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Hypertension. 1995;25:180-185

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(Hypertension. 1995;25:180-185.)
© 1995 American Heart Association, Inc.


Articles

Inhibition of Endothelial Nitric Oxide Synthase Activity by Protein Kinase C

Ken-ichi Hirata; Ryohei Kuroda; Tsuyoshi Sakoda; Masaya Katayama; Nobutaka Inoue; Masakuni Suematsu; Seinosuke Kawashima; Mitsuhiro Yokoyama

From the First Department of Internal Medicine, Kobe (Japan) University School of Medicine.


*    Abstract
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*Abstract
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Abstract Nitric oxide (NO) is an important molecular messenger accounting for endothelium-derived relaxing factor. Recently, NO synthase (NOS) from cultured endothelial cells has been purified and molecularly cloned. To evaluate the effect of phosphorylation by protein kinase C (PKC) and cyclic AMP–dependent protein kinase (PKA) on endothelial constitutive NOS catalytic activity, we incubated purified endothelial NOS with PKC or PKA. Endothelial NOS was stoichiometrically phosphorylated by PKC and PKA. In intact bovine aortic endothelial cells (BAECs), NOS was phosphorylated by stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA). NOS activity measured by the conversion of [3H]arginine to [3H]citrulline in homogenates of BAECs treated with TPA or phorbol 12,13-dibutyrate was reduced by 30%, whereas dibutylyl cyclic AMP did not affect NOS activity. Moreover, we measured NO release from cultured BAECs by a chemiluminescence method to examine the effect of PKC and PKA on endothelial NOS activity. In cultured BAECs, ATP{gamma}S and A23187 induced NO release in time- and dose-dependent manners. Phorbol esters such as TPA and phorbol 12,13-dibutyrate dose dependently inhibited NO release stimulated by A23187 as well as ATP{gamma}S. Reduction of NO release by TPA was almost completely prevented by pretreatment with staurosporine, an inhibitor of PKC. NO release by A23187 was increased in PKC-downregulated BAECs. In contrast, dibutylyl cyclic AMP or 8-bromo cyclic GMP had no effect on NO release from BAECs induced by A23187 or ATP{gamma}S. These results indicate that phosphorylation of NOS by PKC is associated with a reduction of its catalytic activity in vascular endothelial cells.


Key Words: nitric oxide • endothelium • protein kinase C


*    Introduction
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up arrowAbstract
*Introduction
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down arrowDiscussion
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Nitric oxide (NO) is a labile intracellular messenger molecule and is synthesized in diverse mammalian tissues. Endothelial NO accounts for the biological activity of endothelium-derived relaxing factor (EDRF)1 2 and plays an important role in the regulation of vascular tone and platelet aggregation.3 4 NO is generated from the terminal guanidino nitrogen of L-arginine through the action of NO synthase (NOS).5 6 Recently, several types of NOS have been purified and cloned not only in endothelium7 8 9 10 11 12 but also in cerebellum,13 14 macrophages,15 16 17 smooth muscle,18 and hepatocytes.19 NOS exists as at least three isoforms; two of them are calcium/calmodulin–dependent NOS and are constitutively present in endothelium and cerebellum, and the other is inducible-type NOS and is calcium/calmodulin independent except one in hepatocytes.

The activity of endothelial constitutive NOS is mainly regulated by Ca2+/calmodulin in the presence of (6R)-5,6,7,8-tetrahydrobiopterin (BH4), NADPH, and flavin adenine dinucleotide as cofactors. Agonists that release endothelial NO share in common an ability to activate phospholipase C. This activation produces two distinct second messengers: inositol 1,4,5-triphosphate (IP3), which elevates cytosolic free calcium, and diacylglycerol, which activates protein kinase C (PKC).20 21 The deduced primary structure of endothelial NOS cDNA is noted to contain consensus sequences for phosphorylation by protein kinases including PKC and cyclic AMP (cAMP)–dependent protein kinase (PKA). It is proposed that NOS phosphorylation has an important role in the regulation of NO production in the brain. Recently, it has been suggested that purified rat brain NOS is stoichiometrically phosphorylated by PKC and phosphorylation by PKC reduces NOS catalytic activity.22 Although some pharmacological experiments show that PKC activation by phorbol ester inhibits endothelium-dependent relaxation, the influence of NOS phosphorylation by protein kinases on NOS activity remains uncertain in vascular endothelial cells. The aim of the present study was to clarify the effect of phosphorylation of NOS on its enzyme activity. We demonstrated that endothelial NOS was phosphorylated by PKC and PKA and that phosphorylation by PKC reduced NOS catalytic activity in intact bovine aortic endothelial cells (BAECs).


*    Methods
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up arrowIntroduction
*Methods
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Materials
[{gamma}-32P]ATP and [3H]arginine were purchased from Du Pont–New England Nuclear, and [32P]orthophosphoric acid was purchased from Amersham. Purified PKC from rat brain was a generous gift from Dr Nishizuka (Kobe University, Japan). The catalytic subunit of PKA was purified from rabbit skeletal muscle as described.23 BH4 was purchased from Research Biochemicals Inc. EGTA was purchased from Dojindo. All other reagents were obtained from Sigma Chemical Co.

Cell Culture
BAECs were obtained by scraping the internal surface of the aorta excised from a freshly slaughtered cow with a knife, as previously described.24 25 26 Cells were cultured in Dulbecco's modified Eagle's medium (DMEM) with 15% fetal calf serum (FCS). The cells were seeded on a 25-cm2 flask and incubated at 37°C under an atmosphere of 5% CO2/95% air. The medium was changed on the following day and every 3 days thereafter. After 4 or 5 days, the primary cultures formed a confluent monolayer and could be subcultured. The cells were separated for subculture with 0.25% trypsin solution containing 0.02% EDTA. Cultures used in the present study were from the fifth to 15th passages. BAECs were plated at a density of approximately 1x106 cells onto 60-mm dishes in DMEM with 15% FCS. After 2 days the cultured cells reached confluence. Then the medium was replaced with DMEM with 0.1% bovine serum albumin, and cells were further incubated for 18 hours for experiments of NO release or assay of NOS activity in homogenates. The final cell density on the day of assay was 3x106 cells per dish.

In Vitro NOS Phosphorylation
NOS was purified from the particulate fraction of cultured BAECs as described.8 27 Briefly, the crude homogenate of BAECs in homogenization buffer A (50 mmol/L Tris-HCl, pH 7.4, containing 1 mmol/L EGTA, 1 mmol/L dithiothreitol, 1 µmol/L p-amidinophenylmethanesulfonyl fluoride, 1 µmol/L pepstatin A, and 2 µmol/L leupeptin) was centrifuged at 100 000g for 60 minutes. The particulate fraction resuspended in homogenization buffer B (buffer A containing 10% glycerol, and 1 mmol/L KCl) was solubilized with 20 mmol/L 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS). The CHAPS extract was loaded on an adenosine 2', 5'-bisphosphate–coupled Sepharose column (Pharmacia) and eluted with 10 mmol/L NADPH. The eluate was used as NOS with approximately 60% purity. NOS (20 µg/mL) was phosphorylated by incubation with the catalytic subunit of PKA or PKC in 50 mmol/L Tris-HCl at pH 7.4 containing 50 µmol/L [{gamma}-32P]ATP and 10 mmol/L MgCl2 at 30°C for various times. When NOS was phosphorylated by PKC, 1 mmol/L CaCl2, 8 µg/mL phosphatidylserine, and 0.8 µg/mL diolein were added to the reaction mixture. The final concentrations of phosphorylating enzyme were 1 and 2 µg for PKC and the catalytic subunit of PKA, respectively. The specific activities of the purified kinases were 2 and 1 µmol/mg per minute for PKC and PKA, respectively, using histone H1 as the phosphorylation substrate. Final incubation volume was 100 µL. An aliquot of 40 µL each was subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) as described by Laemmli.28 Gels were stained with Coomassie blue, dried, and subjected to autoradiography. Incorporation of 32P into NOS was measured with a Bioimage Analyzer BAS 2000 (Fuji Film).

In Vivo Phosphorylation by PKC
Confluent BAECs in 100-mm dishes were incubated in 2 mL phosphate-free DMEM with 200 µCi/mL [32P]orthophosphoric acid for 4 hours and exposed to 100 nmol/L 12-O-tetradecanoylphorbol-13-acetate (TPA) for 15 minutes. After a 15-minute incubation with TPA, cells were homogenized in 50 mmol/L Tris-HCl, pH 7.4, containing (mmol/L) NaF 50, pyrophosphate 10, EDTA 1, EGTA 1, and orthovanadate buffer 1; sonicated; and incubated with ADP Sepharose (4 mg) for 1 hour at 4°C. The sample was centrifuged at 1000g for 3 minutes, and the precipitates were subjected to 7.5% SDS-PAGE followed by autoradiography.

Assay for NOS
NOS activity in BAECs was quantified by monitoring the conversion of [3H]arginine to [3H]citrulline as described.8 13 27 For NOS assay, samples were incubated with 100 µmol/L L-[2,3,4,5-3H]arginine for 5 minutes at 25°C in a solution of 50 mmol/L Tris-HCl at pH 7.4, 1 mmol/L EGTA, 1 mmol/L dithiothreitol, 1 mmol/L NADPH, 300 µmol/L calmodulin, 2 mmol/L CaCl2, 10 µmol/L BH4, and 1 µmol/L flavin adenine dinucleotide in a final volume of 100 µL. The reaction was stopped by addition of 0.5 mL of a stopping buffer (2 mmol/L EGTA and 20 mmol/L HEPES at pH 5.5). The whole solution was then applied to a 1-mL Dowex AG 50WX-8 column (Na+ form, Bio-Rad) that had been preequilibrated with the stopping buffer. L-[2,3,4,5-3H]Citrulline was eluted twice with 0.5 mL distilled water, and radioactivity was determined with a liquid scintillation system (model LS3801, Beckman Instruments).

Effect of Phosphorylation on NOS Catalytic Activity in BAECs
BAECs in a 60-mm dish were rinsed twice with 2 mL physiological saline solution (PSS) composed of (mmol/L) NaCl 130, CaCl2 1.5, KCl 5, MgCl2 1, glucose 10, and HEPES 20 (pH 7.4) and were incubated with 2 mL PSS at 37°C with or without TPA (100 nmol/L), phorbol 12,13-dibutyrate (PDBu) (100 nmol/L), and dibutylyl cAMP (Db-cAMP) (10 µmol/L). After 15 minutes of incubation, PSS was aspirated and cells were scraped and homogenized in 1 mL homogenization buffer A. Homogenates were sonicated for 20 seconds twice, and NOS catalytic activity was quantified in homogenates by measuring the conversion of [3H]arginine to [3H]citrulline as described above.

Assay Condition for NO Release in BAECs
At the time of study, the BAECs in 60-mm dishes were rinsed twice with 2 mL PSS and incubated with 2 mL PSS at 37°C with various drugs as follows. For determination of the effect of PKC activation on NO release, cells were preincubated with phorbol esters, such as TPA (0 to 50 nmol/L) and PDBu (0 to 50 nmol/L), for 5 minutes, and 1 µmol/L A23187 or 10 µmol/L ATP{gamma}S was added in the presence of TPA or PDBu; cells were then incubated for 60 minutes. In some experiments, cells were preincubated with staurosporine (50 nmol/L) for 5 minutes before TPA (50 nmol/L) was added. For determination of the effect of cAMP and cGMP on NO release, cells were preincubated with Db-cAMP (0.1 µmol/L to 0.1 mmol/L) or 8-bromo-cGMP (0.1 µmol/L to 0.1 mmol/L) for 5 minutes before various agonists were added. For determination of the effect of downregulating PKC activity on NO release, cells were incubated with PDBu (100 nmol/L) at 37°C under an atmosphere of 5% CO2/95% air for 18 hours in the absence of FCS and then stimulated with 1 µmol/L A23187. After incubation, a 1-mL aliquot was used to measure NO release by chemiluminescence. To standardize the protein concentration, BAECs were solubilized with 1 mL of 1N NaOH for protein determination.

Measurement of NO Release by Chemiluminescence
NO release from cultured BAECs was measured by examining the production of nitrite, the stable degradation product of NO, with an NOx analyzer.29 30 The injected samples were carried by a continuous stream of deoxygenated water into a reflux chamber containing 1% NaI and glacial acetic acid. The samples were exposed to this reducing environment to degrade NO-containing compounds and reduce nitrite to release NO gas. Any released NO was then carried into the NOx analyzer by a stream of nitrogen gas under vacuum within the analyzer, and the gas was mixed with ozone in a reaction chamber. Ozone and NO spontaneously react to release light at a wavelength of 650 to 800 nm, and the amount of light was measured by a photomultiplier tube. NO3- was not reduced in this system and was undetectable.

Determinations
Protein concentrations were determined with bovine serum albumin as a standard protein as described.31 Results are expressed as mean±SEM. Statistical evaluation of the data was performed by Student's t test for unpaired observation. When more than two groups were compared, the significance of the difference between group means was analyzed by one-way ANOVA and the Bonferroni test for samples. Values were considered to be statistically different at a value of P<.05.


*    Results
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up arrowMethods
*Results
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Phosphorylation of NOS
We incubated purified NOS with PKA or PKC together with [{gamma}-32P]ATP for varying times and monitored radioactivity by autoradiography after SDS-PAGE (Fig 1). PKA and PKC phosphorylated NOS. With these enzymes, substantial label was incorporated into NOS in a time-dependent fashion (Fig 1B) and appeared to be nearly stoichiometric with one molecule of 32P/NOS monomer. For PKC, no phosphorylation could be demonstrated when phosphatidylserine or diolein was deleted. Incubation of intact BAECs with TPA for 15 minutes to activate the endogenous PKC resulted in incorporation of 32P into NOS purified by ADP Sepharose from these cells (Fig 2). To assess the influence of phosphorylation on NOS catalytic activity, we incubated NOS enzyme alone or with PKC or PKA for 15 minutes at 30°C. When purified NOS was incubated by itself or with phosphorylating enzyme at 30°C, NOS activity declined by 40% and 45%, respectively, at 15 minutes after incubation. Thus, in vitro the effect of phosphorylating enzymes on NOS activity could not be determined.



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Figure 1. Phosphorylation of nitric oxide synthase (NOS) by protein kinase C (PKC) and cyclic AMP–dependent protein kinase (PKA). Purified NOS was phosphorylated by PKC and PKA at 30°C, and proteins were separated by 7.5% sodium dodecyl sulfate–polyacrylamide gel electrophoresis. A, Autoradiography revealed NOS phosphorylation band by incubation with PKC in a time-dependent manner. B, Line graph shows quantification of radioactive 32P associated with NOS by PKC ({bullet}) and PKA ({circ}). NOS phosphorylation by PKC and PKA was nearly stoichiometric with respect to each NOS monomer. Results are expressed as mean±SEM of three independent experiments.



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Figure 2. Blot shows phosphorylation of endothelial nitric oxide synthase (NOS) in intact bovine aortic endothelial cells (BAECs) stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA). Cultured BAECs were prelabeled with 200 µCi/mL [32P]orthophosphoric acid for 4 hours and then exposed to 100 nmol/L TPA or its vehicle for 15 minutes. BAECs were homogenized, and partially purified NOS was separated by 7.5% sodium dodecyl sulfate–polyacrylamide gel electrophoresis, stained with Coomassie blue, and analyzed by autoradiography. Detailed procedures are described under "Methods." Lane 1, control; lane 2, TPA (100 nmol/L). Western blotting for endothelial NOS revealed that endothelial NOS protein was not altered by treatment with TPA.

In a parallel experiment, we measured NOS catalytic activities in homogenates of BAECs treated with Db-cAMP (10 µmol/L), TPA (100 nmol/L), or PDBu (100 nmol/L). Fig 3 shows NOS activity in homogenates treated with Db-cAMP, TPA, and PDBu compared with that in homogenates of untreated BAECs. Db-cAMP had no effect on NOS activity, whereas TPA and PDBu reduced enzyme activity by 30% and 27%, respectively. Total NOS expression was measured in BAECs by Western blotting following treatment with Db-cAMP, TPA, and PDBu. Treatment with these agents did not alter the total expression of NOS (data not shown).



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Figure 3. Bar graph shows regulation of nitric oxide synthase (NOS) catalytic activity by activation of protein kinase A (PKA) and cyclic AMP–dependent protein kinase (PKC). Stimulation of NOS phosphorylation in bovine aortic endothelial cells (BAECs) was done by addition of 12-O-tetradecanoylphorbol-13-acetate (TPA), PDBu, and dibutylyl cyclic AMP (Db-cAMP) to activate PKC and PKA, respectively. NOS activity quantified in homogenates from treated BAECs showed Db-cAMP having no effect, 100 nmol/L TPA causing a 30% reduction, and 100 nmol/L PDBu causing a 27% reduction in NOS activity. NOS activity in BAECs without stimulation was determined as 100% NOS activity. Amount of generated citrulline at 100% NOS activity was 4.81 pmol/mg protein per minute. Results are expressed as mean±SEM of five independent experiments. *P<.05 compared with NOS activity without stimulation. No indicates nitric oxide.

Nitrite Release From BAECs
In this chemiluminescence system, a standard curve for more than 100 pmol nitrite was obtained in response to infusion of standard quantities of sodium nitrite. NOx signals linearly increased with the concentration of sodium nitrite (data not shown). Fig 4A shows the time course of nitrite release from BAECs stimulated by 1 µmol/L A23187 and 10 µmol/L ATP{gamma}S. Nitrite release from BAECs increased linearly with incubation time. Fig 4B shows the concentration response relation for nitrite release stimulated by A23187 and ATP{gamma}S for 60 minutes. The threshold concentration and half-maximal effective concentration value of A23187 were 10 nmol/L and 1 µmol/L, respectively, and those of ATP{gamma}S were 100 nmol/L and 10 µmol/L. To examine the effect of PKC on nitrite release, we measured nitrite release by stimulation of 1 µmol/L A23187 or 10 µmol/L ATP{gamma}S for 60 minutes from BAECs pretreated with TPA (0 to 50 nmol/L). The nitrite release stimulated by A23187 and ATP{gamma}S in 50 nmol/L TPA-pretreated BAECs was reduced by 55% (from 1195±42 to 532±74 pmol/mg protein) and 53% (from 853±38 to 398±51 pmol/mg protein), respectively. The reduced nitrite release by TPA (50 nmol/L) was almost completely reversed by the further pretreatment with staurosporine (50 nmol/L), a PKC inhibitor (Fig 5).



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Figure 4. Line graphs show time course (A) and concentration response (B) of A23187-induced ({circ}) and ATP{gamma}S-induced ({bullet}) accumulation of nitrite release from bovine aortic endothelial cells (BAECs). BAECs were incubated with 1 µmol/L A23187 and 10 µmol/L ATP{gamma}S. Incubation time varied from 0 to 90 minutes. BAECs were incubated for 60 minutes with A23187 and ATP{gamma}S at the concentration shown. Results are expressed as mean±SEM of five independent experiments.



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Figure 5. Line graphs show effect of protein kinase C (PKC) on release of nitrite from bovine aortic endothelial cells (BAECs). We examined the effect of PKC on accumulation of nitrite release induced by 1 µmol/L A23187 (A) and 10 µmol/L ATP{gamma}S (B) for 60 minutes from BAECs. BAECs were preincubated for 5 minutes with 12-O-tetradecanoylphorbol-13-acetate (TPA) at the concentrations shown before addition of agonists ({bullet}). BAECs were further preincubated with staurosporine (50 nmol/L), a PKC inhibitor, for 5 minutes before addition of TPA ({circ}). Similar results were obtained for the accumulation of nitrite release after treatment with PDBu. Results are expressed as mean±SEM of five independent experiments. *P<.05, **P<.01 compared with nitrite release without TPA.

To examine the effect of downregulating PKC activity on nitrite release, we measured nitrite release stimulated by A23187 in BAECs preincubated for 18 hours with or without PDBu (100 nmol/L). The nitrite release from PKC-downregulated cells showed an approximately twofold increase compared with control (2112±163 versus 1160±123 pmol/mg protein, P<.001) (Fig 6).



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Figure 6. Bar graph shows effect of downregulating PKC activity on nitrite release from bovine aortic endothelial cells (BAECs). We measured the accumulation of nitrite release induced by A23187 for 60 minutes from BAECs preincubated for 18 hours with or without PDBu (100 nmol/L). Results are expressed as mean±SEM of five independent experiments. *P<.01 compared with control.

We examined the effect of cAMP and cGMP on nitrite release stimulated by A23187 and ATP{gamma}S. Preincubation with Db-cAMP (0.1 µmol/L to 0.1 mmol/L) or 8-bromo-cGMP (0.1 µmol/L to 0.1 mmol/L) had no effect on the nitrite release stimulated by A23187 or ATP{gamma}S (Fig 7).



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Figure 7. Line graphs show effect of cyclic AMP (cAMP) and cGMP on nitrite release from bovine aortic endothelial cells (BAECs). We examined the effect of dibutylyl cAMP (Db-cAMP, A) and 8-bromo-cGMP (8-br-cGMP, B) on accumulation of nitrite release induced by 1 µmol/L A23187 ({circ}) and 10 µmol/L ATP{gamma}S ({bullet}) for 60 minutes from BAECs. BAECs were preincubated for 5 minutes with Db-cAMP or 8-br-cGMP at the concentration shown before addition of agonists. Results are expressed as mean±SEM of five independent experiments.


*    Discussion
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up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
*Discussion
down arrowReferences
 
The present study demonstrated that endothelial NOS was stoichiometrically phosphorylated by PKC and PKA and that PKC activation by phorbol ester reduced NOS activity in homogenates and intact BAECs. We examined the effect of phosphorylation of NOS on its catalytic activity in vitro. Although endothelial NOS was stoichiometrically phosphorylated by PKA and PKC, purified NOS rapidly lost its enzyme activity during incubation with PKC or PKA. Therefore, alteration in NOS activity was not detected in in vitro phosphorylation. To investigate the effect of NOS phosphorylation in intact cells, we examined NOS catalytic activity in homogenates from phorbol ester– and Db-cAMP–treated BAECs. Although Db-cAMP had no effect on NOS activity, TPA and PDBu reduced NOS activity in homogenates. Treatment with phorbol ester or Db-cAMP did not alter the total NOS expression. The reported amino acid sequences of endothelial NOS were highly homologous to those of brain NOS.9 10 12 Our present findings were consistent with previous data demonstrating that purified brain NOS was stoichiometrically phosphorylated by PKA and PKC and that activation of PKC in intact cells led to a dramatic decrease in NOS activity, whereas activation of PKA did not modulate NOS activity.22 PKC and PKA are shown to phosphorylate a different serine site on brain NOS. Therefore, endothelial NOS might be phosphorylated at two different sites by PKC and PKA, although we did not create two-dimensional phosphopeptide maps.

We used the chemiluminescence method for measuring NO release from BAECs. With this system, we demonstrated that PKC activation inhibited NO release from BAECs stimulated by A23187 as well as ATP{gamma}S. In contrast to PKC, both Db-cAMP and 8-bromo-cGMP did not affect NO release from BAECs. Moreover, downregulation of PKC produced a twofold increase in A23187-stimulated NO release. PKC is well recognized to inhibit receptor-mediated phosphoinositide hydrolysis, IP3 formation, and subsequent intracellular calcium mobilization in many cell types,32 33 and A23187 acts by directly translocating calcium ions across the cell membrane. Thus, inhibition of A23187-induced release of NO indicates that PKC may affect cellular events independent of a receptor coupling mechanism. Moreover, elevation of intracellular calcium concentration by A23187 was not inhibited by phorbol ester. These results suggest that PKC activation may act on the downstream of intracellular calcium signaling to inhibit NOS activity.

Direct measurement of NO release is pivotal for understanding its physiological role in the regulation of vascular tone. NO is a very labile compound, so it is difficult to assess NOS activity in vascular endothelial cells with biological assays including cGMP measurement or relaxation of detector vessels. Indeed, according to previous isometric contraction experiments or bioassay studies, the effect of PKC on the release of EDRF is controversial.34 35 36 Species differences and different experimental conditions may be related to the discrepancies among these studies. Recent studies suggest that the inhibitory effect of PKC on the release of EDRF is due to destruction of EDRF by superoxide anions produced by PKC.37 38 The chemiluminescence method can measure NO derived from nitrite and nitrosocompound, and therefore, even if NO reacts with superoxide anion to form peroxynitrite, this method can detect it. Therefore, our result indicates that PKC regulates NOS catalytic activity negatively by phosphorylating NOS in vascular endothelial cells.

In conclusion, we demonstrated that endothelial NOS was phosphorylated by PKC and PKA and that PKC activation markedly reduced NOS activity and subsequently decreased NO production in BAECs. Many vasoactive substances are known to activate phosphoinositide hydrolysis through G protein–coupled receptors, which results in the production of IP3 and diacylglycerol. Elevated intracellular calcium by IP3 stimulates NO production through constitutive NOS, and PKC activation by diacylglycerol diminishes NO generation by NOS phosphorylation. Therefore, receptor-coupled second messenger systems may regulate NOS activity and NO production in opposite directions in vascular endothelial cells.


*    Acknowledgments
 
The investigation was supported by grants-in-aid for Scientific Research from the Ministry of Education, Science, and Culture, Japan (1993), and a grant-in-aid for Research on Cardiovascular Disease from the Ministry of Health and Welfare, Japan (1992, 1993). PKC was kindly donated by Dr Yasutomi Nishizuka (Biochemistry, Kobe University [Japan]). We are grateful to Mitsuko Kobashi for her skillful technical assistance.


*    Footnotes
 
Reprint requests to Ken-ichi Hirata, MD, First Department of Internal Medicine, Kobe University School of Medicine, 7-chome Chuo-ku Kobe 650, Japan.

Received June 10, 1994; first decision August 9, 1994; accepted September 14, 1994.


*    References
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up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
up arrowDiscussion
*References
 

  1. Palmer RMJ, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature. 1987;327:524-526. [Medline] [Order article via Infotrieve]
  2. Myers PR, Minor RL, Guerra R, Bates JN, Harrison DG. Vasorelaxant properties of the endothelium-derived relaxing factor more closely resemble S-nitrosocysteine than nitric oxide. Nature. 1990;345:161-163. [Medline] [Order article via Infotrieve]
  3. Furchgott RF. Role of endothelium in responses of vascular smooth muscle. Circ Res. 1983;53:557-573. [Free Full Text]
  4. Moncada S, Palmer RMJ, Higgs EA. Nitric Oxide: physiology, pathophysiology, and pharmacology. Pharmacol Rev. 1991;43:109-142. [Medline] [Order article via Infotrieve]
  5. Palmer RMJ, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from L-arginine. Nature. 1988;333:664-666. [Medline] [Order article via Infotrieve]
  6. Nathan C. Nitric oxide as a secretory product of mammalian cells. FASEB J. 1992;6:3051-3064. [Abstract]
  7. Sessa WC, Harrison JK, Barber CM, Zeng D, Durieux ME, D'Angelo DD, Lynch KR, Peach MJ. Molecular cloning and expression of a cDNA encoding endothelial cell nitric oxide synthase. J Biol Chem. 1992;267:15274-15276. [Abstract/Free Full Text]
  8. Pollock JS, Förstermann U, Mitchell JA, Warner TD, Schmidt HHHW, Nakane M, Murad F. Purification and characterization of particulate endothelium-derived relaxing factor synthase from cultured and native bovine aortic endothelial cells. Proc Natl Acad Sci U S A. 1991;88:10480-10484. [Abstract/Free Full Text]
  9. Lamas S, Marsden PA, Li GK, Tempst P, Michel T. Endothelial nitric oxide synthase: molecular cloning and characterization of a distinct constitutive enzyme isoform. Proc Natl Acad Sci U S A. 1992;89:6348-6352. [Abstract/Free Full Text]
  10. Janssens SP, Shimouchi A, Quertermous T, Bloch DB, Bloch KD. Cloning and expression of a cDNA encoding human endothelium-derived relaxing factor/nitric oxide synthase. J Biol Chem. 1992;267:14519-14522. [Abstract/Free Full Text]
  11. Marsden PA, Schappert KT, Chen HS, Flowers M, Sundell CL, Wilcox JN, Lamas S, Michel T. Molecular cloning and characterization of human nitric oxide synthase. FEBS Lett. 1992;307:287-293. [Medline] [Order article via Infotrieve]
  12. Nishida K, Harrison DG, Navas JP, Fisher AA, Dockery SP, Uematsu M, Nerem RM, Alexander RW, Murphy TJ. Molecular cloning and characterization of the constitutive bovine aortic endothelial cell nitric oxide synthase. J Clin Invest. 1992;90:2092-2096.
  13. Bredt DS, Snyder SH. Isolation of nitric oxide synthase, a calmodulin-requiring enzyme. Proc Natl Acad Sci U S A. 1990;87:682-685. [Abstract/Free Full Text]
  14. Bredt DS, Hwang PM, Glatt CE, Lowenstein C, Reed RR, Snyder SH. Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase. Nature. 1991;351:714-718. [Medline] [Order article via Infotrieve]
  15. Yui Y, Hattori R, Kosuga K, Eizawa H, Hiki K, Kawai C. Purification of nitric oxide synthase from rat macrophages. J Biol Chem. 1991;266:12544-12547. [Abstract/Free Full Text]
  16. Xie QW, Cho HJ, Calaycay J, Mumford RA, Swiderek KM, Lee TD, Ding A, Troso T, Nathan C. Cloning and characterization of nitric oxide synthase from mouse macrophage. Science. 1992;256:225-228. [Abstract/Free Full Text]
  17. Lyons CR, Orloff GJ, Cunningham JM. Molecular cloning and functional expression of an inducible nitric oxide synthase from a murine macrophage cell line. J Biol Chem. 1992;267:6370-6374. [Abstract/Free Full Text]
  18. Nunokawa Y, Ishida N, Tanaka S. Cloning of inducible nitric oxide synthase in rat vascular smooth muscle cells. Biochem Biophys Res Commun. 1993;191:89-94. [Medline] [Order article via Infotrieve]
  19. Geller DA, Lowenstein CJ, Shapiro RA, Nussler AK, Silvio MD, Wang SC, Nakayama DK, Simmons RL, Snyder SH, Billiar TR. Molecular cloning and expression of inducible nitric oxide synthase from human hepatocytes. Proc Natl Acad Sci U S A. 1993;90:3491-3495. [Abstract/Free Full Text]
  20. Berridge MJ, Irvine RF. Inositol triphosphate, a novel second messenger in cellular signal transduction. Nature. 1984;312:315-321. [Medline] [Order article via Infotrieve]
  21. Nishizuka Y. The role of protein kinase C in cell surface signal transduction and tumor promotion. Nature. 1984;308:693-698. [Medline] [Order article via Infotrieve]
  22. Bredt DS, Ferris CD, Snyder SH. Nitric oxide synthase regulatory sites: phosphorylation by cyclic AMP-dependent protein kinase, protein kinase C, and calcium/calmodulin protein kinase: identification of flavin and calmodulin binding sites. J Biol Chem. 1992;267:10976-10981. [Abstract/Free Full Text]
  23. Reimann EM, Beham RA. Purification and properties of specific protein kinases: catalytic subunit of cAMP-dependent protein kinase. Methods Enzymol. 1983;99:51-55. [Medline] [Order article via Infotrieve]
  24. Ryan US, Mortara M, Whitaker C. Methods for microcarrier culture of bovine pulmonary artery endothelial cells avoiding the use of enzyme. Tissue Cell. 1980;12:619-635. [Medline] [Order article via Infotrieve]
  25. Hirata K, Akita H, Yokoyama M. Oxidized low density lipoprotein inhibits bradykinin-induced phosphoinositide hydrolysis in cultured bovine endothelial cells. FEBS Lett. 1991;287:181-184. [Medline] [Order article via Infotrieve]
  26. Inoue N, Hirata K, Yamada M, Hamamori Y, Matsuda Y, Akita H, Yokoyama M. Lysophosphatidylcholine inhibits bradykinin-induced phosphoinositide hydrolysis and calcium transients in cultured bovine aortic endothelial cells. Circ Res. 1992;71:1410-1421. [Abstract/Free Full Text]
  27. Ohashi Y, Katayama M, Hirata K, Suematsu M, Kawashima S, Yokoyama M. Activation of nitric oxide synthase from cultured aortic endothelial cells by phospholipids. Biochem Biophys Res Commun. 1993;195:1314-1320. [Medline] [Order article via Infotrieve]
  28. Laemmli UK. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970;227:680-685. [Medline] [Order article via Infotrieve]
  29. Cox RD. Determination of nitrate and nitrite at the parts per billion level by chemiluminescence. Anal Chem. 1980;52:332-335.
  30. Myers PR, Guerra R, Harrison DG. Release of NO and EDRF from cultured bovine aortic endothelial cells. Am J Physiol. 1989;256:H1030-H1037. [Abstract/Free Full Text]
  31. Bradford MM. A rapid and sensitive method for the quantification of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976;72:248-254. [Medline] [Order article via Infotrieve]
  32. Brock TA, Capasso EA. Thrombin and histamine activate phospholipase C in human endothelial cells via a phorbol ester-sensitive pathway. J Cell Physiol. 1988;136:54-62.[Medline] [Order article via Infotrieve]
  33. Carter TD, Hallam TJ, Pearson JD. Protein kinase C activation alters the sensitivity of agonist-stimulated endothelial cell prostacyclin production to intracellular Ca2+. Biochem J. 1989;262:431-437. [Medline] [Order article via Infotrieve]
  34. Weinheimer G, Wagner B, Osswald H. Interference of phorbol esters with endothelium-dependent vascular smooth muscle relaxation. Eur J Pharmacol. 1986;130:319-322. [Medline] [Order article via Infotrieve]
  35. Lewis MJ, Henderson AH. A phorbol ester inhibits the release of endothelium-derived relaxing factor. Eur J Pharmacol. 1987;137:167-171. [Medline] [Order article via Infotrieve]
  36. Rubanyi GM, Desiderio D, Luisi A, Johns A, Sybertz EJ. Phorbol dibutyrate inhibits release and action of endothelium-derived relaxing factor(s) in canine blood vessels. J Pharmacol Exp Ther. 1989;249:858-863. [Abstract/Free Full Text]
  37. Matsubara T, Ziff M. Superoxide anion release by human endothelial cells: synergism between a phorbol ester and a calcium ionophore. J Cell Physiol. 1986;127:207-210. [Medline] [Order article via Infotrieve]
  38. Smith JA, Lang D. Release of endothelium-derived relaxing factor from pig cultured aortic endothelial cells, as assessed by changes in endothelial cell cyclic GMP content, is inhibited by a phorbol ester. Br J Pharmacol. 1990;99:565-571.[Medline] [Order article via Infotrieve]



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