Inhibition of dendritic cell maturation and effector function

The initiation of donor derived dendritic cell (DC) adhesion and migration are one of the key events mediated by ischemia reperfusion injury (IRI) following solid organ transplantation. Recently we have been able to demonstrate that a single donor treatment with the synthetic metalloporphyrin cobalt protoporphyrin (CoPPIX) for heme oxygenase 1 (HO-1) induction results in the reduction of donor-derived DCs following IRI thus leading to the preservation of graft long-term function. Gene expression analysis in murine liver revealed the up-regulation of the signal transducer and activator of transcription 3 (STAT3) after CoPPIX treatment. Since it has been shown that CoPPIX is able to inhibit DC maturation, we could demonstrate that DC (-LPS) induced maturation guided by the secretion of pro-inflammatory cytokines and alloreactive T cell proliferation is dependent of STAT3 phosphorylation and independent of HO-1 activity. These observations highlight the immunomodulatory capacity of STAT3 which might be of further interest for the inhibition of immune response. Keywords: dendritic cells, heme oxygenase-1 (HO-1), STAT3, cobalt protoporphyrin For the analysis of gene expression profiles in vivo C57BL/6 mice were treated either with 5 mg/kg CoPPIX, i.p., 50 mg/kg MC, p.o. and 500 ppm CO for 6 or 24 hrs (3 animals in each group). Untreated C57BL/6 mice were used as controls (n=9). After 6 or 24 hrs of treatment animals were sacrificed and whole livers were harvested for analysis.