Hepatoprotection with tauroursodeoxycholate and beta muricholate against taurolithocholate induced cholestasis: involvement of signal transduction pathways.
BACKGROUND
Tauroursodeoxycholate (TUDC) provides partial protection against taurolithocholate (TLC) induced cholestasis, possibly by inducing a signalling cascade activating protein kinase C (PKC). The potential protective effects of beta muricholic acid (beta-MC), another 7-beta-hydroxylated bile salt, have not previously been studied in TLC cholestasis.


OBJECTIVE
To study the effect of beta-MC on TLC induced cholestasis and also to investigate further the effects of agents affecting intracellular signalling, notably DBcAMP (a cell permeable cAMP analogue) and several protein kinase inhibitors.


METHODS
Functional studies were carried out analysing the proportion of hepatocyte couplets able to accumulate the fluorescent bile acid analogue cholyl-lysyl-fluorescein (CLF) into their sealed canalicular vacuole (cVA of CLF assay).


RESULTS
It was found that both beta-MC and DBcAMP were as effective as TUDC in protecting against TLC induced cholestasis. The PKC inhibitors staurosporin and H7 but not the specific protein kinase A (PKA) inhibitor KT5720 abolished the protective effects of TUDC and beta-MC. BAPTA/AM, a chelator of intracellular Ca(2+), significantly decreased the protective effect of both bile salts, and that of DBcAMP. PKC and PKA inhibitors had no effect on protection with DBcAMP.


CONCLUSIONS
Beta-MC was as effective as TUDC in protecting against TLC cholestasis. Mobilisation of Ca(2+) and activation of PKC, but not of PKA, are involved in the anticholestatic effect of the two 7-beta-hydroxylated bile salts. The hepatoprotective effects of DBcAMP involved Ca(2+) mobilisation, but not PKC or PKA activation.
Milkiewicz
P
P
School of Biosciences, and Liver and Hepatobiliary Unit, University of Birmingham, Birmingham B17 2TT, UK.
Roma
M G
MG
Elias
E
E
Coleman
R
R
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D003994:Bucladesine / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002227:Carbazoles; D002614:Chelating Agents / Q000494:pharmacology; D002756:Cholagogues and Choleretics / Q000627:therapeutic use*; D002779:Cholestasis / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D002793:Cholic Acids / Q000627:therapeutic use*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D013655:Taurochenodeoxycholic Acid / Q000627:therapeutic use*; D013658:Taurolithocholic Acid
D002227:Carbazoles; D002614:Chelating Agents; D002756:Cholagogues and Choleretics; D002793:Cholic Acids; D004791:Enzyme Inhibitors; D007211:Indoles; D011758:Pyrroles; C004821:muricholic acid; D013655:Taurochenodeoxycholic Acid; D013658:Taurolithocholic Acid; D004533:Egtazic Acid; C057416:KT 5720; C031655:ursodoxicoltaurine; D003994:Bucladesine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium