1,720,996 research outputs found
Testing of Compounds in Models of Pulmonary Emphysema
No full textThere is a pressing need for the development of new therapies for emphysema, particularly as no existing treatment has been shown to reduce disease progression. Compounds with a potential activity against the pathological mechanisms postulated to play a role in the development and progression of emphysema should be tested in vivo in animal models of this disease. The choice of the model is of capital importance. While models of elastase-induced emphysema are relatively easy to execute, require low personnel capacity and provide fast results, they also have a limited clinical relevance. On the other hand, models of chronic smoke exposure are time-consuming, expensive and require high personnel capacity but have a high clinical relevance. Presently, mainly two pharmacological approaches are being considered and investigated in experimental studies. The first approach consists of pharmacological interventions designed to slow down the rate at which alveolar wall is lost in emphysema. In this approach we find anti-inflammatory agents, protease inhibitors and antioxidants. The attempt to reduce lung inflammatory cell infiltration is most appealing since such an effect would also reduce the lung burden of both proteases and oxidants. The second approach is an attempt to reverse the process of alveolar loss by inducing alveolar growth. To our knowledge here only the effects of retinoids and/or retinoid receptor agonists have been investigated. This report presents a selected review of the literature of animal studies using these pharmacological approaches
Signalling pathways involved in isoprostane-mediated fibrogenic effects in rat hepatic stellate cells
No full textDespite evidence supporting a potential role for F2-isoprostanes (F2-IsoPs) in liver fibrosis, their signalling mechanisms are poorly understood. We have previously provided evidence that F2-IsoPs stimulate hepatic stellate cell (HSC) proliferation and collagen hyperproduction by activation of a modified form of isoprostane receptor homologous to the classic thromboxane receptor (TP). In this paper, we examined which signal transduction pathways are set into motion by F2-IsoPs to exert their fibrogenic effects. HSC were isolated from the rat liver, cultured to their activated myofibroblast-like phenotype, and then treated with the isoprostane 15-F2-isoprostane (15-F2t-IsoP). Inositol trisphosphate (IP3) and adenosine 3’,5’-cyclic monophosphate (cAMP) levels were determined by commercial kits. Mitogen-activated protein kinases (MAPK) and cyclin D1 expression were assessed by western blotting. Cell proliferation and collagen synthesis were determined by measuring [3H]-thymidine and [3H]-proline incorporation, respectively. 15-F2t-IsoP elicited an activation of extracellular signal-regulated kinase (ERK), p38 MAPK, and c-Jun HN2-terminal kinase (JNK), that are known to be also regulated by G-protein-coupled receptors. Preincubation with specific ERK (PD98059), p38 (SB203580) or JNK (SP600125) inhibitors prevented 15-F2t-IsoP-induced cell proliferation and collagen synthesis. 15-F2t-IsoP decreased cAMP levels within 30 minutes, suggesting the binding to TP isoform and activation of Gi protein. Also, 15-F2t-IsoP increased IP3 levels within few minutes, suggesting that Gq protein pathway is also involved. In conclusion, the fibrogenic effects of F2-IsoPs in HSC are mediated by downstream activation of MAPK, through TP binding that couples via both Gq and Gi proteins. Targeting TP receptor, or its downstream pathways, may contribute to prevent oxidative damage in liver fibrosis
Effect of free iron on collagen synthesis, cell proliferation and MMP-2 expression in rat hepatic stellate cells
No full textVarious studies on hepatic fibrosis occurring in iron overload suggest that excess of tissue iron may be involved in the stimulation of collagen synthesis. Anyway, up to date, direct evidence on the role of iron in hepatic fibrosis is lacking. Moreover, it is not clear whether iron acts as direct initiator of fibrogenesis or as mediator of hepatocellular necrosis. In the present study, we investigated the effect of nontoxic doses of iron on collagen metabolism and proliferation, key features of liver fibrosis, by means of cultures of hepatic stellate cells, the liver cells responsible for collagen production. Iron treatment increased collagen synthesis without affecting noncollagen proteins. The maximum effect was observed at 5 microM iron (+132%). At this dose, no cell damage or proliferation was detected. Conversely, higher doses of iron (10 and 25 microM) induced cell proliferation and a lower increase in collagen synthesis, suggesting the prevalence of proliferative effect on the synthetic one. These effects occurred without the intervention of serum factors and were not mediated by lipid peroxidation. Our results strongly support the hypothesis that iron "per sé" may act as a profibrogenic agent. Finally, we provide evidence that iron plays a role also in matrix degradation, by stimulating some metalloprotease activities. Iron treatment increased metalloprotease-2 activity in hepatic stellate cells, while no changes were observed for interstitial collagenase activity suggesting that, in these conditions, a pathological accumulation of hepatic extracellular matrix may occur
F2-Isoprostane receptors and signal transduction on hepatic stellate cells
No full textF2-isoprostanes are markers of oxidative stress and mediators of important biological effects. Previously, we provided evidence that F2-isoprostanes, generated during CCl4-induced hepatic fibrosis, mediate hepatic stellate cell (HSC) proliferation and collagen hyperproduction.
We suggested the involvement of a modified form of isoprostane receptor, homologous to the classic TxA2 binding site. The stimulatory effects of 8-epi-PGF2alpha on DNA and collagen synthesis are mediated by TxA2 receptor (TP). Moreover, western blotting and immunocytochemistry analysis revealed the expression of TP on HSC both on plasma membranes and within the cells.
Experiments on the signal transduction pathways showed that 8-epi-PGF2alpha increase Ins(1,4,5)P3 and MAPK. Thus, it is likely that the fibrogenic effects induced by 8-epi-PGF2alpha in HSC are mediated by these transduction pathways
Fibrogenic effects of isoprostanes on hepatic stellate cells are mediated by TP receptor
No full textisoprostanes (IsoPs) proved to be mediators of important biological effects and would act through the activation of receptors analogous to those for thromboxane A2 (TP receptors)
In a previous work, we provided evidence that IsoPs, generated during carbon tetrachloride-induced hepatic fibrosis, mediate cell proliferation and collagen hyperproduction in hepatic stellate cells (HSC). These effects seem to be mediated by a modified form of isoprostane receptor, homologous to the classic TxA2 binding site, as suggested by binding studies.
Moreover, western blotting and immunocytochemistry analysis revealed the expression of TP in HSC both on plasma membranes and within the cells.
Further experiments, carried out to clarify the signal transduction pathways, showed that 8-epi-PGF2induced in HSC an increase of Ins(1,4,5)P3. In addition, the treatment of HSC with IsoPs activated ERK1/2, p38 MAPK and cyclin D1. Since these pathways are involved in cell proliferation and collagen gene expression, it is likely that the fibrogenic effects induced by 8-epi-PGF2 in HSC are mediated by these signalling transduction pathways
Iron overload enhances the development of experimental liver cirrhosis in mice
No full textThe role of iron in initiating liver fibrosis in iron overload diseases is not clearly established. Partly, this is due to the lack of suitable animal models that can produce the full liver pathology seen in genetic hemochromatosis. Recent advances in this field have demonstrated that iron may be interacting with other potential liver-damaging agents. The aim of this study was to investigate if feeding with carbonyl iron (CI) facilitates the development of carbon tetrachloride (CCl4)-induced liver fibrosis in the mouse. Mice were given a diet containing 3% CI and treated with CCl4 intraperitoneally twice weekly and 5% alcohol added to the drinking water for 12 weeks. Hepatic iron content increased 15- and 22-fold in animals receiving CI and CI + CCl4. At histological examination, iron-laden hepatocytes were found in CI treated animals, whereas these were absent in animals not exposed to CI. Mice receiving iron-enriched diet alone showed a mild fibrosis. Conversely, a marked collagen deposition was observed in CCl4 and CI + CCl4 groups. In particular, in this latter group, there was evidence of liver cirrhosis. Biochemical evaluation of collagen content substantiated histologic analysis. These results demonstrate that the addition of iron facilitates the development of cirrhosis in animals exposed to subtoxic doses of CCl4. This model may be useful in exploring the pathogenesis of liver cirrhosis. Moreover, its use in genetically altered mouse strains might provide new insight on the role of iron in fibrosis
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