Mechanisms of TNFα-induced cardiac dysfunction in cholestatic bile duct-ligated mice: Interaction between TNFα and endocannabinoids

Abstract

Background & Aims Chronic liver disease is associated with endotoxemia, oxidative stress, increased endocannabinoids and decreased cardiac responsiveness. Endocannabinoids activate the tumor necrosis factor-alpha (TNFα)–nuclear factor κB (NFκB) pathway. However, how they interact with each other remains obscure. We therefore aimed to clarify the relationship between the TNFα–NFκB pathway and endocannabinoids in the pathogenesis of cardiodepression of cholestatic bile duct ligated (BDL) mice. Methods BDL mice with TNFα knockout (TNFα−/−) and infusion of anti-TNFα antibody were used. Cardiac mRNA and protein expression of NFκBp65, c-Jun-N-terminal kinases (JNK), p38 mitogen-activated protein kinase (p38MAPK), extracelullar-signal-regulated kinase (ERK), inducible nitric oxide synthase (iNOS), Copper/Zinc and Magnesium-superoxide dismutase (Cu/Zn- and Mn-SOD), cardiac anandamide, 2-arachidonoylglycerol (2-AG), nitric oxide (NOx) and glutathione, and plasma TNFα were measured. The effects of TNFα, cannabinoid receptor (CB1) antagonist AM251 and the endocannabinoid reuptake inhibitor UCM707, on the contractility of isolated cardiomyocytes, were assessed. Results In BDL mice, cardiac mRNA and protein expression of NFκBp65, p38MAPK, iNOS, NOx, anandamide, and plasma TNFα were increased, whereas glutathione, Cu/Zn-SOD, and Mn-SOD were decreased. Cardiac contractility was blunted in BDL mice. Anti-TNFα treatment in BDL mice decreased cardiac anandamide and NOx, reduced expression of NFκBp65, p38MAPK, and iNOS, enhanced expression of Cu/Zn-SOD and Mn-SOD, increased reductive glutathione and restored cardiomyocyte contractility. TNFα-depressed contractility was worsened by UCM707, whereas AM251 improved contractility. Conclusions Increased TNFα, acting via NFκB–iNOS and p38MAPK signaling pathways, plays an important role in the pathogenesis of cardiodepression in BDL mice. TNFα also suppressed contractility by increasing oxidative stress and endocannabinoid activity.

Role of Oxygen Free Radicals, Nitric Oxide and Mitochondria in Mediating Cardiac Alterations During Liver Cirrhosis Induced by Thioacetamide

“…Cholestasis in the liver results in elevated plasma TNF-α in mice, accompanied by increased cardiac mRNA and protein expression of p38 MAPK and iNOS [16]. Activation of p38 MAPK can contribute to loss of cardiac contractility [31] and also regulate NO production [32].…”

“…The initial elevation could be due to increased protein synthesis, but subsequently there is a robust phosphorylation of the protein resulting in its sustained activation. Activation of p38 MAPK in cholestatic mice was accompanied by changes in glutathione and antioxidant enzymes suggestive of oxidant stress [16], and the damaging effects of NO can be amplified several fold by its reaction with free radical intermediates such as superoxide [33], implicating oxidative stress in cardiac damage during TAA-induced cirrhosis.…”

“…However, it has been shown that TAA administration does not directly produce alterations in the heart [30], and cardiac modifications occurring in ascitic rats with biliary cirrhosis are related to NO [28]. The fact that bile duct ligation per se, without cirrhosis, resulted in elevation of cardiac mRNA, and protein for iNOS [16] lends further credence to this possibility that early liver damage itself can upregulate NO production in the heart irrespective of the trigger.…”

“…Oxidative stress has been suggested to be involved in cardiac dysfunction in the cirrhotic heart [16], and an increase in lipid peroxidation markers has been demonstrated in the kidney, brain and heart of rats with cholestatic liver disease suggesting oxidative damage to different organs [17]. Mitochondria are an important cellular source as well as target of oxygen free radicals, and intestinal and renal mitochondria have been shown to be significantly affected in liver cirrhosis [13,15].…”

Immunodysfunction in Acute-on-Chronic Liver Failure

“…In rat models of liver cirrhosis, endotoxin-induced TNF-α reduces cardiac contractility and increases arterial vasodilatation by inducing nitric oxide production, which can be ameliorated by selective bowel decontamination [18,19]. Higher grades of systemic inflammation in ACLF are strongly associated with -and likely causally linked to -organ failures, which constitute the discriminative characteristic of ACLF versus acutely decompensated cirrhosis [12].…”