Comparative analysis of gene expression changes mediated by individual constituents of hemozoin.

Plasmodium protozoa, the source of malarial infections, catabolize large quantities of hemoglobin during an intraerythrocytic phase. During this process, free heme is detoxified through biomineralization into an insoluble heme aggregate, hemozoin (Hz). In its native state, Hz is associated with a variety of lipid peroxidation products including 4-hydroxy-2-nonenal (HNE). In the present study, gene expression profiles were used to compare responses to two of the individual components of Hz in a model macrophage cell line. LPS-stimulated RAW 264.7 cells were exposed to HNE and the synthetic form of Hz, beta-hematin (BH), for 6 or 24 h. Microarray analysis identified alterations in gene expression induced by exposure to HNE and opsonized BH (fold change, > or = 1.8; p value, < or = 0.01). Patterns of gene expression were compared to changes induced by an opsonized control latex bead challenge in LPS-stimulated cells and revealed that the BH response was predominantly phagocytic. Ingenuity Pathway Analysis demonstrated that HNE mediated a short-term oxidative stress response and had a prolonged effect on the expression of genes associated with categories of "Cell Cycle", "Cellular Assembly and Organization", "DNA Replication, Recombination, and Repair", and "Cellular Development". Comparisons of expression changes caused by BH and HNE with those observed during malarial infection suggest that BH and HNE are involved in inflammatory response modulation, altered NF-kappaB signal transduction, extracellular matrix (ECM) degradation, and dyserythropoiesis. HNE exposure led to several significant steady-state expression changes including repressed chemokine (C-C motif) ligand 5 (Ccl5), indicative of dyserythropoiesis, and a severe matrix metalloproteinase 9 (Mmp9)/tissue inhibitor of metalloproteinase 1 (Timp1) imbalance in favor of ECM proteolysis.