Finally, the anti apoptotic effects of IGF I were further evaluated on other effector mechanisms, that is, the cleav age of PARP and caspase 3. As shown in Figure 6, exposure of human HSCs to FasL CHX induces cleavage of PARP and this effect is partially reversed by co incubation with IGF I. In addition, the cleavage http://www.selleckchem.com/products/nutlin-3a.html of caspase 3 induced by phoresissodium dodecylanalysedsulphate polyacrylamide were 473 Akt FasL CHX was decreased by co incubation with IGF I. Discussion The reversibility of fibrosis and even cirrhosis is currently a central issue in hepatology. The introduction of more effective anti viral treatments and possibly anti fibrogenic agents is directed at reducing fibrosis as a key end point. In this context, a clear definition of the cellular and molecular mechanisms regulating apoptosis of fibrogenic cell types, including HSCs, is urgently required.

In addi tion, affinities and differences between experimental models and human disease need to be better defined and clarified. It is evident that in experimentally induced liver fibrosis in rodents, cessation of liver injury results in fibro sis regression, usually associated with reduction of TIMP 1 expression and HSC apoptosis. These observations are supported by in vitro studies performed in activated rodent HSCs. Based on this evidence, clearance of activated HSCs by apoptosis has been regarded as an appealing target for anti fibrotic therapy. However, the regulation of apoptosis in activated human HSCs deserves further evaluation. Novo et al.

have demon strated that activated human HSCs do not undergo spon taneous apoptosis and survive when exposed to prolonged serum deprivation and numerous other pro apoptotic stimuli. Induction of caspase dependent, mitochondria driven apoptosis in human HSCs was observed only when actinomycin D or cycloheximide Carfilzomib were added to the culture, indicating that de novo protein expression contributes to resistance to apoptotic stimuli. In particular, these authors observed an increasingly higher expression of BCl 2 during the process of HSC acti vation. The possibility that human HSCs respond to pro apoptotic stimuli differently from rodent cells has raised the need for a more extensive characterisation of the responsible mechanisms and pathways involved in this process. Accordingly, the aim of the present study was to investigate the involvement of other key anti apoptotic pathways such as PI 3K/Akt/p Bad in response to IGF I.

The choice of IGF I as a stimulus not for these investigations was based on extensive evidence of this polypeptide as a potent survival factor. It has been shown in numerous cell types that IGF I acts through the activation of PI 3K and several downstream molecules. In addition, other path ways are likely to be implicated in the cell survival action of IGF I, particularly ERK kinase activation, Raf activation and p38 activation.