Agonist‐induced desensitization of histamine Hi receptor‐mediated inositol phospholipid hydrolysis in human umbilical vein endothelial cells

Abstract

1 The regulation of histamine-induced [3H]-inositol phosphate formation was studied in human cultured umbilical vein endothelial cells (HUVEC).2 Histamine (ECm 4.8 iLM) produced a 12.7 fold increase in [3H]-inositol phosphate formation over basal levels. Prior exposure to 0.1 mM histamine (2 h) produced a 78% reduction in the response to subsequent histamine (0.1 mM) challenge. The IC5o for this histamine-induced desensitization was 0.9 ;LM.3 The inositol phosphate response to histamine (0.1 mM) was inhibited by phorbol dibutyrate (IC5o 40 nM; maximal reduction 64%). This effect was antagonized by both staurosporine (100 nM) and Ro 31-8220 (10 PM). However, the histamine-induced desensitization of the HI-receptor-mediated inositol phosphate response was insensitive to the protein kinase inhibitors, staurosporine, Ro 31-8220, K252a and KN62.4 Prior exposure to sodium nitroprusside (100 gM), forskolin (10 jiM) or dibutyryl cyclic AMP (1 mM) had no effect upon histamine-induced [3H]-inositol phosphate formation. 5NaF (20 mM) and thrombin (ECm 0.4 u ml-') also induced inositol phosphate formation in HUVEC.Histamine pretreatment (0.1 mM, 10-120 min) failed to modify the inositol phosphate response to a subsequent NaF or thrombin challenge. (Wojcikiewicz et al., 1993). The mechanism underlying these effects have been extensively studied using the P2-adrenoceptor as a model. For this receptor, short term (<1 h) exposure to agonist results in receptor desensitization which is mediated through two different mechanisms, involving adenosine 3': 5'-cyclic monophosphate (cyclic AMP)-dependent phosphorylation of specific sites in the third intracellular loop of the receptor (Lohse et al., 1990;Hausdorff et al., 1989;1990), and cyclic AMP-independent phosphorylation of residues in the cytoplasmic tail of the receptor by a specific family of receptor kinases named P-adrenoceptor kinases (BARK: Benovic et al., 1986;1987;Kolbilka, 1992;Ostrowski et al., 1992;Lefkowitz, 1993;Inglese et al., 1993).In the case of P-ARK, the phosphorylation of the P2-adrenoceptor is rapidly followed by the binding of a protein (0-arrestin 1 or 2) which interferes with the coupling of the receptor with its G-protein (Lefkowitz, 1993;Lohse et al., 1992). Sequestration (which is manifest by a loss of cell surface receptors to an intracellular compartment) quickly follows the more rapid uncoupling of p2-receptors from G,-proteins (Yu et al., 1993;Barak et al., 1994). Following agonist removal, sequestered receptors can be recycled to the cell surface (Yu et al., 1993). It has been suggested that receptor sequestration may represent a mechanism by which receptors can be dephosphorylated and recycled to re-establish normal responsiveness (Barak et al., 1994). Longer term exposure of Author for correspondence. the 2-adrenoceptor to agonists leads to an overall loss of cellular receptors (downregulation) as a result of receptor degradation via the lysosomes and altered receptor expression (Hadcock et al., 1989;Kolbilka, 1992).Less is known of the mechanisms...

Histamine receptor H1 is required for TCR-mediated p38 MAPK activation and optimal IFN-γ production in mice

“…Here we show, for the first time to our knowledge, that H 1 R gene expression is silenced early after the activation of CD4 + T cells. Modulation of H 1 R signaling, like that of other G protein-coupled receptors, is complex and includes receptor desensitization, internalization, and subsequent downregulation (41,42). Desensitization of H 1 R is induced by both agonist-specific (homologous) and agonist nonspecific (heterologous) pathways, mainly involving PKC-mediated phosphorylation of H 1 R (43,44).…”

Differential modulation of the phases of a Ca2+ spike by the store Ca2+‐ATPase in human umbilical vein endothelial cells

“…We assessed the degree of store emptying by examining the decline in the [Ca¥]é responses; maximal histamine responses were also measured before and after the sequence of pulses as another measure of store depletion. This protocol reduces the extent of any agonist receptor desensitization (unlikely since HUVEC histamine receptors desensitize over a matter of hours; McCreath et al 1994), but, more importantly, is likely to be a more efficient stimulus than continuous application by minimizing inactivation of release at the IP× receptor, as argued for caffeine at the ryanodine receptor . Also, where submaximal agonist stimulation selectively releases Ca¥ from a subpopulation of stores which is characterized by heightened sensitivity to Figure 3.…”

Bimodal Regulation of the Human H1 Histamine Receptor by G Protein-coupled Receptor Kinase 2

“…Numerous studies have demonstrated that both endogenously expressed as well as heterologously expressed H1HRs exhibit hyporesponsiveness/desensitization when exposed to either PKC-activating agents or histamine (7,(13)(14)(15)(16)(17)(18)(19) and that agonist-specific desensitization can be associated with H1HR internalization or down-regulation (14,18). However, beyond a basic appreciation that the H1HR desensitizes and internalizes, little is known regarding the mechanisms by which these processes are mediated.…”