MRP4 inhibition reduces human skin DC migration. Human skin explants were intradermally injected with 20 μL of plain medium, or 20 μL containing 6.7, 20, or 60 μmol/L sildenafil. Sildenafil was also added to the culture medium of the respective samples at the same concentrations. Migrated skin DCs were harvested after 24 hours and quantified. Compared with the medium condition, significantly less cells migrated when skin was injected with 20 μmol/L (50% reduction; P < .03) or 60 μmol/L (60% reduction; P < .01) sildenafil (n = 3; 20 biopsies per condition per experiment).