The bile acid-phospholipid conjugate Ursodeoxycholyl Lysophosphatidylethanolamide (UDCA-LPE) disturbs pro-fibrogenic Integrin and TGFβ signaling

Background: Integrin receptors, which are involved in cell-cell and cell-matrix interaction, emerge as crucial mediators of TGFβ1 activation in liver fibrosis and may therefore serve as attractive targets for anti-fibrogenic drug development. Ursodeoxycholyl Lysophosphatidylethanolamide (UDCA-LPE) is a synthetic bile acid-phospholipid conjugate with profound hepatoprotective and anti-fibrogenic functions in vitro and in vivo. Herein, we aimed to study the interaction of UDCA-LPE with pro-fibrogenic integrin and TGFβ1 signaling as crucial pathways during hepatofibrogenesis.

Results: To analyze the mechanism of function of UDCA-LPE, we investigated different signaling pathways by inhibitors treatment, immunofluorescence, lipid fractioning and HPLC-MS. We discovered, that integrins bound UDCA-LPE with the RGD recognition motif in CL48 liver cells and primary human hepatic stellate cells. After UDCA-LPE bound to integrins with its UDCA end, LPE end binding transporter proteins pulled UDCA-LPE together with bound integrins to LPE localization in lipid fractions. The translocation of integrins led to a loss of co-localization of integrins with the down-stream protein SRC, resulting in dephosphorylation of FAK (Tyr 925 and Tyr 576/577) and SRC (Tyr416). Taken together, UDCA-LPE disturbed integrin-FAK signaling by modifying the localization of integrins. UDCA-LPE further led to translocation of TGFβ receptor I and II, resulting in dephosphorylation of Smad2/3. Integrin blocking peptide RGD not only inhibited UDCA-LPE induced translocation of integrins, but also disturbed the translocation of TGFβ1 receptors with subsequent dephosphorylation of Smad2/3. These results suggest that the anti-fibrogenic effect of UDCA-LPE to TGFβ signaling is integrin dependent. Additionally, RGD peptide and UDCA-LPE shortly stimulated the phosphorylation of TGFβR2 (Ser 225), suggesting the involvement of integrins in TGFβ signaling.

Conclusions: UDCA-LPE mediated translocation of integrins and TGFβ receptors lead to a loss of co-localization with their down-stream signaling proteins SRC and Smad2/3. By inhibiting crucial pro-fibrogenic signaling pathways UDCA-LPE emerges as a promising experimental drug-candidate for the treatment of liver fibrosis.