Prevention of rat hepatic fibrosis by the protease inhibitor, camostat mesilate, via reduced generation of active TGF-beta

Synergistic induction of apoptosis by acyclic retinoid and interferon-beta in human hepatocellular carcinoma cells

Acyclic retinoid, a synthetic retinoid analog, as well as interferon alfa (IFN-alpha) and IFN-beta induce apoptosis in hepatocellular carcinoma (HCC) cells and are used clinically in the prevention of HCC. Here, we show that acyclic retinoid acts synergistically with IFNs in suppressing the growth and inducing apoptosis (as characterized by DNA fragmentation and chromatin condensation) in 5 human HCC cell lines (JHH7, HuH7, PLC/PRF/5, HLE, and HLF). This synergism was only observed when cells were pretreated with the acyclic retinoid, whereas natural retinoic acids (all-trans and 9-cis retinoic acid) were ineffective. This promotion may be due to up-regulation of type 1 IFN receptor (IFNR) expression by the retinoid. Accordingly, incubation with antitype 1 IFNR antibody abolished the synergy. Enhanced IFNR expression was accompanied by increased expression and DNA-binding activity of STAT1, an intracellular signal transducing molecule of IFNR, and increased induction of 2', 5'-oligoadenyl-5'-triphosphate synthetase, which is a target gene of STAT1. Acyclic retinoid did not have any effects on the growth of normal human hepatocytes (Hc) probably because of a lack of IFNR and STAT1 up-regulation. In conclusion, these results provide a rationale for combined biochemoprevention of HCC using acyclic retinoid and IFN-beta.

Differential expression of urokinase-type plasminogen activator and plasminogen activator inhibitor-1 in early and late gestational mouse skin and skin wounds

Early gestation fetal mouse skin heals without scars. Plasminogen activator inhibitor-1 (PAI-1) has been associated with postnatal organ fibrosis. We hypothesized that the relative balance between urokinase-type plasminogen activator (uPA) and PAI-1 expression in favor of uPA prevents scarring in early fetal skin wounds, whereas a change in favor of PAI-1 in late gestation results in wound scarring. To evaluate uPA and PAI-1 expression, 1-mm skin wounds were made in E14.5 and E18 mice and harvested 24, 48, or 96 hours postwounding. Aprotinin (2 mg/ml)-coated beads were injected into selected E14.5 wounds. Normal skin and skin wounds were evaluated for uPA, PAI-1, and collagen expression. We showed that in normal skin uPA level is higher in E14.5 than in E18 mice, while PAI-1 is lower in E14.5 than in E18 mice. After wounding, E14.5 wounds show a moderate increase in uPA and a minimal increase in PAI-1. E18 wounds show a transient increase in uPA but a significant, sustained increase in PAI-1. Addition of aprotinin to E14.5 wounds causes an increase in collagen deposition. We conclude that the differential expression of uPA and PAI-1 in the skin of early vs. late gestation mice may contribute to the degree of scar formation seen after cutaneous injury.

Impaired liver regeneration in mice by lipopolysaccharide via TNF-alpha/kallikrein-mediated activation of latent TGF-beta

BACKGROUND & AIMS

Because impaired regeneration after surgical treatment of the liver is influenced by circulating endotoxin, the underlying molecular mechanism was investigated.

METHODS

Lipopolysaccharide (LPS) was injected intraperitoneally into mice, followed 24 hours later by 67% partial hepatectomy. We measured serum tumor necrosis factor (TNF) alpha levels as well as proliferating cell nuclear antigen labeling index, transforming growth factor (TGF) beta expression, and plasma kallikrein (PLK) activities in regenerating livers. We also examined the effect of LPS, TNF-alpha, and PLK on latent TGF-beta activation in homotypic and heterotypic cultures of rat or mouse hepatic stellate cells and Kupffer cells.

RESULTS

Serum TNF-alpha levels increased after LPS (500 ng/g body wt) injection and after partial hepatectomy, accompanying TGF-beta-mediated suppression of hepatic proliferating cell nuclear antigen labeling index. This suppression was mimicked by a combination of preadministration of 50 ng/g body wt LPS and postoperative administration of 5 ng/g body wt TNF-alpha. In vitro, LPS stimulated Kupffer cells to secrete TNF-alpha, which enhanced PLK activity on the hepatic stellate cell surface through increasing PLK binding, thereby inducing proteolytic activation of latent TGF-beta and its autoinduction. Blockade of TGF-beta, TNF-alpha, or PLK activity prevented LPS-induced impaired regeneration in vivo.

CONCLUSIONS

LPS provokes TNF-alpha/PLK-mediated proteolytic activation of latent TGF-beta in hepatic stellate cells, leading to impaired liver regeneration after partial hepatectomy.

Transforming growth factor-beta: a promising target for anti-stenosis therapy

Transforming growth factor-beta (TGF-beta) is the general name for a family of cytokines which have widespread effects on many aspects of growth and development. The TGF-beta isoforms are produced by most cell types and exert a wide range of effects in a context-dependent autocrine, paracrine or endocrine fashion via interactions with distinct receptors on the cell surface. TGF-beta is involved in the wound healing process and, thus plays a significant role in the formation of a restenotic lesion after percutaneous transluminal coronary angioplasty (PTCA) or stenting. Perhaps because of its wide-ranging effects, TGF-beta is usually released from cells in a latent form, and its activation and signaling are complex. Manipulation of the TGF-beta1, TGF-beta2, and TGF-beta3 isoforms by inhibiting their expression, activation, or signaling reduces scarring and fibrosis in animal models. However, to date, few have reached clinical trial. This review summarizes current knowledge on the activation and signaling of TGF-beta, and focuses on the anti-TGF-beta strategies which may lead to clinical applications in the prevention of restenosis following PTCA or stenting.