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

Abstract

Background & Aims:Nitrovasodilators have been proposed for the treatment of portal hypertension alone or in combination with ␤-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 dosedependent 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 ␣ 1 ␤ 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.

NCX-1000, a NO-releasing derivative of ursodeoxycholic acid, selectively delivers NO to the liver and protects against development of portal hypertension

“…Indeed NCX-1000 reduces HSC contraction as well as MCP-1 release induced by TNF-␣ and IFN-␥ (30). The finding that SNAP also inhibits HSC contraction (31) and that both compounds increase nitrite͞ nitrate release in cell supernatants as well as intracellular fluorescence in cells loaded with the NO-reactive fluorochrome 4,5-diaminofluorescein diacetate, whereas UDCA itself has no effect, strongly supports the view that NCX-1000 inhibits HSC functions through an NO-dependent mechanism (25).…”

“…In endothelial cells eNOS catalytic activity is modulated by dynamic regulatory processes including posttranslational protein modifications, interactions with regulatory proteins, and availability of essential cofactors (13). It is well established that the binding of eNOS with the ubiquitous calcium-regulatory protein calmodulin promotes NO production, whereas caveolin-1, the coat protein of nonclathrin-coated transport vesicles and putative signaling molecule, decreases the catalytic activity of the enzyme (31). Liver expression of calveolin-1 is increased in cirrhotic rats, suggesting that an abnormal protein-protein interaction is responsible for the defective eNOS function (13).…”

Hepatocyte transplantation activates hepatic stellate cells with beneficial modulation of cell engraftment in the rat

“…Consistent with this finding, nitric oxide donors reproduced the effects of hypoxia in stellate cell lines, for example, with increased VEGF production, 31 while inhibiting proliferation and procollagen expression in cultured HSC. 32,33 Because the latter studies were carried out in fully activated cell lines, comparing all mechanisms of NTG in vitro with its effects in vivo may not be possible.…”

Role of CD44 in Epithelial Wound Repair

“…Several aspects of stellate cell migration have been examined, including chemotactic factors (3-7) and intracellular signaling pathways (6,8,9). However, little is known concerning the cell-matrix interactions mediating migration.…”