Synergistic action of DPIV and APN in the regulation of T cell function.

Inhibitors of the enzymatic activity of alanyl-aminopeptidases severely affect growth and typical functions of human peripheral T cells both in vitro and in vivo. The most prominent changes observed include the activation of cellular signal transduction pathways such as MAP kinases Erk1/2 or the Wnt-pathway, a decrease of production and release of "pro-inflammatory" cytokines (IL-2, IL-12) and, most importantly, an induction of expression and release of the immunosuppressive cytokine, TGF-beta1. Similar effects on T cell proliferation and function have been observed in response to inhibition of DPIV, which is strongly suggestive of a functional synergism of APN and DPIV. In support of this hypothesis evidence is provided showing that the simultaneous application of inhibitors of DPIV and APN further enhances the anti-inflammatory and immunosuppressive effects provoked by the inhibition of APN or DPIV alone. Therefore, the simultaneous inhibition of these enzymes represents a promising strategy for the pharmacological therapy of T cell mediated diseases such as autoimmune disease, inflammation, allergy, and allograft rejection.