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D Beasley

Publications and source records attributed to D Beasley.

At least 19 recordsLinked to original sources
PubMed2001

Juxtacrine effects of IL-1 alpha precursor promote iNOS expression in vascular smooth muscle cells.

After injury to the blood vessel wall, vascular smooth muscle cells (SMC) synthesize interleukin (IL)-1 and inducible nitric oxide (NO) synthase (iNOS). The present study tested whether endogenous production of IL-1 alpha stimulates iNOS expression in vascular SMC, and assessed whether IL-1 alpha exerts autocrine effects on the cells producing IL-1 alpha or juxtacrine effects on cells that contact the IL-1 alpha producing cells. Rat aortic SMC were transiently transfected with expression plasmids encoding either IL-1 alpha precursor, which localizes to the plasma membrane, or mature IL-1 alpha, which remains cytosolic. iNOS mRNA levels, determined by RT-PCR, and production of nitrite, a stable oxidation product of NO, were markedly elevated in SMC overexpressing IL-1 alpha precursor, and modestly elevated in SMC overexpressing mature IL-1 alpha, relative to SMC transfected with vector alone. Exposure to exogenous IL-1 beta or TNF-alpha further stimulated iNOS gene expression in SMC producing IL-1 alpha; low levels of IL-1 beta (20 pg/ml) were effective in SMC transfected with IL-1 alpha precursor plasmid, whereas SMC transfected with mature IL-1 alpha plasmid or vector alone required higher concentrations of IL-1 beta (200 and 2,000 pg/ml, respectively). The increases in iNOS mRNA levels and NO production in SMC overexpressing IL-1 alpha precursor were prevented by exogenous IL-1 receptor antagonist, suggesting that these effects were mediated by the type I IL-1 receptor. Immunostaining studies indicated that IL-1 alpha precursor stimulates iNOS gene expression via cell-cell contact. Expression of iNOS was enhanced in cells that were in contact with a cell overexpressing IL-1 alpha precursor (identified by coexpression of green fluorescent protein), and in cells that were overexpressing IL-1 alpha themselves, but only when the cell contacted another cell. Together these results indicate that IL-1 alpha precursor acts by cell-cell contact as an autocrine and juxtacrine enhancer of iNOS gene expression, inducing moderate iNOS expression on its own, and markedly augmenting the responsiveness of rat aortic SMC to exogenous cytokines.

Animals↗
PubMed2000

Essential roles of IkappaB kinases alpha and beta in serum- and IL-1-induced human VSMC proliferation.

Interleukin-1 (IL-1) is a potent vascular smooth muscle cell (VSMC) mitogen, which can stimulate cells via activation of nuclear factor-kappaB (NF-kappaB) following phosphorylation of its inhibitory subunit (IkappaB). Because the proliferative effect of IL-1 is additive with that of serum, the present studies assessed the role of IkappaB kinases (IKKs) and NF-kappaB in both IL-1- and serum-induced VSMC proliferation. IL-1beta (1 ng/ml) induced marked and persistent NF-kappaB activation in VSMC that was maximal at 1 h and persisted for 3 days. There was a 3-fold increase in DNA synthesis after acute IL-1 exposure (24-96 h) and a 12-fold increase after chronic IL-1 exposure (>7 days). Electrophoretic mobility shift assay and supershift analysis indicated that IL-1-induced NF-kappaB complexes consisted of p65/p50 heterodimers and p50 homodimers. Human saphenous vein smooth muscle cells (HSVSMC) were transiently cotransfected with expression plasmids encoding a dominant negative mutant form of either IKKalpha or IKKbeta, in which K(44) was mutated to A (K44A), and a green fluorescent protein expression plasmid that allows identification of transfected cells. IL-1 induced nuclear localization of p65 in 95% of cells transfected with vector alone but in only 69% and 26% of cells expressing IKKalpha (K44A) or IKKbeta (K44A), respectively. Likewise, proliferation increased 3.2-fold in IL-1-treated HSVSMC which had been transfected with vector alone, but only 2.2- and 1.5-fold proliferation in HSVSMC expressing IKKalpha (K44A) or IKKbeta (K44A), respectively. Although serum activated NF-kappaB transiently, serum-induced proliferation was markedly attenuated in HSVSMC expressing IKKalpha (K44A) and IKKbeta (K44A) compared with HSVSMC transfected with vector alone. The results support an essential role of IKKs in the proliferative response of HSVSMC to IL-1 and to serum.

Animals↗
PubMed1999

Retinoic acid and CO2 laser resurfacing.

The purpose of this study was to analyze the effect of retinoic acid on wound healing and depth of injury in an animal skin model resurfaced with a CO2 laser. The dorsal skin of 21 Hartley guinea pigs was divided into halves. One-half received a daily application of 0.05% retinoic acid for 28 days, whereas the other half served as the control. The animals were divided into three treatment groups of seven animals. Group A was laser resurfaced with one pass of the Coherent UltraPulse CO2 laser (300 mJ, 60 W, density 40 percent). Group B received two passes, and group C received three passes. Histologic studies were obtained before laser resurfacing and days 1, 4, and 7 after resurfacing. Depth of injury, thickness, number of squamous cell and granular cell layers, and epithelialization rates were measured. We found that the depth of injury was statistically less in animals pretreated with retinoic acid. Granular cells were thicker and more numerous at day 4 in pretreated animals but similar to controls by day 7. Animals pre-treated with retinoic acid overall seemed to heal wounds earlier. In conclusion, pretreatment with retinoic acid may reduce the depth of injury in laser resurfacing and speed healing rates.

Animals↗
PubMed1999

Constitutive expression of interleukin-1alpha precursor promotes human vascular smooth muscle cell proliferation.

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in the failure of vascular surgeries and contributes to the development of atherosclerotic lesions. Evidence that interleukin-1 (IL-1) is a mitogen for cultured VSMC has implicated its release by activated macrophages in the development of atherosclerosis. VSMC also produce IL-1, including the precursor form of IL-1alpha. However, it is not known whether IL-1alpha precursor is processed to mature IL-1alpha or released from VSMC, nor is it known whether either precursor or mature IL-1alpha functions as an autocrine growth factor. The goals of the present study were to establish whether proliferation is enhanced in human VSMC transfectants producing IL-1alpha constitutively at levels comparable to those produced after activation, and to determine which domains of IL-1alpha are important for its activity. Human VSMC were stably transfected with expression vectors directing constitutive expression of either full-length IL-1alpha precursor [IL-1alpha-(1-271)], its NH2-terminal domain [IL-1alpha-(1-112)], or mature IL-1alpha [IL-1alpha-(113-271)]. Both IL-1alpha-(1-271) and IL-1alpha-(113-271) stable transfectants produced moderate levels of IL-1alpha (0.2-1.0 ng/10(6) cells) and released low levels of IL-1alpha into the supernatant (<20 pg/ml). VSMC stably transfected with either IL-1alpha-(1-271) or IL-1alpha-(113-271) expression plasmids proliferated rapidly compared with nontransfected or vector-transfected VSMC and displayed a distinct morphology characterized by elongated, spindle-shaped cells. Stable transfection with IL-1alpha-(1-271) was somewhat more effective than transfection with IL-1alpha-(113-271). Interestingly, VSMC transfected with IL-1alpha-(113-271) expression plasmids also expressed IL-1alpha-(1-271) mRNA, suggesting that IL-1alpha-(113-271) activates an IL-1-induced IL-1 autocrine loop. In contrast, neither proliferation rates nor morphology was affected by stable transfection with IL-1alpha-(1-112) expression plasmids. Exogenous IL-1 receptor antagonist partially reversed the enhanced DNA synthesis in VSMC transfected with either IL-1alpha-(1-271) or IL-1alpha-(113-271) expression plasmids, suggesting that the pro-proliferative effect of VSMC-derived IL-1alpha is at least partially mediated by signaling via the type I IL-1 receptor. These results demonstrate that IL-1alpha precursor is an autocrine growth factor for human VSMC and further indicate that amino acids 113-271 play a crucial role in its actions.

Blotting, Western↗
PubMed1999

COX-2 and cytosolic PLA2 mediate IL-1beta-induced cAMP production in human vascular smooth muscle cells.

Interleukin (IL)-1 is a potent vasodilator that causes prolonged induction of prostacyclin (PGI2) and cAMP synthesis in human vascular smooth muscle cells (HVSMC). The present study investigated IL-1 induction of PG synthetic enzymes in HVSMC and tested their respective roles in PGI2 and cAMP production. Cyclooxygenase (COX)-1 mRNA was not detectable in either control or IL-1-treated HVSMC, as assessed by RT-PCR. In contrast, COX-2 mRNA was detectable in control HVSMC, increased markedly (16-fold) after 1 h of IL-1 exposure, and increased further (52-fold) after 24 h. COX-2 protein levels, assessed by Western analysis, were increased concomitantly. HVSMC contained mRNA encoding both the secreted and cytosolic forms of phospholipase A2 (sPLA2 and cPLA2, respectively). IL-1 stimulation did not affect sPLA2 mRNA levels, but cPLA2 mRNA levels increased at 8 h, after the initial induction of PG synthesis. HVSMC constitutively expressed PGI2 synthase mRNA, and its levels were not affected by IL-1. A selective COX-2 inhibitor, NS-398, reversed IL-1-induced PGI2 and cAMP production, supporting a role of COX-2 in mediating increased PG synthesis. IL-1-induced cAMP was also reversed by a selective cPLA2 inhibitor, AACOCF3, but not by thioetheramide phosphorylcholine, which inhibits sPLA2 preferentially over cPLA2, supporting a requirement for cPLA2-derived arachidonic acid in IL-1-induced PG synthesis. The delayed induction of cPLA2 mRNA was also attenuated by NS-398, suggesting that it was secondary to the initial COX-2-induced PG synthesis. Together, the results support the hypothesis that IL-1 induces intracellular PG synthesis in HVSMC via rapid upregulation of COX-2, which utilizes cPLA2-derived arachidonic acid to generate PG metabolites that regulate adenylate cyclase.

Cells, Cultured↗
PubMed1999

Hypoxia stimulates proliferation and interleukin-1alpha production in human vascular smooth muscle cells.

Several lines of evidence indicate that hypoxia is a stimulus to vascular smooth muscle cell (VSMC) proliferation that occurs in pulmonary hypertension. The present study tested the hypothesis that low O(2) tension directly stimulates human VSMC proliferation by inducing them to produce interleukin (IL)-1, a potent autocrine growth factor for human VSMC. Human VSMC derived from pulmonary artery, aorta, or saphenous vein were incubated in either a normal in vitro O(2) environment (20% O(2)) or in chambers containing low (approximately 1%) or moderate (5%) O(2). Levels of IL-1alpha and IL-1beta mRNA increased in human VSMC after 24-48 h of incubation in low O(2) compared with levels in normoxic cells and then decreased upon subsequent reoxygenation. Levels of cell-associated IL-1alpha also increased progressively after 24-48 h in low O(2); however, detectable IL-1alpha was not released from the cells in the media. IL-1beta was detectable in cell lysates and supernatants; however, the levels were not affected by exposure to low O(2). mRNA encoding for tumor necrosis factor-alpha (TNF-alpha), a related cytokine and VSMC mitogen, was not detectable in human VSMC exposed to either low or 20% O(2). Proliferation of human VSMC was not stimulated during exposure to low O(2), despite the fact that cells remained responsive to the mitogenic effect of exogenous IL-1. Interestingly, however, exposure to 5% O(2) enhanced proliferation of human VSMC but did not induce IL-1alpha production. Inhibition of IL-1 binding to the type I IL-1 receptor by exogenous addition of IL-1-receptor antagonist (10 microgram/ml) did not attenuate the proliferation rates of human VSMC incubated in 20%, 5%, or low O(2) or in human VSMC that were reoxygenated after exposure to low O(2). These results demonstrate two direct and distinct effects of hypoxia on VSMC. Exposure to moderately low O(2) tension induces VSMC proliferation, independent of IL-1, whereas exposure to very low O(2) tension induces production of IL-1alpha.

Cell Division↗
PubMed1997

TxA2-induced pulmonary artery contraction requires extracellular calcium.

In order to examine the role of extracellular calcium in the pulmonary arterial vasoconstriction that is elicited by thromboxane A2 (TxA2), rabbits were sacrificed and the main trunk of the pulmonary artery removed. Contractile responses of the isolated vessel to the TxA2 mimetic, U46 619, were measured in a temperature controlled (37 degrees C) organ bath. Compared with control responses, U46 619 microM) contractions were nearly eliminated when 1 mM EGTA was added to the buffer. In the presence of normal extracellular calcium concentrations, antagonists of voltage sensitive calcium channels (e.g. verapamil and nifedipine) attenuated the U46 619-induced contractions. These voltage sensitive calcium channel blockers were more effective in eliminating contractile responses to high KCl concentrations (6) or 120 mM KCl). The inability of these calcium channel antagonists to completely eliminate U46 619 responses was confirmed in the anesthetized rabbit where both nifedipine and verapamil failed to block the increase in pulmonary arterial blood pressure resulting from intravenous U46 619 infusion. These results indicate that extracellular calcium is essential for U46 619-induced pulmonary vascular contraction, and that mechanisms in addition to voltage operated calcium channels participate in the movement of extracellular calcium through the plasma membrane.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1997

Phorbol ester and interleukin-1 induce interleukin-6 gene expression in vascular smooth muscle cells via independent pathways.

Previous studies using bioassays suggest that interleukin 6 (IL-6) is a major secretory product of vascular smooth muscle cells (VSMC), which is induced by proinflammatory cytokines. This study investigated whether activation of the protein kinase C (PKC) pathway induces IL-6 gene expression and release in VSMC, by using both bioassay and specific immunoassay methods to measure IL-6 release. Activation of PKC with a phorbol ester, PMA (phorbol myristate acetate), induced a rapid and transient (1-4 h) increase in the levels of both 1.2- and 2.4-kb IL-6 transcripts in rat aortic SMCs (RASMC), as determined by Northern analysis, which was followed by increased release of bioactive IL-6, as determined by a B9 cell-proliferation assay. IL-1, a physiological activator of PKC, induced a rapid increase in IL-6 messenger RNA (mRNA) levels, which was sustained at 24 h. PMA-induced IL-6 mRNA levels in RASMC were markedly attenuated after downregulation of PKC with PMA and by the selective PKC inhibitor, bisindolylmaleimide. In contrast, IL-1-induced increases in IL-6 mRNA were not affected by either PKC downregulation or bisindolylmaleimide. Angiotensin II (Ang II), also known to activate PKC, likewise induced a rapid increase in IL-6 mRNA levels and IL-6 release in RASMC, but the effect was not blocked by PKC downregulation. VSMC derived from human saphenous vein (HSVSMC) released substantial amounts of immunoreactive IL-6 in the absence of stimulation by exogenous growth factors, and both PMA and IL-1 markedly increased IL-6 release. Furthermore, downregulation of PKC and bisindolylmaleimide blocked the effect of PMA but not that of IL-1 in HSVSMC. These results suggest that activation of phorbol ester-responsive PKC induces IL-6 gene expression in both rat and human VSMC. In contrast, IL-1 and Ang II activate IL-6 gene expression by a pathway distinct from that of phorbol ester-responsive PKC.

Angiotensin II↗
PubMed1995

Interleukin 1 induces prostacyclin-dependent increases in cyclic AMP production and does not affect cyclic GMP production in human vascular smooth muscle cells.

Interleukin 1 (IL-1) is a pro-inflammatory cytokine which has direct vasorelaxant effects on vascular smooth muscle cells (VSMC). In the present study, IL-1 markedly increased intracellular levels of the vasodilatory mediator, cAMP, in human saphenous and human aortic VSMC. IL-1-induced cAMP was associated with a marked increase in prostacyclin (PGI2) production, and was reversed by indomethacin and tranylcypromine, inhibitors of cyclooxygenase and PGI2 synthetase respectively. Furthermore, PGI2, but not PGE2, was a potent inducer of cAMP production in HSVSMC, implicating a role for PGI2 in mediating IL-1-induced cAMP production. In previous studies, IL-1 increased immunoreactive cGMP production in human saphenous VSMC through a pathway inhibitable by soluble guanylate cyclase inhibitors, methylene blue and LY83583, but not by nitric oxide (NO) synthase inhibitors, suggesting a role of NO-independent activation of soluble guanylate cyclase. However, in the present study, it was found that cAMP cross-reacted significantly in cGMP radioimmunoassays employing three out of four commercial antisera, that IL-1 did not affect cGMP production in human saphenous or human aortic VSMC as determined by an RIA having low cAMP cross-reactivity, and that both LY83583 and methylene blue inhibited IL-1-induced increases in cAMP. The results implicate prostacyclin-dependent cAMP production as a mediator of the vasodilatory effects of IL-1 in humans.

Aminoquinolines↗
PubMed1995

Human vascular smooth muscle cells produce an intracellular form of interleukin-1 receptor antagonist.

Interleukin-1 (IL-1) is a proinflammatory monocyte- and macrophage-derived cytokine that has potent vasorelaxant effects on vascular smooth muscle cells (VSMC). VSMC themselves also express both IL-1 alpha- and beta-genes, suggesting that IL-1 may be an autocrine regulator of VSMC function. The present study demonstrates that human saphenous vein VSMC (HSVSMC) produce IL-1 receptor antagonist (IL-1Ra), a specific inhibitor of IL-1 action. IL-1Ra was produced constitutively in most experiments, and its production was upregulated by phorbol 12-myristate 13-acetate and by IL-1 beta. IL-1Ra produced by HSVSMC remained predominately cell associated and was not detectable extracellularly. Furthermore, reverse transcription-polymerase chain reaction analysis and cDNA sequencing indicated that HSVSMC express the alternatively spliced form of IL-1Ra which lacks the signal peptide present in secreted IL-1Ra. HSVSMC also produced IL-1 alpha and the precursor form but not the mature form of IL-1 beta. These results suggest that HSVSMC lack active IL-1 beta-converting enzyme. Like IL-1Ra, IL-1 beta precursor and IL-1 alpha remained cell associated, predominately in the cytosolic fraction. IL-1 beta induced production of both IL-1Ra and IL-1 alpha at each time point and concentration tested. In contrast, platelet-derived growth factor and transforming growth factor-beta augmented production of IL-1Ra, but not that of IL-1 alpha. These results are suggestive of an autocrine role for cell-associated IL-1Ra, as well as for IL-1 alpha and IL-1 beta, in the regulation of VSMC function.

Base Sequence↗
PubMed1994

Interleukin 1 activates soluble guanylate cyclase in human vascular smooth muscle cells through a novel nitric oxide-independent pathway.

Recent demonstration of cytokine-inducible production of nitric oxide (NO) in vascular smooth muscle cells (VSMC) from rat aorta has implicated VSMC-derived NO as a key mediator of hypotension in septic shock. Our studies to determine whether an inducible NO pathway exists in human VSMC have revealed a novel cytokine-inducible, NO-independent pathway of guanylate cyclase activation in VSMC from human saphenous vein (HSVSMC). Interleukin 1 (IL-1), tumor necrosis factor (TNF), interferon gamma (IFN-gamma) and Escherichia coli lipopolysaccharide (LPS) increased cGMP at 24 h, whereas IL-2 and IL-6 were ineffective. The effect of IL-1 on cyclic guanosine 3',5'-monophosphate (cGMP) was delayed, occurring after 6 h of exposure, and was maximal after 10 h. Methylene blue and LY83583 reversed the IL-1-induced increase in cGMP, suggesting that it was mediated by activation of soluble guanylate cyclase. However, IL-1-induced cGMP in HSVSMC was not inhibited by extracellular hemoglobin. Also, the effect of IL-1 on cGMP was not reversed by nitro- or methyl-substituted L-arginine analogs, aminoguanidine, or diphenyleneiodonium, all of which inhibit IL-1-induced NO synthase in rat aortic VSMC (RAVSMC). IL-1-induced cGMP in HSVSMC was also independent of tetrahydrobiopterin and extracellular L-arginine, as it was not affected by 2,4-diamino-6-hydroxyprytimidine, an inhibitor of tetrahydrobiopterin biosynthesis, and was similar in L-arginine-free and L-arginine-containing media. Analysis of NO synthase mRNA with the use of polymerase chain reaction indicates that levels of mRNA for inducible NO synthase are several orders of magnitude lower in IL-1-treated human HSVSMC than in IL-1-treated RAVSMC. IL-1-induced cGMP was also NO independent in human umbilical artery VSMC, and NO dependent in rat vena cava VSMC. Together these results indicate that IL-1 activates a novel NO-independent pathway of soluble guanylate cyclase activation in human VSMC.

Amino Acid Oxidoreductases↗
PubMed1994

Borrelia burgdorferi and Escherichia coli lipopolysaccharides induce nitric oxide and interleukin-6 production in cultured rat brain cells.

Borrelia burgdorferi, the spirochetal agent of Lyme disease, infects the central nervous system (CNS), but the factors that mediate inflammation and neurologic dysfunction are not known. Sonicated B. burgdorferi stimulated in a concentration-dependent manner the production of nitric oxide (NO) in glial-enriched primary cultures of neonatal rat brain cells via induction of NO synthase activity. Lipopolysaccharide (LPS) of Escherichia coli also stimulated nitrite accumulation in a concentration-dependent manner. Stimulation of NO production by B. burgdorferi sonicate and E. coli LPS was associated with increased levels of mRNA coding for the cytokine-inducible form of NO synthase. B. burgdorferi sonicate also stimulated release of interleukin-6, with a concentration-response relationship similar to that for its stimulation of nitrite production, as did E. coli LPS. A competitive antagonist of E. coli LPS, Rhodopseudomonas sphaeroides lipid A, inhibited LPS-induced stimulation of NO synthase activity but markedly potentiated that of B. burgdorferi, indicating that the initial triggering mechanism of B. burgdorferi is distinct from that of E. coli LPS. Induction of NO synthase by bacterial agents within the brain may represent a common pathway of CNS inflammation and neurotoxicity.

Amino Acid Oxidoreductases↗
PubMed1994

Interleukin-1 beta and tumor necrosis factor-alpha synergistically induce NO synthase in rat vascular smooth muscle cells.

Cytokine-inducible nitric oxide (NO) production has been implicated in the pathogenesis of septic shock. The present study was designed to determine which cytokines induce expression of the NO synthase gene in rat aortic vascular smooth muscle cells (VSMC) in vitro and whether NO synthase gene expression is inducible in vivo. NO synthase mRNA appeared after 4-h exposure to interleukin-1 beta (IL-1 beta), and levels continued to increase up to 24 h. Levels of NO synthase transcripts were greatest in VSMC treated with IL-1 beta (1 nM), lower in VSMC treated with Escherichia coli lipopolysaccharide (LPS; 100 micrograms/ml), and just detectable in VSMC treated with tumor necrosis factor-alpha (TNF-alpha; 1 nM). IL-1 beta, TNF-alpha, and LPS each induced NO synthase activity, assessed by release of nitrite, conversion of L-arginine to L-citrulline, and increased levels of guanosine 3',5'-cyclic monophosphate, whereas IL-2, IL-6, and interferon-gamma were ineffective. IL-1 beta was more potent and effective than TNF-alpha; however, submaximal concentrations of TNF-alpha acted synergistically with IL-1 beta to induce NO synthase gene expression and activity. Inducible NO synthase mRNA was present in aorta from rats 6 h after treatment with LPS (5 mg/kg), but not at 24 h. Synergistic activation of NO synthase gene expression in VSMC by IL-1 beta and TNF-alpha may contribute to hypotension in sepsis.

Amino Acid Oxidoreductases↗
PubMed1992

Interleukin-1 beta alters actin expression and inhibits contraction of rat thoracic aorta.

Previous studies have indicated that interleukin-1 beta (IL-1) inhibits contraction of rat aortas by activating nitric oxide production in vascular smooth muscle cells, with subsequent increases in guanosine 3',5'-cyclic monophosphate (cGMP). This study determined if the effect of IL-1 involves the primary regulatory event in smooth muscle activation, myosin light chain (MLC) phosphorylation. This study also examined whether IL-1 affects contractile protein content. IL-1 (20 ng/ml) significantly decreased stress in response to 0.1 microM phenylephrine with a concomitant decrease in MLC phosphorylation. Incubation with IL-1 for 3 h or longer decreased alpha-smooth muscle actin and increased gamma-actin isoform, with no change in beta-nonmuscle actin or myosin isozyme content. These results suggest that IL-1 inhibition of a vascular smooth muscle contraction may be due to a decrease in activator calcium, which may account for the resultant decrease in MLC phosphorylation. These results also indicate that IL-1 significantly affects contractile protein content, enhancing gamma-actin isoforms and decreasing the vascular smooth muscle specific alpha-isoactin.

Actins↗
PubMed1991

Interleukin 1 induces prolonged L-arginine-dependent cyclic guanosine monophosphate and nitrite production in rat vascular smooth muscle cells.

The cytokine interleukin 1 (IL-1) inhibits contractile responses in rat aorta by causing endothelium-independent and prolonged activation of soluble guanylate cyclase. The present study tested whether IL-1 activates guanylate cyclase by inducing prolonged production of nitric oxide in cultured rat aortic vascular smooth muscle cells (VSMC). IL-1 induced a marked time-dependent increase in cyclic guanosine monophosphate (cGMP) in VSMC which was significant at 6 h, and increased progressively for up to 36 h. This effect of IL-1 was abolished when protein synthesis was inhibited with cycloheximide or actinomycin D, suggesting that the effect of IL-1 involves new protein synthesis. IL-1-induced cGMP accumulation was inhibited by the soluble guanylate cyclase inhibitors, methylene blue, LY83583, and hemoglobin and by the L-arginine analogue NGmonomethyl-L-arginine (L-NMMA). The inhibitory effect of L-NMMA was reversed by a 10-fold excess of L-arginine, but not by D-arginine. Nitrite, an oxidation product of nitric oxide, accumulated in the media of VSMC incubated with IL-1 for 24 h in the presence of L-arginine, whereas both IL-1-induced cGMP accumulation and nitrite production were attenuated in VSMC incubated in L-arginine-deficient medium. In L-arginine-depleted VSMC, IL-1-induced cGMP accumulation was restored to control levels by a 15-min incubation with L-arginine. These results demonstrate that IL-1 activates guanylate cyclase in rat VSMC by inducing production of nitric oxide via a pathway dependent on extracellular L-arginine.

Aminoquinolines↗
PubMed1990

Endotoxin inhibits contraction of vascular smooth muscle in vitro.

Decreased responsiveness of the vasculature to vasoconstrictors has been implicated in the pathogenesis of endotoxic shock, yet the mechanism of diminished responsiveness has not been determined. In these studies, exposure of rat aortic rings to purified Escherichia coli lipopolysaccharide (endotoxin) in vitro inhibited subsequent contractions caused by vasoconstrictors. Contractions caused by the alpha-adrenoceptor agonist phenylephrine, as well as those induced by potassium depolarization, were depressed by endotoxin. The effect of endotoxin on vascular contractions was delayed. Phenylephrine-induced contractions were not decreased during a 1-h exposure to endotoxin (10 micrograms/ml), but they were markedly decreased when tested several hours after the exposure period. A large part of the inhibition caused by a 1-h exposure to endotoxin was endothelium dependent. In contrast, endotoxin inhibited contractions equally in rings with or without endothelium exposed to endotoxin for a longer period (3 h). The inhibitory effect of endotoxin was not affected by indomethacin, but it was eliminated in aortic rings treated with the protein synthesis inhibitor cycloheximide. These studies indicate that endotoxin potently inhibits vascular contraction in vitro. The effect of endotoxin is apparently independent of prostanoids but may involve protein synthesis and effects on both vascular smooth muscle and endothelial cells.

Acetylcholine↗