Growth Stimulation and Anti-apoptotic Properties of a Novel Ursodeoxycholic Lysophosphatidylethanolamide in HepG2 cells: Implications for Treatment of Liver Diseases
Homeostasis of phospholipids is altered during pathogenesis of liver diseases including alcohol and non-alcoholic steatohepatitis (NASH). There is no generally accepted drug therapy to treat these diseases. Hepatic phosphatidylcholine (PC) is often depleted. As a therapy strategy, we synthesized a bile acid-phospholipid conjugate which targets hepatocytes via the bile acid transport system. We performed amide coupling between ursodeoxycholic acid (UDCA) and lysophosphatidylethanolamine (LPE) to form ursodeoxycholic lysophosphatidylethanolamide (UDCA-LPE). For uptake studies and metabolism in HepG2 cells, fluorescent labelled UDCA-NBD PE was synthesized. Structures of UDCA-LPE and UDCA-NBD PE were analyzed by NMR spectroscopy and mass spectrometry. By using thin layer chromatography and liquid chromatography coupled to mass spectrometry, we provided evidence that UDCA-NBD PE was metabolized by HepG2 cells to produce UDCA, NBD PE and NBD PC. UDCA-NBD PE decomposition implies that UDCA-LPE could be decomposed to UDCA, LPE and LPC in cells. It is known that phospholipids support cell growth in culture we thus studied effects of UDCA-LPE on cell growth during starvation. We found that UDCA-LPE stimulated cell growth in the same manner as LPE suggesting that hydrolysis of UDCA-LPE to LPE was responsible for growth stimulation. Since fatty liver diseases are associated with hepatocyte apoptosis, effects of UDCA-LPE on apoptosis were studied. We performed FACS analysis of propinium-iodide stained DNA and Caspase 3/7 and 8 activity assays to study TNF-a+cyclohexaminde-induced apoptosis in HepG2 cells. For both assays, UDCA-LPE inhibited apopotosis by 70%, while LPC had much weaker inhibition by 20%. Taken together, UDCA-LPE elicited biological activities in stimulating hepatocyte growth and inhibiting apoptosis. UDCA-LPE may represent a novel compound to facilitate liver regeneration and for treatment of liver diseases.
HepG2 - apoptosis - bile acid-phospholipid conjugate - hepatocytes growth