Ethanol-induced macrophage apoptosis: the role of TGF-beta.
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Both clinical and laboratory reports indicate that ethanol addicts are prone to recurrent infections. We hypothesize that ethanol promotes macrophage apoptosis, thus compromising the efficiency of the mononuclear phagocyte system in dealing with infection. We studied the effect of ethanol on macrophage apoptosis. Human monocytes isolated from healthy subjects after an alcohol drinking binge showed enhanced apoptosis (before, 1.2 +/- 0.3% vs after, 28.4 +/- 3.7% apoptotic cells/field). Peritoneal macrophages harvested from ethanol-treated rats also showed increased (p < 0.0001) apoptosis. DNA isolated from peritoneal macrophages of ethanol-treated rats displayed integer multiples of 200 base pairs (ladder pattern). Furthermore, macrophages harvested from ethanol-treated rats had an enhanced expression as well as accumulation of TGF-beta. In in vitro studies, ethanol promoted apoptosis of human monocytes as well as rat peritoneal macrophages. In addition, ethanol enhanced apoptosis of murine macrophages (J774) in a time-dependent manner. The ethanol-induced apoptosis was amplified by LPS and partly attenuated (p < 0.001) by anti-TGF-beta Ab. TGF-beta also promoted macrophage apoptosis in a dose-dependent manner. Moreover, ethanol enhanced TGF-beta protein production by macrophages. These results indicate that ethanol promotes macrophage apoptosis. This effect of ethanol seems to be partly mediated through the generation of TGF-beta by macrophages. (+info)
Effects of dexamethasone, ibuprofen, and ligustrazini on lipopolysaccharides-induced tumor necrosis factor alpha production.
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AIM: To study the influence of dexamethasone (Dex), ibuprofen (Ibu), and ligustrazini (Lig) on lipopolysaccharides (LPS)-induced tumor necrosis factor alpha (TNF alpha) gene expression (both mRNA and protein). METHODS: TNF alpha in supernatants of human whole blood was measured by ELISA; The TNF alpha mRNA was assessed by slot blot analysis. RESULTS: LPS-induced TNF alpha production was in a dose-dependent manner. TNF alpha levels in the whole blood increased markedly at 3 h and peaked at 6 h. The induction of TNF alpha mRNA was very rapid, peaking at 2 h after LPS challenge. Dex exerted inhibitory effects on TNF alpha production in a dose-dependent manner. Ibu and Lig had 2-phase effects on TNF alpha release. CONCLUSION: Dex, Ibu, and Lig affected TNF alpha gene expression, so they may be new approaches of anti-TNF alpha for treatment of sepsis. (+info)
Effects of Ro 31-8220 on lipopolysaccharides-induced hepatotoxicity and release of tumor necrosis factor from rat Kupffer cells.
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AIM: To investigate protein kinase C (PKC) functions on lipopolysaccharide (LPS)-induced hepatotoxicity, a new potent PKC inhibitor Ro 31-8220 (Ro) was used to detect its effect on LPS-induced hepatotoxicity in rat hepatocytes and tumor necrosis factor (TNF) release from rat Kupffer cells (KC). METHODS: Hepatocytes (containing KC) were incubated with LPS (10 mg.L-1) and Ro (0.1-10 mumol.L-1) for 24 h, alanine aminotransferase (AlaA) leakage in the culture as indication of hepatotoxicity. The TNF activity in the supernatant of rat KC culture with LPS in the presence of Ro (0.1-10 mumol.L-1) was monitored by the L929 target cell lytic assay. RESULTS: Ro (0.1-10 mumol.L-1) reduced AlaA leakage in the hepatocyte culture. Ro inhibited dose-dependently the LPS-induced TNF production from rat KC. CONCLUSION: PKC inhibitor Ro protects the hepatocytes from LPS-induced cytotoxicity and inhibits the LPS-induced TNF production from rat KC. (+info)
Effects of dexamethasone and ibuprofen on LPS-induced gene expression of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung.
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AIM: To study the kinetics of tumor necrosis factor alpha (TNF alpha), interleukine-1 (IL-1 beta), and macrophage inflammatory protein-1 alpha (MIP-1 alpha) gene expression in rat lung after i.p. lipopolysaccharides (LPS) and the effect of dexamethasone (Dex) and ibuprofen (Ibu) on the cytokines gene expression. METHODS: The amount of Evans blue in lung was measured by fluorescence method. The mRNA levels of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung were assessed by slot blot analysis. RESULTS: The mRNA levels of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung after i.p. LPS increased in a dose-dependent manner, and peaked at 2, 6, and 12 h, respectively. Both Dex 50 mg.kg-1 and Ibu 90 mg.kg-1 injected at 1 h before i.p. LPS markedly decreased the content of Evans blue in lung at 1 h after i.p. LPS. After Dex or Ibu pretreatment, the peak levels of TNF alpha, IL-1 beta, and MIP-1 alpha mRNA decreased markedly compared with LPS alone. CONCLUSION: The gene expression of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung increased after i.p. LPS. Dex and Ibu prevented LPS-induced lung injury through inhibiting the cytokines gene expression. (+info)
Influences of Kupffer cell stimulation and suppression on immunological liver injury in mice.
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AIM: To study the possible involvement of Kupffer cells (KC) in immunological liver injury in mice. METHODS: Liver injury was induced by i.v. injection of Bacillus Calmette-Guerin (BCG) 5 x 10(7) viable bacilli followed by i.v. injection of lipopolysaccharides (LPS) 7.5 micrograms to each mouse. Indian ink and silica were i.v. injected to suppress KC and retinol was given po to stimulate KC in these mice. Plasma alanine aminotransferase (AlaAT), aspatate aminotransferase (AspAT), nitric oxide (NO), and liver tissue were examined. RESULTS: Injection of LPS following BCG injection resulted in a remarkable elevation of plasma NO, AlaAT, and AspAT levels, and severe liver damage. The damages were enhanced by the activation of KC with retinol and reduced by suppression of KC with silica and Indian ink. CONCLUSION: The degree of liver injury induced by BCG + LPS is closely correlated with the status of KC, and NO from KC plays an important role in the pathogenesis of the liver damage in mice. (+info)
NO contribution to lipopolysaccharide-induced hepatic damage in galactosamine-sensitized mice.
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To investigate the role of nitric oxide (NO) in hepatitis-induced endotoxemia, we injected mice intraperitoneally with 250 mg/kg galactosamine (GalN) and 1 mg/kg lipopolysaccharide (LPS) separately and in combination. NO synthesis increased in a dose-dependent manner with LPS. NO generation at 5 hr after administration of LPS was greater than that at 24 hr. Enhancement of NO generation was demonstrated in mice administered GalN and LPS in combination. A nitrosyl-heme signal in 10,000 g supernatant of liver homogenate, due to cytochrome P450 (P450) combining with NO, NO-P450, was detected at more than ten hr and even more after administration of LPS by electron spin resonance (ESR) measurements at 77 degrees K. The strongest NO-P450 signal and most extreme elevation of aspartate oxoglutarate aminotransferase (AST), alanine oxoglutarate aminotransferase (ALT), and lactate dehydrogenase (LDH) in serum and of lysosomal enzyme activity in plasma were observed in the GalN + LPS group. Their potency was greater than in the 10 mg/kg LPS group, which was even greater than in the LPS 1 mg/kg group. The aniline hydroxylase activity was inversely proportional to NO-P450 signal intensity. It appears that NO might contribute to LPS-induced hepatic damage in GalN-sensitized mice through degeneration and inactivation of liver microsomal enzymes by binding P450 active sites. (+info)
Bacterial lipopolysaccharide inhibits dengue virus infection of primary human monocytes/macrophages by blockade of virus entry via a CD14-dependent mechanism.
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Monocytes/macrophages (MO/Mphi) are the major target cells for both dengue virus (DV) and bacterial lipopolysaccharide (LPS), and the aim of this study was to define their interactions. We had found that LPS markedly suppressed DV infection of primary human MO/Mphi when it was added to cultures prior to or together with, but not after, viral adsorption. The inhibitory effect of LPS was direct and specific and was not mediated by LPS-induced secretion of cytokines and chemokines such as tumor necrosis factor alpha, interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12, alpha interferon, MIP-1alpha, and RANTES. In fact, productive DV infection was not blocked but was just postponed by LPS, with a time lag equal to one viral replication cycle. Time course studies demonstrated that LPS was only effective in suppressing DV infection of MO/Mphi that had not been previously exposed to the virus. At various time points after viral adsorption, the level of unbound viruses that remained free in the culture supernatants of LPS-pretreated cultures was much higher than that of untreated controls. These observations suggest that the LPS-induced suppression of DV replication was at the level of virus attachment and/or entry. Blockade of the major LPS receptor, CD14, with monoclonal antibodies MY4 or MoS39 failed to inhibit DV infection but could totally abrogate the inhibitory effect of LPS. Moreover, human serum could significantly enhance the LPS-induced DV suppression in a CD14-dependent manner, indicating that the "binding" of LPS to CD14 was critical for the induction of virus inhibition. Taken together, our results suggest that LPS blocked DV entry into human MO/Mphi via its receptor CD14 and that a CD14-associated cell surface structure may be essential for the initiation of a DV infection. (+info)
Fever: links with an ancient receptor.
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Recent advances have provided evidence that prostaglandin E2 mediates the generation of fever in response to interleukin-1 or lipopolysaccharide and have reinforced the similarities of signaling downstream of these two pyrogens. (+info)