Fibronectin Increases Survival of Rat Hepatic Stellate Cells - A Novel Profibrogenic Mechanism of Fibronectin

Abstract

The aims of this study were to determine whether fibronectin increases survival of hepatic stellate cells (HSCs) in starving conditions, and to identify the signal transduction pathways involved in this effect. Methods: Primary culture of rat HSCs were plated on fibronectin-uncoated or coated culture wells, and grown in the presence of 0.2% or 20% fetal calf serum. Cell apoptosis was measured by an ELISA procedure. Signal transduction pathways were analyzed by inhibiting major intracellular transduction pathways with appropriated inhibitors and by detecting phosphorylated proteins. Results: Fibronectin increased survival of serum deprived HSCs. This effect was abrogated by the presence of the RGD peptide, by silencing FAK expression, and by inhibiting PI3K with LY294002 or wortmannin. Growth of HSCs on fibronectin induced integrin α5β1 expression, tyr³⁹⁷, ser⁴⁷³, and ser¹³⁶ phosphorylation of FAK, Akt, and Bad, respectively, and the binding of phosphorylated Bad to 14-3-3 proteins. Likewise, fibronectin increased Bcl2/Bax ratio and reduced release of mitochondrial cytochrome c into the cytoplasm, formation of apoptosome, and caspase 9 and 3 activity. These effects were avoided by treatment of cells with PI3K inhibitors. Conclusion: Fibronectin increases survival of HSCs via a pathway involving integrin α5β1 receptors, FAK, PI3K, Akt and proteins of Bcl2 family.

Anatomy, pathophysiology and basic mechanisms of disease

“…Stellate cells themselves, and potentially hepatocytes, may also produce fibronectin EDA, but usually later than the 'first responder' sinusoidal endothelial cells. 592,593 Modulation by soluble mediators…”

Stimulation through very late antigen‐4 and ‐5 improves the multifunctionality and memory formation of CD8+ T cells

“…Inhibition of apoptosis by fibronectin binding has been reported in several cell types [23][24][25]. Here, the acquisition of T-cell effector functionality could be attributed to binding to CH-296, which contains the CS1 and C domains.…”

“…Fibronectin acts in conjunction with TCR engagement to induce T-cell proliferation, which is mediated by the interaction of VLA-4 and VLA-5 with the CS1 and C domains of fibronectin [7][8][9]. Inhibition of apoptosis by fibronectin binding has been reported in several cell types [23][24][25]. Here, the acquisition of T-cell effector functionality could be attributed to binding to CH-296, which contains the CS1 and C domains.…”

Pharmacologically active microcarriers influence VEGF‐A effects on mesenchymal stem cell survival

“…Although PKCε may induce Bcl-2 biosynthesis, the most important action of this kinase is to stimulate proliferation. The increased amount of Bcl-2 due to FN-PAM-VEGF could also be attributed to the presence of fibronectin which is known to promote cell survival via multiple effects, including Bcl-2 over-expression [42]. …”