Toll-like receptor 2 mediates inflammatory cytokine induction but not sensitization for liver injury by Propioni- bacterium acnes

Recognition of Gram-positive bacteria by Toll-like receptor 2 (TLR2) induces activation of proinflammatory pathways. In mice, sensitization with the Gram-positive Propionibacterium acnes followed by a challenge with the TLR4 ligand, lipopolysaccharide (LPS), results in fulminant hepatic failure. Here, we investigated the role of TLR2 in liver sensitization to LPS-induced injury. Stimulation of Chinese hamster ovary cells and peritoneal macrophages with heat-killed P. acnes required expression of TLR2 but not of TLR4, suggesting that P. acnes was a TLR2 ligand. Cell activation by P. acnes was myeloid differentiation primary-response protein 88 (MyD88)-dependent, and it was augmented by coexpression of CD14 in mouse peritoneal macrophages. In vitro, P. acnes behaved as a TLR2 ligand and induced TLR4 hetero- and TLR2 homotolerance in peritoneal macrophages. In vivo priming of wild-type mice with P. acnes, but not with the selective TLR2 ligands peptidoglycan and lipotheicoic acid, resulted in hepatocyte necrosis, hyperelevated serum levels of tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, interferon-gamma (IFN-gamma), and IL-12 (p40/p70), and increased RNA expression of proinflammatory cytokines (IL-12p40, IL-1alpha, IL-6, IL-1beta, IL-18, IFN-gamma) in the liver after a LPS challenge. Furthermore, P. acnes priming sensitized TLR2-deficient (TLR2-/-) but not MyD88-/- mice to LPS-induced injury, evidenced by hepatocyte necrosis, increased levels of serum TNF-alpha, IFN-gamma, IL-6, and liver proinflammatory cytokine mRNA expression. IFN-gamma, a cytokine sensitizing to endotoxin, was induced by P. acnes in splenocytes of TLR2-/- and TLR9-/- but not MyD88-/- mice. These results suggest that although P. acnes triggers TLR2-mediated cell activation, TLR2-independent but MyD88-dependent mechanisms mediate in vivo sensitization by P. acnes for LPS-induced liver injury.     

Acute ethanol consumption synergizes with trauma to increase monocyte tumor necrosis factor α production late postinjury

The hypothesis that acute ethanol uptake plus trauma can synergize to increase immunosuppression was tested. We found that, unlike non-alcohol-exposed patients, patients with acute alcohol use prior to trauma have a transient decrease in monocyte tumor necrosis factor (TNF) production during the very early postinjury (0–3 days) period. However, TNF production by these alcoholexposed patients' monocytes (MØ) became hyperelevated late postinjury (>9 days). Consequently, these massively elevated MØ TNF levels can contribute to posttrauma immunosuppression after acute alcohol use. We also demonstrate that normal monocyte activation with the superantigen,Staphylococcus enterotoxin B (SEB), results in a preferential induction of cellassociated MØ TNF production, described as characteristic of immunosuppressed trauma patients. Acutein vitro ethanol treatment down-regulated the elevated TNF production by trauma patients' MØ after either SEB, muramyl-dipeptide (MDP), interferon- plus MDP, or lipopolysaccharide (LPS) stimulation. Both SEB- and LPS-induced TNF mRNA induction was inhibited by acute alcohol treatment in normal MØ, indicating that ethanol can regulate cytokine gene expression. An additional immunosuppressive effect of acute ethanol's stimulation was suggested by its induction of elevated transforming growth factor production in trauma patients' activated MØ.     

Alcohol-Induced Regulation of Nuclear Regulatory Factor-Kβ in Human Monocytes

Acute ethanol exposure has the capacity to modulate immune functions, particularly, to down regulate monocyte production of inflammatory cytokines. However, the intracellular mechanisms for these effects of ethanol are yet to be understood. Considering that nuclear regulatory factor-kβ (NF-KB)/Rel is a common regulatory element of the promoter region of the inflammatory cytokine genes, herein, we tested the hypothesis that acute ethanol affects NF-kB activation in human monocytes. Adherence-isolated monocytes showed constitutive DNA binding activity of NF-kB. A clinically relevant dose (25 mM) of acute ethanol treatment in vitro increased NF-kB binding activity in monocytes with a preferential induction of the inhibitory, p50/p50, NF-kB/Rel homodimer, and resulted in no induction of the p65/p50 heterodimer. In contrast, lipopolysaccharide stimulation primarily induced the p65/p50 heterodimer that has been shown to result in gene activation. Thus, such unique activation of the inhibitory p50/p50 homodimer by acute ethanol treatment may result in inhibition rather than activation of NF-kB-regulated inflammatory cytokine genes. Consequently, these results suggest that physiologically relevant concentrations of ethanol may affect production of inflammatory cytokines, such as tumor necrosis factor-α, interleukin-1β, and interleukin-6 by disrupting NF-kB signaling in monocytes.     

The genetics of hepatitis C virus underlie its ability to escape humoral immunity

Hepatitis C virus (HCV) is a leading cause of chronic liver disease, and efforts to develop therapeutic vaccine strategies have been limited by immune escape due to HCV variants that are resistant to current vaccines or HCV variants that rapidly acquire new resistance-conferring mutations. Recently, the crystal structure of the viral envelope protein E2 region was resolved as well as how E2 docks to the host CD81 protein; therefore, antibodies that block this interaction should prevent viral entry into host cells. In this issue of the JCI, Bailey and colleagues show that immune escape of HCV can occur by naturally occurring polymorphisms in E2 that are distinct from those at mapped sites of antibody binding. These data reveal alternative mechanisms of resistance that need to be considered in both natural viral escape as well as in rationale vaccine design against HCV.     

Acute effects of zolpidem on daytime alertness, psychomotor and physical performance

In a double-blind cross-over study, seven athletes received zolpidem (10mg) or placebo in two sessions over two nights. Residual effects on subsequent daytime functions were evaluated objectively by measuring psychomotor and physical performance using a combined test of finger dexterity, a simple discriminatory reaction test, critical flicker fusion test (CFF), vertical jump, and 50-m sprint, as well as subjectively, by visual analog scales. Zolpidem shortened self-estimated sleep latency and increased total sleep at nighttime. There was no change in alertness and fatigue scales on the following day in the zolpidem session, but realm of daytime well-being was slightly worsened. The CFF test showed significantly better results in the zolpidem group than in the placebo group. Zolpidem did not have effects in athletic evaluation. Zolpidem has a hypnotic activity without disturbing psychomotor and physical performance on the following day when given to healthy adults, suggesting zolpidem may be used in healthy athletes to adjust their extrinsic sleep disturbances and their consecutive psychomotor and physical impairments.     

天然免疫及微RNAs在肝脏疾病中的作用(附视频)

[编者按:本文系Szabo教授在第1届中国免疫学学术会议上所作"Innate immunity and microRNAin liver disease"报告文字提要] 肝脏作为一个免疫器官,不仅可形成局部的免疫反应,而且对全身的免疫应答也有调节作用.近年来研究表明,天然免疫反应在各种原因引起的肝脏疾病中扮演了重要的角色.     

Additive inhibition of dendritic cell allostimulatory capacity by alcohol and hepatitis C is not restored by DC maturation and involves abnormal IL-10 and IL-2 induction

Background: Excessive alcohol use results in impaired immunity, and it is associated with increased incidence and progression of chronic hepatitis C virus (HCV) infection. Here we investigated the effects of HCV infection and alcohol on myeloid dendritic cells (DC) that are critical in antiviral immunity. Methods: Immature and mature DCs were generated from monocytes of chronic HCV infected patients (HCV‐DC) and controls (N‐DC) with IL‐4 plus granulocyte‐macrophage colony stimulating factor (GM‐CSF) in the presence or absence of alcohol (25 mM). DC allostimulatory capacity was tested in mixed lymphocyte reaction (MLR) and cytokine production by ELISA. Results: Allostimulatory capacity of HCV‐DCs was reduced compared to N‐DCs and it was further inhibited by alcohol treatment (p < 0.01). MLR was also decreased with alcohol‐treated N‐DCs. DC phenotypic markers and apoptosis were comparable between HCV‐DCs and N‐DCs irrespective of alcohol treatment. However, HCV‐DCs and alcohol‐treated N‐DCs exhibited elevated IL‐10 and reduced IL‐12 production. Reduced MLR with HCV‐DCs and its further inhibition by alcohol coexisted with decreasing IL‐2 levels (p < 0.017). DC maturation partially improved but failed to fully restore the reduced allostimulatory function of either alcohol‐treated or alcohol‐naïve HCV‐DCs (p < 0.018). Conclusions: Alcohol and HCV independently and together inhibit DC allostimulatory capacity, increase IL‐10, reduce IL‐12 and IL‐2 production that cannot be normalized by DC maturation. HCV and alcohol interact to modulate innate and adaptive immune responses via dendritic cells.