NMDA receptors influence the intracellular calcium concen‐tration and the expression of differentiation markers in HaCaT cells

Abstract

Ionotropic glutamate receptors (ligand‐gated, ion‐channel proteins) of the N‐methyl‐d‐aspartate (NMDA) receptor type could enable a transmembranous calcium influx from the extracellular space. Though ionotropic glutamate receptors are predominantly neuronal receptors, they are also expressed in non‐neuronal tissues like keratinocytes. Therefore, investigations were performed to study the function of NMDA receptors in HaCaT cells. The intracellular calcium concentration of HaCaT cells was studied under the influence of the selective receptor agonist NMDA and the selective NMDA antagonist MK‐801. The proliferation of HaCaT cells was investigated using the crystal‐violet method. Furthermore, the expression of Cytokeratin 10 and Filaggrin was examined in HaCaT cells after blocking NMDA receptors with MK‐801. Using NMDA, there was a significant increase in the number of HaCaT cells showing elevated intracellular calcium concentration, at a dose between 25 µm and 1 mm (up to 84.6% of cells). The NMDA‐associated calcium influx could be significantly suppressed by prior application of MK‐801. There was no influence of NMDA on the proliferation of HaCaT cells. There was also no cytotoxic effect of NMDA (up to 1 mm). The expression of Cytokeratin 10 and Filaggrin could be suppressed by blocking NMDA receptors with MK‐801. The investigations show that glutamate receptors of the NMDA‐type play a role in the differentiation of HaCaT cells by regulating their intracellular calcium concentration.