A-induced Hepatitis In Mice Research Articles

Sublobular veins as the main site of lymphocyte adhesion/transmigration and adhesion molecule expression in the porto-sinusoidal-hepatic venous system during concanavalin A-induced hepatitis in mice.

Lymphocyte infiltration is a manifest feature of hepatitis. To reveal the main site and mechanism of lymphocyte adhesion/extravasation in the hepatic vasculature during inflammation, we morphometrically and histologically analyzed these events in relation to adhesion molecule expression using a murine model of T-cell mediated hepatitis induced by concanavalin A (Con A). Although lymphocyte adhesion was restricted to the sinusoids in untreated mice, it increased in all the segments of porto-sinusoidal-hepatic venous system 8 hours after Con A injection; the number of adhering lymphocytes per unit vascular circumference was the largest in the sublobular veins, relatively large in the central veins and small hepatic veins, and relatively small in the sinusoids and negligible in the portal veins. At 20 hours, extravascular lymphocytes showed similar distribution to lymphocyte adhesion at 8 hours except in the portal veins, around which they were possibly accumulated by the translocation of extrasinusoidal lymphocytes. E-selectin and vascular cell adhesion molecule-1 (VCAM-1) were transiently expressed at 4 to 6 hours, whereas P-selectin and intercellular adhesion molecule-1 were not changed between 0 and 48 hours. In particular, E-selectin expression coincided with that of lymphocyte adhesion in distribution. Lymphocyte attachment was inhibited by pretreatment with anti-E-selectin monoclonal antibody (MAb) or anti-VCAM-1 MAb, and expression of E-selectin and VCAM-1 was suppressed by pretreatment with anti-tumor necrosis factor-alpha (TNF-alpha) MAb. Electron microscopically, lymphocytes were trapped by endothelial lamellipodia and traversed the endothelium by diapedesis. These results indicate that lymphocyte adhesion/transmigration preferentially takes place in the sublobular veins in association with TNF-alpha-induced endothelial activation, i.e., E-selectin and VCAM-1 expression and lamellipodia formation.

Bimodal role of endogenous interleukin-6 in concanavalin A-induced hepatitis in mice.

Acute concanavalin A (Con A)-induced hepatitis in mice is an animal model for hepatic injury induced by activated T cells. The evolution of hepatic involvement can be followed from hour to hour by measuring serum transaminase levels. We investigated the possible role of endogenous interleukin-6 (IL-6) in this model. We found serum IL-6 levels and splenic IL-6 mRNA during Con A-induced hepatitis to be significantly lower in interferon-gamma (IFN-gamma)-deficient mice, which are resistant against the Con A-induced syndrome, than in wild-type ones, suggesting that systemic IL-6 production favors development of hepatic injury. However, IL-6-deficient mice proved to be more susceptible to the disease than wild-type mice, indicating that endogenous IL-6 plays a predominantly hepatoprotective role. Experiments in which wild-type mice were treated with anti-IL-6 antibodies, before or after Con A challenge, allowed us to reconcile these contrasting observations. The antibody injections resulted in a biphasic alteration of serum IL-6 levels, initial neutralization being followed by rebound increased levels due to accumulation of IL-6 in the form of antigen-antibody complexes. The effect of antibody on disease severity differed depending on the time of injection. Antibody injection at 2.5 h post Con A resulted in delayed disease manifestation, whereas treatment initiated before Con A resulted in accelerated disease. We conclude that endogenous IL-6 plays a bimodal role. IL-6 present before Con A challenge as well as that induced in the very early phase after Con A injection triggers hepatoprotective pathways. Continuation of IL-6 production beyond this early phase, by some other pathway, seems to be harmful to hepatocytes.

Treatment of concanavalin A-induced hepatitis in mice with low molecular weight heparin

Background/Aims: Heparin has been noted to inhibit inflammation independent of its known anti-coagulant activity. In the present study, we examined the ability of heparin and low molecular weight heparin to prevent immune-mediated, concanavalin A-induced liver damage. Methods: Mice were pretreated with either heparin or low molecular weight heparin (Fragmin) prior to their inoculation with concanavalin A (10 mg/kg). Liver enzymes, liver histology, and the serum levels of tumor necrosis factor- a, interleukin-6, and interleukin-10 were examined in the control and treated mice. Results: The histopathologic damage in the liver, and the concanavalin A-induced release of aminotransferases, tumor necrosis factor- a, and interleukin-6 were significantly inhibited in mice pretreated with low molecular weight heparin, whereas the serum levels of the anti-inflammatory cytokine interleukin-10 were increased ( p<0.01). Interestingly, maximal inhibition was obtained with low low molecular weight heparin doses (5 and 1 μg/mouse, p<0.001), while higher doses were less effective. Concanavalin A-induced liver injury was not prevented by pretreatment of the mice with heparan sulphate ( p<0.001), which although it is structurally similar to heparin possesses neither anti-inflammatory nor anti-coagulant properties. Conclusions: This study demonstrates the efficacy of low molecular weight heparin in preventing immunemediated liver damage in mice.

Concanavalin A-induced Hepatitis in Mice is Prevented by Interleukin (IL)-10 and Exacerbated by Endogenous IL-10 Deficiency

One single intra-venous (i.v.) injection of Concanavalin A (Con A) into mice provokes a cell-mediated immunoinflammatory hepatitis. We have presently evaluated the immunopharma-cological effects of exogenous interleukin (IL)-10 and the role of endogenous IL-10 in this model by using exogenous IL-10, anti-IL-10 monoclonal antibody (mAb) and mice with disrupted IL-10 gene (IL-10 KO mice). Whilst exogenous IL-10 administered in a prophylactic (lh prior to Con A) and even “early” therapeutic fashion (30min after Con A) reduced the elevation of transaminase activities in plasma in a dose-dependent manner, observed in control mice, these biochemical markers of liver injury were significantly increased both in IL-10 KO mice as well as in those receiving anti-IL-10 mAb. Interestingly, doses of Con A lower than 20 mg/kg that were only capable of inducing slight serological signs of hepatitis in mice, exerted marked hepatitic effects when administered to either anti-IL-10 mAb-treated mice or to IL-10 KO mice. The disease modulating effects of exogenous IL-10 and either genetical or pharmacologically-induced IL-10 deficiency were associated with profound and opposite modifications of the Con A-induced increase in the circulating levels of IFN-y and TNF-a. Relative to control animals, the blood levels of these cytokines were diminished in IL-10-treated mice and augmented in both IL-10 KO mice and anti-IL-10 mAb-treated mice. These results prove the physiological antiinflammatory role of endogenous IL-10 in Con A induced hepatitis and the beneficial effects of IL-10 treatment to prevent this condition.

Production and role of interleukin-10 in concanavalin A-induced hepatitis in mice.

Experimental T-cell-mediated hepatitis induced by concanavalin A (Con A) involves the production of proinflammatory cytokines. Because interleukin (IL)-10 is a potent anti-inflammatory cytokine derived from macrophages and T cells and is produced within the liver, we investigated the role of IL-10 in modulating the hepatotoxicity and the secretion of cytokines following in vivo injection of Con A. IL-10 is produced early in the serum after Con A challenge. Neutralization of endogenous IL-10 by monoclonal antibodies (mAbs) increases the secretion of tumor necrosis factor alpha (TNF-alpha) (+111%), interferon gamma (IFN-gamma) (+92%), and IL-12 (+730%) 8 hours after Con A injection, and increases the hepatotoxicity, assessed by serum alanine transaminase (ALT) (+174%) measurement and by histology, 24 hours after induction of hepatitis. Conversely, preadministration of recombinant IL-10 reduces the production of these proinflammatory cytokines (-47%, -80%, and -47% for TNF-alpha, IL-12, and IFN-gamma, respectively), and decreases neutrophil infiltration and ALT serum concentration (-74%) 8 hours after Con A challenge. We conclude that IL-10, either endogenously produced or exogenously added, has a hepatoprotective role in Con A-induced hepatitis, through its suppressive property on proinflammatory cytokine production, and that it might be of therapeutic relevance in human liver diseases involving activated T cells.

Involvement of processing defects in failure of FP/Al–Li: Drury, W. J.Metall. Trans. A Oct. 1989 20A, (10), 2175–2179

A previous study demonstrated that Fumigaclavine C (FC) had a potential immunosuppressive activity against concanavalin A-induced hepatitis in mice. However, the precise mechanisms of the anti-inflammatory and hepatoprotective effects of FC are incompletely delineated. This study further investigated the protective effects of FC on lipopolysaccharide (LPS)-induced murine RAW264.7 cells and the underlying molecular mechanism in liver kupffer cells. FC differentially attenuated the production of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interferon gamma (IFN-γ), and high mobility group box protein 1 (HMGB-1). Intriguingly, FC significantly suppressed LPS-induced HMGB-1 nucleo-cytoplasmic shuttling relocation and release. FC notably decreased the phosphorylation levels of phosphatidylinositol 3-kinase (PI3K), phosphoinositide-dependent kinase 1 (PDK1), protein kinase C beta II (PKCβII), and protein kinase C gamma (PKCγ). PKCβII/γ played an important part in this signaling pathway cascade. Furthermore, the docking simulation revealed that FC could directly bind to the HMGB-1 B box interfering with Lys90 and Leu145. All of these results indicated that FC exhibited anti-inflammatory and hepatoprotective effects through suppressing HMGB-1 relocation and release by interfering with Lys90 and Leu145.