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Octreotide differentially modulates human Caco-2 intestinal epithelial cell proliferation and differentiation by
S A Sgambati1, A Zarif, M D Basson
1Department of Surgery, Yale University School of Medicine, University of Connecticut School of Medicine, New Haven 06520-8062, USA.
Abstract:
Somatostatin modulates gastrointestinal mucosal growth and differentiation indirectly via inhibition of bioactive peptides and directly by less well understood mechanisms. We studied the direct effects of the somatostatin analog octreotide on proliferation, brush-border enzyme activity, cell-matrix interactions and intracellular cAMP in Caco-2 human intestinal epithelial cells. Proliferation was assessed by cell counting and [3H]thymidine uptake. The brush-border enzymes alkaline phosphatase (AP) and dipeptidyl dipeptidase (DP) were quantitated by synthetic substrate digestion. Adhesion and migration on purified matrix proteins were also measured. Octreotide (10(-9)-10(-5)M) shortened doubling time (46.5 +/- 6.2% at 10(-5) M, n = 20, P < 0.0001) and stimulated [3H]thymidine uptake. Octreotide decreased intracellular cAMP by 19.4 +/- 5.0% (n = 7, P < 0.0001) while dibutyryl-cAMP (10(-6) M) prolonged doubling time by 10.1 +/- 1.5% (n = 8, P < 0.0001), and blocked the octreotide effect. Octreotide decreased AP and DP with maximal effect at 10(-6) M (36.8 +/- 8.3% and 20.5 +/- 9.1%, n > 7, P < 0.0005 respectively). However, mitomycin proliferative blockade prevented octreotide inhibition of AP and DP, suggesting that the mitogenic effects of octreotide had simply decreased average maturity of the cells. Octreotide did not alter Caco-2 adhesion, EGF-or matrix-modulated motility, or integrin surface expression. Octreotide appears to directly stimulate Caco-2 proliferation by decreasing cAMP. These proliferative effects modulate Caco-2 differentiation but do not affect cell-matrix interactions.
Insights
The somatostatin analog octreotide directly stimulates intestinal cell proliferation by reducing intracellular cAMP levels. This effect influences cell differentiation but not cell-matrix interactions.
Area of Science:
- Gastroenterology
- Cell Biology
- Molecular Pharmacology
Background:
- Somatostatin influences gastrointestinal mucosal growth and differentiation.
- Its direct mechanisms on intestinal epithelial cells are not fully understood.
- Octreotide is a somatostatin analog used to study these effects.
Purpose of the Study:
- To investigate the direct effects of octreotide on Caco-2 human intestinal epithelial cells.
- To examine octreotide's impact on cell proliferation, brush-border enzyme activity, cell-matrix interactions, and intracellular cAMP.
- To elucidate the signaling pathways involved in octreotide's action.
Main Methods:
- Caco-2 cells were treated with varying concentrations of octreotide.
- Cell proliferation was measured using cell counting and [3H]thymidine uptake.
- Brush-border enzyme activity (alkaline phosphatase and dipeptidyl dipeptidase) was quantified.
- Intracellular cAMP levels were measured.
- Cell adhesion and migration assays were performed.
Main Results:
- Octreotide significantly shortened cell doubling time and stimulated [3H]thymidine uptake, indicating increased proliferation.
- Octreotide decreased intracellular cAMP levels, and this effect was mimicked by dibutyryl-cAMP.
- Brush-border enzyme activity was reduced by octreotide, but this was linked to increased proliferation rather than direct enzyme inhibition.
- Octreotide did not affect cell adhesion, motility, or integrin expression.
Conclusions:
- Octreotide directly stimulates Caco-2 cell proliferation, primarily by decreasing intracellular cAMP.
- The proliferative effects of octreotide modulate Caco-2 cell differentiation.
- Octreotide does not appear to directly influence cell-matrix interactions in Caco-2 cells.