Forskolin upregulation of NOS I protein expression in porcine ciliary processes: a new aspect of aqueous humor regulation.

BACKGROUND

To determine whether nitric oxide synthase (NOS) protein expression can be modulated by forskolin in porcine ciliary processes.

METHOD: Western blot analysis using mouse monoclonal antibodies against NOS I (neuronal NOS or nNOS), NOS II (macrophage NOS or macNOS), and NOS III (endothelial NOS or eNOS) was performed in porcine ciliary processes. Expression of NOS I and II was also assessed in the presence or in the absence of 1 microM forskolin exposure (4 and 24 hours).

RESULTS

All three NOS isoforms could be detected in isolated porcine ciliary processes. Protein expression for NOS I was about 6 times higher than for NOS III and 15 times higher than for NOS II. In comparison to controls, after forskolin exposure, NOS I protein expression was increased by about 1.5-fold. No change could be observed in NOS II protein expression after forskolin exposure.

CONCLUSIONS

Nitric oxide is involved in transepithelial fluid transport of different organs (lung, kidney, colon, etc.) and is suspected to play a role in ciliary processes by modulating the aqueous humor production. The present study indicates that forskolin (which increases cAMP production) modulates NOS I protein expression in isolated porcine ciliary processes. These results suggest that selective inhibition of NOS I could be tried for reducing aqueous humor production. The clinical relevance requires further investigations.