Role of endoplasmic reticulum stress in apoptosis of differentiated mouse podocytes induced by high glucose

Abstract

Podocytes are terminally differentiated epithelial cells lacking the ability to proliferate. The loss of podocytes is a hallmark of progressive kidney diseases, including diabetic nephropathy (DN). Endoplasmic reticulum stress (ERS)-induced apoptosis is involved in a number of pathological conditions, including DN. The aim of the present study was to investigate whether a high glucose environment induces the apoptosis of podocytes through ERS. Differentiated mouse podocytes were divided into three groups: the normal glucose group (NG, 1 g/l D-glucose), the high glucose group (HG, 4.5 g/l D-glucose) and the mannitol group (M, 1 g/l D-glucose plus 24.4 mM mannitol). The cells were harvested following stimulation with the indicated treatments for 12, 24, 48 and 72 h. Podocyte apoptosis was determined using TUNEL assay and flow cytometry (propidium iodide staining). Glucose-regulated protein 78 (GRP78), CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP/GADD153) and caspase-12 expression was analyzed by RT-PCR, western blot analysis and immunocytochemistry. The apoptotic rate increased significantly in the HG group compared with the NG and M groups at 48 and 72 h (all P<0.01). GRP78 expression, an indicator of ERS, was increased from 12 h, indicating that ERS was activated. Subsequently, two ER-associated death (ERAD) pathways, the CHOP/GADD153- and caspase-12-dependent pathways, were detected. CHOP/GADD153 expression reached its peak at 48 h, and caspase-12 expression gradually increased with time. Spearman’s correlation analysis revealed that caspase-12 and CHOP/GADD153 positively correlated with the apoptotic rate (r=0.915, P<0.01 and r=0.639, P<0.01). Our results demonstrated that hyperglycemia (high glucose) induced apoptosis partly through ERS in the differentiated mouse podocytes, which possibly contributes to the pathogenesis of DN.

Ursodeoxycholic acid and 4-phenylbutyrate prevent endoplasmic reticulum stress-induced podocyte apoptosis in diabetic nephropathy

“…Our results were similar to other investigators. 7,43 Inagi et al 44 demonstrated that podocytes treated with hyperglycemia did not upregulate ER stress markers. As mentioned in the section of methods in their study, podocytes were cultured in the presence of 4.5 mg/ml (25 mM) D-or L-glucose for 2 weeks.…”

Pathologic changes of pancreatic endothelial cells in Diabetic Rat

“…On the one hand, long-term high blood sugar can weaken the synthesis of islet cells and secretion of insulin, and reduce insulin secretion or loss of glucose. On the other hand, long-term high blood sugar decreases the number of islet cells and increases failure islet beta-cell function in patients with diabetes [5][6][7]. STZ-induced diabetic rat model is similar to human diabetes, which has the same pathological and physiological changes.…”

Hydrogen sulfide exhibits cardioprotective effects by decreasing endoplasmic reticulum stress in a diabetic cardiomyopathy rat model

“…The pathophysiology of apoptosis was closely associated with ERS. New evidence demonstrated that hyperglycemia induced apoptosis by activating ERS (67,68). In addition, in diabetic heart tissue, the ER was found to be swollen and dilated following ultrastructural analysis, suggesting abnormalities in the ER in a hyperglycemic environment (69)(70)(71).…”