Store-Operated Calcium Entry in Mesangial Cells and Glomerular Inflammatory Responses

Emerging evidence indicates that immunological and inflammatory mechanisms play a significant role in the development of diabetic nephropathy (DN). The early features of DN include accumulation of extracellular matrix (ECM) in the glomerular mesangium. Inflammatory cell infiltration mediated by locally produced cytokines/chemokines contributes to the histological impairment in DN. Glomerular mesangial cell (MC) is a major cell type in glomerulus to produce cytokines/chemokines in response to diabetes and a major contributor to mesangial expansion in DN. We have previously demonstrated that the Orai‐1 mediated store‐operated calcium entry (SOCE) suppressed ECM protein production by MCs. The aim of this study was to determine whether SOCE in MCs regulated cytokine/chemokine production by MCs and macrophage infiltration into glomerulus. Methods Orai‐1 channel protein in MCs was knocked down using the targeted nanoparticle‐siRNA delivery system in wild‐type C57BL6 mice at the age of 16 weeks. Immunohistochemistry was performed on the paraffin‐embedded kidney sections to examine macrophages infiltration in glomeruli using F4/80 as a marker. In cultured human MCs, the levels of various inflammatory cytokines (MCP‐1, TNF‐α, IL‐6) were examined using ELISA in the presence of normal glucose (5 mM D‐glucose + 20 mM L‐glucose) or high glucose (25 mM D‐glucose) with/without an activator (thapsigargin at 1 μM) of SOCE. Results In vivo knockdown of Orai1 in MCs induced infiltration of F4/80 stained macrophages into the glomeruli in the mice treated with nanoparticle/Orai1 siRNA for 5 days compared to the control mice. In cultured human MCs, 24‐hour treatment with high glucose significantly increased the expression levels of MCP‐1 and TNF‐α. The high glucose responses were significantly blunted by thapsigargin. However, high glucose treatment for 24 hours significantly decreased and activation of SOCE by thapsigargin significantly increased IL‐6 expression level in MCs. Conclusion Orai‐1 mediated SOCE in MCs inhibits the glomerular macrophage infiltration in mice and has differential effects on the expression of different cytokine/chemokines in MCs. Support or Funding Information NIH/NIDDK (1RO1 DK115424); AHA Southwest Affiliate (16GRNT27780043); Harry S. Moss Heart Trust Award. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .