Effect of fluralaner on the biology, survival, and reproductive fitness of the neotropical malaria vector Anopheles aquasalis.

BACKGROUND: Reducing mosquito abundance or interfering with its ability to support the parasite cycle can help to interrupt malaria in areas of significant risk of malaria transmission. Fluralaner is a safe and effective drug for veterinary use indicated for the treatment against fleas and ticks which acts as an antagonist of chloride ion channels mediated by γ-aminobutyric acid (GABA), preventing the entry of these ions into the postsynaptic neuron, leading to hyperexcitability of the postsynaptic neuron of the central nervous system of arthropods. Fluralaner demonstrated insecticidal activity against different insect species. METHODS: The study aimed to evaluate the effects of fluralaner on the biology, survival, and reproductive fitness of Anopheles aquasalis. The following lethal concentrations (LC) were determined for An. aquasalis: LC5 = 0.511 µM; LC25 = 1.625 µM; LC50 = 3.237 µM. RESULTS: A significant decrease (P < 0.001) was evident in the number of eggs, larvae, and pupae in the group exposed to a sublethal dose of fluralaner when compared to a control group (without the drug). Using blood from dogs after administration of fluralaner, it was observed that the drug causes 100% mortality in An. aquasalis in less than 24 h after feeding; this effect remains even after 90 days in all samples. DISCUSSION: Fluralaner showed the same result for up to 60 days, and after that, there was a slight reduction in its effect, evidenced by a decrease in the percentage of dead females; however, still significant when compared to the control group. CONCLUSION: Fluralaner affects the biology and reduction of survival in An. aquasalis in a lasting and prolonged period, and its fecundity with lower dosages, is a strong candidate for controlling disease vectors.

Unravelling the genome of the brackish water malaria vector Anopheles aquasalis.

Malaria is a severe public health problem in several developing tropical and subtropical countries. Anopheles aquasalis is the primary coastal malaria vector in Central and South America and the Caribbean Islands, and it has the peculiar feature of living in water with large changes in salinity. Recent research has recognised An. aquasalis as an important model for studying the interactions of murine and human Plasmodium parasites. This study presents the complete genome of An. aquasalis and offers insights into its evolution and physiology. The genome is similar in size and gene content to other Neotropical anophelines, with 162 Mb and 12,446 protein-coding genes. There are 1387 single-copy orthologs at the Diptera level (eg. An. gambiae, An. darlingi and Drosophila melanogaster). An. aquasalis diverged from An. darlingi, the primary malaria vector in inland South America, nearly 20 million years ago. Proteins related to ion transport and metabolism belong to the most abundant gene families with 660 genes. We identified gene families relevant to osmosis control (e.g., aquaporins, vacuolar-ATPases, Na+/K+-ATPases, and carbonic anhydrases). Evolutionary analysis suggests that all osmotic regulation genes are under strong purifying selection. We also observed low copy number variation in insecticide resistance and immunity-related genes for all known classical pathways. The data provided by this study offers candidate genes for further studies of parasite-vector interactions and for studies on how anophelines of brackish water deal with the high fluctuation in water salinity. We also established data and insights supporting An. aquasalis as an emerging Neotropical malaria vector model for genetic and molecular studies.

Phenotypic traits of individuals in a long-term colony of Anopheles (Nyssorhynchus) aquasalis (Diptera: Culicidae) show variable susceptibility to Plasmodium and suggest cryptic speciation.

Anopheles aquasalis is an important malaria vector in coastal regions of South America and islands of the Caribbean. In its original description, the species was divided into two varieties, based on the scaling patterns of their hind-tarsomere 2. Specimens from our 25-year established colony, used for Plasmodium experimental infections, still exhibit both scaling tarsomere patterns. This study examined the DNA sequence of the nuclear Internal Transcribed Spacer 2 (ITS2) and susceptibility to Plasmodium, looking for differences among the phenotypes 30BS and 50BS. One hundred mosquitoes, 25 males and 25 females of each sex, and phenotype were analyzed. Twenty-seven novel haplotypes were identified. Three were found in both phenotypes (30BS and 50BS) regardless of gender. Among the other 27 genotypes, we observed a male-oriented bias in both phenotypic categories. Evaluation of Plasmodium yoelii N67 infections, based on oocyst counts, showed a higher susceptibility of 30BS compared with 50BS. Future studies need to be conducted to evaluate if these genotype assortments among the phenotypic groups reflect differences in fitness, mating, and their susceptibility to infection by Plasmodium parasites.

GD3 ganglioside-enriched extracellular vesicles stimulate melanocyte migration.

Melanomas often accumulate gangliosides, sialic acid-containing glycosphingolipids found in the outer leaflet of plasma membranes, as disialoganglioside GD3 and its derivatives. Here, we have transfected the GD3 synthase gene (ST8Sia I) in a normal melanocyte cell line in order to evaluate changes in the biological behavior of non-transformed cells. GD3-synthase expressing cells converted GM3 into GD3 and accumulated both GD3 and its acetylated form, 9-O-acetyl-GD3. Melanocytes were rendered more migratory on laminin-1 surfaces. Cell migration studies using the different transfectants, either treated or not with the glucosylceramide synthase inhibitor d-1-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (PPPP), allowed us to show that while GM3 is a negative regulator of melanocyte migration, GD3 increases it. We showed that gangliosides were shed to the matrix by migrating cells and that GD3 synthase transfected cells shed extracellular vesicles (EVs) enriched in GD3. EVs enriched in GD3 stimulated cell migration of GD3 negative cells, as observed in time lapse microscopy studies. Otherwise, EVs shed by GM3+veGD3-ve cells impaired migration and diminished cell velocity in cells overexpressing GD3. The balance of antimigratory GM3 and promigratory GD3 gangliosides in melanocytes could be altered not only by the overexpression of enzymes such as ST8Sia I, but also by the horizontal transfer of ganglioside enriched extracellular vesicles. This study highlights that extracellular vesicles transfer biological information also through their membrane components, which include a variety of glycosphingolipids remodeled in disease states such as cancer.

Papel de dissialogangliosídeos na progressão tumoral de melanomas / Role of disialoganglioside in melanoma tumor progression

Na progressão tumoral, células de melanoma acumulam derivados de dissialogangliosídeos. A função desses glicoconjugados na progressão do tumor ainda é desconhecida. Tem-se estudado um possível papel de dissialogangliosídeos na migração celular. A linhagem celular de melanócito, melan-a, foi usada como modelo para a expressão do gene da GD3-sintase (ST8Sia I), a qual é a única enzima conhecida na conversão de GM3 no gangliosídio associado a tumor, GD3... Essas células também foram mais migratórias do que as células GM3+/GD3-, sugerindo que GM3 tem um papel negativo na migração celular. Depois foi examinado o efeito da adição de gangliosídeos exógenos. A adição de GM3 em células derivadas de melan-a também inibiu a migração celular; enquanto que a adição de GD3 a promoveu a migração. Juntos, nossos resultados sugerem que a razão entre GM3 e GD3 em melanócitos mostra um papel modulatório na motilidade celular dependente de integrina. Nós também mostramos a papel pró-apoptótico de GD3 em células de melanoma murino (TM1). Uma vez que, o insucesso de transfecção da expressão estável de GD3 sintase em TM1 pode ser devido a sensibilização destas células a morte celular na presença de uma superexpressão de GD3. As células sobreviventes seriam aquelas que adquiriam a capacidade de modificar o seu produto da GD3 sintase para um dos seus derivados, não-apoptogênico. Desta forma, nós propomos que a persistência da expressão de GD3 pode selecionar células resistentes a apoptose, as quais, por sua vez adquiririam um fenótipo mais migratório...(aU)

Upon tumor progression, melanoma cells accumulate disialoganglioside derivatives. The function of these molecules in tumor progression remains unknown. To address possible functions of the disialoganglioside G03 , the murine melanocyte cell line, melan-a, was transfected with the G03 synthase gene (ST8Sia 1). In melan-a transfectants, disialogangliosides modulated melanocyte cell adhesion and migration. Ali transfectants displayed equivalent . . + + leveis of 1ntegnns on the cell surface. GM3 /G03 melanocytes tended to adhere and migrate more towards laminin-1 coated surfaces than GM3 +/G03- cells. Depletion of glycosphingolipids, using phenyl-palmitoylamino-pirrolidinopropanol (PPPP), rendered cells (LacCer-)/GM3- /G03-.These latter cells were also more migratory than GM3 +fG03- cells, suggesting that GM3 plays a negative role in cell migration. We next examined the effect of exogenously added gangliosides. Addition of GM3 to melan-a cells also inhibited cell migration; whereas exogenously added G03 promoted it. Taken together, our results suggest that the ratio between GM3 and G03 in melanocytes modulates migration. We have also uncovered a pro-apoptogenic function of G03 in murine melanomas, as we failed to achieve stable expression of G03 in melanoma cells due to their increased sensitivity to cell death inducing agents. Failure of maintaining high expression of G03 in murine melanoma cells was associated with de novo expression of GM2/Go2 synthase gene. This gene converts G03 in Go2. GM2/Go2 synthase gene expression could warrant survival of G03 synthase expressing cells, by consuming Go3 and therefore releasing cells from the pro-apoptogenic effect of this ganglioside (AU)