RESUMO
BACKGROUND: Propolis is a bee product with various biological properties, including an antiviral activity when taken orally. However, its mechanisms at the cellular and molecular level are not well understood. RESULTS: We investigated the effect of propolis on antiviral signaling in A549 cells transfected with double-stranded RNA (dsRNA), a model for viral infection. Pretreatment of the cells with propolis inhibited poly I:C (synthetic dsRNA)-induced interferon (IFN)-ß expression. Propolis had no effect on the dsRNA-induced expression of RIG-I-like receptors (RLRs), which are known as intracellular viral RNA sensors. As to the effect on antiviral executor genes, propolis enhanced myxovirus resistance 1 (MX1) expression, whereas interferon-inducible gene 6-16 (G1P3) and 2'-5'-oligoadenylate synthetase (OAS) were unaffected. All of these genes belong to the IFN-inducible genes, suggesting that the effect of propolis on antiviral signaling is not necessarily mediated by the autocrine regulation by IFN-ß. Propolis pretreatment inhibited dsRNA-induced interleukin-8 (IL8) and CCL5 expression, and consequently lowered polymorphonuclear leukocyte (PMN) chemotactic activity in the cell-conditioned medium. CONCLUSION: Taken together, these results suggest that propolis may suppress excess inflammatory responses without affecting the innate immunity during viral infection.
Assuntos
Antivirais/farmacologia , Interferon beta/genética , Neutrófilos/efeitos dos fármacos , Própole/farmacologia , RNA de Cadeia Dupla/antagonistas & inibidores , Adenocarcinoma , Brasil , Linhagem Celular Tumoral , Quimiotaxia de Leucócito/efeitos dos fármacos , Meios de Cultivo Condicionados , Expressão Gênica/efeitos dos fármacos , Humanos , Interferon beta/antagonistas & inibidores , Neoplasias Pulmonares , Neutrófilos/fisiologia , Poli I-C/antagonistas & inibidores , Poli I-C/farmacologia , RNA de Cadeia Dupla/fisiologia , TransfecçãoRESUMO
In many eukaryotes, the introduction of double-stranded RNA (dsRNA) into cells triggers the degradation of mRNAs through a post-transcriptional gene-silencing mechanism called RNA interference or RNAi. In the present study, we found that endogenous long-dsRNA was substantially more effective at producing interference than endogenous, or exogenous, short-dsRNA expression in Giardia lamblia . The effects of this interference were not evident in the highly expressed protein tubulin or the stage-specific cyst wall protein 2. However, long-dsRNA caused potent and specific interference in the medium subunits of adaptins, the RNA-dependent RNA polymerase, and the exogenous green fluorescence protein. Our results suggest that the ability of dsRNA antisense to inhibit the expression of these specific types of proteins is indicative of a gene-specific mechanism.
Assuntos
Regulação para Baixo/genética , Giardia lamblia/genética , Proteínas de Protozoários/metabolismo , Interferência de RNA/fisiologia , RNA de Cadeia Dupla/fisiologia , Subunidades do Complexo de Proteínas Adaptadoras/genética , Subunidades do Complexo de Proteínas Adaptadoras/metabolismo , Chaperona BiP do Retículo Endoplasmático , Técnica Direta de Fluorescência para Anticorpo , Técnica Indireta de Fluorescência para Anticorpo , Regulação da Expressão Gênica/genética , Giardia lamblia/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Microscopia Confocal , Proteínas de Protozoários/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , RNA Polimerase Dependente de RNA/genética , RNA Polimerase Dependente de RNA/metabolismo , Tubulina (Proteína)/genética , Tubulina (Proteína)/metabolismoRESUMO
Isogenic strains (with and without dsRNA) of the entomogenous fungi Metarhizium anisopliae var. acridum and Paecilomyces fumosoroseus were investigated for correlation between the presence of dsRNA and the production of cuticle-degrading proteases that play an important role in host parasitism, total secreted protein, and conidia production. Similar levels of cuticle-degrading subtilisin-like (Pr1) protease were observed for isogenic strains of M. anisopliae var. acridum after growth in medium supplemented with the cuticle of the grasshopper Rhammatocerus schistocercoides. Similarly, no statistical differences were observed for protease production, detected using the chromogenic substrate azocasein. For P. fumosoroseus isogenic strains, no significant differences in protease activity were observed after growth in the presence of either Euschistus heros or Nezara viridula (Hemiptera: Pentatomidae) cuticle. Similarly, no statistical differences were observed in virulence against E. heros. A comparison of mean conidia production showed a significantly higher production in the dsRNA-free isogenic strains of M. anisopliae var. acridum. Although, for most of the fungal phenotypes analysed, no overt effects were associated with the presence of these dsRNA infections, the reduction in conidia production by the isogenic strains of M. anisopliae var. acridum with dsRNA suggested that it may not be entirely accurate to describe these infections as latent.