Background and aims-We (Gut 2001;48:103-109)

No abstract

Aims:The characteristic histological feature of autoimmune hepatitis (AIH) is interface hepatitis with predominant portal lymphoplasmacytic necroinflammatory infiltration. Centrilobular necrosis (CN), reminiscent of toxic or circulatory liver injury, has been reported in AIH. The aim of this study was to assess the frequency of CN in patients with AIH and its correlation with laboratory and clinical data. Methods: Liver biopsies were obtained from 114 patients (90 women, 24 men, mean (SD) age 45.4 (19.4) years) with AIH and were evaluated under code by a single pathologist according to the modified Knodell score. Results: CN was found in 20 (17.5%) patients with virtually unaffected portal areas in four cases. Patients with AIH with CN had a higher total hepatic activity index (median (range) 11 (6 to 15) v 5 (2 to 10)) and presented less frequently with cirrhosis (10% v 38%). Patients with CN had a higher frequency of acute onset (87% v 32%), higher bilirubin (median (range) 12.0 (0.43 to 40.0) v 1.9 (0.36 to 46)) and higher ALT levels (median (range) 25.6 (2.7 to 63.9) v 7.2 (0.7 to 62.6)), than did patients with AIH without centrizonal injury. Conclusion: CN with sparing of the portal areas represents a rare histological pattern in AIH. CN is associated with an acute clinical presentation and might reflect an early lesion preceding portal involvement. Recognition of this particular histological appearance enables early diagnosis of AIH and a timely initiation of immunosuppressive therapy.A utoimmune hepatitis (AIH) is characterised by the presence of autoantibodies, hypergammaglobulinaemia, elevated serum transaminases, and the histological evidence of interface hepatitis with a predominantly portal lymphoplasmacytic necroinflammatory infiltrate.

Most chronic liver diseases of all etiologies result in progressive liver fibrosis. Myofibroblasts produce the extracellular matrix, including type I collagen, which constitutes the fibrous scar in liver fibrosis. Normal liver has little type I collagen and no detectable myofibroblasts, but myofibroblasts appear early in experimental and clinical liver injury. The origin of the myofibroblast in liver fibrosis is still unresolved. The possibilities include activation of endogenous mesenchymal cells including fibroblasts and hepatic stellate cells, recruitment from the bone marrow, and transformation of epithelial or endothelial cells to myofibroblasts. In fact, the origin of myofibroblasts may be different for different types of chronic liver diseases, such as cholestatic liver disease or hepatotoxic liver disease. This review will examine our current understanding of the liver myofibroblast.

Although leptin induces fibrotic activity in hepatic stellate cells (HSCs), the mechanisms are not entirely understood. To investigate the potential role of reduced nicotinamide adenine dinucleotide phosphate oxidase (NADPH) and reactive oxygen species (ROS) in leptin signaling in HSCs, we analyzed leptin-induced intracellular signaling pathways in primary wild-type (WT), p47 phox ؊/؊ , and signal transducer and activator of transcription protein 3 (STAT3)-deleted HSCs. Leptin-stimulated ROS production was attenuated in human and mouse HSCs by the NADPH oxidase inhibitor diphenylene-iodonium (DPI) and in HSCs lacking the NADPH component p47 phox . Leptin-induced phosphorylation of extracellular signal-regulated kinase (ERK) and AKT, but not of STAT3, was blocked by NADPH oxidase inhibition. Moreover, leptin-induced ROS production was inhibited by the Janus kinase (JAK) inhibitor, AG490, but normal ROS production was observed in STAT3-deleted HSCs. Pharmacologic or genetic inhibition of NADPH in HSCs not only resulted in a reduction of leptin-mediated HSC proliferation but also reduced the leptin-mediated up-regulation of the fibrogenic markers collagen ␣1(I) and ␣-smooth muscle actin and of the inflammatory mediators monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein 1 (MIP-1), and macrophage inflammatory protein 2 (MIP-2). In vivo, leptin enhanced chemokine expression induced by chemokine (C-C motif) ligand 4 (CCl 4 ) in WT mice, but a blunted response was observed in p47 phox؊/؊ mice. In conclusion, NADPH oxidase is a crucial mediator of proliferative, fibrogenic, and inflammatory actions of leptin. Leptin-induced NADPH oxidase acts downstream of JAK activation but is independent of STAT3. Our results, in conjunction with previous studies on angiotensin II and platelet-derived growth factor (PDGF), place NADPH in the center of the fibrogenic signaling response in HSCs and demonstrate its potential role as a pharmacological target for antifibrotic therapies.