Effects of prostaglandin F(2α) analogues on endothelin-1-induced impairment of rabbit ocular blood flow: comparison among tafluprost, travoprost, and latanoprost

Novel frontiers in neuroprotective therapies in glaucoma: Molecular and clinical aspects

In the last years, neuroprotective therapies have attracted the researcher interests as modern and challenging approach for the treatment of neurodegenerative diseases, aimed at protecting the nervous system from injuries. Glaucoma is a neurodegenerative disease characterized by progressive excavation of the optic nerve head, retinal axonal injury and corresponding vision loss that affects millions of people on a global scale. The molecular basis of the pathology is largely uncharacterized yet, and the therapeutic approaches available do not change the natural course of the disease. Therefore, in accordance with the therapeutic regimens proposed for other neurodegenerative diseases, a modern strategy to treat glaucoma includes prescription of drugs with neuroprotective activities. With respect to this, several preclinical and clinical investigations on a plethora of different drugs are currently ongoing. In this review, first, the conceptualization of the rationale for the adoption of neuroprotective strategies for retina is summarized. Second, the molecular aspects highlighting glaucoma as a neurodegenerative disease are reported. In conclusion, the molecular and pharmacological properties of most promising direct neuroprotective drugs used to delay glaucoma progression are examined, including: neurotrophic factors, NMDA receptor antagonists, the α2-adrenergic agonist, brimonidine, calcium channel blockers, antioxidant agents, nicotinamide and statins.

Nicotinamide Prevents Retinal Vascular Dropout in a Rat Model of Ocular Hypertension and Supports Ocular Blood Supply in Glaucoma Patients

Purpose

To investigate whether nicotinamide (NAM) modulates retinal vasculature in glaucoma.

Methods

This was a prospective controlled clinical trial investigating animal and human histopathology. Participants included normotensive and ocular hypertensive rats, postmortem human ocular tissue, glaucoma patients (n = 90), and healthy controls (n = 30). The study utilized histopathology, computer-assisted retinal vasculature analysis, optical coherence tomography angiography (OCTA), and NAM treatment. The main outcome measures included retinal vascular parameters in rats as assessed by AngioTool; retinal vasculature integrity in rats and humans as assessed by histopathology, antibody-staining, and ImageJ-based measurements; and retinal perfusion density (PD) and flux index in humans as assessed by OCTA.

Results

A number of vessel parameters were altered in ocular hypertension/glaucoma compared to healthy controls. NAM treatment improved the retinal vasculature in ocular hypertensive rats, with an increase in mean vessel area, percentage area covered by vessels, total vessel length, total junctions, and junction density as assessed by AngioTool (all P < 0.05); vessel wall integrity as assessed by VE-cadherin antibody staining was also improved (P < 0.01). In humans, as assessed by OCTA, increases in PD in the optic nerve head and macula complete image (0.7%, P = 0.04 and 1.0%, P = 0.002, respectively) in healthy controls, and an increase in the temporal quadrant of the macula (0.7%, P = 0.02) in glaucoma patients was seen after NAM treatment.

Conclusions

NAM can prevent retinal vascular damage in an animal model of glaucoma. After NAM treatment, glaucoma patients and healthy controls demonstrated a small increase in retinal vessel parameters as assessed by OCTA.

Neuroaxonal and cellular damage/protection by prostanoid receptor ligands, fatty acid derivatives and associated enzyme inhibitors

Cellular and mitochondrial membrane phospholipids provide the substrate for synthesis and release of prostaglandins in response to certain chemical, mechanical, noxious and other stimuli. Prostaglandin D₂, prostaglandin E₂, prostaglandin F_2α, prostaglandin I₂ and thromboxane-A₂ interact with five major receptors (and their sub-types) to elicit specific downstream cellular and tissue actions. In general, prostaglandins have been associated with pain, inflammation, and edema when they are present at high local concentrations and involved on a chronic basis. However, in acute settings, certain endogenous and exogenous prostaglandins have beneficial effects ranging from mediating muscle contraction/relaxation, providing cellular protection, regulating sleep, and enhancing blood flow, to lowering intraocular pressure to prevent the development of glaucoma, a blinding disease. Several classes of prostaglandins are implicated (or are considered beneficial) in certain central nervous system dysfunctions (e.g., Alzheimer’s, Parkinson’s, and Huntington’s diseases; amyotrophic lateral sclerosis and multiple sclerosis; stroke, traumatic brain injuries and pain) and in ocular disorders (e.g., ocular hypertension and glaucoma; allergy and inflammation; edematous retinal disorders). This review endeavors to address the physiological/pathological roles of prostaglandins in the central nervous system and ocular function in health and disease, and provides insights towards the therapeutic utility of some prostaglandin agonists and antagonists, polyunsaturated fatty acids, and cyclooxygenase inhibitors.

Effectiveness and safety of tafluprost in primary open-angle glaucoma and ocular hypertension: a post-marketing phase IV study in China

BACKGROUND

Prostaglandin analogs (PGAs) are the first-line treatment for primary open-angle glaucoma (POAG) and ocular hypertension (OH). This study aimed to confirm the effectiveness and safety of Tapros® (0.0015% tafluprost eye drops) in Chinese patients with POAG and OH.

METHODS

This phase IV, multicenter, non-comparative, prospective study enrolled patients with POAG and OH in China between 12/27/2017 and 04/15/2020. Patients who were treatment-naïve or untreated within one month (group A) or with unreached intraocular pressure (IOP) target after previous monotherapy of other PGAs (group B) or non-PGA IOP-lowering drugs (group C) were treated with 0.0015% tafluprost for three months. The IOP reduction, response rate, and safety were observed.

RESULTS

There were 165, 89, and 31 patients in groups A, B, and C, with baseline IOPs of 22.4 ± 4.7, 21.0 ± 3.5, and 22.5 ± 3.2 mmHg, respectively. The least-square means and percentages of IOP reduction at 3 months for groups A, B, and C were 4.7 (19.8%), 1.6 (6.1%), and 4.6 mmHg (20.3%), respectively. A significant reduction in IOP was observed at each visit compared with baseline (all P < 0.05). At the final visit, 57.0% of the participants in group A achieved an IOP reduction of ≥ 20%, while 40.4% and 77.4% in groups B and C achieved an IOP reduction of ≥ 10%. Fifty-eight treatment-related adverse events occurred in 46 participants (15.7%), of which the most common one was conjunctival hyperemia (34/293, 11.6%).

CONCLUSIONS

Tafluprost showed a sustained and significant effect with tolerable adverse events in Chinese patients with POAG and OH who were treatment-naïve or untreated within one month or received prior treatments with unsatisfying outcomes.

Remodeling of the Lamina Cribrosa: Mechanisms and Potential Therapeutic Approaches for Glaucoma

Glaucomatous optic neuropathy is the leading cause of irreversible blindness in the world. The chronic disease is characterized by optic nerve degeneration and vision field loss. The reduction of intraocular pressure remains the only proven glaucoma treatment, but it does not prevent further neurodegeneration. There are three major classes of cells in the human optic nerve head (ONH): lamina cribrosa (LC) cells, glial cells, and scleral fibroblasts. These cells provide support for the LC which is essential to maintain healthy retinal ganglion cell (RGC) axons. All these cells demonstrate responses to glaucomatous conditions through extracellular matrix remodeling. Therefore, investigations into alternative therapies that alter the characteristic remodeling response of the ONH to enhance the survival of RGC axons are prevalent. Understanding major remodeling pathways in the ONH may be key to developing targeted therapies that reduce deleterious remodeling.

Effect of Rho Kinase Inhibitor Ripasudil (K-115) on Isolated Porcine Retinal Arterioles

Purpose: To investigate the vasorelaxation effect of ripasudil (K-115), a novel Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor, on isolated retinal arterioles. We determined whether the actions of ripasudil on the retinal microvascular diameter were dependent on the endothelium and/or potassium channels in the smooth muscle, with the goals of uncovering the signaling mechanisms required for this vasomotor activity and inhibiting the action of endothelin-1 (ET-1). Methods: In this in vitro study, we isolated porcine retinal arterioles, which were cannulated and pressurized without flow. We recorded diametric changes using videomicroscopic techniques. Results: In a dose-dependent (10 nM-30 μM) manner, retinal arterioles were relaxed in response to ripasudil [maximum % resting diameter, 160.3% ± 7.7% (mean ± standard error of the mean)]. The ripasudil-induced vasorelaxation was unaffected by endothelium removal, using nonselective potassium channel blocker tetraethylammonium, Ca²⁺-activated large-conductance potassium channel blocker iberiotoxin, voltage-gated potassium channel blocker 4-AP, ATP-sensitive potassium channel blocker glibenclamide, and inward rectifier potassium channel blocker BaCl₂. Ripasudil prevented ET-1-caused vasoconstriction of the retinal arterioles regardless of the presence of endothelium to a similar extent. Conclusion: The ROCK inhibitor ripasudil elicits endothelium-independent relaxation and inhibits the action of ET-1 on the retinal arterioles. Determining the relaxation properties of ripasudil on the retinal microvasculature will likely support the development of potential therapies for glaucoma.

Intraocular pressure fluctuation and neurodegeneration in the diabetic rat retina

BACKGROUND AND PURPOSE

Early retinal neurodegeneration occurs as one of the complications of diabetes even before clinically detectable diabetic vascular retinopathy. The pathogenesis of retinal diabetic neuropathy is still not well understood. We investigated the serial changes or fluctuations in intraocular pressure (IOP) and examined their roles in the pathogenesis of neuronal degeneration in diabetic retina.

EXPERIMENTAL APPROACH

Male Sprague Dawley rats with streptozotocin-induced diabetes were treated with ophthalmic preparations of brinzolamide, latanoprost, both drugs (combined treatment) or saline for 8 weeks. IOP was measured daily under general anaesthesia using a rebound tonometer. Antegrade axoplasmic flow in the optic nerve was assessed with a fluorescent substrate. Immunohistochemical staining, TUNEL assays and western blots were also used.

KEY RESULTS

The fluctuation of IOP was higher in the diabetes group than in the normal control or the combined treatment group. Diabetes-induced apoptosis of retinal ganglion cells was decreased by combined treatment. Increased expression of glial fibrillary acidic protein or Iba-1 in the retina or optic nerve head, induced by diabetes, was attenuated only by the combined treatment. Intercellular adhesion molecule-1 was increased in diabetic rats but not in the combined treatment group. Diabetes-induced loss of antegrade axoplasmic transport was partially relieved with combined treatment.

CONCLUSION AND IMPLICATIONS

Elevated IOP fluctuations seemed to be associated with the gliosis, neuroinflammation, and neurodegeneration induced by diabetes. The loss of retinal ganglion cells might be relieved by IOP-lowering medication. The improvement of unstable perfusion pressure could play a role in neuroprotection in the diabetic retina.

[The role of the endothelin system in the pathogenesis of eye diseases]

The endothelin system (ES) plays a complex role in the pathogenesis of various eye diseases as a local regulator of vascular tone as well as many other physiological processes. Components of ES - endothelins and their receptors - can be found nearly in all cellular structures of the eye, their concentration increases in the presence of many eye diseases. In glaucoma, ES is involved in the mechanisms of eye hypertension by influencing the secretion and outflow of aqueous humor. The increase of endothelin level leads to the decrease of perfusion pressure, hypoxia, astrocyte proliferation, increase of density and rigidity of lamina cribrosa, apoptosis of neural cells, and has a profibrogenic effect. In retinal pathology, increase of endothelins disturbs autoregulation of retinal blood vessels changing the neurovascular interactions, breaks intercellular contacts in the retina, promotes neoangiogenesis. In diabetic retinopathy, ES contributes to the development of microangiopathy and proliferative vitreoretinopathy. The review discusses the possibility of correcting ES activity in the eye with medications by influencing its synthesis, cleavage and receptor binding.

The Sustained Release of Tafluprost with a Drug Delivery System Prevents the Axonal Injury-induced Loss of Retinal Ganglion Cells in Rats

PURPOSE

To investigated whether a new drug delivery system (DDS) could enable the controlled release of tafluprost and suppress retinal ganglion cell (RGC) death in rats after optic nerve transection (ONT).

METHODS

A DDS containing 0.04%, 0.20% or 1.00% tafluprost, or vehicle, was injected intravitreally in 8-12-week-old male Sprague-Dawley rats 7 days before ONT, and the retinas were extracted 7 days after ONT. For comparison, eye drops containing 0.0015% tafluprost or vehicle were used once a day. The extracted retinas were analyzed with liquid chromatography-tandem mass spectrometry, immunohistochemistry and western blotting.

RESULTS

The level of tafluprost acid in the groups that received the 0.20% and 1.00% tafluprost DDSs was stable, and higher than the maximum concentration in the eye drop group, even after 14 days. In the retinas treated with the 1.00% tafluprost DDS, the active form of the drug had a high concentration (~50 times higher than eye drops), but no significant IOP difference compared with its vehicle in this study. The 1.00% tafluprost DDS group also had less cleaved α-fodrin and fewer c-Jun-positive cells than the vehicle DDS group.

CONCLUSIONS

This study found that a newly developed DDS allowed the controlled release of tafluprost and prevented the loss of RGCs after ONT IOP independently. The duration of drug action on the target site was longer with a tafluprost DDS than with topical instillation and should therefore reduce problems related to lack of patient compliance. This system may also enable new treatments to prevent RGC degeneration in diseases such as glaucoma.

Pulse Waveform Analysis of the Ocular Blood Flow Using Laser Speckle Flowgraphy before and after Glaucoma Treatment

Although reduction in intraocular pressure (IOP) is the principle of glaucoma treatment, impaired ocular blood flow is believed to play a role in the progression of glaucoma. This study evaluated the effect of glaucoma treatment on pulse waveforms for optic nerve head (ONH) microcirculation in patients with glaucoma. Fifty-one subjects were included on the basis of the glaucoma treatment administered, which involved instillation of prostaglandin (PG) analogs (PG group; n = 28) or trabeculectomy (trabeculectomy group; n = 23). ONH blood flow, represented by the mean blur rate (MBR_T) and pulse waveforms, was measured using laser speckle flowgraphy before and 1 and 3 months after treatment. Three months after treatment, IOP exhibited a significant decrease (p < 0.05). Although there was no significant change in MBR_T after treatment, the acceleration time index (ATI) significantly decreased (p=0.034) in the PG group. In the trabeculectomy group, there was no significant change in the MBR_T after treatment, while fluctuation (p=0.019) and blowout score (BOS) (p=0.036) exhibited significant decrease and increase, respectively. Multiple regression analysis showed that mean deviation was significantly associated with the rate of change in the BOS (p=0.013), age was a significant contributing factor for the rate of change in fluctuation in the trabeculectomy group, reflection was significantly associated with the ATI (p=0.037) in the in the PG group. Both glaucoma treatments can change the pulse waveforms, with MBR_T remaining unchanged, and IOP reduction owing to the treatment may contribute to stable blood flow in the tissue area of the ONH. As impaired ocular blood flow plays a role in the progression of glaucomatous damage, it would be beneficial if glaucoma treatment could improve the stability of ONH microcirculation.

Effects of the Glaucoma Drugs Latanoprost and Brimonidine on Corneal Temperature

Purpose

The aim of this study was to investigate the effects of the glaucoma drugs latanoprost, brimonidine, and the combination of both on the central corneal temperature (CT) of healthy subjects by means of infrared thermography. Changes of the central CT may reflect changes of ocular blood flow.

Methods

Before application and during 2 hours after the application of latanoprost, brimonidine, or the combination of both in one eye, the CT in both eyes of 40 healthy subjects was measured repeatedly.

Results

Brimonidine reduced CT by approximately 0.5°C. This effect was statistically significant (P < 0.0001). Latanoprost, however, had a very small and insignificant influence (P = 0.47). Accordingly, the combination of brimonidine and latanoprost also reduced CT up to 0.5°C, and this effect was statistically significant (P < 0.0001).

Conclusions

Brimonidine, but not latanoprost, had a significant effect on central CT. This cooling effect of brimonidine is most probably due to a drug-induced reduction of blood circulation in the ciliary body and iris and to a certain extent also to a reduction of blood flow in the fundus of the eye.

Translational Relevance

This study shows evidence that thermography of the cornea provides indirect information on the influence of drugs on the blood flow to the anterior segment of the patient's eye.

Assessment of the optic nerve head, peripapillary, and macular microcirculation in the newly diagnosed patients with primary open-angle glaucoma treated with topical tafluprost and tafluprost/timolol fixed combination

RELEVANCE:

The ability of antiglaucoma drugs to improve ocular hemoperfusion is an important aspect of their action. Tafluprost is the first preservative-free prostaglandin analog. The efficacy and safety of tafluprost, as well as tafluprost/timolol fixed combination (FC), were demonstrated in randomized multicenter trials. However, there is no literature on the effect of tafluprost and its FC on the peripapillary and macular blood flow.

PURPOSE:

To determine the changes of microcirculation in the optic nerve head (ONH), peripapillary retina, and macula in patients with newly diagnosed primary open-angle glaucoma (POAG) under the topical tafluprost and tafluprost/timolol FC treatment.

MATERIALS AND METHODS:

Optical coherence tomography angiography (OCT-A) was performed in dynamics with an interval of a week in 36 patients (36 eyes) with a newly diagnosed initial stage of POAG: 12 eyes with tafluprost, 12 – tafluprost/timolol FC, and 12 – no topical treatment (the control group). The change in intraocular pressure (IOP), mean ocular perfusion pressure (MOPP) of the eye, and vessel density (VD) inside the ONH (inside disc), as well as in the peripapillary retina and macula, was evaluated by comparing paired repeated observations using the median growth analysis.

RESULTS:

In the tafluprost group, there were a decrease in IOP by 19.4% and an increase in MOPP by 8.7% from the reference level. In the tafluprost/timolol group, these figures were 43% and 30.1%, respectively. OCT-A values did not change reliably, except for VD inside disc: the median growth of the tafluprost group was 2.28 (P = 0.02) and of the tafluprost/timolol group was 1.82 (P = 0.03). These changes were obtained in 11 of 12 patients in each group under treatment. In control group, all indicators remained unchanged.

CONCLUSIONS:

A significant increase of MOPP and a decrease of VD in the ONH in patients with initial glaucoma occurred within a week under the topical tafluprost or its FC. This can be explained by the restoration of autoregulation of the ocular blood flow in conditions of pronounced hypotensive effect of the drugs.

Preperimetric Glaucoma Prospective Observational Study (PPGPS): Design, baseline characteristics, and therapeutic effect of tafluprost in preperimetric glaucoma eye

Purpose

There is no consensus on the diagnosis or treatment policy for Preperimetric Glaucoma (PPG) because the pathogenesis of PPG is not clear at this time. Preperimetric Glaucoma Prospective Observational Study (PPGPS) is a first multicenter, prospective, observational study to clarify the pathogenesis of PPG. This article indicates study design, patient baseline characteristics, and analysis focused on optic nerve head (ONH) blood flow in PPG, as well as the intraocular pressure (IOP) -lowering effect and ONH blood flow-improving effects of Tafluprost.

Method

In this study, 122 eyes from 122 subjects (mean age: 53.1 ± 14.3) newly diagnosed as PPG were enrolled. The circumpapillary retinal nerve fiber layer thickness (cpRNFLT) was evaluated with optical coherence tomography (OCT). The ONH blood flow was measured with laser speckle flowgraphy. The therapeutic effect of Tafluprost was evaluated at Month 0 (ONH blood flow-improving effect) and Month 4 (IOP-lowering effect).

Results

The untreated IOP, cpRNFLT, and baseline Mean deviation (MD) value was 16.4 ± 2.5 mmHg, 80.4 ± 8.2 μm, and -0.48 ± 1.29 dB, respectively. In the site-specific visual field evaluation using the sector map, there was no appreciable site-specific visual field defect in the eye with PPG. The inferior region of cpRNFLT in 4-quadrant OCT sector analysis and 6 o’clock region in 12-o’clock OCT sector analysis was the highest rate of abnormality in PPG eyes. Topical administration of Tafluprost significantly reduced IOP from 16.4 ± 2.5 mmHg at baseline to 14.5 ± 2.3 mmHg at Month 4 (P < 0.001, paired t-test). In the linear regression analysis, there was a significant relationship between the increase of ONH blood flow and baseline value.

Conclusion

PPGPS is a first prospective study focusing on the pathology of PPG. This study is expected to elucidate the pathology of PPG, with evidence useful for determining a treatment strategy for PPG.

Retinal Blood Flow Velocity Change in Parafoveal Capillary after Topical Tafluprost Treatment in Eyes with Primary Open-angle Glaucoma

Although ocular circulation at the retina and optic disc is known to be associated with the pathology of glaucoma, direct measurement of blood flow velocity has been difficult to obtain. This prospective observational study enrolled 11 consecutive patients with treatment-naïve primary open-angle glaucoma (POAG) and 11 healthy subjects, and the effects of topical tafluprost treatment on ocular circulation were examined at baseline and at 1, 4, and 12 weeks after initiating treatment with topical tafluprost on POAG patients using multiple modalities, which include adaptive optics scanning laser ophthalmoscopy (AOSLO). Baseline mean intraocular pressure (IOP) was significantly higher and mean parafoveal blood flow velocity (pBFV) was significantly lower in POAG eyes than in healthy eyes. Mean IOP was significantly decreased (1 week, −19.1%; 4 weeks, −17.7%; and 12 weeks, −23.5%; all P < 0.001) and mean pBFV was significantly increased from the baseline at all follow-up periods after initiating treatment (1 week, 14.9%, P = 0.007; 4 weeks, 21.3%, P < 0.001; and 12 weeks, 14.3%, P = 0.002). These results reveal that tafluprost may not only lower IOP but may also improve retinal circulation in POAG eyes and AOSLO may be useful to evaluate retinal circulatory change after treatment.

Tafluprost Ophthalmic Solution 0.0015 %: A Review in Glaucoma and Ocular Hypertension

Tafluprost ophthalmic solution 0.0015 % preserved with benzalkonium chloride (BAK) 0.001 % is available in several Asian countries, including Japan. In pivotal trials, BAK-preserved tafluprost ophthalmic solution 0.0015 % lowered intraocular pressure (IOP) more effectively than placebo in Asian patients with normal-tension glaucoma and was at least as effective as latanoprost ophthalmic solution 0.005 % in Asian patients with primary open-angle glaucoma or ocular hypertension. In other prospective studies in Asian patients with glaucoma or ocular hypertension, tafluprost ophthalmic solution 0.0015 % was at least as effective as latanoprost ophthalmic solution 0.005 % or travoprost ophthalmic solution 0.004 % in terms of IOP lowering, and was considered easier to use and/or store. The efficacy of tafluprost ophthalmic solution 0.0015 % was maintained in the longer term. Tafluprost ophthalmic solution 0.0015 % was generally well tolerated. In conclusion, BAK-preserved tafluprost ophthalmic solution 0.0015 % remains a useful option for the treatment of Asian patients with glaucoma and ocular hypertension.

Impact of prostaglandin glaucoma drops on platelet-activating factor action: an in vitro study

AIM

The aim of this study was to investigate the effect of different prostaglandin analogs on platelet-activating factor (PAF) levels.

METHODS

Three prostaglandin analogs were selected: bimatoprost 0.3 mg/mL, latanoprost 50 μg/mL, and tafluprost 15 μg/mL. Each drug sample was tested for its ability to cause platelet aggregation, which was measured as PAF-induced aggregation, before and after the addition of various concentrations of the examined sample, creating a linear curve of percentage inhibition (ranging from 0% to 100%) versus different concentrations of the sample. The concentration of the sample that inhibited 50% PAF-induced aggregation was calculated based on this curve, and this value was defined as IC50. In addition, the effect of eye drops on PAF metabolism was examined, through an in vitro analysis on PAF basic metabolic enzymes (PAF-cholinephosphotransferase, PAF-acetyl-CoA:1-O-alkyl-sn-glycero-3-phosphocholine acetyltransferase, and PAF-acetylhydrolase).

RESULTS

The IC50 values for Lumigan UD^® (bimatoprost 0.3 mg/mL), Monoprost^® (latanoprost 50 μg/mL), and Saflutan (tafluprost 15 μg/mL) were 8.7, 0.28, and 1.4 μg/mL, respectively.

DISCUSSION

All three prostaglandin analogs suspended PAF, but bimatoprost induced the most potent inhibition, compared to tafluprost and to the weak effect of latanoprost.

Optic Nerve Head Blood Flow, as Measured by Laser Speckle Flowgraphy, Is Significantly Reduced in Preperimetric Glaucoma

PURPOSE

To compare optic nerve head (ONH) blood flow in healthy eyes, eyes with preperimetric glaucoma (PPG), and eyes with mild normal-tension glaucoma (NTG) using laser speckle flowgraphy (LSFG).

METHODS

In 172 eyes (normal: 44 eyes; PPG: 62 eyes; mild NTG: 66 eyes), LSFG was used to measure mean blur rate in the ONH tissue area (MBR_T), an index of capillary blood flow. Multiple regression analysis was performed to determine factors affecting circumpapillary retinal nerve fiber layer thickness (cpRNFLT), mean deviation (MD) and pattern standard deviation (PSD) of the visual field.

RESULTS

Despite similar characteristics in age, refractive error and systemic variables among the study groups, MBR_T in the normal eyes differed significantly from both the PPG and mild NTG eyes (P = 0.001, P < 0.001, respectively). Multiple regression analysis revealed that MBR_T was an independent factor affecting cpRNFLT, MD and PSD (P < 0.001, P = 0.001, P = 0.003, respectively).

CONCLUSION

ONH blood flow was detectibly reduced in eyes with PPG, in close association with structural and visual field damage. This suggests that measuring ONH tissue-area blood flow with LSFG may be a useful way of monitoring glaucoma severity, even in the early stages of glaucoma.

Recent Clinical Applications of Laser Speckle Flowgraphy in Eyes with Retinal Disease

Retinal diseases related to ischemia, such as diabetic retinopathy, are the main cause of blindness worldwide. However, the pathogenesis of these diseases remains unclear, as does the time course of associated changes in ocular blood flow. Laser speckle flowgraphy (LSFG), which uses the laser speckle phenomenon to detect and quantify ocular circulation, is a promising candidate for a noninvasive method to measure ocular blood flow in living eyes. A recently developed LSFG measurement parameter, mean blur rate (MBR), can serve as a quantitative and reproducible index of retinal blood cell velocity. Mean blur rate can be used in the study of retinal diseases to evaluate microcirculation in the retinal vessels, choroid, and optic nerve head. In addition to overall MBR (MA), LSFG measurements of optic nerve head microcirculation can be divided into vessel-area MBR (MV) and tissue-area MBR (MT). Absolute values for MT have been shown to be linearly correlated with capillary blood flow, regardless of fundus pigmentation. Recently, there has been an increasing number of reports on the clinical applications of LSFG in retinal disease.

Comparison of Ocular Pulse Amplitude Lowering Effects of Preservative-Free Tafluprost and Preservative-Free Dorzolamide-Timolol Fixed Combination Eyedrops

Purpose. To compare the ocular pulse amplitude (OPA) lowering effects of preservative-free tafluprost and dorzolamide-timolol fixed combination (DTFC) using dynamic contour tonometry. Methods. In total, 66 eyes of 66 patients with normal tension glaucoma (NTG) (n = 34) or primary open angle glaucoma (POAG) (n = 32) were included. Patients were divided into two groups: the preservative-free tafluprost-treated group (n = 33) and the preservative-free DTFC-treated group (n = 33). Intraocular pressure (IOP) was measured using Goldmann applanation tonometry (GAT). OPA was measured using dynamic contour tonometry; corrected OPA (cOPA) was calculated at baseline and at 1 week and 1, 3, and 6 months after treatment. Results. After 6 months of treatment, tafluprost significantly reduced IOP (P < 0.001). The OPA lowering effects differed significantly between the two treatment groups (P = 0.003). The cOPA-lowering effect of tafluprost (1.09 mmHg) was significantly greater than that of DTFC (0.36 mmHg) after 6 months of treatment (P = 0.01). Conclusions. Tafluprost and DTFC glaucoma treatments provided marked OPA and IOP lowering effects. Tafluprost had a greater effect than DTFC; thus, this drug is recommended for patients at risk of glaucoma progression, due to the high OPA caused by large fluctuations in IOP.

Comparison of Ocular Pulse Amplitude-Lowering Effects of Tafluprost and Latanoprost by Dynamic Contour Tonometry

PURPOSE

A prospective study was performed to compare the ocular pulse amplitude (OPA)-lowering effects of tafluprost and latanoprost, used in the treatment of glaucoma, using dynamic contour tonometry.

METHODS

The study population consisted of patients with normal-tension glaucoma (NTG) (n = 27) or primary open-angle glaucoma (POAG) (n = 14) treated with tafluprost and latanoprost. All patients were newly diagnosed with NTG and POAG and had undergone no previous treatment. Intraocular pressure (IOP) was measured by Goldmann applanation tonometry (GAT), OPA was measured by dynamic contour tonometry, and corrected OPA (cOPA) was calculated before and after 1 week, 1-3 months of treatment.

RESULTS

Initial IOP and OPA were 17.12 ± 3.75, 2.30 ± 0.56 mmHg and 17.53 ± 2.87, 2.65 ± 0.94 mmHg in the tafluprost and latanoprost groups, respectively. After 3 months of treatment, IOP and OPA were 13.00 ± 2.04 mmHg (24.1%) and 1.51 ± 0.30 mmHg (34.3%), respectively, in the tafluprost group. These values were 15.40 ± 2.32 mmHg (12.2%) and 2.08 ± 0.83 mmHg (21.5%), respectively, in the latanoprost group. Therefore, tafluprost significantly reduced IOP (P = 0.01), but OPA-lowering effects did not differ significantly between the 2 groups (P = 0.17). However, the cOPA-lowering effect of tafluprost (1.27 mmHg, 55.2%) was significantly greater than that of latanoprost (0.84 mmHg, 31.7%) after 3 months of treatment (P < 0.001).

CONCLUSIONS

Tafluprost and latanoprost, used to treat glaucoma, have marked OPA-lowering effects as well as IOP-lowering effects. Moreover, tafluprost has a greater effect than latanoprost. Therefore, it can be used for patients in need of IOP reduction and at risk of glaucoma progression.

In vitro Effects of Prostaglandin Analogs on Cultured Astrocytes Obtained from the Lamina Cribrosa

PURPOSE

To evaluate the effects of prostaglandin analogs (PGAs) on cell viability and apoptosis in cultured astrocytes obtained from the lamina cribrosa (LC) of the human optic nerve head (ONH).

METHODS

Astrocytes were cultured from LC samples obtained from human donor ONH and treated with three kinds of acid form of PGAs: latanoprost (LAT-A), tafluprost (TAF-A), and bimatoprost (BIM-A) (0.1, 1, 10, 50 and 100 ug/mL). Cell viability was assessed using the WST-1 assay. Cell apoptosis was measured using the deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) assay. Apoptotic protein expression was evaluated using western blot analysis.

RESULTS

ONH astrocytes expressed FP receptor in western blot analysis. In the presence of 0.1 ug/mL of LAT-A, BIM-A, and TAF-A, the cell viability was 85%, 85% and 82%, respectively. WST-1 assay revealed about 50% of cell viability following treatment with 50 ug/mL of all PGAs. After exposing astrocytes to 10 ug/mL of each PGA for 24 hours, apoptotic cells were stained in TUNEL assay. Western blot analysis revealed that the PGAs up-regulated Bax (pro-apoptotic protein) and down-regulated Bcl-xL (anti-apoptotic protein) in the astrocytes.

CONCLUSIONS

PGAs affected cell viability in cultured astrocytes obtained from human ONH LC. PGA treatment may induce apoptosis in ONH astrocytes.

Targeted delivery of antiglaucoma drugs to the supraciliary space using microneedles

PURPOSE

In this work, we tested the hypothesis that highly targeted delivery of antiglaucoma drugs to the supraciliary space by using a hollow microneedle allows dramatic dose sparing of the drug compared to topical eye drops. The supraciliary space is the most anterior portion of the suprachoroidal space, located below the sclera and above the choroid and ciliary body.

METHODS

A single, hollow 33-gauge microneedle, 700 to 800 μm in length, was inserted into the sclera and used to infuse antiglaucoma drugs into the supraciliary space of New Zealand white rabbits (N = 3-6 per group). Sulprostone, a prostaglandin analog, and brimonidine, an α₂-adrenergic agonist, were delivered via supraciliary and topical administration at various doses. The drugs were delivered unilaterally, and intraocular pressure (IOP) of both eyes was measured by rebound tonometry for 9 hours after injection to assess the pharmacodynamic responses. To assess safety of the supraciliary injection, IOP change immediately after intravitreal and supraciliary injection were compared.

RESULTS

Supraciliary delivery of both sulprostone and brimonidine reduced IOP by as much as 3 mm Hg bilaterally in a dose-related response; comparison with topical administration at the conventional human dose showed approximately 100-fold dose sparing by supraciliary injection for both drugs. A safety study showed that the kinetics of IOP elevation immediately after supraciliary and intravitreal injection of placebo formulations were similar.

CONCLUSIONS

This study introduced the use of targeted drug delivery to the supraciliary space by using a microneedle and demonstrated dramatic dose sparing of antiglaucoma therapeutic agents compared to topical eye drops. Targeted delivery in this way can increase safety by reducing side effects and could allow a single injection to contain enough drug for long-term sustained delivery.

Secondary neuroprotective effects of hypotensive drugs and potential mechanisms of action

Primary open-angle glaucoma, a long-term degenerative ocular neuropathy, remains a significant cause of vision impairment worldwide. While many risk factors have been correlated with increased risk for primary open-angle glaucoma, intraocular pressure (IOP) remains the only modifiable risk factor and primary therapeutic target. Pharmacologic therapies are administered topically; these include α(2)-agonists, β-antagonists, prostaglandin analogs and carbonic anhydrase inhibitors. Some of these topical medications exhibit secondary neuroprotective effects independent of their effect on IOP. This review covers the possible mechanisms of neuroprotection stimulated by drugs currently marketed for the lowering of IOP, based on known literature. While the neuroprotective properties of many glaucoma pharmaceuticals are promising from an experimental standpoint, key challenges for the development of new clinical practices include unknown systemic side effects, limited methods of drug delivery to the retina and optic nerve, and development of extended-release formulations.

Therapeutic uses of prostaglandin F(2α) analogues in ocular disease and novel synthetic strategies

The pharmacological management of glaucoma and ocular hypertension has significantly changed over the last 18 years with the introduction of PGF2α analogues, more specifically latanoprost (6), travoprost (8), bimatoprost (10) and tafluprost (12). Prostanoids are currently the first-line medicines among ocular antihypertensive drugs in terms of efficacy, safety, patient compliance and medical economy. Their ability to effectively reduce intraocular pressure with once-per-day dosing, ocular tolerability comparable to timolol and general lack of systemic adverse effects have made them the mainstay of pharmacological therapy for glaucoma and ocular hypertension all over the world. The present review reports a novel, convergent and highly diastereoselective method for the synthesis of PGF2α analogues from the structurally advanced prostaglandin phenylsulfone (5Z)-(+)-15 and new ω-chain synthons. The biochemistry, clinical efficacy and side effects of four commercially available PGF2α analogues, currently used as first-line agents for reducing intraocular pressure in patients with glaucoma or ocular hypertension, are also discussed.

Effects of antiglaucoma drugs on blood flow of optic nerve heads and related structures

An association between glaucoma development or progression and compromised ocular blood flow has been postulated as a result of population-based studies and prospective cohort studies. Blood flow in the optic nerve head (ONH) is of primary importance in the pathogenesis of glaucoma. The potential to modify the blood flow in the ONH and its related structures has been reported in various agents, including topical antiglaucoma drugs and systemic drugs such as calcium channel antagonists, which are reviewed in this manuscript. Clinical implications of the improvement in ocular blood flow on the treatment of glaucomatous optic neuropathy require further investigation.

Tafluprost once daily for treatment of elevated intraocular pressure in patients with open-angle glaucoma

Glaucoma is a leading cause of visual loss worldwide. Current antiglaucoma therapy focuses on lowering intraocular pressure to a safe level. In recent years, prostaglandin analogs have become the first-line agents for treating open angle glaucoma. Tafluprost, which was first reported in 2003, is a novel prostaglandin analog, and has been shown to be a potent ocular hypotensive agent in a number of preclinical and clinical studies. Also, its unique preservative-free formulation helps to decrease preservative-associated ocular disorders and improve patient compliance. In this review, studies from 2003 to 2012 focusing on the structure, metabolism, efficacy, and safety of tafluprost are summarized. These studies suggested that application of tafluprost once daily is a safe and effective treatment for patients with open angle glaucoma.

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.

The effects of prostaglandin analogues on intracellular Ca2+ in ciliary arteries of wild-type and prostanoid receptor-deficient mice

PURPOSE

To clarify the mechanism of prostaglandin (PG) analogue-dependent relaxation in ciliary arteries from wild-type (WT) and prostanoid receptor-deficient mice.

METHODS

The intracellular-free calcium concentration ([Ca(2+)](i)) in isolated WT mouse ciliary arteries was measured by fluorescence photometry. Reduction of [Ca(2+)](i) leading to vascular relaxation by PG analogues latanoprost, isopropyl unoprostone, or tafluprost was compared to the maximum increase of [Ca(2+)](i) by 50 mM KCl. The cyclooxygenase inhibitor indomethacin and the NO synthase inhibitor N(G)-nitro-(L)-arginine methylester ((L)-NAME) were added to investigate the involvement of vascular endothelial factors. Moreover, PG analogue-dependent reduction of [Ca(2+)](i) was measured in ciliary artery strips from FP, EP1, EP2, and EP3 receptor-deficient mice.

RESULTS

The 3 PG analogues reduced K(+)-dependent increase in [Ca(2+)](i) in a concentration-dependent manner. Indomethacin (10 μM) had little effect. The reductions of [Ca(2+)](i) induced by 10 μM PG analogues were not significantly affected by the treatment with the NO synthase inhibitor (L)-NAME (10(-4) M). The effect of all 3 PG analogues in FP and EP3 receptor-deficient arteries was similar to the effect in WT arteries. Latanoprost significantly enhanced the reduction of [Ca(2+)](i) in ciliary arteries from prostanoid EP1 and EP2 receptor-deficient mice compared to WT mice. Tafluprost had a similar effect in arteries from EP2 receptor-deficient mice.

CONCLUSIONS

PG analogues latanoprost, isopropyl unoprostone, and tafluprost reduced the K(+)-dependent increase in [Ca(2+)](i) in isolated mouse ciliary arteries. Endothelial-derived factors and FP and EP3 receptors were not involved in the responses. The increased effectiveness of latanoprost and tafluprost in reducing [Ca(2+)](i) in EP1 and EP2 receptor-deficient arteries suggests that the PG analogues may act, at least partially, through nonprostanoid receptor pathways. For glaucoma patients, PG analogues can be selected to reduce the intraocular pressure and increase the ocular blood flow.

Differential pharmacology and clinical utility of preservative-free tafluprost in the treatment of ocular hypertension and glaucoma

Glaucoma is a chronic disease requiring lifelong treatment. Discomfort due to medications may affect patients’ quality of life and may cause poor compliance, which leads to poor intraocular pressure control. To minimize the side effects of long-term treatment, preparations with lower benzalkonium chloride concentrations, preservative-free preparations and alternative preservatives have been developed and reported to have a lower rate of side effects. Tafluprost, launched on the ophthalmic market in 2008, is a new 16-phenoxy analogue of prostaglandin F_2α, clinically used as an ocular hypotensive agent for the treatment of glaucoma and ocular hypertension. The safety and intraocular pressure-lowering efficacy of tafluprost has been demonstrated in various preclinical and clinical studies.

Tafluprost: a novel prostaglandin analog for treatment of glaucoma

OBJECTIVE

The objective of this review is to evaluate the safety and efficacy of tafluprost, a fluoroprostaglandin receptor analog, for reduction of intraocular pressure in open angle glaucoma and ocular hypertension.

METHODS

A search of published literature was performed on the PubMed database using the search term "tafluprost." The literature search identified 48 publications, including clinical and preclinical studies, from 2003 to 2011. From these ressults, articles available in the English language and in full text were selected and systematically reviewed by the authors.

RESULTS

Recent studies have shown that tafluprost is an effective IOP-lowering medication. Evidence based medicine also reveals that tafluprost is safe and well-tolerated. Preservative-free tafluprost is as potent as the preserved formulation, but with fewer and milder ocular surface side effects.

CONCLUSION

Since its introduction in 2008, initial studies have demonstrated that preserved and preservative-free tafluprost formulations have proven efficacy and safety in the treatment of glaucoma and ocular hypertension. Larger studies with longer follow-up are needed to assess long-term safety, efficacy, and tolerability compared with other prostaglandin analogs used for treating glaucoma.

Effects of Rho-associated protein kinase inhibitors Y-27632 and Y-39983 on isolated rabbit ciliary arteries

PURPOSE

In normotensive eyes, reduced ocular blood flow can lead to glaucoma pathogenesis. Drugs that reduce intraocular pressure (IOP) often cause vasodilation of the ciliary arteries and improve blood flow to the eye. A novel class of drugs called Rho-associated coiled coil-forming protein kinase (ROCK) inhibitors can lower IOP. Therefore, we tested the ability of two ROCK inhibitors, Y-27632 and Y39983, to relax rabbit ciliary arteries.

METHODS

We measured in vitro ciliary artery smooth muscle contractions by isometric tension recordings and changes of intracellular free calcium concentration ([Ca(2+)](i)) by fluorescence photometry.

RESULTS

Both Y-27632 and Y-39983 induced a concentration-dependent relaxation in rabbit ciliary arteries precontracted with a high-potassium (high-K) solution. The amplitude of relaxation induced by Y-27632 and Y-39983 was not affected by either 100 μM N (G)-nitro-L: -arginine methyl ester (L: -NAME) or 10 μM indomethacin. In Ca(2+)-free solution, Y-27632 and Y-39983 significantly inhibited the transient contraction of ciliary arteries induced by 10 μM histamine. However, neither Y-27632 nor Y-39983 affected the elevation of [Ca(2+)](i) induced by high-K solution and histamine.

CONCLUSIONS

We concluded that Y-27632 and Y-39983 relaxed isolated rabbit ciliary artery segments in vitro. The mechanism of relaxation was not dependent on endothelial-derived factors such as nitric oxide (NO) or prostacyclin, nor was it dependent on changes in intracellular Ca(2+) concentration.

Endothelin antagonism as an active principle for glaucoma therapy

Endothelin, the most potent vasoactive peptide known to date, has been suggested to play a potential role in the pathogenesis of open-angle glaucoma. Open-angle glaucoma is the most common optic nerve head neuropathy and is associated with a loss of retinal ganglion cells and visual field damage. Although an increased intraocular pressure is a major risk factor for glaucomatous optic neuropathy, other factors such as a reduced ocular blood flow play an important role for appearance of the disease. Thus, treatment of glaucoma is focused on lowering of intraocular pressure and preventing the occurrence or progression of glaucomatous optic neuropathy. Endothelin participates in the regulation of intraocular pressure by an effect on trabecular outflow, the main route for aqueous humour outflow from the eye. Trabecular outflow is modulated by trabecular meshwork contractility which is affected by endothelin. In addition to the effects of endothelin in the anterior part of the eye, the vasoconstrictor causes a decrease in ocular blood flow followed by pathological changes in the retina and the optic nerve head which is assumed to contribute to the degeneration of retinal ganglion cells. In sum, inhibition of endothelin signalling leads to lowering of intraocular pressure and exerts neuroprotective effects. Thus, endothelin antagonism in the eye represents a promising approach for pharmacological treatment of glaucoma.