Illumina-microarray analysis of mycophenolic acid-induced cell death in an insulin-producing cell line and primary rat islet cells: new insights into apoptotic pathways involved.

Mycophenolic acid (MPA), widely used to prevent organ transplant rejection, may induce toxicity and impair function in beta-cells. Mechanisms of MPA-induced cell death have not been fully explored. In this study, we examined gene expression patterns in INS-1E cells and isolated primary rat islets following MPA treatment using the Illumina-cDNA microarray. The MPA treatment decreases RhoGDI-alpha gene expression, which points to apoptosis by JNK activation through a MAPKs-dependent pathway. A strong association between RhoGDI-alpha and Rac1 activation during MPA-induced apoptosis is also consistent with apoptosis through JNK. Suppression of RhoGDI-alpha using siRNA and gene over-expression both affected the cell death rate, consistent with Rac1 activation and downstream activation of MAPKs signaling. We confirmed that Rac1 protein mediates the interaction between RhoGDI-alpha and JNK signaling. We conclude that MPA-induced cell death in primary beta-cells and an insulin-secreting cell line proceeds through RhoGDI-alpha down-regulation linked to Rac1 activation, with subsequent activation of JNK. The RhoGDI-alpha/Rac1/JNK pathway may present a key to intervention in MPA-induced islet apoptosis. Copyright (c) 2010 Elsevier Inc. All rights reserved.