PGE2 carried by IDENs has at least two unique characteristics in comparison with the free form of PGE2. First, the stability of PGE2 carried by IDENs is increased significantly, as shown by the fact that the half-life of PGE2 is approximately 30 seconds in mTOR inhibitor the circulator system,36,37 and intravenous injection of chemically synthesized PGE2 did not have any effect on the induction

of IFN-γ and IL-4 of mice treated with α-GalCer (data not shown) and therefore could have no effect on the activation of Wnt signaling in NKT cells. Besides the stability of PGE2 regulated by the local balance between the COX2-driven synthesis and 15-hydroxyprostaglandin dehydrogenase–mediated degradation of PGE2,38,39 in this study, we demonstrated that the amount of PGE2 carried by IDENs is also associated with the potency of induction of liver NKT AZD8055 purchase cell anergy (Supporting Figs. 5 and 6). It is conceivable that the factors regulating the amount available and the affinity of IDEN binding to PGE2 may

also contribute to PGE2-mediated Wnt signaling. The role of ceramide40 and others factors that affect COX2/15-hydroxyprostaglandin dehydrogenase–mediated PGE2 synthesis and degradation warrants further study. In addition, factors regulating gut permeability which are critical factors in regulating the amount of nanoparticle trafficking from the gut to the liver41–43 needs further study to. Caution should be exercised when drawing conclusions regarding Ureohydrolase the biological effect of PGE2 on IDENs. Effects on the Wnt signaling pathway may be different when comparing PGE2 on IDENs to that of free form of PGE2, since microRNAs and other lipids are packed in the IDENs

and may also contribute to the PGE2-mediated Wnt signaling pathway. Identifying whether IDEN microRNAs and/or lipids have a role in PGE2-mediated Wnt signaling pathway needs further study. Second, PGE2 carried by IDENs induces anergy of NKT cells not only through direct targeting of NKT cells but also through DC activation via a TLR-mediated pathway. The finding that IDENs can carry a number of therapeutic agents44 and target APCs may provide an avenue to pursue IDEN modulation of APC function and their role in gut immune tolerance. These findings also open up a new avenue for investigating further the possible role of IDENs carrying other molecules released in gut that could induce both gut and liver immune tolerance. Furthermore, from therapeutic standard point, IDENs from intestines of other species may also be a useful vehicle for delivering therapeutic reagents44,45 to treat gastrointestinal diseases as well as diseases such as liver diseases treated by oral administration. In this study, the finding that IDEN-PGE2 activated the Wnt pathway and suppressed cytokine expression via inactivation of the GSK3/β-catenin pathway raises a number of important questions that need to be addressed in future studies.