geranylgeranylacetone and Retinal-Diseases

Retinal ischemia-reperfusion (I/R) injury is a common pathophysiological stress state connected to various diseases, including acute glaucoma, retinal vascular obstruction, and diabetic retinopathy. Recent studies have suggested that geranylgeranylacetone (GGA) could increase heat shock protein70 (HSP70) level and reduce retinal ganglion cells (RGCs) apoptosis in a rat retinal I/R model. However, the underlying mechanism remains unclear. Moreover, the injury caused by retinal I/R includes not only apoptosis but also autophagy and gliosis, and the effects of GGA on autophagy and gliosis have not been reported. Our study established a retinal I/R model by anterior chamber perfusion pressuring to 110 mmHg for 60 min, followed by 4 h of reperfusion. The levels of HSP70, apoptosis-related proteins, GFAP, LC3-II, and PI3K/AKT/mTOR signaling proteins were determined by western blotting and qPCR after treatment with GGA, HSP70 inhibitor quercetin (Q), PI3K inhibitor LY294002, and mTOR inhibitor rapamycin. Apoptosis was evaluated by TUNEL staining, meanwhile, HSP70 and LC3 were detected by immunofluorescence. Our results demonstrated that GGA-induced HSP70 expression significantly reduced gliosis, autophagosome accumulation, and apoptosis in retinal I/R injury, indicating that GGA exerted protective effects on retinal I/R injury. Moreover, the protective effects of GGA mechanistically relied on the activation of PI3K/AKT/mTOR signaling. In conclusion, GGA-induced HSP70 overexpression has protective effects on retinal I/R injury by activating PI3K/AKT/mTOR signaling.

Topics: Animals; Apoptosis; Gliosis; Heat-Shock Response; HSP70 Heat-Shock Proteins; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Reperfusion Injury; Retinal Diseases; TOR Serine-Threonine Kinases

We evaluated the effects of a transscleral drug delivery device, consisting of a reservoir and controlled-release cover, which were made of photopolymerized polyethylene glycol dimethacrylate and triethylene glycol dimethacrylate, combined at different ratios. Geranylgeranylacetone (GGA), a heat-shock protein (HSP) inducer, was loaded into the device. The GGA was released from the device under zero-order kinetics. At both 1 week and 4 weeks after device implantation on rat sclera, HSP70 gene and protein expression were up-regulated in the sclera-choroid-retinal pigment epithelium fraction of rat eyes treated with the GGA-loaded device compared with rat eyes treated with saline-loaded devices or eyes of non-treated rats. Flash electroretinograms were recorded 4 days after white light exposure (8000 lx for 18 h). Electroretinographic amplitudes of the a- and b-waves were preserved significantly in rats treated with GGA-loaded devices compared with rats treated with saline-loaded devices. Histological examination showed that the outer nuclear layer thickness was preserved in rats that had the GGA-loaded device. These results may show that transscleral GGA delivery using our device may offer an alternative method to treat retinal diseases.

Topics: Animals; Blotting, Western; Choroid; Delayed-Action Preparations; Diterpenes; Drug Delivery Systems; Electroretinography; Gene Expression; Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Light; Male; Methacrylates; Polyethylene Glycols; Polymers; Polymethacrylic Acids; Rats, Sprague-Dawley; Retina; Retinal Diseases; Retinal Pigment Epithelium; Reverse Transcriptase Polymerase Chain Reaction; Sclera; Thioredoxins

Exposure to excessive light induces retinal photoreceptor cell damage, leading to development and progression of various retinal diseases. We tested the effect of geranylgeranylacetone (GGA), an acyclic polyisoprenoid, on light-induced retinal damage in mice. Oral treatment with GGA (1.0 mg/d) for 5 d induced thioredoxin (Trx) and heat shock protein 72 (Hsp72) predominantly in the retinal pigment epithelium (RPE). After white light exposure (8000 lux for 2 h), the percentage of terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling-positive photoreceptor cells decreased significantly at 24 and 96 h, and the number of photoreceptor cell nuclei at 96 h and the electroretinographic amplitudes of the a- and b-waves at 4 and 10 d increased significantly in GGA-pretreated mice compared with saline-pretreated mice. Light-induced upregulations of 8-hydroxy-2-deoxyguanosine and 4-hydroxy-2-nonenal-modified protein, markers of oxidative stress, were inhibited by GGA pretreatment. To elucidate the cytoprotective mechanism of GGA and Trx, we used human K-1034 RPE cells and mouse photoreceptor-derived 661W cells. In K-1034 cells, GGA (10 microM) induced intracellular Trx, Hsp72, and extracellular Trx but not extracellular Hsp72. Extracellular Trx (0.75 nM) attenuated H2O2 (200 microM)-induced cell damage in 661W cells. Pretreatment with GGA and overexpression of Trx in K-1034 cells counteracted H2O2 (50 microM)-induced attenuation of cellular latex bead incorporation. Protection of phagocytotic activity through induction of Trx and possibly Hsp72 in RPE cells and elimination of oxidative stress in the photoreceptor layer through release of Trx from RPE cells may be mechanisms of GGA-mediated cytoprotection. Therefore, Trx is a neurotrophic factor released from RPE cells and plays a crucial role in maintaining photoreceptor cell integrity.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aldehydes; Animals; Blotting, Western; Cell Count; Cell Death; Cell Line; Deoxyguanosine; Disease Models, Animal; Diterpenes; Electroretinography; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Gene Expression; HSP72 Heat-Shock Proteins; Humans; Hydrogen Peroxide; Immunohistochemistry; In Situ Nick-End Labeling; Light; Male; Mice; Mice, Inbred BALB C; Neoplasm Proteins; Neuroprotective Agents; Phagocytes; Photoreceptor Cells; Retinal Diseases; Thioredoxins; Time Factors