Notch intracellular domain 1 is involved in high glucose-induced apoptosis in glomerular podocytes in mice

Abstract

Objective To investigate the relation of Notch intracellular domain 1 (NICD1) protein expression and glomerular podocytes apoptosis of mice under high glucose (HG) culture medium and find out whether HG activated Notch pathway in podocytes via other pathways, in order to provide a potential direction to treat diabetic nephropathy. Methods NICD1 protein expression was detected in HG-induced mouse podocytes at indicated time points. Cells were divided into seven groups: normal glucose group, high glucose group, high glucose + γ-secretase inhibitor (GSI, inhibits the activation of Notch1) group, high glucose + p38 mitogen-activated protein kinase (MAPK) inhibitor group, high glucose + Janus kinase 2 (JAK2) inhibitor group, high glucose + transforming growth factor-β typeⅠ receptor (TβRⅠ) inhibitor group and high glucose + phosphoinositide 3 kinese/protein kinase B (PI3K/Akt) inhibitor group. NICD1 expression was detected by immunocytochemistry and Western blot. Apoptosis rate of HG-induced podocytes was analyzed by flow cytometry (FCM) and DeadEnd™ fluorometric TUNEL system. We used t-testing to compare the difference between two groups and one way analysis of variance to test the differences among groups. Results HG stimulation in podocytes increased NICD1 protein level than normal glucose group (0.079±0.010). NICD1 expression began to increase at 12 h after the stimulation of HG (0.443±0.075), reached the peak at 48 h (0.746±0.034) and slightly decreased at 72 h (0.658±0.056, F=6.235, P<0.01). Apoptotic cells increased in HG-induced podocytes at 48 h, which was inhibited after treatment of GSI (P<0.01). JAK2 (0.193±0.096) and TβRⅠ inhibitors (0.225±0.067)suppressed HG-induced activation of Notch pathway in podocytes (t=6.781, 4.287, both P<0.01). Conclusion Notch pathway maybe mediates HG-induced podocytes apoptosis via JAK/STAT and TGF-β1/Smad pathways. Key words: High glucose; Podocytes; Notch pathway; Apoptosis