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 μmol·L^-1) 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-γ group of macrophages was (26.72 ± 3.57) μmol·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.