mTOR complex 1 controls the nuclear localization and function of glycogen synthase kinase 3ß.

Glycogen synthase kinase 3ß (GSK3ß) phosphorylates and thereby regulates a wide range of protein substrates involved in diverse cellular functions. Some GSK3ß substrates, such as c-Myc and Snail, are nuclear transcription factors, suggesting the possibility that GSK3ß function is controlled through its nuclear localization. Here, using ARPE-19 and MDA-MB-231 human cell lines, we found that inhibition of mTOR complex 1 (mTORC1) leads to partial redistribution of GSK3ß from the cytosol to the nucleus and to a GSK3ß-dependent reduction of the levels of both c-Myc and Snail. mTORC1 is known to be controlled by metabolic cues, such as by AMP-activated protein kinase (AMPK) or amino acid abundance, and we observed here that AMPK activation or amino acid deprivation promotes GSK3ß nuclear localization in an mTORC1-dependent manner. GSK3ß was detected on several distinct endomembrane compartments, including lysosomes. Consistently, disruption of late endosomes/lysosomes through a perturbation of RAS oncogene family member 7 (Rab7) resulted in loss of GSK3ß from lysosomes and in enhanced GSK3ß nuclear localization as well as GSK3ß-dependent reduction of c-Myc levels. These findings indicate that the nuclear localization and function of GSK3ß is suppressed by mTORC1 and suggest a link between metabolic conditions sensed by mTORC1 and GSK3ß-dependent regulation of transcriptional networks controlling cellular biomass production.

Treatment of anti-vascular endothelial growth factor-resistant diabetic macular edema with dexamethasone intravitreal implant.

PURPOSE: To investigate the efficiency of intravitreal dexamethasone implant in patients with chronic diabetic macular edema nonresponsive to three consecutive monthly intravitreal injections of anti-vascular endothelial growth factor administered previously. METHODS: Fifteen patients (16 eyes) were included in this 4-month prospective clinical trial. Main observed outcomes were the changes between initial and monthly visits in best-corrected visual acuity, central foveal thickness, and intraocular pressure (IOP). Patients included had central foveal thickness of >225 µm (measured by optical coherence tomography) and were nonresponsive to previously administered 3 consecutive monthly intravitreal injections of 1.25-mg bevacizumab. Administration of intravitreal dexamethasone implant was performed at baseline, and patients were followed-up monthly. RESULTS: Statistically significant changes from baseline were observed in best-corrected visual acuity (at 2 months), central foveal thickness (at 1, 2, and 3 months), and IOP (at Months 1, 2, and 3) as follows: mean best-corrected visual acuity significantly increased from 0.29 Snellen lines at baseline to 0.39 lines after 2 months (P = 0.0381). At Months 1, 2, and 3, the mean central foveal thickness significantly decreased, from 462 µm at baseline, to 366 µm (P = 0.0343), 346 µm (P = 0.0288), and 355 µm (P = 0.0370), respectively. When compared with baseline IOP of 15.38 mmHg (12-19 mmHg), IOP increased significantly at Months 1, 2, and 3: 18.93 mmHg (range, 16-24 mmHg; P = 0.0003), 19.5 mmHg (range, 16-27 mmHg; P = 0.0003), and 17.5 mmHg (range, 15-21 mmHg; P = 0.0048), respectively. CONCLUSION: Dexamethasone intravitreal implant may present an alternative option in the treatment of chronic diabetic macular edema nonresponsive to three consecutive monthly bevacizumab injections administered previously. However, IOP measures were only slightly increased. It seems that the effect of dexamethasone may last till 4 months after initial injection.

Anti-VEGF in treatment of diabetic macular edema.

Diabetic macular edema is the leading cause of moderate visual deterioration in patients with diabetic retinopathy. Ranibizumab) blocks vascular endothelial growth factor (VEGF) induced hyperpermeability of blood vessels. In this prospective case series we investigated the efficacy and safety of anti-VEGF treatment in reduction of central retinal thickness (CRT) and improvement in visual acuity (VA) in patients with diabetic macular edema (DME). 9 patients were followed up for 6 months and treated monthly with intravitreal ranibizumab. VA and CRT were measured at each visit. Treatment was discontinued as the peak improvement of either parameter was reached and reinstituted in case of deterioration/recurrence of edema. Study endpoints included: VA using ETDRS chart, CRT and number of injections at 6 months. Mean VA from all 9 patients increased by 0.3 lines of logMAR (p < 0.05 compared to baseline), and CRT decreased from 515 +/- 123 microm to 310 +/- 110 microm. The improvement of VA after ranibizumab injection was in correlation with a decrease in CRT. Mean of 4 injections were needed to control the disease during the follow-up period. Ranibizumab treatment was effective in VA and reducing CRT. Several injections were needed to control the disease. Regular OCT examinations and retreatment are advised in order to maintain initially reached VA.

Anti-VEGF in treatment of central retinal vein occlusion.

Macular edema along with macular ischemia is responsible for decreased visual acuity in central retinal vein occlusion. Bevacizumab (Avastin, Genentech) blocks vascular endothelial growth factor (VEGF) induced hyperpermeability of blood vessels. In this prospective case series we investigated the efficacy of anti-VEGF treatment in reduction of central retinal thickness (CRT) and improvement in visual acuity (VA). 25 patients were followed up for 12 months and treated monthly with intravitreal bevacizumab. VA and CRT were measured at each visit. Treatment was discontinued as the peak improvement of either parameter was reached and reinstituted in case of deterioration/recurrence of edema. Study endpoints included: VA using ETDRS charts, CRT and number of injections at 12 months. Mean VA from all 25 patients increased by 3.1 logMAR lines (p < 0.05 compared to baseline). The improvement of VA after bevacizumab injection was in correlation with a decrease in CRT In subgroup analyses, patients receiving bevacizumab injection within the first 3 months after CRVO showed an average VA gain of 4.2 logMAR lines. Mean of 4.5 injections was needed to control the disease during the follow-up period. Bevacizumab treatment was effective in VA and reducing CRT. It appears from subgroup analysis that initiation of treatment early in the course of disease produced better functional outcome. Several injections were needed to control the disease. Regular OCT examinations and retreatment are advised in order to maintain initially reached VA.