RESUMEN
Interleukins (IL), aside from their role in the regulation of the immune cascade, they have also been shown to modulate intestinal transport function. IL-1ß is a potent inflammatory cytokine involved in many important cellular functions. The aim of this work was to study the in vitro effect of IL-1ß on d-galactose transport across intestinal epithelia in rabbit jejunum and Caco-2 cells. The results showed that d-galactose intestinal absorption was diminished in IL-1ß treated jejunum rabbits without affecting the Na(+), K(+)-ATPase activity. The presence of IL-1 cell-surface receptors was confirmed by addition to tissue of a specific IL-1 receptor antagonist (IL-1ra). The cytokine did not inhibit either the uptake of d-galactose nor modified the sodium-glucose transport (SGLT1) protein levels in the brush border membrane vesicles, suggesting an indirect IL effect. The IL-inhibition was significantly reversed in the presence of inhibitors of protein kinase C (PKC) and mitogen-activated protein kinases (MAPKs). The proteasome selective inhibitor completely abolished the IL-effect. Furthermore, the cytokine inhibition on galactose transport related to NF-kB activation was also confirmed in Caco-2 cells. In summary, the direct addition of IL-1ß to intestinal epithelia inhibits d-galactose transport by a possible reduction in the SGLT1 activity. This event may be mediated by several transduction pathways activated during the inflammatory processes related to several protein kinases and nuclear factor, NF-kB. The IL-effect is independent of hormonal milieu and nervous stimuli.
Asunto(s)
Galactosa/metabolismo , Interleucina-1beta/farmacología , Mucosa Intestinal/metabolismo , FN-kappa B/fisiología , Proteína Quinasa C/fisiología , Animales , Transporte Biológico , Células CACO-2 , Proteínas Quinasas Dependientes de AMP Cíclico/fisiología , Humanos , Sistema de Señalización de MAP Quinasas , Masculino , Conejos , Transportador 1 de Sodio-Glucosa/fisiologíaRESUMEN
BACKGROUND/AIMS: Recent studies from our laboratory have shown that nitric oxide is involved in the IL-1ß-induced inhibition of D-fructose intestinal transport in rabbits. The aim of this work was to further the studies of IL-1ß effect on D-galactose absorption in a septic state induced by intravenous administration of this cytokine. METHODS: Galactose intestinal absorption was assessed employing three techniques: sugar uptake in jejunum everted rings, transepithelial flux in Ussing-type chambers and uptake assays in brush border membrane vesicles. The level of the Na(+)/D-glucose cotransporter (SGLT1) expression was analyzed by Western blot. RESULTS: In sepsis condition the body temperature was increased and studies on cellular intestinal integrity have not shown modifications in the brush border membrane. However, D-galactose absorption across mucosa of jejunum was diminished in IL-1ß treated rabbits. The levels of SGLT-1 were no significantly different in both animal groups (control and IL-1ß treated), indicating that the cytokine could induce a reduction in the SGLT-1 functionality. The inhibition was significantly reversed by the activation of several PKC, PKA, MAPKs and nuclear factor (NF)-ĸB inhibitors administered 15 min before the IL-1ß. CONCLUSION: The inhibitory effect of IL-1ß on D-galactose absorption across mucosal side of enterocyte could be mediated by the activation of several kinases and nuclear factor (NF)-ĸB.
Asunto(s)
Galactosa/metabolismo , Interleucina-1beta/fisiología , Absorción Intestinal , Animales , Cromonas/farmacología , Proteínas Quinasas Dependientes de AMP Cíclico/antagonistas & inhibidores , Genisteína/farmacología , Técnicas In Vitro , Indoles/farmacología , Interleucina-1beta/farmacología , Mucosa Intestinal/metabolismo , Yeyuno/metabolismo , Yeyuno/patología , Masculino , Maleimidas/farmacología , Microvellosidades/metabolismo , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Morfolinas/farmacología , FN-kappa B/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteína Quinasa C/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/farmacología , Conejos , Sepsis/metabolismo , Transportador 1 de Sodio-Glucosa/metabolismoRESUMEN
Lipopolysaccharide (LPS) is an endotoxin comprising part of the cell wall of Gram-negative bacteria. It is able to induce a septic state and the release of several pro-inflammatory cytokines that are known to be responsible for hormonal changes in humans and animals. The aim of this study was to evaluate changes in plasma adrenocorticotrophic hormone (ACTH), corticosterone and cortisol levels in a rabbit model in which sepsis was induced by the intravenous administration of LPS. The possible involvement of several protein kinases, namely protein kinase A (PKA), C (PKC) and mitogen-activated protein kinases (MAPKs), and proteasome was also assessed. The results indicated that LPS induced significant increases in plasma ACTH, corticosterone and cortisol concentrations in rabbits. Moreover, protein kinases and proteasome seemed to mediate the hormone response to LPS as treatment with specific inhibitors prior to LPS administration was able to reduce, delay, or, in some cases, inhibit the hormone increases. The findings may help to construct strategies to protect and treat animals with endotoxaemia.