OX40-OX40L Interaction Promotes Proliferation and Activation of Lymphocytes via NFATc1 in ApoE-Deficient Mice

Background: Our previous studies have shown that OX40-OX40L interaction regulates the expression of nuclear factor of activated T cells c1(NFATc1) in ApoE(-/-) mice during atherogenesis. The aim of this study was to investigate whether OX40-OX40L interaction promotes Th cell activation via NFATc1 in ApoE(-/-) mice. Methods and Results: The lymphocytes isolated from spleen of ApoE(-/-) mice were cultured with anti-CD3 mAb in the presence or absence of anti-OX40 or anti-OX40L antibodies. The expression of NFATc1 mRNA and protein in isolated lymphocytes were measured by real time PCR (RT-PCR) and flow cytometry (FCM), respectively. The proliferation of lymphocytes was analyzed by MTT method, and the expression of IL-2, IL-4 and IFN-gamma in the cultured cells and supernatant were measured by RT-PCR and enzyme-linked immunosorbent assary (ELISA), respectively. After stimulating OX40-OX40L signal pathway, the expression of NFATc1 and the proliferation of leukocytes were significantly increased. Anti-OX40L suppressed the expression of NFATc1 in lymphocytes of ApoE(-/-) mice. Anti-OX40L or the NFATc1 inhibitor (CsA) markedly suppressed the cell proliferation induced by anti-OX40. Moreover, the expression of IL-2 and IFN-gamma was increased in lymphocytes induced by OX40-OX40L interaction. Blocking OX40-OX40L interaction or NFATc1 down-regulated the expression of IL-2 and IFN-gamma, but didn't alter the expression of IL-4 in supernatants. Conclusion: These results suggest that OX40-OX40L interaction promotes the proliferation and activation of lymphocytes through NFATc1.