Introduction: Ophthalmic preservatives, such as polyquaternium-1 (PQ-1), are critical for the inhibition of growth of microbial contaminants in multi-dose bottles of topical medications. These antimicrobial agents must have a high efficacy against pathogenic organisms, while maintaining a favorable tolerability and safety profile. Areas covered: This review focuses on the ophthalmic preservative PQ-1. For comparison purposes, the most commonly used preservative, benzalkonium chloride (BAK), is also discussed. This survey focuses primarily on data collected during the past 10 years. Expert opinion: Effective drug delivery requires more than just an active ingredient that achieves its desired biological effect on end-target tissues. In addition, drugs must be stable in the containers that they are stored in, and must possess minimal undesired local and systemic side effects that can cause patients to decrease their adherence. In addressing these concerns, specifically in topical ophthalmic drops, one must take into account the active ingredients, vehicle components and preservatives. Medications with fewer adverse effects may lead to enhanced adherence to therapy; therefore, the induction of such adverse outcomes must be considered by physicians when treating patients with chronic ocular disease. Although BAK will continue to be used in ophthalmic medications, due to its familiarity and compatibility with a broad range of topical ocular formulations, PQ-1 is certainly a viable alternative in the preservative formulary armamentarium.
Everything from our high-tech lifestyles outdoor environmental factors, and the general aging of the population can lead to blepharitis, dry eye disease (DED) and meibomian gland dysfunction (MGD). Sustained tasks, such as reading, can reduce the blink rate to as low as five blinks per minute. This slow blink rate can cause additional stress on an ocular surface that is already compromised due to one of the aforementioned disorders.
purpose. To study the mRNA and pharmacology of a serotonin (5-HT) receptor positively coupled to adenylyl cyclase in normal, primary (P-CEPI), and immortalized human corneal epithelial cells (CEPI-17-CL4), by using numerous 5-HT agonists and antagonists. To determine and compare cloned human 5-HT7 receptor binding affinities of compounds with their functional potency data. methods. RT-PCR was used to detect the presence of an mRNA for the human 5-HT7 receptor in CEPI-17-CL4 cells. Receptor-mediated production of cAMP in cultured cells was measured using an enzyme immunoassay. Compound binding affinities were determined using [3H]-lysergic acid diethylamide ([3H]-LSD) binding to cell membranes of human embryonic kidney (HEK-293) cells expressing the cloned human 5-HT7 receptor. results. RT-PCR revealed the presence of a 5-HT7 receptor mRNA in CEPI-17-CL4 cells. Normal P-CEPI cells generated cAMP in response to 5-HT (−log EC50; pEC50 = 7.6), 5-carboxamidotryptamine (5-CT; pEC50 = 7.8), 5-methoxy-tryptamine (pEC50 = 7.0) and 5-methoxy-dimethyl-tryptamine (pEC50 = 5.7). In CEPI-17-CL4 cells, serotonergic agonists also stimulated cAMP production with different potencies (pEC50): 5-CT (7.4) > 5-HT (6.5) ≥ 5-methoxy-tryptamine (6.1) > 5-methoxy-dimethyl-tryptamine (5.4) ≥ 8-OH-DPAT (<5.0) = α-methyl-5-HT (<5.0). Various 5-HT receptor antagonists inhibited cAMP production induced by 5-CT in CEPI-17-CL4 cells with different potencies (pKi): methiothepin (8.5) > mesulergine (8.1) = metergoline (8.0) > spiperone (7.4) ≥ clozapine (7.2) = SB-258719 (7.2) > mianserin (6.9) > ketanserin (6.3). Antagonist pKi values in P-CEPI cells were methiothepin (8.7), spiperone (7.4) and SB-258719 (6.6). The rank order of affinity for displacement of [3H]-LSD from the cloned human 5-HT7 receptor was: methiothepin > ritanserin > mesulergine = clozapine ≥ metergoline = 5-HT > SB-258719 ≥ spiperone > mianserin ≥ ketanserin. The functional agonist and antagonist potency data obtained from CEPI-17-CL4 cells correlated well with cloned human 5-HT7 receptor binding affinity data (r = 0.69), with P-CEPI cell functional data (r = 0.85), and with functional potency data in the literature for the cloned human 5-HT7 receptor (r = 0.88). conclusions. These collective data support the presence of a pharmacologically defined, adenylyl cyclase-coupled 5-HT7 receptor in the CEPI-17-CL4 cells that may have relevance to physiological and/or pathologic functions of 5-HT7 receptors in the human cornea.
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 β-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 μM] > phenylephrine [EC50 > 10 μM for both] = dopamine [EC50 > 10 μM 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 = 2705 and 1980 nM] > atenolol [Ki > 4000 nM for both] (n = 3-7). These detailed pharmacological studies using a variety of agonists and antagonists further supported the presence of β2-adrenergic receptors in immortalized human NPE and TM cells.
Phospholipase C induced phosphoinositide (PI) turnover, intracellular Ca2+ ([Ca2+]i) mobilization and mitogen-activated protein (MAP) kinase activation by FP-class prostaglandin analogs was studied in normal human ciliary muscle (h-CM) cells. Agonist potencies obtained in the PI turnover assays were: travoprost acid ((+)-fluprostenol; EC50 = 2.6 ± 0.8 nM) > bimatoprost acid (EC50 = 3.6 ± 1.2 nM) > (±)-fluprostenol (EC50 = 4.3 ± 1.3 nM) >> prostaglandin F2α (PGF2α) (EC50 = 134 ± 17 nM) > latanoprost acid (EC50 = 198 ± 83 nM) > S-1033 (EC50 = 2930 ± 1420 nM) > unoprostone (EC50 = 5590 ± 1490 nM) > bimatoprost (EC50 = 9600 ± 1100 nM). Agonist potencies in h-CM cells correlated well with those previously obtained for the cloned human ciliary body-derived FP receptor (r = 0.96, p< 0.001) and that present on h-TM cells (r = 0.94, p< 0.0001). Travoprost acid, PGF2α and unoprostone also stimulated [Ca2+]i mobilization in h-CM cells with travoprost acid being the most potent agonist. MAP kinase activity was stimulated in the h-CM cells with the following rank order of activity (at 100 nM): travoprost acid > PGF2α > latanoprost acid > PGD2 > bimatoprost > latanoprost = bimatoprost acid = fluprostenol > PGE2 = S-1033 > unoprostone > PGI2. The PI turnover, [Ca2+]i mobilization and MAP kinase activation induced by several of these agonists was blocked by the FP receptor antagonist, AL-8810 (11β-fluoro-15-epiindanyl PGF2α) (e.g. Ki = 5.7 μM versus PI turnover). These studies have characterized the biochemical and pharmacological properties of the native FP prostaglandin receptor present on h-CM cells using three signal transduction mechanism assays and a broad panel of FP-class agonist analogs (including free acids of bimatoprost, travoprost and latanoprost) and the FP receptor antagonist, AL-8810.
The goal of these studies was to compare the effects of several prostaglandin (PG) receptor agonists on adenylyl cyclase activity in transformed human nonpigmented ciliary epithelial (NPE) cells. In order to define the pharmacology of the PG receptors present on these cells, cyclic AMP production was measured by both manual and robotic radioimmunoassay (RIA) techniques. In NPE cells, the rank order of potency for the PGs tested in the current study (n = up to 46) was PGE2 (EC50 = 67 nM) > 13,14-dihydro-PGE, (EC50 = 231 nM) > 11-deoxy-PGE1 (EC50 = 500 nM) = 16,16-dimethyl-PGE2 (EC50 = 872 nM) = 11-deoxy-16,16-dimethyl-PGE2 (EC50 = 1135 nM)>>PGF2α (EC50 > 10,000 nM) = PGD2 (EC50 >10,000 nM) = PGI2 (EC50 > 10,000 nM). The EP2-receptor selective PG, butaprost, exhibited a potency of 212 nM (Emax = 55%). The response to 1 μM PGE2 was antagonized by AH6809 (IC50 = ~ 50 μM, Kb = 4 μM). The relative potencies of the EP agonists mentioned above were significantly weaker in EbTr and NCB-20 cells expressing DP and IP receptors, respectively (1). These data provide a detailed pharmacological identification and characterization of EP2 receptors on NPE cells.
Various prostaglandin agonists representing various classes of receptor subtypes were evaluated for their ability to stimulate adenylyl cyclase via the endogenous DP receptor in embryonic bovine tracheal (EBTr) cells. Two antagonists were used to block the agonist‐induced cyclic AMP production. ZK118182 (EC 50 =16±4 n M ), RS‐93520 (EC 50 =23±4 n M ), SQ27986 (EC 50 =33±9 n M ), ZK110841 (EC 50 =33±5 n M ), BW245C (EC 50 =59±19 n M ) and PGD 2 (EC 50 =101±10 n M ) ( n =4–70) were the most potent agonists. Whilst most compounds were full agonists (E max =100% relative to PGD 2 ), BW245C was significantly more efficacious than PGD 2 (E max =121±3%; P <0.001) and RS‐93520 appeared to be a partial agonist (E max =64±9%; P <0.001). Agonists from the EP (e.g. enprostil; misoprostol; butaprost), FP (e.g. cloprostenol; fluprostenol; PHXA85), IP (iloprost; PGI 2 ) and TP (U46619) prostanoid receptor classes were weak agonists or inactive in the EBTr cell assay system. The DP‐receptor antagonist, BWA868C, showed a competitive antagonist profile with pA 2 values of 8.00±0.02 and 8.14±0.13 in Schild analyses with two structurally different agonists, BW245C and ZK118182, respectively ( n =3). AH6809, another purported DP‐receptor antagonist, weakly inhibited PGD 2 ‐ and ZK118182‐induced cyclic AMP production ( K i s=808±193 n M and 782±178 n M , respectively). The current studies have characterized the DP receptor positively coupled to adenylyl cyclase in EBTr cells using a wide range of agonist and antagonist prostaglandins. These data support the utility of the EBTr cell line as a useful tool for the evaluation of DP receptor agonists and antagonists and for profiling other classes of prostaglandins. British Journal of Pharmacology (1999) 127 , 204–210; doi: 10.1038/sj.bjp.0702490
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