Adenylyl Cyclase Activity Mediated by β-Adrenoceptors in Immortalized Human Trabecular Meshwork and Non-Pigmented Ciliary Epithelial Cells

Abstract

Non-pigmented ciliary epithelial (NPE) and trabecular meshwork (TM) cells are important in maintaining normal aqueous humor dynamics through the inflow and outflow routes, respectively. The current studies were undertaken to evaluate the ability of several beta-adrenergic receptor agonists to stimulate various antagonists to inhibit cAMP production in cultured immortalized human TM and NPE cells using an automated enzyme immunoassay. Isoproterenol was the most potent agonist in both the NPE and TM cells. The rank order of potency of agonists in NPE and TM cells, respectively, was: isoproterenol [EC50 = 37 and 66 nM] > epinephrine [EC50 = 112 and 526 nM] > albuterol [EC50 = 426 and 785 nM] > norepinephrine [EC50 = 3 and > 10 microM] > phenylephrine [EC50 > 10 microM for both] = dopamine [EC50 > 10 microM for both](n = 3-19). The isoproterenol-induced cAMP production was inhibited by various antagonists with the following rank order of potency in NPE and TM cells, respectively: propranolol [Ki = 0.2 and 0.3 nM] = ICI-118551 [Ki = 0.5 and 0.4 nM] > levobunolol [Ki = 1.1 and 2.1 nM] > levobetaxolol [Ki = 13 and 14 nM] = racemic betaxolol [Ki = 43 and 19 nM] > dextrobetaxolol [Ki = 2,705 and 1,980 nM] > atenolol [Ki > 4,000 nM for both] (n = 3-7). These detailed pharmacological studies using a variety of agonists and antagonists further supported the presence of beta2-adrenergic receptors in immortalized human NPE and TM cells.

Melatonin and Its Analog 5-Methoxycarbonylamino-N-Acetyltryptamine Potentiate Adrenergic Receptor-Mediated Ocular Hypotensive Effects in Rabbits: Significance for Combination Therapy in Glaucoma

“…Traditionally, b-adrenergic receptors have been described as modulators of IOP by changing the intracellular levels of cAMP in nonpigmented epithelial cells (Crider and Sharif, 2002). This has permitted the design and discovery of new b-adrenergic receptors antagonists to reduce IOP (Sharif et al, 2001).…”

Indirect Sympatholytic Actions at β-Adrenoceptors Account for the Ocular Hypotensive Actions of Cannabinoid Receptor Agonists

“…However, it should be noted that although CB 1 was found to colocalize with adrenergic inputs in the anterior eye, the bulk of CB 1 staining did not overlap with the inputs, suggesting that CB 1 may have additional postsynaptic (or nonsynaptic) functions. Recent work has demonstrated that CB 1 receptors heterodimerize with ␤ 2 AR receptors (Hudson et al, 2010), and because both of these receptors are expressed within the ciliary body epithelium (Straiker et al, 1999;Stamer et al, 2001;Crider and Sharif, 2002), the possibility that CB 1 /␤ 2 AR heterodimerization within the ciliary epithelial cells contributes to the ocular hypotensive properties of cannabinoids cannot be completely ruled out.…”

A3 adenosine and CB1 receptors activate a PKC‐sensitive Cl− current in human nonpigmented ciliary epithelial cells via a Gβγ‐coupled MAPK signaling pathway

“…These SV40-transformed NPCE cells are functionally similar to both untransformed primary NPCE cells (Coca-Prados & Wax, 1986) and epithelial cells of the intact ciliary body (Yantorno et al, 1989), with preservation of ion transport systems (Delamere et al, 1993;Patil et al, 2001) and GPCRs (Coca-Prados & Wax, 1986;Crook et al, 1992;Mitchell et al, 1999;Crider & Sharif, 2002).…”