Background: AMPK-driven signaling plays a dual function as energy sensor and a controller of cellular structure in response to different stimuli, including stress conditions, hormones and antidiabetic drugs. Recent evidence shows that AMPK may control the dynamics of actin stress fibers in astrocytes. Trans-differentiation of hepatic stellate cells (HSC) into contractile myofibroblasts is a key event during the fibrogenic process, and is associated with cytoskeletal modifications. AMPK activity is decreased during the trans-differentiation process of HSC in vivo, and AMPK negatively modulates the activated state of myofibroblastic HSC. However, little information is available on the possible role of the AMPK pathway on the cytoskeleton. Aim: Of the study was to investigate the link between AMPK activation and cytoskeletal remodeling in primary HSC. Methods: HSC were isolated from normal rat liver and cultured in complete medium for up to 16 days. Gene expression was analyzed by RTQ-PCR. Multi stack confocal analysis was employed to determine changes in cytoskeletal organization. Results: Expression of both catalytic subunits (a1 and a2) of AMPK was higher in freshly isolated HSC than in 3-day cultured cells, as indicated by RTQ-PCR. Freshly-isolated HSC exposed to the AMPK activators 5-aminoimidazole-4carboxamide-1-beta-4-ribofuranoside (AICAR) or metformin showed impaired adhesion and spreading on plastic, confirming that AMPK interferes with cytoskeletal organization in these cells. These effects were associated with decreased expression of a-smooth muscle actin and b-actin in HSC exposed to AICAR. Next, activated HSC were treated with AICAR (1mM), and the relationship between AMPK activation and HSC morphology and cytoskeletal organization was analyzed by confocal microscopy after 8 or 24 hours. Treatment with AICAR increased the frequency of actin-based lamellipodia initiation in a random way, suggesting loss of motile direction. These changes were more evident at longer times of exposure to AICAR. Confocal analysis also showed that AICAR induces changes in the expression levels and organization of both total actin and filamentous actin. Conclusion: This study shows for the first time that organization of the actin cytoskeleton is influenced by AMPK during the activation process of HSC. These results identify an new level of interaction between AMPK and hepatic fibrogenesis.
|Titolo:||THE ACTIN CYTOSKELETON AS A NOVEL TARGET OF AMP-ACTIVATED PROTEIN KINASE (AMPK) IN HEPATIC STELLATE CELLS|
|Anno di registrazione:||2009|
|Autori di Ateneo:|
|Autori:||K. Rombouts; C. Tosti Guerra; A. Caligiuri; C. Bertolani; E. Rovida; F. Vizzutti; G. Laffi; M. Pinzani; F. Marra.|
|Appare nelle tipologie:||1c - Abstract su rivista|
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