Activation of focal adhesion kinase and JNK contributes to the extracellular matrix and cAMP-GEF mediated survival from bile acid induced apoptosis in rat hepatocytes.
OBJECTIVE
Adherence to an extracellular matrix (ECM) rescues hepatocytes from apoptosis, but how hepatocytes adhered to different ECM and respond to apoptotic and cytoprotective stimuli is unknown.


METHODS
Rat hepatocytes were plated on type 1 collagen (CI), laminin (LM) or polylysine (PL) and the amount of apoptosis induced by glycochenodeoxycholate (GCDC), deoxycholate (DCA), Fas ligand or serum withdrawal was determined by Hoechst staining. The response to cytoprotection by cAMP-guanine exchange factor (cAMP-GEF) activation was determined. Kinase activation was determined by immunoblotting with phosphospecific antibodies.


RESULTS
Hepatocytes on LM and PL had more apoptosis in response to all apoptotic stimuli. GCDC increased c-jun-N-terminal kinase (JNK) phosphorylation 2-fold in hepatocytes on CI, but 15- and 30-fold in hepatocytes on PL or LM. SP-600125, a JNK inhibitor, prevented LM and PL potentiation of bile acid apoptosis. GCDC induced dephosphorylation of focal adhesion kinase (FAK) was prevented by cAMP-GEF activation. Cytochalasin B which decreased FAK phosphorylation prevented cAMP-GEF cytoprotection.


CONCLUSIONS
JNK activation augments apoptosis in hepatocytes plated on PL and LM. Decreased FAK phosphorylation as seen in cells treated with bile acids or attached to PL and LM promotes hepatocyte apoptosis.
Department of Clinical Sciences, Tufts Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01539, USA.
Paul
P
Usechak
Anna
A
Gates
Cynthia Rl
CR
Webster
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001647:Bile Acids and Salts / Q000633:toxicity; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D024042:Collagen Type I; D000242:Cyclic AMP / Q000378:metabolism*; D005109:Extracellular Matrix / Q000201:enzymology; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology* / Q000201:enzymology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D007797:Laminin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011107:Polylysine; D051381:Rats
D001647:Bile Acids and Salts; D024042:Collagen Type I; D020662:Guanine Nucleotide Exchange Factors; D007797:Laminin; D011107:Polylysine; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D048031:JNK Mitogen-Activated Protein Kinases