Galanin Causes Cl⁻ Secretion in the Human Colon: Potential Significance of Inflammation‐Associated NF‐κB Activation on Galanin‐1 Receptor Expression and Function

Abstract

Galanin is widely distributed in enteric nerves and nerve terminals throughout the gastrointestinal (GI) tract. Within the GI tract galanin is best known for its ability to alter smooth muscle contractility and regulate intestinal motility. However, recent studies also indicate that galanin can modulate epithelial ion transport. We previously showed that epithelial cells lining the human GI tract, including those of colonic origin, express Gal1 galanin receptors (Gal1-R). We herein demonstrate that epithelial cells lining the human colon only express Gal1-R receptors and do not express other galanin receptor subtypes. We previously showed that Gal1-R expression was transcriptionally regulated by the transcription factor NF-kappa B. Consistent with this transcription factor being activated in a number of inflammatory conditions, we show increased colonic Gal1-R expression in patients with colitis due to a variety of causes. To further evaluate the physiology of Gal1-R activation, we studied this receptor expressed by the human colon epithelial cell line T84. Gal1-R activation resulted in a dose-dependent increase in Cl- secretion; whereas infection of T84 cells with pathogens known to activate NF-kappa B augmented Gal1-R expression and Cl- secretion. Thus, galanin acts as a secretagogue in epithelial cells lining the human colon, with alterations in Gal1-R expression possibly playing an important role in the diarrhea associated with various inflammatory processes affecting the GI tract.

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