Histamine and prostaglandin E up-regulate the production of Th2-attracting chemokines (CCL17 and CCL22) and down-regulate IFN-gamma-induced CXCL10 production by immature human dendritic cells

Abstract

Effector memory T helper 2 (Th2) cells that accumulate in target organs (i.e. skin or bronchial mucosa) have a central role in the pathogenesis of allergic disorders. To date, the factors that selectively trigger local production of Th2-attracting chemokines remain poorly understood. In mucosa, at the sites of allergen entry, immature dendritic cells (DC) are in close contact with mast cells. Histamine and prostaglandin E2 (PGE2) are two mediators released by allergen-activated mast cells that favour the polarization of maturing DC into Th2-polarizing cells. We analysed here the effects of histamine and PGE2 on the prototypic, Th2-(CCL17, CCL22) versus Th1-(CXCL10) chemokine production by human DC. We report that histamine and PGE2 dose-dependently up-regulate CCL17 and CCL22 by monocyte-derived immature DC. These effects were potentiated by tumour necrosis factor-alpha, still observed in the presence of the Th1-cytokine interferon-gamma (IFN-gamma) and abolished by the immunomodulatory cytokine interleukin-10. In addition, histamine and PGE2 down-regulated IFN-gamma-induced CXCL10 production by monocyte-derived DC. These properties of histamine and PGE2 were observed at the transcriptional level and were mediated mainly through H2 receptors for histamine and through EP2 and EP4 receptors for PGE2. Finally, histamine and PGE2 also up-regulated CCL17 and CCL22 and decreased IFN-gamma-induced CXCL10 production by purified human myeloid DC. In conclusion, these data show that, in addition to polarizing DC into mature cells that promote naïve T-cell differentiation into Th2 cells, histamine and PGE2 may act on immature DC to trigger local Th2 cell recruitment through a selective control of Th1/Th2-attracting chemokine production, thereby contributing to maintain a microenvironment favourable to persistent immunoglobulin E synthesis.

Figure 1

Histamine and PGE₂ up-regulate CCL17 and CCL22 production by immature human monocyte-derived DC. Monocyte-derived DC were not or were incubated with 0·1–10 µm histamine (▪) or PGE₂ (○) (left panels) or with 10 µm histamine (▪) or PGE₂ (○) (right panels). CCL17 (upper panels) and CCL22 (lower panels) were quantified by ELISA in the 48 hr supernatants (left panels) or at the indicated time-points (right panels). Results are expressed as mean ± SD of five separate experiments. *P < 0·05.

Figure 2

Histamine and PGE₂ modulate CCL17, CCL22 and CXCL10 mRNA expression. (a) Monocyte-derived DC were either untreated or exposed to 10 µm histamine or PGE₂ in the absence (left panels) or presence of 20 ng/ml IFN-γ (right panels). After 8 hr incubation, CCL17, CCL22 and CXCL10 mRNA expression was evaluated by RT–PCR. RNA integrity and cDNA synthesis was verified by amplifying GAPDH cDNA. Results are representative of one out of five experiments. (b) Densitometry analysis. CCL17, CCL22 and CXCL10 mRNA expression after stimulation with histamine or PGE₂ is expressed as a ratio of relative band intensity in comparison with mRNA expression without stimulation (left panels) or stimulated with IFN-γ alone (right panels).

Figure 3

The effects of histamine and PGE₂ were potentiated by TNF-α and prevented by IL-10. (a & b) Monocyte-derived DC were not or were incubated with 0·01–10 µm histamine or PGE₂ in the absence (▪) or presence (□) of 2 ng/ml TNF-α. (c) DC were stimulated with 1 µm histamine or PGE₂ in the absence (▪) or presence (□) of 25 ng/ml IL-10. (a–c) CCL17 (a and c left panel) and CCL22 (b and c right panel) were quantified by ELISA in the 48 hr supernatants. As a control, the production of CCL17 (a) and CCL22 (b) in the presence of 25 ng/ml TNF-α is indicated (hatched histogram). Results are expressed as mean ± SD of four experiments. *P < 0·05.

Figure 4

Histamine and PGE₂ modulate CCL17, CCL22 and CXCL10 production by peripheral blood myeloid DC. (a & b) Freshly isolated peripheral blood myeloid DC were not or were stimulated with 1 µm histamine or PGE₂ in the absence (▪) or presence (□) of 2 ng/ml TNF-α. CCL17 (a) and CCL22 (b) were quantified by ELISA in the 48 hr supernatants. (c) Freshly purified peripheral blood myeloid DC were not or were stimulated with 1 µm histamine or PGE₂ in the absence (▪) or presence (□) of 20 ng/ml IFN-γ. CXCL10 was quantified by ELISA in the 48 hr supernatants. Results are expressed as mean ± SD of four experiments. *P < 0·05.

Figure 5

Histamine and PGE₂ decreased IFNγ-induced CXCL10 production. (a–c) Monocyte-derived DC were not (hatched histograms) or were incubated with 0·1–10 µm histamine (black histograms) or PGE₂ (grey histograms) in the absence or presence of 20 ng/ml IFN-γ. CXCL10 (a), CCL17 (b) and CCL22 (c) were quantified by ELISA in the 48 hr supernatants. Results are expressed as mean ± SD of five experiments. *P < 0·05.

Figure 6

Histamine and PGE₂ receptors involved in the modulation of chemokine production. (a) Monocyte-derived DC were incubated with 1 µm histamine in the absence or presence of 1 µm of H1, H2 or H3 receptor antagonists (mepyramine, cimetidine or thioperamide, respectively). (b) Monocyte-derived DC were incubated with 1 µm of the EP receptor agonists: Sulprostone (EP1 + EP3), Butaprost (EP2), 17-phenyl-w-trinor (EP1 + EP3), and PGE₁ alcohol (EP3/EP4). CCL17 (black bars), CCL22 (grey) and CXCL10 (white) were quantified by ELISA in the 48 hr supernatants. Results are expressed as a percentage of inhibition of CCL17 or CCL22 or as a percentage of increase of CXCL10 production, as described in Materials and methods (mean ± SD of three separate experiments). *P < 0·05.

Figure 7

Involvement of the cAMP/PKA pathway in the modulation of chemokine production by histamine and PGE₂. (a & b) Monocyte-derived DC were incubated with 100 nm of a PKA (H89) or a PKC (calphostin C) inhibitor, and stimulated with histamine and PGE2 in the absence (a) or presence (b) of 20 ng/ml IFN-γ. CCL22 (a) and CXCL10 (b) were quantified by ELISA in the 24 hr supernatants. Results are expressed as a percentage of inhibition of CCL22 or as a percentage of increase of CXCL10 production, as described in Materials and methods (mean ± SD of three separate experiments).