Activation of mitogen-activated protein kinase by cholinergic agonists and EGF in human compared with rat cultured conjunctival goblet cells.

PURPOSE

To compare activation of the p42/p44 mitogen-activated protein kinase (MAPK) by cholinergic agonists and epidermal growth factor (EGF) in cultured human and rat goblet cells.

METHOD

. Conjunctiva was removed from either humans during ocular surgery or male Sprague-Dawley rats and cultured in RPMI medium. These cells were incubated with the cholinergic agonist carbachol (10(-4) M) or EGF (10(-8) M) for various times. Before stimulation, cells were incubated with the EGF receptor (EGFR) inhibitor, AG1478 (10(-7) M) or the muscarinic M(3) receptor inhibitor, 4-diphenylacetoxy-N-(2-chloroethyl)-piperidine hydrochloride (4-DAMP; 10(-5) M) for 10 minutes. Proteins were analyzed by Western blot analysis, using antibodies specific to phosphorylated (activated) p42/44-MAPK or total p42-MAPK. Immunoreactive bands were quantified, and data were expressed as percentage of increase over basal.

RESULTS

Carbachol (10(-4) M) increased MAPK activity in human and rat cultured goblet cells in a time-dependent manner, increasing pMAPK with a maximum at 10 minutes. EGF (10(-8) M) activated MAPK in human and rat goblet cells in a time-dependent manner with a maximum at 5 minutes. Carbachol- and EGF-induced activation of pMAPK was completely inhibited by AG1478 in cultured conjunctival goblet cells from both species. Carbachol-induced MAPK activity was also completely inhibited by 4-DAMP in both species.

CONCLUSIONS

In human and rat cultured conjunctival goblet cells, cholinergic agonists and EGF activate MAPK with a similar time dependency, this activation is receptor mediated, and cholinergic agonists transactivate the EGF receptor. Thus, rat cultured conjunctival goblet cells can be used as a model to study human conjunctival goblet cells.