iNOS mRNA expression in (A) immuno-purified human monocytes and (B) RAW264.7 murine macrophages. Cells were fed or not with HZ or sHZ, or treated with haemin added as met-haem-albumin. A portion of the cells was additionally stimulated with IFN-gamma (100 U/mL) or a stimulatory cytokine-LPS mix (MIX+LPS) containing IFN-gamma (400 U/mL), TNF-alpha (500 U/mL), IL-1beta (100 U/mL) and LPS (20 μg/mL) (final concentrations). After 24 h incubation, mRNA was extracted from cells and iNOS-specific mRNA was quantified by real-time RT-PCR. Data are presented as fold increase in iNOS-mRNA level vs control. Mean values ± SE (n = 2–7). The difference between untreated/unfed controls and treated/fed cells was tested for significance: *p < 0.05.