Cyclic AMP dysregulates intestinal epithelial cell restitution through PKA and RhoA

Mucosal homeostasis is dependent on the establishment and maintenance of the cell-cell contacts that comprise the physiological barrier. Breaks in the barrier are linked to multiple diseases such as inflammatory bowel disease. While increased cyclic adenosine monophosphate (cAMP) levels limit inflammation by decreasing leukocyte infiltration, the effects of elevated cAMP on intestinal epithelial repair are unknown.

Restitution in animals administered rolipram was monitored by microscopic examination after laser wounding of the intestinal epithelium or in mice treated with dextran sodium sulfate (DSS). In vitro analysis was conducted using IEC6 and T84 cells to determine the role of elevated cAMP in altering Rho-dependent cellular migration signaling pathways.

We show that treatment with rolipram, forskolin, and cAMP analogs decrease intestinal epithelial cell migration in vitro. In vivo cell imaging revealed that increased cAMP resulted in a decreased cellular migration rate, with cells at the edge displaying the highest activity. As expected, elevated cAMP elicited increased protein kinase A (PKA) activity, in turn resulting in the inactivation and sequestration of RhoA and decreased actin reorganization. The ablation of restitution by cAMP was not restricted to cell culture, as forskolin and rolipram treatment significantly decreased epithelial microwound closure induced by the two photon confocal injury model.

Together, these data suggest that administration of cAMP-elevating agents paradoxically decrease infiltration of damage-causing leukocytes while also preventing epithelial repair and barrier maintenance. We propose that treatment with cAMP-elevating agents severely limits mucosal reepithelialization and should be contraindicated for use in chronic inflammatory bowel disorders.