that are not observed in other orders. However, little is known about the molecular events that regulate its embryogenesis. Here we investigate the expression and function of genes potentially involved in the initial patterning events that establish the embryonic dorso-ventral axis in this hemipteran.ResultsWe establish a staging system for early embryogenesis that allows us to correlate embryo morphology with gene expression profiles. Using this system, we investigate the role of Toll pathway genes during embryogenesis. Detailed analyses of gene expression throughout development, coupled with functional analyses using parental RNA interference, revealed that maternal Toll is required to establish germ layers along the dorso-ventral axis and for embryo placement along the anterior-posterior axis. Interestingly, knockdown of the Toll pathway effector Rp-dorsal appears to regulate the expression of the Bone Morphogenetic Protein antagonist Rp-short-gastrulation.ConclusionsOur results indicate that Toll signals are the initiating event in dorso-ventral patterning during Rhodnius embryogenesis, and this is the first report of a conserved role for Toll in a hemipteran. Furthermore, as Rp-dorsal RNA interference generates anteriorly misplaced embryos, our results indicate a novel role for Toll signals in establishment of the anterior-posterior axis in Rhodnius.

small ORFs: A new class of essential genes for development.

Genes that contain small open reading frames (smORFs) constitute a new group of eukaryotic genes and are expected to represent 5% of the Drosophila melanogaster transcribed genes. In this review we provide a historical perspective of their recent discovery, describe their general mechanism and discuss the importance of smORFs for future genomic and transcriptomic studies. Finally, we discuss the biological role of the most studied smORF so far, the Mlpt/Pri/Tal gene in arthropods. The pleiotropic action of Mlpt/Pri/Tal in D. melanogaster suggests a complex evolutionary scenario that can be used to understand the origins, evolution and integration of smORFs into complex gene regulatory networks.

Larvicidal Potential of the Halogenated Sesquiterpene (+)-Obtusol, Isolated from the Alga Laurencia dendroidea J. Agardh (Ceramiales: Rhodomelaceae), against the Dengue Vector Mosquito Aedes aegypti (Linnaeus) (Diptera: Culicidae)

Dengue is considered a serious public health problem in many tropical regions of the world including Brazil. At the moment, there is no viable alternative to reduce dengue infections other than controlling the insect vector, Aedes aegypti Linnaeus. In the continuing search for new sources of chemicals targeted at vector control, natural products are a promising alternative to synthetic pesticides. In our work, we investigated the toxicity of a bioactive compound extracted from the red alga Laurencia dendroidea J. Agardh. The initial results demonstrated that crude extracts, at a concentration of 5 ppm, caused pronounced mortality of second instar A. aegypti larvae. Two molecules, identified as (−)-elatol and (+)-obtusol were subsequently isolated from crude extract and further evaluated. Assays with (−)-elatol showed moderate larvicidal activity, whereas (+)-obtusol presented higher toxic activity than (−)-elatol, with a LC50 value of 3.5 ppm. Histological analysis of the larvae exposed to (+)-obtusol revealed damage to the intestinal epithelium. Moreover, (+)-obtusol-treated larvae incubated with 2 µM CM-H2DCFDA showed the presence of reactive oxygen species, leading us to suggest that epithelial damage might be related to redox imbalance. These results demonstrate the potential of (+)-obtusol as a larvicide for use against A. aegypti and the possible mode of action of this compound.

AVALIAÇÃO MOLECULAR DAS VIAS IMUNOLÓGICAS DE SINALIZAÇÃO CELULAR EM Aedes aegypti INFECTADO COM Metarhizium anisopliae

Recentes trabalhos mostraram que femeas de Aedes aegypti alimentadas com sangue foram menos suscetiveis ao fungo Metarhizum anisopliae , comparado com femeas alimentadas com sacarose. Desde entao estudos tem sido feitos investigando o porque desses resultados. No presente trabalho foi avaliado a expressao dos genes relacionados as vias Toll, Immune Deficiency (IMD) e Janus Quinase (JAK-STAT) de A. aegypti alimentadas com sangue ou sacarose. As femeas de A. aegypti foram infectadas com M. anisopliae e 48 horas depois foram dissecadas para obtencao do corpo gorduroso (CG) e epitelio intestinal (EI). Realizou-se extracao de RNA total, obtencao de cDNA e analise por PCR em tempo real. Nossos resultados mostraram que ocorreu uma modulacao positiva na expressao dos genes Relish 1A, Cactus e STAT no epitelio intestinal e corpo gorduroso em femeas alimentadas com sacarose e infectadas com fungo.

AVALIÇÃO DA RESPOSTA IMUNE DO HEMIPTERA Rhodnius prolixus FRENTE À INFECÇÃO COM O FUNGO ENTOMOPATOGÊNICO Metarhizium anisopliae

O hemipetra Rhodnius prolixus e vetor da doenca de chagas. O fungo Metarhizium anisopliae apresenta patogenicidade e virulencia contra varias especies de insetos e vem sendo utilizado como inseticida biologico contra diferentes pragas e vetores. Dessa forma, o objetivo do presente trabalho foi avaliar o perfil da resposta imune de R. prolixus apos infeccao com fungo entomopatogenico M. anisopliae . Para isso foram utilizadas femeas adultas em jejum ou alimentadas com sangue de coelho e, posteriormente, infectado com o fungo M. anisopliae . A modulacao da resposta imune foi estudada pela analise da abundância de RNAm codificando Dorsal e Cactus (via Toll), Relish (via IMD), Eigher (ortologo de TNF), STAT e SOCS (via Jack-STAT), bem como Defensina e Lisozimas (LysA, LysB) (peptideos antimicrobianos) por RT-qPCR. O EF-1 (Elongation Factor-1) foi utilizado como gene de referencia. Os resultados preliminares mostraram que a infeccao por fungo foi capaz de reduzir a taxa de eclosao de R. prolixus em 40%. Foi evidenciado que as Vias Toll e IMD estao envolvidas na defesa imune contra M. anisopliae .