22 Histamine type 1(H) receptor radioligand binding studies in T cells from normal and atopic subjects

Histamine H1-receptors in HL-60 monocytes are coupled to Gi-proteins and pertussis toxin-insensitive G-proteins and mediate activation of Ca2+ influx without concomitant Ca2+ mobilization from intracellular stores

“…The results of binding studies suggest that human monocytes possess Hi-receptors (Cameron et al 1986;Driver et al 1989). Hi-receptors mediate activation of phospholipase C with subsequent Ca 2+ mobilization from intracellular stores (Hill 1990).…”

“…Occupation with agonist of Hi-receptors in HL-60 neutrophils results in the activation of phospholipase C with subsequent Ca 2+ mobilization from intracellular stores and Ca z+ influx through non-selective cation (NSC) channels ). The results of binding studies suggest that human monocytes possess H~-receptors as well, but it is not known whether these receptors are functionally active (Cameron et al 1986;Driver et al 1989). This prompted us to study the effects of HA on [Ca2+]i and 0 2 formation in HL-60 cells differentiated towards monocytes with la,25-dihydroxycholecalciferol (la,25(OH)zD3) (Ostrem et al 1987;Hruska et al 1988).…”

Histamine inhibits the production of interleukin-12 through interaction with H2 receptors.

“…Signaling through the H 1 receptor involves the activation of PLC, leading to the generation of 1,4,5-inositol phosphate and DAG, whereas H 2 receptor stimulation results in cAMP generation (22, 23). H 1 and H 2 receptors are expressed on many cell types, including lymphoid cells (24)(25)(26). The immune modulating effects of histamine include inhibition of IL-2 and IFN-␥ production by T cells and inhibition of TNF-␣ and IL-1 production by monocytes (27)(28)(29).…”

Oligomerization of Recombinant and Endogenously Expressed Human Histamine H4Receptors

“…The H 1 R is a well-known target for the treatment of seasonal allergies but has also been shown to mediate inflammatory responses in keratinocytes (Giustizieri et al, 2004;Matsubara et al, 2005). The H 1 R is ubiquitously expressed and is coexpressed together with the H 4 R in leukocytes, including monocytes and T lymphocytes (Cameron et al, 1986;Morse et al, 2001), suggesting that on these cells, histamine may modulate inflammatory actions through the action on both H 1 Rs and H 4 Rs. We therefore investigated the potential homo-oligomerization of the H 4 R and the heterooligomerization of the H 1 R with the H 4 R using heterologous expression systems.…”