Splenectomy prevents brain orexin, ghrelin, or oxytocin but not GLP-1-induced improvement of intestinal barrier function in rats.

BACKGROUND

Accumulating evidence has suggested that neuropeptides such as orexin, ghrelin, or oxytocin act centrally in the brain to regulate intestinal barrier function through the vagus nerve. It has been reported that the vagal cholinergic anti-inflammatory pathway was blocked by splenectomy. In the present study, we therefore examined the effect of splenectomy on neuropeptides-induced improvement of increased intestinal permeability.

METHODS

Colonic permeability was determined in vivo by quantifying the absorbed Evans blue in colonic tissue for 15 min spectrophotometrically in rats.

RESULTS

Splenectomy increased colonic permeability. The increased permeability by splenectomy was significantly blocked by vagal activation induced by carbachol or 2-deoxy-d-glucose which was prevented by atropine, suggesting vagal activation could prevent colonic hyperpermeability in splenectomized rats. In the splenectomized rats, intracisternal injection of orexin, ghrelin, oxytocin, or butyrate failed to inhibit increased colonic permeability while intracisternal glucagon-like peptide-1 (GLP-1) analogue, liraglutide, potently blocked the increased colonic permeability in a dose-dependent manner. The liraglutide-induced improvement of increased colonic permeability was blocked by atropine in splenectomized rats. Intracisternal injection of GLP-1 receptor antagonist attenuated 2-deoxy-d-glucose-induced improvement of colonic hyperpermeability in splenectomized rats.

CONCLUSION

The present results suggested that the spleen is important in the improvement of intestinal barrier function by brain orexin, ghrelin or oxytocin, and butyrate. On the other hand, GLP-1 acts centrally in the brain to improve colonic hyperpermeability in a spleen-independent manner. All these results suggest that dual mechanisms (spleen dependent or independent) may exist for the brain-gut regulation in intestinal barrier function.