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Mediators of interleukin-1 beta action Na(+)-K(+)ATPase in Caco-2 cells
Rana Mahmoud Al-Sadi1, Sawsan Ibrahim Kreydiyyeh
1Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Beirut-Lebanon.
Abstract:
Interleukin1-beta has been demonstrated previously to reduce the activity and expression of the Na(+)-K(+) pump in the rat jejunum and colon. This work attempts to elucidate the signal transduction pathway underlying its effect using Caco-2 cells. IL-1beta reduced, in these cells also, the activity and expression of ATPase, in a dose and time-dependent manner. The down-regulatory effect of the cytokine on the ATPase was not evident, when p38 MAP kinase was inhibited, but appeared in presence of inhibitors of MEK and NFkappaB, although activation of NF-kappaB was demonstrated by western blot analysis. The effect of IL-1beta on the pump disappeared in the presence of indomethacin, a COX inhibitor. Exogenous PGE2 reduced the expression of the pump within 15 minutes, and this effect was still apparent when p38MAPK was inhibited. Curcumin, a JNK/AP-1 inhibitor, partially abolished the effect of IL-1beta on ATPase expression but did not interfere with the effect of PGE2. These results indicate that IL-1beta reduces the expression of ATPase independently of NFkB but, through a major pathway involving p38 and COX-2/PGE2, and another pathway involving JNK/AP1.
Insights
Interleukin-1 beta (IL-1beta) reduces Na(+)-K(+) ATPase expression in Caco-2 cells. This effect involves p38 MAP kinase, COX-2/PGE2, and JNK/AP-1 signaling pathways, independent of NF-kappaB.
Area of Science:
- Cellular and Molecular Biology
- Gastrointestinal Physiology
- Signal Transduction
Background:
- Interleukin-1 beta (IL-1beta) is known to decrease Na(+)-K(+) pump activity and expression in the rat jejunum and colon.
- Understanding the specific signaling cascades mediating IL-1beta's effects is crucial for comprehending intestinal epithelial cell regulation.
Purpose of the Study:
- To elucidate the signal transduction pathway through which Interleukin-1 beta (IL-1beta) down-regulates the Na(+)-K(+) ATPase in Caco-2 cells.
- To investigate the roles of p38 MAP kinase, MEK, NF-kappaB, COX-2/PGE2, and JNK/AP-1 in mediating IL-1beta's effects.
Main Methods:
- Utilized Caco-2 cell lines to study the effects of IL-1beta on Na(+)-K(+) ATPase activity and expression.
- Employed specific inhibitors for p38 MAP kinase, MEK, NF-kappaB, COX, and JNK/AP-1 to dissect signaling pathways.
- Western blot analysis was used to confirm NF-kappaB activation.
- Investigated the effects of exogenous PGE2 and curcumin (JNK/AP-1 inhibitor).
Main Results:
- IL-1beta dose- and time-dependently reduced Na(+)-K(+) ATPase activity and expression in Caco-2 cells.
- The inhibitory effect of IL-1beta was dependent on p38 MAP kinase and COX-2/PGE2 signaling.
- IL-1beta's effect was partially mediated by JNK/AP-1 but independent of NF-kappaB activation.
- Exogenous PGE2 mimicked IL-1beta's effect on ATPase expression, independent of p38 MAP kinase.
Conclusions:
- IL-1beta negatively regulates Na(+)-K(+) ATPase expression in intestinal cells via distinct signaling pathways.
- A major pathway involves p38 MAP kinase and the COX-2/PGE2 axis.
- A secondary pathway mediated by JNK/AP-1 also contributes to the down-regulation, independent of NF-kappaB.