Caspase Activation in Retinas of Diabetic and Galactosemic Mice and Diabetic Patients

Abstract

Apoptosis of retinal capillary cells begins early in diabetes and likely contributes to the capillary obliteration that is an important feature of diabetic retinopathy. Caspases are proteolytic enzymes that are closely involved in the induction and execution phases of apoptosis, but their role in the development of diabetic retinopathy has not been studied previously. Our study focused on the measurement of activities of multiple caspases in retinas of mice at different durations of diabetes. Several caspases (including caspases-1, -2, -6, -8, and -9) were activated as early as 2 months of diabetes. The caspases activity pattern changed with increasing duration of disease, suggesting a slowly developing caspases cascade. Activities of executioner caspases (e.g., cas-6 and -3) became elevated after longer duration of diabetes, and the induction of cas-3 activity was associated with the duration of diabetes at which capillary cells begin to show evidence of undergoing apoptosis. Retinas from patients with type 2 diabetes likewise showed a significant increase in activities of cas-1, -3, -4, and -6. For comparison, retinal caspases were also measured in experimental galactosemia, another model that develops a diabetic-like retinopathy. The pattern of caspases activation differed between diabetes and galactosemia, but cas-1 activity became elevated soon after elevation of blood hexose concentration in both. Caspases offer new therapeutic targets to test the role of apoptosis in the development of diabetic retinopathy.

siah-1 Protein Is Necessary for High Glucose-induced Glyceraldehyde-3-phosphate Dehydrogenase Nuclear Accumulation and Cell Death in Müller Cells

“…Tissue Culture-Rat Retinal Mü ller Cell Line (rMC-1)-rMC-1 have previously been characterized and established by others and us as a useful tool for retinal Müller cell studies (4,41,42). rMC-1 were maintained in normal (5 mM) glucose Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum and 1% penicillin/streptomycin at 37°C and 5% CO 2 in a humidified incubator.…”

Hyperglycemia-Induced Defects in Angiogenesis in the Chicken Chorioallantoic Membrane Model

“…Hyperglycemia-induced apoptosis has been observed in vitro on many endothelial cell types and in vivo in animal models of diabetes and the retinas of diabetic patients (40,41). The mechanisms by which hyperglycemia induces apoptosis are not fully characterized.…”

“…It has been shown that in pericytes, but not in endothelial cells, apoptosis is the consequence of nuclear factor-B activation (42). In vitro, the effector mechanism of increased apoptosis in endothelial cells has been shown to be the direct activation of caspases (41), an event that was prevented in vitro by incubation with an activator of AMP-kinase (43). It has been shown in vitro that hyperglycemia decreases endothelial cell proliferation (44) and that endothelial progenitor cells isolated from diabetic patients exhibit impaired proliferation, adhesion, and incorporation into vascular structure (45).…”

Nuclear GAPDH: changing the fate of Müller cells in diabetes

“…Hyperglycemia also induces the production of pro-inflammatory cytokines by Müller cells. Thus, Müller cells are a potent source for pro-inflammatory cytokines and might play a crucial role in retinal inflammation associated with the development of diabetic retinopathy [21][22][23][24][25][26]. Cytokine secretion by Müller cells influences function and viability of surrounding retinal cells, such as the retinal endothelial cells, in a paracrine fashion and their own function and viability in an autocrine manner [22].…”