Pilocarpine Induced Expression of Nitric Oxide Synthase in R18A5 Retinal Ganglion Cell Line

ABSTRACT

Pilocarpine is a direct cholinergic agonist and reduces intraocular pressure by enhancing aqueous outflow. A recent study reveals that pilocarpine induces apoptotic cell death in retinal ganglion cells; activation of bax and caspase-3 is a possible mechanism of the cell death. The objective of this study is to determine whether nitric oxide is involved in apoptotic retinal ganglion cell death which is induced by pilocarpine. R18A5 retinal ganglion cells were treated with 1 mM pilocarpine. After 20 hours of incubation, NADPH-d staining assay and immunocytochemistry of nNOS, iNOS, and NF-KB were performed. In retinal ganglion cells treated with pilocarpine, intense NADPH-d histochemical reactivity was present, whereas NADPH-d reactivity was weak in control. The immunoreactivity of iNOS was increased significantly and the immunoreactivity of nNOS was increased slightly in retinal ganglion cells treated with pilocarpine. The activation of NF-KB was demonstrated by staining of nuclei in retinal ganglion cells exposed to pilocarpine, whereas such features were not seen in untreated control cells. This study provides the first evidence that nitric oxide synthase is increased in retinal ganglion cells treated with pilocarpine, and nitric oxide may be a mediator of the cell death mechanism.