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 34kDa demonstrated a drug content of 6% w/w and a sustained drug release up to 60 days in vitro. Feno-NP (PLGA 34kDa) 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
PurposeClinical studies have shown that peroxisome proliferator-activated receptor alpha (PPARα) agonist fenofibrate has therapeutic effects on diabetic retinopathy (DR). The purpose of this study was to identify a novel PPARα agonist and to evaluate its beneficial effects on DR.MethodsThe transcriptional activity of PPARα was measured by a luciferase-based promoter assay. TUNEL was used to evaluate apoptosis in retinal precursor cells (R28). Diabetes was induced in rats by injection of streptozotocin. Retinal inflammation was examined using leukostasis assay, and retinal vascular leakage was measured using permeability assay. Retinal function was measured using electroretinogram (ERG) recording, and retinal apoptosis was quantified using the cell death ELISA. The anti-angiogenic effect was evaluated in the oxygen-induced retinopathy (OIR) model.ResultsA compound, 7-chloro-8-methyl-2-phenylquinoline-4-carboxylic acid (Y-0452), with a chemical structure distinct from existing PPARα agonists, activated PPARα transcriptional activity and upregulated PPARα expression. Y-0452 significantly inhibited human retinal capillary endothelial cell migration and tube formation. The compound also protected R28 cells against apoptosis and inhibited NF-κB signaling in R28 cells exposed to palmitate. In diabetic rats, Y-0452 ameliorated leukostasis and vascular leakage in the retina. In addition, Y-0452 preserved the retinal function and reduced retinal cell death in diabetic rats. Y-0452 also alleviated retinal neovascularization in the OIR model.ConclusionsY-0452 is a novel PPARα agonist and has therapeutic potential for DR.
The aim of this study was to investigate the effects of Avastin on aquaporin4 (AQP4) expression in human retinal Müller cells in vitro under hypoxia, so as to explore the mechanism of Avastin treating retinal edema. The human Müller cells were cultured using the enzymatic digestion method. Müller cells were identified under the transmission electron microscopy and by using immunofluorescence staining. By using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), the expression of AQP4 mRNA and VEGF mRNA in Müller cells cultured with 500 μmol/L CoCl(2) for 0, 3, 6, 12 and 24 h, and with 0, 100, 300, 500 and 700 μmol/L CoCl(2) for 24 h was detected. The expression of AQP4 mRNA in Müller cells cultured with 50 ng/mL exogenous vascular endothelial growth factor (VEGF) for 0, 0.5, 1, 2 and 4 h, and with 0, 25, 50 and 75 ng/mL VEGF for 24 h was detected. Amplified cDNA products of AQP4 mRNA in Müller cells cultured with 500 μmol/L CoCl(2) and 200 μg/mL Avastin for 24 h were detected. The results showed that more than 95% cells displayed positive immunofluorescence reaction. Characteristic 8-10 nm intracellular filaments could be seen in the cytoplasm under the transmission electron microscopy. In the CoCl(2) experimental groups, the expression of AQP4 mRNA and VEGF mRNA in Müller cells was increased as compared with the control group. Alteration of AQP4 mRNA and VEGF mRNA levels showed a significantly positive correlation (r (2)=0.822, P<0.05). The expression of AQP4 mRNA in Müller cells was increased by VEGF. The expression of AQP4 mRNA was significantly decreased by Avastin as compared with the control group. It is suggested that Avastin can decrease the expression of AQP4 mRNA in human Müller cells under chemical hypoxic conditions partially via VEGF path, which may be one of the mechanisms of Avastin treating retinal edema.
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