Angiotensin-Converting Enzyme Inhibitor Enhances Liver Regeneration Following Partial Hepatectomy: Involvement of Bradykinin B2 and Angiotensin AT1 Receptors

Searching for the link; mechanisms underlying liver regeneration and recurrence of colorectal liver metastasis post partial hepatectomy

Despite excellent treatment of primary colorectal cancer, the majority of deaths occur as a result of metastasis to the liver. Recent population studies have estimated that one quarter of patients with colorectal cancer will incur synchronous or metachronous colorectal liver metastasis. However, only one quarter of these patients will be eligible for potentially curative resection. Tumor recurrence occurs in reportedly 60% of patients undergoing hepatic resection, and the majority of intrahepatic recurrence occurs within the first 6 months of surgery. The livers innate ability to restore its homeostatic size, and volume facilitates major hepatic resection that currently offers the only chance of cure to patients with extensive hepatic metastases. Experimental and clinical evidence supports the notion that following partial hepatectomy, liver regeneration (LR) paradoxically drives tumor progression and increases the risk of recurrence. It is becoming increasingly clear that the processes that drive liver organogenesis, regeneration, and tumor progression are inextricably linked. This presents a major hurdle in the management of colorectal liver metastasis and other hepatic malignancies because therapies that reduce the risk of recurrence without hampering LR are sought. The processes and pathways underlying these phenomena are multiple, complex, and cross-communicate. In this review, we will summarize the common mechanisms contributing to both LR and tumor recurrence.

Coordinated cytochrome P450 expression in mouse liver and intestine under different dietary conditions during liver regeneration after partial hepatectomy

Liver resection is performed to remove tumors in patients with liver cancer, but the procedure's suitability depends on the regenerative ability of the liver. It is important to consider the effects of exogenous factors, such as diets, on liver regeneration for the recovery of function. The evaluation of drug metabolism during liver regeneration is also necessary because liver dysfunction is generally observed after the operation. Here, we investigated the influence of a purified diet (AIN-93G) on liver regeneration and changes in the mRNA expression of several cytochrome P450 (CYP) isoforms in the liver and small intestine using a two-thirds partial hepatectomy (PH) mouse model fed with a standard diet (MF) and a purified diet. Liver regeneration was significantly delayed in the purified diet group relative to that in the standard diet group. The liver Cyp2c55 and Cyp3a11 expression was increased at 3 day after PH especially in the purified diet group. Bile acid may partly cause the differences in liver regeneration and CYP expression between two types of diets. On the other hand, Cyp3a13 expression in the small intestine was transiently increased at day 1 after PH in both diet groups. The findings suggest that compensatory induction of the CYP expression occurred in the small intestine after attenuation of drug metabolism potential in the liver. The present results highlight the importance of the relationship between liver regeneration, drug metabolism, and exogenous factors for the effective treatment, including surgery and medication, in patients after liver resection or transplantation.

Effect of non-alcoholic liver disease on recurrence rate and liver regeneration after liver resection for colorectal liver metastases

BACKGROUND

Resection of metastases is the only potential cure for patients with liver metastasis from colorectal cancer (crc-lm). But despite an improved overall 5-year survival, the recurrence rate is still as high as 60%. Non-alcoholic fatty liver disease (nafld) can decrease the liver's capacity to regenerate after resection and might also affect cancer recurrence, potentially by elevating transforming growth factor β, levels of specific metalloproteinases, and oxidative stress. The objective of the present work was to determine the effect of the histologic features of nafld on cancer recurrence and liver regeneration.

METHODS

This retrospective analysis considered 60 patients who underwent an R0 hepatectomy for crc-lm. Volumetric analysis of the liver was calculated using axial view, portovenous phase, 2.5 mm thickness, multiphasic computed tomography images taken before and after surgery. The histologic features of nafld (steatosis, inflammation, and ballooning) were scored using the nafld activity score, and the degree of fibrosis was determined.

RESULTS

The hepatic recurrence rate was 38.33%. Median overall survival duration was 56 months. Median disease-free survival duration was 14 months, and median hepatic disease-free survival duration was 56 months. Multivariate analysis revealed significant correlations of hepatic disease-free survival with hepatocyte ballooning (p = 0.0009), lesion diameter (p = 0.014), and synchronous disease (p = 0.006). Univariate and multivariate analyses did not reveal any correlation with degree of steatosis or recurrence rate.

CONCLUSIONS

This study reveals an important potential negative effect of hepatocyte ballooning on hepatic disease-free survival.

Is Serum Angiotensin-Converting Enzyme Level Useful For Determining Necroinflammatory Activity In Chronic Hepatitis B Infection?

AIM

The purpose of this study was to investigate the relationship between the findings from liver biopsy and the serum angiotensin-converting enzyme (ACE) level to determine whether ACE might serve as a potential noninvasive sign of necroinflammatory activity in patients with Chronic Hepatitis B (CHB) infection.

METHODS

A total of 54 CHB patients referred for liver biopsy were enrolled in the study. Serum ACE levels were determined photometrically with a kinetic test.

RESULTS

The aspartate aminotransferase (AST), alanine aminotransferase (ALT), hepatitis B virus-deoxyribonucleic acid (HBV-DNA), histological activity index (HAI), and white blood cell counts were higher in patients with severe fibrosis, while albumin levels were low. The serum ACE levels showed a statistically significant correlation with HBV-DNA, HAI score, and ALT-AST levels.

DISCUSSION

In this study, a statistically significant relation between serum ACE levels and HAI scores was observed. This represents the first analysis to compare necroinflammation of the liver and serum ACE levels. There may be some explanations that the suppression of hepatocyte growth factor (HGF) by Angiotensin II and increased inflammatory damage might be a reason for the correlation between HAI and ACE. Serum ACE levels, HBV-DNA levels, and serum transaminase levels might be used together as noninvasive markers for the prediction of necroinflammation in CHB patients.

Effect of angiotensin-converting enzyme inhibitor, lisinopril on morphological and biochemical aspects of fibrotic liver regeneration

BACKGROUND/AIMS

Hepatic fibrosis results in defective liver regeneration following partial hepatectomy. Angiotensin converting enzyme (ACE) inhibitors can enhance liver regeneration and are also involved in the reduction of hepatic fibrosis. The present study has been conducted to evaluate the potential effect of an ACE inhibitor, lisinopril, on the morphological and biochemical aspects of fibrotic liver regeneration.

MATERIALS AND METHODS

Eight-week old female Sprague Dawley rats were made fibrotic by intragastric carbon tetrachloride treatment. Rats were given saline or lisinopril (1 mg/kg) orally for 1 week and were subjected to sham surgery or two-third partial hepatectomy. Liver regenerative and functional capacities were determined 48 hours post surgery.

RESULTS

Lisinopril administration did not affect the regeneration rate, proliferation cell nuclear antigen count, and hepatocellular area of fibrotic livers following partial hepatectomy. No statistically significant difference between treated and control rats regarding mitotic count, hepatocyte nuclear area, and binuclear hepatocyte frequency was observed. Serum biochemical analysis showed that lisinopril non-significantly decreased the partial hepatectomy induced elevated levels of alanine aminotransferase, aspartate transaminase, and alkaline phosphatase whereas lactate dehydrogenase and total bilirubin levels were significantly reduced. No marked reduction in hepatic collagen content and alpha smooth actin positive cells was observed by lisinopril treatment.

CONCLUSION

ACE inhibitor lisinopril did not produce major histomorphological alterations in regenerating fibrotic liver following partial hepatectomy, however, it may improve its functional capability.

Blockade of the renin-angiotensin system inhibits growth of colorectal cancer liver metastases in the regenerating liver

Partial hepatectomy (PH), the preferred option for selected patients with colorectal cancer liver metastases (CRCLM), is associated with 40-80% tumor recurrence rates. Renin-angiotensin system (RAS) blockade inhibits tumor growth and has been suggested to improve liver regeneration. We documented the effect of RAS blockade on tumor growth and liver regeneration in a murine model. CRCLM induction followed by 70% PH was performed on 78 CBA mice. Liver regeneration (days 2, 6) and CRCLM tumor load were measured by liver (and tumor) weights, percentage of CRCLM burden and tumor nodule count (days 16, 21). mRNA expression of the RAS components was characterised. Statistical analysis was performed using 2-independent sample T test or Mann-Whitney test (SPSS). Captopril did not impair liver regeneration. By day 21, Captopril decreased tumor burden (percentage of CRCLM in the liver) (48.7 ± 4.7% control, 24.4 ± 6.2 Captopril; p = 0.008), tumor volume (1046.2 ± 200.2 mm(3), 388.3 ± 150.4; p = 0.02), tumor nodule count per image field (181.1 ± 28.5, 68 ± 17.6; p = 0.005) and tumor angiogenesis (71.8 ± 6.4 vessels/mm(2), 43.1 ± 7.6; p = 0.015) compared to controls. Captopril enhanced tumor apoptosis (1 ± 0.2%, 2.5 ± 0.7; p = 0.028). Liver regeneration and tumor development increased liver ACE levels. Blockade of the RAS effectively retarded CRCLM tumor growth at the late stage of tumor development within the regenerating liver without impeding liver regeneration following PH, via anti-angiogenesis and pro-tumor apoptosis. Captopril may be of therapeutic benefit in patients undergoing PH for CRCLM.

Blockade of the renin-angiotensin system improves the early stages of liver regeneration and liver function

BACKGROUND

Partial hepatectomy is the preferred option for selected patients with colorectal cancer liver metastases (CRCLM). Sufficient liver regeneration (LR) is essential for a successful outcome in these patients. The blockade of the renin-angiotensin system (RAS) reduces the growth of several tumor types. The RAS also acts as a regulator of liver fibrosis and potentially LR. The angiotensin-converting enzyme (ACE) inhibitor, captopril, significantly inhibits the growth of CRCLM, but its effect on LR remains undefined.

METHODS

After 70% of partial hepatectomy, mice were randomly assigned to control or captopril-treated groups. LR was measured by liver-to-body weight ratio on days 1, 2, 4, 6, and 8. Hepatocyte proliferation, apoptosis and cell size, hepatic stellate cell (HSC) count, and sinusoidal endothelial cell density were quantified. Matrix metalloproteinase 9 (MMP-9) protein levels, liver injury markers, and RAS messenger RNA levels were also determined.

RESULTS

At day 2, captopril increased liver-to-body weight ratio (56.5 ± 1.7 captopril versus 49.3 ± 2.4 control, P = 0.027). This was associated with increased HSC count (65.4 ± 4.8 cells per 100,000 μm(2), 48.7 ± 2.3, P = 0.007) and MMP-9 levels (0.68 ± 0.12 AU, 0.12 ± 0.04, P = 0.014). The messenger RNA levels of angiotensin-converting enzyme (P = 0.045) and angiotensin 1 receptor (P = 0.039) were reduced by captopril at day 2.

CONCLUSION

Captopril enhanced early LR. This effect was associated with increased HSC numbers and MMP-9 protein, whereas hepatocyte proliferation was lower than controls. Captopril may provide a beneficial treatment option for the management of patients with CRCLM.

Two drugs with paradoxical effects on liver regeneration through antiangiogenesis and antifibrosis: Losartan and Spironolactone: a pharmacologic dilemma on hepatocyte proliferation

BACKGROUND

There is a strong relationship between liver regeneration and angiogenesis and fibrosis. It is known that Spironolactone, an aldosterone antagonist, acting on rennin-aldosterone axis, and Losartan, an angiotensin II type I antagonist, have both antifibrotic and antiangiogenic effects. Theoretically, the end result of these mechanisms with contradictory influences on liver regeneration is not known well. In this study, we aimed to reveal the effects on liver regeneration of administration of Spironolactone and Losartan, having contradicting effects on regeneration through antiangiogenesis and antifibrosis.

MATERIALS AND METHODS

A total of 72 Wistar albino rats were divided into control, Spironolactone, and Losartan groups and subdivided to conduct examinations on days 1, 3, 5, and 7. The specimens were treated with proliferating cell nuclear antigen to evaluate the characteristics of liver regeneration; with phosphorylated Smad2 (phospho-Smad2), serum transforming growth factor beta (TGF-B) 1, and tissue TGF-B1 to evaluate the termination of regeneration and with vascular endothelial growth factor receptor 2, Flk-1/KDR, to evaluate angiogenesis.

RESULTS

The proliferating cell nuclear antigen-labeling index was found to be significantly higher in Spironolactone and Losartan groups than in the control group on days 1, 3, and 5 (P = 0.031, 0.0023, and 0.032, respectively). Vascular endothelial growth factor receptor 2, Flk-1/KDR, expression was significantly lower in Spironolactone and Losartan groups than in the control group on days 3, 5, and 7 (P = 0.032, 0.0024, and 0.007, respectively). Phospho-Smad2 was significantly lower on days 1, 3, and 5 in Spironolactone and Losartan groups than in the control group (P = 0.011, 0.0020, and 0.05, respectively). Tissue TGF-B1 levels were significantly lower in Spironolactone and Losartan groups than in the control group only on day 3 (P = 0039). Serum TGF-B1 levels in Losartan groups were significantly different from those of control and Spironolactone groups only on day 1 (P < 0.05).

CONCLUSIONS

Liver regeneration, expected to decrease on day 3, was prolonged and increased even on day 5 despite antiangiogenic effects of Losartan and Spironolactone, which in fact inhibit fibrosis through phospho-Smad2 and increase regeneration. In addition, serum and tissue TGF-B1 levels are not sensitive enough to show active TGF-B1 for the evaluation of regeneration.

Impact of hypertension in liver regeneration in rats

PURPOSE

To determine the impact of hypertension in liver regeneration, in rats by examining gain in liver mass and the replication of hepatocytes and stellate cells.

METHODS

Forty Wistar rats were allocated into two groups of twenty, the control and experiment group. The experiment group animals were submitted to induction of renovascular hypertension. A week later, all the animals underwent a partial hepatectomy. Measurements were taken after 24 hours and seven days, when ten animals in each group were euthanized. Thus, four subgroups were obtained. The livers were excised and sent for histopathological analysis.

RESULTS

The control group had a greater gain in liver mass than the experiment group seven days after partial hepatectomy (p=0.0051). The difference in the activate stellate cell count was not statistically significant following analysis after both 24 hours and seven days (p=1.0). A higher number of dividing hepatocytes was observed in the control group seven days after partial hepatectomy (p=0.0014).

CONCLUSION

In rats, hypertension had no direct influence on stellate cell replication, but led to a delay in liver mass gain and were shown to be a reduction factor on hepatocyte replication seven days after partial hepatectomy.

Advances in the regulation of liver regeneration

Liver regeneration is known to be a process involving highly organized and ordered tissue growth triggered by the loss of liver tissue, and remains a fascinating topic. A large number of genes are involved in this process, and there exists a sequence of stages that results in liver regeneration, while at the same time inhibitors control the size of the regenerated liver. The initiation step is characterized by priming of quiescent hepatocytes by factors such as TNF-α, IL-6 and nitric oxide. The proliferation step is the step during which hepatocytes enter into the cell cycle's G1 phase and are stimulated by complete mitogens including HGF, TGF-α and EGF. Hepatic stimulator substance, glucagon, insulin, TNF-α, IL-1 and IL-6 have also been implicated in regulating the regeneration process. Inhibitors and stop signals of hepatic regeneration are not well known and only limited information is available. Furthermore, the effects of other factors such as VEGF, PDGF, hypothyroidism, proliferating cell nuclear antigen, heat shock proteins, ischemic-reperfusion injury, steatosis and granulocyte colony-stimulating factor on liver regeneration are also systematically reviewed in this article. A tissue engineering approach using isolated hepatocytes for in vitro tissue generation and heterotopic transplantation of liver cells has been established. The use of stem cells might also be very attractive to overcome the limitation of donor liver tissue. Liver-specific differentiation of embryonic, fetal or adult stem cells is currently under investigation.

Co-medications that modulate liver injury and repair influence clinical outcome of acetaminophen-associated liver injury

BACKGROUND & AIMS

Acetaminophen-induced liver injury is the most common cause of acute liver failure in the United States; it occurs inadvertently in approximately half of all cases. Concomitant use of other medications might impact susceptibility to acetaminophen hepatotoxicity. We investigated its association with administration of drugs that have been shown to modulate liver injury and/or repair in preclinical studies.

METHODS

We analyzed data from 6386 cases of acetaminophen-associated liver injury that were defined in the FDA database of reported adverse events. Data reported in the severe adverse event categories of "died" or "life-threatening" (defined as "fatal" cases, n = 2512) were compared with those of "non-fatal" cases (n = 3874). Potential associations between fatality and concomitant use of 9 drug classes were assessed using multiple logistic regression analyses after adjusting for other variables.

RESULTS

Among female subjects, concomitant use of statins, fibrates or nonsteroidal anti-inflammatory drugs was associated with decreased likelihood of fatality, whereas ethanol use was associated with increased likelihood. Among male subjects, concomitant use of statins was associated with decreased likelihood of fatality, whereas concomitant use of sympathetic stimulants or ethanol was associated with increased likelihood. Concomitant use of angiotensin converting enzyme inhibitors or angiotensin receptor II antagonists was associated with decreased likelihood of fatality among younger subjects.

CONCLUSIONS

Concomitant use of medications that have been shown in preclinical studies to modulate liver injury and/or repair influenced acetaminophen hepatotoxicity. Drugs that reduce injury or increase repair are protective, whereas those that exacerbate injury or reduce repair are detrimental.

Are angiotensin II receptor antagonists useful strategies in steatotic and nonsteatotic livers in conditions of partial hepatectomy under ischemia-reperfusion?

We examined whether angiotensin (Ang) II receptor antagonists could be considered a therapeutic strategy in steatotic and nonsteatotic livers in conditions of partial hepatectomy under ischemia-reperfusion (I/R), which is commonly applied in clinical practice to reduce blood loss. We report that Ang II type I receptor (AT1R) antagonist, but not Ang II type II receptor (AT2R) antagonist, increased regeneration in nonsteatotic livers. In the presence of steatosis, both AT1R and AT2R antagonists increased liver regeneration. This effect was stronger when the two were combined. Neither of the Ang II receptor antagonists protected nonsteatotic livers against damage. Only the AT1R antagonist, through nitric oxide inhibition, reduced damage in steatotic livers. The combination of the AT1R and AT2R antagonists in steatotic livers conferred a similar degree of protection to AT1R antagonist alone. Herein, we show that p38 mitogen-activated protein kinase (p38) was a key mechanism in the regeneration induced by the Ang II receptor antagonists in both liver types because when this signaling pathway was inhibited, the beneficial effects of the Ang II receptor antagonists on liver regeneration disappeared, regardless of hepatocyte growth factor or transforming growth factor beta-hepatic levels. In conclusion, in conditions of partial hepatectomy under I/R, the AT1R antagonist for nonsteatotic livers and the AT1R and AT2R antagonists for steatotic livers improved regeneration in the remnant liver through p38 activation. In addition, the combination of the AT1R and AT2R antagonists in steatotic livers led to stronger liver regeneration than either antagonists used separately and also provided the same protection against damage as that afforded by AT1R antagonist alone.

Effect of angiotensin II and bradykinin inhibition in rat reduced-size liver transplantation

This study examined whether angiotensin II (Ang II) blockers [Ang II type I receptor antagonist, Ang II type II receptor antagonist, and angiotensin converting enzyme (ACE) inhibitor] could reduce hepatic injury and improve regeneration in reduced-size orthotopic liver transplantation (ROLT) and whether the beneficial effects of ischemic preconditioning (PC) in ROLT could be explained by changes in Ang II. We show that small liver grafts generated Ang II after ROLT and that this was associated with increased angiotensinogen and ACE messenger RNA expression. Furthermore, inhibition of Ang II did not contribute to PC-induced protection in ROLT. All Ang II blockers reduced hepatic injury, but none of them promoted liver regeneration. Bradykinin (BK) receptor antagonist improved liver regeneration but did not reduce hepatic injury in ROLT. Finally, the combination of Ang II blockers and BK receptor antagonists in ROLT reduced hepatic injury and improved liver regeneration. In conclusion, treatments with either Ang II blockers or BK receptor antagonists cannot, on their own, improve the outcome of ROLT. Although Ang II blockers can reduce hepatic ischemia-reperfusion injury and BK receptor antagonists can promote liver regeneration, neither confers both benefits at the same time. Consequently, it may be of clinical interest to apply both treatments simultaneously.

Cytoskeleton interruption in human hepatoma HepG2 cells induced by ketamine occurs possibly through suppression of calcium mobilization and mitochondrial function

Ketamine is an intravenous anesthetic agent often used for inducing and maintaining anesthesia. Cytoskeletons contribute to the regulation of hepatocyte activity of drug biotransformation. In this study, we attempted to evaluate the effects of ketamine on F-actin and microtubular cytoskeletons in human hepatoma HepG2 cells and its possible molecular mechanisms. Exposure of HepG2 cells to ketamine at Collapse

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MESH Headings

• Adenosine Triphosphate/biosynthesis
• Base Sequence
• Calcium/metabolism
• Cell Line, Tumor
• Cytoskeletal Proteins/genetics
• Cytoskeletal Proteins/metabolism
• Cytoskeleton/drug effects
• Cytoskeleton/metabolism
• DNA Primers
• Humans
• Ketamine/pharmacology
• Microscopy, Confocal
• Mitochondria/physiology
• RNA, Messenger/biosynthesis
• RNA, Messenger/genetics
• Reverse Transcriptase Polymerase Chain Reaction

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Affiliation(s)

Huai-Chia Chang Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, 250 Wu-Xing St., Taipei 110, Taiwan
Ta-Liang Chen
Ruei-Ming Chen

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Angiotensin II regulates liver regeneration via type 1 receptor following partial hepatectomy in mice

Angiotensin II (Ang II) is an important mediator stimulating liver fibrosis after liver injury. However, it is not known whether Ang II plays a role in liver regeneration. Here, we investigate the effects of Ang II type 1 (AT(1)) receptor blocker (ARB), angiotensin-converting enzyme inhibitor (ACEI), systemic infusion of Ang II, and genetic deficiency of the AT(1a) receptor (AT1a-KO) on the hepatic regenerative response to partial hepatectomy (PH) in mice. Administration of ARB (candesartan cilexetil and losartan) or ACEI (enarapril and lisinopril) enhanced 5-bromo-2'-deoxyuridine (BrdU) incorporation into hepatocyte nuclei in remnant liver as well as the restoration of liver weight after PH. Systemic infusion of Ang II (100 ng/kg/min) suppressed the PH-induced BrdU incorporation and the restoration of liver weight. In contrast to Ang II infusion, these hepatic responses to PH were significantly greater in AT1a-KO mice than in wild-type mice. The PH-induced increases in hepatic levels of hepatocyte growth factor (HGF) mRNA and plasma HGF concentrations were greater in candesartan- and enarapril-treated mice or in AT1a-KO mice than in vehicle-treated mice or wild-type mice, respectively, whereas they were less in Ang II-infused mice than in vehicle-infused mice. In contrast to HGF, blockades of the renin-angiotensin system or Ang II infusion produced opposite effects on the PH-induce increases in hepatic transforming growth factor (TGF)-beta 1 mRNA and plasma TGF-beta 1 levels. These studies suggest that Ang II plays a role in the liver regeneration as a suppressor of hepatocyte proliferation via the AT(1) receptor-mediated control of growth factor production.

The renin-angiotensin system and malignancy

The renin-angiotensin system (RAS) is usually associated with its systemic action on cardiovascular homoeostasis. However, recent studies suggest that at a local tissue level, the RAS influences tumour growth. The potential of the RAS as a target for cancer treatment and the suggested underlying mechanisms of its paracrine effects are reviewed here. These include modulation of angiogenesis, cellular proliferation, immune responses and extracellular matrix formation. Knowledge of the RAS has increased dramatically in recent years with the discovery of new enzymes, peptides and feedback mechanisms. The local RAS appears to influence tumour growth and metastases and there is evidence of tissue- and tumour-specific differences. Recent experimental studies provide strong evidence that drugs that inhibit the RAS have the potential to reduce cancer risk or retard tumour growth and metastases. Manipulation of the RAS may, therefore, provide a safe and inexpensive anticancer strategy.