Expression of genes encoding innate host defense molecules in normal human monocytes in response to Candida albicans

Abstract

Little is known about the regulation and coordinated expression of genes involved in the innate host response to Candida albicans. We therefore examined the kinetic profile of gene expression of innate host defense molecules in normal human monocytes infected with C. albicans using microarray technology. Freshly isolated peripheral blood monocytes from five healthy donors were incubated with C. albicans for 0 to 18 h in parallel with time-matched uninfected control cells. RNA from monocytes was extracted and amplified for microarray analysis, using a 42,421-gene cDNA chip. Expression of genes encoding proinflammatory cytokines, including tumor necrosis factor alpha, interleukin 1 (IL-1), IL-6, and leukemia inhibitory factor, was markedly enhanced during the first 6 h and coincided with an increase in phagocytosis. Expression of these genes returned to near baseline by 18 h. Genes encoding chemokines, including IL-8; macrophage inflammatory proteins 1, 3, and 4; and monocyte chemoattractant protein 1, also were strongly up-regulated, with peak expression at 4 to 6 h, as were genes encoding chemokine receptors CCR1, CCR5, CCR7, and CXCR5. Expression of genes whose products may protect monocyte viability, such as BCL2-related protein, metallothioneins, CD71, and SOCS3, was up-regulated at 4 to 6 h and remained elevated throughout the 18-h time course. On the other hand, expression of genes encoding T-cell-regulatory molecules (e.g., IL-12, gamma interferon, and transforming growth factor beta) was not significantly affected during the 18-h incubation. Moreover, genes encoding IL-15, the IL-13 receptor (IL-13Ra1), and CD14 were suppressed during the 18-h exposure to C. albicans. Thus, C. albicans is a potent inducer of a dynamic cascade of expression of genes whose products are related to the recruitment, activation, and protection of neutrophils and monocytes.

FIG. 1.

Percent phagocytosis of Candida albicans by normal human monocytes over an 18-h time course. Data represent the means ± SEM for five separate donors at each time point.

FIG. 2.

Gene expression heat map of up-regulated genes in normal human monocytes in response to Candida albicans, demonstrating 785 genes that were up-regulated ≥2.5-fold during the 18-h time course.

FIG. 3.

Heat map of gene expression for immunologically defined classes of molecules of innate host response in normal human monocytes in response to Candida albicans during the 18-h time course.

FIG. 4.

Kinetics of expression of genes encoding proinflammatory molecules of normal human monocytes in response to Candida albicans over 18 h. Data represent the mean changes (n-fold) in expression for five separate donors at each time point.

FIG. 5.

Kinetics of expression of genes encoding chemotaxis regulatory molecules in normal human monocytes in response to Candida albicans over 18 h. Data represent the mean changes (n-fold) in expression for five separate donors at each time point.

FIG. 6.

Summary kinetic profile of expression of immunologically important classes of genes in monocyte host defense against C. albicans over an 18-h time course. The expression of genes encoding proinflammatory cytokines, chemokines, some chemokine receptors, COX2, heat shock proteins, antiapoptosis molecules, connexins, metallothioneins, transferrin receptor, and SOCS3 are all up-regulated in association with early monocyte response to C. albicans. By comparison, the gene encoding the chemokine receptor CCR2 is down-regulated within the first 18 h of exposure to C. albicans. Data represent mean changes (n-fold) for genes in each group with ≥2.5-fold change.