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Susanne Mohr, Derrick J. Feenstra, Katherine Trueblood, George Dubyak, E.Chepchumba Yego; Autoinflammation in Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):999.
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Hyperglycemia leads to sustained activation of caspase-1 in the retinas of diabetic animals and patients in vivo and in retinal cells in vitro. How caspase-1 activation is achieved and sustained is unknown. This study was focused on identifying mechanisms regulating high glucose-induced caspase-1 activity in vitro and in vivo.
Capillary degeneration in diabetic wild type and caspase-1 knock-out mice was assessed by elastase digestion. Caspase-1 activation patterns were determined from retinas of normal and diabetic wild type (C57Bl6) and IL-1β receptor knock-out (IL1R-/-) mice using a caspase-1 specific fluorescence substrate. Retinal Müller cells were treated with 5mM, 25 mM, or 25mM glucose medium plus IL-1 receptor antagonist (IL-1ra) for up to 96 hours followed by caspase-1 activity measurements. QPCR and Western Blot analysis were used to determine NALP3 levels in retinal Müller cells and retinal tissue of non-diabetic and diabetic donors.
Caspase-1 knock-out inhibits the diabetes-induced increase in numbers of acellular capillaries/mm2 by 65±19% compared to wild type. Hyperglycemia induced a multi-phasic pattern of caspase-1 activation in retinal tissue and Müller cells compared to controls. The IL-1ra, which prevents downstream signaling of caspase-1/IL-1β, significantly decreased late phase caspase-1 activity by 30.48 ± 10.61% at 72 hours compared to high glucose alone. In vivo, knock-out of the IL-1 receptor prevented late phase activation of caspase-1 in the diabetic retina. Hyperglycemia-induced caspase-1 activation is mediated by the induction of the NALP3 inflammasome. NALP3 levels increased by 10 ± 5% in retinal tissue from diabetic donors compared to non-diabetic donors.
Diabetes induces an autoinflammatory response within retinal tissue that is mediated by the continuous activation of the caspase-1/IL-1β signaling pathway via the NALP3 inflammasome. Interfering in the caspase-1/IL-1β activation feedback cycle represents a novel therapeutic strategy to prevent the progression of diabetic retinopathy.
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