Rat Eyes Research Articles

Chemical proteasome inhibition as a novel animal model of inner retinal degeneration in rats.

Chemical proteasome inhibition has been a valuable animal model of neurodegeneration to uncover roles for the ubiquitin-proteasome system in the central nervous system. However, little is known about the effects of chemical proteasome inhibitors on retinal integrity. Therefore, we characterized the effects of structurally different chemical proteasome inhibitors on the retinal morphology and the mechanisms of their action in the normal adult rat eyes. Intravitreal injection of MG-262 and other proteasome inhibitors led to inner retinal degeneration. MG-262-induced inner retinal degeneration was accompanied by reduced proteasome activity, increased poly-ubiquitinated protein levels, and increased positive immunostaining of ubiquitin, 20S proteasome subunit and GADD153/CHOP in the retina. Its retinal degenerative effect was also associated with reduced retinal neurofilament light chain gene expression, reflecting retinal ganglion cell death. MG-262-induced neurofilament light chain downregulation was largely resistant to pharmacological modulation including endoplasmic reticulum stress, apoptosis or MAP kinase inhibitors. Thus, this study provides further evidence of roles for the ubiquitin-proteasome system in the maintenance of the retinal structural integrity. Chemical proteasome inhibition may be used as a novel animal model of inner retinal degeneration, including retinal ganglion cell loss, which warrants further analysis of the molecular mechanisms underlying its retinal degenerative effect.

Evaluation of acute corneal damage induced by 222-nm and 254-nm ultraviolet light in Sprague–Dawley rats

Two hundred twenty-two nanometres ultraviolet (UV) light produced by a krypton–chlorine excimer lamp is harmful to bacterial cells but not skin. However, the effects of 222-nm UV light exposure to the eye are not fully known. We evaluated acute corneal damage induced by 222- and 254-nm UV light in albino rats. Under deep anaesthesia, 6-week-old Sprague–Dawley albino rats were exposed to UV light. The exposure levels of corneal radiation were 30, 150, and 600 mJ/cm2. Epithelial defects were detected by staining with fluorescein. Superficial punctate keratitis developed in corneas exposed to more than 150 mJ/cm2 of UV light, and erosion was observed in corneas exposed to 600 mJ/cm2 of UV light. Haematoxylin and eosin staining also showed corneal epithelial defects in eyes exposed to 254-nm UV light. However, no damage developed in corneas exposed to 222-nm UV light. Cyclobutane pyrimidine dimer-positive cells were observed only in normal corneas and those exposed to 254-nm UV light. Although some epithelial cells were stained weakly in normal corneas, squamous epithelial cells were stained moderately, and the epithelial layer that was detached from the cornea exposed to 600 mJ/cm2 of light was stained intensely in corneas exposed to 254-nm UV light. In the current study, no corneal damage was induced by 222-nm UV light, which suggested that 222-nm UV light may not harm rat eyes within the energy range and may be useful for sterilising or preventing infection in the future.

Ocular biocompatibility of dexamethasone acetate loaded poly(ɛ-caprolactone) nanofibers

Electrospinning technique has been explored to produce nanofibers incorporated with drugs as alternative drug delivery systems for therapeutic purposes in various organs and tissues. Before such systems could potentially be used, their biocompatibility must be evaluated. In this study, dexamethasone acetate-loaded poly(ɛ-caprolactone) nanofibers (DX PCL nanofibers) were developed for targeted delivery in the vitreous cavity in the treatment of retinal diseases. Ocular biocompatibility was tested in vitro and in vivo. DX PCL nanofibers were characterized by scanning electron microscopy (SEM) and Fourier Transform InfraRed spectroscopy (FTIR) and the in vitro drug release from nanofibers was evaluated. The in vitro biocompatibility of DX PCL nanofibers was tested on both ARPE-19 and MIO-M1 cells using the cytotoxicity (MTT) test by morphological studies based on staining of the actin fibers in ARPE-19 cells and GFAP in MIO-M1 cells. The in vivo biocompatibility of DX PCL nanofibers was investigated after intravitreous injection in the rat eye, using spectral domain Optical Coherence Tomography (OCT) imaging of the retina. SEM results indicated that nanometric fibers were interconnected in a complex network, and that they were composed of polymer. FTIR showed that polymer and drug did not chemically interact after the application of the electrospinning technique. PCL nanofibers provided controlled DX release for 10 days. DX PCL nanofibers were not cytotoxic to the ocular cells, allowing for the preservation of actin fibers and GFAP in the cytoplasm of ARPE-19 and MIO-M1 cells, respectively, which are biomarkers of these ocular cell populations. DX PCL nanofibers did not affect the retinal and choroidal structures, and they did not induce abnormalities, hemorrhages, or retinal detachment, suggesting that the nanofibers were well tolerated. In eyes receiving DX PCL nanofibers, SD-OCT images were corroborated with histological analysis of neuroretina and choroid, which are ocular tissues that are extremely sensitive to toxic agents. Finally, the preservation of cone and rod photoreceptors indicated the light sensitivity of the animals. In conclusion, DX PCL nanofibers exhibited ocular biocompatibility and safety in the rodent eye and allow the release of dexamethasone. Further studies are required to appreciate the potential of these new drug delivery systems for the treatment of retinal diseases.

Lentiviral Vector-Mediated Expression of Exoenzyme C3 Transferase Lowers Intraocular Pressure in Monkeys.

Primary open-angle glaucoma (POAG) is considered a lifelong disease characterized by optic nerve deterioration and visual field damage. Although the disease progression can usually be controlled by lowering the intraocular pressure (IOP), therapeutic effects of current approaches do not last long. Gene therapy could be a promising method for persistent treatment of the disease. Our previous study demonstrated that gene transfer of exoenzyme C3 transferase (C3) to the trabecular meshwork (TM) to inhibit Rho GTPase (Rho), the upstream signal molecule of Rho-associated kinase (ROCK), resulted in lowered IOP in normal rodent eyes. In the present study, we show that the lentiviral vector (LV)-mediated C3 expression inactivates RhoA in human TM cells by ADP ribosylation, resulting indisruption of the actin cytoskeleton and altered cell morphology. In addition, intracameral delivery of the C3 vector to monkey eyes leads to persistently lowered IOP without obvious signs of inflammation. This is the first report of using a vector to transduce the TM of an alive non-human primate with a gene that alters cellular machinery and physiology. Our results in non-human primates support that LV-mediated C3 expression in the TM may have therapeutic potential forglaucoma, the leading cause of irreversible blindness in humans.

Development and characterization of a new rat ocular hypertension model induced by intracameral injection of conjunctival fibroblasts

Glaucoma is a chronic optic neuropathy that leads to visual field loss. Elucidating the mechanisms underlying glaucoma is essential for developing new treatments, such as neuroprotective drugs. Various glaucoma models based on the induction of intraocular pressure (IOP) elevation have been established for use in glaucoma studies. However, the time-dependent pathological changes accompanying IOP elevation have not been fully elucidated. In this study, rat conjunctival fibroblasts were injected into the anterior chamber of rat eyes, and IOP elevation was induced for 28 days. Glaucomatous signs such as optic nerve head cupping, retinal thinning, glial activation and apoptotic signaling in the retina were obvious in the cell-injected eyes on the 14th day after injection. The pattern of retinal ganglion cell (RGC) loss differed by the magnitude of IOP elevation. The number of RGCs decreased by 37.5% in eyes with IOP lower than 50 mmHg (Under-50) and by 88.0% in those with IOP higher than 50 mmHg (Over-50) 28 days after cell injection. The RGC counts were correlated with IOP in the Under-50 group but not in the Over-50 group. Our model may contribute to the investigation of pathogenic mechanisms of glaucoma and the development of new glaucoma treatments.

Biodegradable Thermosensitive PLGA-PEG-PLGA Polymer for Non-irritating and Sustained Ophthalmic Drug Delivery.

Challenges of ophthalmic drug delivery arise from not only the limited solubility of hydrophobic therapeutics, but also the restricted permeability and fast clearance of drugs due to the complex anatomy and physiology of the eyes. Biodegradable thermosensitive polymer, poly(dl-lactide-co-glycolide-b-ethylene glycol-b-dl-lactide-co-glycolide) (PLGA-PEG-PLGA) is a desirable ophthalmic drug delivery system because it can be formulated into injectable solution which forms gel in situ to provide prolonged drug release. In this study, excellent biocompatibility of blank PLGA-PEG-PLGA (1800-1500-1800) thermogel was demonstrated with insignificant difference from saline noted in rat eye enucleation test, in vivo inflammation test upon topical instillation, and subconjunctival injection. After subconjunctival injection, thermogel formulations loaded with hydrophilic (rhodamine B) or hydrophobic (coumarin 6) fluorescent dyes were retained up to 4weeks in eye tissues and significantly higher level was detected than rhodamine B solution or coumarin 6 suspension in weeks 3 and 4. Moreover, in vivo whole body imaging showed that dye-loaded (sulfo-cyanine 7 NHS ester, Cy7; or cyanine 7.5 alkyne, Cy7.5) thermogels had longer retention at the injection site and retarded release to other body parts than dye solutions. Generally, the release rate of hydrophobic dyes (coumarin 6 and Cy7.5) was much slower than that of the hydrophilic dyes (rhodamine B and Cy7) from the thermogel. In summary, the thermogel was safe for ophthalmic drug delivery and could deliver both hydrophobic and hydrophilic compounds for sustained drug release into eye tissues with single subconjunctival injection for better patient compliance and reduced risks on repeated injection.

Prospective insulin-based ophthalmic delivery systems for the treatment of dry eye syndrome and corneal injuries

The presence of insulin (INS) receptors on the ocular surface (OS) and lacrimal gland (LG), and the high prevalence of dry eye syndrome (DES) and corneal lesions in diabetic patients suggest that INS is relevant for OS homeostasis and wound healing. The study aims at developing delivery systems for the topical administration of INS to the OS in order to improve INS local bioavailability and evaluate the influence of the delivery systems on DES in diabetic rats (DM) (n = 05/group). Chitosan microparticles (MP), chitosan/poloxamer gel (GEL) and MP-loaded GEL (GELMP), with or without INS were developed. Formulations were instilled into the eyes of diabetic rats (DM) for 15 days and the tear fluid volume, corneal cells morphology and cornea thickness were assessed and compared with an aqueous dispersion of INS (DISP-INS). All delivery systems had pH of about 6, osmolality suitable for topical application and positive zeta potential. The MPs with or without INS had sizes close to 4 μm, spherical morphology and INS encapsulation efficiency of 77 ± 6%. DISP-INS and GELMP-INS formulations produced tear secretion amounts significantly higher than those receiving formulations containing no INS and similar to healthy animals. Cornea surface impression cytology showed that treatment with INS-delivery systems and not DISP-INS almost normalized cells morphology. Treatment with GELMP-INS increased INS by 2.5 in the LG and eyeball as compared to the groups treated with GEL-INS and MP-INS, while treatment with DISP-INS left no traces of drug in the eye after treatment termination. GEL and GELMP containing INS were also able to normalize the thickness of the corneal epithelia. In conclusion, GELMP-INS normalized tear fluid volume, corneal thickness, protected corneal cells morphology and increased ocular bioavailability of INS, making it a promising treatment strategy for DES and corneal lesions.

The Presence of Fat Droplets in the Retina of Rats in a Model of Fat Embolism

IntroductionFat embolism (FE) induced in rats by intravenous injection (IV) of the neutral fat triolein (T) results in the deposition of intrapulmonary lipid associated with septal and arterial inflammation. In humans, FE may also contribute to retinopathy. This study's goal is to determine the presence of fat droplets in the retina in our rat model at a time when pulmonary fat is known to accumulate.Material and MethodsSprague‐Dawley rats (250–300g) were injected with 0.2 ml of T (N=13) in the caudal vein; controls received injection of saline (N=13). 48 hours later, rats were euthanized using decapitation under isoflurane anesthesia. Lungs were dissected, frozen immediately and stored for histological analysis. Eyes were dissected and incubated in PBS at 4°C for two hours. The retinas were isolated, flattened into optimal cutting temperature (OCT) compound by making four peripheral incisions at 90° intervals, and frozen immediately in isopentane equilibrated to −80°C. Cryosections of five representative experimental and control samples were stained with Oil Red O to detect fat. Three independent samples from each animal were stained. Two pathologists blinded to the identity of the samples analyzed the samples for presence of Oil Red O‐positive fat droplets.ResultsForty‐eight hours after T injection, all experimental animals exhibited large lipid droplets in the outer retina, indicated by the deep red Oil Red O staining. Lipid droplets were absent in retinas of saline injected controls. The lipid droplets typically span the outer segments, outer nuclear, and outer plexiform layers with some extending through the inner nuclear layer and into the inner plexiform layer. No lipid droplets observed in the inner retina or extending into the retinal ganglion cell layer. T‐treated rats also had the expected large fat droplets in the lungs, mostly in the alveoli with an inflammatory response in the parenchyma; while the saline treated animals showed only a small number of droplets.ConclusionsFat droplets were observed within the eyes in T‐injected rats at 48 hours following injection and were predominantly located within the outer retina. As previously described, the lungs has significant accumulation of fat droplets. This animal model could serve as a novel model for studying retinopathy subsequent to fat embolism in human patients. Future studies should include longitudinal analyses of fat embolism in the retina and resulting structural damage and functional impairment at different post injection intervals. It is proposed that the underlying pathogenesis may involve alterations in the renin‐angiotensin system as suggested for the lung.Support or Funding InformationSupported by the Catherine T Geldmacher foundation, Saint Louis, MO.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

In Situ Cross-linking Hydrogel as a Vehicle for Retinal Progenitor Cell Transplantation

One of the current limitations of retinal transplantation of stem cells as well as other cell types is the dispersion of cells from the injection site (including loss of cells into the vitreous chamber) and low survival after transplantation. Gelatin-hydroxyphenyl propionic acid (Gtn-HPA) conjugate is a biodegradable polymer that can undergo covalent cross-linking in situ, allowing for injection of incorporated cells through a small caliber needle followed by gel formation in vivo. We tested the hypothesis that Gtn-HPA hydrogel supports survival and integration of retinal progenitor cells (RPCs) post-transplantation. In vitro compatibility and in vivo graft survival were assessed by mixing an equal volume of Gtn-HPA conjugate and RPC suspension and triggering enzyme-mediated gelation, using minute amounts of horseradish peroxidase and peroxide. Immunocytochemistry showed >80% survival of cells and minimal apoptosis for cells incorporated into Gtn-HPA, equivalent to controls grown on fibronectin-coated flasks. RPCs undergoing mitosis were seen within the three-dimensional Gtn-HPA hydrogel, but the percentage of Ki-67-positive cells was lower compared with the monolayer controls. For in vivo studies, gel–cell mixture or cell suspension in saline was trans-sclerally injected into the left eye of female Long Evans rats immunosuppressed with cyclosporine A. Grafts survived at the 1 week time point of the study, with Gtn-HPA-delivered grafts showing less inflammatory response demonstrated by anti-leukocyte staining. More eyes in the gel–cell mixture group showed surviving cells in the subretinal space compared with saline-delivered controls, while the number of cells surviving per graft was not significantly different between the two groups. This work demonstrates an injectable in situ cross-linking hydrogel as a potential vehicle for stem cell delivery in the retina.

Fenofibrate-Loaded Biodegradable Nanoparticles for the Treatment of Experimental Diabetic Retinopathy and Neovascular Age-Related Macular Degeneration.

Fenofibrate is a peroxisome proliferator-activated receptor α (PPARα) agonist and has been shown to have therapeutic effects on diabetic retinopathy (DR). However, the effects of fenofibrate through systemic administration are not as potent as desired due to inefficient drug delivery to the retina. The present study aimed to explore the sustained therapeutic effects of fenofibrate-loaded biodegradable nanoparticles (NP) on both DR and neovascular age-related macular degeneration (AMD). Fenofibrate was successfully encapsulated into poly(lactic- co-glycolic acid) (PLGA) NP (Feno-NP), and Feno-NP were optimized by varying polymer composition to achieve high drug loading and prolonged drug release. The Feno-NP made of PLGA 34 kDa demonstrated a drug content of 6% w/w and a sustained drug release up to 60 days in vitro. Feno-NP (PLGA 34 kDa) was selected for following in vivo studies, and one single intravitreal (IVT) injection of Feno-NP into rat eyes with a 30G fine needle maintained sustained fenofibric acid drug level in the eye for more than 60 days. The efficacy of Feno-NP in DR and neovascular AMD was investigated using streptozotocin (STZ)-induced diabetic rats, laser-induced choroidal neovascularization (CNV) rats, and very low-density lipoprotein receptor knockout ( Vldlr -/-) mice. Therapeutic effects of Feno-NP were evaluated by measuring electroretinogram (ERG), retinal vascular leakage, leukostasis, CNV size, and retinal levels of vascular endothelial growth factor (VEGF) and intracellular adhesion molecule-1 (ICAM-1). In diabetic rats, Feno-NP ameliorated retinal dysfunctions, reduced retinal vascular leakage, inhibited retinal leukostasis, and downregulated the overexpression of VEGF and ICAM-1 at 8 weeks after one IVT injection. In addition, Feno-NP reduced retinal vascular leakage and CNV formation in both CNV rats and Vldlr -/- mice. Moreover, no toxicity of Feno-NP or Blank-NP to retinal structure and function was detected. Feno-NP exhibited good physiochemical characteristics and controlled drug release profile, conferring prolonged beneficial effects on DR and neovascular AMD.

Effect of taxifolin on development of retinopathy in alloxan-induced diabetic rats

Purpose: Diabetic retinopathy (DR) is one of the leading causes of blindness. In DR patients, antioxidant defence is disrupted, and production of reactive oxygen species and pro-inflammatory cytokines such as interleukin 1β (IL-1β) and tumour necrosis factor alpha (TNF-α) increases. Taxifolin has been reported to suppress reactive oxygen species, IL-1β and TNF-α production. The aim of this study is to biochemically and histopathologically examine the protective effect of taxifolin against DR damage induced by alloxan.Materials and methods: Alloxan received rats with a blood glucose level of ≥250 mg/dL were divided into taxifolin-treated (TAX) (n = 6), diabetic control (DC) (n = 6) groups. There were rats received only saline in non-diabetic control (NC) group (n = 6). Taxifolin (50 mg/kg) was orally administered to the TAX group rats. DC and NC rats received the same volume of saline as a solvent. This procedure was repeated once a day for 3 months. At the end of this period, animals were killed by high dose thiopental sodium anaesthesia. Histopathological examinations were then performed on excised rat eyes. Malondialdehyde (MDA), total glutathione (tGSH), IL-1β and TNF-α levels were measured in obtained blood samples.Results: MDA, IL-1β and TNF-α levels were significantly increased in blood samples of DC group rats with hyperglycemia induced by alloxan compared with NC group (p < 0.0001), and decreased in the TAX group compared with the DC group (p < 0.0001). The levels of tGSH were significantly decreased in blood samples of DC group rats compared with NC group (p < 0.0001), and increased in the TAX group compared with the DC group (p < 0.0001). Histopathologically, retinal ganglion cells of the TAX group had a slightly dilated and congested blood vessel, and severe damage was inflicted to the retinal ganglion cell layer of the DC group.Conclusions: Experimental results suggest that taxifolin may be beneficial in the treatment of DR.

Optimization by design of etoposide loaded solid lipid nanoparticles for ocular delivery: Characterization, pharmacokinetic and deposition study

The present study was to develop etoposide loaded solid lipid nanoparticles (SLN) and optimize it for effective ocular delivery to the posterior eye. SLN were prepared by melt-emulsification and ultrasonication technique. Etoposide loaded SLN were optimized by using three-factor three levels Box-Behnken design to establish the functional relationships between variables on responses of particle size, polydispersity index (PDI) and entrapment efficiency (EE). SLN were characterized for size & surface morphology, entrapment efficiency and in vitro release. Further the pharmacokinetic study of optimized formulation after intravitreal administration was evaluated in Wister rats. The deposition in the ocular tissues was checked by scintigraphic analysis in Albino rabbits. Histology was also done to evaluate morphological changes if any occur after treatment. The particle size, PDI and EE obtained for the optimized formulation (Z15) were 239.43 ± 2.35 nm, 0.261 ± 0.001 and 80.96 ± 2.21% respectively. Single intravitreal administrations of SLN were able to give sustained etoposide concentration in the vitreous for 7 consecutive days which was also supported by the results of Gamma scintigraphic study. Histology of posterior ocular tissues do not showed any serious toxic effect. Therefore it can concluded that etoposide loaded SLN was able to maintain vitreous concentration of drug without any serious toxic effect to the surrounding ocular tissues after an intravitreous administration in rat eye.

Neuroprotective effects of topical coenzyme Q10 + vitamin E in mechanic optic nerve injury model.

We aimed to create mechanic optic nerve injury model in rats and investigate the neuroprotective effects of topical Coenzyme Q10 + Vitamin E (CoQ + Vit.E) molecules on retinal ganglion cells. Mechanic optic nerve injury model was created in the right eyes of rats (n = 12). Rats were divided into two groups: glaucoma model with sham treatment and topical CoQ + Vit.E treatment. Treatment was applied for 4 weeks. Glial fibrillary acidic protein, Brn-3a antibody, and anti-Iba1 were examined by immunohistochemistry. Glial fibrillary acidic protein, Bax, Bcl-xL, and Tfam protein expression were measured by Western blot analysis. The number of Brn-3a-positive retinal ganglion cell was 15.0 ± 1.0 (min: 14, max: 16) in sham treatment group and 22.2 ± 4.8 (min: 18, max: 29) in topical CoQ10 + Vit.E treatment group. The protection of Brn-3a in CoQ10 + Vit.E was statistically significant (p < 0.05). Glial fibrillary acidic protein-positive astroglial counts were recorded as 11.7 ± 2.1 (min: 10, max: 14) in sham treatment and 2.5 ± 1.5 (min: 1, max: 4) in topical CoQ10 + Vit.E treatment group (p < 0.05). Topical CoQ10 + Vit.E treatment also decreased Iba1 expression in the retina of mechanic optic nerve injury groups. CoQ10 + Vit.E treatment prevented apoptotic cell death by increasing Bcl-xL protein expression. Also, CoQ10 + Vit.E preserved Tfam protein expression in the retina. This study has shown that in glaucoma treatment the neuron protecting effect of topical CoQ10 + Vit.E molecules can be valuable.

Dan Huang Ming Mu Recipe Suppresses the Progression of Streptozotocin-induced Diabetic Retinopathy After Retinal Laser Photocoagulation in Brown Norway Rats via Down-regulating Vascular Endothelial Growth Factor and Up-regulating Pigment Epithelium-derived Factor

ObjectiveTo analyze the effects of Dan Huang Ming Mu Recipe (DHMMR) (a pharmaceutical preparation from herbs and having the function of replenishing vital essence, removing heat, promoting blood circulation and excreting pathogenic water) on diabetic retinopathy (DR) after retinal laser photocoagulation through regulating the expression of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). MethodsForty male Brown Norway (BN) rats were randomly divided into blank group (group A, 10 BN rats) and model group (30 BN rats). DR models were induced by 40 mg/kg streptozotocin (STZ) and the body weight and blood glucose of rats were monitored. After 12-week injection, fluorescein fundus angiography (FFA) and histopathological examination were detected to confirm the successful establishment of DR models. Subsequently, the right eyes of model group rats were conducted retinal laser photocoagulation with the left eyes having no retinal laser photocoagulation and rats of the model group were randomly divided into group B (the model control group), group C (the positive control group), and group D (the DHMMR group), with 10 rats in each group. Rats of the group A and the group B were given vehicle, and the group C were given calcium dobesilate suspension by gavage, and the group D were given DHMMR by gavage. After 4-week gavage, FFA was carried out to observe the fundus microvascular change. Then, the rats were sacrificed to do histopathological examinations and the serum levels of P-selectin, cAMP, cGMP, and the relative expression of the protein of VEGF and PEDF in retina were detected. ResultsAfter 12-week STZ injection, the blood glucose of the model group were pronouncedly higher than the blank group (P < 0.01). Fundus micro-hemangioma changes were observed in the rats of the model group through FFA, and the rats of the blank group did not see any changes. The pictures of HE staining showed that the retinal structure of the model group was more disordered than the blank group. After 4-week gavage, treatments with DHMMR showed dramatic reduction of serum levels of P- selectin, cAMP and cGMP compared with the group B (P < 0.01). FFA and histopathological examinations of DHMMR-treated rats revealed significantly suppression of retinal edema, fundus microvascular destruction and retinal destruction distinguishing from the group B. And the relative expression of VEGF protein of the group D and the group A was markedly lower than that of the group B (P < 0.01). The relative expression of PEDF protein of the group D and the group A was dramatically higher than that of the group B to the contrary (P < 0.01). ConclusionsDHMMR demonstrates pronounced suppressive effects on the progression of DR after retinal laser photocoagulation, through down-regulating VEGF and up- regulating PEDF.

Corosolic acid: antiangiogenic activity and safety of intravitreal injection in rats eyes.

Investigate the potential application of corosolic acid (CA) in the treatment of diseases causing retinal neovascularization. CA cytotoxicity effect was evaluated in ARPE-19 cells by sulforhodamine B colorimetric method, and antiangiogenic activity was studied using chorioallantoic membrane (CAM) assay. An amount of 0.01mL of CA formulations at 5, 10 and 25µM was injected in the right eyes of Wistar rats, and the contralateral eyes received the vehicle to verify the safety of ophthalmic use. Electroretinography (ERG) was performed before, 7 and 15days after CA administration. Animals were killed on the 15th day, and the histological analysis of retina was carried out under light microscopy. CA did not present cytotoxicity at concentrations below 35.5μM after 48h of treatment. The antiangiogenic activity was confirmed by CAM assay, since CA (range from 5 to 25µM) induced a significant reduction in vascularity without any signs of toxicity. ERG recordings and histological evaluation did not show any signs of retinal toxicity. CA was effective in reducing vascularity in a CAM model and was found to be safe for potential ophthalmic use.

Apricot Kernel Extract and Amygdalin Inhibit Urban Particulate Matter-Induced Keratoconjunctivitis Sicca.

Exposure to particulate matter is a risk factor for various ocular surface diseases, including keratoconjunctivitis sicca (KCS). In this study, we investigated the protective effects of apricot kernel extract (AKE) and its bioactive compound, amygdalin, on KCS induced by exposure to urban particulate matter (UPM). In the in vivo experiments, eye drops containing 0.5 mg/mL AKE (AKE-0.5) or 1 mg/mL AKE (AKE-1) were administered directly into the eyes of female rats after UPM exposure. Additionally, the effect of AKE and amygdalin on matrix metalloproteinases (MMPs) activity and the expressions of inflammatory factors, including tumor necrosis factor (TNF)-α and interleukin (IL)-6, was investigated in conjunctival epithelial cells in vitro. Topical administration of AKE-1 attenuated UPM exposure-induced reduction of tear secretion. Both AKE-0.5 and AKE-1 inhibited UPM exposure-induced corneal epithelial damage and irregularity. AKE also protected against UPM exposure-induced disruption of the mucin-4 layer on the ocular surface. In addition, AKE and amygdalin prevented UPM-induced activation of MMPs and upregulation of TNF-α and IL-6 in conjunctival epithelial cells. Therefore, AKE may have protective effects against UPM exposure-induced KCS via the inhibition of MMPs and inflammation. The pharmacological activities of AKE may be in part due to its bioactive compound, amygdalin.

The In Vivo Evaluation on Total Components from Extract of Aconitum Based on a New Analytic Method of Area under Absorbance-Wavelength Curve

Objective. To study oral pharmacokinetics of Aconitum extract in randomized Sprague-Dawley (SD) rats and observe the profile change in vivo between plasma concentration and time with an aim to disclose relevant delivery rule for total components from Aconitum extract and finally to evaluate the research of Aconitum sustained-release preparation. Methods. Randomized rats were administered orally with the single and multiple dose of Aconitum extract based on the clinical use of Aconitum injection. Blood samples were collected at predetermined interval time from an eye of rats. The concentration of total components in those samples was determined by a new analytic method of area under absorbance-wavelength curve, the data were analyzed by Drug and Statistics software, and then the pharmacokinetic parameters and compartment model were acquired and compared, respectively. Results. The pharmacokinetic parameters of single and multiple doses were similar, and both of them showed characteristics of the one-compartment model. Cav, DF, and AUCss were (2.075 ± 0.282) µg/ml, (2.405 ± 0.175), and (24.901 ± 0.422) µg/ml/h, respectively. However, the concentrations of total components in the fifth and sixth day were 0.32 and 0.44 µg/ml, which were lower than the value of Cav. Conclusion. The method of AUAWC is feasible for the pharmacokinetics study in vivo analysis on total components of Aconitum with good sensitivity, specificity, and repeatability. The results demonstrated that both absorption and elimination of total components from Aconitum extract in rats were rapid and pharmacokinetic behavior was consistent at the level of single and multiple doses, which confirms that Aconitum injection is available to transform the oral sustained-release preparation. This will bring a good instruction to the research of sustained-release preparation of traditional Chinese medicine (TCM), which still lacks of an evaluation method available for total components in vivo analysis.

Solid lipid nanoparticles for ocular delivery of isoniazid: evaluation, proof of concept and in vivo safety & kinetics.

Evaluation of solid lipid nanoparticles (SLNs) for ocular delivery of isoniazid (INH). INH-SLNs were characterized for morphological, thermal, crystalline and nuclear magnetic resonance properties. In vitro release and ex vivo corneal permeability of INH-SLNs was also evaluated. Proof-of-concept uptake studies were performed in corneal and conjunctival cell lines and in vivo in rat eye using fluorescein-labeled SLNs. Antimycobacterial activity of INH-SLNs was confirmed. In vivo aqueous humor pharmacokinetics, toxicity and tolerance was performed in rabbit/rat eye. INH-SLNs showed extended release (48h), enhanced corneal permeability (1.6-times), five-times lower MIC, significant in vitro and in vivo uptake of fluorescein-labeled SLNs, 4.2-times ocular bioavailability (area under the curve) and in vivo acute and repeat dose safety. INH-SLNs are an effective ocular delivery system.

Efficacy and safety of a novel naltrexone treatment for dry eye in type 1 diabetes

BackgroundDry eye disease (DED) is a prevalent complication of diabetes and presents as reduced tear production and/or increased corneal surface sensitivity often with secondary ocular surface changes. This study examined the safety and efficacy of a proprietary new eye drop formulation for topical treatment of DED.MethodsType 1 diabetes (T1D) was established in male Sprague-Dawley rats to study the efficacy and safety of the investigational compound that contained 20 μg/ml of naltrexone (NTX). Tear production was measured by the Schirmer’s 1 test, and ocular surface sensitivity was measured using an aesthesiometer. Diabetic rats received twice daily applications of a single drop (~ 0.02 ml) of the proprietary formulation (NTX-001) or vehicle onto one eye. For comparison, some diabetic rats received eye drops containing NTX in sterile Vigamox®. Safety was monitored by assessment of ocular histopathology in naïve male rats and naïve male rabbits receiving twice daily treatment of two drops for 30 days.ResultsDry eye in T1D rats was reversed within hours of a single treatment of NTX-001, and over a period of 10 days NTX-001 restored corneal sensitivity and reversed dry eye relative to values measured in diabetic rats receiving vehicle. In comparison to NTX dissolved in Vigamox®, the proprietary NTX-001 was more effective at reversing dry eye. Safety studies in naïve rats and rabbits revealed no visible ocular pathology after 30 days of treatment.ConclusionsAn investigational new eye drop containing 20 μg/ml NTX effectively reversed tear film deficits and restored corneal surface sensitivity in diabetic animals without causing toxic side effects.

An Investigation into Retigabine (Ezogabine) Associated Dyspigmentation in Rat Eyes by MALDI Imaging Mass Spectrometry.

Retigabine (RTG) is an antiepileptic drug approved as an adjunctive treatment for refractory partial-onset seizures in adults. In April 2013, the Food and Drug Administration issued a warning that RTG could cause changes in retinal pigmentation and discoloration of skin, resulting in a blue appearance. As part of a larger preclinical effort to gain a mechanistic understanding as to the origins of retinal pigment changes associated with RTG, we conducted a long-term repeat dosing study in rats. Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) was used to determine the distribution of RTG and its metabolites in the rat eye following 13 and 39 weeks of dosing. IMS revealed the presence of RTG, a previously characterized N-acetyl metabolite of RTG (NAMR), and several species structurally related through the dimerization of RTG and NAMR. These species were highly localized to the melanin-containing layers of the uveal tract of the rat eye including the choroid, ciliary body, and iris, suggesting that the formation of these dimers occurs from melanin bound RTG and NAMR. Furthermore, several of the RTG-related dimers have UV absorbance which give them a purple color in solution. We propose that the melanin binding of RTG and NAMR effectively concentrates the two compounds to enable mixed condensation reactions to occur when the binding provides the proper geometry in the redox environment of the uveal tissues. High lateral resolution images illustrate that the blood-retinal barrier effectively restricts retinal access to RTG-related compounds. The spatial information provided by MALDI IMS was critical in contextualizing the homogenate concentrations of key RTG-related compounds and helped provide a basis for the mechanism of dimer formation.