| Increased intraocular pressure(IOP) is one of the main risk factor of the onset and progress of glaucoma. To decrease IOP, either by surgery or by ocular hypotensive agents is the main goal of glaucoma therapy. Aqueous humor production inhibition by drugs is still one of the main strategy in the IOP control.Ciliary epithelium, where the aqueous humor is formed, consists of two apically juxtaposed cell layers, the non-pigmented epithelium (NPE) layer (on the side of the aqueous humor) and the pigmented epithelium (PE) layer (on the side of the stroma). Till now, the mechanism of aqueous humor formation is still unclear. More and more evidences showed that most of the aqueous humor production results from transepithelial ionic currents from the stroma into the aqueous humor followed by a passive osmotic water inflow into the posterior chamber of the eye.Anions, inparticular HCO3 and Cl play important role in the process of aqueous humor production.Nitric oxide (NO),an active intracellular messenger produced in the tissue from L-arginine when catalyzed by the NO sythase (NOS),is involved in a variety of physiological and pathalogical processes of the body. NOS is widely distributed in the eye and NO plays important roles in the processes of the ocular blood flow regulation, IOP control, visual transduction, ocular inflammation, neuronal cytotoxicity and immune response, etc.It has been shown that NO modulates aqueous dynamics of the eye by, at least, increasing the outflow of the aqueous humor. However, the role of NO in the aqueous humor production is still unkown and the data on this is still rare.Nevertheless,as it has been reported that in other tissues NO modulates fluid secretion, results from immunohistochemistry and electrophysiology studies illustrated that NO might be involvedin the modulation of aqueous humor production and possibly mediate the effect in aqueous homor dynamics induced by some pharmacological agents such as cyclic AMP or isoproterenol.The purpose of this study is to investigate the modulation of NO production in ciliary processes and the role played by NO in the transepithelial inoic transport, which related to aqueous humor production, in ciliary epithelial bilayers. This study will consist four parts as following:1 ) Modulation of NOS expression by forskolin (an adenylylcyclase activator) and brimonidine (an a 2-adrenoceptor agonist) in isolated porcine ciliary processes.2) Modulation of nitrite production in isolated pig ciliary processes: Effect of forskolin and brimonidine.3 ) Assessment of transepithelial short circuit currents in human and porcine isolated ciliary bodies: Effect of hypotensive agents.4 Modulation of short-circuit current by NO-cyclic guanylate -protein kinase G in isolated porcine ciliary processes.The results of this study will benefit the understanding of the molecular mechanism of aqueous homor production and the glaucamatic change of the eye, as well as the modulation role of NO in aqueous humor formation and the mechanism of some ocular hypotensive agents. In addition.this study might be able to help the drugs design targeting better IOP control which will besurely benefit the glaucoma patients worldwide. PART I.Modulation of Nitric Oxide Synthase Expression by Forskolin and Brimonidine inIsolated Porcine Ciliary ProcessesPURPOSE. To determine whether nitric oxide synthase (NOS) protein expression can be modulated by forskolin and brimonine in isolated porcine ciliary processes.METERIALS AND METHODS: Western blot analysis using mouse monoclonal antibodies against NOS I (neuronal NOS or nNOS), NOS II (macrophage NOS or macNOS), and NOS HI (endothelial NOS or eNOS) was performed in porcine ciliary processes. In the presence or absence of brimonidine (1 M), expression of NOS I, II and III was also assessed when exposed to 1 DM forskolin (24 hours).RESULTS: All three NOS isoforms could be detected in isolated porcine ciliary processes. Protein expression for NOS I was about 2 times higher than for NOS...
|
PDF Full Text Request