Histamine induces IL-12 production and activates cytotoxic responses acting on dendritic cells: Importance of the acidic microenvironment

AMARAL MARÍA M; ALVAREZ CAROLINA; GEFFNER JORGE; VERMEULEN MÓNICA

Viña del Mar

Congreso; 9th Latin American Congress of Immunology; 2009

ALAI

We have shown that, in acidic conditions, histamine (H) increases IL-12 production by dendritic cells, through H1R. In these sense, the cytokines profile that is usually produced by DC (Th2) in presence of H, changes to Th1. Here, we analyzed if other histamine receptors are involved in IL-12 production. Taking in account that this cytokine promotes cytotoxic immune answers, we evaluated the possible role of H in this mechanism. DC were obtained from C57BL/6 bone marrow progenitors cultured with GM-CSF. They were cultured at pH 7.3 or 6.5 during 1 h, washed and suspended at pH 7.3, and treated with H (0.1 M) for 30 min at 37oC. The IL-12, IL-6 and TNF-α production were evaluated by flow cytometry. H increased TNF-α and IL-6 production by DC, but at acidic conditions this effect was reverted. % of positive cells ±SE ( n=7) for TNF-α = pH 7.3, 12.5 ± 3; pH 7.3 + H, 21 ± 3.4; pH 6.5, 12 ± 3.5, and pH 6.5 + H, 9 ± 3. % of positive cells ±SE ( n=19) for IL-6 = pH 7.3, 9.5 ± 1.4; pH 7.3 + H, 15.4 ± 3; pH 6.5, 13 ± 2.5, and pH 6.5 + H, 10 ± 1.8. On the other hand, we found a decrease of IL-12 production in DC pre-treated with Thi. % of positive cells ±SE ( n=7) for IL-12 = pH 6.5, 30 ± 5, and pH 6.5 + H, 46 ± 5; pH 6.5 + H + Thi, 32 ± 6. Interestingly, at acidic conditions, H promoted cytotoxicity by DC. cpm ±SE (n=4) pH 7.3, 19.2 ± 4.3; pH 7.3 + H, 29 ± 3; pH 6.5, 27 ± 1.5, and pH 6.5 + H, 44 ± 4.53. Finally, we examined by Real Time PCR, if acidosis could modify the normal expression of H3 and H4 receptors in DC. The H treatment resulted in a seven-fold increase on the expression of H3R in DC exposed to acidosis. In addition, the decrease on H4R expression because of the acidic conditions action was reverted by H. Our results suggest that H promotes cytotoxicity by DC at acidic conditions, acting by H1R, H3R/H4R. On the other hand, H increases pro-inflammatory cytokines production.