A novel role for ursodeoxycholic acid in inhibiting apoptosis by modulating mitochondrial membrane perturbation.
The hydrophilic bile salt ursodeoxycholic acid (UDCA) protects against the membrane-damaging effects associated with hydrophobic bile acids. This study was undertaken to (a) determine if UDCA inhibits apoptosis from deoxycholic acid (DCA), as well as from ethanol, TGF-beta1, Fas ligand, and okadaic acid; and to (b) determine whether mitochondrial membrane perturbation is modulated by UDCA. DCA induced significant hepatocyte apoptosis in vivo and in isolated hepatocytes determined by terminal transferase-mediated dUTP-digoxigenin nick end-labeling assay and nuclear staining, respectively (P < 0.001). Apoptosis in isolated rat hepatocytes increased 12-fold after incubation with 0.5% ethanol (P < 0.001). HuH-7 cells exhibited increased apoptosis with 1 nM TGF-beta1 (P < 0. 001) or DCA at >/= 100 microM (P < 0.001), as did Hep G2 cells after incubation with anti-Fas antibody (P < 0.001). Finally, incubation with okadaic acid induced significant apoptosis in HuH-7, Saos-2, Cos-7, and HeLa cells. Coadministration of UDCA with each of the apoptosis-inducing agents was associated with a 50-100% inhibition of apoptotic changes (P < 0.001) in all the cell types. Also, UDCA reduced the mitochondrial membrane permeability transition (MPT) in isolated mitochondria associated with both DCA and phenylarsine oxide by > 40 and 50%, respectively (P < 0.001). FACS(R) analysis revealed that the apoptosis-inducing agents decreased the mitochondrial transmembrane potential and increased reactive oxygen species production (P < 0.05). Coadministration of UDCA was associated with significant prevention of mitochondrial membrane alterations in all cell types. The results suggest that UDCA plays a central role in modulating the apoptotic threshold in both hepatocytes and nonliver cells, and inhibition of MPT is at least one pathway by which UDCA protects against apoptosis.
Rodrigues
C M
CM
Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
Fan
G
G
Ma
X
X
Kren
B T
BT
Steer
C J
CJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects; D002756:Cholagogues and Choleretics / Q000494:pharmacology*; D003840:Deoxycholic Acid / Q000633:toxicity; D000431:Ethanol / Q000633:toxicity; D053222:Fas Ligand Protein; D008099:Liver / Q000187:drug effects / Q000473:pathology* / Q000648:ultrastructure; D008297:Male; D008562:Membrane Glycoproteins / Q000633:toxicity; D008930:Mitochondria, Liver / Q000187:drug effects / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016212:Transforming Growth Factor beta / Q000633:toxicity; D014580:Ursodeoxycholic Acid / Q000494:pharmacology*
D002756:Cholagogues and Choleretics; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D008562:Membrane Glycoproteins; D016212:Transforming Growth Factor beta; D003840:Deoxycholic Acid; D000431:Ethanol; D014580:Ursodeoxycholic Acid