Na⁺/Ca²⁺ Exchanger a Druggable Target to Promote β-Cell Proliferation and Function

An important feature of type 2 diabetes is a decrease in β-cell mass. Therefore, it is essential to find new approaches to stimulate β-cell proliferation. We have previously shown that heterozygous inactivation of the Na⁺/Ca²⁺ exchanger (isoform 1; NCX1), a protein responsible for Ca²⁺ extrusion from cells, increases β-cell proliferation, mass, and function in mice. Here, we show that Ncx1 inactivation also increases β-cell proliferation in 2-year-old mice and that NCX1 inhibition in adult mice by four small molecules of the benzoxyphenyl family stimulates β-cell proliferation both in vitro and in vivo. NCX1 inhibition by small interfering RNA or small molecules activates the calcineurin/nuclear factor of activated T cells (NFAT) pathway and inhibits apoptosis induced by the immunosuppressors cyclosporine A (CsA) and tacrolimus in insulin-producing cell. Moreover, NCX1 inhibition increases the expression of β-cell-specific genes, such as Ins1, Ins2, and Pdx1, and inactivates/downregulates the tumor suppressors retinoblastoma protein (pRb) and miR-193a and the cell cycle inhibitor p53. Our data show that Na⁺/Ca²⁺ exchange is a druggable target to stimulate β-cell function and proliferation. Specific β-cell inhibition of Na⁺/Ca²⁺ exchange by phenoxybenzamyl derivatives may represent an innovative approach to promote β-cell regeneration in diabetes and improve the efficiency of pancreatic islet transplantation for the treatment of the disease.