RESUMO
Prostaglandins (PGs) participate in the regulation of vertebrate and in at least six insect orders' immune responses. We identified PGE2 in midgut, fat body, Malpighian tubules, and ovarioles of Anopheles albimanus (Aa) mosquitoes. Our data indicate that PGE2 synthesis in cultured midguts responds to the presence of two bacterial species, Micrococcus luteus and Klebsiella pneumoniae. The production of mRNA coding for antimicrobial peptides Aa-Attacin, Aa-Cecropin, and Aa-Gambicin was observed in cultured fat bodies and midguts. The production of these messengers was reduced in the presence of dexamethasone, and this effect was reversed by arachidonic acid. Adding PGE2 to cultures resulted in increased Aa-cecropin mRNA and decreased Aa-attacin and Aa-gambicin mRNAs.
Assuntos
Anopheles/metabolismo , Peptídeos Catiônicos Antimicrobianos/metabolismo , Dinoprostona/metabolismo , Corpo Adiposo/metabolismo , Túbulos de Malpighi/metabolismo , Adaptação Fisiológica/fisiologia , Animais , Anopheles/imunologia , Anopheles/microbiologia , Cecropinas/metabolismo , Inibidores de Ciclo-Oxigenase , Dexametasona , Corpo Adiposo/imunologia , Feminino , Trato Gastrointestinal/imunologia , Trato Gastrointestinal/metabolismo , Ibuprofeno , Técnicas In Vitro , Proteínas de Insetos/metabolismo , Ovário/metabolismo , Fosfolipases A/antagonistas & inibidores , RNA Mensageiro/metabolismoRESUMO
Superoxide anion (O(-) (2)) and nitric oxide (NO) generation in Dactylopius coccus hemolymph obtained by perfusion and activated with zymosan was studied. Activated hemolymph reduced 3-[4,5 dimethylthiazolil-2]-2,5-diphenyl tetrazolium bromide. This reduction was prevented by superoxide dismutase (SOD) indicating O(-) (2) generation. This activity was dependent on temperature, and hemolymph incubated at 75 degrees C lost its activity. Chromatocytes incubated with zymosan released their content and produced O(-) (2). Activated hemolymph also produced NO and this activity was prevented in the presence of NG-nitro-L-arginine methyl ester, suggesting that nitric oxide synthase (NOS) might be present in D. coccus hemolymph. The probable source of O(-) (2) in the D. coccus hemolymph is the anthraquinone oxidation, since commercial carminic dye produced O(-) (2) during its oxidation by Agaricus bisporus tyrosinase. Gram+ Micrococcus luteus exposed to activated hemolymph were killed in vitro, and addition of NG-nitro-L-arginine methyl ester and D-Mannitol (a hydroxyl radical scavenger) prevented their killing. The cytotoxic effect produced by the activated hemolymph was not observed with the Gram- bacteria Serratia marcescens. These results suggest that D. coccus activated hemolymph generates reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) that may limit M. luteus growth.
