Endothelium-dependent contractions are associated with both augmented expression of prostaglandin H synthase-1 and hypersensitivity to prostaglandin H2 in the SHR aorta

Prostaglandin H2 (PGH2 [endoperoxide]) is an immediate product of prostaglandin H (PGH) synthase activity (cyclooxygenase) and a likely candidate to mediate endothelium-dependent contractions evoked by acetylcholine in the aorta of the spontaneously hypertensive rat (SHR). Experiments were designed to investigate whether or not endothelium-dependent contractions were associated with an increased expression of PGH synthase, an augmented acetylcholine-induced release of PGH2, and/or a hypersensitivity of the smooth muscle to endoperoxides in SHR aorta compared with normotensive Wistar-Kyoto (WKY) aorta. In SHR aorta, endothelium-dependent contractions to acetylcholine were abolished by tenidap (10(-8) mol/L), a preferential PGH synthase-1 inhibitor, but slightly impaired by NS-398 (10(-6) mol/L), a preferential PGH synthase-2 inhibitor. PGH synthase-1 expression, which was evaluated by both reverse transcriptase-polymerase chain reaction and Western blotting, was about twofold greater in preparations with endothelium from SHR than from WKY rats. There was no difference in PGH synthase-1 expression between preparations with and those without endothelium in both strains. In SHR but not WKY aortas, acetylcholine (10(-5) mol/L, 5 minutes) caused a significant endothelium-dependent release of PGH2 as measured by gas chromatography/mass spectrometry. PGH2 evoked more potent contractions in rings without endothelium from SHR than from WKY rats, whereas the thromboxane analogue U46619 and prostaglandin F2 alpha caused a comparable response in both preparations. These results show that endothelium-dependent contractions to acetylcholine in SHR aorta are associated with a greater expression of PGH synthase-1, a significant release of PGH2, and a hypersensitivity of the smooth muscle to the endoperoxide.

Platelet-derived growth factor suppresses and fibroblast growth factor enhances cytokine-induced production of nitric oxide by cultured smooth muscle cells. Effects on cell proliferation

Stimulation of thymidine incorporation by basic fibroblast growth factor or epidermal growth factor treatment of cultured quiescent smooth muscle cells (rat and human) was attenuated by the concomitant treatment with interleukin-1 beta in the presence of indomethacin. Platelet-derived growth factor-AB and -BB-induced thymidine incorporation was not inhibited by the presence of the cytokine under similar experimental conditions. Elevation of nitrite levels in the conditioned medium of cultures exposed to interleukin-1 beta correlated with the inhibition of thymidine incorporation. Platelet-derived growth factor-AB and -BB inhibited the production of nitric oxide (measured as nitrite levels in conditioned medium) by cells treated simultaneously with interleukin-1 beta and growth factor. However, platelet-derived growth factor-AA neither affected nitrite production nor thymidine incorporation by smooth muscle cells. Levels of cytokine-stimulated nitrite production by smooth muscle cells were increased synergistically by the presence of fibroblast growth factors or epidermal growth factor. The inhibition of thymidine incorporation and concomitant elevation of nitrite production was abolished in the presence of nitro-L-arginine. Cultures maintained in the presence of low levels of the cytokine for 9 days were growth-inhibited, and this was reversed when culture medium was supplemented with nitro-L-arginine. The treatment of smooth muscle cells, which were grown in coculture inserts with the cytokine to induce nitric oxide production, before their combination with other quiescent layers of cells resulted in the inhibition of thymidine incorporation by this second layer of cells regardless of the growth factor used for stimulation. Nitric oxide may act as an endogenous inhibitor of smooth muscle cell proliferation in the vessel wall, and impairment of its production may be one action of potent vascular mitogens such as platelet-derived growth factor.

Interleukin-1 beta induces the production of an L-arginine-derived relaxing factor from cultured smooth muscle cells from rat aorta

The effect of interleukin-1 beta on the production of non-prostanoid vasoactive factors by cultured rat aortic smooth muscle cells was investigated. Under bioassay conditions, the perfusate from a column of confluent cells grown on beads and treated with interleukin-1 beta (1 ng/ml for 18 to 24 hr) abolished the contraction of a canine coronary ring without endothelium contracted by phenylephrine (1 microM), while the perfusate from control cells had no effect. The relaxing activity of the perfusate was observed when transit times were increased from 1 sec to 5 min. Nitro L-arginine (100 microM) reversed the relaxations and L-arginine stereoselectively restored the relaxations. Interleukin-1 beta (1 ng/ml) evoked a time-dependent accumulation of cyclic GMP but not cyclic AMP in cultured smooth muscle cells. The transfer of fresh or stored (-70 degrees C) conditioned culture medium from interleukin-1 beta-treated cells but not from control cells, to cultured smooth muscle cells stimulated the production of cyclic GMP. These observations demonstrate that interleukin-1 beta induces the production of transferable factor which relaxes vascular smooth muscle and stimulates the production of cyclic GMP.

The induction of nitric oxide synthase activity is inhibited by TGF-beta 1, PDGFAB and PDGFBB in vascular smooth muscle cells

The effect of transforming growth factor-beta 1 (TGF-beta 1) and platelet-derived growth factor (PDGF) was investigated on the induction of nitric oxide synthase activity caused by interleukin-1 beta in cultured smooth muscle cells from rat aorta. TGF-beta 1, PDGFAB and PDGFBB but not PDGFAA inhibited in a concentration-dependent manner the production of nitrite, an oxidation product of nitric oxide, evoked by interleukin-1 beta. The growth factors alone did not stimulate the release of nitrite. The addition of interleukin-1 beta-treated smooth muscle cells to suspensions of indomethacin-treated human washed platelets inhibited the aggregation evoked by thrombin whereas no effect was observed with untreated cells. Platelet aggregation was not inhibited by smooth muscle cells that had been pretreated with interleukin-1 beta in combination with either TGF-beta 1, PDGFAB or PDGFBB but not with PDGFAA. These observations demonstrate that platelet-derived products such as TGF-beta and PDGFs inhibit the induction of nitric oxide synthase activity in vascular smooth muscle cells.

Inhibition of cytokine-induced nitric oxide production by transforming growth factor-beta 1 in human smooth muscle cells

1. Experiments were performed to investigate the effects of human recombinant interleukin-1 beta on the production of vasoactive substances by human aortic smooth muscle cells in culture. Smooth muscle cells were cultured either on microcarrier beads for bioassay experiments, or in multiwell plates for the determination of nitrite levels. 2. Cells were grown on microcarrier beads, treated with interleukin-1 beta or vehicle (control) for 24 h, and packed in a column which was perfused with oxygenated Krebs-Ringer solution in the presence of indomethacin. The activity of the perfusates was bioassayed by measuring the changes in tension of a contracted ring of Wistar rat aorta without endothelium, and by evaluating the modulation of thrombin-induced platelet aggregation. 3. Perfusates from interleukin-1 beta treated cells evoked relaxations of the contracted detector tissues, and microcarrier beads covered with treated cells inhibited thrombin-induced platelet aggregation. Superoxide dismutase enhanced these effects whereas Methylene Blue abolished them. Control cells evoke neither relaxation nor inhibition of platelet aggregation. Interleukin-1 beta induced a time- and concentration-dependent production of nitrite. Cycloheximide and nitro-L-arginine inhibited the relaxations and the production of nitrite evoked by interleukin-1 beta-treated cells. L-Arginine but not D-arginine overcame the blockade elicited by nitro-L-arginine. Transforming growth factor-beta 1 reduced the interleukin-1 beta-dependent generation of nitrite by cultured smooth muscle cells and relaxation of contracted bioassay tissues. 4. Interleukin-1 beta, transforming growth factor-beta 1, Methylene Blue and L-arginine-related compounds did not induce significant variations of tension of the detector rings. 5. These data demonstrate that the inflammatory and immunological mediator interleukin-1 can stimulate the production of a nitric oxide-like substance(s) in cultured human smooth muscle cells leading to the activation of soluble guanylate cyclase. Liberation of transforming growth factor-beta by activated platelets may inhibit these reactions.

Enhanced production of nitric oxide in aortae from spontaneously hypertensive rats by interleukin-1 beta

Cultured aortic smooth muscle cells from spontaneously hypertensive rats produce more nitrite than cells from Wistar-Kyoto rats in response to interleukin-1 beta. Therefore, the effect of interleukin-1 beta-induced nitric oxide production was compared on the contractility of aortic smooth muscle from spontaneously hypertensive and Wistar-Kyoto rats. Under control conditions, there was no difference in the response of aortic rings (without endothelium) to phenylephrine between both strains. Contractions to 5-hydroxytryptamine were larger in preparations from hypertensive than normotensive animals. Treatment with interleukin-1 beta for 6 h reduced the responsiveness to both vasoconstrictors in a concentration-dependent manner. The depression was more pronounced in rings from spontaneously hypertensive rats: the threshold concentration of the cytokine was lower, and its maximal effect greater. Nitro-L-arginine prevented the inhibitory effect of interleukin-1 beta. The cytokine evoked a time-dependent loss of tone in phenylephrine-contracted rings with the same time of onset in both strains. However, the decay of tension was more pronounced in aortae from hypertensive than normotensive rats. In aortae from both strains, the decay was potentiated by L-arginine, but not D-arginine. Interleukin-1 beta elicited greater concentration-dependent productions of cyclic GMP and nitrite in rings from spontaneously hypertensive than from Wistar-Kyoto rats, and these were inhibited by methylene blue and nitro-L-arginine, respectively. The concentration-relaxation curves to 3-morpholino-sydnonimine were moderately, but significantly, shifted to the left in aortae from spontaneously hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Indapamide potentiates the endothelium-dependent production of cyclic guanosine monophosphate by bradykinin in the canine femoral artery

Indapamide is a sulfonamide diuretic agent that has antihypertensive properties. In the canine femoral artery, indomethacin reduces the endothelium-dependent relaxation induced by bradykinin, and indapamide restores the response. The aim of this study was to determine whether indapamide affects the release or the effects of endothelium-derived nitric oxide and prostanoids. The effect of indapamide on the production of endothelium-derived nitric oxide and prostacyclin was assessed indirectly by the measurement of the tissue content of cyclic guanosine monophosphate (GMP) and the accumulation of 6-keto-prostaglandin F1 alpha in the incubation medium, respectively. Indapamide did not affect the basal production of either cyclic GMP, cyclic adenosine monophosphate (AMP), or 6-keto-prostaglandin F1 alpha in the presence or absence of indomethacin. Indomethacin decreased the production of cyclic AMP and the release of 6-keto-prostaglandin F1 alpha induced by bradykinin, and this was unaffected by indapamide. Indapamide enhanced the bradykinin-stimulated production of cyclic GMP in the presence of indomethacin and did not affect that evoked by 3 morpholino-sydnonimine, an exogenous donor of nitric oxide. Indomethacin had no significant effect on the production of cyclic GMP stimulated by either bradykinin or 3 morpholino-sydnonimine. These studies demonstrate that the potentiation by indapamide of the relaxation evoked by bradykinin is associated with an enhanced production of cyclic GMP in the presence of indomethacin, which suggests that the production of endothelium-derived nitric oxide is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet inhibition by an L-arginine-derived substance released by IL-1 beta-treated vascular smooth muscle cells

Experiments were performed to examine whether stimulation of cultured vascular smooth muscle cells by interleukin (IL)-1 beta would induce platelet inhibitory properties of these cells. Incubation of platelets with untreated rat aortic smooth muscle cells had no effect on thrombin-induced platelet aggregation. In contrast, incubation of platelets with IL-1 beta-pretreated smooth muscle cells or the perfusate from such cells resulted in the inhibition of thrombin-induced platelet aggregation. This effect was potentiated by superoxide dismutase and reversed by incubating the IL-1 beta-treated smooth muscle cells with NG-nitro-L-arginine (L-NNA) or by treating the platelets with methylene blue. Cytokine-treated smooth muscle cells inhibited thrombin-stimulated changes in platelet cytosolic ionized calcium, whereas untreated cells were without effect. Incubating platelets with IL-1 beta-treated smooth muscle cells resulted in a 10-fold increase in platelet guanosine 3',5'-cyclic monophosphate (cGMP) levels, whereas untreated smooth muscle cells had no effect. The elevation of platelet cGMP induced by the IL-1 beta-treated smooth muscle cells was prevented by exposing the cytokine-treated cells to L-NNA or by treating platelets with methylene blue. Treatment of smooth muscle cells with IL-1 beta also resulted in an eightfold increase in nitrite production, which was blocked when the cells were incubated with L-NNA. The addition of cycloheximide to smooth muscle cells during their incubation with IL-1 beta completely inhibited smooth muscle cell nitrite production, the effects of the smooth muscle cells on platelet cGMP levels, and platelet responses to thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming growth factor-beta 1 inhibits L-arginine-derived relaxing factor(s) from smooth muscle cells

The effects of human recombinant interleukin-1 beta were investigated on the release of nonprostanoid relaxing substances from cultured aortic smooth muscle cells from Wistar rats. Cells cultured on microcarrier beads were packed in columns. The perfusate over these beads was bioassayed by measuring changes in isometric tension of contracted arteries without endothelium. The perfusates from interleukin-1 beta-treated smooth muscle cells, but not from control cells, evoked relaxations. The relaxations persisted when the transit time between the cultured smooth muscle cells and the detector was increased to 5 min. The effect of relaxing substance(s) was inhibited by cycloheximide, nitro-L-arginine, methylene blue, and transforming growth factor-beta 1. L-Arginine but not D-arginine overcame the blockade by nitro-L-arginine. Superoxide dismutase potentiated the relaxations. In cells cultured in multiwell plates, interleukin-1 beta evoked a time- and concentration-dependent accumulation of nitrite in the extracellular medium that was inhibited dose dependently by transforming growth factor-beta 1. These studies demonstrate that cultured smooth muscle cells can be stimulated to produce nitric oxide-related substances and that the inducible pathway is modulated by transforming growth factor-beta 1.