Although NFkappaB binding activity is induced during liver regeneration after partial hepatectomy, the physiological consequence of this induction is unknown. We have assessed the role of NFkappaB during liver regeneration by delivering to the liver a superrepressor of NFkappaB activity using an adenoviral vector expressing a mutated form of IkappaBalpha. This adenovirus (Ad5IkappaB) was almost exclusively expressed in the liver and inhibited NFkappaB DNA binding activity and transcriptional activity in cultured cells as well as in the liver in vivo. After partial hepatectomy, infection with Ad5IkappaB, but not a control adenovirus (Ad5LacZ), resulted in the induction of massive apoptosis and hepatocytes as demonstrated by histological staining and TUNEL analysis. In addition, infection with Ad5IkappaB but not Ad5LacZ decreased the mitotic index after partial hepatectomy. These two phenomena, increased apoptosis and failure to progress through the cell cycle, were associated with liver dysfunction in animals infected with the Ad5IkappaB but not Ad5LacZ, as demonstrated by elevated serum bilirubin and ammonia levels. Thus, the induction of NFkappaB during liver regeneration after partial hepatectomy appears to be a required event to prevent apoptosis and to allow for normal cell cycle progression.

RF ablation and PMC thus far have had equivalent therapeutic effects, complication rates, and rates of residual foci of untreated disease. However, RF tumor ablation can be achieved with fewer sessions.

Toxins convert the hepatocellular response to tumor necrosis factor-α (TNF-α) stimulation from proliferation to cell death, suggesting that hepatotoxins somehow sensitize hepatocytes to TNF-α toxicity. Because nuclear factor-κB (NF-κB) activation confers resistance to TNF-α cytotoxicity in nonhepatic cells, the possibility that toxin-induced sensitization to TNF-α killing results from inhibition of NF-κB-dependent gene expression was examined in the RALA rat hepatocyte cell line sensitized to TNF-α cytotoxicity by actinomycin D (ActD). ActD did not affect TNF-α-induced hepatocyte NF-κB activation but decreased NF-κB-dependent gene expression. Expression of an IκB superrepressor rendered RALA hepatocytes sensitive to TNF-α-induced apoptosis in the absence of ActD. Apoptosis was blocked by caspase inhibitors, and TNF-α treatment led to activation of caspase-2, caspase-3, and caspase-8 only when NF-κB activation was blocked. Although apoptosis was blocked by the NF-κB-dependent factor nitric oxide (NO), inhibition of endogenous NO production did not sensitize cells to TNF-α-induced cytotoxicity. Thus NF-κB activation is the critical intracellular signal that determines whether TNF-α stimulates hepatocyte proliferation or apoptosis. Although exogenous NO blocks RALA hepatocyte TNF-α cytotoxicity, endogenous production of NO is not the mechanism by which NF-κB activation inhibits this death pathway.

Our findings show that transient human matrix metalloproteinase-1 overexpression in the liver effectively attenuates established fibrosis and induces hepatocyte proliferation.

Tumor necrosis factor (TNF)alpha, a pivotal cytokine involved in inflammation, is produced primarily by Kupffer cells in the liver. It has been shown that inactivation of Kupffer cells prevents alcohol-induced liver injury; therefore, the purpose of this study was to determine if neutralizing anti-TNF-alpha antibody is also effective. Male Wistar rats were exposed to ethanol (11 to 12 g x kg(-1) x d[-1]) continuously for up to 4 weeks via intragastric feeding using an enteral feeding model. Before ethanol exposure, polyclonal anti-mouse TNF-alpha rabbit serum was injected (2.0 mg/kg intravenously). There were no significant differences in body weight, mean ethanol concentration, or cyclic patterns of ethanol in urine when ethanol- and ethanol plus antibody-treated groups were compared. Expression of TNF-alpha and macrophage inflammatory protein 2 (MIP-2) messenger RNA (mRNA), determined using reverse transcription-polymerase chain reaction, was three- to four-fold higher in livers of ethanol-treated rats than in those of rats fed an ethanol-free, high-fat control diet. In addition, MIP-2 levels were also elevated when detected by Northern blot analysis. Anti-TNF-alpha antibody did not affect expression of mRNA for interleukin (IL) 1alpha, IL-6, transforming growth factor beta1, or TNF-alpha. However, MIP-2 mRNA expression, which is regulated by TNF-alpha, was decreased significantly by anti-TNF-alpha antibody treatment. Serum aspartate transaminase levels were elevated in ethanol-treated rats to 136 +/- 12 IU/L after 4 weeks but only reached 90 +/- 5 IU/L (P < .05) in rats treated with anti-TNF-alpha antibody. The hepatic inflammation and necrosis observed in ethanol-fed rats were attenuated significantly by antibody treatment, and steatosis was not. These results support the hypothesis that TNF-alpha plays an important role in inflammation and necrosis in alcohol-induced liver injury and that treatment with anti-TNF-alpha antibody may be therapeutically useful in this disease.

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Following a fibrogenic stimulus, the hepatic stellate cell (HSC; also called Ito cell, lipocyte, or fat-storing cell) changes from a quiescent to an activated cell, 1,2 which includes increased proliferation, a phenotypic transformation to a myofibroblast-like cell, increased synthesis of extracellular matrix proteins, and contractility. [3][4][5][6] The activated HSC is the predominant source of the increased extracellular matrix proteins, which characterize hepatic fibrosis and cirrhosis. Many of the changes demonstrated in HSC activation during fibrogenesis in vivo are also observed in HSCs grown in culture on plastic. 2,7,8 Furthermore, HSCs have been implicated in hepatic inflammation through their ability to secrete cytokines 9 and chemokines 10-12 and express adhesion molecules. 13 Although many aspects of the molecular regulation of the activation of HSCs are unknown, a role for the transcription factor NF B is evolving. NF B is responsible for the rapid induction of many cytokines and adhesion molecules implicated in the immune and inflammatory responses. 14-16 Classic NF B is a heterodimer of p65 (Rel A) and p50 (NF B-1), but NF B may consist of a variety of homodimers and heterodimers. 17 NF B is retained in an inactive form in the cytoplasm through association with an I B inhibitory protein, such as I B␣. 18 Following cellular stimulation, I B␣ is phosphorylated at serines 32 and 36 by a specific kinase IKK, 19,20 ubiquinated, and undergoes proteolysis in proteasomes, enabling NF B to translocate to the nucleus in which it binds to NF B DNA binding sites and stimulates transcription of many cytokines, chemokines, and adhesion molecules. 21 NF B is induced upon the transformation of quiescent to activated HSCs. 22 Using differential display, we demonstrated the expression of ICAM-1, an NF B-responsive gene, in activated but not in quiescent HSCs. 13 Furthermore, treatment of activated, but not quiescent, HSCs with the cytokines TNF␣ or interleukin (IL)-1 resulted in I B␣ degradation, NF B nuclear translocation, increased NF B DNA binding activity, and induction of NF B-responsive genes (Hellerbrand et al., manuscript submitted October 1997).The signaling pathway leading to the induction of NF Bresponsive genes provides opportunities to specifically block this response. A super-repressor form of I B␣, containing serine-to-alanine mutations at amino acids 32 and 36, inhibits signal-induced phosphorylation and subsequent degradation of I B␣. 23,24 The proteasome complex is required for degradation of I B␣. Proteasome inhibitors, such as ALLN and MG-132, block the induction of NF B activity in cultured cells 25,26 and prevent inflammation in vivo. 27 This study uses two different approaches to block the NF B pathway in activated HSCs, as follows: 1) infection Abbreviations: HSC, hepatic stellate cells; ICAM, intercellular adhesion molecule; IL, interleukin; PBS, phosphate-buffered saline; TNF, tumor necrosis factor.

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