Angiotensin II increases mRNA levels of all TGF-beta isoforms in quiescent and activated rat hepatic stellate cells. Cell Biol Int. 2010;34:969-978. [PMID: 20557291 DOI: 10.1042/cbi20090074]

The relationship between liver enzymes, prehypertension and hypertension in the Azar cohort population

BACKGROUND

The incidence of hypertension (HTN) as a worldwide health problem is rising rapidly. Early identification and management of pre-HTN before HTN development can help reduce its related complications. We evaluated the relationship between liver enzymes levels and pre-HTN/HTN in the Azar cohort population.

METHOD

This cross-sectional study was based on data from the large Azar cohort study and a total of 14,184 participants were included. Pre-HTN and HTN were defined based on the American Heart Association guideline. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT) levels were measured by Pars Azmoon kits. The relationship between pre-HTN/HTN and liver enzyme levels was evaluated by logistic regression.

RESULTS

Of 14,184 participants, 5.7% and 39.6% had pre-HTN and HTN, respectively. In the adjusted model, AST levels of 19-23 IU/l were associated with an elevated risk of pre-HTN (OR [95% CI]: 1.24 [1.04-1.48]). A dose-response increase was seen in pre-HTN in relation to ALT, with the highest OR in the third tertile (1.34 [1.09-1.63]). The odds of pre-HTN also increased with GGT in the third tertile (1.25[1.03-1.52]). In addition, the odds of HTN increased with increased levels of AST, ALT, ALP, and GGT, such that the highest ORs were recorded in the third tertile (OR 1.22 [1.09-1.37], 1.51 [1.35-1.70], 1.19 [1.07-1.34], and 1.68 [1.49-1.89], respectively). Among these enzymes, GGT had the highest OR regarding HTN.

CONCLUSION

This study indicates that AST, ALT, ALP and GGT levels were associated with pre-HTN (except for ALP) and HTN, independent of known risk factors. Hence, it may be possible to use liver enzymes to predict the incidence of pre-HTN and HTN, empowering primary care providers to make the necessary interventions promptly.

Study on the relationship between hepatic fibrosis and epithelial-mesenchymal transition in intrahepatic cells

Hepatic fibrosis is a pathophysiological process, which causes excessive extracellular matrix (ECM) deposition resulting from persistent liver damage. Myofibroblasts are the core cells that produce ECM. It is known that epithelial-mesenchymal transition (EMT) is not a simple transition of cells from the epithelial to mesenchymal state. Instead, it is a process, in which epithelial cells temporarily lose cell polarity, transform into interstitial cell-like morphology, and acquire migration ability. Hepatocytes, hepatic stellate cells, and bile duct cells are the types of intrahepatic cells found in the liver. They can be transformed into myofibroblasts via EMT and play important roles in the development of hepatic fibrosis through a maze of regulations involving various pathways. The aim of the present study is to explore the relationship between the relevant regulatory factors and the EMT signaling pathways in the various intrahepatic cells.

Oxidative Stress in Chronic Liver Disease and Portal Hypertension: Potential of DHA as Nutraceutical

Chronic liver disease constitutes a growing public health issue worldwide, with no safe and effective enough treatment clinical scenarios. The present review provides an overview of the current knowledge regarding advanced chronic liver disease (ACLD), focusing on the major contributors of its pathophysiology: inflammation, oxidative stress, fibrosis and portal hypertension. We present the benefits of supplementation with docosahexaenoic acid triglycerides (TG-DHA) in other health areas as demonstrated experimentally, and explore its potential as a novel nutraceutical approach for the treatment of ACLD and portal hypertension based on published pre-clinical data.

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

Sulforaphane inhibits the activation of hepatic stellate cell by miRNA-423-5p targeting suppressor of fused

Liver fibrosis, a common pathological process in chronic liver diseases, is characterized by excessive accumulation of extracellular matrix proteins and considered as a wound healing response to chronic liver injury. Hepatic stellate cell (HSC) activation plays a key role in liver fibrosis development. Previous studies showed that sulforaphane (SFN) has wide protective effects against tissue injury and inflammation. Accumulating evidence has shown that microRNAs play important roles in the development of hepatic fibrosis, some of which have been identified as potential therapeutic targets. This study was conducted to explore the role of SFN in the suppression of HSC activation. Quantitative real-time PCR showed that HSC miR-423-5p levels were up-regulated during HSC activation and down-regulated after SFN administration. Further, transfection of a miR-423-5p mimic demonstrated that inhibition of HSC activation by SFN required down-regulation of miR-423-5p. We showed that suppressor of fused is the direct target of miR-423-5p. SFN may play a role in inhibiting hepatic fibrosis by downregulating miRNA-423-5p. MiRNA-423-5p may be useful as a therapeutic target for treating hepatic fibrosis.

Targeting Oxidative Stress for the Treatment of Liver Fibrosis

Oxidative stress is a reflection of the imbalance between the production of reactive oxygen species (ROS) and the scavenging capacity of the antioxidant system. Excessive ROS, generated from various endogenous oxidative biochemical enzymes, interferes with the normal function of liver-specific cells and presumably plays a role in the pathogenesis of liver fibrosis. Once exposed to harmful stimuli, Kupffer cells (KC) are the main effectors responsible for the generation of ROS, which consequently affect hepatic stellate cells (HSC) and hepatocytes. ROS-activated HSC undergo a phenotypic switch and deposit an excessive amount of extracellular matrix that alters the normal liver architecture and negatively affects liver function. Additionally, ROS stimulate necrosis and apoptosis of hepatocytes, which causes liver injury and leads to the progression of end-stage liver disease. In this review, we overview the role of ROS in liver fibrosis and discuss the promising therapeutic interventions related to oxidative stress. Most importantly, novel drugs that directly target the molecular pathways responsible for ROS generation, namely, mitochondrial dysfunction inhibitors, endoplasmic reticulum stress inhibitors, NADPH oxidase (NOX) inhibitors, and Toll-like receptor (TLR)-affecting agents, are reviewed in detail. In addition, challenges for targeting oxidative stress in the management of liver fibrosis are discussed.

Balance and circumstance: The renin angiotensin system in wound healing and fibrosis

The tissue renin angiotensin system (tRAS) is a locally-acting master-modulator of tissue homeostasis and regeneration. Through these abilities, it is emerging as an attractive target for therapies aiming to restore tissue homeostasis in conditions associated with disturbed wound healing. The tRAS can be divided into two axes - one being pro-inflammatory and pro-fibrotic and one being anti-inflammatory and anti-fibrotic. However, the division of the axes is fuzzy and imperfect as the axes are codependent and the outcome of tRAS activation is determined by the context. Although the tRAS is a local system it shares its key enzymes, ligands and receptors with the systemic RAS and is consequently also targeted by repurposing of drugs developed against the systemic RAS to manage hypertension. With a focus on the skin we will here discuss the tRAS, its involvement in physiological and pathological wound healing, and the therapeutic aptitude of its targeting to treat chronic wounds and fibrosis.

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) and liver fibrosis: A review

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) are key producer of reactive oxygen species in liver cells. Hepatic stellate cells (HSCs) and Kupffer cells (KCs) are the two key cells for expression of NOX in liver. KCs produce only NOX2, while HSCs produce NOX1, 2, and 4, all of which play essential roles in the process of fibrogenesis within liver. These NOX subtypes are contributed to induction of liver fibrosis by acting through multiple pathways including induction of HSC activation, proliferation, survival and migration, stimulation of hepatocyte apoptosis, enhancement of fibrogenic mediators, and mediation of an inflammatory cascade in both KCs and HSCs.

SIGNIFICANCE

KCs and HSCs are two key cells for production of NOX in liver in relation to the pathology of liver fibrosis. NOX subtypes 1, 2, and 4 are inducers of fibrogenesis in liver. NOX activation favors hepatocyte apoptosis, HSC activation, and KC-mediated inflammatory cascade in liver, all of which are responsible for generation of liver fibrosis.

Role of the renin-angiotensin system in hepatic fibrosis and portal hypertension

The renin-angiotensin system (RAS) is an important regulator of cirrhosis and portal hypertension. As hepatic fibrosis progresses, levels of the RAS components angiotensin (Ang) II, Ang-(1-7), angiotensin-converting enzyme (ACE), and Ang II type 1 receptor (AT1R) are increased. The primary effector Ang II regulates vasoconstriction, sodium homoeostasis, fibrosis, cell proliferation, and inflammation in various diseases, including liver cirrhosis, through the ACE/Ang II/AT1R axis in the classical RAS. The ACE2/Ang-(1-7)/Mas receptor and ACE2/Ang-(1-9)/AT2R axes make up the alternative RAS and promote vasodilation, antigrowth, proapoptotic, and anti-inflammatory effects; thus, countering the effects of the classical RAS axis to reduce hepatic fibrogenesis and portal hypertension. Patients with portal hypertension have been treated with RAS antagonists such as ACE inhibitors, Ang receptor blockers, and aldosterone antagonists, with very promising hemodynamic results. In this review, we examine the RAS, its roles in hepatic fibrosis and portal hypertension, and current therapeutic approaches based on the use of RAS antagonists in patients with portal hypertension.

BML-111 equilibrated ACE-AngII-AT1R and ACE2-Ang-(1-7)-Mas axis to protect hepatic fibrosis in rats

BACKGROUND

It was recently reported Lipoxins (LXs) had protective effects on fibrous diseases, and renin-angiotensin-aldosterone system (RAAS) had played vital and bidirectional roles in hepatic fibrosis. In this paper, a hepatic fibrosis model, induced by carbon tetrachloride (CCL₄) in rats, was used to observe the relations between RAAS and LXs, as well as to further explore the alternative anti-fibrosis mechanisms of LXs.

METHODS

The model was evaluated by morphological observations and biochemical assays. The activities and contents of angiotensin converting enzyme (ACE) and angiotensin converting enzyme 2 (ACE2) were examined through assay kits and ELISA. The expression levels of angiotensinII (AngII), Angiotensin II type 1 receptor (AT1R), angiotensin-(1-7) (Ang-1-7), and Mas were all measured using real time PCR, ELISA, and Western blot.

RESULTS

The model was established successfully and BML-111 significantly ameliorated CCL₄-induced hepatic fibrosis, including reduction inflammation injury, decrease extracellular matrix deposition, and improvement hepatic functions. Furthermore, BML-111 could obviously decrease not only the activities of ACE but also the expression levels of ACE, AngII,and AT1R, which were induced by CCL₄. On the other hand, BML-111 could markedly increase the activities of ACE2, besides the expression levels of ACE2, Ang-(1-7) and Mas. More importantly, BOC-2, a lipoxin A₄ receptor blocker, could reverse all these phenomena.

CONCLUSIONS

Equilibrating ACE-AngII-AT1R axis and ACE2-Ang-(1-7)-Mas axis mediated the protective effect of BML-111 on hepatic fibrosis in rats.

肝星状细胞衰老与增殖、凋亡的关系

肝星状细胞(hepatic stellate cells, HSCs)活化、细胞外基质大量形成是肝纤维化发生发展的关键环节. 许多研究发现, 抑制HSCs增殖、促进HSCs凋亡可阻断肝纤维化进程; 同时研究发现, 促进活化HSCs衰老也可为肝纤维化的防治提供新的策略. 本文就HSCs衰老与增殖、凋亡的关系以及在肝纤维化中的作用相关研究进展予以综述.

Hepatic structural enhancement and insulin resistance amelioration due to AT1 receptor blockade

Over the last decade, the role of renin-angiotensin system (RAS) on the development of obesity and its comorbidities has been extensively addressed. Both circulating and local RAS components are up-regulated in obesity and involved in non-alcoholic fatty liver disease onset. Pharmacological manipulations of RAS are viable strategies to tackle metabolic impairments caused by the excessive body fat mass. Renin inhibitors rescue insulin resistance, but do not have marked effects on hepatic steatosis. However, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARB) yield beneficial hepatic remodeling. ARBs elicit body mass loss and normalize insulin levels, tackling insulin resistance. Also, this drug class increases adiponectin levels, besides countering interleukin-6, tumoral necrosis factor-alpha, and transforming growth factor-beta 1. The latter is essential to prevent from liver fibrosis. When conjugated with peroxisome proliferator-activated receptor (PPAR)-alpha activation, ARB fully rescues fatty liver. These effects might be orchestrated by an indirect up-regulation of MAS receptor due to angiotensin II receptor type 1 (AT1R) blockade. These associations of ARB with PPAR activation and ACE2-angiotensin (ANG) (1-7)-MAS receptor axis deserve a better understanding. This editorial provides a brief overview of the current knowledge regarding AT1R blockade effects on sensitivity to insulin and hepatic structural alterations as well as the intersections of AT1R blockade with peroxisome proliferator-activated receptor activation and ACE2-ANG (1-7) - MAS receptor axis.

Epithelial-mesenchymal transition in liver fibrosis

Liver fibrosis is the result of a sustained wound healing response to sustained chronic liver injury, which includes viral, alcoholic and autoimmune hepatitis. Hepatic regeneration is the dominant outcome of liver damage. The outcomes of successful repair are the replacement of dead epithelial cells with healthy epithelial cells, and reconstruction of the normal hepatic structure and function. Prevention of the development of epithelial-mesenchymal transition (EMT) may control and even reverse liver fibrosis. EMT is a critical process for an epithelial cell to undergo a conversion to a mesenchymal phenotype, and is believed to be an inflammation-induced response, which may have a central role in liver fibrosis. The origin of fibrogenic cells in liver fibrosis remains controversial. Numerous studies have investigated the origin of all fibrogenic cells within the liver and the mechanism of the signaling pathways that lead to the activation of EMT programs during numerous chronic liver diseases. The present study aimed to summarize the evidence to explain the possible role of EMT in liver fibrosis.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

p38 MAPK-mediated proliferation-promoting effect of angiotensin Ⅱ on hepatic stellate cells

AIM: To elucidate the signal transduction mechanism by which angiotensin Ⅱ promotes the proliferation of hepatic stellate cells (HSCs).

METHODS: The influence of angiotensin Ⅱ on p38 MAPK expression in primarily cultured HSCs was detected by Western blot. The p38 MAPK inhibitor SB203580 was incubated with HSCs to observe its effect on angiotensin Ⅱ-induced transforming growth factor-β (TGF-β) secretion and collagen Ⅰ and Ⅳ expression.

RESULTS: Western blot analysis showed that, compared to the normal saline group, treatment with angiotensin Ⅱ (10^-8, 10^-7, 10^-6 moL/L) for 24 h significantly induced p38 MAPK expression (0.45 ± 0.052, 0.61 ± 0.026, 0.87 ± 0.032 vs 0.27 ± 0.020, all P < 0.0005). Compared to the normal saline group, treatment with angiotensin Ⅱ (10^-6 moL/L) for 24 h significantly induced HSC proliferation (0.1073 ± 0.0093 vs 0.5233 ± 0.0240, P < 0.0005), promoted incretion of TGF-β1 (10.6 ng/mL ± 0.98 ng/mL vs 100.8 ng/mL ± 3.67 ng/mL, P < 0.0005), and increased the expression of collagen α1(Ⅰ) and α1(Ⅳ) (1.13 ± 0.053 vs3.74 ± 0.047; 1.35 ± 0.035 vs 4.07 ± 0.072; both P < 0.0005). Pre-treatment with SB203580 significantly attenuated the effect of angiotensin Ⅱ on the above parameters in HSCs (0.2033 ± 0.0176 vs 0.5233 ± 0.0240; 21.07 ng/mL ± 2.08 ng/mL vs 100.8 ng/mL ± 3.67 ng/mL; 1.16 ± 0.024 vs 3.74 ± 0.047; 1.56 ± 0.075 vs 4.07 ± 0.072, all P < 0.0005).

CONCLUSION: Angiotensin Ⅱ induces HSC proliferation and increases expression of TGF-β1 via the p38 MAPK pathway.

Salvianolic Acid B Attenuates Rat Hepatic Fibrosis via Downregulating Angiotensin II Signaling

The renin-angiotensin system (RAS) plays an important role in hepatic fibrosis. Salvianolic acid B (Sal B), one of the water-soluble components from Radix Salviae miltiorrhizae, has been used to treat hepatic fibrosis, but it is still not clear whether the effect of Sal B is related to angiotensin II (Ang II) signaling pathway. In the present study, we studied Sal B effect on rat liver fibrosis and Ang-II related signaling mediators in dimethylnitrosamine-(DMN-) induced rat fibrotic model in vivo and Ang-II stimulated hepatic stellate cells (HSCs) in vitro, with perindopril or losartan as control drug, respectively. The results showed that Sal B and perindopril inhibited rat hepatic fibrosis and reduced expression of Ang II receptor type 1 (AT1R) and ERK activation in fibrotic liver. Sal B and losartan also inhibited Ang II-stimulated HSC activation including cell proliferation and expression of type I collagen I (Col-I) and α-smooth muscle actin (α-SMA) production in vitro, reduced the gene expression of transforming growth factor beta (TGF-β), and downregulated AT1R expression and ERK and c-Jun phosphorylation. In conclusion, our results indicate that Sal B may exert an antihepatic fibrosis effect via downregulating Ang II signaling in HSC activation.

Effect of valsartan on the pathological progression of hepatic fibrosis in rats with type 2 diabetes

Currently there is no effective treatment for nonalcoholic fatty liver disease (NAFLD), especially hepatic fibrosis induced by type 2 diabetes. Valsartan maybe has beneficial effect on the liver disease. The aim of the present study was to investigate the effect of valsartan on the pathological progression of hepatic fibrosis in rats with type 2 diabetes. An animal model of hepatic fibrosis with type 2 diabetes was developed using a high-sucrose, high-fat diet and low-dose streptozotocin. Valsartan (15 mg/kg/day, i.g.) was orally administered for four months. The livers were removed to make hematoxylin-eosin (HE) staining and Picric acid-Sirius red staining, and immunohistochemistry staining of α-smooth-muscle-actin (α-SMA), transforming growth factor β1 (TGF-β1), tumor necrosis factor (TNF-α) and monocyte chemotactic protein-1 (MCP-1). Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was performed to detect hepatocyte apoptosis. The liver mitochondria were isolated to measure the mitochondrial respiratory function. The results showed that valsartan significantly alleviated the lesion of hepatic steatosis and hepatic fibrosis by HE staining and Picric acid-Sirius red staining. Immunohistochemical staining suggested that the expression of α-SMA, TGF-β1, TNF-α and MCP-1 in liver tissue of diabetic rats was markedly reduced by valsartan. TUNEL staining showed that there were fewer TUNEL-positive apoptotic hepatocytes in valsartan group. In addition, valsartan restored the injured hepatic mitochondrial respiratory function. The findings demonstrated that valsartan prevented the pathological progression of hepatic fibrosis in type 2 diabetic rats, correlated with reducing α-SMA, TGF-β1, TNF-α and MCP-1 expression, also anti-apoptosis and mitochondria-protective potential.

Modulation of TGFβ(2) and dopamine by PKC in retinal Müller cells of guinea pig myopic eye

AIM

To investigate the effect of protein kinase C (PKC) on transforming growth factor-β(2) (TGFβ(2)) and dopamine in retinal Müller cells of guinea pig myopic eye.

METHODS

Myopia was induced by translucent goggles in guinea pig, whose retinal Müller cells were cultured using the enzyme-digesting method. Retinal Müller cells were divided into 5 groups: normal control, myopia, myopia plus GF109203X, myopia plus PMA, myopia plus DMSO. PKC activities were detected by the non-radioactive methods. TGFβ(2) and tyrosine hydroxylase (TH) proteins were analyzed by Western Blotting in retinal Müller cells. Dopamine was determined by the high-performance liquid chromatography-electrochemical detection in suspensions.

RESULTS

After 14 days deprived, the occluded eyes became myopic with ocular axle elongating. Müller cells of guinea pigs were obtained using enzyme digestion. Compared with normal control group, the increase in PKC activity and the up-regulation in TGFβ(2) expression were found in retinal Müller cells of myopic eyes, with the decrease of TH and dopamine content (P<0.05). After PKC activated by PMA, TGFβ(2) and TH content were up-regulated with the increase of dopamine content (P<0.05). While the PKC activities was inhibited by GF109203X, proteins of TGFβ(2) and TH were down-regulated in the myopic eyes, with the decrease of dopamine content (P<0.05).

CONCLUSION

TGFβ(2) and dopamine are modulated by PKC in Müller cells of the myopic eyes in guinea pig.