Inhibition of mitochondrial Na⁺-Ca²⁺ exchange by CGP-37157 attenuates BCR-mediated apoptosis in DT40 B lymphocytes

Abstract

The antigen binding to the B cell receptor (BCR) induces a rise in cytoplasmic Ca²⁺ and initiates cell responses such as apoptosis, proliferation, and differentiation in B lymphocytes. We previously showed that the inhibition of mitochondrial Na⁺-Ca²⁺ exchange (NCXm) by 7-chloro-5- (2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one [CGP-37157] dose-dependently reduced BCR-mediated rise in cytoplasmic Ca²⁺ in DT40 B lymphocytes. However, the effect of CGP-37157 on BCR-mediated apoptosis is not yet fully understood. Here, we studied the effect of NCXm inhibition on BCR-mediated apoptosis in DT40 B lymphocytes. Apoptotic cells (Annexin V⁺ and PI − ) were increased by the BCR-stimulation while the treatment of cells with 20-μM CGP-37157 attenuated the apoptosis induction. On the other hand, 24-hr treatments with 0.2 − 20 μM CGP- 37157 without the BCR stimulation did not affect the apoptotic-cell population. In the NCLX (a gene encoding NCXm) knockout cells, although the apoptotic cells were increased in the control, the appearance of late apoptotic cells (Annexin V⁺ and PI⁺) was decreased by BCR stimulation when compared to the wild-type cells. Our findings suggest that the inhibition of NCXm attenuates BCR-mediated apoptosis in DT40 B lymphocytes.