Anti-inflammatory and immunosuppressive effect of phloretin.

This study investigated the effect of phloretin (Ph) on the proliferation, activation, and cell-cycle distribution of mouse T lymphocytes and NO production and phagocytosis of macrophages. Carboxyfluorescein diacetatesuccinimidyl ester (CFDA-SE) staining plus flow cytometry assay was employed to obtain the proliferation-related index (PI) of lymphocytes. The expression levels of CD69 and CD25 on T lymphocytes stimulated with Con A were evaluated with flow cytometry after staining with fluorescent monoclonal antibody. Cell-cycle distribution of T lymphocytes was analyzed by propidium iodide staining. Griess kit was used to evaluate the NO production and fluorescent microbeads were used to analyze the phagocytosis ability of macrophages. Our results showed that phloretin (40, 60, and 80 micromol x L(-7)) significantly inhibited the proliferation of T lymphocytes and the PI reduced from 1.41 +/- 0.13 to 1.34 +/- 0.16, 1.19 +/- 0.12 and 1.07 +/- 0.06, respectively. Phloretin significantly inhibited the expression of CD69 and CD25 (P < 0.01). The cell cycle distribution analysis showed that phloretin could induce a cell cycle arrest at G0/G1 phase. NO production of LPS +IFN-gamma group of macrophages was (26.72 +/- 3.57) micromol x L(-1), and was significantly reduced by phloretin (P < 0.01). And phagocytosis rate of macrophages was significantly reduced by phloretin (P < 0.01). The results demonstrate that phloretin might be developed into a new immuosuppressive drug.

Defective PTEN regulation contributes to B cell hyperresponsiveness in systemic lupus erythematosus.

PTEN regulates normal signaling through the B cell receptor (BCR). In systemic lupus erythematosus (SLE), enhanced BCR signaling contributes to increased B cell activity, but the role of PTEN in human SLE has remained unclear. We performed fluorescence-activated cell sorting analysis in B cells from SLE patients and found that all SLE B cell subsets, except for memory B cells, showed decreased expression of PTEN compared with B cells from healthy controls. Moreover, the level of PTEN expression was inversely correlated with disease activity. We then explored the mechanisms governing PTEN regulation in SLE B cells. Notably, in normal but not SLE B cells, interleukin-21 (IL-21) induced PTEN expression and suppressed Akt phosphorylation induced by anti-immunoglobulin M and CD40L stimulation. However, this deficit was not primarily at the signaling or the transcriptional level, because IL-21-induced STAT3 (signal transducer and activator of transcription 3) phosphorylation was intact and IL-21 up-regulated PTEN mRNA in SLE B cells. Therefore, we examined the expression of candidate microRNAs (miRs) that could regulate PTEN: SLE B cells were found to express increased levels of miR-7, miR-21, and miR-22. These miRs down-regulated the expression of PTEN, and IL-21 stimulation increased the expression of miR-7 and miR-22 in both normal and SLE B cells. Indeed, a miR-7 antagomir corrected PTEN-related abnormalities in SLE B cells in a manner dependent on PTEN. Therefore, defective miR-7 regulation of PTEN contributes to B cell hyperresponsiveness in SLE and could be a new target of therapeutic intervention.