Protective effects of erythropoietin on cirrhotic cardiomyopathy in rats

Therapies for Cirrhotic Cardiomyopathy: Current Perspectives and Future Possibilities

Cirrhotic cardiomyopathy (CCM) is defined as cardiac dysfunction associated with cirrhosis in the absence of pre-existing heart disease. CCM manifests as the enlargement of cardiac chambers, attenuated systolic and diastolic contractile responses to stress stimuli, and repolarization changes. CCM significantly contributes to mortality and morbidity in patients who undergo liver transplantation and contributes to the pathogenesis of hepatorenal syndrome/acute kidney injury. There is currently no specific treatment. The traditional management for non-cirrhotic cardiomyopathies, such as vasodilators or diuretics, is not applicable because an important feature of cirrhosis is decreased systemic vascular resistance; therefore, vasodilators further worsen the peripheral vasodilatation and hypotension. Long-term diuretic use may cause electrolyte imbalances and potentially renal injury. The heart of the cirrhotic patient is insensitive to cardiac glycosides. Therefore, these types of medications are not useful in patients with CCM. Exploring the therapeutic strategies of CCM is of the utmost importance. The present review summarizes the possible treatment of CCM. We detail the current status of non-selective beta-blockers (NSBBs) in the management of cirrhotic patients and discuss the controversies surrounding NSBBs in clinical practice. Other possible therapeutic agents include drugs with antioxidant, anti-inflammatory, and anti-apoptotic functions; such effects may have potential clinical application. These drugs currently are mainly based on animal studies and include statins, taurine, spermidine, galectin inhibitors, albumin, and direct antioxidants. We conclude with speculations on the future research directions in CCM treatment.

Oxidative Mechanisms and Cardiovascular Abnormalities of Cirrhosis and Portal Hypertension

In patients with portal hypertension, there are many complications including cardiovascular abnormalities, hepatorenal syndrome, ascites, variceal bleeding, and hepatic encephalopathy. The underlying mechanisms are not yet completely clarified. It is well known that portal hypertension causes mesenteric congestion which produces reactive oxygen species (ROS). ROS has been associated with intestinal mucosal injury, increased intestinal permeability, enhanced gut bacterial overgrowth, and translocation; all these changes result in increased endotoxin and inflammation. Portal hypertension also results in the development of collateral circulation and reduces liver mass resulting in an overall increase in endotoxin/bacteria bypassing detoxication and immune clearance in the liver. Endotoxemia can in turn aggravate oxidative stress and inflammation, leading to a cycle of gut barrier dysfunction → endotoxemia → organ injury. The phenotype of cardiovascular abnormalities includes hyperdynamic circulation and cirrhotic cardiomyopathy. Oxidative stress is often accompanied by inflammation; thus, blocking oxidative stress can minimize the systemic inflammatory response and alleviate the severity of cardiovascular diseases. The present review aims to elucidate the role of oxidative stress in cirrhosis-associated cardiovascular abnormalities and discusses possible therapeutic effects of antioxidants on cardiovascular complications of cirrhosis including hyperdynamic circulation, cirrhotic cardiomyopathy, and hepatorenal syndrome.

Role of Galectin in Cardiovascular Conditions including Cirrhotic Cardiomyopathy

Abnormal cardiac function in the setting of cirrhosis and in the absence of a primary cardiac disease is known as cirrhotic cardiomyopathy. The pathogenesis of cirrhotic cardiomyopathy is multifactorial but broadly is comprised of two pathways. The first is due to cirrhosis and synthetic liver failure with abnormal structure and function of many substances, including proteins, lipids, hormones, and carbohydrates such as lectins. The second is due to portal hypertension which invariably accompanies cirrhosis. Portal hypertension leads to a leaky, congested gut with resultant endotoxemia and systemic inflammation. This inflammatory phenotype comprises oxidative stress, cellular apoptosis, and inflammatory cell infiltration. Galectins exert all these pro-inflammatory mechanisms across many different tissues and organs, including the heart. Effective therapies for improving cardiac function in patients with cirrhosis are not available. Conventional strategies for other noncirrhotic heart diseases, including vasodilators, are not feasible because of the significant baseline vasodilation in cirrhotic patients. Therefore, exploring new treatment modalities for cirrhotic cardiomyopathy is of great importance. Galectin-3 inhibitors such as modified citrus pectin, N-acetyllactosamine, TD139 and GB0139 exert anti-apoptotic, anti-oxidative and anti-inflammatory effects and thus have potential therapeutic interest. This review briefly summarizes the physiological and pathophysiological role of galectin and specifically examines its role in cardiac disease processes. We present a more detailed discussion of galectin in cardiovascular complications of cirrhosis, particularly cirrhotic cardiomyopathy. Finally, therapeutic studies of galectin-3 inhibitors in cirrhotic cardiomyopathy are reviewed.

Dysregulated Calcium Handling in Cirrhotic Cardiomyopathy

Cirrhotic cardiomyopathy is a syndrome of blunted cardiac systolic and diastolic function in patients with cirrhosis. However, the mechanisms remain incompletely known. Since contractility and relaxation depend on cardiomyocyte calcium transients, any factors that impact cardiac contractile and relaxation functions act eventually through calcium transients. In addition, calcium transients play an important role in cardiac arrhythmias. The present review summarizes the calcium handling system and its role in cardiac function in cirrhotic cardiomyopathy and its mechanisms. The calcium handling system includes calcium channels on the sarcolemmal plasma membrane of cardiomyocytes, the intracellular calcium-regulatory apparatus, and pertinent proteins in the cytosol. L-type calcium channels, the main calcium channel in the plasma membrane of cardiomyocytes, are decreased in the cirrhotic heart, and the calcium current is decreased during the action potential both at baseline and under stimulation of beta-adrenergic receptors, which reduces the signal to calcium-induced calcium release. The study of sarcomere length fluctuations and calcium transients demonstrated that calcium leakage exists in cirrhotic cardiomyocytes, which decreases the amount of calcium storage in the sarcoplasmic reticulum (SR). The decreased storage of calcium in the SR underlies the reduced calcium released from the SR, which results in decreased cardiac contractility. Based on studies of heart failure with non-cirrhotic cardiomyopathy, it is believed that the calcium leakage is due to the destabilization of interdomain interactions (dispersion) of ryanodine receptors (RyRs). A similar dispersion of RyRs may also play an important role in reduced contractility. Multiple defects in calcium handling thus contribute to the pathogenesis of cirrhotic cardiomyopathy.

Galectin-3 inhibits cardiac contractility via a TNFα-dependent mechanism in cirrhotic rats

Background/Aims

Galectin-3 plays a key pathogenic role in cardiac hypertrophy and heart failure. The present study aimed to investigate the effects of galectin-3 on cardiomyopathy – related factors and cardiac contractility in a rat model of cirrhotic cardiomyopathy.

Methods

Rats were divided into two sets, one for a functional study, the other for cardiac contractile-related protein evaluation. There were four groups in each set: sham operated and sham plus N-acetyllactosamine (N-Lac, a galectin-3 inhibitor; 5 mg/kg); bile duct ligated (BDL) and BDL plus N-Lac. Four weeks after surgery, ventricular level of galectin-3, collagen I and III ratio, tumor necrosis factor alpha (TNFα), and brain natriuretic peptide (BNP) were measured either by Western blots or immunohistochemistry or enzyme-linked immunosorbent assay. Blood pressure was measured by polygraph recorder. Cardiomyocyte contractility was measured by inverted microscopy.

Results

Galectin-3 and collagen I/III ratio were significantly increased in cirrhotic hearts. TNFα and BNP were significantly increased in BDL serum and heart compared with sham controls. Galectin-3 inhibitor significantly decreased galectin-3, TNFα, and BNP in cirrhotic hearts but not in sham controls. N-Lac also significantly improved the blood pressure, and systolic and diastolic cardiomyocyte contractility in cirrhotic rats but had no effect on sham controls.

Conclusion

Increased galectin-3 in the cirrhotic heart significantly inhibited contractility via TNFα. Inhibition of galectin-3 decreased the cardiac content of TNFα and BNP and reversed the decreased blood pressure and depressed contractility in the cirrhotic heart. Galectin-3 appears to play a pathogenic role in cirrhotic cardiomyopathy.

Pathogenic Mechanisms Underlying Cirrhotic Cardiomyopathy

Cardiac dysfunction associated with cirrhosis in the absence of preexisting heart disease is a condition known as cirrhotic cardiomyopathy (CCM). Cardiac abnormalities consist of enlargement of cardiac chambers, attenuated systolic and diastolic contractile responses to stress stimuli, and repolarization changes. CCM may contribute to cardiovascular morbidity and mortality after liver transplantation and other major surgeries, and also to the pathogenesis of hepatorenal syndrome. The underlying mechanisms of CCM are poorly understood and as such medical therapy is an area of unmet medical need. The present review focuses on the pathogenic mechanisms responsible for development of CCM. The two major concurrent mechanistic pathways are the inflammatory phenotype due to portal hypertension, and protein/lipid synthetic/metabolic defects due to cirrhosis and liver insufficiency. The inflammatory phenotype arises from intestinal congestion due to portal hypertension, resulting in bacteria/endotoxin translocation into the systemic circulation. The cytokine storm associated with inflammation, particularly TNFα acting via NFκB depresses cardiac function. They also stimulate two evanescent gases, nitric oxide and carbon monoxide which produce cardiodepression by cGMP. Inflammation also stimulates the endocannabinoid CB-1 pathway. These systems inhibit the stimulatory beta-adrenergic contractile pathway. The liver insufficiency of cirrhosis is associated with defective synthesis or metabolism of several substances including proteins and lipids/lipoproteins. The protein defects including titin and collagen contribute to diastolic dysfunction. Other protein abnormalities such as a switch of myosin heavy chain isoforms result in systolic dysfunction. Lipid biochemical changes at the cardiac sarcolemmal plasma membrane result in increased cholesterol:phospholipid ratio and decreased membrane fluidity. Final common pathway changes involve abnormal cardiomyocyte intracellular ion kinetics, particularly calcium. In conclusion, cirrhotic cardiomyopathy is caused by two pathways of cellular and molecular dysfunction/damage due to hepatic insufficiency and portal hypertension.

Protective Effects of Spermidine Against Cirrhotic Cardiomyopathy in Bile Duct-Ligated Rats

Cirrhotic cardiomyopathy is a critical factor that causes morbidity and mortality in crucial conditions such as liver transplantation. In animal model, the common pathophysiologic mechanisms of cirrhotic cardiomyopathy are similar to those associated with bile duct ligation (BDL). Overproduction of inflammatory and oxidant markers plays a crucial role in cirrhotic cardiomyopathy. Spermidine, a multifunctional polyamine, is known for its antioxidant and anti-inflammatory effects. In this study, we investigated the effects of spermidine on development of cirrhotic cardiomyopathy in BDL rats. Rats were randomly housed in 6 groups. Except the normal and sham groups, BDL was performed for all the control and spermidine groups. Seven days after operation, 3 different doses of spermidine (5, 10 and 50 mg/kg) were administrated until day 28, in spermidine groups. At the end of the fourth week, the electrocardiography (ECG) and papillary muscle isolation were performed. The serum level of tumor necrosis factor-a (TNF-α), interleukin-1β (IL-1β), and IL-10 and cardiac level of superoxide dismutase, glutathione (GSH). and malondialdehyde (MDA) were assessed. Furthermore, the nuclear factor-κB (NF-κB) expression was assessed by western blot. Cardiac histopathological changes were monitored. The serum levels of magnesium (Mg) and potassium (K) were investigated. Control group, exhibited exaggerated signs of cirrhotic cardiomyopathy in comparison with the sham group. Co-administration of spermidine at the dose of 10 mg/kg in BDL rats significantly improved the cardiac condition, reduced the inflammatory mediators, and increased antioxidant enzymes. In addition, the histopathologic findings were in accordance with the other results of the study. Besides, there was no significant alteration in serum levels of Mg and K. This study demonstrates that spermidine at the dose of 10 mg/kg significantly improved the cirrhotic cardiomyopathy in BDL model in rats.

Advances in cirrhotic cardiomyopathy

PURPOSE OF REVIEW

Cirrhotic cardiomyopathy (CCM) is a well-recognized entity. When patients with CCM encounter challenges such as liver transplantation, overt cardiac dysfunction manifests, leading to morbidity and mortality. Although revised diagnostic criteria for CCM have recently been proposed, these still need to be validated.

RECENT FINDINGS

Previous reviews have summarized the mechanisms of CCM, such as abnormalities of the β-adrenergic pathway, cardiac plasma membrane biophysical and biochemical properties, and electrophysiological changes. Cardiomyocyte apoptosis, inflammation, and oxidative stress also play important roles. The present review details further mechanisms of CCM, which include myosin heavy chain isoform shifts and abnormalities in cellular calcium transients. Additionally, we review recent studies on therapeutic strategies. Recent work underscores the importance of CCM in the natural history of the immediate and medium-term postoperative period after liver transplantation. Appropriate management strategies for CCM remain the area of greatest unmet need, requiring much further research.

SUMMARY

CCM is a clinically relevant syndrome affecting patients with cirrhosis, leading to increased morbidity and mortality. New diagnostic criteria have been recently proposed by an expert working group. The pathogenic mechanisms remain incompletely clarified and optimal management strategies need much further study.

Preconditioning and anti-apoptotic effects of Metformin and Cyclosporine-A in an isolated bile duct-ligated rat heart

Despite all previous studies relating to the mechanism of cirrhotic cardiomyopathy (CCM), the role of cirrhosis on Ischemic Preconditioning (IPC) has not yet been explored. The present study strives to assess the cardioprotective role of IPC in bile duct ligated (BDL) rats as well as the cardioprotective role of Cyclosporin-A (CsA) and Metformin (Met) in CCM. Cirrhosis was induced by bile duct ligation (BDL). Rats' hearts were isolated and attached to a Langendorff Apparatus. The pharmacological preconditioning with Met and CsA was done before the main ischemia. Myocardial infarct size, hemodynamic and electrophysiological parameters, biochemical markers, and apoptotic indices were determined at the end of the experiment. Infarct size, apoptotic indices, arrhythmia score, and incidence of VF decreased significantly in the IPC group in comparison with the I/R group. These significant decreases were abolished in the IPC (BDL) group. Met significantly decreased the infarct size and apoptotic indices compared with I/R (BDL) and normal groups, while CsA led to similar decreases except in the level of caspase-3 and -8. Met and CsA decreased and increased the arrhythmia score and incidence of VF in the BDL groups, respectively. Functional recovery indices decreased in the I/R (BDL) and IPC (BDL) groups. Met improved these parameters. Therefore, the current study depicted that the cardioprotective effect of Met and CsA on BDL rats is mediated through the balance between pAMPK and apoptosis in the mitochondria.

Myocardial Dysfunction in Cirrhotic Cardiomyopathy is Associated with Alterations of Phospholamban Phosphorylation and IL-6 Levels

BACKGROUND

Decreased cardiac contractility has been observed in cirrhosis, but the mechanisms that initiate and maintain cardiac dysfunction are not entirely understood.

AIM OF THE STUDY

We test the hypothesis that cirrhotic cardiomyopathy is related to deterioration of myocardial contractility due to alterations in calcium-handling proteins expression. In addition, we evaluated whether cardiac pro-inflammatory cytokine levels are associated with this process.

METHODS

Cirrhosis was induced by thioacetamide (TAA, 100 mg/kg/i.p., twice weekly for eight weeks). The myocardial performance was evaluated in isolated left ventricle papillary muscles under basal conditions and after inotropic challenge. The cardiac calcium handling protein expression was detected by Western blotting. Cardiac TNF-α and IL-6 levels were measured by ELISA.

RESULTS

Thioacetamide induced liver cirrhosis, which was associated with cirrhotic cardiomyopathy characterized by in vivo left ventricular diastolic and systolic dysfunction as well as cardiac hypertrophy. In vitro baseline myocardial contractility was lower in cirrhosis. Also, myocardial responsiveness to post-rest contraction stimulus was declined. Protein expression for RYR2, SERCA2, NCX, pPBL Ser¹⁶ and L-type calcium channel was quantitatively unchanged; however, pPBL Thr¹⁷ was significantly lower while IL-6 was higher.

CONCLUSIONS

Our study demonstrates that cirrhotic cardiomyopathy is associated with decreased cardiac contractility with alteration of phospholamban phosphorylation in association with higher cardiac pro-inflammatory IL-6 levels. These findings provided molecular and functional insights about the effects of liver cirrhosis on cardiac function.

Heart and bile acids - Clinical consequences of altered bile acid metabolism

Cardiac dysfunction has an increased prevalence in diseases complicated by liver cirrhosis such as primary biliary cholangitis and primary sclerosing cholangitis. This observation has led to research into the association between abnormalities in bile acid metabolism and cardiac pathology. Approximately 50% of liver cirrhosis cases develop cirrhotic cardiomyopathy. Bile acids are directly implicated in this, causing QT interval prolongation, cardiac hypertrophy, cardiomyocyte apoptosis and abnormal haemodynamics of the heart. Elevated maternal serum bile acids in intrahepatic cholestasis of pregnancy, a disorder which causes an impaired feto-maternal bile acid gradient, have been associated with fatal fetal arrhythmias. The hydrophobicity of individual bile acids in the serum bile acid pool is of relevance, with relatively lipophilic bile acids having a more harmful effect on the heart. Ursodeoxycholic acid can reverse or protect against these detrimental cardiac effects of elevated bile acids.

Recent advances in cirrhotic cardiomyopathy

Cirrhotic cardiomyopathy, a cardiac dysfunction presented in patients with cirrhosis, represents a recently recognized clinical entity. It is characterized by altered diastolic relaxation, impaired contractility, and electrophysiological abnormalities, in particular prolongation of the QT interval. Several mechanisms seem to be involved in the pathogenesis of cirrhotic cardiomyopathy, including impaired function of beta-receptors, altered transmembrane currents, and overproduction of cardiodepressant factors, like nitric oxide, tumor necrosis factor α, and endogenous cannabinoids. Diastolic dysfunction is the first manifestation of cirrhotic cardiomyopathy and reflects the increased stiffness of the cardiac mass, which leads to delayed left ventricular filling. On the other hand, systolic incompetence is presented later, is usually unmasked during pharmacological or physical stress, and predisposes to the development of hepatorenal syndrome. The prolongation of QT is found in about 50 % of cirrhotic patients, but rarely leads to fatal arrhythmias. Cirrhotics with blunted cardiac function seem to have poorer survival rates compared to those without, and the risk is particularly increased during the insertion of transjugular intrahepatic portosystemic shunt or liver transplantation. Till now, there is no specific treatment for the management of cirrhotic cardiomyopathy. New agents, targeting to its pathogenetical mechanisms, may play some role as future therapeutic options.

Cirrhotic cardiomyopathy: pathogenesis and clinical relevance

Cirrhosis is known to cause alterations in the systemic haemodynamic system. Cirrhotic cardiomyopathy designates a cardiac dysfunction that includes impaired cardiac contractility with systolic and diastolic dysfunction, as well as electromechanical abnormalities in the absence of other known causes of cardiac disease. This condition is primarily revealed by inducing physical or pharmacological stress, but echocardiography is excellent at revealing diastolic dysfunction and might also be used to detect systolic dysfunction at rest. Furthermore, measurement of circulating levels of cardiac biomarkers could improve the diagnostic assessm+ent. Cirrhotic cardiomyopathy contributes to various complications in cirrhosis, especially as an important factor in the development of hepatic nephropathy. Additionally, cirrhotic cardiomyopathy seems to be associated with the development of heart failure in relation to invasive procedures such as shunt insertion and liver transplantation. Current pharmacological treatment is nonspecific and directed towards left ventricular failure, and liver transplantation is currently the only proven treatment with specific effect on cirrhotic cardiomyopathy.