RESUMEN
Lipopolysaccharide (LPS) induced tumor necrosis factor (TNF)-alpha production in human monocytes, which was dependent on activation of extracellular signal-regulated kinase (ERK), p38, c-Jun NH(2)-terminal kinase (JNK), and nuclear factor (NF)-kappa B. LPS-induced TNF-alpha production was inhibited by granulocyte colony-stimulating factor (G-CSF) and interleukin (IL)-10. G-CSF, like IL-10, exerted the inhibitory effect even when simultaneously added with LPS. Among the signaling pathways, signal transducer and activator of transcription 3 (STAT3) was selectively activated in monocytes stimulated by G-CSF or IL-10. G-CSF-mediated inhibition of LPS-induced TNF-alpha production as well as G-CSF-induced STAT3 phosphorylation and suppressor of cytokine signaling 3 mRNA expression were prevented by pretreatment of monocytes with AG-490, an inhibitor of Janus kinase 2. G-CSF did not affect LPS-induced activation of ERK, p38, JNK, and NF-kappa B, indicating that G-CSF affects the pathway downstream or independently of these signaling molecules. G-CSF-induced, but not IL-10-induced, STAT3 phosphorylation was attenuated in the presence of LPS. These findings suggest that G-CSF, like IL-10, inhibits LPS-induced TNF-alpha production in human monocytes through selective activation of STAT3, and the immunomodulation observed in vivo by G-CSF administration may be partly ascribed to the direct effect of G-CSF on monocyte functions.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Factor Estimulante de Colonias de Granulocitos/farmacología , Lipopolisacáridos/farmacología , Monocitos/metabolismo , Proteínas Proto-Oncogénicas , Transducción de Señal/fisiología , Transactivadores/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Células Cultivadas , Proteínas de Unión al ADN/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Retroalimentación Fisiológica/efectos de los fármacos , Retroalimentación Fisiológica/fisiología , Humanos , Interleucina-10/metabolismo , Interleucina-10/farmacología , Janus Quinasa 2 , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/fisiología , Monocitos/efectos de los fármacos , Monocitos/inmunología , Neutrófilos/efectos de los fármacos , Neutrófilos/inmunología , Neutrófilos/metabolismo , Fosforilación/efectos de los fármacos , Proteínas Tirosina Quinasas/efectos de los fármacos , Proteínas Tirosina Quinasas/metabolismo , Receptores de Factor Estimulante de Colonias de Granulocito/metabolismo , Factor de Transcripción STAT3 , Transducción de Señal/efectos de los fármacos , Transactivadores/efectos de los fármacos , Factor de Necrosis Tumoral alfa/efectos de los fármacosRESUMEN
Human neutrophils were found to express members of the inhibitor of apoptosis (IAP) family, namely cellular IAP1 (cIAP1), cIAP2, and X-linked IAP. Among these members, cIAP2 expression was selectively up-regulated by stimulation with granulocyte colony-stimulating factor (G-CSF), but not with granulocyte-macrophage CSF. The increased expression of cIAP2 mRNA was detected as early as 30 minutes after in vitro stimulation with G-CSF, and the elevated level of cIAP2 protein was detected at 1 hour. The elevated level of cIAP2 protein was also detected in peripheral blood neutrophils obtained from healthy donors receiving G-CSF administration. G-CSF-induced up-regulation of cIAP2 mRNA and protein, phosphorylation of signal transducer and activator of transcription 3 (STAT3), and the antiapoptotic effects were inhibited by pretreatment of cells with AG490, a specific inhibitor of Janus kinase 2 (JAK2). Mature neutrophils from a patient with chronic neutrophilic leukemia exhibited remarkable overexpression of cIAP2 mRNA and prolongation of survival, whereas cIAP2 mRNA expression and survival in mature neutrophils from patients with chronic myelogenous leukemia were essentially similar to those in normal neutrophils. These findings suggest that cIAP2 expression is up-regulated by G-CSF through activation of the JAK2-STAT3 pathway, and increased expression of cIAP2 protein may contribute to G-CSF-mediated antiapoptosis. In addition, overexpression of cIAP2 may be partly responsible for sustained neutrophilia at least in some cases of chronic neutrophilic leukemia.