Phorbol ester-mediated desensitization of histamine H1 receptors on a cultured smooth muscle cell line

Inhibition of H2 histamine receptor-mediated cation channel opening by protein kinase C in human promyelocytic cells

Histamine, through H(2) receptors, triggers a prominent rise in intracellular free Ca(2+) concentration ([Ca(2+)](i)) in addition to an elevation of cAMP level in HL-60 promyelocytes. Here we show that the histamine-induced [Ca(2+)](i) rise was due to influx of Ca(2+) from the extracellular space, probably through nonselective cation channels, as incubation of the cells with SKF 96365 abolished the histamine-induced [Ca(2+)](i) rise, Na(+) influx, and membrane depolarization. The Ca(2+) influx was specifically inhibited by pretreatment of the cells with PMA or extracellular ATP with 50% inhibitory concentrations of 0.12 +/- 0.03 nM and 185 +/- 17 microM, respectively. Western blot analysis of protein kinase C (PKC) isoforms revealed that PMA (< or =1 nM) and ATP (300 microM) caused selective translocation of PKC-delta to the particulate/membrane fraction. Costimulation of the cells with histamine and SKF 96365 partially reduced histamine-induced granulocytic differentiation, which was evaluated by looking at the extent of fMet-Leu-Phe-induced [Ca(2+)](i) rise and superoxide generation. In conclusion, nonselective cation channels are opened by stimulation of the H(2) receptor, and the channels are at least in part involved in the induction of histamine-mediated differentiation processes. Both effects of histamine were selectively inhibited probably by the delta isoform of PKC in HL-60 cells.

Opposing regulatory effects of protein kinase C on the cAMP cascade in human HL-60 promyelocytic leukemia cells

The functional role of protein kinase C in the cAMP signaling cascade was investigated in human promyelocytic leukemia (HL-60) cells. Protein kinase C activation after short exposure to 100 nM phorbol 12-myristate 13-acetate (PMA) increased the intracellular cAMP level up to 3- to 5-fold after 30 min. Such enhancement was almost completely blocked by the selective protein kinase C inhibitor bisindolylmaleimide (GF 109203X). In addition, PMA, but not 4-alpha-PMA, synergistically elevated cAMP levels when adenylyl cyclase was activated directly by forskolin or indirectly by G protein activation after cholera toxin treatment or guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) treatment in digitonin-permeabilized cells. The results indicate that protein kinase C directly increases adenylyl cyclase activity and synergistically enhances it, when it is simultaneously activated otherwise. On the other hand, a 10-min treatment with PMA cut the cAMP accumulation induced by histamine, prostaglandin E2, or isoproterenol by 50-70%. However, the binding affinity and total binding of [3H]histamine to membrane receptors was not effected by PMA, suggesting that the site of protein kinase C's action is not at the receptor level. Western blot analysis of protein kinase C isozymes revealed that PMA (100 nM) caused translocation of cytosolic protein kinase C such as alpha, beta and epsilon to the particulate/membrane fraction. Treatment with a lower concentration of PMA (10 nM) translocated the protein kinase C-epsilon within 2 min, while it had little effect on the translocation of protein kinase C-alpha and -beta up to 20 min. However, simultaneous treatment with 10 nM PMA plus histamine for 5 min significantly inhibited the histamine-mediated cAMP generation, indicating that the protein kinase C-epsilon could be involved in the inhibition of receptor-mediated cAMP generation. Taken together, we conclude that PMA, through the activation of protein kinase C, has two opposite effects on the cAMP signaling cascade in HL-60 cells: a direct activation of adenylyl cyclase and an inhibition of receptor-mediated signal transduction.

Increased desensitization by picomolar phorbol ester of the endothelium-mediated effect of histamine in the perfused rat mesenteric bed

The vasodilatatory, endothelium-mediated, effect of histamine (H), through H1 receptor, in the isolated and perfused mesenteric bed of the rat, undergoes strong desensitization during perfusion or repetitive injections of noradrenaline (NA) and H. The mesenteric bed completely desensitized to H is responsive to carbachol (C) and this latter compound does not affect the H desensitization. The homologous desensitization to C effect is very small, attaining less than 10% after 30 min of continuous perfusion. In this work the effect of inhibitors or activators of protein-kinase(s)-C (PKC) are studied during continuous perfusion of H or C in preparations preconstricted by NA. Staurosporine antagonizes the onset of the H desensitization, while the rate of desensitization in increased by phorbol-12-myristate-13-acetate (PMA). PMA, at a concentration from 10(-12) to 10(-10)M, selectively enhances the homologous desensitization of H, while at 10(-8)M it also produces a desensitization to C. At least two different PKC isoenzymes might be involved in the desensitization of the vasodilatatory effect of H and C in the isolated and perfused rat mesenteric bed.

Homologous and heterologous desensitization of histamine H1- and ATP-receptors in the smooth muscle cell line, DDT1MF-2: the role of protein kinase C

1. The possible role of protein kinase C (PKC) in homologous and heterologous desensitization of histamine H1- and ATP-receptors has been studied in monolayers of cultured vas deferens smooth muscle cells (DDT1MF-2). Cells were loaded with the calcium-sensitive fluorescent dye fura-2 and increases in intracellular free Ca2+ concentration ([Ca2+]i) monitored in response to histamine H1- or ATP-receptor activation. 2. Histamine and ATP stimulated the release of Ca2+ from intracellular Ca2+ stores and Ca2+ influx across the plasma membrane. Activation of PKC with the phorbol ester beta-phorbol-12,13 dibutyrate (PDBu; 1 microM) attenuated histamine (100 microM) and ATP (10 microM)-induced release of intracellular Ca2+ and Ca2+ influx. 3. The selective PKC inhibitor, Ro 31-8220 (10 microM), reversed the PDBu-induced attenuation of histamine (100 microM)-stimulated Ca2+ responses. 4. Histamine H1- and ATP-receptors are readily susceptible to homologous desensitization since short-term exposure to histamine or ATP (450 s) attenuated the Ca2+ responses elicited by a second application of the same agonist. Furthermore, H1-receptor activation-induced heterologous desensitization of ATP stimulated Ca2+ responses and vice versa. 5. Homologous and heterologous desensitization of histamine and ATP Ca2+ responses still occurred in the presence of the PKC inhibitor, Ro 31-8220 (10 microM). 6. These data suggest that PKC activation can attenuate histamine H1- and ATP-receptor mediated Ca2+ responses. However, based on our experimental data, PKC-independent mechanisms appear to be involved in the homologous and heterologous desensitization of histamine H1- and ATP-receptor mediated Ca2+ responses in DDT1MF-2 cells.

Desensitization of histamine H1 receptor-mediated inositol phosphate accumulation in guinea pig cerebral cortex slices

1. Histamine stimulated the production of [3H]-inositol phosphates in untreated (control) guinea-pig cerebral cortex slices with a best-fit EC50 of 17 +/- 4 microM, and a best-fit maximum response of 385 +/- 23% over basal accumulation. 2. Histamine pretreatment desensitized guinea-pig cortex slices to a subsequent challenge with histamine, which was observed as a reduction in the best-fit maximum response to 182 +/- 32% over basal accumulation. 3. The time-course for the histamine-induced production of [3H]-inositol phosphates was approximately linear over 90 min of stimulation in both control and histamine pretreated slices. The rate of production in pretreated slices was significantly slowed compared to control, such that by 90 min of histamine stimulation the desensitized slices produced 2.8 times the basal [3H]-inositol phosphate accumulation compared to 5.3 fold the basal [3H]-inositol phosphate accumulation in the control slices. 4. Displacement of [3H]-mepyramine binding to homogenates of guinea-pig cerebral cortex by mepyramine and histamine revealed that histamine pretreatment did not alter the apparent affinity of the H1 receptor for histamine (control Kd = 6.3 +/- 0.7 microM, desensitized Kd = 7.9 +/- 1.6 microM) or mepyramine (control Kd = 3.4 +/- 0.8 nM, desensitized Kd = 3.4 +/- 1.3 nM), nor was there any reduction in the calculated maximum number of [3H]-mepyramine binding sites (control Bmax = 192 +/- 31 fmol mg-1 protein, desensitized Bmax = 220 +/- 50 fmol mg-1 protein). 5. The histamine-mediated desensitization of response in guinea-pig slices was mediated by the HI receptor subtype, since the attentuated maximum histamine-stimulated [3H]-inositol phosphate accumulation could not be prevented by inclusion of an H2- (ranitidine) and an H3- (thioperamide) receptor antagonist during the pretreatment period.6. The desensitized histamine-stimulated [3H]-inositol phosphate accumulation recovered to 90% of control levels over a period of 150 min after the removal of the conditioning dose of histamine, with a half-time of recovery of about 95 min.

Desensitization of histamine H1 receptor-mediated inositol phosphate production in HeLa cells

1. Histamine stimulated the accumulation of total [3H]-inositol phosphates (IPn) in control HeLa cells with an EC50 of 3.7 +/- 0.7 microM in the presence of 10 mM LiCl. The maximum response to histamine after 15 min incubation was 43 +/- 5% over basal accumulation and occurred at a concentration of 1 mM histamine. 2. The histamine-induced IPn production in HeLa cells was confirmed as H1 receptor-mediated, since the H1 antagonist mepyramine (10(-6) M) inhibited the histamine response (10(-4) M) by 83 +/- 7%, whereas the H2 antagonist, ranitidine (10(-4) M), and H3 antagonist, thioperamide (10(-6) M), were ineffective. 3. Histamine (10(-4) M) pretreatment of HeLa cells for 30 min desensitized the subsequent histamine-induced IPn accumulation. The desensitized cells accumulated IPn in response to histamine with an EC50 of 1.7 +/- 0.7 microM after 15 min incubation. The maximum histamine-induced IPn accumulation at 10(-4) M was 19 +/- 5% over basal and was significantly lower (P < 0.03) than the maximum response in control cells. 4. The desensitization of histamine-induced IPn accumulation was time-dependent and, at a desensitizing histamine concentration of 10(-4) M, the half-maximal attenuation occurred after approximately 9 min and maximum desensitization was achieved by 15-20 min. The desensitization of the IPn accumulation was a reversible phenomenon and full recovery of the response occurred 150 min after the removal of the desensitizing histamine-containing medium. The half-time for the recovery of the histamine-induced response was estimated at 120 min. 5. Bradykinin stimulated IPn, accumulation in HeLa cells, and the ECm in control cells of 1.9 +/- 0.2 nM was not significantly different from the EC50 value from histamine-pretreated cells of 1.6 +/- 0.9 nM. The bradykinin response at 1 microM was 194 +/- 48% over basal IPn accumulation in control cells and this value was significantly different (P <0.04) from the 1 microM bradykinin-induced IPn accumulation in histamine pretreated HeLa cells of 143 +/- 38% over basal.6. NaF stimulated IP,, accumulation in control HeLa cells in a dose-related manner, with the maximum effect occurring at 15-20 mM. The EC50 value for NaF-stimulated IPn accumulation in control cells was 10.5 +/- 1.1 mm and the maximum response was 136 +/- 41% over basal after 20 min incubation. In histamine desensitized HeLa cells the EC50 value for NaF was 12.3 +/- 0.4 mM after 20 min stimulation,which was not significantly different from the value obtained in control cells. The maximum NaF stimulated IPn formation in desensitized cells of 68 +/- 23% over basal occurred at 15 -20 mM and was significantly lower (P<0.01) than that obtained in control cells.7. We show here that the acute histamine pretreatment of HeLa cells results in the desensitization of histamine H1 receptor-mediated IPn production. The desensitization was not restricted to the H1 receptor-mediated signal transduction pathway, but also includes both the bradykinin- and NaF mediated responses, supporting a heterologous desensitization mechanism. Our results are consistent with the site of attenuation being at or distal to the G-protein and the underlying mechanism being a slowed time-course for the production of inositol phosphates.

Desensitization of histamine H1 receptor-mediated cyclic GMP production in guinea-pig lung

Histamine H1 receptor-mediated production of cGMP in guinea-pig lung tissue becomes rapidly desensitized after previous exposure to histamine. This desensitization is clearly concentration dependent and appears to be homologous. Responses to histamine are also inhibited by previous treatment with phorbol 12,13-dibutyrate. Yet, the time course of the inhibition is considerably slower and the maximal inhibition is significantly less compared to receptor desensitization. Moreover, the effects of the phorbol ester are not confined to H1 receptor responses. Since the effects of receptor desensitization are also not prevented by several protein kinase C inhibitors, the development of homologous H1 receptor desensitization is not dependent upon protein kinase C activation, but is caused by a yet unidentified mechanism.

Voltage-dependent sodium and potassium, but no calcium conductances in DDT1 MF-2 smooth muscle cells

Voltage-dependent inward and outward membrane currents were investigated in the DDT1 MF-2 smooth muscle cell line using the whole-cell patch-clamp technique. Application of a pulse protocol with subsequent depolarizing voltage steps elicited an inactivating inward current and a non-inactivating outward current. The outward current was activated at membrane potentials more positive than -35 mV, with tau act = 30 -40 ms. The outward current was blocked by tetraethylammonium (NEt4Cl) and 3,4-aminopyridine in a dose-dependent manner (EC50 of 5 mM and 0.5 mM, respectively). The amplitude of the outward current was linked to the potassium equilibrium potential (Vek), and tail currents reversed near Vek. The outward current was completely abolished when intracellular potassium was substituted by 106 mM caesium and 20 mM NEt4Cl. The inward current was activated at potentials more positive than -30 mV with tau act of 1.6-2.5 ms, and with tau inact of 1.7-3.0 ms. Steady-state inactivation was 50% at a holding potential of -40 mV. The inward current was blocked by tetrodotoxin (EC50 of 0.15 microM) and dependent on the reversal potential for sodium. Voltage-dependent calcium currents could not be detected. Further, the cytoplasmic free calcium concentration, as measured using Indo-1 fluorescence, was not changed during high-potassium (40 mM)-induced depolarization. In contrast, contraction of freshly obtained hamster vas deferens tissue elicited by high-potassium(40 mM)-induced depolarization was largely inhibited by diltiazem (20 microM). These findings showed that voltage-dependent calcium channels are not functional in DDT1 MF-2 smooth muscle cells in contrast to freshly obtained Syrian hamster vas deferens smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in histamine receptors of guinea-pig ileal smooth muscle produced during agonist-induced desensitization

1. The effects of prolonged treatment with histamine (10(-4) M, 30 min) on desensitization at histamine H1-receptors of guinea-pig ileal longitudinal muscle were investigated. 2. This treatment did not change either the maximum amount or dissociation constant (Kd) of [3H]-mepyramine binding to membranes of guinea-pig ileal muscle. 3. In contrast, this treatment shifted the histamine inhibition curves of [3H]-mepyramine binding to the right both in the presence and absence of 0.5 mM guanosine-5'-triphosphate (GTP). This rightward shift of the curves occurred rapidly in the first 10 min of exposure to histamine. 4. The histamine inhibition curves were analyzed with a two binding sites model. It was shown that the histamine-induced affinity change of the receptor for the agonist occurred with the high affinity binding component (which comprise about 80% of the total), whereas no significant change occurred with the low affinity component. The GTP-dependent decrease in the affinity of the receptor for the agonist also occurred with the high affinity component both in control and histamine-treated preparations. 5. These studies suggest that histamine-induced desensitization was caused by alteration in the affinity of the receptor for the agonist rather than reduction in the number of the receptors and that the interaction of the receptor with a guanine nucleotide regulatory protein was retained in the desensitized state.

ET-1 receptors in C-6 cells: homologous down-regulation and modulation by protein kinase C

Endothelin (ET-1) receptors were studied in the C-6 glia cell line. ET-1 binds to C-6 cells in a temperature- and time-dependent manner, with an apparent Kd of 1.16 +/- 0.07 10(-10) M and a Bmax of 96,500 +/- 6000 sites/cell (mean +/- SEM, n = 27). Stimulation of protein kinase C (PKC) with the diacylglycerol (DAG) analog phorbol 12-myristate 13-acetate (PMA) resulted in a decrease in the number of receptors in a dose-dependent manner. Inhibition of PKC with H-7 eliminated the effect of PMA on the reduction of binding sites. Treatment with exogenous 1-oleoyl-2-acetyl-sn-glycerol (OAG) and 1,2-dioctanoyl-sn-glycerol (DOG), release of endogenous DAG with phospholipase C, and inhibition of the metabolism of DAG with the diacylglycerol kinase inhibitor R 59022 also resulted in a decrease in the number of receptors. The effect of these agents was inhibited by H-7. ET-1-mediated down-regulation of receptors was also demonstrated, but the down-regulation was not affected by H-7 or by depletion of cellular PKC with chronic, high dose of PMA. Internalization constants of ET-1-receptor complex was also measured according to the model of Wiley and Cunningham (Cell 25 (1981) 433). PMA- and ET-1-mediated down-regulation of receptors was associated with an increase in the endocytosis constant for the hormone-receptor complex and a decrease in the rate of insertion of receptor into the plasma membrane. PMA, but not ET-1, increased the rate of endocytosis of unoccupied receptors. Radioiodinated ET-1 was crosslinked to the receptor after binding, extracted and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A band at 66 kDa was obtained. These studies show that ET-1 and PKC activation produce down-regulation of ET-1 membrane receptors and that ET-1-mediated down-regulation probably does not involve the activation of PKC.

Regulation of histamine H1 receptor-mediated phosphoinositide hydrolysis by histamine and phorbol esters in DDT1 MF-2 cells

The regulation of histamine-stimulated phosphoinositide turnover by histamine and phorbol esters was examined in intact DDT1 MF-2 cells grown in suspension culture. Histamine increased the incorporation of 32P into phosphatidylinositol (PI) in these cells, and this stimulation was inhibited by the H1 antagonist diphenhydramine but not by the H2 antagonist cimetidine. Pretreatment of cells with histamine or with phorbol 12-myristate 13-acetate (PMA) or other activators of protein kinase C induced a marked decrease in the subsequent stimulation by histamine. PMA, but not histamine, also decreased the ability of epinephrine to stimulate PI labelling through alpha 1-adrenoceptors. Thus, histamine appears to induce homologous desensitization of histamine H1 receptor-mediated PI turnover, whereas direct activation of protein kinase C in the absence of receptor occupancy by agonist induces nonspecific heterologous desensitization of both histamine H1- and alpha 1-adrenoceptor-mediated responses.

Histamine receptors in human fibroblasts: inositol phosphates, Ca2+, and cell growth

Histamine stimulated inositol phosphate formation by human skin fibroblasts. The effect of histamine was reduced but still readily apparent in the absence of extracellular Ca2+. Histamine caused a transient increase in intracellular free Ca2+ as detected by indo-1 and fura-2 fluorescence studies on cell populations and on individual cells. Similar increases were observed in the absence of extracellular Ca2+, indicating that the effect was primarily due to mobilization of Ca2+ from intracellular stores, presumably by inositol trisphosphate (IP3). The effects of histamine on phosphoinositide metabolism and intracellular Ca2+ were inhibited by pretreatment of the cells with phorbol esters, suggesting that the histamine receptor in fibroblasts is subject to feedback regulation by protein kinase C. Histamine inhibited the incorporation of [3H]-thymidine into DNA. The effects of histamine on inositol phosphate formation, intracellular Ca2+, and thymidine incorporation were blocked by the H1 receptor antagonist mepyramine. Our results indicate that human skin fibroblasts have H1 receptors coupled to the formation of inositol phosphates and mobilization of intracellular Ca2+. We suggest that this H1 receptor also mediates a block of the cell cycle and that histamine may play a physiological role in the regulation of fibroblast proliferation.

Angiotensin II and phorbol-esters potently down-regulate endothelin (ET-1) binding sites in vascular smooth muscle cells

[125I]ET-1 binding to vascular smooth muscle cells showed an apparent single class of high affinity recognition sites with a Kd of 2.12 +/- 0.46 nM and a Bmax of 81.2 +/- 5.2 fmol/10(6) cells. The specific binding was equally and totally displaced by ET-1 and ET-2 whereas ET-3 presented a different pattern. We investigated heterologous regulation of ET-1 binding sites by preincubating the cells with angiotensin II (AII), Arg-vasopressin, bradykinin, enkephalins, serotonin, norepinephrine and carbachol, for 18 h at 37 degrees C. Only AII pretreatment resulted in an important and dose-dependent decrease of ET-1 binding capacity. Sar1-Ile8-AII inhibited the regulatory effect of AII. Furthermore, preexposure of the cells with phorbol-12,13 dibutyrate but not with phorbol-12,13 didecanoate also resulted in a concentration-dependent diminution of ET-1 binding sites. These findings suggest that AII may selectively down-regulate ET-1 binding sites in vascular smooth muscle cells by a mechanism involving protein kinase C.

Molecular and cellular analysis of histamine H1 receptors on cultured smooth muscle cells

Histamine is an important mediator of immediate hypersensitivity for both animals and humans. The action of histamine on target tissues is believed to be mediated by specific cell surface receptors, especially H1 and H2 receptors for hypersensitivity and inflammatory reactions, which involve stimulation of smooth muscle contractility, alterations in vascular permeability, and modifications in the activities of macrophages and lymphocytes. Although the nature of histamine receptors in the brain and peripheral tissues has been studied extensively by many laboratories, the molecular mechanism of histamine receptor-mediated reactions is not fully understood, mainly because histamine receptors are incompletely characterized from the biochemical point of view. In previous studies, we have found that the cultured smooth muscle cell line DDT1MF-2, derived from hamster vas deferens, expresses low-affinity histamine H1 receptors and responds biochemically and functionally to H1-specific stimulation (Mitsuhashi and Payan, J Cell Physiol 134:367, 1988). This cell line provides a model for analyzing the biochemical responses of H1 receptor-mediated reactions in peripheral tissues. In this review, we summarized our recent progress in the study of low-affinity H1 receptors on DDT1MF-2 cells.