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PubMed2005

The astroglial-derived S100beta protein stimulates the expression of nitric oxide synthase in rodent macrophages through p38 MAP kinase activation.

S100beta is an astroglial-derived Ca2+ -binding protein having neurotrophic role on neurons and glial cells. An aberrant S100beta production has been observed in neurodegenerative disease, as Alzheimer's disease and Down syndrome. S100beta is responsible to start up a gliotic reaction by the release of pro-inflammatory mediators, including nitric oxide (NO) and cytokines from microglia and astrocytes, which are, in turn, deleterious for neurons. Interestingly, pro-inflammatory effect of S100beta seems not be restricted into the brain. Macrophages play a pivotal role in inflammatory diseases, occurring both in the brain and in the periphery. In this study, we tested the hypothesis that S100beta may affect macrophage functions, amplifying thus the inflammatory process. Our results demonstrate that S100beta stimulates both NO production and iNOS protein transcription and expression in J774 and rat peritoneal macrophages. NO production was concentration and time-dependently inhibited by two iNOS inhibitors, L-NAME and SMT. We also demonstrated that S100beta induced oxidative stress by increasing H2O2 production and lipid peroxidation of cell membrane in both macrophage types. The pro-oxidant potential of S100beta activates p38 MAP kinase (MAPK), which has been described to directly activate NF-kappaB. In our study, SB203580, a p38 MAPK inhibitor, and two NF-kappaB inhibitors, TLCK and BAY 11-7082, decreased both NO production and iNOS protein transcription and expression in S100beta-stimulated J774 and peritoneal rat macrophages. Moreover, additional studies demonstrated that S100beta affected also TNF-alpha protein expression in J774 macrophages. In conclusion, our results highlight the potential role of S100beta during an inflammatory scenario identifying macrophages as a novel S100beta-responsive cell-type.

Animals↗
PubMed2005

COX-2 mediates morphine-induced delayed cardioprotection via an iNOS-dependent mechanism.

Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) have been shown to be mediators of cardioprotection induced by ischemic preconditioning and opioids. However, it is not known whether COX-2 is involved in morphine-induced cardioprotection accompanied with iNOS. Therefore, we investigated the role of COX-2 in morphine-induced cardioprotection and the effect of iNOS on COX-2. Myocardial ischemia was induced by a 45-min coronary artery occlusion in mice. Infarct size (IS) as a percentage of the area at risk (AAR) was determined by triphenyltetrazolium chloride staining. The COX-2-selective inhibitor NS-398 was used to investigate the role of COX-2. Expression of COX-2 was assessed by Western blotting, and the myocardial prostaglandin (PG)E2 and 6-keto-PGF(1alpha) contents were measured using enzyme immunoassays. The iNOS-selective inhibitor SMT and iNOS gene-knockout mice were used to investigate the effect of iNOS on COX-2. IS/AAR was reduced significantly 1 and 24 h after morphine preconditioning. The infarct-sparing effect 24 h after morphine administration, but not the cardioprotection 1 h later, was completely abolished by NS-398. Marked enhancement of myocardial COX-2 expression was measured 24 h after morphine preconditioning associated with up-regulation of myocardial contents of PGE2 and 6-keto-PGF(1alpha). Neither the level of COX-2 nor the contents of PGE2 and 6-keto-PGF(1alpha) were enhanced 1 h later. Administration of SMT and targeted abrogation of iNOS gene blocked the enhancement of myocardial PGE2 and 6-keto-PGF(1alpha) 24 h after morphine administration but did not inhibit the up-regulation of COX-2 expression. We concluded that COX-2 mediates morphine-induced delayed cardioprotection via an iNOS-dependent pathway.

6-Ketoprostaglandin F1 alpha↗
PubMed2006

Cannabidiol inhibits inducible nitric oxide synthase protein expression and nitric oxide production in beta-amyloid stimulated PC12 neurons through p38 MAP kinase and NF-kappaB involvement.

In view of the pro-inflammatory scenario observed in Alzheimer's disease, in the recent years anti-inflammatory drugs have been proposed as potential therapeutic agents. We have previously shown that cannabidiol, the main non-psychotropic component from Cannabis sativa, possess a variegate combination of anti-oxidant and anti-apoptotic effects that protect PC12 cells from Abeta toxicity. In parallel, cannabidiol has been described to have anti-inflammatory properties in acute models of inflammation but the possible inhibitory effect of cannabidiol on iNOS protein expression and nitrite production in the nitrosative stress induced by Abeta in neuronal cell-line is un-investigated. Stimulation of differentiated PC12 cells with Abeta (1-42) (1 microg/mL) for 36 h caused a significant increase of nitrite production, compared to un-stimulated cells, that was inhibited in a concentration-dependent manner by both the non-selective iNOS inhibitor, L-NAME (0.3-30 microM), and, at higher extent, by the selective iNOS inhibitor SMT (0.3-30 microM). CBD (10(-6) to 10(-4) M) inhibited both nitrite production and iNOS protein expression induced by Abeta (1-42). Cannabidiol effect was mediated through the inhibition of phosphorylated form of p38 MAP kinase and transcription factor nuclear factor-kappaB activation in a concentration-dependent manner. The here reported data increases our knowledge about the possible neuroprotective mechanism of cannabidiol, highlighting the importance of this compound to inhibit beta-amyloid induced neurodegeneration, in view of its low toxicity in humans.

Amyloid beta-Peptides↗
PubMed2004

Decrease in arterial pressure induced by adrenomedullin in the hypothalamic paraventricular nucleus is mediated by nitric oxide and GABA.

We tested the hypothesis that the decrease in arterial pressure induced by adrenomedullin (ADM) in the hypothalamic paraventricular nucleus (PVN) is mediated by nitric oxide (NO) and/or GABA. Unilateral microinjections of ADM into the PVN of anesthetized rats caused a significant decrease in mean arterial pressure (MAP). The ADM-induced decrease in MAP was significantly attenuated by pretreatment with N(psi)-nitro-L-arginine methyl ester (L-NAME, a non-selective NOS inhibitor), 7-nitroindazole sodium salt (7-NiNa, a selective neuronal NOS inhibitor), N5-(1-Iminoethyl)-L-ornithine (L-NIO, a selective endothelial NOS inhibitor) or bicuculline methiodide, but pretreatment with S-methylisothiourea (SMIT, a selective inducible NOS inhibitor) had no effect on this ADM-induced effect. In addition, coronal sections of rat brains were processed for combined NADPH-diaphorase (a marker of neuronal NOS-containing neurons) histochemistry and in situ hybridization for the receptor-activity-modifying protein 2 (a specific ADM receptor component). Double-labeled neurons were found in both parvocellular and magnocellular subdivisions of the PVN, confirming that NO-producing neurons in the PVN are capable of mediating ADM's effects. Thus, our data provide evidence that the ADM-induced decrease in MAP in the PVN is mediated by NO from neuronal and endothelial NOS, and by GABA.

Adrenomedullin↗
PubMed2005

High levels of endogenous nitric oxide produced after burn injury in rats arrest activated T lymphocytes in the first G1 phase of the cell cycle and then induce their apoptosis.

Major physical traumas provoke a systemic inflammatory response and immune dysfunction. In a model of thermal injury in rats, we previously showed that an overproduction of nitric oxide (NO) was responsible for the collapse of lymphoproliferative responses. In the present work, we performed a time-course analysis of cell proliferation and cell death parameters in order to establish the sequence of events triggered by the high NO output in Wistar/Han rat splenocytes activated with Con A, 10 days after burn injury. We demonstrate that activated T cells from burned rats never divided whereas normal T cells underwent four division cycles. However, T cells from both burned and normal rat entered the G1 phase as shown by increase of cell size, mitochondria hyperpolarization, and expression of cyclin D1. Burned rat T cells progressed to the late G1 phase as shown by expression of the nuclear Ki-67 antigen, but they never entered the S phase. They underwent apoptosis as shown by morphological parameters, disruption of transmembrane mitochondrial potential, and DNA fragmentation. Persistent accumulation of the p53 protein accompanied these phenomena. NO synthase inhibitors antagonize alterations of cell proliferation and cell death parameters in burned rat T cells and accelerated p53 turnover.

Animals↗
PubMed2003

Lipopolysaccharide down-regulates inducible nitric oxide synthase expression in swine heart in vivo.

Studies of the regulation of iNOS expression have provided many contradictory results. Comparing iNOS expression profile between cell types or organs of the same animal under the same experimental conditions may provide an explanation for these conflicting results. We have examined iNOS mRNA and protein expression in heart and liver of the same group of pigs. We found that there is a sharp difference in iNOS expression between heart and liver. The iNOS mRNA and protein was constitutively expressed in the heart at high level, but was not detectable in the liver of the same control animal. Lipopolysaccharide (LPS, 100 microg/kg, i.v.) caused a marked iNOS induction in the liver, but significantly down-regulated iNOS expression in the heart. This differential iNOS expression appears to be physiologically relevant, since LPS and the iNOS inhibitor, S-methylisothiourea, exerted different effects on hepatic and myocardial blood flow. Our data demonstrate a fundamental difference in iNOS regulation in the heart and liver of swine, and may explain the contradictory data on the regulation of iNOS expression.

Animals↗
PubMed1996

Brain penetration of the histamine H3 receptor antagonists thioperamide and clobenpropit in rat and mouse, determined with ex vivo [125I]iodophenpropit binding.

We investigated the brain penetration of the histamine H3 receptor antagonists thioperamide and clobenpropit using ex vivo [125I]iodophenpropit binding. Homogenates of the rat cortex, striatum and mouse whole brain were prepared 1 h after subcutaneous injection of the H3 antagonists and incubated with [125I]iodophenpropit, a radiolabeled H3 receptor antagonist, to determine the H3 receptor occupancy. Specific [125I]iodophenpropit binding to the rat cortex and striatum was inhibited by thioperamide with IC30 values of 1.0 and 1.5 mg/kg, respectively. Clobenpropit also inhibited [125I]iodophenpropit binding, but was less potent (IC30: 18 and 19 mg/kg in the rat cortex and striatum, respectively) than thioperamide. Similar results were obtained in experiments with mouse whole brain (3.5 and 13 mg/kg for thioperamide and clobenpropit), indicating that there is no important species differences in the brain penetration of these drugs between rats and mice. These findings suggest that after peripheral injection both in rat and mouse thioperamide penetrates the blood-brain barrier more efficiently compared to clobenpropit.

Animals↗
PubMed1998

Pharmacological characterisation of the histamine H3 receptor in the rat hippocampus.

The purpose of this report was to pharmacologically characterise the histamine H3 in the rat hippocampus using radioligand binding studies with the H3 receptor antagonist [125I]iodophenpropit and the H3 receptor mediated inhibition of [3H]noradrenaline release. A dissociation constant of 0.33 nM and a maximal number of binding sites of 125 fmol/mg protein were found for [125I]iodophenpropit. Competition studies showed stereoselectivity for the (R) and (S) enantiomers of alpha-methylhistamine and 10 microM of GTPgammaS shifted the curve of (R)-alpha-methylhistamine rightwards. Up to 1 microM, (R)-alpha-methylhistamine displaced only 30% whereas the tested H3-antagonists displaced 50-60% of the total [125I]iodophenpropit bound. This indicates the presence of an additional non-H3 receptor binding site(s) for [125I]iodophenpropit in the rat hippocampus. This secondary site shows low affinity for H3 agonists, but high affinity for the tested H3 antagonists. Electrically evoked [3H]acetylcholine release was shown in slices of rat hippocampus. No H3 receptor modulation of [3H]acetylcholine release from hippocampal slices was detectable. However, H3 receptor activation inhibited 42% of the electrically-evoked [3H]noradrenaline release in rat hippocampal slices. The inhibition of [3H]noradrenaline release was effectively antagonized by the H3 antagonists thioperamide and burimamide. We describe the pharmacological identification of the histamine H3 receptor in the rat hippocampus and its similarities and differences from the cortical H3 receptor. These studies enable us to investigate changes in density and functionality of the hippocampal H3 receptor under (patho)physiological conditions.

Acetylcholine↗
PubMed2001

Intestinal ischemia induces late preconditioning against myocardial infarction: a role for inducible nitric oxide synthase.

OBJECTIVE: We tested the hypothesis that occlusion of the superior mesenteric artery induces late preconditioning against myocardial infarction and examined the effects of pharmacological modifiers of inducible nitric oxide synthase activity on the late preconditioning in anesthetized rats. METHODS: Rats underwent an intestinal ischemia preconditioning protocol (30 min occlusion of the superior mesenteric artery) or were sham-operated. They were subjected to a sustained 30 min of coronary occlusion and 180 min of reperfusion 24 h later. RESULTS: In rats receiving no pharmacological intervention, the percentage of myocardial infarct within the area at risk and left ventricle was 72+/-4% and 31+/-2%, respectively, in sham-operated rats, and these were significantly reduced to 44+/-4% and 23+/-2% (P<0.01) 24 h after intestinal ischemia preconditioning. Myeloperoxidase activity was significantly reduced by intestinal ischemia preconditioning. Administration of aminoguanidine (300 mg/kg, s.c.) or S-methylisothiourea sulfate (3 mg/kg, i.v.), both relative inducible NO synthase inhibitors, 60 or 30 min before sustained myocardial ischemia not only abolished the late preconditioning afforded by intestinal ischemia, but also inhibited the ability of intestinal ischemia preconditioning to significantly reduce neutrophil infiltration. A change in inducible NO synthase activity was not observed in normal myocardium 24 h after intestinal ischemia, but 30 min of coronary occlusion significantly increased the inducible NO synthase activity in the preconditioned group, which was abolished by aminoguanidine or S-methylisothiourea sulfate. CONCLUSIONS: These data provide pharmacological evidence that induction of inducible nitric oxide synthase, following intestinal ischemia, is associated with increased myocardial tolerance to infarction 24 h later.

Analysis of Variance↗
PubMed2001

Expression of inducible nitric oxide synthase in primary culture of rat bladder smooth muscle cells by plasma from cyclophosphamide-treated rats.

Intraperitoneal administration of cyclophosphamide (50-150 mg/kg) for 6 or 12 h induced edema and hemorrhagic changes in rat bladder, which were both dose and time-dependent. Pretreatment with nitric oxide synthase (NOS) inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME, 40 mg/kg) or with s-methylisothiourea (40 mg/kg) ameliorated the cyclophosphamide-induced cystitis. Cyclophosphamide administration also produced increases in NO-metabolite levels (nitrate+nitrite) in the urine and plasma of rats. Greater increases in NO metabolites were observed with 150 than with 50 mg/kg of cyclophosphamide, and at 12 than at 6 h after cyclophosphamide injection. Pretreatment with L-NAME and s-methylisothiourea significantly reduced cyclophosphamide-induced increases in urine and plasma NO-metabolite levels. To explore the mechanism by which cyclophosphamide increases the expression of inducible NOS (iNOS), primary cultures of rat bladder smooth muscle were developed. Exposure to tumor necrosis factor alpha (TNF-alpha) plus interferon gamma, produced a marked increase in the expression of iNOS and in NO production in the culture medium. However, exposure to cyclophosphamide or to its metabolite acrolein (10(-6)-10(-4) M for 24 h) did not increase iNOS or NO-metabolite levels. On the other hand, incubation of primary cell cultures with plasma from rats treated with cyclophosphamide (150 mg/kg, 12 h) produced a marked increase in iNOS expression and NO production. Taken together, our results indicate that NO plays an important role in the pathogenesis of cyclophosphamide-induced cystitis in rats, and some factors may be released in cyclophosphamide-treated rat plasma which stimulate iNOS expression in primary culture of rat bladder smooth muscle cells.

Acrolein↗
PubMed1998

Agonist and antagonist effects of histamine H3 receptor ligands on 5-HT3 receptor-mediated ion currents in NG108-15 cells.

The ability of histamine H3 receptor ligands to interact with 5-HT3 receptors in NG108-15 cells was studied using the whole cell patch clamp recording technique. Imetit, a histamine H3 receptor agonist, generated inward currents and exhibited weak partial agonist activity at the 5-HT3 receptor (EC50 = 11.8 microM). Imetit-induced currents were slow to desensitize and at a high concentration reduced in size. The histamine H3 receptor antagonists iodophenpropit and thioperamide did not generate inward currents but were able to inhibit 5-hydroxytryptamine (5-HT) responses with an IC50 of 1.57+/-0.3 microM and 13.7+/-3.5 microM, respectively. Thioperamide is probably a non-competitive antagonist which may have more than one binding site on the receptor.

Animals↗
PubMed1999

Dose-dependent attenuation of lipopolysaccharide-fever by inhibitors of inducible nitric oxide-synthase in guinea pigs.

Different doses of aminoguanidine or S-methylisothiourea, both predominantly inhibitors of the inducible form of nitric oxide (NO)-synthase, were injected into the arterial circulation of guinea pigs alone or along with 10 microg/kg bacterial lipopolysaccharide. Doses of 10 mg/kg, 50 mg/kg or 250 mg/kg aminoguanidine per se had no influence on abdominal temperature of guinea pigs. Only the highest dose of aminoguanidine (250 mg/kg) completely suppressed the first phase of the biphasic febrile response to lipopolysaccharide-injections. Lipopolysaccharide-fever was not modulated by administration of 10 mg/kg or 50 mg/kg aminoguanidine, when compared to fever in response to injections of lipopolysaccharide along with solvent. Doses of 10 mg/kg or 50 mg/kg S-methylisothiourea did not alter abdominal temperature while a dose of 250 mg/kg S-methylisothiourea had a lethal effect in guinea pigs. The febrile response to lipopolysaccharide was unimpaired by administration of 10 mg/kg S-methylisothiourea, while a dose of 50 mg/kg again attenuated fever predominantly by a suppression of the first fever phase. None of the applied doses of aminoguanidine or S-methylisothiourea resulted in a significant attenuation of the lipopolysaccharide-induced circulating cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6. The drugs themselves, without lipopolysaccharide-injections, did not enhance or reduce circulating levels of the investigated cytokines. The results indicate that endogenous NO may participate in the induction of lipopolysaccharide-fever and that fever suppression by systemic administration of NO-synthase inhibitors occurs independently from the lipopolysaccharide-induced circulating cytokines.

Animals↗
PubMed1996

Selective inhibition of the inducible isoform of nitric oxide synthase prevents pulmonary transvascular flux during acute endotoxemia.

The inducible isoform of nitric oxide synthase (iNOS) is expressed in various organs, including the lung, during systemic endotoxemia. Overproduction of nitric oxide (NO) by iNOS contributes significantly to the vascular failure and end-organ damage in endotoxemia. Using selective pharmacological inhibitors of iNOS, the purpose of this study was to define the role of iNOS in a rat model of endotoxin-induced pulmonary transvascular flux (TVF). Lung TVF was assessed by a method of Evans Blue permeability index (PI). Bacterial lipopolysaccharide (LPS) (15 mg/kg intraperitoneally [IP]) significantly increased pulmonary iNOS activity and serum levels of nitrite/nitrate (NO2/NO3). This was accompanied by a significant elevation of the PI 5 hours after injection. Selective iNOS inhibition with either S-methyl isothiourea (SMT; 5 mg/kg IP) or aminoguanidine (AG; 20 mg/kg IP), administered 2 hours after LPS injection, significantly prevented the increase in PI associated with LPS injection. Similarly, inhibition of the induction of iNOS with dexamethasone (10 mg/kg IP), given 3 hours before LPS, also inhibited the increase in PI. All three treatments significantly prevented the increase in both lung iNOS activity and serum NO2/NO3 associated with endotoxemia. In conclusion, the overproduction of NO generated by iNOS during systemic endotoxemia causes a vascular leak in the lung. Thus, it is speculated that selective inhibition of iNOS may be beneficial in preventing the development of acute respiratory failure in sepsis.

Acute Disease↗
PubMed1997

Comparison of the inhibitory effect of isothiourea and mercapto-alkylguanidine derivatives on the alternative pathways of arginine metabolism in macrophages.

Novel, non-arginine based compounds have been identified as potent inhibitors of nitric oxide synthase (NOS). Members of the isothiourea and mercapto-alkylguanidine classes have generated much interest, as some members of these classes show selectivity towards the inducible isoform of NOS (iNOS), which plays a role in inflammation and shock. Here we compared the effect of a number of these compounds as well as L-arginine based NOS inhibitor reference compounds on macrophage-derived and liver arginase and macrophage iNOS activities. From the non-arginine based NOS inhibitors studied only S-aminoethyl-isothiourea (AETU) caused a slight inhibition of arginase activity. This inhibition was kinetically competitive and due to the rearrangement of AETU to mercapto-ethylguanidine (MEG). The weak inhibitory effect of non-arginine based iNOS inhibitors on arginase activity further supports the view that such compounds may be of practical use for inhibition of NO production in cells simultaneously expressing iNOS and arginase.

Animals↗
PubMed1997

Inhibition of nitric oxide synthases enhances the effect of ACTH in hemorrhagic shock.

In a model of volume-controlled hemorrhagic shock in rats, invariably leading to death within 30 min of bleeding termination, the intravenous (i.v.) bolus injection of ACTH-(1-24) at the dose of 0.16 mg/kg restored cardiovascular and respiratory functions and greatly prolonged survival. I.v. or intracerebroventricular (i.c.v.) treatment with NG-nitro-L-arginine methylester (L-NAME), a non-isoform-selective inhibitor of nitric oxide synthases (NOSs), at the doses of 2.5-10 mg/kg i.v. or 0.015-0.135 mg/kg i.c.v., as well as i.v. treatment with S-methylisothiourea (SMT), a selective inhibitor of the inducible isoform of NOS, at the doses of 0.001-3 mg/kg, dose-dependently improved cardiovascular and respiratory functions and potentiated the effect of a subthreshold dose (0.02 mg/kg) of ACTH-(1-24). On the other hand, either intraperitoneal or i.c.v. pretreatment with L-arginine, the substrate of NOSs, prevented the effect of ACTH-(1-24). These data suggest that inhibition of NO overproduction is involved in the mechanism of action of ACTH-(1-24) in shock reversal.

Animals↗
PubMed1999

Interleukin-1beta causes different levels of nitric oxide-mediated depression of contractility in different positions of rat thoracic aorta.

Interleukin-1beta (IL-1beta) can be synthesized by macrophages, endothelial cells and vascular smooth muscle cells when stimulated by bacterial lipopolysaccharide (endotoxin) during septic shock. The IL-1beta levels in the blood vessel wall are also elevated in atherosclerosis. IL-1beta can cause induction of inducible nitric oxide synthase (iNOS) expression in vascular smooth muscle cells and produce vasorelaxation, hypotension and ultimately tissue damage. We studied the depressions of vascular smooth muscle contractions at 3 hours after exposure to IL-1beta in different positions of rat thoracic aorta. The data show that the aortic rings from the cranial end of rat thoracic aorta had little response to IL-1beta (0.5 and 1.0 ng/ml) while those from the caudal end of thoracic aorta had larger depressant response. S-methylisothiourea sulfate (SMT), an iNOS inhibitor, completely blocked the depression of contraction caused by IL-1beta in intact aortic rings. If the endothelium was removed from the aortic rings before exposure to IL-1beta, all rings from different parts of the thoracic aorta showed an equal amount of vasodepression. Thus, the difference in the depressant response of IL-1beta in different portions of thoracic aorta is endothelium-dependent and involves induction of NOS.

Animals↗
PubMed2000

Mapping the active site polarity in structures of endothelial nitric oxide synthase heme domain complexed with isothioureas.

Analyzing the active site topology and plasticity of nitric oxide synthase (NOS) and understanding enzyme-drug interactions are crucial for the development of potent, isoform-selective NOS inhibitors. A small hydrophobic pocket in the active site is identified in the bovine eNOS heme domain structures complexed with potent isothiourea inhibitors: seleno analogue of S-ethyl-isothiourea, S-isopropyl-isothiourea, and 2-aminothiazoline, respectively. These structures reveal the importance of nonpolar van der Waals contacts in addition to the well-known hydrogen bonding interactions between inhibitor and enzyme. The scaffold of a potent NOS inhibitor should be capable of donating hydrogen bonds to as well as making nonpolar contacts with amino acids in the NOS active site.

Binding Sites↗
PubMed2001

Lipopolysaccharide-induced cell cycle arrest in macrophages occurs independently of nitric oxide synthase II induction.

Lipopolysaccharide (LPS, a Gram-negative bacterium cell wall component) is a potent macrophage activator that inhibits macrophage proliferation and stimulates production of nitric oxide (NO) via NO synthase II (NOSII). We investigated whether NO mediates the LPS-stimulated cell cycle arrest in mouse bone marrow-derived macrophages (BMM). The addition of the NO donor DETA NONOate (200 microM) inhibited BMM proliferation by approx. 80%. However, despite NO being an antimitogen, LPS was as potent at inhibiting proliferation in BMM derived from NOSII-/- mice as from wild-type mice. Consistent with these findings, LPS-induced cell cycle arrest in normal BMM was not reversed by the addition of the NOSII inhibitor S-methylisothiourea. Moreover, in both normal and NOSII-/- BMM, LPS inhibited the expression of cyclin D1, a protein that is essential for proliferation in many cell types. Despite inhibiting proliferation DETA NONOate had no effect on cyclin D1 expression. Our data indicate that while both LPS and NO inhibit BMM proliferation, LPS inhibition of BMM proliferation can occur independently of NOSII induction.

Animals↗