apyrase and Chemical-and-Drug-Induced-Liver-Injury

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 (P2X7-/-), and in wild-type mice. P2X7-/- 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 P2X7-/- 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 ecto-NTPDase CD39 (CD39-/-) that metabolizes ATP was examined in parallel with the use of soluble apyrase to deplete extracellular ATP in wild-type mice. CD39-/- 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-1β release. In conclusion, P2X7 and exposure to the ligands ATP and NAD are required for manifestations of APAP-induced hepatotoxicity.

Topics: Acetaminophen; Animals; Antigens, CD; Antipyretics; Apyrase; Cells, Cultured; Chemical and Drug Induced Liver Injury; Hemorrhage; Inflammasomes; Interleukin-1beta; Kupffer Cells; Male; Mice; Mice, Inbred C57BL; NAD; Necrosis; Pyridines; Receptors, Purinergic P2X7; Signal Transduction; Tetrazoles

Concanavalin A (Con A)-induced injury is an established natural killer T (NKT) cell-mediated model of inflammation that has been used in studies of immune liver disease. Extracellular nucleotides, such as adenosine triphosphate, are released by Con A-stimulated cells and bind to specific purinergic type 2 receptors to modulate immune activation responses. Levels of extracellular nucleotides are in turn closely regulated by ectonucleotidases, such as CD39/NTPDase1. Effects of extracellular nucleotides and CD39 on NKT cell activation and upon hepatic inflammation have been largely unexplored to date. Here, we show that NKT cells express both CD39 and CD73/ecto-5'-nucleotidase and can therefore generate adenosine from extracellular nucleotides, whereas natural killer cells do not express CD73. In vivo, mice null for CD39 are protected from Con A-induced liver injury and show substantively lower serum levels of interleukin-4 and interferon-gamma when compared with matched wild-type mice. Numbers of hepatic NKT cells are significantly decreased in CD39 null mice after Con A administration. Hepatic NKT cells express most P2X and P2Y receptors; exceptions include P2X3 and P2Y11. Heightened levels of apoptosis of CD39 null NKT cells in vivo and in vitro appear to be driven by unimpeded activation of the P2X7 receptor.. CD39 and CD73 are novel phenotypic markers of NKT cells. In turn, CD39 expression [corrected] modulates nucleotide-mediated cytokine production by, and limits apoptosis of, hepatic NKT cells. Deletion of CD39 is protective in [corrected] Con A-induced hepatitis. This study illustrates a [corrected] role for purinergic signaling in NKT-mediated mechanisms that result in liver immune injury.

Topics: 5'-Nucleotidase; Adenosine Triphosphate; Animals; Antigens, CD; Apoptosis; Apyrase; Chemical and Drug Induced Liver Injury; Concanavalin A; Disease Models, Animal; Killer Cells, Natural; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitogens; Nucleotides; Receptors, Purinergic P2; Receptors, Purinergic P2X7; T-Lymphocyte Subsets