Store-operated Ca2+ entry contributed to high glucose- induced podocyte injury




Tao, Yu
Chaudhari, Sarika
Shotorbani, Parisa Yazdizadeh
Ma, Rong
Chen, Zheng


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Purpose: Diabetic Nephropathy is one of the major complications of diabetes. Hyperglycemia is a known initiator of diabetes mellitus. Evidence suggests that podocyte injury is associated with diabetic nephropathy onset and progression. However, the mechanisms underlying podocyte injury induced by high glucose (HG) are poorly understood. Store-operated calcium entry (SOCE) is a multifunctional signaling pathway in many cell types. However, its role in podocyte injury in the settings of diabetes is not known. The present study was aimed to determine that enhanced SOCE mediated high glucose (HG)-induced podocyte injury by upregulating calpain activity. Methods: All experiments were performed using cultured human podocytes. Western blot was conducted to estimate Orai1, STIM1, and nephrin protein abundance. Ca2+ imaging was used to analyze SOCE. Confocal microscopy was used to visualize podocyte actin arrangement. Calpain activity was determined by calpain activity assay kits. Results: HG (25mM) treatment significantly increased Orai1, but not STIM1 protein abundance for time periods ranging from 2 to 12 hours. The HG-induced Orai1 response was dose dependent. Ca2+ imaging experiment showed that HG treatment for 12 hours significantly increased SOCE. In addition, HG treatment significantly decreased nephrin (a podocyte marker) protein abundance and resulted in cytoskeleton rearrangement by the formation of cortical F-actin. Both HG responses were significantly blunted by BTP2 (4 µM), a SOCE inhibitor. Furthermore, we found that activation of SOCE by thapsigargin (1 µM) increased calpain activity which was abolished by BTP2. In addition, BTP2 blunted the increased calpain activity induced by HG treatment. Moreover, calpeptin (a calpain inhibitor) attenuated the HG-induced reduction of nephrin protein abundance. Conclusions: The present study suggests that enhanced SOCE contributes to HG-induced podocyte injury by increasing calpain activity.