Calcineurin B1 Deficiency in Glial Cells Reduces Gastrointestinal Motility and Results in Maldigestion and/or Malabsorption in Mice.

Calcineurin is a Ca2+/calmodulin-dependent protein phosphatase abundantly expressed in the nervous system. To investigate the roles of calcineurin in glial cells, we previously generated glial calcineurin B1-conditional knockout (CKO) mice and found that these mice displayed dysfunction of enteric glial cells, mucosal degeneration and inflammation in the small intestine, and growth retardation and postweaning death, suggesting a novel role of calcineurin in enteric glial cells. Although these findings raised a possibility that abnormalities in calcineurin B1-deficient enteric glial cells may cause dysregulation of gastrointestinal motility and result in maldigestion and/or malabsorption in the CKO mice, these issues remain to be elucidated. In the present study, we showed that gastrointestinal motility was reduced in the CKO mice. Degeneration of mucosal epithelium was observed in the small intestine. Glucose levels were decreased in serum, whereas starch, glucose, and lipid levels were increased in feces. Thus, calcineurin B1 deficiency in glial cells reduces gastrointestinal motility, induces mucosal epithelium degeneration in the small intestine, and results in maldigestion and/or malabsorption in mice, further supporting the important role of calcineurin in enteric glial cells.

Calcineurin B1 Deficiency in Glial Cells Induces Mucosal Degeneration and Inflammation in Mouse Small Intestine.

Although calcineurin is abundantly expressed in the nervous system and involved in neurite extension and synaptic plasticity in neurons, little is known about its roles in glial cells. To investigate the roles of calcineurin in glial cells, we generated glial calcineurin B1-conditional knockout (CKO) mice and analyzed the abnormalities in the small intestine. The CKO mice were generated by crossing floxed calcineurin B1 mice with glial fibrillary acidic protein (GFAP)-Cre mice. The CKO mice exhibited growth retardation approximately from the third postnatal week and died mostly within the fourth postnatal week. The small intestine of the CKO mice was thin and hemorrhagic. The mucosal layer was degenerated and GFAP expression was reduced in the CKO small intestine. These pathological changes were associated with inflammation and increased intestinal permeability. In contrast, no apparent abnormalities were observed in the large intestine of the CKO mice. Nuclear factor of activated T cells failed to translocate into the nucleus after stimulation in enteric glial cells of the CKO small intestine. In conclusion, the calcineurin B1 deficiency in glial cells impairs the small intestine and leads to malnutrition and eventual death in mice, suggesting that calcineurin plays a novel and important role in enteric glial cells.