Superoxide Destabilization of β-Catenin Augments Apoptosis of High-Glucose-Stressed Mesangial Cells

Abstract

Intense mesangial cell apoptosis contributes to the pathogenesis of diabetic nephropathy. Although reactive oxygen radicals and Wnt signaling components are potent regulators that modulate renal tissue remodeling and morphogenesis, cross-talk between oxidative stress and Wnt/beta-catenin signaling in controlling high-glucose-impaired mesangial cell survival and renal function have not been tested. In this study, high glucose induced Ras and Rac1 activation, superoxide burst, and Wnt5a/beta-catenin destabilization and subsequently promoted caspase-3 and poly (ADP-ribose) polymerase cleavage and apoptosis in mesangial cell cultures. The pharmacological and genetic suppression of superoxide synthesis by superoxide dismutase and diphenyloniodium, dominant-negative Ras (S17N), and dominant-negative Rac1 (T17N) abrogated high-glucose-induced glycogen synthase kinase (GSK-3beta) activation and caspase-3 and poly (ADP-ribose) polymerase degradation. Inactivation of Ras and Racl also reversed Wnt/beta-catenin expression and survival of mesangial cells. Stabilization of beta-catenin by the transfection of stable beta-catenin (Delta45) and kinase-inactive GSK-3beta attenuated high-glucose-mediated mesangial cell apoptosis. Exogenous superoxide dismutase administration attenuated urinary protein secretion in diabetic rats and abrogated diabetes-mediated reactive oxygen radical synthesis in renal glomeruli. Immunohistological observation revealed that superoxide dismutase treatment abrogated diabetes-induced caspase-3 cleavage and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) and increased Wnt5a/beta-catenin expression in renal glomeruli. Taken together, high glucose induced oxidative stress and apoptosis in mesangial cells. The Ras and Rac1 regulation of superoxide appeared to raise apoptotic activity by activating GSK-3beta and inhibiting Wnt5a/beta-catenin signaling. Controlling oxidative stress and Wnt/beta-catenin signaling has potential for protecting renal tissue against the deleterious effect of high glucose.

Yi Qi Qing Re Gao-containing serum inhibits lipopolysaccharide-induced rat mesangial cell proliferation by suppressing the Wnt pathway and TGF-β1 expression

“…Furthermore, treatment with simvastatin restored Wnt4, Wnt5a and β-catenin expression in MCs and attenuated diabetic kidney injuries both in vivo and in vitro (16). In addition, it has been demonstrated that abrogation of oxidative stress may restore Wnt5a/β-catenin signaling and attenuate high glucose-induced MC apoptosis (25). DKK-1 expression was also increased in these same conditions, and mediated c-Jun, TGF-β1, and fibronectin expression, whereas stable β-catenin expression alleviated DKK-1-induced profibrotic factors, indicating that β-catenin may be a potential therapeutic target of MC dysfunction of diabetic nephropathy (26).…”

“…In podocyte injury and proteinuric kidney diseases, the Wnt pathways are essential regulators and potential therapeutic targets (13,14). Studies regarding the role of the Wnt signaling pathway in MCs have mainly focused on hyperglycemic conditions (15,16,25,26). Lin et al (15) observed that in diabetic nephropathy, the Wnt/β-catenin signaling pathway serves a crucial role in the regulation of MC proliferation.…”

AMPK dysregulation promotes diabetes-related reduction of superoxide and mitochondrial function

“…Although several groups have identified markers of oxidative stress and oxidative damage in diabetic kidneys or kidney cells (3,4), no studies to date have attempted to measure and quantify superoxide production with diabetes directly in vivo. As the half-life of superoxide anion in cells is measured in seconds and it is rapidly converted to hydrogen peroxide and other reactive oxygen intermediates, the measurement of superoxide production has been challenging (5), especially in the intact organism.…”

Influence of glucosamine on glomerular mesangial cell turnover: implications for hyperglycemia and hexosamine pathway flux

“…In addition, renal proximal tubular cells (47), podocytes (61), and MC (23) exhibit apoptosis after exposure to high glucose concentrations, and an increase in TUNEL-positive cells has been observed in experimental and clinical diabetic nephropathy (30,64,70), although a link to flux through the hexosamine pathway has not been established. Accordingly, we studied the relationship between flux through the hexosamine pathway and MC proliferation and apoptosis.…”