Cyclosporin A blocks bile acid synthesis in cultured hepatocytes by specific inhibition of chenodeoxycholic acid synthesis

Princen, H.M.G.; Meijer, Piet; Wolthers, B.G.; Vonk, Roelf; Kuipers, Folkert

doi:10.1042/bj2750501

Cited by 102 publications

(71 citation statements)

References 34 publications

(45 reference statements)

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“…In previous studies of bile acid synthesis in cultured human hepatocytes, 14 C-labeled cholesterol has been added as a substrate. 6,43 In the present study, the hepatocytes were obtained from histologically normal donor liver tissue. The bile acids formed were cholic acid and chenodeoxycholic acid, normally synthesized in human liver.…”

Section: Discussionmentioning

confidence: 99%

“…[2][3][4][5] The quantitative importance as well as the regulation of the latter pathway is still being debated and is not yet clear. 6,7 Cholesterol 7␣-hydroxylase activity is known to be regulated by end-product inhibition by the bile acids returning to the liver from the gut via the portal vein. Other factors, such as hormones, may also be of importance in its regulation.…”

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Bile acid synthesis in primary cultures of rat and human hepatocytes

et al. 1998

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The regulation of hepatic bile acid formation is incompletely understood. Primary cultures of mammalian hepatocytes offer an opportunity to examine putative regulatory factors in relative isolation. Using rat and human hepatocytes in primary culture, we examined bile acid composition and the expression of the rate-limiting enzyme of formation, cholesterol 7␣-hydroxylase. Control rat hepatocytes showed a declining bile acid production over 4 days, from 156 ؎ 24 ng/mL (67% cholic acid) on day 1 to 55 ؎ 11 ng/mL (55% cholic acid) on day 4. In addition to cholic acid, chenodeoxycholic acid, ␣-muricholic acid, and ␤-muricholic acid were formed. Treatment with triidothyronine (T 3 ) or dexamethasone alone had no significant effect on bile acid production. A combination of T 3 and dexamethasone significantly increased the total bile acid production on day 4 (224 ؎ 54 ng/mL) and resulted in a marked change in composition to 23% cholic acid and 77% non-12␣-hydroxylated bile acids. Control rat hepatocytes had a cholesterol 7␣-hydroxylase activity of 3.3 ؎ 0.6 pmol/mg protein/min after 4 days in culture. Cells treated with the combination of dexamethasone and T 3 had an activity of 16.4 ؎ 3.6 pmol/mg protein/min. The cholesterol 7␣-hydroxylase messenger RNA (mRNA) levels, determined by solution hybridization after 4 days of culture, showed results similar to those for the activity data; control cells had 5.3 ؎ 0.9 cpm/ g total nucleic acids (tNAs). T 3-or dexamethasone-treated cells did not differ from control cells, whereas the combination of T 3 and dexamethasone increased the mRNA levels to 20.6 ؎ 2.8 cpm/ g tNAs. In human hepatocytes, isolated from donor liver, bile acid formation increased from 206 ؎ 79 ng/mL on day 2 to 1490 ؎ 594 ng/mL on day 6 and then declined slightly. Cholic acid and chenodeoxycholic acid were formed, constituting about 80% and 20%, respectively. The combined addition of T 3 and dexamethasone had a tendency to decrease rather than increase bile acid formation. Also, mRNA levels of the cholesterol 7␣-hydroxylase increased severalfold in the human hepatocytes from day 2 to day 4 and then declined. The addition of T 3 or dexamethasone did not effect the mRNA levels in any consistent way. It is noteworthy that the capacity of the cultured human hepatocytes to produce bile acids was higher than that of cultured rat hepatocytes, in spite of the fact that the production of bile acids in rat liver is 3-to 5-fold higher than that in human liver in vivo. It is also evident that while hormonal factors appear to regulate bile acid synthesis in the rat, no evidence for this was found in human hepatocytes. As the composition of bile acids secreted by human hepatocytes in primary culture closely resembles that found in vivo, this represents a useful model for further studies of the synthesis and regulation of bile acids. (HEPATOLOGY 1998;27: 615-620.)Bile acid synthesis is localized within the liver and represents an important pathway for cholesterol elimination from the body. The major bile acids, primarily f...

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Bile acid synthesis in primary cultures of rat and human hepatocytes

et al. 1998

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“…Cyclosporin has also been shown to inhibit apolipoprotein B (apoB) secretion from permeabilized Hep G2 cells (26) and has been implicated in causing cholestasis, with reduced bile acid synthesis, based on in vitro studies of inhibition of sterol 27-hydroxylase (2,21,31). Furthermore, LDL is produced in the plasma from very low-density lipoprotein (VLDL) as a result of metabolic cascades, and it is unclear whether any overproduction of VLDL is caused by cyclosporin.…”

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Cyclosporin-induced dyslipoproteinemia is associated with selective activation of SREBP-2

Zhu

Patel

1999

American Journal of Physiology-Endocrinology and Metabolism

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. Cyclosporin-induced dyslipoproteinemia is associated with selective activation of SREBP-2. Am. J. Physiol. 277 (Endocrinol. Metab. 40): E1087-E1094, 1999.-The use of cyclosporin A has contributed greatly to the success of organ transplantation. However, cyclosporin-associated side effects of hypertension, nephrotoxicity, and dyslipoproteinemia have tempered these benefits. Cyclosporin-induced dyslipoproteinemia may be an important risk factor for the accelerated atherosclerosis observed posttransplantation. Using a mouse model, we treated Swiss-Webster mice for 6 days with a daily dose of 20 µg/g body wt of cyclosporin and observed significant elevations of plasma cholesterol, triglyceride, and apolipoprotein B (apoB) levels relative to vehicle-alone treated control animals. Measurement of the rate of secretion of very lowdensity lipoprotein (VLDL) by the liver in vivo showed that cyclosporin treatment led to a significant increase in the rate of hepatic VLDL triglyceride secretion. Total apoB secretion was unaffected. Northern analysis showed that cyclosporin A treatment increased the abundance of hepatic mRNA levels for a number of key genes involved in cholesterol biosynthesis relative to vehicle-alone treated animals. Two key transcriptional factors, sterol regulatory element-binding protein (SREBP)-1 and SREBP-2, also showed differential expression; SREBP-2 expression was increased at the mRNA level, and there was an increase in the active nuclear form, whereas the mRNA and the nuclear form of SREBP-1 were reduced. These results show that the molecular mechanisms by which cyclosporin causes dyslipoproteinemia may, in part, be mediated by selective activation of SREBP-2, leading to enhanced expression of lipid metabolism genes and hepatic secretion of VLDL triglyceride.

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“…Bile acid synthesis via 27-hydroxylase (acidic pathway) accounts for a substantial fraction of bile acid synthesis under physiological conditions and after long-term bile drainage, at least in the rat 32,33 and mouse. 34 Additionally, modulation of this alternative pathway may differ from that of the classical cholesterol 7␣-hydroxylation pathway 35 or between species like rats [36][37][38] and rabbits.…”

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Complex feedback regulation of bile acid synthesis in the hamster: The role of newly synthesized cholesterol

et al. 1999

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Hepatic bile acid synthesis is regulated by recirculating bile acids, possibly by modulating the availability of newly synthesized and preformed cholesterol. Because data in the hamster on this mechanism are lacking, we fitted these animals with an extracorporeal bile duct and administered tritiated water intraperitoneally to label newly formed cholesterol. After interruption of the enterohepatic circulation, physiological and double-physiological doses of conjugated cholate (25 or 50 mol/100 g · h) or of unconjugated deoxycholate (6 or 12 mol) were infused intraduodenally for 54 hours and compared with controls. De novo and preformed cholesterol directly secreted into bile or used for cholate and chenodeoxycholate synthesis were quantitated by high-pressure liquid chromatography (HPLC)-liquid scintillation. Directly after depletion of the bile acid pool (6-9 hours) at nearly physiological conditions, chenodeoxycholate synthesis was significantly reduced by cholate and deoxycholate by up to 45% to 51%, whereas cholate formation decreased by Ϸ22% during deoxycholate. This short-term effect was mainly mediated by reduced synthesis from preformed cholesterol. After long-term bile depletion (30-54 hours), bile acid synthesis returned to control levels during 25 mol of cholate and of both deoxycholate doses. In contrast, only 50 mol of cholate prevented derepression of bile acid synthesis. This long-term effect was mainly attributed to a diminished formation from de novo cholesterol exceeding the reduced synthesis from preformed cholesterol. In summary, short-and long-term regulation of bile acid synthesis in hamsters differs with respect to availabilities of preformed and de novo cholesterol. (HEPATOL-OGY 1999;30:230-237.)

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Cyclosporin A blocks bile acid synthesis in cultured hepatocytes by specific inhibition of chenodeoxycholic acid synthesis

Cited by 102 publications

References 34 publications

Bile acid synthesis in primary cultures of rat and human hepatocytes

Bile acid synthesis in primary cultures of rat and human hepatocytes

Cyclosporin-induced dyslipoproteinemia is associated with selective activation of SREBP-2

Complex feedback regulation of bile acid synthesis in the hamster: The role of newly synthesized cholesterol

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