Astaxanthin Protects Retinal Photoreceptor Cells against High Glucose-Induced Oxidative Stress by Induction of Antioxidant Enzymes via the PI3K/Akt/Nrf2 Pathway.

Diabetic retinopathy (DR) is a major microvascular complication that can lead to severe visual impairment in patients with diabetes. The elevated oxidative stress and increased reactive oxygen species (ROS) production induced by hyperglycemia have been reported to play an important role in the complex pathogenesis of DR. Astaxanthin (AST), a natural carotenoid derivative, has been recently recognized as a strong free radical scavenger and might, therefore, be beneficial in different diseases, including DR. In this study, we evaluated the potential role of AST as an antioxidative and antiapoptotic agent in protecting retinal cells and also investigated the involvement of the PI3K/Akt/Nrf2 pathway in AST-mediated effects. We treated high glucose-cultured mouse photoreceptor cells (661W) with different concentrations of AST and analyzed ROS production and cell apoptosis in the different regimens. Moreover, we also analyzed the expression of PI3K, Akt, Nrf2, and Phase II enzymes after AST treatment. Our results showed that AST dose-dependently reduced ROS production and attenuated 661W cell apoptosis in a high glucose environment. Importantly, its protective effect was abolished by treatment with PI3K or Nrf2 inhibitors, indicating the involvement of the PI3K/Akt/Nrf2 pathway. These results suggest AST as a nutritional supplement that could benefit patients with DR.

Effect of Fenofibrate on the Expression of Inflammatory Mediators in a Diabetic Rat Model.

Purpose: To investigate the mechanisms of anti-inflammatory and anti-oxidative effects of fenofibrate, a peroxisome proliferator-activated receptors-α agonist, in preventing diabetic retinopathy (DR) progression via a diabetic rat model. Methods: Diabetes was induced by intraperitoneal injection of streptozotocin in 6-week-old female Wistar rats. Diabetic rats were divided into diabetes without treatment (n = 10), diabetes treated with low dose fenofibrate (30 mg/kg/day) (n = 10) and high dose fenofibrate (100 mg/kg/day) (n = 10). Serum aqueous humor (AqH) and ocular tissues were gathered after 3-month treatment. Expressions of NF-κB and inflammatory chemokines (monocyte chemoattractant protein-1, fractalkine, and intercellular adhesion molecule-1) were detected by reverse transcription-polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and electrophoretic mobility shift assay. The levels of oxidative biomarkers, including acrolein, nitrotyrosine, and 8-hydroxy-2'-deoxyguanosin (8-OHdG), were determined by IHC and ELISA. The reactive oxygen species (ROS) levels in serum and AqH were measured by chemiluminescence methods. Results: After 3 months of treatment, the expressions of mRNA and protein of monocyte chemoattractant protein-1, fractalkine, and intercellular adhesion molecule-1 in the retina of diabetic rats were significantly inhibited by fenofibrate in a dose-dependent manner. These effects were mediated by inhibition of NF-κB by fenofibrate. The levels of oxidative markers, including acrolein, nitrotyrosine, and 8-OHdG, decreased in the retina of diabetic rats after fenofibrate treatment. The ROS levels in the AqH of diabetic rats also suppressed by fenofibrate. Conclusions: Fenofibrate significantly inhibited the expressions of NF-κB and inflammatory chemokines and reduced oxidative products within diabetic retina. Treatment of fenofibrate might be beneficial to preventing DR progression.

Chitosan oligosaccharides prevented retinal ischemia and reperfusion injury via reduced oxidative stress and inflammation in rats.

The purpose of the present study was to investigate the protective effect and mechanism of chitosan oligonucleotides (COS) on retinal ischemia and reperfusion (I/R) injury. Rats pretreated with PBS, low-dose COS (5 mg/kg), or high-dose COS (10 mg/kg) were subjected to retinal ischemia by increasing their intraocular pressure to 130 mm Hg for 60 min. The protective effect of COS was evaluated by determining the electroretinograms (ERGs), morphology of the retina, and survival of retinal ganglion cells (RGCs). The oxidative damage was determined by imuunohistochemistry and ELISA, respectively. The expressions of inflammatory mediators (TNF-α, IL-1ß, MCP-1, iNOS, ICAM-1) and apoptotic-related proteins (p53, Bax, Bcl-2) were quantified by PCR and Western blots. The detection of NF-κB p65 in the retina was performed by immunofluorescence. The protein levels of IκB and phosphorylated mitogen-activated protein kinases [MAPK; viz. extracellular signal-regulated protein kinases (ERK), c-Jun N-terminal kinases (JNK) and p38] and the NF-κB/DNA binding ability were assessed by Western blot analysis and EMSA. We found that pretreatment with COS, especially a high dosage, effectively ameliorated the I/R-induced reduction of the b-wave ratio in ERGs and the retinal thickness and the survival of RGCs at 24 h. COS decreased the expression of inflammatory mediators, p53 and Bax, increasing Bcl-2 expression and thereby reducing retinal oxidative damage and the number of apoptotic cells. More importantly, COS attenuated IκB degradation and p65 presence in the retina, thus decreasing NF-κB/DNA binding activity after I/R. In addition, COS decreased the phosphorylation levels of JNK and ERK but increased the phosphorylation level of p38. Pretreatment with p38 inhibitor (SB203580) abolished the protective effect of COS on retinal oxidative damage, as indicated by increased retinal 8-OHdG stains, and significantly increased the expression of inflammatory mediators (TNF-α, MCP-1, iNOS, ICAM-1) in I/R-injured rats. In conclusion, COS prevented retinal I/R injury through its inhibition of oxidative stress and inflammation. These effects were achieved by blocking the activation of NF-κB, JNK, and ERK but promoting the activation of p38 activation.

Comparative effects of fatty acids on proinflammatory gene cyclooxygenase 2 and inducible nitric oxide synthase expression in retinal pigment epithelial cells.

Dietary fat modification is a promising approach to prevent age-related macular degeneration (AMD). However, which types of fatty acids carry a greater risk for AMD remains unclear. In this study, we compared the effects of 18-carbon fatty acids with different degrees of unsaturation on the expression of the proinflammatory genes cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) in human retinal pigment epithelium (RPE). Additionally, we investigated whether lutein could modulate these genes induced by fatty acids in RPE. Treatment with oleic acid, linoleic acid (LA), or linolenic acid increased the expression of iNOS and COX-2 genes and the production of prostaglandin E(2 )and nitric oxide (NO) in RPE, whereas the saturated fatty acid stearic acid had little effect on these genes. Of the fatty acids studied, LA had the greatest effects on the induction of these genes. Furthermore, LA also induced NF-kappaB transcriptional activation the most. Lutein inhibited LA-induced expression of COX-2 and iNOS in a dose-dependent manner. These data suggested that specific unsaturated fatty acids, particularly LA, can stimulate RPE cells to express proinflammatory genes, which may contribute to the pathogenesis of AMD. Lutein inhibited the expression of these genes induced by LA through blockade of NF-kappaB activation.

Hyperbaric oxygen treatment in Purtscher's retinopathy induced by chest injury.

We present a patient who had Purtscher's retinopathy in both eyes after sustaining a chest contusion. After multiple sessions of hyperbaric oxygen (HBO) therapy were given, visual function and retinal appearance improved. This case suggests that HBO therapy may be a treatment option for Purtscher's retinopathy.

Subthreshold transpupillary thermotherapy for early resolution of foveal subretinal fluid in choroidal metastasis.

PURPOSE: To report the effectiveness of subthreshold transpupillary thermotherapy (TTT) in the early resolution of subretinal fluid at the fovea in solitary choroidal metastasis. METHODS: : Three consecutive patients who had adenocarcinoma of the lung with choroidal metastasis and macular subretinal fluid were treated by subthreshold TTT. Tumor response and fluorescein angiographic and visual results were recorded. RESULTS: Fluorescein angiography revealed solitary choroidal metastasis at the posterior pole with subretinal fluid in all patients. Initial best-corrected visual acuity in Patient 1, a 57-year-old man, was 40/200. Instead of usual high laser intensity, three applications of TTT, 400-mW power, 3-mm size, and 1-minute duration, were performed over the tumor mass. Repeated treatment with the same regimen was performed after 1 week. Visual acuity improved to 20/25 2 months after treatment. Best-corrected visual acuity in Patient 2, a 68-year-old woman, was 10/200 in the right eye before treatment. Visual acuity improved to 80/200 after treatment and remained stable for 14 months. Visual acuity improved from 20/100 to 20/60 in a third patient 2 months after treatment. The disappearance of subretinal fluid over the fovea was noted by fluorescein angiography 2 months after laser treatment and remained stable until the end of follow-up. CONCLUSION: Improvement of visual acuity and cessation of fluorescein leakage in the tumor showed that subthreshold (i.e., biomicroscopically invisible laser effect) TTT served as an effective treatment modality in the early resolution of macular subretinal fluid in choroidal metastasis. Multiple sessions of subthreshold TTT are safe to apply very close to the macula.

Circumscribed choroidal hemangioma in a Chinese patient treated using transpupillary thermotherapy: a case report.

We describe the first case of a Chinese patient with circumscribed choroidal hemangioma (CCH) effectively managed using transpupillary thermotherapy (TTT). A 57-year-old man had an elevated orange-red subretinal mass with a base of 5 x 5 mm superior to the optic disc, along with serous macular detachment in the left eye. Ultrasonography depicted a mass 3 mm thick with acoustic solidity and high internal reflectivity. Fluorescein angiography showed an area of hyperfluorescence in the prearterial phase and tumor staining in the late phase, consistent with a diagnosis of CCH. Therefore, TTT (spot size, 3 mm; exposure, 1 min) was performed with a diode laser, delivered through a slit-lamp biomicroscope. The laser power was first set at 300 mW and then increased in 50-mW increments, until test shots in the mid-peripheral retina outside the lesion produced a slightly grayish appearance in the irradiated area. The tumor was covered with four overlapping laser spots and subjected to an average beam power of 400 mW. Best-corrected visual acuity increased from 20/50 before treatment, to 20/20 3 months following one session of TTT. The lesion became atrophic and the subretinal fluid disappeared. Our experience shows that TTT can be an even more effective treatment strategy for CCH in Asians than in Caucasians. In Chinese patients, the power level of the diode laser should be lower than that used in Caucasians.

Transpupillary thermotherapy in the treatment of central serous chorioretinopathy.

A 40-year-old man had persistent central serous chorioretinopathy at the foveal region for 20 months. The pretreatment best-corrected visual acuity was 0.3. The leaking point was close to the fovea, making the use of argon laser photocoagulation treatment unsafe. Transpupillary thermal therapy with diode laser (power setting = 120 mW, spot size = 1.2 mm, and duration = 60 seconds) was performed to cover the whole detached area. The subretinal fluid decreased 1 week later. Fluorescein angiography 2 months later revealed neither further leakage nor any subretinal fluid. After 3 months of follow-up, best-corrected visual acuity improved to 0.4. Transpupillary thermal therapy may be a useful alternative for the treatment of chronic, persistent central serous chorioretinopathy at the fovea.