P Milkiewicz1, M G Roma, E Elias, R Coleman. 1. School of Biosciences, and Liver and Hepatobiliary Unit, University of Birmingham, Birmingham B17 2TT, UK.
Abstract
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. AIMS: 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.
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. AIMS: 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.
Authors: S Ganesan; R Calle; K Zawalich; J I Smallwood; W S Zawalich; H Rasmussen Journal: Proc Natl Acad Sci U S A Date: 1990-12 Impact factor: 11.205
Authors: Andréa M A Costa; Beatriz Tuchweber; Thierry Lamireau; Ibrahim M Yousef; Charles Balabaud; Jean Rosenbaum; Alexis Desmoulière Journal: Virchows Arch Date: 2003-03-26 Impact factor: 4.064
Authors: F A Crocenzi; A D Mottino; E J Sánchez Pozzi; J M Pellegrino; E A Rodríguez Garay; P Milkiewicz; M Vore; R Coleman; M G Roma Journal: Gut Date: 2003-08 Impact factor: 23.059