Ocular Hypotensive FP Prostaglandin (PG) Analogs: PG Receptor Subtype Binding Affinities and Selectivities, and Agonist Potencies at FP and Other PG Receptors in Cultured Cells

How latanoprost changed glaucoma management

Glaucoma is currently considered one of the leading causes of severe visual impairment and blindness worldwide. Topical medical therapy represents the treatment of choice for many glaucoma patients. Introduction of latanoprost, 25 years ago, with an entirely new mechanism of action from that of the antiglaucoma drugs used up to that time was a very important milestone. Since then, due mainly to their efficacy, limited systemic side effects and once daily dosing, prostaglandin analogues (PGAs) have become as the first-choice treatment for primary open-angle glaucoma. PGAs are in general terms well tolerated, although they are associated with several mild to moderate ocular and periocular adverse events. Among them, conjunctival hyperemia, eyelash changes, eyelid pigmentation, iris pigmentation and hypertrichosis around the eyes are the most prevalent. The objective of this paper is to review the role of PGAs in the treatment of glaucoma over the 25 years since the launch of Latanoprost and their impact on clinical practice outcomes.

Prostaglandin F2α Affects the Cycle of Clock Gene Expression and Mouse Behavior

Prostaglandins are bioactive compounds, and the activation of their receptors affects the expression of clock genes. However, the prostaglandin F receptor (Ptgfr) has no known relationship with biological rhythms. Here, we first measured the locomotor period lengths of Ptgfr-KO (B6.129-Ptgfrtm1Sna) mice and found that they were longer under constant dark conditions (DD) than those of wild-type (C57BL/6J) mice. We then investigated the clock gene patterns within the suprachiasmatic nucleus in Ptgfr-KO mice under DD and observed a decrease in the expression of the clock gene cryptochrome 1 (Cry1), which is related to the circadian cycle. Moreover, the expression of Cry1, Cry2, and Period2 (Per2) mRNA were significantly altered in the mouse liver in Ptgfr-KO mice under DD. In the wild-type mouse, the plasma prostaglandin F2α (PGF2α) levels showed a circadian rhythm under a 12 h cycle of light-dark conditions. In addition, in vitro experiments showed that the addition of PTGFR agonists altered the amplitude of Per2::luc activity, and this alteration differed with the timing of the agonist addition. These results lead us to hypothesize that the plasma rhythm of PGF2α is important for driving clock genes, thus suggesting the involvement of PGF2α- and Ptgfr-targeting drugs in the biological clock cycle.

Prostaglandin analogs in ophthalmology

Glaucoma is a major cause of irreversible blindness worldwide. Reducing intraocular pressure (IOP) is currently the only approach to prevent further optic nerve head damage. Pharmacotherapy is the mainstay of treatment for glaucoma patients. In recent years, a significant milestone in glaucoma treatment has been a transition to prostaglandin analogs (PGAs) as the first line of drugs. The rapid shift from traditional β-blockers to PGAs is primarily due to their excellent efficacy, convenient once-a-day usage, better diurnal control of IOP, and systemic safety profiles. This review article aims to provide information regarding the various PGAs in practice and also the newer promising drugs.

Ocular Biomechanics and Glaucoma

Biomechanics is a branch of biophysics that deals with mechanics applied to biology. Corneal biomechanics have an important role in managing patients with glaucoma. While evidence suggests that patients with thin and stiffer corneas have a higher risk of developing glaucoma, it also influences the accurate measurement of intraocular pressure. We reviewed the pertinent literature to help increase our understanding of the biomechanics of the cornea and other ocular structures and how they can help optimize clinical and surgical treatments, taking into consideration individual variabilities, improve the diagnosis of suspected patients, and help monitor the response to treatment.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress?

Purpose: Ocular biomechanics is an assessment of the response of the structures of the eye to forces that may lead to disease development and progression, or influence the response to surgical intervention. The goals of this review are (1) to introduce basic biomechanical principles and terminology, (2) to provide perspective on the progress made in the clinical study and assessment of ocular biomechanics, and (3) to highlight critical studies conducted in keratoconus, laser refractive surgery, and glaucoma in order to aid interpretation of biomechanical parameters in the laboratory and in the clinic.Methods: A literature review was first conducted of basic biomechanical studies related to ocular tissue. The subsequent review of ocular biomechanical studies was limited to those focusing on keratoconus, laser refractive surgery, or glaucoma using the only two commercially available devices that allow rapid assessment of biomechanical response in the clinic.Results: Foundational studies on ocular biomechanics used a combination of computer modeling and destructive forces on ex-vivo tissues. The knowledge gained from these studies could not be directly translated to clinical research and practice until the introduction of non-contact tonometers that quantified the deformation response of the cornea to an air puff, which represents a non-destructive, clinically appropriate load. The corneal response includes a contribution from the sclera which may limit corneal deformation. Two commercial devices are available, the Ocular Response Analyzer which produces viscoelastic parameters with a customized load for each eye, and the Corvis ST which produces elastic parameters with a consistent load for every eye. Neither device produces the classic biomechanical properties reported in basic studies, but rather biomechanical deformation response parameters which require careful interpretation.Conclusions: Research using clinical tools has enriched our understanding of how ocular disease alters ocular biomechanics, as well as how ocular biomechanics may influence the pathophysiology of ocular disease and response to surgical intervention.

Cytotoxicity, Mitochondrial Functionality, and Redox Status of Human Conjunctival Cells after Short and Chronic Exposure to Preservative-Free Bimatoprost 0.03% and 0.01%: An In Vitro Comparative Study

Prostaglandin analogues (PGAs), including bimatoprost (BIM), are generally the first-line therapy for glaucoma due to their greater efficacy, safety, and convenience of use. Commercial solutions of preservative-free BIM (BIM 0.03% and 0.01%) are already available, although their topical application may result in ocular discomfort. This study aimed to evaluate the in vitro effects of preservative-free BIM 0.03% vs. 0.01% in the human conjunctival epithelial (HCE) cell line. Our results showed that long-term exposure to BIM 0.03% ensues a significant decrease in cell proliferation and viability. Furthermore, these events were associated with cell cycle arrest, apoptosis, and alterations of ΔΨ_m. BIM 0.01% does not exhibit cytotoxicity, and no negative influence on conjunctival cell growth and viability or mitochondrial activity has been observed. Short-time exposure also demonstrates the ability of BIM 0.03% to trigger reactive oxygen species (ROS) production and mitochondrial hyperpolarisation. An in silico drug network interaction was also performed to explore known and predicted interactions of BIM with proteins potentially involved in mitochondrial membrane potential dissipation. Our findings overall strongly reveal better cellular tolerability of BIM 0.01% vs. BIM 0.03% in HCE cells.

Comparison of Soluble and Liposome Encapsulated, Sustained Release Latanoprost for Focal Adipose Reduction

Background: To address the lack of non-cytotoxic, non-surgical options to treat undesirable focal adiposity of the face, we propose use of the anti-glaucoma medication and prostaglandin F2α analogue latanoprost, which has a well-described side effect of periorbital adipose shrinkage. Objective: To evaluate the safety and efficacy of soluble and liposomal latanoprost for focal fat reduction. Approach: To compare efficacy, single administrations of either the FDA-approved cytolytic drug deoxycholic acid (DOCA), latanoprost, or liposomal latanoprost were injected into ob/ob mouse inguinal fat pads. Study outcomes included mouse weight, inguinal fat pad volume, architecture, and cytotoxicity. Results: Both DOCA and soluble latanoprost significantly reduced inguinal fat pad volume whereas liposome encapsulation reduced inguinal fat pad volume insignificantly over the 14-day study period. Hematoxylin and eosin demonstrated effective reduction in adipocyte volume without histologic evidence of cytolysis or inflammation whereas DOCA caused dermal ulcerations, adipocyte lysis, and increased tissue inflammation. Conclusion: Latanoprost reduced fat volume without inducing cell lysis or inflammation.

The Roles Played by FP/EP3 Receptors During Pressure-lowering in Mouse Eyes Mediated by a Dual FP/EP3 Receptor Agonist

Purpose

We investigated the intraocular pressure (IOP)-lowering effect of topical sepetaprost (SPT), a dual agonist of the FP and EP3 receptors. We explored whether certain receptors mediated the hypotensive effect of SPT and outflow facility changes in C57BL/6 mice (wild-type [WT]) and FP and EP3 receptor-deficient mice (FPKO and EP3KO mice, respectively).

Methods

IOP was measured using a microneedle. Outflow facility was measured using a two-level, constant-pressure perfusion method.

Results

SPT significantly reduced IOP for 8 hours after administration to WT mice. The 2-hour IOP reductions afforded by latanoprost were 15.3 ± 2.5, 1.8 ± 2.0, and 12.3 ± 2.4% in WT, FPKO, and EP3KO mice, respectively; the SPT figures were 13.6 ± 2.1, 5.9 ± 2.7, and 6.6 ± 2.6%, respectively. Latanoprost-mediated IOP reduction was significantly decreased in FPKO mice, and SPT-mediated IOP reduction was reduced in both FPKO and EP3KO mice. At 6 hours after administration, latanoprost did not significantly reduce the IOP in any tested mouse strain. SPT-mediated IOP reduction was reduced in both FPKO and EP3KO mice. IOP reduction at 6 hours was significantly higher after simultaneous administration of selective FP and EP3 receptor agonists, but IOP did not fall on administration of (only) a selective EP3 receptor agonist. SPT significantly increased outflow facility in WT mice, but less so in FPKO and EP3KO mice.

Conclusions

The IOP-lowering effect of SPT lasted longer than that of latanoprost. Our data imply that this may be attributable to augmented outflow facility mediated by the FP and EP3 receptors.

[Neuroprotective properties of latanoprost]

Glaucoma is the main cause of irreversible blindness in the world. Latanoprost - an ester prodrug of prostaglandin F_2α (PGF_2α) - was the first prostaglandin analogue used to treat glaucoma. The review shows that latanoprost possesses direct neuroprotective properties such as blocking the entry of calcium ions into neurons and inhibiting the action of caspase-3, inhibiting the activity of cyclooxygenase and activation of polypeptide 2B1 (OATP2B1) and Klotho protein. It is emphasized that when the drug is instilled into the eye, the concentration of the drug inside the vitreous body is twice as high as what is required to ensure the survival of retinal ganglion cells.

A Review of Prostanoid Receptors: Expression, Characterization, Regulation, and Mechanism of Action

Prostaglandin signaling controls a wide range of biological processes from blood pressure homeostasis to inflammation and resolution thereof to the perception of pain to cell survival. Disruption of normal prostanoid signaling is implicated in numerous disease states. Prostaglandin signaling is facilitated by G-protein-coupled, prostanoid-specific receptors and the array of associated G-proteins. This review focuses on the expression, characterization, regulation, and mechanism of action of prostanoid receptors with particular emphasis on human isoforms.

Headaches related to latanoprost in open-angle glaucoma

Clinical relevance: The existing notion that topical latanoprost can lead to symptoms of headaches by reporting three cases of headache symptoms that developed following instillation of latanoprost prescribed as first-line therapy for newly diagnosed primary open-angle glaucoma (POAG) is explored in this case series.Background: Prostaglandin analogues (PGAs) are often used as first-line treatment in the treatment of POAG. An uncommon and infrequently reported side effect of PGAs is headaches.Methods: A retrospective review of patient records was conducted on patients seen at the Centre for Eye Health between April 2016 and August 2017. Clinical findings, including outcomes following interventions such a punctal occlusion, as well as the proposed pharmacological mechanism underlying this phenomenon are presented and discussed.Results: Case 1 is a 62-year-old Caucasian male diagnosed with POAG and prescribed latanoprost in both eyes. At the follow-up visit, he reported waking up in with a dull throbbing headache following instillation of the eye drops the night before. Case 2 is a 58-year-old Asian male with POAG prescribed latanoprost to both eyes. Within a week, he developed symptoms of recurrent progressively worsening headaches post-instillation which persisted into the morning. Case 3 is a 75-year-old Caucasian male with POAG prescribed latanoprost for both eyes. He developed latanoprost sensitivity as well as headache symptoms associated with the eye drops which resolved followed its cessation. All patients reported initial symptoms of headaches associated with latanoprost use however the headaches were not persistent with intermittent punctal occlusion (cases 1 and 2) or intra-class drug rechallenge (case 3).Conclusion: Although there may be a yet-undiscovered link between a headache response and latanoprost, these cases call to question the pharmacological relationship between latanoprost and headache symptoms. A systemic approach to critically examine the pathophysiological link between pharmacological therapy and potential adverse effects is proposed.

Latanoprost-loaded cyclodextrin microaggregate suspension eye drops for enhanced bioavailability and stability

OBJECTIVE

The bioavailability of conventional eye drops is very low due to different physiological barriers. Commercial latanoprost (LAT) eye drops (Xalatan®) need to be refrigerated and protected from light. The purpose of this study was to develop novel LAT eye drops to improve ocular bioavailability and stability.

METHODS

Ophthalmic suspension containing LAT/γ-cyclodextrin (γCD) aggregates was designed and the preparation process was sufficiently studied. The prepared formulations were evaluated for pH, viscosity, osmolality, particle size, entrapment efficiency and in vitro release study. In vitro permeability study using Human Corneal Epithelial Cells and in vivo studies on rabbits were also performed.

RESULTS

LAT/γCD aggregates were formed and confirmed by scanning electron microscopy. LAT/γCD eye drops showed obvious sustained release profiles and were more stable than Xalatan®. In vitro corneal permeation study indicated LAT/γCD eye drops had no significant cytotoxicity and had higher cell permeability. In vivo precorneal retention study showed AUC_0-6 h, C_max, and mean residence time (MRT) of LAT/γCD eye drops were 3.98, 2.12, and 2.07 times higher than those of Xalatan®, respectively. In vivo ocular distribution study revealed that AUC_0-24 h, C_max, and MRT for latanoprost acid in aqueous humor exhibited 2.60-fold, 1.36-fold, and 1.99-fold increase in LAT/γCD eye drops group than those of Xalatan® group, respectively.

CONCLUSION

Cyclodextrin microaggregate suspension eye drops represent a potential strategy for enhanced bioavailability and stability of LAT.

Discovery to Launch of Anti-allergy (Emadine; Patanol/Pataday/Pazeo) and Anti-glaucoma (Travatan; Simbrinza) Ocular Drugs, and Generation of Novel Pharmacological Tools Such as AL-8810

The eye and eyesight are exquistly designed and are precious, and yet we often take them for granted. Good vision is critical for our long-term survival and for humanity's enduring progress. Unfortunately, since ocular diseases do not culminate in life-and-death scenarios, awareness of the plight of millions of people suffering from such eye ailments is not publicized as other diseases. However, losing eyesight or falling victim to visual impairment is a frightening outlook for most people. Glaucoma, a collection of chronic optic neuropathies, of which the most prevalent form, primary open-angle glaucoma (POAG), is the second leading cause of irreversible blindness. POAG currently afflicts >70 million people worldwide and is an insidious, progressive, silent thief of sight that is asymptomatic. On the other hand, allergic conjunctivitis (AC), and the associated rhinitis ("hay-fever"), frequently victimizes a huge number of people worldwide, especially during seasonal changes. While not life-threatening, sufferers of AC soon learn the value of drugs to treat their signs and symptoms of AC as they desire rapid relief to overcome the ocular itching/pain, redness, and tearing AC causes. Herein, I will describe the collective efforts of many researchers whose industrious, diligent, and dedicated team work resulted in the discovery, biochemical/pharmacological characterization, development and eventual launch of drugs to treat AC (e.g., olopatadine [Patanol/Pataday/Pazeo] and emedastine [Emedine]), and for treating ocular hypertension and POAG (e.g., travoprost [Travatan ] and Simbrinza). This represents a personal perspective.

Effect of prostaglandin analogs: Latanoprost, bimatoprost, and unoprostone on matrix metalloproteinases and their inhibitors in human trabecular meshwork endothelial cells

Bimatoprost, latanoprost, and unoprostone are prostaglandin F_2α analogs (PGAs) and are used to lower intraocular pressure. We investigated the free acid effects of these three prostaglandin analogs: bimatoprost, latanoprost, and unoprostone on human matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMP) in the trabecular meshwork (TM) cells. Immunoblot results show that all three PGAs generally increased MMPs-1,9 and TIMPs-4. Additionally, bimatoprost and latanoprost both increased MMP-3 and TIMP-2, while unoprostone had an indeterminate effect on both. Zymography results show that all three PGAs except unoprostone increased intermediate MMP-1 activity while bimatoprost and latanoprost increased MMP-9 activity. Together, these data suggest that the balance between MMPs and TIMPs correlate to the relative intraocular pressure lowering effectiveness observed in clinical studies of these PGAs.

Nonclinical Pharmacokinetic and Pharmacodynamic Assessment of Bimatoprost Following a Single Intracameral Injection of Sustained-Release Implants

Purpose

To assess the pharmacokinetic (PK)/pharmacodynamic (PD) relationship following intracameral Bimatoprost sustained-release (SR) implants (8, 15, 30, and 60 µg) in dogs to determine the optimal investigative dose in humans.

Methods

Forty-four male normotensive beagle dogs were assigned to 1 of 8 groups receiving 8-, 15-, 30-, and 60-µg implants (PD assessment [n = 8/group, 4 groups]; PK assessment [n = 3/group, 4 groups]). Intraocular pressure (IOP) in PD animals and aqueous humor/blood concentrations of bimatoprost and its acid in PK animals were assessed. PK/PD correlation analysis was performed using steady-state data. Residual implants were recovered to assess polymer degradation.

Results

Dose-dependent IOP lowering was observed for all dose groups for at least 3 months postdose. Blood concentrations of bimatoprost and bimatoprost acid were below the limit of quantification (<0.25 ng/mL), whereas dose-dependent concentration-time profiles were observed in the aqueous humor. At steady state, observed and predicted correlation between aqueous humor drug concentration and IOP lowering was similar and translatable to findings in humans following topical bimatoprost eyedrop administration. Implants at all doses were well tolerated and polymer degradation was apparent.

Conclusions

Dose-dependent IOP lowering with Bimatoprost SR was maintained for at least 3 months in dogs, and the implants were well tolerated. The established PK/PD relationship appears to translate to humans. Doses between 8 and 15 µg appear to provide the best benefit/risk profile for clinical development of the implants.

Translational Relevance

The close PK/PD relationship between dog and human helps inform which bimatoprost dose should be investigated in clinical studies.

Netarsudil and latanoprost ophthalmic solution for the reduction of intraocular pressure in open-angle glaucoma or ocular hypertension

Introduction: Netarsudil and latanoprost ophthalmic solution (0.02%/0.005%) is indicated for intraocular pressure (IOP) lowering in open-angle glaucoma (OAG) or ocular hypertension (OHTN). The once-daily agent combines the mechanism of action for each of the individual components and provides a new avenue for long-term intraocular pressure control. This review aims to cover the agent's current efficacy and safety data and opine as to its role in glaucoma management.Areas covered: This article will cover Phase II-III clinical efficacy and safety data as well as basic science literature pertaining to the agent's mechanism of action and pharmacodynamics. In selecting articles for inclusion in this review, a literature search using the PubMed database was carried out. Cross-referencing was carried out where applicable. We did not use any date or language restrictions in electronic searches.Expert opinion: Netarsudil and latanoprost ophthalmic solution plays a pivotal role in management of individuals with OAG and OHTN. The agent may be used as first-line therapy to provide substantial IOP-lowering or when additional lowering is indicated and prostaglandins have provided insufficient IOP lowering. The once-daily dosing regimen decreases the risk of inadequate treatment due to nonadherence.

Intraocular pressure reduction with once-a-day application of a new prostaglandin eye drop: a pilot placebo-controlled study in 12 patients

PURPOSE

To assess the ocular hypotensive effect of 15-keto fluprostenol, the oxidized metabolite of travoprost, on glaucoma patients, through a randomized double-masked placebo-controlled study.

METHODS

Twelve patients with ocular normal tension glaucoma (NTG) (intraocular pressure [IOP] < 22 mmHg) were enrolled. In order to ensure patient compliance to treatment, all study subjects were hospitalized. In each patient, the eye to be submitted to the treatments was randomly chosen. After hospital admission (day 1), those patients received for 5 days at 8 P.M. either one drop of 15-keto fluprostenol (35 μg/ml) or one drop of placebo. IOP evaluation was performed within 8 A.M. and 8 P.M. for 6 days. Furthermore, we performed a determination of cardiovascular parameters before and after the treatments.

RESULTS

Starting with the first IOP measurement after the first treatment (8 A.M. on day 2), IOP was reduced of about 14% in the eyes treated 15-keto fluprostenol, in comparison with baseline IOP values of 15-keto fluprostenol-treated patients. The IOP reduction in the 15-keto fluprostenol-treated group was significantly compared to placebo group (p < 0.05) starting from day 3 till day 6 of the study. Except for mild hyperemia in one 15-keto fluprostenol-treated eye, no other side effects were observed or reported by the enrolled patients.

CONCLUSIONS

The travoprost metabolite 15-keto fluprostenol was effective in decrease IOP and maintained IOP reduction along 5 days of treatment. The 15-keto fluprostenol can be developed as a good candidate for once-a-day NTG patients' treatment.

Efficacy and safety of prostaglandin analogues in primary open-angle glaucoma or ocular hypertension patients: A meta-analysis

BACKGROUND

To evaluated and compared the efficacy and safety of 3 prostaglandin analogues (0.005% latanoprost, 0.004% travoprost, and 0.03% bimatoprost) in treatment of primary open-angle glaucoma (POAG) or ocular hypertension (OHT).

METHODS

PubMed, Embase, Cochrane library, Web of science, CNKI, Wanfang, and Vip database, published between January 1, 2000 and June 1, 2018, were systematically examined for randomized controlled trials (RCT) based on prostaglandin analogues for POAG or OHT treatment. Statistical analyses including weighted mean difference (WMD) calculation and odds ratio (OR) were performed using Review Manager Software version 5.3.

RESULT

The 17 studies were included in this analysis (N = 2433 participants) with 1∼12 months' follow-ups. The difference of intraocular pressure (IOP) reduction between latanoprost and travoprost group had not significant; there was significant difference of IOP reduction between latanoprost and bimatoprost group in the third month and sixth month; Travoprost was significantly different from bimatoprost in reducing IOP in the third month. Travoprost revealed an elevated risk of conjunctival hyperemia compared with latanoprost. An elevated risk of conjunctival hyperemia and growth of lashes compared with latanoprost. Bimatoprost shows lower ocular tolerability with higher incidence of side effects such as conjunctival hyperemia.

CONCLUSIONS

0.03% bimatoprost appears more effective following long time use (3 and 6 month post-treatment) for IOP control compared to 0.005% latanoprost, and is more effective compared to 0.004% travoprost after being used for a certain period of time (3 months post-treatment); nevertheless, 0.005% latanoprost is better tolerated in patients with POAG or OHT.

Contribution of prostanoid FP receptor and prostaglandins in transient inflammatory ocular hypertension

We explored the involvement of FP receptor and endogenous prostaglandins (PGs) in transient ocular hypertension (OH) induced by PGE2 or PGF2α in mouse eyes. PGE2 and PGF2α were topically applied to induce transient OH in Wild-type (WT) and FP-, EP1-, EP2-, and EP3-deficient (knockout [KO]) mice. To suppress endogenous PG production, the non-steroidal anti-inflammatory drug nepafenac was applied topically before treatment. PGE2 and PGF2α induced significant OH in the WT, FPKO, and EP1–3KO mice compared to the control 30 min after instillation, and the increase in IOP at 30 or 60 min after instillation in FPKO mice was significantly higher than that in the WT mice. The effects of PGF2α on the increase in IOP were significantly weaker than those of PGE2, especially in EP1KO and EP3KO mice. Transient OH induced by PGE2 and PGF2α was significantly attenuated by nepafenac treatment in FPKO mice. Transient OH was induced by PGE2 and PGF2α in WT, FPKO, and EP1–3KO mice, which was enhanced in FPKO mice. This OH was significantly diminished by nepafenac treatment in FPKO mice, suggesting that FP receptor may have an important naïve physiological role in the eye, and could regulate IOP elevation during PG-associated ocular inflammation.

Prostaglandin FP receptor antagonists: discovery, pharmacological characterization and therapeutic utility

In contrast to the availability of potent and selective antagonists of several prostaglandin receptor types (including DP₁ , DP₂ , EP and TP receptors), there has been a paucity of well-characterized, selective FP receptor antagonists. The earliest ones included dimethyl amide and dimethyl amine derivatives of PGF_2α , but these have failed to gain prominence. The fluorinated PGF_2α analogues, AL-8810 and AL-3138, were subsequently discovered as competitive and non-competitive FP receptor antagonists respectively. Non-prostanoid structures, such as the thiazolidinone AS604872, the D-amino acid-based oligopeptide PDC31 and its peptidomimic analogue PDC113.824 came next, but the latter two are allosteric inhibitors of FP receptor signalling. AL-8810 has a sub-micromolar in vitro potency and ≥2 log unit selectivity against most other PG receptors when tested in several cell- and tissue-based functional assays. Additionally, AL-8810 has demonstrated therapeutic efficacy as an FP receptor antagonist in animal models of stroke, traumatic brain injury, multiple sclerosis, allodynia and endometriosis. Consequently, it appears that AL-8810 has become the FP receptor antagonist of choice. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Discovery, characterization and clinical utility of prostaglandin agonists for the treatment of glaucoma

Topical ophthalmic formulations of analogues of the endogenous arachidonic acid cyclooxygenase metabolite, PGF_2α , are the standard of care treatment for the blinding disease glaucoma. These are the most potent and efficacious medical therapies for lowering intraocular pressure (IOP), the most important risk factor identified for disease progression. They have few side effects and offer the convenience of once-a-day dosing. It was initially believed that endogenous PGs raised IOP and caused substantial ocular surface adverse effects. However, carefully designed experiments demonstrated that esterification of the carboxylic acid afforded potent and efficacious topical ocular hypotensive activity. The final hurdle to be overcome was improvement of the side effect profile. A hypothesis was advanced that the IOP-lowering effect of PGF_2α isopropyl ester was due to activation of its cognate PG-FP receptor, while side effects were largely due to promiscuous interaction with other PG receptors. This hypothesis was validated by modification of the ω chain (carbons 13-20) to a phenyl group. This provided the first marketed FP-class PG agonist analogue (FP-PGA) ocular hypotensive agent, latanoprost. Since the introduction of latanoprost into clinical medicine to lower and control IOP, a number of additional FP-PGAs have been discovered, characterized and marketed, including travoprost, tafluprost, unoprostone isopropyl ester and bimatoprost (an amide). LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

The neuroprotective effect of latanoprost acts via klotho-mediated suppression of calpain activation after optic nerve transection

Latanoprost was first developed for use in glaucoma therapy as an ocular hypotensive agent targeting the prostaglandin F2α (FP) receptor. Subsequently, latanoprost showed a neuroprotective effect, an additional pharmacological action. However, although it is well-known that latanoprost exerts an ocular hypotensive effect via the FP receptor, it is not known whether this is also true of its neuroprotective effect. Klotho was firstly identified as the gene linked to the suppression of aging phenotype: the defect of klotho gene in mice results aging phenotype such as hypokinesis, arteriosclerosis, and short lifespan. After that, the function of klotho was also reported to maintain calcium homeostasis and to exert a neuroprotective effect in various models of neurodegenerative disease. However, the function of klotho in eyes including retina is still poorly understood. Here, we show that klotho is a key factor underlying the neuroprotective effect of latanoprost during post-axotomy retinal ganglion cell (RGC) degeneration. Importantly, a quantitative RT-PCR gene expression analysis of klotho in sorted rat retinal cells revealed that the highest expression level of klotho in the retina was in the RGCs. Latanoprost acid, the biologically active form of latanoprost, inhibits post-traumatic calpain activation and concomitantly facilitates the expression and shedding of klotho in axotomized RGCs. This expression profile is a good match with the localization, not of the FP receptor, but of organic anion transporting polypeptide 2B1, known as a prostaglandin transporter, in the ocular tissue. Furthermore, an organic anion transporting polypeptide 2B1 inhibitor suppressed latanoprost acid-mediated klotho shedding ex vivo, whereas an FP receptor antagonist did not. The klotho fragments shed from the RGCs reduced the intracellular level of reactive oxygen species, and a specific klotho inhibitor accelerated and increased RGC death after axotomy. We conclude that the shed klotho fragments might contribute to the attenuation of axonal injury-induced calpain activation and oxidative stress, thereby protecting RGCs from post-traumatic neuronal degeneration.

Effect of Travoprost and Nonsteroidal Anti-Inflammatory Drug on Diurnal Intraocular Pressure in Normal Subjects with Low-Teen Baseline Intraocular Pressure

PURPOSE

The main purpose was to determine whether a nonsteroidal anti-inflammatory drug (NSAID) ophthalmic solution would affect the intraocular pressure (IOP)-lowering effect of a benzalkonium chloride (BAK)-free prostaglandin analog, travoprost. The secondary purpose was to confirm the IOP-lowering effect of BAK-free travoprost on the diurnal IOP.

METHODS

This was a prospective, randomized, double-blind, placebo-controlled 1-month trial. After baseline diurnal IOP was confirmed, travoprost was administered once daily to both eyes. Bromfenac sodium hydrate was then randomly assigned to one eye, while flavin adenine dinucleotide sodium was applied to the other eye as a control. Both solutions were administered twice daily. IOP was measured three times daily (8:00, 14:00, and 20:00). The IOP of both groups was compared using Student's t-test. The effect of NSAID on IOP was investigated by repeated measures analysis of variance (ANOVA).

RESULTS

Twenty-eight normal Japanese subjects (mean age, 36.6 years) completed the study. After the start of travoprost, remarkable IOP lowering was gained and it settled to 10-11 mmHg. The diurnal IOPs of the NSAID group showed similar tendencies to that of the control group (P = 0.69-1.0). In a 1-month period, the range of IOP reductions compared with the baseline IOP of both groups showed no significant difference (P = 0.76-0.92). NSAID did not have an influence on IOP (F-value = 0.0036, P = 0.95).

CONCLUSIONS

Although BAK-free travoprost showed a powerful IOP-lowering effect in diurnal and 1-month readings, even in eyes with an IOP of <13 mmHg, the NSAID ophthalmic solution did not affect its IOP-lowering effect.

Ocular Tolerability of Preservative-Free Tafluprost and Latanoprost: in vitro and in vivo Comparative Study

Objective:

Detrimental effects of the preserved prostaglandin analogs (PGAs) have been thoroughly documented in the published literature. The current work studied two preservative-free (PF) prostaglandin eye drops: PF tafluprost and PF latanoprost. The aim of the study was to compare these two PF formulations in vitro for viability of the human corneal epithelial (HCE-T) cells and in vivo for ocular tolerability of the rabbit eye.

Method:

Viability of the HCE-T cells was measured by the MTS assay. The SV40-immortalized HCE-T cells were exposed to 100 µL of the drug solutions (at their commercial concentrations) or the culture medium. Ocular irritation was evaluated after repeated instillation of the drug solutions in Japanese white rabbits (Kbl:JW).

Results:

A significant loss of HCE-T cell viability was observed in vitro immediately after the exposure to PF latanoprost formulation but not immediately after the exposure to PF tafluprost formulation. Congruently, PF latanoprost induced in vivo more irritation on the rabbit eye than PF tafluprost.

Conclusion:

Comparing these two PF formulations in vitro and in vivo, it is considered that ocular tolerability of PF tafluprost is better than PF latanoprost. Taking into account the composition of these two PF PGA formulations, the solubilizing agent macrogolglycerol hydroxystearate 40 (MGHS40) contained in PF latanoprost formulation is a plausible cause for the negative effects.

Evaluation of Efficacy and Safety of Latanoprost/Timolol versus Travoprost/Timolol Fixed Combinations for Ocular Hypertension Associated with Uveitis

PURPOSE

To compare latanoprost/timolol (LT) versus travoprost/timolol (TT) fixed combinations for ocular hypertension (OHT) associated with uveitis.

METHODS

Thirty-six patients (55 eyes) who were treated with LT (28 eyes) or TT (27 eyes) for OHT associated with uveitis were reviewed retrospectively. Intraocular pressure (IOP) and inflammation scores at the initiation of treatment and at the last visit during therapy were analyzed.

RESULTS

Although IOP was reduced significantly in both LT and TT groups, the reduction rate was significantly greater with TT group than with LT. The differences in the reduction of IOP between the groups remained significant when the cases were classified into inflammation-induced OHT and steroid-induced OHT. Inflammation score was not exacerbated by LT or TT treatment.

CONCLUSIONS

Both LT and TT are safe and effective for the treatment of OHT associated with uveitis and greater IOP reduction may be achieved by TT than by LT treatment.

Unoprostone activation of BK (KCa1.1) channel splice variants

This investigation was conducted to study the relationship between intracellular Ca(2+) and activation of large conductance Ca(2+)-activated K(+) (BK) currents by unoprostone, the first synthetic docosanoid. We used HEK293 cells stably transfected with two BK channel splice variants, one sensitive to unoprostone and the other insensitive. We examined the effects of unoprostone on channel activity in excised inside-out patches and cell-attached patches. The half-maximal stimulation of the sensitive BK channels by Ca(2+) was shifted from 3.4±0.017 nM to 0.81±.0058 nM in the presence of 10 nM unoprostone. There was no effect on insensitive channels even at unoprostone concentrations as high as 1000 nM. There was no effect of unoprostone on the voltage dependence of the BK channels. Changes in open probability and effects of Ca(2+) and unoprostone were best described by a synergistic binding model. These data would suggest that Ca(2+) and unoprostone were binding to sites close to one another on the channel protein and that unoprostone binding causes the affinity of the calcium binding site to increase. This idea is consistent with three dimensional models of the Ca(2+) binding site and a putative unoprostone binding domain. Our results have important implications for the clinical use of unoprostone to activate BK channels. Channel activation will be limited if intracellular Ca(2+) is not elevated.

Effect of topical anti-glaucoma medications on late pupillary light reflex, as evaluated by pupillometry

Purpose

The late post-illumination pupillary response (PIPR_10–30s) to blue light is reduced in glaucoma, suggesting that pupillometry can be used in clinical glaucoma evaluation. Since animal studies have indicated that common anti-glaucomatous agents affect the iris muscle, we investigated the short-term effect of the anti-glaucoma drugs on the pupillary light reflex and in particular on the PIPR_10–30s.

Methods

In this randomized, double-masked, crossover trial, pupillometry was performed before and after topical administration of latanoprost, dorzolamide, and timolol in 20 healthy subjects. Stimulus was blue (463 nm) and red light (633 nm) of 2 log (lux). Main outcome was the PIPR_10–30s to blue light. Additionally, pupil size, maximal contraction, and the early post-illumination pupillary response (PIPR_0–10s) to blue and red light were investigated. Pupil response variations between 8 a.m. and 2 p.m. were also assessed. Intraocular pressure (IOP) was measured before and 3.5 h after drug instillation.

Results

We found no drug effect on the blue light PIPR_10–30s or any other blue light pupil parameters. During the control day, the only significant variation over time was observed for the red light PIPR_0–10s (p = 0.02). Pupillary size decreased slightly with timolol (0.1 mm, p = 0.03) and dorzolamide (0.2 mm, p < 0.001), but not with latanoprost. Timolol also reduced the maximal contraction amplitude significantly during red light (p = 0.02). Intraocular pressure was significantly reduced by all three drugs after 3.5 h (p < 0.01), while it remained unchanged during the control day (p = 0.3).

Conclusion

Anti-glaucoma medications did not interfere with the blue light elicited PIPR. Dorzolamide reduced pupil size, while timolol reduced both pupil size and maximal contraction to red light, but the effect was minute and not of clinical importance.

The circadian changes of intraocular pressure and ocular perfusion pressure after tafluprost compared with travoprost in normal tension glaucoma

PURPOSE

To compare the 24-h changes of intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP) obtained with tafluprost versus travoprost in patients with normal-tension glaucoma (NTG).

METHODS

This study is a randomized crossover study of 50 patients newly diagnosed with NTG who received either tafluprost or travoprost given once at 9 PM for 2 months, after which they were crossed over to the other medication for another 2 months. IOP and blood pressure were measured for 24 h before starting the treatment and after finishing the first and second treatment periods.

RESULTS

Forty-one patients completed the study. The mean (±standard deviation) 24-h IOP was 16.8±2.0 mmHg at baseline, 14.4±2.2 mmHg on tafluprost, and 13.6±1.8 mmHg on travoprost. Both prostaglandin monotherapies significantly reduced mean 24-h IOP as compared with baseline (P<0.001, P<0.001, respectively), and travoprost demonstrated a lower mean 24-h IOP than tafluprost (P=0.044). Both treatments significantly reduced the IOP from baseline at every point over 24 h. At 3 individual time points, travoprost provided a lower IOP than tafluprost: at 4 PM (13.8±2.7 vs. 14.8±2.6 mmHg, P=0.041), at 6 PM (13.5±2.5 vs. 14.4±2.5 mmHg, P=0.006), and at 8 PM (13.3±2.5 vs. 14.5±2.4 mmHg, P=0.029). Both tafluprost and travoprost significantly increased the 24-h MOPP (P=0.008, P=0.002, respectively), and travoprost demonstrated a greater 24-h MOPP than tafluprost (P=0.027).

CONCLUSIONS

Both tafluprost and travoprost were effective in lowering IOP and increasing MOPP throughout 24 h in NTG. However, travoprost reduced IOP greater than tafluprost in the late afternoon and evening.

Fixed-dose combination of tafluprost and timolol in the treatment of open-angle glaucoma and ocular hypertension: comparison with other fixed-combination products

A new preservative-free fixed-dose combination of 0.0015% tafluprost, a prostaglandin F_2α analog, and 0.5% timolol (TAF/TIM; Santen Oy, Tampere, Finland), a beta-adrenergic antagonist has recently been developed. The intraocular pressure (IOP) reduction with TAF/TIM in open-angle glaucoma and ocular hypertension is similar to that of other prostaglandin–timolol fixed-combination products. Patients with high IOP responded well to TAF/TIM with reductions of up to 40% (>13 mmHg) and beyond. Compared to previous controlled and double-masked clinical trials with DuoTrav^® (Alcon, Fort Worth, USA) and Ganfort^® (Allergan, Irvine, USA), TAF/TIM caused less superficial ocular side effects and less conjunctival hyperemia. Plausible explanations for the differences in side effects between the fixed-combination products are discussed.

Topical prostaglandin analogue drugs inhibit adipocyte differentiation

Purpose

To investigate the effects of topical prostaglandin analogue drugs on the differentiation of adipocytes.

Methods

Differentiation of 3T3-L1 preadipocytes was induced with isobutylmethylxanthine, dexamethasone, and insulin. 3T3-L1 cells were exposed to 0.008, 0.08, 0.2 µM of latanoprost and travoprost. Reverse transcription polymerase chain reaction for mRNA expression of lipoprotein lipase and peroxisome proliferator-activated receptor γ 2 (PPARγ2), and glycerol-3-phosphate dehydrogenase (G3PDH) assays were performed to examine the effects on early and late differentiation, respectively. Also, glycerol assays were done to evaluate the effect of prostaglandin analogues on lipolysis after differentiation.

Results

Both prostaglandin analogues inhibited differentiation of preadipocytes. Topical prostaglandin analogues significantly decreased G3PDH activity, a marker of late differentiation. However, topical prostaglandin analogues did not change mRNA expressions of lipoprotein lipase and PPARγ2, markers of early differentiation. The activities of the early markers of differentiation were not changed significantly before and after growth arrest. Compared to latanoprost, travoprost decreased G3PDH activity more significantly (p < 0.05). Both prostaglandin analogues did not affect the lipolysis of differentiated adipocytes (p > 0.05).

Conclusions

Prostaglandin analogues display an inhibitory effect on the differentiation of adipocytes when the cells start to differentiate especially in the late stage of differentiation. Thus, commercial topical prostaglandin analogues may decrease the fat contents of eyelids.

FR-190997, a nonpeptide bradykinin B2-receptor partial agonist, is a potent and efficacious intraocular pressure lowering agent in ocular hypertensive cynomolgus monkeys

Preclinical Research FR-190997 (8-[2,6-dichloro-3-[N-[(E)-4-(N-methylcarbamoyl) cinnaminoacetyl]-N-methylamino]benzyloxy]-2-methyl-4- (2-pyridylmethoxy) quinoline), a nonpeptide bradykinin (BK) B2-receptor-selective agonist, represents a novel class of ocular hypotensive agents. FR-190997 exhibited a high affinity for the human cloned B2-receptor (Ki = 9.8 nM) and a relatively high potency (EC50 = 155 nM) for mobilizing intracellular Ca(2+) ([Ca(2+)]i) in human ocular cells from nonpigmented ciliary epithelium; trabecular meshwork [h-TM]; ciliary muscle [h-CM] that are involved in regulating intraocular pressure (IOP). Unlike BK, FR-190997 behaved as a partial agonist (Emax = 38-80%) in these cells and its [Ca(2+)]i-mobilizing effects were blocked by the B2-receptor-selective antagonists (HOE-140, Ki = 0.8-7 nM; WIN-64338, Ki = 157-425 nM). FR-190997 stimulated the production of prostaglandins (PGs) in h-CM and h-TM cells (EC50 = 15-19 nM; Emax = 27-33%); an effect that was reduced by the cyclooxygenase-2 inhibitor bromfenac, and by HOE-140. FR-190997 also induced pro-matrix metalloproteinase (MMP)-1 and MMP-3 release from h-CM cells. FR-190997 significantly lowered IOP (37% [P < 0.001] with 30 μg, 24 h post-topical ocular dosing) in ocular hypertensive eyes of conscious Cynomolgus monkeys. This effect was reduced by bromfenac and completely blocked by a B2-antagonist. FR-190997 primarily stimulated uveoslceral outflow (UVSO) of aqueous humor (2.6 to 3.9-fold above baseline). In conclusion, FR-190997 is a B2-receptor selective partial agonist that activates phospholipase C, mobilizes [Ca(2+)]; induces PG and pro-MMP production, and that profoundly lowers IOP by promoting UVSO in ocular hypertensive Cynomolgus monkey eyes.

The prostaglandin f2α analog fluprostenol attenuates the fibrotic effects of connective tissue growth factor on human trabecular meshwork cells

Abstract Purpose: The trabecular meshwork (TM) outflow pathways of the aqueous humor show an increase in extracellular matrix in patients with primary open-angle glaucoma (POAG). The increase in TM extracellular matrix appears to be caused by transforming growth factor-β signaling and its downstream mediator connective-tissue growth factor (CTGF). Here we studied whether treatment with the prostaglandin F2α analog fluprostenol modulates the CTGF-mediated increase of the TM extracellular matrix.

METHODS

Human TM cells from 3 different donors were treated with CTGF (50 ng/mL) and/or fluprostenol (10(-6) M and 10(-7) M) and were analyzed by real-time reverse transcription polymerase chain reaction and Western blotting. Cell supernatants of the treated cells were analyzed by zymography.

RESULTS

Treatment with CTGF induced the expression and synthesis of CTGF, fibronectin, collagen type IV and VI, while treatment with fluprostenol alone had no effects. The effects of CTGF were blocked by 1-h pretreatment with fluprostenol in a dose-dependent manner. Treatment with fluprostenol or combined fluprostenol/CTGF induced the activity of matrix metalloproteinase 2 (MMP2) in TM cells, whereas treatment with CTGF alone had no effects on MMP2 activity.

CONCLUSIONS

Fluprostenol blocks the fibrotic effects of CTGF on human TM cells and increases the activity of MMP2. Both effects have the distinct potential to attenuate a CTGF-mediated increase in TM extracellular matrix in patients with POAG and any effects on TM outflow resistance that may result from that.

Diurnal intraocular pressure with bimatoprost/timolol fixed combination versus latanoprost/timolol fixed combination in healthy subjects

PURPOSE

To evaluate the effects of a bimatoprost/timolol fixed combination (BTFC) and a latanoprost/timolol fixed combination (LTFC) on diurnal intraocular pressure (IOP) and anterior ocular parameters in healthy subjects.

METHODS

We enrolled 58 healthy subjects in this prospective clinical study. Thirty subjects were treated with BTFC and 28 subjects were treated with LTFC. IOP was measured every 2 hours except from 01:00 and 05:00. Axial length, corneal curvature, and anterior chamber depth were obtained using the IOL master at baseline and 24 hours later. Adverse events were assessed by patient interview and by slit lamp examination.

RESULTS

The largest difference in IOP between treated and untreated eyes 8 hours after instillation was 1.67 mmHg in the BTFC group (p < 0.001). The largest difference in IOP between treated and untreated eyes 10 hours after instillation was 1.93 mmHg in the LTFC group (p < 0.001). For anterior ocular parameters such as axial length, corneal curvature, anterior chamber depth at baseline and 24 hours after instillation, there were no significant differences between the baseline and 24-hour values in either the BTFC or LTFC group. The most frequently occurring adverse event was conjunctival hyperemia, which was found in 33.3% (n = 10) of the BTFC group and 25.0% (n = 7) of the LTFC group (p = 0.486).

CONCLUSIONS

BTFC and LTFC provided a significant reduction in IOP from baseline without changing any anterior ocular parameters. Our results provide a reference for monocular trials to assess the effect of eye drops in a clinical condition.

Effects of prostaglandin analogues on aqueous humor outflow pathways

Elevated intraocular pressure (IOP) is the most prevalent risk factor for glaucoma. All treatments, whether surgical or pharmaceutical, are aimed at lowering IOP. Prostaglandin analogues are a first line therapy for glaucoma due to their ability to reduce IOP, once-daily dosing, efficacy, and minimal side-effect profile. Whereas prostaglandin analogues have been known to alter aqueous humor outflow through the unconventional (uveoscleral) pathway, more recent evidence suggests their action also occurs through the conventional (trabecular) pathway. Understanding how prostaglandin analogues successfully lower IOP is important, as this information may lead to the discovery of new molecular targets for future therapeutic intervention. This review explores the current understanding of prostaglandin analogue biology as it pertains to IOP reduction and improved aqueous humor outflow facility.

In vitro effects of preservative-free and preserved prostaglandin analogs on primary cultured human conjunctival fibroblast cells

PURPOSE

Long-term use of topical medication is needed for glaucoma treatment. One of the most commonly prescribed classes of hypotensive agents are prostaglandin analogs (PGs) used as both first-line monotherapy; as well as in combination therapy with other hypotensive agents. Several side effects of eye drops can be caused by preservatives. The purpose of this study was to evaluate the effects of PGs with varying concentrations of benzalkonium chloride (BAC), alternative preservatives, or no preservatives on human conjunctival fibroblast cells.

METHODS

Primary human conjunctival fibroblast cells were used in these experiments. Cells were exposed to the following drugs: BAC at different concentrations, bimatoprost 0.01% (with BAC 0.02%), latanoprost 0.005% (with BAC 0.02%), tafluprost 0.0015% with/without 0.001% BAC and travoprost 0.004% (with 0.001% Polyquad) for 15 and 30 minutes. Cell cytotoxicity was evaluated by phase-contrast microscopy to monitor morphological changes of cells, Counting Kit-8 (CCK-8) assay to cell viability, and fluorescent activated cell sorting (FACS) analysis to measure apoptosis.

RESULTS

BAC caused cell shrinkage and detachment from the plate in a dose-dependent manner. Morphological changes were observed in cells treated with bimatoprost 0.01% and latanoprost 0.005%. However, mild cell shrinkage was noted in cells treated with tafluprost 0.0015%, while a non-toxic effect was noted with travoprost 0.004% and preservative-free tafluprost 0.0015%. CCK-8 assay and FACS analysis showed all groups had a significantly decreased cell viability and higher apoptosis rate compared with the control group. However, travoprost 0.004% and preservative-free tafluprost 0.0015% showed lower cytotoxicity and apoptosis rate than other drugs.

CONCLUSIONS

This in vitro study revealed that BAC-induced cytotoxicity is dose-dependent, although it is important to emphasize that the clinical significance of toxicity differences observed among the different PGs formulations has not yet been firmly established. Alternatively preserved or preservative-free glaucoma medications seem to be a reasonable and viable alternative to those preserved with BAC.

Regeneration of optic nerve fibers with unoprostone, a prostaglandin-related antiglaucoma drug, in adult cats

PURPOSE

We investigated the effects of unoprostone on neurite extension of cultured retinal pieces and axonal regeneration of retinal ganglion cells in the crushed optic nerve of adult cats.

METHODS

The retinal pieces were cultured with unoprostone or its primary metabolite, M1, dissolved in DMSO or polysorbate for 14 days, and the number and length of Tau-1-positive neurites and glial processes labeled with anti-glial fibrillary acidic protein antibodies were examined. After the optic nerve was crushed, unoprostone was injected into the vitreous body and the crushed site. On day 12, wheat germ agglutinin-conjugated horseradish peroxidase was injected into the vitreous body to anterogradely label the regenerated axons. On day 14, the optic nerve was excised and longitudinally sectioned. After peroxidase reaction, the number of axons regenerating beyond the crush site was examined.

RESULTS

The greatest number of neurites protruded from the cultured retinal pieces in 3 μM unoprostone and 3 μM M1. The neurite length was also the longest at 3 μM unoprostone and 3 μM M1, in which no glial processes were detected. After injections of 3 μM unoprostone, the final concentration in the vitreous humor, into the vitreous body and the crush site, the optic nerve fibers regenerated and extended beyond the crush site. In contrast, almost no fibers extended beyond the crush site after injection of phosphate-buffered saline.

CONCLUSIONS

The results indicate that intravitreal injection of unoprostone promotes regeneration of crushed optic nerve fibers in adult cats.

Incidence of deepening of upper eyelid sulcus after topical use of tafluprost ophthalmic solution in Japanese patients

PURPOSE

To investigate the incidence of deepening of upper eyelid sulcus (DUES) with topical use of tafluprost in Japanese glaucoma patients.

METHODS

This study was a prospective, open-label, non-controlled case series conducted at a single center. Thirty-six primary open-angle glaucoma Japanese patients who had no history of surgery were enrolled. The patients were prescribed 0.0015% topical tafluprost once daily to one eye that had the more severe visual field disorder, and observed during outpatient visits before and at 30, 60, and 90 days after starting treatment. At every visit, three examiners judged the presence of DUES unanimously by facial photographs including eyebrows and lower eyelids. The primary outcome variable was the incidence of DUES at the end of day 90 in the study as assessed by observer-masked facial photography. The patients were also asked if they noticed any subjective symptom of DUES. Gender, refraction, and intraocular pressure were evaluated as potential risk factors.

RESULTS

Thirty-two patients completed this clinical trial. DUES were identified objectively in 19% (6/32) of the patients after 90 days of treatment. The incidence was not related to gender, refraction, baseline or post-treatment intraocular pressure, or intraocular pressure reduction. Finally, 17% (1/6) of patients with objectively diagnosed DUES noticed the presence of DUES by themselves. No patient dropped out of the study because of DUES.

CONCLUSION

Similar to other prostaglandin analogs, topical use of tafluprost ophthalmic solution is associated with DUES as a local adverse reaction.

Bimatoprost protects retinal neuronal damage via Akt pathway

Worldwide, prostaglandin analogs, such as bimatoprost, have become the major therapeutic class for medical treatment of glaucoma because of their efficacy and generally well tolerated systemic safety profile. However, the detailed mechanism of the direct action of bimatoprost on retinal ganglion cells (RGC) has rarely been understood. Thus, in this study, we elucidated the mechanism of the protective effects of bimatoprost on RGC against oxidative stress. To examine the protective effects of bimatoprost, cultured RGC with various concentrations of bimatoprost (in both free acid and amide form) were exposed to l-buthionin-(S,R)-sulfoximine (BSO) plus glutamate or serum depletion in vitro and intravitreal injection of N-methyl-D-aspartate (NMDA) was used to induce retinal damage in vivo. To elucidate the protective mechanism of bimatoprost, we used western blot analysis to investigate the phosphorylation of Akt and extracellular signal-regulated kinase (ERK). Bimatoprost significantly reduced BSO plus glutamate- and serum deprivation-induced death in concentration-dependent manners. Bimatoprost induced activation of Akt and ERK, and a phosphatidylinositol 3-kinase inhibitor, LY294002, attenuated the protective effect of bimatoprost. On the other hand, a mitogen-activated protein kinase kinase inhibitor, U0126, exhibited protective effect unexpectedly. Moreover, ERK was more phosphorylated by attenuation of Akt activity in cultured RGC. In an in vivo study, bimatoprost reduced NMDA-induced RGC death. Taken together, these findings indicate that bimatoprost has protective effects on in vitro and in vivo retinal damage, suggesting that the mechanism underlying may be via the Akt pathway, which may modulate the ERK pathway.

Current status of unoprostone for the management of glaucoma and the future of its use in the treatment of retinal disease

INTRODUCTION

Optic nerve and retinal diseases such as glaucoma, age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are significant public health concerns and have a momentous impact on patients' functional status and quality of life. These diseases are among the most common causes of visual impairment worldwide and account for billions of dollars in healthcare expenditures and lost productivity. The importance of adequate treatment of these conditions and the need for efficacious therapeutic drugs cannot be overstated. Unoprostone continues to be developed as a potential treatment for these debilitating diseases.

AREAS COVERED

This review provides background information on unoprostone isopropyl (unoprostone), a prostanoid and synthetic docosanoid approved for the treatment of open-angle glaucoma and ocular hypertension, and recapitulates safety and efficacy data as it relates to this indication. Additionally, this review describes potential new uses of unoprostone as therapy for dry AMD and RP. A literature search of peer-reviewed publications was performed utilizing PubMed. Searches were last updated on 10 September 2012.

EXPERT OPINION

Current data indicate that unoprostone does significantly lower intraocular pressure (IOP) and has a favorable safety and tolerability profile. However, the IOP-lowering effects of unoprostone do not compare with other commercially available prostanoids and it has the disadvantage of a twice-daily rather than once-daily dosing regimen. Nonetheless, recent data suggest that unoprostone may improve neuronal survival and increase ocular blood flow, indicating that it may have some value as a therapy for glaucoma, RP and dry AMD. Further studies are needed to confirm whether unoprostone provides any clinically significant advantage over the other commercially available prostanoids.

Topical prostaglandin analogues and conjunctival inflammation in uveitic glaucoma

Purpose:

A pilot study to determine whether topical prostaglandin analogues alter the expression of conjunctival inflammatory markers in patients with uveitic glaucoma.

Methods:

Prospective, single-masked case series of 20 patients with uveitis and secondary raised intraocular pressure. Participants were divided into four groups of five patients dependent on their use of topical medication: (1) prostaglandin analogues only, (2) corticosteroids only, (3) both prostaglandin analogues and corticosteroids, (4) no topical medication. Conjunctival cells were harvested by impression cytology and were examined for inflammatory markers (CD3, CD54, HLA-DR, CCR4, CCR5) by flow cytometry. A tear fluid sample was also examined for inflammatory cytokines (IL-12p70, IL-2, IL-10, IL-8, IL-6, IL-4, IL-5, IFN-gamma, IL-1beta, IFN-alpha, IFN-beta) by multiplex bead arrays.

Results:

All groups demonstrated increased markers of conjunctival inflammation. There was no significant difference in levels of any inflammatory markers between the four groups, suggesting that the use of topical prostaglandin analogues does not increase conjunctival levels of inflammation beyond those already seen in uveitis.

Conclusions:

The use of topical prostaglandins does not appear to induce conjunctival inflammation over that which is already present in patients with uveitic glaucoma. This supports the use of topical prostaglandin analogues in patients with uveitic glaucoma, indicating that their use is unlikely to adversely affect subsequent glaucoma filtration surgery through the induction of chronic conjunctival inflammation.

Intravitreal diclofenac versus intravitreal triamcinolone acetonide in the treatment of diabetic macular edema

PURPOSE

To compare the efficacy and safety of intravitreal diclofenac versus intravitreal triamcinolone acetonide in the treatment of diabetic macular edema.

METHODS

Thirty-two eyes with diffuse diabetic macular edema were randomly allocated to intravitreal injection of 4 mg/0.1 mL of triamcinolone (Group 1: N = 16) or 500 μg/0.1 mL of diclofenac (Group 2: N = 16). Preoperative and postoperative visual acuity, intraocular pressure, and central macular thickness were recorded and compared between the 2 groups up to 12 weeks.

RESULTS

Both groups showed statistically significant reduction in central macular thickness (triamcinolone: P = 0.02 and diclofenac: P = 0.01), without statistically significant difference between the 2 groups. Visual improvement was significant only in triamcinolone group (P = 0.05). However, the 2 groups showed no statistically significant difference in mean visual acuity or mean line improvement. Transient elevation of intraocular pressure occurred in 12.5% of the triamcinolone group. Diclofenac group showed statistically significant reduced intraocular pressure (P = 0.02).

CONCLUSION

Intravitreal diclofenac is effective in the treatment of diffuse diabetic macular edema up to 12 weeks. Intravitreal triamcinolone and diclofenac appear to have comparable therapeutic effects on retinal thickness. The degree of visual improvement is higher with triamcinolone.