Telmisartan plus propranolol improves liver fibrosis and bile duct proliferation in the PSC-like Abcb4-/- mouse model

Neuroimmunomodulation of adrenoblockers during liver cirrhosis: modulation of hepatic stellate cell activity

The sympathetic nervous system and the immune system are responsible for producing neurotransmitters and cytokines that interact by binding to receptors; due to this, there is communication between these systems. Liver immune cells and nerve fibres are systematically distributed in the liver, and the partial overlap of both patterns may favour interactions between certain elements. Dendritic cells are attached to fibroblasts, and nerve fibres are connected via the dendritic cell-fibroblast complex. Receptors for most neuroactive substances, such as catecholamines, have been discovered on dendritic cells. The sympathetic nervous system regulates hepatic fibrosis through sympathetic fibres and adrenaline from the adrenal glands through the blood. When there is liver damage, the sympathetic nervous system is activated locally and systemically through proinflammatory cytokines that induce the production of epinephrine and norepinephrine. These neurotransmitters bind to cells through α-adrenergic receptors, triggering a cellular response that secretes inflammatory factors that stimulate and activate hepatic stellate cells. Hepatic stellate cells are key in the fibrotic process. They initiate the overproduction of extracellular matrix components in an active state that progresses from fibrosis to liver cirrhosis. It has also been shown that they can be directly activated by norepinephrine. Alpha and beta adrenoblockers, such as carvedilol, prazosin, and doxazosin, have recently been used to reverse CCl₄-induced liver cirrhosis in rodent and murine models.KEY MESSAGESNeurotransmitters from the sympathetic nervous system activate and increase the proliferation of hepatic stellate cells.Hepatic fibrosis and cirrhosis treatment might depend on neurotransmitter and hepatic nervous system regulation.Strategies to reduce hepatic stellate cell activation and fibrosis are based on experimentation with α-adrenoblockers.

Telmisartan Alleviates Alzheimer's Disease-Related Neuropathologies and Cognitive Impairments

BACKGROUND

Alzheimer's disease (AD) is the most common type of neurodegenerative disorder. There are few effective medications for halting the progression of AD. Telmisartan (TEL) is a widely used anti-hypertensive drug approved by FDA. Aside from treating hypertension, TEL has been revealed to provide protection against AD. However, the underlying mechanisms remain unclear.

OBJECTIVE

To investigate the mechanisms underlying the beneficial effects of TEL against AD.

METHODS

Eight-month-old APP/PS1 mice were administered with 5 mg/kg TEL once per day for 4 successive months. Nesting test, Y-maze test, and Morris water maze test were employed to assess the cognitive and executive functions. Neuronal and synaptic markers, Aβ pathology, neuroinflammation, and oxidative stress in the brains were measured. Specifically, components involved in amyloid-β (Aβ) production and degradation pathway were analyzed to explore the mechanisms underlying the therapeutic effect of TEL against Aβ pathology. The primary microglia were used to uncover the mechanisms underlying the anti-inflammatory effects of TEL in AD. Additionally, the preventive effect of TEL against AD were investigated using 4-month-old APP/PS1 mice.

RESULTS

TEL treatment ameliorated cognitive and executive impairments, neuronal and synaptic injury, Aβ pathology, neuroinflammation, and oxidative stress in APP/PS1 mice. The favorable effects of TEL on Aβ pathology were achieved by inhibiting enzymatic Aβ production and facilitating enzymatic and autophagic Aβ degradation. Meanwhile, the anti-inflammatory effects of TEL were accomplished via microglial PPARγ/NLRP3 pathway. The administration of TEL prior to symptom onset prevented AD-related cognitive decline and neuropathologies.

CONCLUSION

TEL represents a promising agent for AD prevention and treatment.

Endothelin Receptor-A Inhibition Decreases Ductular Reaction, Liver Fibrosis, and Angiogenesis in a Model of Cholangitis

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) leads to ductular reaction and fibrosis and is complicated by vascular dysfunction. Cholangiocyte and endothelial cell crosstalk modulates their proliferation in cholestatic models. Endothelin (ET)-1 and ET-2 bind to their receptor, ET-A, and cholangiocytes are a key source of ET-1 after bile duct ligation. We aimed to evaluate the therapeutic potential of ET-A inhibition in PSC and biliary-endothelial crosstalk mediated by this pathway.

METHODS

Wild-type and multidrug resistance 2 knockout (Mdr2-/-) mice at 12 weeks of age were treated with vehicle or Ambrisentan (ET-A antagonist) for 1 week by daily intraperitoneal injections. Human control and PSC samples were used.

RESULTS

Mdr2-/- mice at 4, 8, and 12 weeks displayed angiogenesis that peaked at 12 weeks. Mdr2-/- mice at 12 weeks had enhanced biliary ET-1/ET-2/ET-A expression and secretion, whereas human PSC had enhanced ET-1/ET-A expression and secretion. Ambrisentan reduced biliary damage, immune cell infiltration, and fibrosis in Mdr2-/- mice. Mdr2-/- mice had squamous cholangiocytes with blunted microvilli and dilated arterioles lacking cilia; however, Ambrisentan reversed these alterations. Ambrisentan decreased cholangiocyte expression of pro-angiogenic factors, specifically midkine, through the regulation of cFOS. In vitro, ET-1/ET-A caused cholangiocyte senescence, endothelial cell angiogenesis, and macrophage inflammation. In vitro, human PSC cholangiocyte supernatants increased endothelial cell migration, which was blocked with Ambrisentan treatment.

CONCLUSIONS

ET-A inhibition reduced biliary and liver damage in Mdr2-/- mice. ET-A promotes biliary angiocrine signaling that may, in turn, enhance angiogenesis. Targeting ET-A may prove therapeutic for PSC, specifically patients displaying vascular dysfunction.

Telmisartan relieves liver fibrosis and portal hypertension by improving vascular remodeling and sinusoidal dysfunction

BACKGROUNDS

Telmisartan(TEL) has demonstrated anti-fibrotic and blood pressure lowering effect in various diseases. In this study, we aimed to explore the beneficial effects of TEL on portal hypertension(PHT).

METHODS

Two models of cirrhosis-induced PHT were involved including carbon tetrachloride injection(CCl4) and bile duct ligation(BDL). Rats were orally gavaged with TEL for 4 weeks. After that, the portal pressure(PP) was determined, and liver and mesenteric tissue specimens were collected to evaluate inflammatory response, liver fibrosis, vascular remodeling, angiogenesis, etc. RESULTS: In CCl4 PHT models, TEL decreased PP significantly from 12.79 ± 2.92 to 6.91 ± 1.19 mmHg(p < 0.05). In inflammatory response, hepatic expressions of interleukin(IL)-6, lipopolysaccharide(LPS), and tumor necrosis factor-α(TNF-α) were significantly decreased after TEL treatment. Moreover, in the liver fibrotic area, the expressions of α-smooth muscle actin(α-SMA), collagen1a1(Col1a1), desmin, transforming growth factor-β(TGF-β), and hydroxyproline, and serum hyaluronic acid were significantly decreased after TEL treatment. Additionally, the expressions of von Willebrand factor(vWF), vascular endothelial growth factor(VEGF) and platelet-derived growth factor-β(PDGF-β), matrix metallopeptidase(MMP)-2, and MMP-9 were ameliorated in liver sinusoid, while the expressions of MMP-2 and vWF were reduced in mesenteric arteries after TEL treatment. Meanwhile, TEL treatment up-regulated the hepatic expressions of an anti-fibrotic factor Krüppel-like factor-4(KLF-4) and its downstream endothelial nitric oxide synthase(eNOS) in rats with PHT. The performance of TEL in BDL model was similar but slightly weaker.

CONCLUSIONS

TEL ameliorated the cirrhosis-induced PHT by reducing liver fibrosis, inflammation responses, angiogenesis, and vascular remodeling. Collectively, KLF-4 and eNOS were the possible molecular targets for the management of cirrhosis-associated PHT.

Treatment of glaucoma by prostaglandin agonists and beta-blockers in combination directly reduces pro-fibrotic gene expression in trabecular meshwork

Prostaglandin analogues (PG), beta-blockers (BB) or their combination (PG+BB) are used primarily to reduce the intraocular pressure (IOP) pathologically associated with glaucoma. Since, fibrosis of the trabecular meshwork (TM) is a major aetiological factor in glaucoma, we studied the effect of these drugs on fibrosis-associated gene expression in TM of primary glaucoma patients. In the present study, TM and iris of primary open-angle (n = 32) and angle-closure (n = 37) glaucoma patients were obtained surgically during trabeculectomy and categorized based on the type of IOP-lowering medications use as PG, BB or PG+BB. mRNA expression of pro-fibrotic and anti-fibrotic genes was quantified using qPCR in these tissues. The gene expression levels of pro-fibrotic genes were significantly lower in PG+BB as compared to other groups. These observations and underlying signalling validated in vitro in human TM cells also showed reduced fibrotic gene and protein expression levels following PG+BB treatment. In conclusion, it is observed that PG+BB combination rather than their lone use renders a reduced fibrotic status in TM. This further suggests that IOP-lowering medications, in combination, would also modulate fibrosis-associated molecular changes in the TM, which may be beneficial for maintaining aqueous out-flow mechanisms over the clinical treatment duration.

Biliary epithelium: A neuroendocrine compartment in cholestatic liver disease

Hepatic fibrosis is characterized by abnormal accumulation of extracellular matrix (ECM) that can lead to ductopenia, cirrhosis, and even malignant transformation. In this review, we examine cholestatic liver diseases characterized by extensive biliary fibrosis such as primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC), polycystic liver disease (PLD), and MDR2-/- and BDL mouse models. Following biliary injury, cholangiocytes, the epithelial cells that line the bile ducts, become reactive and adopt a neuroendocrine phenotype in which they secrete and respond to neurohormones and neuropeptides in an autocrine and paracrine fashion. Emerging evidence indicates that cholangiocytes influence and respond to changes in the ECM and stromal cells in the microenvironment. For example, activated myofibroblasts and hepatic stellate cells are major drivers of collagen deposition and biliary fibrosis. Additionally, the liver is richly innervated with adrenergic, cholinergic, and peptidergic fibers that release neurohormones and peptides to maintain homeostasis and can be deranged in disease states. This review summarizes how cholangiocytes interact with their surrounding environment, with particular focus on how autonomic and sensory regulation affects fibrotic pathophysiology.

Propranolol prevents liver cirrhosis by inhibiting hepatic stellate cell activation mediated by the PDGFR/Akt pathway

Propranolol is known to reduce portal pressure by decreasing blood flow to the splanchnic circulation and the liver. However, it is unknown if propranolol improves fibrogenesis and sinusoidal remodeling in the cirrhotic liver. The aim of this study was to investigate the therapeutic effects of propranolol on carbon tetrachloride (CCl₄)-induced liver fibrosis in a mouse model and the intrinsic mechanisms underlying those effects. In this study, a hepatic cirrhosis mouse model was induced by CCl₄ administration for 6 weeks. Propranolol was simultaneously administered orally in the experimental group. Liver tissue and blood samples were collected for histological and molecular analyses. LX-2 cells induced by platelet-derived growth factor-BB (PDGF-BB) were used to evaluate the anti-fibrogenic effect of propranolol in vitro. The results showed that treatment of mice with CCl₄ induced hepatic fibrosis, as evidenced by inflammatory cell infiltration, collagen deposition and abnormal vascular formation in the liver tissue. All these changes were significantly attenuated by propranolol treatment. Furthermore, we also found that propranolol inhibited PDGF-BB-induced hepatic stellate cell migration, fibrogenesis, and PDGFR/Akt phosphorylation. Taken together, propranolol might prevent CCl₄-induced liver injury and fibrosis at least partially through inhibiting the PDGF-BB-induced PDGFR/Akt pathway. The anti-fibrogenic effect of propranolol may support its status as a first-line treatment in patients with chronic liver disease.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

The role of renin-angiotensin system modulation on treatment and prevention of liver diseases

The renin-angiotensin system (RAS) is now recognized as an important modulator of body metabolic processes. The discovery of angiotensin-converting enzyme 2 (ACE2) has renewed interest in the potential therapeutic role of RAS modulation. Recent studies have pointed out the importance of the local balance between ACE/Ang-II/AT1 and ACE2/Ang-(1-7)/Mas arms to avoid liver metabolic diseases. Furthermore, non-alcoholic fatty liver disease is an increasing health problem that includes a spectrum of hepatic steatosis, steatohepatitis and fibrosis. Some new studies revealed that RAS imbalance appears to promote hepatic fibrogenesis; while the activation of ACE2/Ang-(1-7)/Mas counter-regulatory axis is able to prevent liver injuries. In this context, the aim of the present review is to discuss the importance of RAS in the development and prevention of liver disease. AT1 receptor activation by Ang II induces hepatic stellate cell contraction and proliferation, causes oxidative stress, endothelial dysfunction, cell growth and inflammation. In addition, both AT1 blocker administration and ACE inhibitors lead to a reduction in inflammation and improvement of hepatic fibrosis. Conversely, Ang-(1-7) infusion reduces fibrosis and proliferation mainly by suppression of hepatic stellate cell activation; Mas receptor antagonism aggravates liver fibrosis and severe liver steatosis. In conclusion, the use of ACE/Ang II/AT1 axis inhibitors associated with ACE2/Ang(1-7)/Mas axis activation is a promising new strategy serving as a novel therapeutic regimen to prevent and treat chronic liver diseases as well as acute liver injury.