RESUMO
Defensins, a family of small, cationic, antimicrobial peptides, are found in mammals, insects and plants. alpha-defensins are stored in granules of neutrophils and released upon activation by exocytosis. It was shown here that human neutrophil peptide (HNP), at concentrations of 10(-8) -10(-9) M, up-regulated the expression of TNF-alpha and IL-1 beta in monocytes activated with Staphylococcus aureus or PMA, while expression of IL-10 mRNA was down-regulated and production of IL-8 was not affected. HNP alone was unable to induce TNF-alpha or IL-1 beta expression in resting monocytes. At concentrations of 10(-4) -10(-5)M, HNP was cytotoxic for monocytes in serum-free medium. The cytotoxicity was abrogated in the presence of serum, while a cytokine-modulating effect of HNP was observed in the presence of serum and in whole blood, suggesting that this mechanism may function in vivo. Similarly, serum did not abrogate bactericidal activity of HNP. It was also demonstrated herein that HNP at 10 (-8) -10(-9) M, attenuated the inhibitory action of dexamethasone on TNF-alpha production. In parallel to monocyte studies, we have showed that HNP at concentrations ranging from 10(-9)M to 10(-6)M caused about 5-fold suppression of VCAM-1 expression in TNF-alpha-activated human umbilical vein endothelial cells, while the ICAM-1 expression was not affected. Our findings suggest that neutrophil defensins have the potential to modulate the inflammatory responses through regulation of cytokine production and adhesion molecule expression.
Assuntos
Moléculas de Adesão Celular/biossíntese , Citocinas/biossíntese , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/imunologia , Monócitos/efeitos dos fármacos , Monócitos/imunologia , Proteínas/farmacologia , Animais , Sequência de Bases , Moléculas de Adesão Celular/genética , Células Cultivadas , Citocinas/genética , Primers do DNA/genética , Defensinas , Dexametasona/farmacologia , Endotélio Vascular/metabolismo , Expressão Gênica/efeitos dos fármacos , Humanos , Molécula 1 de Adesão Intercelular/biossíntese , Molécula 1 de Adesão Intercelular/genética , Ligantes , Monócitos/metabolismo , Proteínas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Coelhos , Fator de Necrose Tumoral alfa/biossíntese , Fator de Necrose Tumoral alfa/genética , Molécula 1 de Adesão de Célula Vascular/biossíntese , Molécula 1 de Adesão de Célula Vascular/genéticaRESUMO
TNF-alpha and IL-1 were reported to be the most powerful inducers of IL-8 in a multitude of cells, including leukocytes. In this study, we investigated TNF-alpha- and IL-1-mediated regulation of IL-8 gene expression in non-fractionated PBMC, and purified monocyte (MO) and lymphocyte (LY) fractions. Our analysis revealed that purified human MO did not respond to exogenous TNF-alpha with the induction of IL-8 mRNA or protein, nor require endogenous TNF-alpha for IL-8 expression. In contrast, in the presence of exogenous IL-1alpha and IL-1beta a substantial enhancement of IL-8 mRNA and protein expression in MO was observed. Nevertheless, antibodies to IL-1alpha and IL-1beta were unable to downregulate the expression of IL-8 in resting adherent or Staphylococcus aureus Cowan 1 (SAC)-stimulated MO. In contrast with MO, purified LY and non-fractionated PBMC expressed IL-8 in response to exogenous TNF-alpha, similar to exogenous IL-1alpha and IL-1beta. As was seen with MO, antibodies to TNF-alpha, IL-1alpha and IL-1beta did not inhibit the expression of IL-8 in purified LY and non-fractionated PBMC stimulated with SAC and LPS. Taken together, our data demonstrate major differences in responsiveness of MO and LY to exogenous TNF-alpha and IL-1, and suggest relative autonomy of IL-8 gene expression in these cells that does not require accessory cytokines but can be induced directly by exogenous stimuli.