Ordered array of dendritic cells and CD8+ lymphocytes in portal infiltrates in chronic hepatitis C.

AIMS: Despite the importance of dendritic cells in stimulating primary and secondary immune responses by presenting antigens to T-lymphocytes in draining lymph nodes and peripheral tissues, respectively, very limited information is available on the presence and localization of these cells in hepatitis C virus (HCV)-related chronic active hepatitis. Therefore, we addressed the ultrastructure, immunophenotype, distribution and relationships to lymphatics of dendritic cells in portal infiltrates of this disease. METHODS AND RESULTS: Part of percutaneous diagnostic liver biopsies (Knodell's histological assessment index: 9-13) was processed for electron microscopy and for immunohistochemical detection of immune system cell membrane antigens and of the lymphatic endothelium marker podoplanin. In portal infiltrates, cells with electron microscopical and cell marker features of dendritic cells and expressing the activation markers CD54, CD80, CD83 and CD86 were organized in a discontinuous network, that embedded CD8+ lymphocytes in close contact with dendritic cells and came in contact with hepatocytes, sometimes infiltrating beyond the limiting plate. Also, dendritic cells were found within newly formed lymphatic capillaries in thin, infiltrated septa among hepatocytes. CONCLUSIONS: This evidence strongly suggests a critical role of dendritic cells and newly formed lymphatics in the pathogenesis and organization of the immune infiltrate that characterizes HCV-related chronic active hepatitis.

Nitrovasodilators inhibit platelet-derived growth factor-induced proliferation and migration of activated human hepatic stellate cells.

BACKGROUND & AIMS: Nitrovasodilators have been proposed for the treatment of portal hypertension alone or in combination with beta-blockers. In addition to their vasodilatory properties, nitric oxide (NO) donors may exert direct antifibrogenic properties. We evaluated the effect of nitroglycerin (NTG) and S-nitroso-N-acetyl penicillamine (SNAP) on the mitogenic and chemotactic properties of platelet-derived growth factor (PDGF)-BB and the modulation of the relative intracellular signaling pathways in fully activated human hepatic stellate cells (HSCs), a cell type that plays an active role in liver fibrogenesis and portal hypertension. METHODS & RESULTS: Both NTG and SNAP induced a dose-dependent decrease in PDGF-induced DNA synthesis and cell migration, which was associated with a decrease in PDGF-induced intracellular Ca(2+) increase and extracellular signal-regulated kinase (ERK) activity. These effects were not related to activation of the classic soluble guanylate cyclase (sGC)/guanosine 3',5'-cyclic monophosphate pathway; accordingly, Western blot analysis of HSC lysates revealed the absence of the alpha(1)beta(1) ubiquitous subunits of sGC, whereas they were detectable in quiescent HSCs, freshly isolated from normal human liver. Conversely, both NTG and SNAP induced a more than 10-20-fold increase in prostaglandin E(2) in cell supernatants within 1 minute, associated with an increase in intracellular adenosine 3',5'-cyclic monophosphate levels. Accordingly, the inhibitory effects of NO donors on PDGF action and signaling were eliminated after preincubation with ibuprofen. CONCLUSIONS: These results suggest that NO donors may exert a direct antifibrogenic action by inhibiting proliferation, motility, and contractility of HSCs in addition to a reduction of fibrillar extracellular matrix accumulation.