Effect of multiple cytokines plus bacterial endotoxin on glucose and nitric oxide production by cultured hepatocytes.
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ABSTRACT:
SUBMITTER: Ceppi ED
PROVIDER: S-EPMC1217515 | biostudies-other | 1996 Jul
REPOSITORIES: biostudies-other
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Project description:Metabolic intermediates influence inflammation not only through signaling effects, but also by fueling the production of pro-inflammatory molecules. Microglial production of nitric oxide (NO) requires the consumption of NADPH. NADPH consumed in this process is regenerated from NADP+ primarily through the hexose monophosphate shunt, which can utilize only glucose as a substrate. These factors predict that glucose availability can be rate-limiting for glial NO production. To test this prediction, cultured astrocytes and microglia were incubated with lipopolysaccharide and interferon-γ to promote expression of inducible nitric oxide synthase, and the rate of NO production was assessed at defined glucose concentrations. Increased NO production was detected only in cultures containing microglia. The NO production was markedly slowed at glucose concentrations below 0.5 mM, and comparably reduced by inhibition of the hexose monophosphate shunt with 6-aminonicotinamide. Reduced NO production caused by glucose deprivation was partly reversed by malate, which fuels NADPH production by malate dehydrogenase, and by NADPH itself. These findings highlight the role of the hexose monophosphate shunt in fueling NO synthesis and suggest that microglial NO production in the brain may be limited at sites of low glucose availability, such as abscesses or other compartmentalized infections.
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Project description:Licorice (Glycyrrhizae radix) is the roots and stolons of Glycyrrhiza uralensis Fischer or Glycyrrhiza glabra Linnaeus in the Japanese Pharmacopoeia. Glycyrrhizae radix has been widely used as a sweetener and a traditional medicine. A Glycyrrhizae radix extract contains many constituents and has antispasmodic, antitussive, anti-ulcer, and anti-inflammatory effects. However, reports comparing the anti-inflammatory effects of these constituents are very few. Here, we purified several constituents from the roots and stolons of G. uralensis and examined and compared their anti-inflammatory effects by monitoring the levels of the inflammatory mediator, nitric oxide (NO), in interleukin (IL)-1β-treated rat hepatocytes. From the G. uralensis extract, we purified the main constituent glycyrrhizin and the constituents that are characteristic of G. uralensis (chalcones and flavanones). These constituents suppressed NO production in IL-1β-treated rat hepatocytes, and isoliquiritigenin showed the greatest suppression activity. Isoliquiritigenin, isoliquiritin, and liquiritigenin significantly decreased both protein and mRNA for the inducible nitric oxide synthase. These constituents reduced the levels of mRNAs encoding tumor necrosis factor α and IL-6. In contrast, although glycyrrhizin is abundant, it showed a 100-fold lower potency in NO suppression. Therefore, both glycyrrhizin and the minor constituents (isoliquiritigenin, isoliquiritin, and liquiritigenin) may be responsible for the anti-inflammatory effects of G. uralensis. It is also implied that these constituents may have a therapeutic potential for inflammatory hepatic disorders.
| S-EPMC5668654 | biostudies-literature
Project description:Activated hepatic stellate cells play a major role in the pathophysiology of chronic liver disease. They can influence the metabolism of hepatocytes by producing a variety of cytokines and growth factors. Upon stimulation with endotoxin, stellate cells also synthesize nitric oxide (NO), a potent mediator of growth of several cell types including hepatocytes. We investigated the effect of serum-free medium conditioned by activated stellate cells in the absence and presence of endotoxin on NO and DNA synthesis in hepatocytes. Stellate cells and hepatocytes were isolated by enzymatic digestion of the liver. Stellate cells were cultured for 10 days after which the majority exhibited alpha-smooth muscle actin (a marker for activated cells); hepatocytes were used after overnight culture. While the medium conditioned by stellate cells in the absence of endotoxin stimulated DNA synthesis in hepatocytes, medium conditioned in its presence inhibited this process in an endotoxin concentration-dependent manner (10 - 1000 ng ml(-1)). Endotoxin-conditioned stellate cell medium also stimulated NO synthesis in hepatocytes; the effect was consistent with increased protein and mRNA expression of inducible NO synthase (iNOS). However, inhibition of DNA synthesis in hepatocytes caused by endotoxin-conditioned stellate cell medium was unaffected by the NOS inhibitor, L-N(G)-monomethylarginine (L-NMMA), guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and neutralizing antibodies for TGF-beta, IL-1beta, IL-6 and TNF-alpha. These results indicate that factors other than these cytokines produced by activated stellate cells upon stimulation with endotoxin or by hepatocytes challenged with endotoxin-conditioned stellate cell medium inhibit DNA synthesis in hepatocytes.
| S-EPMC1572860 | biostudies-other
Project description:1. In the present experiments, we investigated the effects of methylecgonidine (MEG) on nitric oxide (NO) production in cultured neonatal rat cardiomyocytes. Incubation of cultured cardiomyocytes with carbachol or MEG for 48 h significantly enhanced NO production. No release was increased from 1.48+/-0.13 microM (mg protein)(-1) for control to 5.73+/-0.19 microM (mg protein)(-1) for 1 microM carbachol treated cells (P<0.001). In addition, incubation with 1 microM MEG enhanced NO production to 5.55+/-0.28 microM (mg protein)(-1). The effects of MEG on NO production were concentration-dependent. The muscarinic antagonist atropine prevented the enhancement of NO production induced by carbachol or MEG. Compared to MEG-induced NO production, cocaine was much less potent. 2. The enhancement of NO production by carbachol or MEG was even greater in cultured cardiomyocytes transfected with the M(2) cDNA. After 48-h incubation with 1 microM carbachol or 1 microM MEG, NO production was increased by 6.5 and 6.7 fold, respectively, in cardiomyocytes overexpressing M(2) receptors. Coincubation with atropine or N(G)-nitro-L-arginine methyl ester abolished the enhancement of NO production. In contrast, NO production enhanced by carbachol or MEG in M(1)- or M(3)-transfected cardiomyocytes was similar to the level in non-transfected cells. 3. Western blot analysis showed that the protein levels of M(1), M(2), and M(3) were significantly increased in cardiomyocytes transfected with the receptor cDNAs, but MEG had no effect on the expressions. It is interesting that both carbachol and MEG caused a significant increase in constitutive endothelial NO synthase (eNOS) only in M(2)-transfected cardiomyocytes, not in non-transfected, M(1)- or M(3)-transfected cells. Again, atropine blocked the MEG-produced induction of eNOS. 4. Our data demonstrate that MEG significantly enhanced NO production in cultured cardiomyocytes and that the enhancement of NO production may result from MEG stimulation of muscarinic M(2) receptors.
| S-EPMC1573099 | biostudies-other
Project description:Nitric oxide (NO) inhibits myocardial glucose transport and metabolism, although the underlying mechanism(s) and functional consequences of this effect are not clearly understood. We tested the hypothesis that NO inhibits the activation of AMP-activated protein kinase (AMPK) and translocation of cardiac glucose transporters (GLUTs; GLUT-4) and reduces lactate production. Ischemia was induced in open-chest dogs by a 66% flow reduction in the left anterior descending coronary artery (LAD). During ischemia, dogs were untreated (control) or treated by direct LAD infusion of (i) nitroglycerin (NTG) (0.5 microg.kg(-1).min(-1)); (ii) 8-Br-cGMP (50 microg.kg(-1).min(-1)); or (iii) NO synthase inhibitor L-nitro-argininemethylester (40 microg.kg(-1).min(-1); n = 9 per group). Cardiac substrate oxidation was measured with isotopic tracers. There were no differences in myocardial blood flow or oxygen delivery among groups; however, at 45 min of ischemia, the activation of AMPK was significantly less in NTG (77 +/- 12% vs. nonischemic myocardium) and 8-Br-cGMP (104 +/- 13%), compared with control (167 +/- 17%). Similarly, GLUT-4 translocation was significantly reduced in NTG (74 +/- 7%) and 8-Br-cGMP (120 +/- 11%), compared with control (165 +/- 17%). Glucose uptake and lactate output were 30% and 60% lower in NTG compared with control. Inhibition of NO synthesis stimulated glucose oxidation (67% increase compared with control) but did not affect AMPK phosphorylation, GLUT-4 translocation and glucose uptake. Contractile function in the ischemic region was significantly improved by NTG and L-nitro-argininemethylester. In conclusion, in ischemic myocardium an NO donor inhibits glucose uptake and lactate production via a reduction in AMPK stimulation of GLUT-4 translocation, revealing a mechanism of metabolic modulation and myocardial protection activated by NO donors.
| S-EPMC1100777 | biostudies-literature
Project description:Nitric Oxide (NO), a potent vasodilator and vital signaling molecule, has been shown to contribute to the regulation of glomerular ultrafiltration. However, whether changes in NO occur in podocytes during the pathogenesis of salt-sensitive hypertension has not yet been thoroughly examined. We showed here that podocytes produce NO, and further hypothesized that hypertensive animals would exhibit reduced NO production in these cells in response to various paracrine factors, which might contribute to the damage of glomeruli filtration barrier and development of proteinuria. To test this, we isolated glomeruli from the kidneys of Dahl salt-sensitive (SS) rats fed a low salt (LS; 0.4% NaCl) or high salt (HS; 4% NaCl, 3 weeks) diets and loaded podocytes with either a combination of NO and Ca2+ fluorophores (DAF-FM and Fura Red, respectively) or DAF-FM alone. Changes in fluorescence were observed with confocal microscopy in response to adenosine triphosphate (ATP), angiotensin II (Ang II), and hydrogen peroxide (H2O2). Application of Ang II resulted in activation of both NO and intracellular calcium ([Ca2+]i) transients. In contrast, ATP promoted [Ca2+]i transients, but did not have any effects on NO production. SS rats fed a HS diet for 3 weeks demonstrated impaired NO production: the response to Ang II or H2O2 in podocytes of glomeruli isolated from SS rats fed a HS diet was significantly reduced compared to rats fed a LS diet. Therefore, glomerular podocytes from hypertensive rats showed a diminished NO release in response to Ang II or oxidative stress, suggesting that podocytic NO signaling is dysfunctional in this condition and likely contributes to the development of kidney injury.
| S-EPMC5776695 | biostudies-literature
Project description:Chronic alcohol consumption results in hepatotoxicity, steatosis, hypoxia, increased expression of inducible nitric oxide synthase (iNOS) and decreased activities of mitochondrial respiratory enzymes. The impact of these changes on cellular respiration and their interaction in a cellular setting is not well understood. In the present study we tested the hypothesis that nitric oxide (NO)-dependent modulation of cellular respiration and the sensitivity to hypoxic stress is increased following chronic alcohol consumption. This is important since NO has been shown to regulate mitochondrial function through its interaction with cytochrome c oxidase, although at higher concentrations, and in combination with reactive oxygen species, can result in mitochondrial dysfunction. We found that hepatocytes isolated from alcohol-fed rats had decreased mitochondrial bioenergetic reserve capacity and were more sensitive to NO-dependent inhibition of respiration under room air and hypoxic conditions. We reasoned that this would result in greater hypoxic stress in vivo, and to test this, wild-type and iNOS(-/-) mice were administered alcohol-containing diets. Chronic alcohol consumption resulted in liver hypoxia in the wild-type mice and increased levels of hypoxia-inducible factor 1 ? in the peri-venular region of the liver lobule. These effects were attenuated in the alcohol-fed iNOS(-/-) mice suggesting that increased mitochondrial sensitivity to NO and reactive nitrogen species in hepatocytes and iNOS plays a critical role in determining the response to hypoxic stress in vivo. These data support the concept that the combined effects of NO and ethanol contribute to an increased susceptibility to hypoxia and the deleterious effects of alcohol consumption on liver.
| S-EPMC3217123 | biostudies-literature
Project description:The principal goal of the present study was to test the hypothesis that cytokines modulate glucose transport in skeletal muscle by increasing nitric oxide production. Cultured L6 skeletal muscle cells were incubated in the presence of tumour necrosis factor-alpha, interferon-gamma or lipopolysaccharide (LPS) alone or in combination for 24 h. Neither cytokines nor LPS alone induced NO production, as measured by nitrite concentrations in the medium. However, when used in combination, the two cytokines significantly stimulated NO production, and this effect was synergistically enhanced by the presence of LPS. Reverse transcriptase-PCR (RT-PCR) analysis revealed that NO release was associated with the induction of inducible (macrophage-type) NO synthase (iNOS). The increase in iNOS expression was confirmed at the protein level by Western-blot analysis and NADPH/diaphorase histochemical staining. Cytokines and LPS markedly increased basal glucose transport in L6 myocytes. Insulin also stimulated basal glucose transport, but significantly less in cells chronically exposed to cytokines/LPS. The sensitivity of L6 muscle cells to insulin-stimulated glucose transport was also significantly decreased by cytokines/LPS treatment. The NOS inhibitor NG-nitro-l-arginine methyl ester (l-NAME) inhibited nitrite production in cytokine/LPS-treated cells, and this prevented the increase in basal glucose transport and restored muscle cell responsiveness to insulin. Cytokines/LPS exposure significantly increased GLUT1 transporter protein levels but decreased GLUT4 expression in L6 cells. l-NAME treatment prevented the increase in GLUT1 protein content but failed to restore GLUT4 transporter levels. These results demonstrate that cytokines and LPS affect glucose transport and insulin action by inducing iNOS expression and NO production in skeletal muscle cells. The data further indicate that cytokines and LPS increase the expression of the GLUT1 transporter protein by an NO-dependent mechanism.
| S-EPMC1218586 | biostudies-other
Project description:An activity-guided fractionation approach revealed several phenylpropanoid glycerol glucosides isolated from the bulbs of Lilium longiflorum Thunb. (Easter lily) with gluconeogenesis inhibitory activities. The strongest activity was observed for (2S)-1-O-p-coumaroyl-2-O-β-d-glucopyranosylglycerol (3), (2S)-1-O-caffeoyl-2-O-β-d-glucopyranosylglycerol (1), and (2R)-1-O-β-d-glucopyranosyl-2-O-p-coumaroylglycerol (2) with inhibitions of 51.2, 39.2, and 36.8%, respectively. The p-coumaroyl-based (3) and its acetylated derivative (5) exhibited differential inhibition activity (51.2% as compared to 3.6%), suggesting that natural acetylation decreases the hypoglycemic activity of these compounds. Direct structure-activity analysis of phenylpropanoid glycerol glucosides indicated that the hydroxylation pattern of the hydroxy cinnamic acid moiety and acetylation were responsible for the differences in activity. This is the first report of phenylpropanoid glycerol glucosides as a phytochemical class of hepatic glucose production inhibitors.
| S-EPMC6648405 | biostudies-literature
Project description:SIGNIFICANCE:The molecule nitric oxide (NO) has been shown to regulate behaviors in bacteria, including biofilm formation. NO detection and signaling in bacteria is typically mediated by hemoproteins such as the bis-(3',5')-cyclic dimeric adenosine monophosphate-specific phosphodiesterase YybT, the transcriptional regulator dissimilative nitrate respiration regulator, or heme-NO/oxygen binding (H-NOX) domains. H-NOX domains are well-characterized primary NO sensors that are capable of detecting nanomolar NO and influencing downstream signal transduction in many bacterial species. However, many bacteria, including the human pathogen Pseudomonas aeruginosa, respond to nanomolar concentrations of NO but do not contain an annotated H-NOX domain, indicating the existence of an additional nanomolar NO-sensing protein (NosP). Recent Advances: A newly discovered bacterial hemoprotein called NosP may also act as a primary NO sensor in bacteria, in addition to, or in place of, H-NOX. NosP was first described as a regulator of a histidine kinase signal transduction pathway that is involved in biofilm formation in P. aeruginosa. CRITICAL ISSUES:The molecular details of NO signaling in bacteria are still poorly understood. There are still many bacteria that are NO responsive but do encode either H-NOX or NosP domains in their genomes. Even among bacteria that encode H-NOX or NosP, many questions remain. FUTURE DIRECTIONS:The molecular mechanisms of NO regulation in many bacteria remain to be established. Future studies are required to gain knowledge about the mechanism of NosP signaling. Advancements on structural and molecular understanding of heme-based sensors in bacteria could lead to strategies to alleviate or control bacterial biofilm formation or persistent biofilm-related infections.
| S-EPMC6217740 | biostudies-literature