Abstract
Purpose: :
Hydrogen sulfide (H2S), a colorless gas with pungent odor has been reported to exert pharmacological effects on neural and non-neural tissues from several mammalian species (Lowicka et al., Pharmacol Rep. 59: 4, 2007). Evidence from our laboratory shows that H2S donors can alter glutamatergic neurotransmission in isolated mammalian neural retina presumably via an effect on the adenylate cyclase pathway (Opere et al., IOVS 46: E-Abstract 2228, 2005; Njie et al., IOVS 49: E-Abstract 2005, 2008). The present study further investigates whether H2S donors can alter cyclic AMP production in rat retinal pigmented epithelial cells (RPE-J).
Methods: :
RPE-J cells derived from primary cultures of 7 day old Long-Evans rats were incubated with the cyclooxygenase inhibitor, flurbiprofen (3 µM) and the phosphodiesterase inhibitor isobutylmethylxanthine (2 mM) for 30 minutes prior to treatment with H2S donors, sodium hydrosulfide (NaHS), and sodium sulfide (Na2S) or forskolin (positive control) at different time periods. After termination of the reaction, cells were lysed and then prepared for cyclic AMP assays using an Enzyme Immunoassay (EIA) kit. Cyclic AMP production was expressed as pmol/mg of protein.
Results: :
In cells treated with Na2S (10 nM-10 µM), we observed a time-dependent increase in cyclic AMP concentrations over basal levels reaching a maximal effect of 150 % at 10 mins. Na2S (10 nM-10 µM) caused a concentration-dependent increase in cyclic AMP levels reaching a maximal response at 1 µM. Unlike Na2S, NaHS (1 nM-10 µM) produced an increase in cyclic AMP concentrations over basal levels reaching a maximum of 100% at 20 mins after treatment. NaHS (1 nM-100 µM) also produced a concentration-related increase in cyclic AMP levels in a manner similar to that observed with Na2S. The diterpene activator of adenylate cyclase, forskolin (10 µM) - caused a three-fold increase in cyclic AMP concentrations over basal levels in RPE-J cells.
Conclusions: :
H2S donors can increase cyclic AMP production in rat retinal pigmented epithelial cells, an effect that is similar to that previously reported in porcine and bovine neural retinae. It appears that H2S plays a regulatory role in signal transduction processes in mammalian retina.
Keywords: neurotransmitters/neurotransmitter systems • retinal pigment epithelium • second messengers: pharmacology/physiology