Premium
Bile salt–phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide as a hepatoprotective agent
Author(s) -
Chamulitrat Walee,
Burhenne Jürgen,
Rehlen Tobias,
Pathil Anita,
Stremmel Wolfgang
Publication year - 2009
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.22955
Subject(s) - ursodeoxycholic acid , cytoprotection , protein kinase b , pi3k/akt/mtor pathway , phospholipid , biology , biochemistry , chemistry , apoptosis , microbiology and biotechnology , membrane
A decrease of hepatocellular phosphatidylcholine (PC) is associated with hepatic injury, e.g., in nonalcoholic steatohepatitis (NASH). Therefore, we evaluated the hepatoprotective effect of a PC‐precursor lipid specifically targeted to the liver. We synthesized the bile acid‐phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA‐LPE), which was designed to target PC to hepatocytes by way of bile‐acid transport systems. We synthesized a fluorescently labeled analogue UDCA‐6‐[(7‐nitro‐2‐1,3‐benzoxadiazol‐4‐yl)amino]hexanoyl PE (UDCA‐NBDPE) for uptake and metabolism studies. Unexpectedly, the majority of UDCA‐NBDPE was still intact and not hydrolyzed efficiently in HepG2 cells. For targeting in vivo , NBD fluorescence from UDCA‐NBDPE‐injected mice was recovered in the liver the most, whereas injection of NBDPE alone resulted in an even distribution in liver, kidneys, and intestine. Cytoprotection by UDCA‐LPE was tested in starvation and tumor necrosis factor alpha (TNF‐α) apoptosis models using HepG2 cells. Only the intact UDCA‐LPE was able to persistently stimulate growth after 36 to 120‐hour starvation, and significantly inhibited TNF‐α‐induced apoptosis. In both models, LPC, LPE, UDCA, or UDCA added with LPE exhibited weak to no cytoprotection. UDCA‐LPE stabilized mitochondrial membranes by lowering mitochondrial membrane potential. Western blot analyses of phosphorylated Akt and glycogen synthase kinase‐3 (GSK‐3)α/β revealed that UDCA‐LPE activated phosphatidyl inositol 3‐kinase (PI3K)/Akt signaling pathways. The PI3K inhibitor LY294002 or Akt small interfering (si)RNA consistently inhibited the proproliferative effects of UDCA‐LPE during starvation. The TNF‐α death‐receptor extrinsic pathway involves caspase 8 activation, which is inhibited by cellular FLICE‐inhibitory protein (cFLIP); thus, cFLIP siRNA was employed in our studies. cFLIP siRNA was able to reverse the cytoprotective effects of UDCA‐LPE during TNF‐α‐induced apoptosis, and UDCA‐LPE concomitantly upregulated protein expression of cFLIP L . Conclusion: UDCA‐LPE, which targeted the liver in vivo , elicited potent biological activities in vitro by stimulating hepatocyte growth and by inhibiting TNF‐α‐induced apoptosis. Thus, UDCA‐LPE may be suitable for evaluation of treatment efficacy in NASH. (H EPATOLOGY 2009.)