sirolimus and Retinal-Diseases

Chronic inflammation plays an important role in the pathogenesis of ocular diseases such as diabetic retinopathy, uveitis and age-related macular degeneration. Activation and proliferation of naïve T cells may result in pathological changes responsible for significant visual morbidity. Sirolimus (earlier termed rapamycin) is a novel drug that inhibits cellular kinases and, thereby, inhibits T-cell proliferation. Preclinical studies in experimental models have shown promising results with the use of this pharmacological agent in various ocular conditions. Subsequently, early phase I/II studies have provided encouraging safety and efficacy data. This chapter focuses on the mechanisms of action, preclinical study results and data from human clinical trials of sirolimus in human eye diseases. Key highlights from ongoing phase III clinical trials are also provided. Sirolimus, thus, appears to be an important addition to the armamentarium of steroid-sparing therapeutic agents that act on various steps in the inflammatory pathway.

Topics: Clinical Trials as Topic; Humans; Immunosuppressive Agents; Retinal Diseases; Sirolimus; Uveitis

To describe the clinical course and outcomes of aggressive retinal astrocytic hamartoma (RAH) treated with oral mechanistic target of rapamycin inhibitors (mTORis).. A retrospective clinical case series.. Five patients with genetically confirmed tuberous sclerosis complex and visually significant RAH due to tumor growth or exudation.. In this retrospective clinical case series, a review of electronic medical records was performed to determine baseline and follow-up ophthalmic examination characteristics, along with ancillary imaging findings, in patients receiving off-label treatment with either oral sirolimus or everolimus for symptomatic RAH.. Visual acuity, change in tumor size, degree of exudation, and adverse effects of the mTORis were evaluated.. The 5 patients in this series ranged in age from 8 months to 54 years. Four were treated with sirolimus, and 1 received everolimus. In all the cases, the tumor height was stable or decreased after the treatment (median follow-up duration, 39 months; range, 11-73 months). Exudation improved after the treatment in all the cases. In an 8-month-old infant, frequent upper respiratory tract infections prompted the cessation of treatment. In 1 patient, the mTORi was temporarily withheld because of elevated liver enzyme levels. No other significant adverse effects were noted.. Sirolimus and everolimus should be considered in the management of vision-threatening RAH, particularly in the setting of exudative and rapidly growing tumors. Four of the 5 patients in this series tolerated the oral mTORi and continued with the therapy. There were no serious complications.

Topics: Everolimus; Hamartoma; Humans; Infant; Retinal Diseases; Retrospective Studies; Sirolimus

To evaluate the effect of autophagy inducers on damage caused by vital dye in adult human RPE (ARPE) cells and in a rat model.. ARPE-19 cells were exposed to ICG or BBG (0.05 mg/ml) with rapamycin (200 nM) or metformin (2 mM) for 30 min and treated with or without 20 μM chloroquine (CQ) to identify the protein levels of LC3 and SQSTM1 by immunoblotting. In vivo study was performed by injecting 10 μl 0.05% ICG and 0.25% BBG into the subretinal space of the rat eyes, and/or co-treated them with metformin and rapamycin. The retinas were used to determine autophagy with the LC3-II level and apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assay.. In this study, both ICG and BBG inhibited autophagy flux in adult human retinal pigment epithelium cells (ARPE-19), whereas only ICG consistently reduced autophagy in the retina of rats. Moreover, rapamycin and metformin induced autophagic flux in ARPE-19 cells and increased the LC3-II level in retinal tissues exposed to vital dyes. Both ICG and BBG increased apoptosis in the retina of rats. However, both rapamycin and metformin induced autophagy and reduced the apoptosis caused by vital dyes.. Taken together, these results suggest that rapamycin and metformin may diminish vital dye-induced retinal damage in vivo through activation of autophagy.

Topics: Adult; Animals; Apoptosis; Cell Survival; Cells, Cultured; Coloring Agents; Disease Models, Animal; Humans; Hypoglycemic Agents; Immunosuppressive Agents; Metformin; Rats; Retinal Diseases; Retinal Pigment Epithelium; Sirolimus

Damage and loss of retinal ganglion cells (RGCs) can cause visual impairment. The underlying molecular mechanisms that mediate RGC death in ischemic retinal diseases are still unclear. In this study, we sought to understand the neuroprotective effect of rapamycin, the selective inhibitor of mTORC1, on RGC survival and the cellular mechanics that mediate this effect. Recent studies have reported that the epidermal growth factor (EGF) receptor shows an increase in expression in astrocytes after injury, and this receptor can promote their transformation into reactive astrocytes. Our results, along with previous works from others, show the colocalization of phosphor-EGF receptors with the astrocyte marker glial fibrillary acidic proteins in reactive astrocytes in the injured retina. In our in vitro studies, using primary astrocyte cultures of the optic nerve head of rats, showed that rapamycin significantly blocked EGF-induced mTOR signaling mainly through the PI3K/Akt pathway in primary astrocytes, but not through the MAPK/Erk pathway. Additionally, rapamycin dramatically inhibited the activation of mTOR signaling in our ratinal ischemia-reperfusion (I/R) injury model in vivo. Astrocyte activation was assessed by immunostaining retinal flat mounts or cross sections with antibody against GFAP, and we also used western blots to detect the expression of GFAP. Taken together, these results revealed that rapamycin decreases the activation of astrocytes after retinal ischemia-reperfusion injury. Furthermore, rapamycin can improve retinal RGC survival in rats during I/R, as detected by FluoroGold labeling. Our data reveals the neuroprotective effects of rapamycin in an experimental retina injury model, possibly through decreasing glial-dependent intracellular signaling mechanisms for suppressing apoptosis of RGCs. Our study also presents an approach to targeting reactive astrocytes for the treatment of optic neurodegenerations.

Topics: Animals; Anti-Bacterial Agents; Apoptosis; Astrocytes; Blotting, Western; Cell Survival; Cells, Cultured; Epidermal Growth Factor; Glial Fibrillary Acidic Protein; Male; Neuroprotective Agents; Optic Disk; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Retinal Diseases; Retinal Ganglion Cells; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Inhibitors of the mammalian target of rapamycin (mTOR) have been shown to protect against neuronal injury, but the mechanisms underlying this effect are not fully understood. The present study aimed to examine the effects of rapamycin, an inhibitor of the mTOR pathway, on inflammation and capillary degeneration in a rat model of N-methyl-D-aspartate (NMDA)-induced retinal neurotoxicity. Inflammation and capillary degeneration were evaluated by counting the numbers of CD45-positive leukocytes and Iba1-positive microglia, and by measuring the length of empty basement membrane sleeves, respectively. Marked increases in the numbers of leukocytes and microglia were observed 1 d after intravitreal injection of NMDA (200 nmol), and significant capillary degeneration was observed after 7 d. These NMDA-induced changes were significantly reduced by the simultaneous injection of rapamycin (20 nmol) with NMDA. These results suggest that rapamycin has preventive effects on inflammation and capillary degeneration during retinal injury.

Topics: Animals; Anti-Inflammatory Agents; Capillaries; Male; N-Methylaspartate; Rats, Sprague-Dawley; Retinal Diseases; Sirolimus

Topics: Administration, Oral; Adolescent; Adult; Antibiotics, Antineoplastic; Blood Cell Count; Creatinine; Female; Hamartoma; Humans; Liver Function Tests; Male; Retinal Diseases; Sirolimus; Tomography, Optical Coherence; Tuberous Sclerosis; Visual Acuity; Young Adult

Many chorioretinal diseases are chronic and need sustained drug delivery systems to keep therapeutic drug level at the disease site. Many intravitreal drug delivery systems under developing do not have mechanism incorporated for a non-invasive monitoring of drug release. The current study prepared rugate porous silicon (pSi) particles by electrochemical etching with the current frequency (K value) of 2.17 and 2.45. Two model drugs (rapamycin and dexamethasone) and two drug-loading strategies were tested for the feasibility to monitor drug release from the pSi particles through a color fundus camera. The pSi particles (k=2.45) with infiltration loading of rapamycin demonstrated progressively more violet color reflection which was negatively associated with the rapamycin released into the vitreous (r=-0.4, p<0.001, pairwise). In contrast, pSi with K value of 2.17 demonstrated progressive color change toward green and a weak association between rapamycin released into vitreous and green color abundance was identified (r=-0.23, p=0.002, pairwise). Dexamethasone was covalently loaded on to the fully oxidized pSi particles that appeared in vitreous as yellow color and fading over time. The yellow color decrease over time was strongly associated with the dexamethasone detected from the vitreous samples (r=0.7, p<0.0001, pairwise). These results suggest that engineered porous silicon particles may be used as a self-reporting drug delivery system for a non-invasive real time remote monitoring.. The current study, for the first time, demonstrated proof of concept that engineered porous silicon photonic crystal may deliver therapeutics in a controlled fashion while at the same time might offer a noninvasive remote monitoring of its payload release in a living eye. Porous silicon photonic crystal changes color which is in association with its payload release into vitreous. With further optimization, the color change may be harnessed to inform eye care professionals of real time drug concentration in the eye and allow them to make informed decision to re-dose the patients.

Topics: Animals; Dexamethasone; Drug Delivery Systems; Drug Monitoring; Rabbits; Retinal Diseases; Sirolimus; Video Recording

We previously demonstrated that rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), protects against N-methyl-D-aspartic acid (NMDA)-induced retinal neurotoxicity, but the mechanism underlying this protection is not fully understood. The present study aimed to examine the effects of everolimus, another inhibitor of mTOR, on neuronal cell loss and inflammation in a rat model of NMDA-induced retinal neurotoxicity, and to determine whether the extracellular signal-regulated kinase (ERK) pathway contributes to the protective effect of everolimus. Intravitreal injection of NMDA (200 nmol) resulted in (1) cell loss in the ganglion cell layer, (2) increase in the numbers of CD45-positive leukocytes and Iba1-positive microglia, and (3) phosphorylation of ribosomal protein S6 (pS6), a downstream indicator of mTOR activity. Simultaneous injection of everolimus with NMDA significantly attenuated these NMDA-induced responses. The neuroprotective effect of everolimus was almost completely prevented by the mitogen-activated protein kinase/ERK kinase inhibitor U0126 (1 nmol). NMDA increased the level of phosphorylated ERK (pERK) in Müller cells, and increase in pERK levels was also observed after co-injection of NMDA and everolimus. These results suggest that everolimus has a neuroprotective effect against NMDA-induced retinal neurotoxicity, an effect that seems to be mediated partly by activation of the ERK pathway in Müller cells.

Topics: Animals; Disease Models, Animal; Everolimus; Extracellular Signal-Regulated MAP Kinases; In Situ Nick-End Labeling; Inflammation; Intravitreal Injections; Leukocyte Common Antigens; Male; N-Methylaspartate; Neuroprotective Agents; Phosphorylation; Protein Kinase Inhibitors; Rats, Sprague-Dawley; Retina; Retinal Diseases; Retinal Ganglion Cells; Sirolimus; TOR Serine-Threonine Kinases

The role played by autophagy after ischemia/reperfusion (I/R) in the retina remains unknown. Our study investigated whether ischemic injury in the retina, which causes an energy crisis, would induce autophagy. Retinal ischemia was induced by elevation of the intraocular pressure and modulation of autophagic markers was analyzed at the protein levels in an early and late phase of recovery. Following retinal ischemia an increase in LC3BII was first observed in the early phase of recovery but did not stay until the late phase of recovery. Post-ischemic induction of autophagy by intravitreal rapamycin administration did not provide protection against the lesion induced by the ischemic stress. On the contrary, an increase in the number of apoptotic cells was observed following I/R in the rapamycin treated retinas.

Topics: Animals; Apoptosis; Autophagy; Disease Models, Animal; Immunosuppressive Agents; Male; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Retina; Retinal Diseases; Sirolimus

Topics: Edema; Humans; Immunosuppressive Agents; Macula Lutea; Male; Middle Aged; Pneumonia; Retinal Diseases; Sinusitis; Sirolimus