| 19171179 |
Delbro D, Westerlund A, Bjorklund U, Hansson E: In inflammatory reactive astrocytes co-cultured with brain endothelial cells nicotine-evoked Ca (2+) transients are attenuated due to interleukin-1beta release and rearrangement of actin filaments. Neuroscience. 2009 Mar 17;159(2):770-9. Epub 2009 Jan 9.
The aim of this study was to investigate whether nicotine acetylcholine receptors (nAChRs) are expressed in a more pronounced way in astrocytes co-cultured with microvascular endothelial cells from adult rat brain, compared with monocultured astrocytes, as a sign of a more developed signal transduction system. Also investigated was whether nicotine plays a role in the control of neuroinflammatory reactivity in astrocytes. Ca (2+) imaging experiments were performed using cells loaded with the Ca (2+) indicator Fura-2/AM. Co-cultured astrocytes responded to lower concentrations of nicotine than did monocultured astrocytes, indicating that they are more sensitive to nicotine. Co-cultured astrocytes also expressed a higher selectivity for alpha7nAChR and alpha4/beta2 subunits and evoked higher Ca (2+) transients compared with monocultured astrocytes. The Ca (2+) transients referred to are activators of Ca (2+)-induced Ca (2+) release from intracellular stores, both IP (3) and ryanodine, triggered by influx through receptor channels. The nicotine-induced Ca (2+) transients were attenuated after incubation with the inflammatory mediator lipopolysaccharide (LPS), but were not attenuated after incubation with the pain-transmitting peptides substance P and calcitonin-gene-related peptide, nor with the infection and inflammation stress mediator, leptin. Furthermore, LPS-induced release of interleukin-1beta (IL-1beta) measured by enzyme-linked immunosorbent assay (ELISA) was more pronounced in co-cultured versus monocultured astrocytes. Incubation with both LPS and IL-1beta further attenuated nicotine-induced Ca (2+) response. We also found that LPS and IL-1beta induced rearrangement of the F-actin filaments, as measured with an Alexa488-conjugated phalloidin probe. The rearrangements consisted of increases in ring formations and a more dispersed appearance of the filaments. These results indicate that there is a connection between a dysfunction of nicotine Ca (2+) signaling in inflammatory reactive astrocytes and upregulation of IL-1beta and the rearrangements of actin filaments in the cells. |
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