Histamine H₂ receptors and histidine decarboxylase in normal and leukemic human monocytes and macrophages

Spontaneous and all-trans-retinoic acid (RA)-induced differentiation of normal human monocytes and of leukemic THP-1 monocytes into macrophages resulted in a progressive loss of adenosine 3',5'-cyclic monophosphate production induced by histamine via typical H₂ receptors (H₂R). In THP-1 cells and in HL-60 human acute myelocytic leukemia cells, RA treatment increased the abundance of the 4.5-kb messenger RNA of the H₂R gene fourfold, suggesting transcriptional control by a RA response element. Scatchard plots of [³H]tiotidine binding indicated the expression of H₂R with similar affinity and binding capacity in THP-1 monocytes and macrophages, while the conversion of normal monocytes into macrophages decreased H₂R density from 91.8 to 43.1 fmol/mg protein, with no change in affinity (K(d) = 9.9 to 11.2 nM). In THP-1 macrophages, histamine inhibited 4β-phorbol 12-myristate 13-acetate (PMA)-induced H₂O₂ formation via the activation of H₂ receptors. Expression of the H₂R gene, histamine accumulation, and histidine decarboxylase activity were also demonstrated in normal human monocytes/macrophages and peripheral lymphocytes. Histamine and H₂R may therefore affect, via intracrine, autocrine, and paracrine pathways, various immune and inflammatory responses of the lymphoid and myeloid progenitors and lineages in the bone marrow and peripheral tissues.