Many neuronal and retinal disorders are associated with pathological hyperpermeability of the microvasculature. We have used explants of rodent retinae to study acute neurovascular permeability and signal transduction and the role of AMP-activated protein kinase (AMPK). Following stimulation with either vascular endothelial growth factor (VEGF-A) or bradykinin (BK), AMPK was rapidly and strongly phosphorylated and acted as a key mediator of permeability downstream of Ca2+. Accordingly, AMPK agonists potently induced acute retinal vascular leakage. AMPK activation led to phosphorylation of endothelial nitric oxide synthase (eNOS), which in turn increased VE-cadherin phosphorylation on Y685. In parallel, AMPK also mediated phosphorylation of p38 MAP kinase and HSP27, indicating that it regulated paracellular junctions and cellular contractility, both previously associated with endothelial permeability. Endothelial AMPK provided a missing link in neurovascular permeability, connecting Ca2+ transients to the activation of eNOS and p38, irrespective of the permeability-inducing factor used. Collectively, we find that, due to its compatibility with small molecule antagonists/agonists and siRNA, the ex-vivo retina model constitutes a reliable tool to identify and study regulators and mechanism of acute neurovascular permeability.
IMPORTANCE Melanoma-associated retinopathy (MAR) is a paraneoplastic syndrome in which antiretinal antibodies crossreact with retinal ON-bipolar cells, resulting in night blindness and progressive visual field loss. Current therapeutic options include cytoreductive surgery in combination with immunoglobulin, corticosteroids, or plasmapheresis, but their effectiveness is limited and may be contraindicated, given the possible protective role of circulating autoantibodies against metastatic spread. We report 3-year follow-up of the first case (to our knowledge) of MAR treated with intravitreal long-acting steroid implants.OBJECTIVE To report on a patient with MAR who was treated with intravitreal fluocinolone acetonide implants in the absence of systemic immunosuppression. DESIGN, SETTING, AND PARTICIPANTSThis is a 3-year follow-up of a 73-year-old woman with a history of surgical excision of a malignant melanoma of the left pinna who presented with visual symptoms of shimmering and nyctalopia. Fundus examination, fundus autofluorescence, and optical coherence tomography were normal, with no evidence of cystoid macular edema. Automated perimetry showed a reduction in visual field and full-field electroretinography (ERG) demonstrated findings consistent with generalized ON-bipolar cell dysfunction, typical of MAR. The patient was treated with bilateral fluocinolone acetonide intravitreal implants. MAIN OUTCOMES AND MEASURESVisual acuity, visual field, and electroretinography testing for 3 years after treatment. RESULTSVisual fields improved in this 73-year-old patient from 20/30 (Snellen measured as 6/9) OD and 20/16 (6/5) OS at baseline to 20/20 OU within 1 week of treatment. Detailed electroretinography monitoring indicated characteristic abnormalities that partly resolved after treatment, consistent with improved inner retinal ON-bipolar cell function. Bilateral cataracts developed approximately 2 years after injection; cataract surgery was performed uneventfully. At 3 years posttreatment, the patient remained visually stable and in systemic disease remission, with best-corrected visual acuity remaining at 20/20 OU. CONCLUSIONS AND RELEVANCEWe report what is, to our knowledge, the first case of MAR treated with intravitreal slow-release corticosteroid implants, which shows improvements in visual symptoms, visual fields, and retinal function. Sustained-release intraocular steroid implants may offer an effective and safe alternative to systemic immunosuppression in MAR, although results from 1 case should be generalized with abundant caution.
12Pathological hyperpermeability accompanies many blinding retinopathies. Despite 13 important therapeutic breakthroughs benefitting many but not all retinopathy patients, 14 the intracellular signalling underlying retinal leakage is still poorly understood. We 15 have developed an ex-vivo model, which allowed us to measure and manipulate acute 16 vascular permeability in the intact rodent retina, and combined measurements with 17 immunohistochemical analyses of signal transduction. This ex-vivo retina platform 18 proved to be an easily accessible and reliable tool for systematic identification of 19 regulators of vascular permeability through small molecule antagonists/agonists and 20 siRNA. By using this model, we showed that AMPK was a key mediator of VEGF-and 21 bradykinin-induced permeability by acting downstream of Ca 2+ and CAMKK, and 22 upstream of eNOS/VE-cadherin as well as p38/HSP27. Accordingly, AMPK agonist 23 potently induced retinal vascular leakage, a finding of major importance for their use 24 as therapeutic agents in the treatment of e.g. cancer or metabolic syndrome. 25 26 489 490 1 Nagy, 500 5 Ford, J. A. et al. Current treatments in diabetic macular oedema: systematic review and meta-501 analysis. BMJ Open 3, 504 7 Canning, P. et al. Lipoprotein-associated phospholipase A2 (Lp-PLA2) as a therapeutic target 505 to prevent retinal vasopermeability during diabetes. of phospholipase C, protein 510 kinase C, and calcium in VEGF-induced venular hyperpermeability. Am J Physiol 276, H535-511 542,
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