Eduardo Linck Machado Guimarães

Relationship between oxidative stress levels and activation state on a hepatic stellate cell line

Abstract: Background/Aims: Oxidative stress plays an important role in liver fibrosis. Under pathological conditions, hepatic stellate cells (HSC) undergo an activation process, developing a myofibroblast‐like phenotype from the lipocyte phenotype. In this study, we determined the levels of oxidative stress and proliferation in different activation states of an experimental model of mouse HSC, the GRX cell line. These cells can be induced in vitro to display a more activated state or a quiescent phenotype.

Hepatic stellate cell line modulates lipogenic transcription factors

Background/Aims: Pre‐adipocyte differentiation into adipocyte is a terminal differentiation process triggered by a cascade of transcription factors. Conversely, hepatic stellate cells (HSC) can switch between lipid storing and the myofibroblast phenotype in association with liver fibrotic processes. Here, adipogenic/lipogenic‐related transcription factors and downstream‐regulated genes were evaluated in a murine HSC cell line. GRX‐HSC cells are transitional myofibroblasts that differentiate into lipocytes following retinol or indomethacin treatment.

Hepatic stellate cell activation in vitro: Cell cycle arrest at G2/M and modification of cell motility

Hepatic fibrosis is a common response to chronic liver injury and is characterized by increased production of extracellular matrix components, whose major part is produced by hepatic stellate cells activated by inflammatory mediators to proliferate and migrate into the injured regions. GRX cells are a model of hepatic stellate cells characterized as myofibroblasts by morphological and biochemical criteria. We have recently shown that they respond to inflammatory mediators and cytokines present in the concanavalin A‐activated spleen cell supernatant (SCS) by quantitative changes in the expression of intermediate filaments. The present study investigated the effects of SCS and TNF‐α on the GRX cell proliferation and on the organization of the actin cytoskeleton. SCS and TNF‐α diminished the culture cell density, with an increase of cell [3H]thymidine incorporation and of cellular protein content, indicating an arrest in the G2/M phase of the cell cycle, which was reversible 48 h after removal of SCS. This effect was abrogated by dibutiryl‐cAMP. Actin cytoskeleton reorganization was observed after 24 h treatment, indicating increased cell motility. Our results suggest that inflammation‐dependent activation of stellate cells occurs in ordered interaction and coordination of proinflammatory agents. The increase of cAMP levels activates the conversion of lipocytes into myofibroblasts and increases the number of cells that can participate in repair. Since cAMP retains cells in the G1 phase, cytokines of the TNF‐α group are required for cell proliferation inducing the entry into the S phase. The progression through the G2/M checkpoint is mediated again by increased cAMP levels. J. Cell. Biochem. 90: 387–396, 2003.