Inhibition of HO-1 activity by zinc protoporphyrin IX (ZnPPIX) enhanced infection-associated apoptosis in liver cells in vivo and macrophages in vitro, while intracellular bacterial killing was impaired in liver tissue in vivo and RAW 264.7 cells and peritoneal macrophages in vitro upon enzyme activity inhibition. This evidence concerns the gene HMOX1 and infection.