Abnormal signaling activity of phosphatidylinositol 3-kinase pathway in peripheral blood T cells from patients with systemic lupus erythematosus

Abstract

To investigate the activity of phosphatidylinositol 3-kinase (PI3K) signal pathway, a cytoplasmic signaling pathway known to play an important role in T cell activation, in peripheral blood T cells from systemic lupus erythematosus (SLE) patients. T cells were isolated from the peripheral blood samples of 28 SLE patients, 5 males and 23 females, with RosettSep T cell purification kit. PI3K activity was determined by immunoprecipitation and ELISA, and Western blotting was used to measure the Akt and phosphorylated Akt protein expression. T cell proliferation and cytokine production was examined by MTT test and ELISA respectively. Fifteen healthy adults and 8 active rheumatoid arthritis patients were used as controls. The T cells from the SLE patients and normal controls were treated with 10% normal control serum of SLE serum for 24 h ("rest") and then to detect the P13K and Akt activity. Some T cells from the SLE patients were stimulated with CD3/CD28 mono-antibodies or CD3/CD28 mono-antibodies + LY294002, a specific P13K inhibitor, and then the proliferation and secretion of IL-6 and IL-10 were analyzed. Compared with the healthy controls and rheumatoid arthritis patients, the activity levels of PI3K and Akt in the T cells of peripheral blood from the SLE patients were significantly increased. T cells allowed to "rest" for 24 hours in culture medium showed a reversal of the changes in activity of PI3K and Akt. The activity of PI3K pathway was increased in the T cells from healthy controls when cultured with SLE serum. The proliferation and IL-6 and IL-10 secretion of the T cells from SLE patients cultured with LY294002 were inhibited. The P13K and Akt activity levels of the T cells from SLE patients were not related to SLE disease activity index (SLEDAI). The T cells from SLE patients show an abnormal activation of PI3K pathway which may be due, at least in part, to their exposure to relevant serum factors.