P-234

Rapamycin unbalances the polarization of macrophages to M1 in humans

A. Mercalli, I. Calavita, E. Dugnani, A. Citro, E. Cantarelli, V. Sordi, L. Piemonti
San Raffaele Scientific Institute, San Raffaele Diabetes Research Institute, Milan, Italy

Objective: Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied.

Methods and results: To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by LPS plus IFN-g or IL-4, respectively. The presence of RAPA (10 ng/ml) unbalanced the polarization to classic activation. RAPA induced macrophage apoptosis in M2 but not in M1. In M2, beyond the impactonsurvival, RAPA reduced the CXCR4, CD206 and CD209 expression and the SCGF-b, CCL18 and CCL13 release. At the other site, in M1 RAPA increased the CD86 and CCR7 expression and the IL-6, TNF-a and IL-1b release while it reduced the CD206 and CD209 expression and the IL-10, VEGF and CCL18 release. In view of in vitro data, we examined the in vivo effect of RAPA monotherapy (0.1 mg/kg/day) in 12 patients who were treated for at least 1 month prior to islet transplant. Cytokine release by TLR4-stimulated PBMC before, 2 and 4 weeks after treatment showed a clear shift to a M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1.

Conclusions: These results provide new insights into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.

P-234

Rapamycin unbalances the polarization of macrophages to M1 in humans

A. Mercalli, I. Calavita, E. Dugnani, A. Citro, E. Cantarelli, V. Sordi, L. Piemonti
San Raffaele Scientific Institute, San Raffaele Diabetes Research Institute, Milan, Italy

Objective: Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied.

Methods and results: To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by LPS plus IFN-g or IL-4, respectively. The presence of RAPA (10 ng/ml) unbalanced the polarization to classic activation. RAPA induced macrophage apoptosis in M2 but not in M1. In M2, beyond the impactonsurvival, RAPA reduced the CXCR4, CD206 and CD209 expression and the SCGF-b, CCL18 and CCL13 release. At the other site, in M1 RAPA increased the CD86 and CCR7 expression and the IL-6, TNF-a and IL-1b release while it reduced the CD206 and CD209 expression and the IL-10, VEGF and CCL18 release. In view of in vitro data, we examined the in vivo effect of RAPA monotherapy (0.1 mg/kg/day) in 12 patients who were treated for at least 1 month prior to islet transplant. Cytokine release by TLR4-stimulated PBMC before, 2 and 4 weeks after treatment showed a clear shift to a M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1.

Conclusions: These results provide new insights into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.