Phloretin Modulates Human Th17/Treg Cell Differentiation In Vitro via AMPK Signaling

Context. The imbalance between T helper 17 (Th17) cell and regulatory T (Treg) cell is involved in many immune disorders and diseases. Phloretin, a dihydrochalcone structural flavonoid compound, possesses many bioactive properties. However, whether phloretin could impact on the differentiation of T cells is not completely clear. Objective. We conducted studies to explore the effect of phloretin on glucose uptake, proliferation, and differentiation of human peripheral blood CD4(+) T cells and investigated the mechanism of phloretin on inducing Th17/Treg development. Methods. Naive CD4(+) T cells were purified from peripheral blood of healthy volunteers, stimulated with anti-CD3/CD28 antibodies, and polarized in vitro to generate Th17 or Treg cells. Glucose uptake, proliferation, cell cycle, protein expression (phospho-Stat3, phospho-Stat5), and Th17 and Treg cell numbers were analyzed by flow cytometry. AMP-activated protein kinase (AMPK) signaling was analyzed by western blot. Results and Discussion. Phloretin could inhibit the glucose uptake and proliferation of activated CD4(+) T cells. The proliferation inhibition was due to the G0/G1 phase arrest. Phloretin decreased Th17 cell generation and phospho-Stat3 expression as well as increased Treg cell generation and phospho-Stat5 expression in the process of inducing Th17/Treg differentiation. The phosphorylation level of AMPK was significantly enhanced, while the phosphorylation level of mTOR was significantly decreased in activated CD4(+) T cells under phloretin treatment. The AMPK signaling inhibitor compound C (Com C) could neutralize the effect of phloretin, while the agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) could impact the Th17/Treg balance similar to phloretin during Th17/Treg induction. Conclusion. Our results suggest that phloretin can mediate the Th17/Treg balance by regulating metabolism via the AMPK signal pathway.