Inflammatory Cascades Driven by Tumor Necrosis Factor-Alpha Play a Major Role in the Progression of Acute Liver Failure and Its Neurological Complications

Chastre, Anne; Bélanger, Marcel; Beauchesne, Élizabeth; Nguyen, Bich; Desjardins, Paul; Butterworth, Roger F.

doi:10.1371/journal.pone.0049670

Cited by 81 publications

(73 citation statements)

References 38 publications

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“…Etanercept also decreased IL-6 levels in the brain, attenuated microglial activation as assessed by OX-42 immunoreactivity, and increased brain glutathione concentrations. 63 Together, these studies support the role of inflammation, whether caused by infection or as a consequence of ALF itself, as being manifest in determining the severity, progression and outcome of HE in ALF. Figure 2 The systemic inflammatory response syndrome in the outcome of hepatic encephalopathy in acute liver failure adapted from Rolando et al .…”

Section: The Role Of Systemic Inflammation In Encephalopathy In Acutementioning

confidence: 65%

“…63 However, the proinflammatory response which develops as a consequence of acute liver injury is vital in initiating liver repair and regeneration and it may be detrimental to use agents targeted to key proinflammatory mediators. Moreover, as functional immunoparesis is a consistent finding in patients with ALF and CLF, 94,118,119 this could be detrimental rendering patients susceptible to bacterial and fungal infection.…”

Section: Agents Targeted To Key Pro-inflammatory Mediators and The Inmentioning

confidence: 99%

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Pathogenesis of Hepatic Encephalopathy: Role of Ammonia and Systemic Inflammation

Aldridge

Tranah

Shawcross

2015

Journal of Clinical and Experimental Hepatology

248

190

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The syndrome we refer to as Hepatic Encephalopathy (HE) was first characterized by a team of Nobel Prize winning physiologists led by Pavlov and Nencki at the Imperial Institute of Experimental Medicine in Russia in the 1890's. This focused upon the key observation that performing a portocaval shunt, which bypassed nitrogen-rich blood away from the liver, induced elevated blood and brain ammonia concentrations in association with profound neurobehavioral changes. There exists however a spectrum of metabolic encephalopathies attributable to a variety (or even absence) of liver hepatocellular dysfunctions and it is this spectrum rather than a single disease entity that has come to be defined as HE. Differences in the underlying pathophysiology, treatment responses and outcomes can therefore be highly variable between acute and chronic HE. The term also fails to articulate quite how systemic the syndrome of HE can be and how it can be influenced by the gastrointestinal, renal, nervous, or immune systems without any change in background liver function. The pathogenesis of HE therefore encapsulates a complex network of interdependent organ systems which as yet remain poorly characterized. There is nonetheless a growing recognition that there is a complex but influential synergistic relationship between ammonia, inflammation (sterile and non-sterile) and oxidative stress in the pathogenesis HE which develops in an environment of functional immunoparesis in patients with liver dysfunction. Therapeutic strategies are thus moving further away from the traditional specialty of hepatology and more towards novel immune and inflammatory targets which will be discussed in this review. ( J CLIN EXP HEPATOL 2015;5:S7-S20) H epatic encephalopathy (HE) is the term used to encapsulate the broad spectrum of neuropsychiatric disturbances associated with both acute and chronic liver failure (ALF and CLF, respectively), as well as porto-systemic bypass in the absence of hepatocellular disease. The clinical manifestations of HE can be extremely heterogeneous in nature, with symptoms presenting anywhere on a continuum spanning from seemingly normal cognitive performance, right the way through to states of confusion, stupor and coma. In between these extremes, patients with HE may exhibit signs such as inattentiveness, blunted affect, impairment of memory or reversal of the sleep-wake cycle, as well as physical manifestations such as tremor, myoclonus, asterixis and deep tendon hyperreflexia.ALF is defined by the onset of coagulopathy alongside any degree of encephalopathy in patients with no evidence of pre-existing liver disease. 1 The presence of HE in those with ALF is prognostic, with up to a quarter of cases developing raised intracranial pressure. 2 Patients presenting with ALF are at risk of developing its cardinal, lifethreatening feature, cerebral edema. Left untreated, cerebral edema can rapidly progress to cause herniation of the uncus through the falx cerebri, leading to compression of the brainstem and, ultimately, death. H...

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Section: The Role Of Systemic Inflammation In Encephalopathy In Acutementioning

confidence: 65%

Section: Agents Targeted To Key Pro-inflammatory Mediators and The Inmentioning

confidence: 99%

Pathogenesis of Hepatic Encephalopathy: Role of Ammonia and Systemic Inflammation

Aldridge

Tranah

Shawcross

2015

Journal of Clinical and Experimental Hepatology

248

190

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“…Treatment of ALF mice with etanercept delays the onset of severe encephalopathy while reducing the neuroinflammatory response. 62 A previous study in the same animal model showed that TNFa gene deletion likewise led to attenuation of the neurological complications. 41 As stated above, mild hypothermia and NAC both have the potential to reduce ALF-related increases of the brain production of pro-inflammatory cytokines including TNFa.…”

Section: Anti-inflammatory Strategiesmentioning

confidence: 93%

Pathogenesis of Hepatic Encephalopathy and Brain Edema in Acute Liver Failure

Butterworth

2015

Journal of Clinical and Experimental Hepatology

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117

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Neuropathologic investigations in acute liver failure (ALF) reveal significant alterations to neuroglia consisting of swelling of astrocytes leading to cytotoxic brain edema and intracranial hypertension as well as activation of microglia indicative of a central neuroinflammatory response. Increased arterial ammonia concentrations in patients with ALF are predictors of patients at risk for the development of brain herniation. Molecular and spectroscopic techniques in ALF reveal alterations in expression of an array of genes coding for neuroglial proteins involved in cell volume regulation and mitochondrial function as well as in the transport of neurotransmitter amino acids and in the synthesis of pro-inflammatory cytokines. Liver-brain pro-inflammatory signaling mechanisms involving transduction of systemically-derived cytokines, ammonia neurotoxicity and exposure to increased brain lactate have been proposed. Mild hypothermia and N-Acetyl cysteine have both hepatoprotective and neuro-protective properties in ALF. Potentially effective anti-inflammatory agents aimed at control of encephalopathy and brain edema in ALF include etanercept and the antibiotic minocycline, a potent inhibitor of microglial activation. Translation of these potentially-interesting findings to the clinic is anxiously awaited. ( J CLIN EXP HEPATOL 2015;5:S96-S103) A cute liver failure (ALF), also referred to as fulminant hepatic failure, invariably leads to central nervous system dysfunction that may include encephalopathy, seizures and brain edema, a major cause of intracranial hypertension and brain herniation, a leading cause of mortality in ALF. An increase in cerebral blood flow frequently accompanies the onset of brain edema. 1Neuropathological assessments of the brain in both human and experimental ALF reveals significant changes to neuroglia in general and to astrocytes and microglia, in particular. Astrocytes in brain sections from patients who died in ALF are swollen 2 as are their mitochondria (Figure 1). Based upon these observations, it is generally assumed that the brain edema that accompanies ALF is primarily, if not exclusively, cytotoxic in nature. Studies in experimental animals with ALF due to toxic liver injury show a similar pattern of changes as well as alterations in expression of genes coding for key astrocytic proteins. 3Although gross alterations of the blood-brain barrier (BBB) are not generally a feature of ALF, alterations of cerebrovascular endothelial cell function have occasionally been described. 2,4 On the other hand, material from ALF animals in which edema and encephalopathy were precipitated by infection manifest clear alterations of both BBB function and of expression of BBB tight junction proteins.5 These latter findings suggest that, in ALF accompanied by significant infection/inflammation, brain edema may comprise both cytotoxic and vasogenic components. BRAIN METABOLISM IN ACUTE LIVER FAILUREALF leads to severe compromise of cerebral metabolism and includes increases of cerebral blood flow, decrea...

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“…The "TNF theory" of HA/HE pathogenesis [8] emphasizes significant roles of TNF-α and other cytokines in HE up to the extent that these cytokines could be used as markers for encephalopathy grading [4,[9][10][11][12][13]. Obviously, TNF-α could be considered a suitable target for therapeutic intervention, however, with limited information on its responsiveness towards RSV in neuroinflammation and neuroexcitotoxicity.…”

Section: Discussionmentioning

confidence: 99%

“…Later studies have also emphasized significant involvement of TNF-α and other cytokines in HE to the extent that these cytokines could be used as markers for encephalopathy grading [4,[9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Resveratrol Normalizes Hyperammonemia Induced Pro-Inflammatory and Pro-Apoptotic Conditions in Rat Brain

Khanna¹,

Trigun²

2016

IJCAM

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Research ArticleInt J Complement Alt Med 2016, 4(2): 00115 IntroductionAmmonia neurotoxicity is considered responsible for development of a serious nervous system disorder called hepatic encephalopathy (HE). This situation arises mainly due to liver dysfunction led hyperammonemia (HA). HE is characterized by the neuropsychiatric manifestations related to motor dysfunction, memory impairment, and deranged sleep-awake cycle [1,2]. Since HE affects the quality of life of the patients, it is important to develop effective therapeutic strategy against HE. This necessitates understanding the neuro-chemistry of HA pathogenesis.Since ammonia crosses the blood brain barrier easily, prolonged HA condition, a common situation during chronic liver failure (CLF), is likely to maintain increased ammonia concentration in brain [3,4]. The information, mainly derived from the cell culture system and from animal models with acute HE, suggest that the increased brain ammonia level mainly drives astrocytes to undergo significant morpho-pathological changes and also over activates glutamate-NMDA receptor (N-Methyl-D-Aspartate Receptor) pathway in the post-synaptic neurons [1,[5][6][7]. Moreover, NMDAR inhibition could not be translated into prevention of ammonia neurotoxicity, mainly because threshold glutamate-NMDAR activation is necessary for normal neurological functions including higher order brain functions and normal synaptic activity.During recent past, "TNF theory" (Tumor necrosis factor) of HE pathogenesis could draw much attention due to a close association between the level of TNF-α and ammonia in the brain of CLF patients with HE [8]. Later studies have also emphasized significant involvement of TNF-α and other cytokines in HE to the extent that these cytokines could be used as markers for encephalopathy grading [4,[9][10][11][12][13].It is now evident that the microglia and astroglia cells in brain synthesize TNF-α to regulate higher order brain functions and astrocyte induced synaptic strengthening [14][15][16][17]. However, when produced in higher amounts during neuropathology, they are known to potentiate glutamate induced cytotoxicity by inhibiting glutamate transport to the glial cells from the synaptic cleft [12,[16][17][18][19]. Even development of MHE has been described to be dependent more on enhanced inflammatory markers than the severity of CLF or HA in the CLF patients [20]. Moreover, some findings from in vitro studies suggest that resveratrol treatment could prevent ammonia toxicity in astroglial cells by normalizing ROS/RNS level [12,21,22]. Thus, hinting towards a significant role of resveratrol in ameliorating ammonia toxicity. However, the mechanism by which resveratrol does so is unclear.Resveratrol (3, 3, 4'-trihydroxy-Trans stilbene), a natural polyphenol, is found in a number of dietary sources such as grapes, berries, and red wine [23][24][25]. It acts as an effective cardioprotector, AbstractChronic liver failure (CLF) led hyperammonemia (HA) is known to develop a metabolic brain disorder known a...

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Inflammatory Cascades Driven by Tumor Necrosis Factor-Alpha Play a Major Role in the Progression of Acute Liver Failure and Its Neurological Complications

Cited by 81 publications

References 38 publications

Pathogenesis of Hepatic Encephalopathy: Role of Ammonia and Systemic Inflammation

Pathogenesis of Hepatic Encephalopathy: Role of Ammonia and Systemic Inflammation

Pathogenesis of Hepatic Encephalopathy and Brain Edema in Acute Liver Failure

Resveratrol Normalizes Hyperammonemia Induced Pro-Inflammatory and Pro-Apoptotic Conditions in Rat Brain

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