P2X7 receptor-mediated purinergic signaling promotes liver injury in acetaminophen hepatotoxicity in mice

Abstract

SC, Mehal WZ. P2x7 receptor-mediated purinergic signaling promotes liver injury in acetaminophen hepatotoxicity in mice. Am J Physiol Gastrointest Liver Physiol 302: G1171-G1179, 2012. First published March 1, 2012; doi:10.1152/ajpgi.00352.2011.-Inflammation contributes to liver injury in acetaminophen (APAP) hepatotoxicity in mice and is triggered by stimulation of immune cells. The purinergic receptor P2X7 is upstream of the nod-like receptor family, pryin domain containing-3 (NLRP3) inflammasome in immune cells and is activated by ATP and NAD that serve as damage-associated molecular patterns. APAP hepatotoxicity was assessed in mice genetically deficient in P2X7, the key inflammatory receptor for nucleotides (P2X7Ϫ/Ϫ), and in wild-type mice. P2X7Ϫ/Ϫ mice had significantly decreased APAP-induced liver necrosis. In addition, APAP-poisoned mice were treated with the specific P2X7 antagonist A438079 or etheno-NAD, a competitive antagonist of NAD. Pre-or posttreatment with A438079 significantly decreased APAP-induced necrosis and hemorrhage in APAP liver injury in wild-type but not P2X7Ϫ/Ϫ mice. Pretreatment with etheno-NAD also significantly decreased APAP-induced necrosis and hemorrhage in APAP liver injury. In addition, APAP toxicity in mice lacking the plasma membrane ectoNTPDase CD39 (CD39Ϫ/Ϫ) that metabolizes ATP was examined in parallel with the use of soluble apyrase to deplete extracellular ATP in wild-type mice. CD39Ϫ/Ϫ mice had increased APAP-induced hemorrhage and mortality, whereas apyrase also decreased APAP-induced mortality. Kupffer cells were treated with extracellular ATP to assess P2X7-dependent inflammasome activation. P2X7 was required for ATP-stimulated IL-1␤ release. In conclusion, P2X7 and exposure to the ligands ATP and NAD are required for manifestations of APAPinduced hepatotoxicity.CD39; nod-like receptor family, pryin domain containing-3, caspase-1; inflammasome; damage-associated molecular pattern ACETAMINOPHEN (APAP) overdose is the most common cause of acute liver failure in the Unites States and Europe (15,18,24). Furthermore, cases of acute hepatic failure due to APAP continue to rise (24). Toxicity is initiated by metabolism of APAP via reductive pathways to reactive metabolites. An antidote exists for patients early in the course of poisoning during this metabolism phase. However, with increased delays in administration of therapy, the frequency with which patients develop hepatocellular injury worsens.The initial, direct toxic injury induces an area of necrosis in the centrilobular regions. Liver injury is propagated by an inflammatory response after the drug has been metabolized and the initial centrilobular injury has occurred (23). The nature of this inflammatory response has been the subject of significant investigation in the past several years.Prior research by our group indicates that inflammasome activation is a crucial initiating step in the propagation of APAP-induced hepatic injury (10). Proinflammatory cytokines IL-1␤ and IL-18 are thought to be crucial to the prop...

Selenium Nanoparticles Ameliorative Effect on Acetaminophen Hepatotoxicity in Male Mice

“…ALP, AST and ALT were increased significantly (p < 0.01) in the group received APAP indicating the toxic effect of the drug. Several investigations accumulated similar findings [6][7][8][9][10][11][12][13]. The enzymes activity in the groups treated with SeNPs immediately after APAP supplementation or in combination with APAP showed normal enzyme activity with no significant difference to that of the control (Table 1).…”

“…Liver cells eliminate free radicals and face apoptosis as a result of the drug hepatotoxicity [5]. Several studies tackled the hepatotoxic effect of APAP in male and female mice and rat [6][7][8][9][10][11][12][13].…”

P2X receptors regulate adenosine diphosphate release from hepatic cells

“…Elevated circulating nucleotide levels and sustained purinergic signaling may consequently promote inflammatory diseases [7,8]. Consistent with this view, knockout of P2Y and ion channel purinergic receptors (P2X) in mice has been shown to significantly reduce inflammatory disease in the heart, liver, kidney, and other tissues [9][10][11][12][13][14].…”

Purinergic signalling in the liver in health and disease

“…P2X7 is required for hepatic caspase-1 activation and migration of neutrophils into the liver. This suggests that extracellular ATP may play a pivotal role in development of the inflammasome after APAP overdose [130]. The P2X7 receptor antagonist A438079 is protective against APAPinduced liver injury, and it was claimed that it acted by inhibiting P450 isoenzymes rather than by inflammasome activation [260].…”

“…We have shown that high levels of extracellular nucleotides promote injury while adenosine can be protective during acute inflammatory settings as in vascular reperfusion [14] or with acetaminophen (APAP) toxicity [130]. In the liver, like many tissues, ethanol or fructose ingestion leads to an increase in adenine nucleotide release with both CD39 and ecto-5′-nucleotidase (CD73)-dependent extracellular increases in adenosine concentration.…”