Abcg5/Abcg8-independent pathways contribute to hepatobiliary cholesterol secretion in mice

2006 ◽  
Vol 291 (3) ◽  
pp. G414-G423 ◽  
Author(s):  
Torsten Plösch ◽  
Jelske N. van der Veen ◽  
Rick Havinga ◽  
Nicolette C. A. Huijkman ◽  
Vincent W. Bloks ◽  
...  
Keyword(s):  
Total Sterol ◽  
Wild Type ◽  
Hepatic Expression ◽  
Maximal Stimulation ◽  
Functional Complex ◽  
Cholesterol Excretion ◽  
Excretion Rates ◽  
Cholesterol Secretion ◽  
Sterol Excretion

The ATP-binding cassette (ABC) half-transporters ABCG5 and ABCG8 heterodimerize into a functional complex that mediates the secretion of plant sterols and cholesterol by hepatocytes into bile and their apical efflux from enterocytes. We addressed the putative rate-controlling role of Abcg5/Abcg8 in hepatobiliary cholesterol excretion in mice during (maximal) stimulation of this process. Despite similar bile salt (BS) excretion rates, basal total sterol and phospholipid (PL) output rates were reduced by 82% and 35%, respectively, in chow-fed Abcg5−/− mice compared with wild-type mice. When mice were infused with the hydrophilic BS tauroursodeoxycholate, similar relative increases in bile flow, BS output, PL output, and total sterol output were observed in wild-type, Abcg5+/−, and Abcg5−/− mice. Maximal cholesterol and PL output rates in Abcg5−/− mice were only 15% and 69%, respectively, of wild-type values. An infusion of increasing amounts of the hydrophobic BS taurodeoxycholate increased cholesterol excretion by 3.0- and 2.4-fold in wild-type and Abcg5−/− mice but rapidly induced cholestasis in Abcg5−/− mice. Treatment with the liver X receptor (LXR) agonist T0901317 increased the maximal sterol excretion capacity in wild-type mice (fourfold), concomitant with the induction of Abcg5/ Abcg8 expression, but not in Abcg5−/− mice. In a separate study, mice were fed chow containing 1% (wt/wt) cholesterol. As expected, hepatic expression of Abcg5 and Abcg8 was strongly induced (fivefold and fourfold) in wild-type but not LXR-α-deficient ( Lxra−/−) mice. Surprisingly, hepatobiliary cholesterol excretion was increased to the same extent, i.e., 2.2-fold in wild-type mice and 2.0-fold in Lxra−/− mice, upon cholesterol feeding. Our data confirm that Abcg5, as part of the Abcg5/Abcg8 heterodimer, strongly controls hepatobiliary cholesterol secretion in mice. However, our data demonstrate that Abcg5/Abcg8 heterodimer-independent, inducible routes exist that can significantly contribute to total hepatobiliary cholesterol output.

Abstract 106: Transintestinal Cholesterol Excretion and Macrophage Reverse Cholesterol Transport are not Stimulated in Hepatic ABCG8 Knockdown Mice Treated with an LXR Agonist

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Allison L McDaniel ◽  
Ryan E Temel ◽  
J M Brown ◽  
Richard G Lee ◽  
Mark J Graham ◽  
...  
Keyword(s):  
Hepatic Cholesterol ◽  
Wild Type ◽  
Biliary Cholesterol ◽  
Neutral Sterol ◽  
Atp Binding Cassette Transporter ◽  
Cholesterol Excretion ◽  
Biliary Cholesterol Secretion ◽  
Lxr Agonists ◽  
Cholesterol Secretion ◽  
Sterol Excretion

Transintestinal cholesterol excretion (TICE) is a recently discovered pathway by which cholesterol travels from plasma to the small intestine for direct excretion into the feces. Hallmarks of animal models with TICE include severely diminished biliary cholesterol secretion but near normal levels of hepatic cholesterol and fecal neutral sterol excretion. Using an ATP binding cassette transporter G8 (ABCG8) antisense oligonucleotide (ASO) to knock down ABCG8 specifically in liver (G8 HKD ), we created a novel mouse model with significantly decreased biliary cholesterol excretion but a 658% increase in hepatic cholesterol accumulation and a 78% reduction in fecal neutral sterol excretion, indicating a dysfunction in the TICE pathway. LXR agonists have previously been shown to stimulate the TICE pathway. In order to more definitively prove the TICE pathway was disfunctional in G8 HKD mice, we treated wild type (WT) and G8 HKD mice with the LXR agonist T0901317 and measured markers of TICE stimulation. As expected, in WT mice, T0901317 doubled biliary cholesterol concentrations. A similar effect was seen in G8 HKD mice treated with T0901317, but biliary cholesterol concentrations remained significantly less than their WT counterparts. These levels of biliary cholesterol closely mirrored hepatic ABCG8 mRNA expression. T0901317 stimulated fecal neutral sterol excretion by >1000% in wild type mice but only by 190% in G8 HKD mice. These data indicate that TICE is disfunctional in G8 HDK mice since the pathway was not stimulated to the same extent in WT and G8 HKD mice by an LXR agonist. Some controversy remains over whether the TICE pathway transports macrophage derived cholesterol. In order to address this issue, we performed a macrophage RCT assay on WT and TICE disfunctional G8 HKD mice. T0901317 stimulated macrophage RCT (fecal neutral sterol 3H dpm) by >2300% in wild type mice but only by 370% in G8 HKD mice. T0901317 increased fecal acidic sterol 3H count by 65-75% in both wild type and G8 HKD mice. These results indicate that macrophage RCT is impaired when the TICE pathway is decreased. In sum, our data shows that hepatic ABCG8 plays a key role in the TICE pathway and that impairing the TICE pathway through hepatic ABCG8 knockdown causes decreased macrophage RCT.

Abstract 390: The Absence of Abcg5 Abcg8 Reveals a Sexually Dimorphic Adaption to Impaired Biliary Cholesterol Secretion

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Jianing Li ◽  
Ailing Ji ◽  
Ryan E Temel ◽  
Deneys R van der Westhuyzen ◽  
Gregory A Graf
Keyword(s):  
Alternative Pathway ◽  
Male Mice ◽  
Biliary Cholesterol ◽  
Female Mice ◽  
Cholesterol Excretion ◽  
Biliary Cholesterol Secretion ◽  
Cholesterol Secretion ◽  
The Impact ◽  
Sterol Excretion ◽  
Secretion Rates

Objective: The ABCG5 ABCG8 (G5G8) sterol transporter is the primary mechanism for biliary cholesterol secretion, but mice maintain fecal sterol excretion in its absence. The mechanism by which mice maintain sterol excretion in the absence of this pathway is not known. Transintestinal cholesterol excretion (TICE) is an alternative pathway to hepatobiliary secretion. We investigated the impact of G5G8 deficiency on TICE in the absence of Sitosterolemia. Methods and Results: We compared both hepatobiliary and transintestinal cholesterol excretion rates in wild-type (WT) and G5G8 deficient mice of both sexes. WT and G5G8 were maintained on a plant-sterol free diet from the time of weaning to prevent the development of secondary phenotypes associated with Sitosterolemia. Biliary and intestinal cholesterol secretion rates were determined by biliary diversion with simultaneous perfusion of the proximal 10 cm of the small bowel. Among WT mice, biliary cholesterol secretion was greater in female mice compared to males. Conversely, male mice exhibited greater rates of TICE than females. As expected, WT mice had higher biliary cholesterol secretion rates than their G5G8 deficient littermates. However, the decline in biliary cholesterol secretion was far less in male mice compared to females in the absence of G5G8. In female mice, the absence of G5G8 resulted in a two-fold increase in TICE, whereas males were unaffected. Conclusion: Female mice are more dependent upon the biliary pathway for cholesterol excretion, whereas males are more dependent upon TICE. G5G8 independent pathways are present for both biliary and intestinal cholesterol secretion. Female and male mice differ in their adaptation to G5G8 deficiency in order to maintain fecal sterol excretion.

scholarly journals Ecto-Nucleotide Triphosphate Diphosphohydrolase-2 (NTPDase2) Deletion Increases Acetaminophen-Induced Hepatotoxicity

2020 ◽  
Vol 21 (17) ◽  
pp. 5998
Author(s):  
Linda Feldbrügge ◽  
Katrin Splith ◽  
Ines Kämmerer ◽  
Sandra Richter ◽  
Anna Riddermann ◽  
...  
Keyword(s):  
Liver Injury ◽  
Liver Toxicity ◽  
Wild Type ◽  
Protective Properties ◽  
Hepatic Expression ◽  
Markers Of Inflammation ◽  
Acute Necrotizing ◽  
Portal Fibroblast ◽  
Portal Fibroblasts

Ecto-nucleotidase triphosphate diphosphohydrolase-2 (NTPDase2) is an ecto-enzyme that is expressed on portal fibroblasts in the liver that modulates P2 receptor signaling by regulating local concentrations of extracellular ATP and ADP. NTPDase2 has protective properties in liver fibrosis and may impact bile duct epithelial turnover. Here, we study the role of NTPDase2 in acute liver injury using an experimental model of acetaminophen (APAP) intoxication in mice with global deletion of NTPDase2. Acute liver toxicity was caused by administration of acetaminophen in wild type (WT) and NTPDase2-deficient (Entpd2 null) mice. The extent of liver injury was compared by histology and serum alanine transaminase (ALT). Markers of inflammation, regeneration and fibrosis were determined by qPCR). We found that Entpd2 expression is significantly upregulated after acetaminophen-induced hepatotoxicity. Entpd2 null mice showed significantly more necrosis and higher serum ALT compared to WT. Hepatic expression of IL-6 and PDGF-B are higher in Entpd2 null mice. Our data suggest inducible and protective roles of portal fibroblast-expressed NTPDase2 in acute necrotizing liver injury. Further studies should investigate the relevance of these purinergic pathways in hepatic periportal and sinusoidal biology as such advances in understanding might provide possible therapeutic targets.

scholarly journals High-salt intake enhances superoxide activity in eNOS knockout mice leading to the development of salt sensitivity

2010 ◽  
Vol 299 (3) ◽  
pp. F656-F663 ◽  
Author(s):  
Libor Kopkan ◽  
Arthur Hess ◽  
Zuzana Husková ◽  
Luděk Červenka ◽  
L. Gabriel Navar ◽  
...  
Keyword(s):  
Salt Intake ◽  
Salt Sensitivity ◽  
High Salt ◽  
No Production ◽  
Wild Type ◽  
Total N ◽  
High Salt Intake ◽  
Excretion Rates ◽  
Salt Sensitive Hypertension

A deficiency in nitric oxide (NO) generation leads to salt-sensitive hypertension, but the role of increased superoxide (O2−) in such salt sensitivity has not been delineated. We examined the hypothesis that an enhancement in O2− activity induced by high-salt (HS) intake under deficient NO production contributes to the development of salt-sensitive hypertension. Endothelial NO synthase knockout (eNOS KO; total n = 64) and wild-type (WT; total n = 58) mice were given diets containing either normal (NS; 0.4%) or high-salt (HS; 4%) for 2 wk. During this period, mice were chronically treated with a O2− scavenger, tempol (400 mg/l), or an inhibitor of NADPH oxidase, apocynin (1 g/l), in drinking water or left untreated ( n = 6–8 per group). Blood pressure was measured by radiotelemetry and 24-h urine samples were collected in metabolic cages. Basal mean arterial pressure (MAP) in eNOS KO was higher (125 ± 4 vs. 106 ± 3 mmHg) compared with WT. Feeding HS diet did not alter MAP in WT but increased it in eNOS KO to 166 ± 9 mmHg. Both tempol and apocynin treatment significantly attenuated the MAP response to HS in eNOS KO (134 ± 3 and 139 ± 4 mmHg, respectively). Basal urinary 8-isoprostane excretion rates (UIsoV), a marker for endogenous O2− activity, were similar (2.8 ± 0.2 and 2.4 ± 0.3 ng/day) in both eNOS KO and WT mice. However, HS increased UIsoV more in eNOS KO than in WT (4.6 ± 0.3 vs. 3.8 ± 0.2 ng/day); these were significantly attenuated by both tempol and apocynin treatment. These data indicate that an enhancement in O2− activity contributes substantially to the development of salt-sensitive hypertension under NO-deficient conditions.

scholarly journals Gamble's “economy of water” revisited: studies in urea transporter knockout mice

2006 ◽  
Vol 291 (1) ◽  
pp. F148-F154 ◽  
Author(s):  
Robert A. Fenton ◽  
Chung-Lin Chou ◽  
Holly Sowersby ◽  
Craig P. Smith ◽  
Mark A. Knepper
Keyword(s):  
Collecting Duct ◽  
Specific Interaction ◽  
Special Role ◽  
Wild Type ◽  
Osmotic Diuresis ◽  
Nacl Transport ◽  
Water Excretion ◽  
Concentrating Mechanism ◽  
Excretion Rates

The Gamble phenomenon (initially described over 70 years ago as “an economy of water in renal function referable to urea”) suggested that urea plays a special role in the urinary concentrating mechanism and that the concentrating mechanism depends in some complex way on an interaction between NaCl and urea. In this study, the role of collecting duct urea transporters in the Gamble phenomenon was investigated in wild-type mice and mice in which the inner medulla collecting duct (IMCD) facilitative urea transporters, UT-A1 and UT-A3, had been deleted ( UT-A1/3−/− mice). The general features of the Gamble phenomenon were confirmed in wild-type mice, namely 1) the water requirement for the excretion of urea is less than for the excretion of an osmotically equivalent amount of NaCl; and 2) when fed various mixtures of urea and salt in the diet, less water is required for the excretion of the two substances together than the amount of water needed for the excretion of the two substances separately. In UT-A1/3−/− mice both of these elements of the phenomenon were absent, indicating that IMCD urea transporters play a central role in the Gamble phenomenon. A titration study in which wild-type mice were given progressively increasing amounts of urea showed that the ability of the kidney to reabsorb urea was saturable, resulting in osmotic diuresis above excretion rates of ∼6,000 μosmol/day. In the same titration experiments, when increasing amounts of NaCl were added to the diet, mice were unable to increase urinary NaCl concentrations to >420 mM, resulting in osmotic diuresis at NaCl excretion rates of ∼3,500 μosmol/day. Thus both urea and NaCl can induce osmotic diuresis when large amounts are given, supporting the conclusion that the decrease in water excretion with mixtures of urea and NaCl added to the diet (compared with pure NaCl or urea) is due to the separate abilities of urea and NaCl to induce osmotic diuresis, rather than to any specific interaction of urea transport and NaCl transport at an epithelial level.

Differential Role of Components of the Fibrinolytic System in the Formation and Removal of Thrombus Induced by Endothelial Injury

1999 ◽  
Vol 81 (04) ◽  
pp. 601-604 ◽  
Author(s):  
Hiroyuki Matsuno ◽  
Osamu Kozawa ◽  
Masayuki Niwa ◽  
Shigeru Ueshima ◽  
Osamu Matsuo ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Thrombus Formation ◽  
Endothelial Injury ◽  
Fibrinolytic System ◽  
Tissue Type ◽  
Clot Lysis ◽  
Wild Type ◽  
Type Plasminogen Activator ◽  
Pai 1

SummaryThe role of fibrinolytic system components in thrombus formation and removal in vivo was investigated in groups of six mice deficient in urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), or plasminogen activator inhibitor-1 (PAI-1) (u-PA-/-, t-PA-/- or PAI-1-/-, respectively) or of their wild type controls (u-PA+/+, t-PA+/+ or PAI-1+/+). Thrombus was induced in the murine carotid artery by endothelial injury using the photochemical reaction between rose bengal and green light (540 nm). Blood flow was continuously monitored for 90 min on day 0 and for 20 min on days 1, 2 and 3. The times to occlusion after the initiation of endothelial injury in u-PA+/+, t-PA+/+ or PAI-1+/+ mice were 9.4 ± 1.3, 9.8 ± 1.1 or 9.7 ± 1.6 min, respectively. u-PA-/- and t-PA-/- mice were indistinguishable from controls, whereas that of PAI-1-/- mice were significantly prolonged (18.4 ± 3.7 min). Occlusion persisted for the initial 90 min observation period in 10 of 18 wild type mice and was followed by cyclic reflow and reocclusion in the remaining 8 mice. At day 1, persistent occlusion was observed in 1 wild type mouse, 8 mice had cyclic reflow and reocclusion and 9 mice had persistent reflow. At day 2, all injured arteries had persistent reflow. Persistent occlusion for 90 min on day 0 was observed in 3 u-PA-/-, in all t-PA-/- mice at day 1 and in 2 of the t-PA-/-mice at day 2 (p <0.01 versus wild type mice). Persistent patency was observed in all PAI-1-/- mice at day 1 and in 5 of the 6 u-PA-/- mice at day 2 (both p <0.05 versus wild type mice). In conclusion, t-PA increases the rate of clot lysis after endothelial injury, PAI-1 reduces the time to occlusion and delays clot lysis, whereas u-PA has little effect on thrombus formation and spontaneous lysis.

scholarly journals Salicylic Acid Accumulation Controlled by LSD1 Is Essential in Triggering Cell Death in Response to Abiotic Stress

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 962
Author(s):  
Maciej Jerzy Bernacki ◽  
Anna Rusaczonek ◽  
Weronika Czarnocka ◽  
Stanisław Karpiński
Keyword(s):  
Cell Death ◽  
Salicylic Acid ◽  
Abiotic Stress ◽  
Wild Type ◽  
Pr Genes ◽  
Genes Expression ◽  
Salicylic Acid Accumulation ◽  
Cell Death Phenotype ◽  
Insight Into

Salicylic acid (SA) is well known hormonal molecule involved in cell death regulation. In response to a broad range of environmental factors (e.g., high light, UV, pathogens attack), plants accumulate SA, which participates in cell death induction and spread in some foliar cells. LESION SIMULATING DISEASE 1 (LSD1) is one of the best-known cell death regulators in Arabidopsis thaliana. The lsd1 mutant, lacking functional LSD1 protein, accumulates SA and is conditionally susceptible to many biotic and abiotic stresses. In order to get more insight into the role of LSD1-dependent regulation of SA accumulation during cell death, we crossed the lsd1 with the sid2 mutant, caring mutation in ISOCHORISMATE SYNTHASE 1(ICS1) gene and having deregulated SA synthesis, and with plants expressing the bacterial nahG gene and thus decomposing SA to catechol. In response to UV A+B irradiation, the lsd1 mutant exhibited clear cell death phenotype, which was reversed in lsd1/sid2 and lsd1/NahG plants. The expression of PR-genes and the H2O2 content in UV-treated lsd1 were significantly higher when compared with the wild type. In contrast, lsd1/sid2 and lsd1/NahG plants demonstrated comparability with the wild-type level of PR-genes expression and H2O2. Our results demonstrate that SA accumulation is crucial for triggering cell death in lsd1, while the reduction of excessive SA accumulation may lead to a greater tolerance toward abiotic stress.

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