A topical nitric oxide-releasing dexamethasone derivative: effects on intraocular pressure and ocular haemodynamics in a rabbit glaucoma model

Nitric-Oxide-Releasing Dexamethasone Derivative NCX-1005 Improves Lung Function and Attenuates Inflammation in Experimental Lavage-Induced ARDS

Acute respiratory distress syndrome (ARDS) is a common complication of critical illness and remains a major source of morbidity and mortality in the intensive care unit (ICU). ARDS is characterised by diffuse lung inflammation, epithelial and endothelial deterioration, alveolar–capillary leak and oedema formation, and worsening respiratory failure. The present study aimed to investigate the anti-inflammatory activity of nitric-oxide-releasing dexamethasone derivative NCX-1005 as a potential novel drug for ARDS. Adult rabbits with lavage-induced ARDS were treated with dexamethasone i.v. (0.5 mg/kg; DEX) and nitro-dexamethasone i.v. (0.5 mg/kg, NCX-1005) or were untreated (ARDS). Controls represented healthy ventilated animals. The animals were subsequently oxygen-ventilated for an additional 4 h and respiratory parameters were recorded. Lung oedema, inflammatory cell profile in blood and bronchoalveolar lavage, levels of the cytokines (IL-1β, IL-6, IL-8, TNF-α), and oxidative damage (TBARS, 3NT) in the plasma and lung were evaluated. Nitric oxide-releasing dexamethasone derivative NCX-1005 improved lung function, reduced levels of cytokines, oxidative modifications, and lung oedema formation to similar degrees as dexamethasone. Only NCX-1005 prevented the migration of neutrophils into the lungs compared to dexamethasone. In conclusion, the nitric oxide-releasing dexamethasone derivative NCX-1005 has the potential to be effective drug with anti-inflammatory effect in experimental ARDS.

NO, CO and H2S based pharmaceuticals in the mission of vision (eye health): a comprehensive review

A set of well defined signaling molecules responsible for normal functioning of human physiology including nitric oxide along with carbon monoxide and hydrogen sulphide are referred as “gasotransmitters”. Due to their involvement in almost every system of a human body, the care of highly sensitive organs using these molecules as drugs represents highly fascinating area of research. In connection with these interesting aspects, the applied aspects of these gaseous molecules in maintaining healthy eye and vision have been targeted in this review. Several examples of eye-droppers including NORMs like latanoprost and nipradiol, CORMs like CORM-3 and CORM-A1, and Hydrogen sulfide releasing system like GYY4137 have been discussed in this context. Therefore the relation of these trio-gasotransmitters with the ophthalmic homeostasis on one hand, and de-infecting role on the other hand has been mainly highlighted. Some molecular systems capable of mimicking gasotransmitter action have also been introduced in connection with the titled theme.

Advances in the discovery of novel agents for the treatment of glaucoma

INTRODUCTION

Glaucoma, a neuropathy characterized by increased intraocular pressure (IOP), is the major cause of blindness worldwide and its treatment aims at reducing IOP.

AREAS COVERED

The authors review the design of the main classes of anti-glaucoma agents. Drugs which interfere with the aqueous humor secretion (adrenergic agonists/antagonists, carbonic anhydrase inhibitors) and with its outflow, by means of both conventional and non-conventional pathways (prostaglandin (PG) analogs, rho kinase inhibitors, nitric oxide (NO) donors) as well as new agents (adenosine receptors modulators, melatonin - fatty acid amide hydrolase hybrids, tyrosine kinase activators, natriuretic peptide analogs) are considered.

EXPERT OPINION

The anti-glaucoma drug field has undergone several developments in recent years with the approval of at least three new drugs belonging to novel pharmacological classes, the rho kinase inhibitors ripasudil and netarsudil, and the PG-NO donor hybrid latanoprostene bunod. Eye drops with combinations of two different drugs are also available, allowing for effective IOP control, with once daily administration for some of them, which assures a better patient compliance and ease of administration. Overall, after more than a decade without new anti-glaucoma drugs, the last year afforded interesting new pharmacological opportunities for the management of this disease.

Role of Histamine H₃ Receptor Antagonists on Intraocular Pressure Reduction in Rabbit Models of Transient Ocular Hypertension and Glaucoma

Intraocular pressure (IOP) has a tendency to fluctuate throughout the day, reaching its peak in the early morning in healthy subjects or glaucoma patients. Likewise, histamine tone also fluctuates over time, being lower at nighttime. Numerous studies have demonstrated a correlation between short-term IOP fluctuation and glaucoma progression; however, it has not yet been determined whether histamine plays a role in IOP fluctuations. The aim of this research was to establish the distribution of the histamine receptor proteins and respective mRNAs in the eye by western blot, immunohistochemistry and RT-PCR in New Zealand rabbits. Furthermore, we used a transient ocular hypertension (OHT) model induced by injection of 50 µL of 5% hypertonic saline into the vitreous and a stable OHT model (100 µL 0.1% carbomer in the anterior chamber) to address the potential IOP-lowering ability of H₃ receptor (H₃R) antagonists (ciproxifan, DL76 and GSK189254). IOPs were performed with a Tono-Pen at baseline and 60, 120 and 240 min post treatment after transient OHT induction and, every day for 12 days in the stable OHT model. All histamine receptor subtypes were localized in the rabbit retina and ciliary body/trabecular meshwork. All the treatments lowered IOP in a dose-dependent fashion between 0.3% and 1%. More specifically, the effects were maximal with ciproxifan at 60 min post-dose (IOP₆₀ change = −18.84 ± 4.85 mmHg, at 1%), remained stable until 120 min (IOP₁₂₀ change = −16.38 ± 3.8 mmHg, at 1%) and decayed thereafter to reach baseline values at 240 min. These effects were highly specific and dependent on histamine release as pre-treatment with imetit (H₃R agonist, 1%) or pyrilamine (H₁R antagonist, 1%) largely blocked ciproxifan-mediated effects. Color Doppler ultrasound examination was performed to evaluate changes in ophtalmic artery resistivity index (RI) before and after repeated dosing with DL 76, GSK189254, ciproxifan and timolol. Chronic treatments with H₃R antagonists and timolol improved the vascular performance of ophthalmic arteries and reduced retinal ganglion cell death. Oxidative stress was also reduced and measured 8-Hydroxy-2′-deoxyguanosine (8OHdG) expression, and by dihidroethydium (DHE) staining. These results demonstrated that the histamine system participates in IOP regulation and that H₃R antagonists could represent a future promising therapy for glaucoma. Further studies should be focused on the long-term IOP circadian fluctuations.

2-Benzylpiperazine: A new scaffold for potent human carbonic anhydrase inhibitors. Synthesis, enzyme inhibition, enantioselectivity, computational and crystallographic studies and in vivo activity for a new class of intraocular pressure lowering agents

Two series of 2-benzylpiperazines have been prepared and tested for the inhibition of physiologically relevant isoforms of human carbonic anhydrases (hCA, EC 4.2.1.1). The new compounds carry on one nitrogen atom of the piperazine ring a sulfamoylbenzamide group as zinc-binding moiety, and different alkyl/acyl/sulfonyl groups on the other nitrogen. Regio- and stero-isomers are described. The majority of these compounds showed Ki values in the low-medium nanomolar range against hCA I, II and IV, but not IX. In many instances interaction with the enzyme was enantioselective. The binding mode has been studied by means of X-ray crystallography and molecular modelling. Two compounds, evaluated in rabbit models of glaucoma, were able to significantly reduce intraocular pressure, making them interesting candidates for further studies.

A novel nitro-dexamethasone inhibits agr system activity and improves therapeutic effects in MRSA sepsis models without antibiotics

Methicillin-resistant Staphylococcus aureus (MRSA) sepsis is a life-threatening medical condition that involves systemic inflammation throughout the body. Glucocorticoids are widely used in combination with antibiotics in the treatment of MRSA sepsis to fight the overwhelming inflammation. Here, we describe the improved anti-inflammatory properties of a nitric oxide (NO)-releasing derivative of dexamethasone, ND8008. ND8008 affected MRSA biofilm formation, caused biofilm cell death, and reduced the effects of virulence factors, such as α-toxin, by inhibiting the activity of the Staphylococcus aureus accessory gene regulator (agr) system. Dosing of mice with ND8008 (127.4 nmol/kg, i.p.) alone greatly reduced the inflammatory response caused by MRSA blood stream infection and considerably increased the survival rate of septic mice. These findings suggest that this novel NO-releasing derivative of dexamethasone ND8008 could be helpful in the treatment of MRSA sepsis.

Non-continuous measurement of intraocular pressure in laboratory animals

Glaucoma is a leading cause of blindness, which is treatable but currently incurable. Numerous animal models therefore have both been and continue to be utilized in the study of numerous aspects of this condition. One important facet associated with the use of such models is the ability to accurately and reproducibly measure (by cannulation) or estimate (by tonometry) intraocular pressure (IOP). At this juncture there are several different approaches to IOP measurement in different experimental animal species, and the list continues to grow. We feel therefore that a review of this subject matter is timely and should prove useful to others who wish to perform similar measurements. The general principles underlying various types of tonometric and non-tonometric techniques for non-continuous determination of IOP are considered. There follows discussion of specific details as to how these techniques are applied to experimental animal species involved in the research of this disease. Specific comments regarding anesthesia, circadian rhythm, and animal handling are also included, especially in the case of rodents. Brief consideration is also given to possible future developments.

Short-term effects of intravitreal triamcinolone acetonide injection on ocular blood flow evaluated with color Doppler ultrasonography

AIM

To evaluate the changes in ocular blood flow with color Doppler ultrasonography (CDU) after intravitreal triamcinolone acetonide (IVTA) injection.

METHODS

A total of 46 patients who underwent IVTA (4 mg/0.1 mL) injection for diabetic macular edema (DME) (n=22), central retinal vein occlusion (CRVO) (n=12) and choroidal neovascular membrane (CNVM) (n=12) were included in the study. Peak systolic velocity (PSV), end diastolic velocity (EDV) and resistivity index (RI) were measured from the ophthalmic artery (OA), the central retinal artery (CRA) and the posterior ciliary artery (PCA) of each patient with CDU before, at the end of the first week and at the end of the first month following IVTA injection.

RESULTS

In the DME group, PSV of OA at the first of the first month (mean±SD) (37.48±10.87 cm/s) increased compared to pre-injection value (31.39±10.84 cm/s) (P=0.048). There was a statistically significant decrease (P=0.049) in PSV of CRA at the end of the first month (7.97±2.67 cm/s) compared to the pre-injection (9.47±3.37 cm/s). There was not any statistically significant difference on the other parameters in the DME group. Also, there was not any statistically significant difference on the ocular blood flow values in the CRVO and CNVM groups.

CONCLUSION

We observed that 4 mg/0.1 mL IVTA increased PSV of OA and decreased PSV of CRA in DME patients and did not have any effect on ocular blood flow values of CRVO and CNVM patients.

Association of eNOS polymorphisms with anterior chamber depth in han chinese: jiangsu eye study

Recently, a study reported that single nucleotide polymorphisms (SNP) in endothelial nitric oxide synthase (eNOS) were associated with primary angle closure glaucoma (PACG) in Australian cohort. In this study, we aimed to investigate whether those eNOS SNPs are associated with primary angle closure (PAC) or ocular biometric characteristics such as axial length (AL), anterior chamber depth (ACD), and diopter of spherical power (DS) in Han Chinese. The samples consisted of 232 PAC subjects and 306 controls collected from a population-based prevalence survey conducted in Funing County of Jiangsu, China. The rs3793342 and rs11771443 in eNOS were genotyped by TaqMan-MGB probe using the RT-PCR system. Our data did not identify any association of the eNOS SNPs with PAC. However, the analysis on the quantitative traits of ocular biometrics showed that the ACD of rs11771443 AA and GA carriers is significantly deeper than that of rs11771443 GG carriers (P = 0.0025), even though the AL and DS are not associated with rs11771443 genotypes. Rs3793342 was not associated with any biometric parameters including ACD, AL and DS. In summary, our data indicates that eNOS rs11771443 is associated with ACD and its role in the pathogenesis of PACG warranted further study.

Evaluation of ocular and general safety following repeated dosing of dexamethasone phosphate delivered by transscleral iontophoresis in rabbits

PURPOSE

To evaluate the toxicokinetics and tolerability (local ocular and general toxicity) of the anti-inflammatory agent, dexamethasone phosphate (a prodrug of dexamethasone) delivered to the eye in rabbits by transscleral iontophoresis.

METHODS

Female rabbits (n=6/group) received dexamethasone phosphate (40 mg/mL ophthalmic solution, EGP-437) transsclerally to the right eye (OD) using the Eyegate(®) II ocular iontophoresis delivery system once biweekly for 24 consecutive weeks at current doses of 10, 14, and 20 mA-min and current levels up to, and including -4 mA for 3.5-5 min. The study included 2 control groups (n=6/group): (1) a noniontophoresis control [an ocular applicator-loaded citrate buffer (placebo) without current] and (2) an iontophoresis control (a citrate buffer plus cathode iontophoresis at 20 mA-min, -4 mA for 5 min). Recoverability was evaluated 4 weeks following the last dose in 2 animals per group. The left eye (OS) was untreated and served as an internal control for each animal. Ocular and general safety of dexamethasone phosphate and dexamethasone were assessed. Other evaluations included toxicokinetics, ophthalmic examinations, intraocular pressure (IOP) measurements, electroretinographs, clinical observations, body weight, hematology and serum chemistry, gross necropsy, organ weight, and microscopic histopathology.

RESULTS

The biweekly transscleral iontophoresis with either the citrate buffer or dexamethasone phosphate at cathodic doses up to, and including 20 mA-min and currents up to, and including -4 mA for 24 weeks was well-tolerated. Transient signs of conjunctival hyperemia and chemosis, mild corneal opacity, and fluorescein staining of the cornea were noted and attributed to expected ocular reactions to the temporary placement of the ocular applicator and application of iontophoresis. There were no dexamethasone phosphate-, dexamethasone-, or iontophoresis-related effects on IOP, electroretinography, or histopathology. Reductions in body weight gain, anemia, decreased leukocyte and lymphocyte counts, compromised liver function, enlarged liver, and reduced spleen weight were consistent with systemic corticosteroid-mediated pharmacology, repeated use of anesthesia, stress, and sedentariness, and unlikely to be related to iontophoresis application.

CONCLUSIONS

The results of this investigation suggest that repeated transscleral iontophoresis with dexamethasone phosphate may be safe for use as a treatment for inflammatory ocular disorders that require prolonged and/or repeated corticosteroid therapy.

The activity of lowering intraocular pressure of cassiae seed extract in a DBA/2J mouse glaucoma model

PURPOSE

To evaluate the activity of lowering intraocular pressure (IOP) by Cassiae seed in the DBA/2J mouse glaucoma model.

METHODS

Young male (mean age: 3 months) inherited glaucoma mice (BDA/2J) were enrolled in this study. To evaluate the potential of Cassiae seed in the treatment of glaucoma, all subjects were divided into 6 groups. There were 1 sham group, positive control identified as group 2 topical brimonidine and group 3 oral acetazolamide, and groups 4-6 Cassiae seed extract (CSE) groups. The lactate dehydrogenase (LDH) level in the anterior aqueous humor and the changes of IOP were investigated. Contents of total polyphenol glycosides in the CSE were measured using a high-performance liquid chromatography (HPLC) method. Chromatographic separation was performed on a Cosmosil 5C(18)-MS reverse-phase HPLC column (4.6×250-mm i.d., 5 μm) with methanol/0.1% H(3)PO(4) as the mobile phases in a gradient elution mode at a flow rate of 1.0 mL/min and an injection volume of 10 μL. The wavelength of UV detector was set at 254 nm.

RESULTS

The LDH level in the anterior aqueous humor and IOP significantly decreased after treatment with CSE. The IOP-lowering effect of CSE was comparable to those of oral acetazolamide and brimonidine instillation. There were no abnormal findings in the external appearance, and body weight change after treatment with CSE for 5 weeks. Chrysophanol and physcion were measured by an HPLC method to obtain total polyphenol glycosides of the CSE, and were involved in the IOP-lowering function.

CONCLUSION

Cassiae seed may be safe and beneficial for treating glaucoma due to its significant IOP- and LDH-lowering activities.

Kappa opioid receptor localization and coupling to nitric oxide production in cells of the anterior chamber

PURPOSE

The present study was designed to determine whether kappa opioid receptors (KORs) are localized to cells of the inflow and outflow pathways of the eye and if activation of these receptors has an effect on nitric oxide (NO) production, because these effects could play a role in KOR agonist-mediated reduction of IOP.

METHODS

Human nonpigmented ciliary epithelial (NPCE) and trabecular meshwork (HTM-3) cells were treated with spiradoline (SPR), a selective KOR agonist, or estradiol, for 24 hours. Some cells were pretreated with the selective KOR antagonist norbinaltorphimine (norBNI) or the nonselective NO synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME) for 30 minutes, followed by the addition of SPR. Immunofluorescent localization of KORs was determined in isolated rabbit iris-ciliary bodies (ICBs) and NPCE and HTM-3 cells.

RESULTS

Immunohistochemical data show the localization of KORs to the rabbit ICB and more specifically to the ciliary epithelial layer. KORs were also found on cell membranes of NPCE and HTM-3 cells. Treatment of both these cell types with spiradoline caused concentration-dependent increases in the release of NO. Spiradoline-induced release of NO from both cell types was inhibited by pretreatment with norBNI and L-NAME.

CONCLUSIONS

Results from this study show the presence of KORs on rabbit ICBs and also on NPCE and HTM cells. Activation of these KORs on both cell types resulted in KOR-mediated increases in NO production. These findings provide evidence that previously demonstrated KOR-mediated reduction in IOP could be caused, in part, by NO production in both the ciliary body and the trabecular meshwork.

Enhanced oxygen saturation in optic nerve head of non-human primate eyes following the intravitreal injection of NCX 434, an innovative nitric oxide-donating glucocorticoid

PURPOSE

Hypoxia of the retina and optic nerve head (ONH) is believed to be pivotal in the development of ocular vascular disorders, including diabetic macular edema (DME). Glucocorticoids are among the most effective agents for the treatment of back of the eye diseases. However, this class of compounds is highly liable to increase intraocular pressure (IOP) and does not improve ocular perfusion or tissue oxygenation. Nitric oxide (NO) has vasodilating properties and lowers IOP in experimental models and humans, suggesting that its properties might complement those of glucocorticoids. NCX 434 is an NO-donating triamcinolone acetonide (TA) that is less likely to increase IOP while targeting both the vascular and inflammatory components of DME.

METHODS

NCX 434 was studied in vitro with respect to its NO-releasing properties in isolated methoxamine-precontracted rabbit aortic rings and glucocorticoid-like activity in recombinant human glucocorticoid receptors. IOP and oxygen saturation in the ONH and overlaying arteries and veins were studied in the anesthetized cynomolgus monkey. Measurements were taken using, respectively, an applanation tonometer and a hyperspectral imaging system before and 7, 14, 21, 31 and 41 days after the intravitreal injection of NCX 434 (5.8 mg/eye) or TA equimolar doses (4.0 mg/eye).

RESULTS

NCX 434 inhibited (3)H-dexamethasone-specific binding (IC(50)=34±5 nM) on human glucocorticoid receptors and elicited NO-dependent aortic ring relaxation (EC(50) of 0.5±0.1 μM, E(max) 98.9%). In monkey eyes, NCX 434 enhanced, whereas TA did not, oxygen saturation in various ONH areas (*P<0.05 vs. basal), decreased it in veins, and did not affect it in the overlaying arteries. Neither NCX 434 nor TA altered IOP significantly at all time points. However, at 31 days post-treatment TA appeared to start increasing IOP (Δ(IOP)=+3.31±0.51 mmHg, 30.8%, over baseline, NS).

CONCLUSIONS

NCX 434 enhances ocular tissue oxygenation. This feature appears to depend on its NO-donating properties; thus, the compound deserves to be further investigated for the treatment of DME and other ocular disorders with impaired ocular perfusion.