Histochemical changes in the affinity of Alcian Blue 8GX for aging monkey kidneys, quantified by atomic absorption spectrophotometry.
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Age Factors↗
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Accumulation of gentamicin by Staphylococcus aureus: the role of the transmembrane electrical potential.
Accumulation of gentamicin by gentamicin-susceptible Staphylococcus aureus was examined by using the ionophorous antibiotic, valinomycin and the protontranslocating ATPase inhibitor N,N'-dicyclohexylcarbodiimide. The effects of these inhibitors on the transmembrane electrical potential (delta psi) were determined by measuring the equilibrium distribution of the tetraphenylphosphonium ion. The results indicate a direct correlation between delta psi and the extent of gentamicin uptake. However, under conditions where a significant delta psi existed across the plasma membrane, uptake of gentamicin was negligible. A threshold delta psi may thus be required to initiate gentamicin uptake. The proposed threshold delta psi appears to vary depending upon the external concentration of gentamicin.
Dicyclohexylcarbodiimide↗
Transmembrane electron transport in sealed and NAD(P)H-loaded right-side-out plasma membrane vesicles isolated from maize (Zea mays L.) roots.
Electron transport across plasma membranes has been observed in vivo in several plant species and tissues after the application of ferricyanide (hexacyanoferrate III, HCF III). In the present work, a transmembrane electron flow was demonstrated in sealed and NAD(P)H-loaded right-side-out (apoplastic-side-out) plasma membrane vesicles isolated from maize (Zea mays L.) roots. HCF III was reduced at a rate of up to 126 nmol min(-1) mg(-1) protein by NADPH-loaded vesicles, while reduction rates with NADH-loaded vesicles were several-fold lower. Coincident with the reduction of HCF III, NAD(P)H oxidation was observed inside the vesicles. The dependence of reduction on K+ indicated an electrogenic transmembrane electron flow. Application of 100 microM calcium decreased HCF III reduction up to 66%, while pre-incubation with 200 microM warfarin or diphenylene iodonium inhibited transmembrane electron transport only weakly. Fe(3+)-EDTA was not reduced significantly by NADPH-loaded plasma membrane vesicles, whereas XTT was reduced at a rate of 765 pmol min(-1) mg(-1) protein. The results suggested a major function for NADPH in transmembrane electron flow and were discussed in conjunction with in vivo experiments.
Biological Transport↗
Flavin-containing polyamine oxidase is a hydrogen peroxide source in the oxidative response to the protein phosphatase inhibitor cantharidin in Zea mays L.
In this study, the specific contribution of polyamine oxidase (PAO), a hydrogen peroxide (H2O2)-producing enzyme, to the oxidative burst induced in maize mesocotyl by the phosphatase inhibitor cantharidin was examined. For this purpose, a pharmacological approach was applied using, either in vitro or in vivo, two strong inhibitors of maize PAO (MPAO), N-prenylagmatine (G3) and its structural analogue Ro5, as well as diphenyleneiodonium (DPI), an inhibitor of the phagocyte NAD(P)H oxidase. DPI was shown to be a good MPAO inhibitor in vitro. G3, Ro5, and DPI were very effective in inhibiting in vivo the extracellular accumulation of H2O2 that is released by mesocotyl segments upon spermidine supply. G3 and Ro5 did not show any inhibition in vitro of either horseradish peroxidase or barley oxalate oxidase. Moreover, G3 and Ro5 did not inhibit the extracellular accumulation of superoxide radical that is released in vivo upon NADH supply. G3, Ro5, and DPI strongly affected H2O2 production induced in maize mesocotyl by cantharidin. Histochemical localization of H2O2 in cantharidin-treated mesocotyl cross-sections revealed an increase of H2O2-specific staining in the epidermal and subepidermal tissues. The effect was also inhibited by G3 and DPI. Moreover, an increase in MPAO activity was observed in the same tissues upon cantharidin treatment. All these data suggest that G3 and Ro5 behave as powerful and selective inhibitors of MPAO activity either in vitro or in vivo and that MPAO activity contributes to a major part of the cantharidin-induced H2O2 synthesis in the apoplastic milieu of maize mesocotyl.
Agmatine↗
Diphenyleneiodium (DPI) reduces oxalate ion- and calcium oxalate monohydrate and brushite crystal-induced upregulation of MCP-1 in NRK 52E cells.
BACKGROUND: Our earlier studies have demonstrated upregulation of monocyte chemoattractant protein-1 (MCP-1) in NRK52E rat renal epithelial cells by exposure to oxalate (Ox) ions and crystals of calcium oxalate monohydrate (COM) or the brushite (Br) form of calcium phosphate. The upregulation was mediated by reactive oxygen species (ROS). This study was performed to investigate whether NADPH oxidase is involved in ROS production. METHODS: Confluent cultures of NRK52E cells were exposed to Ox ions or COM and Br crystals. They were exposed for 1, 3, 6, 12, 24 and 48 h for isolation of MCP-1 mRNA and 24 h for enzyme-linked immunosorbent assay (ELISA) to determine the secretion of protein into the culture medium. We also investigated the effect of free radical scavenger, catalase, and the NADPH oxidase inhibitor diphenyleneiodium (DPI) chloride, on the Ox- and crystal-induced expression of MCP-1 mRNA and protein. The transcription of MCP-1 mRNA in the cells was determined using real-time polymerase chain reaction. Hydrogen peroxide and 8-isoprostane were measured to investigate the involvement of ROS. RESULTS: Exposure of NRK52E cells to Ox ions as well as the crystals resulted in increased expression of MCP-1 mRNA and production of the chemoattractant. Treatment with catalase reduced the Ox- and crystal-induced expression of both MCP-1 mRNA and protein. DPI reduced the crystal-induced gene expression and protein production but not Ox-induced gene expression and protein production. CONCLUSIONS: Exposure to Ox ions, and COM and Br crystals stimulates a ROS-mediated increase in MCP-1 mRNA expression and protein production. Reduction in ROS production, lipid peroxidation, low-density lipoprotein release, and inducible MCP-1 gene and protein in the presence of DPI indicates an involvement of NADPH oxidase in the production of ROS.
Animals↗
Characterization of the flavoprotein domain of gp91phox which has NADPH diaphorase activity.
A series of truncated forms of gp91phox were expressed in Escherichia coli in which the N-terminal hydrophobic transmembrane region was replaced with a portion of the highly soluble bacterial protein thioredoxin. TRX-gp91phox (306-569), which contains the putative FAD and NADPH binding sites, showed weak NADPH-dependent NBT (nitroblue tetrazolium) reductase activity, whereas TRX-gp91phox (304-423) and TRX-gp91phox (424-569) were inactive. Activity saturated at about a 1:1 molar ratio of FAD to TRX-gp91phox (306-569), and showed the same K(m) for NADPH as that for superoxide generating activity by the intact enzyme. Activity was not inhibited by superoxide dismutase, indicating that it was not mediated by superoxide, but was blocked by an inhibitor of the respiratory burst oxidase, diphenylene iodonium. In the presence of Rac1, the cytosolic regulatory protein p67phox stimulated the NBT reductase activity, but p47phox had no effect. Truncated p67phox containing the activation domain (residues 199-210) [C.-H. Han, J.R. Freeman, T. Lee, S.A. Motalebi, and J.D. Lambeth (1998) J. Biol. Chem. 273, 16663-16668] stimulated activity approximately 2-fold, whereas forms mutated or lacking this region failed to stimulate the activity. Our data indicate that: (i) TRX-gp91phox (306-569) contains binding sites for both pyridine and flavin nucleotides; (ii) this flavoprotein domain shows weak diaphorase activity; and (iii) the flavin-binding domain of gp91phox is the target of regulation by the activation domain of p67phox.
Binding Sites↗
DCCD-sensitive Na+-transport in the membrane vesicles of Halobacterium halobium.
The effects of N,N'-dicyclohexylcarbodiimide (DCCD) and various ionophores on light-induced 22Na+-transport were studied in right-side-out membrane vesicles from Halobacterium halobium R1M1. The light-induced Na+ efflux was inhibited at the same DCCD concentration (greater than 40 nmol/mg protein) as required for inhibition of the Na+-dependent membrane potential (delta phi) formation. This supports our previous indication that the DCCD-sensitive, Na+-dependent transformation of pH-gradient (delta pH) into delta phi is mediated by Na+/H+-antiporter (Murakami, N. and Konishi, T. (1985) J. Biochem. 98, 897-907). FCCP or a combination of valinomycin and triphenyltin (TPT) inhibits the light-induced Na+ efflux in accordance with the notion of protonmotive force (delta mu H+)-driven antiporter. However, a marked lag in initiation of the Na+ efflux occurred in the presence of valinomycin, TPMP+, or a small amount of FCCP, suggesting that a gating step is involved in the Na+ efflux. On the other hand, the delta pH-dissipating ionophore TPT did not cause the lag. A simultaneous determination of delta phi, delta pH, and Na+ efflux rate at the initial stage of illumination revealed that the antiporter is gated by delta phi rather than delta mu H+.
Biological Transport↗
Temperature dependence of action of polymyxin B on Escherichia coli.
The temperature dependence of the action of polymyxin B on Escherichia coli was studied by using K+, Ca2+, and tetraphenylphosphonium (TPP+) ion-selective electrodes. At room temperature (27 degrees C), Ca2+ was released immediately after addition of polymyxin, while the efflux of K+ occurred after 30 s. The rapid release of Ca2+ was not affected by incubation temperature, while the efflux of K+ was significantly lowered at temperatures below about 25-30 degrees C. The uptake of TPP+ also increased after polymyxin addition. The release of Ca2+ and the uptake of TPP+ supported the disruption of the outer membrane structure reported previously. In experiments with isolated membrane vesicles (the cytoplasmic membrane being exposed), the efflux of K+ was not delayed, but was lowered at temperatures below about 15-20 degrees C. This temperature range differed significantly from that of whole cells, and was interpreted as representing a difference in membrane fluidity between the outer and cytoplasmic membranes. The phase transition temperature of the outer membrane is known to be higher than that of the cytoplasmic membrane; and the temperature dependence of efflux of K+ from membrane vesicles was compatible with the phase transition temperature of liposomes prepared with phospholipids (not containing lipopolysaccharides) extracted from E. coli. Thus, it was speculated that, with whole cells, polymyxin molecules passed through the outer membrane at temperatures above the phase transition and reached the cytoplasmic membrane, increasing its K+ permeability. The mechanism of the permeability change is discussed in terms of deformation of the cytoplasmic membrane structure induced by polymyxin molecules.
Calcium↗
Phenylethylamine-induced generation of reactive oxygen species and ascorbate free radicals in tobacco suspension culture: mechanism for oxidative burst mediating Ca2+ influx.
In the previous paper [Kawano et al. (2000a) Plant Cell Physiol. 41: 1251], we demonstrated that addition of phenylethylamine (PEA) and benzylamine can induce an immediate and transient burst of active oxygen species (AOS) in tobacco suspension culture. Detected AOS include H2O2, superoxide anion and hydroxyl radicals. Use of several inhibitors suggested the presence of monoamine oxidase-like H2O2-generating activity in the cellular soluble fraction. It was also suggested that peroxidase(s) or copper amine oxidase(s) are involved in the extracellular superoxide production as a consequence of H2O2 production. Since more than 85% of the PEA-dependent AOS generating activity was localized in the extracellular space (extracellular fluid + cell wall), extracellularly secreted enzymes, probably peroxidases, may largely contribute to the oxidative burst induced by PEA. The PEA-induced AOS generation was also observed in the horseradish peroxidase (HRP) reaction mixture, supporting the hypothesis that peroxidases catalyze the oxidation of PEA leading to AOS generation. In addition to AOS production, we observed that PEA induced an increase in monodehydroascorbate radicals (MDA) in the cell suspension culture and in HRP reaction mixture using electron spin resonance spectroscopy and the newly invented MDA reductase-coupled method. Here we report that MDA production is an indicator of peroxidase-mediated generation of PEA radical species in tobacco suspension culture.
Amines↗
Inactivation of ycf33 results in an altered cyclic electron transport pathway around photosystem I in Synechocystis sp. PCC6803.
ycf33 encodes a small protein with a molecular mass of 7.5 kDa and is found from cyanobacteria to higher plants. A ycf33 deletion mutant was constructed in Synechocystis sp. PCC6803 and characterized. The mutant showed a higher phycobilisome/chlorophyll ratio than the wild type and a higher photosystem II/photosystem I fluorescence ratio measured at 77 K. Under photoautotrophic conditions, the growth rates were not much different from those of the wild type. Cyclic electron transport activities around photosystem I were not much different between the wild type and the mutant. However, the effects of diphenyleneiodonium, an inhibitor of flavoprotein, on cyclic electron transport in the mutant were different from those in the wild type; it was severely inhibited in the wild type but not much in the mutant. Together with the effects of nitrite, which accepts electrons from ferredoxin via nitrite reductase and those of HgCl2, it was suggested that the pathway of cyclic electron transport is altered in the mutant.
Amino Acid Sequence↗
Abscisic acid is a key inducer of hydrogen peroxide production in leaves of maize plants exposed to water stress.
The histochemical and cytochemical localization of water stress-induced H(2)O(2) production in the leaves of ABA-deficient vp5 mutant and wild-type maize (Zea mays L.) plants were examined, using 3,3-diaminobenzidine and CeCl(3) staining, respectively, and the roles of endogenous ABA in the production of H(2)O(2) induced by water stress were assessed. Water stress induced by polyethylene glycol resulted in the accumulation of H(2)O(2) in mesophyll cells, bundle-sheath cells and vascular bundles of wild-type maize leaves, and the accumulation was substantially blocked in the mutant maize leaves exposed to water stress. Pre-treatments with several apoplastic H(2)O(2) manipulators abolished the majority of H(2)O(2) accumulation induced by water stress in the wild-type leaves. The subcellular localization of H(2)O(2) production was demonstrated in the cell walls, xylem vessels, chloroplasts, mitochondria and peroxisomes in the leaves of wild-type maize plants exposed to water stress, and the accumulation of H(2)O(2) induced by water stress in the cell walls and xylem vessels, but not in the chloroplasts, mitochondria and peroxisomes, was arrested in the leaves of the ABA mutant or the ABA biosynthesis inhibitor (tungstate)-pre-treated maize plants. Pre-treatments with the apoplastic H(2)O(2) manipulators also blocked the apoplastic but not the intracellular H(2)O(2) accumulation induced by water stress in the leaves of wild-type plants. These data indicate that under water stress, the apoplast is the major source of H(2)O(2) production and ABA is a key inducer of apoplastic H(2)O(2) production. These data also suggest that H(2)O(2) generated in the apoplast could not diffuse freely into subcellular compartments.
Abscisic Acid↗
Prostaglandin f2alpha treatment in vivo, but not in vitro, stimulates protein kinase C-activated superoxide production by nonsteroidogenic cells of the rat corpus luteum.
Luteal regression is associated with the generation of reactive oxygen species (ROS). To determine the nature of the ROS generator, cells isolated from luteinized rat ovaries were examined for ROS production using luminol-amplified chemiluminescence (LCL). Cells cultured for 2-48 h exhibited minimal LCL, but there was a significant (30- to 50-fold), rapid (maximum at 3-5 min), and dose-dependent increase in LCL in response to phorbol ester (phorbol 12-myristate 13-acetate; TPA; ED50 = 0.03 microM) and diacylglycerol (1,2-dioctanoyl-glycerol; ED50 = 30 microM). The TPA-induced response was cell number dependent and was virtually abolished by superoxide dismutase, freezing, or heating (95 degrees C for 5 min). Zymosan, known to induce a phagocytic response in leukocytes, stimulated a superoxide (O2-.) response with a slow onset (maximum at 40 to 60 min) and a maximum about one third of that observed for TPA. The response to TPA and zymosan was inhibited by the NADPH/NADH-oxidase inhibitor, diphenylene iodonium (ID50 = 5 microM for TPA), but not by the mitochondrial inhibitors, potassium cyanide, rotenone, or sodium azide. Fractionation of cells by centrifugal elutriation showed that TPA-stimulated O2-. production coeluted with the nonsteroidogenic cells and that little, if any, O2-. generation coeluted with the steroidogenic cells. Cells isolated 1, 2, and 4 h after in vivo treatment with a luteolytic dose of prostaglandin F2alpha (PGF2alpha) showed a significant increase in TPA-stimulated O2-. production at 2 h, whereas luteal cells or corpora lutea incubated directly with 1 microM PGF2alpha did not show any increase in response. Corpora lutea isolated from naturally regressed ovaries (18 days after ovulation) showed a significantly elevated level of TPA-stimulated O2-. production. In conclusion, there is a superoxide generator in luteinized ovaries that is activated through a protein kinase C pathway, localized in nonsteroidogenic cells, transiently increased during PGF2alpha-induced luteolysis in vivo, and elevated during natural luteal regression.
Animals↗
Analysis of reactive oxygen species generating systems in rat epididymal spermatozoa.
Epididymal sperm maturation culminates in the acquisition of functional competence by testicular spermatozoa. The expression of this functional state is dependent upon a redox-regulated, cAMP-mediated signal transduction cascade that controls the tyrosine phosphorylation status of the spermatozoa during capacitation. Analysis of superoxide anion (O2(-.)) generation by rat epididymal spermatozoa has revealed a two-component process involving electron leakage from the sperm mitochondria at complexes I and II and a plasma membrane NAD(P)H oxidoreductase. Following incubation in a glucose-, lactate-, and pyruvate-free medium (-GLP), O2(-.) generation was suppressed by 86% and 96% in caput and cauda spermatozoa, respectively. The addition of lactate, malate, or succinate to spermatozoa incubated in medium -GLP stimulated O2(-.) generation. This increase could be blocked by rotenone and oligomycin (R/O) in the presence of malate or lactate but not succinate. Stimulation with all three substrates, as well as spontaneous O2(-.) production in +GLP medium, was blocked by the flavoprotein inhibitor, diphenylene iodonium. Diphenylene iodonium, but not R/O, suppressed NAD(P)H-induced lucigenin-dependent chemiluminescence. This NAD(P)H-dependent enzyme resided in the sperm plasma membrane and its activity was regulated by zinc and uncharacterized cytosolic factors. Reverse transcription-polymerase chain reaction analysis indicated that the sperm NAD(P)H oxidoreductase complex is quite distinct from the equivalent leukocyte system.
Animals↗
Mitochondrial participation in modulation of calcium transients in DRG neurons.
The effects of the mitochondrial Na+/Ca2+ exchange blocker tetraphenylphosphonium (TPP+) and the permeability transition blocker cyclosporinA (CysA) on the ability of mitochondria to participate in the regulation of intracellular calcium were investigated on freshly isolated mice sensory DRG neurons. The free intracellular calcium level ([Ca2+]in) was measured using indo-1 based microfluorimetry. The characteristics of depolarization-induced [Ca2+]in transients were changed in the presence of 25 microM TPP+. The amplitude of [Ca2+]in transients became decreased and the restoration of resting [Ca2+]in level speeded up in the presence of TPP+. Application of 5 microM cyclosporinA induced substantial residual elevation of [Ca2+]in after termination of depolarization. We conclude that the mitochondrial Na+/Ca2+ exchanger mechanism plays an important role in the regulation of calcium signals during neuronal activity, prolonging them by releasing Ca2+ stored during transient peak. Activation of permeability transition pores does not participate in these processes.
Animals↗
Enhanced superoxide anion formation in vascular tissues from spontaneously hypertensive and desoxycorticosterone acetate-salt hypertensive rats.
OBJECTIVES: To investigate the basal and NADH-stimulated superoxide (.O2-) production and inactivation by Cu/Zn superoxide dismutase (SOD) in aorta from spontaneously hypertensive rats (SHR) and from desoxycorticosterone acetate (DOCA)-salt hypertensive (DOCA-HT) rats. METHODS: Tissue .O2- levels were estimated with the lucigenin-enhanced chemiluminescence method in aorta and cultured smooth muscle cells (SMCs) from SHR and in aorta from DOCA-HT rats treated for 4 weeks. RESULTS: The basal aortic .O2- generation was increased by 135 and 100%, and the NADH stimulated .O2- production was also increased 37 and 22% in SHR and in DOCA-HT rats compared to their normotensive controls, respectively. Although no difference existed in blood pressure as well as in basal and in NADH stimulated .O2- production between Wistar-Kyoto (WKY) rats and SHR rats at age of 6 weeks, O2- production and blood pressure increased concomitantly in SHR aged 9 and 12 weeks. Basal and NADH-stimulated .O2- production, in cultured SMCs, was also 80 and 64% higher, respectively, in SHR compared to WKY rats. The NADH oxidase activity was found to be increased in aorta from both SHR and DOCA-HT rats but SOD activity was reduced only in aorta from DOCA-HT rats. CONCLUSIONS: An enhanced .O2- formation resulting from an increased NADH oxidase activity was found in aorta from SHR and DOCA-HT rats. Cultured arterial SMCs from SHR also generated excessive .O2- formation under basal and stimulated conditions. The age-related increase in vascular .O2- formation in association with the rise in blood pressure in SHR suggests that the oxidative stress might contribute to the development of hypertension. NADH oxidase activity was greater in aorta of both hypertension models, but a decrease of Cu/Zn SOD activity could also contribute to the high level of aortic .O2- in DOCA-HT rats.
Aging↗
Lysophosphatidylcholine is a major contributor to the synergistic effect of mildly oxidized low-density lipoprotein with endothelin-1 on vascular smooth muscle cell proliferation.
Endothelin-1 (ET-1) and oxidized low-density lipoprotein (ox-LDL) are associated with atherosclerosis and essential hypertension. We assessed the effect of mildly oxidized LDL (mox-LDL) and ox-LDL and their major oxidative components, i.e., reactive oxygen species (ROS), lysophosphatidylcholine (LPC), and 4-hydroxy-2-nonenal (HNE) and their interaction with ET-1 on vascular smooth muscle cell (VSMC) proliferation. Growth-arrested VSMCs isolated from the rabbit aorta were incubated with different concentrations of LDL, mox-LDL, ox-LDL, hydrogen peroxide (H(2)O(2)) (a donor of ROS), LPC, or HNE with or without ET-1. DNA synthesis in VSMCs was measured by [(3)H] thymidine incorporation. Mox-LDL, ox-LDL, H(2)O(2), LPC, HNE, or ET-1 stimulated DNA synthesis in a dose-dependent manner. Maximal effect was observed at 5 microg/ml for mox-LDL (162%) or ox-LDL (154%), 15 microM LPC (156%), 5 microM H2O2 (177%), 1 microM HNE (144%), and 0.1 microM ET-1 (195%). By contrast, LDL was without any significant effect. When added together, there was no synergistic effect of LDL, H2O2, or HNE with ET-1 on DNA synthesis. However, the effect of mox-LDL (0.1 microg/ml), ox-LDL (0.5 microg/ml), or LPC (10 microM) was potentiated by ET-1 (114%-338%, 133%-425%, 118%-333%, respectively). The mitogenic effect of mox-LDL, ox-LDL, or LPC and their interaction with ET-1 were inhibited by defatted albumin (10 microg/ml), antioxidant N-acetylcysteine (400 microM), the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (1 microM). The ET(A/B) receptor antagonist TAK044 (1 microM) or the MAPK kinase inhibitor PD098059 (10 microM) inhibited the mitogenic effect of ET-1 and its interaction with mox-LDL, ox-LDL, or LPC. The synergistic interaction of mox-LDL, ox-LDL, or LPC with ET-1 was completely reversed by the combined use of N-acetylcysteine and TAK044. Our results suggest that mox-LDL, ox-LDL, and their major phospholipid component LPC act synergistically with ET-1 in inducing VSMC proliferation by way of the activation of redox-sensitive and MAPK pathways.
Acetylcysteine↗
Ethanol-induced sensitization to endotoxin in Kupffer cells is dependent upon oxidative stress.
BACKGROUND: Activation of Kupffer cells by gut-derived endotoxin plays a pivotal role in alcoholic liver injury. On the other hand, it was reported that acute ethanol administration reduced activation of Kupffer cells. We found that Kupffer cells isolated from rat treated only once with ethanol were sensitized to endotoxin 24 hrs later correlatively with CD14 expression. Moreover, it was shown that Kupffer cell activation by endotoxin via Toll-like receptor (TLR)-4 is involved in alcohol-induced liver injury and ethanol-induced oxidative stress is important in the regulation of transcription factor NFkappaB activation and cytokine production by Kupffer cells. Here, we show that IRAK, one of signaling molecules of TLR-4, regulates tolerance and sensitization to LPS and acute ethanol increases in IRAK expression through a mechanism dependent upon oxidant production. METHODS: Female C57BL/6 mice were given ethanol (5 g/kg) intragastrically, and LPS was injected 1 or 21 hrs later. Serum transaminase levels were measured. Moreover, some mice were treated with NADPH oxidase inhibitor diphenyleneiodonium sulfate (DPI, 1 mg/kg/day) or infected with adenovirus (1 x 10 plaque-forming units, intravenously) containing IkappaB superrepressor gene, which prevent NFkappaB activation of Kupffer cells, for three days. Kupffer cells were isolated from mice 1 hr and 21 hrs after ethanol treatment. After the addition of LPS, TNF-alpha in the media was measured using ELISA, Electrophoretic mobility shift assay (EMSA) was performed to analyze DNA binding activity of NFkappaB. Further, expression of Interleukin-1 receptor-associated kinase (IRAK) was evaluated by Western blotting. RESULTS: LPS-induced increases in transaminases were blunted in mice treated with ethanol before 1 hr. However, ethanol treatment 21 hrs earlier augmented LPS-increased transaminases three-fold over controls. Pretreatment with nonabsorbable antibiotics blocked these effects of ethanol. LPS-induced TNF-alpha production by Kupffer cells isolated from mice 1 hr after ethanol was reduced to about 60% of values from control Kupffer cells, while LPS-induced TNF-alpha production by Kupffer cells isolated from mice treated with ethanol 21 hrs earlier increased 1.5-fold over control Kupffer cells. In Kupffer cells from mice 1 hr after ethanol treatment, expression of IRAK was decreased, and LPS-induced activation of NFkappaB was decreased correlatively. In contrast, ethanol treatment to mice increased expression of IRAK in Kupffer cells 21hrs later and LPS-induced activation of NFkappaB was elevated significantly. On the other hands, DPI treatment for three days prior to ethanol did not prevent decreases in IRAK expression due to ethanol treatment for 1 hr. However, DPI treatment blunted ethanol-induced increases in IRAK expression. Additionally, inhibition of NKkappaB activation with dominant-negative IkappaBalpha blunted ethanol-induced increase in IRAK expression. Contrary, inhibition of NKkappaB did not affect decrease of IRAK expression due to ethanol treatment for 1 hr. CONCLUSIONS: Ethanol causes tolerance in the early phase after ethanol consumption, while sensitization was observed later. Both tolerance and sensitization were induced by gut-derived endotoxin. These findings indicate that ethanol-induced both tolerance and sensitization of Kupffer cells to endotoxin involve IRAK expression. Further, NADPH oxidase plays a pivotal role in the increase in IRAK expression due to ethanol via activation of NFkappaB signaling pathway. In conclusion, these data indicate that acute ethanol causes sensitization to endotoxin through mechanisms dependent upon oxidative stress.
Adenoviridae↗
Angiotensin II increases Pax-2 expression in fetal kidney cells via the AT2 receptor.
Although both the renin angiotensin system (RAS) and the paired homeobox 2 gene (Pax-2) seem critically important in renal organogenesis, whether and how they might interact has not been addressed. The present study asked whether a link between the RAS and Pax-2 exists in fetal renal cells, speculating that such an interaction, if present, might influence renal development. Embryonic kidney explants and embryonic renal cells (mouse late embryonic mesenchymal epithelial cells [MK4] and mouse early embryonic mesenchymal fibroblasts [MK3]) were used. Pax-2 protein and Pax-2 mRNA were detected by immunofluorescence, Western blot, reverse transcription-PCR, and real-time PCR. Angiotensin II (AngII) upregulated Pax-2 protein and Pax-2 mRNA expression via the AngII type 2 (AT(2)) receptor in MK4 but not in MK3 cells. The stimulatory effect of AngII on Pax-2 gene expression could be blocked by PD123319 (AT(2) inhibitor), AG 490 (a specific Janus kinase 2 inhibitor), and genistein (a tyrosine kinase inhibitor) but not by losartan (AT(1) inhibitor), SB203580 (specific p38 mitogen-activated protein kinase inhibitor), PD98059 (specific MEK inhibitor), SP600125 (JNK inhibitor), and diphenyleneiodonium chloride (an NADPH oxidase inhibitor). Moreover, embryonic kidney explants in culture confirmed that AngII upregulates Pax-2 gene expression via the AT(2) receptor. These studies demonstrate that the stimulatory effect of AngII on Pax-2 gene expression is mediated, at least in part, via the Janus kinase 2/signal transducers and activators of transcription signaling transduction pathway, suggesting that RAS and Pax-2 interactions may be important in renal development.
Angiotensin II↗