HMGB1 neutralization is associated with bacterial translocation during acetaminophen hepatotoxicity

Background Acetaminophen (APAP) hepatotoxicity is associated with a high rate of gram-negative enteric bacterial infection; however, the underlying mechanism is still unknown. APAP overdose induces massive hepatocyte necrosis, necrotic tissue releases high mobility group B1 (HMGB1) and exogenous HMGB1 is able to induce gut bacterial translocation (BT) in normal mice; therefore, it is possible that HMGB1 mediates gut BT in APAP hepatotoxicity. This study aims to test this hypothesis by using anti-HMGB1 neutralizing antibody to treat APAP overdose for 24-48 hours. Methods Male C57BL/6 mice were intraperitoneally (i.p.) injected with a single dose of APAP (350 mg/kg dissolved in 1 mL sterile saline). 2 hrs after APAP injection, the APAP challenged mice were randomized to receive treatment with either anti-HMGB1 antibody (400 μg per dose) or non-immune (sham) IgG every 24 h for a total of 2 doses. Results 24 and 48 hrs after APAP challenge, anti-HMGB1 treatment instead of sham IgG therapy significantly decreased serum HMGB1 concentrations and reduced BT by 85%; serum HMGB1 levels were positively correlated with the amount of BT; anti-HMGB1 therapy decreased hepatic BT at 48 h, which was associated with better recovered liver structure and better restored hepatic immune system that was shown by enhanced hepatic mRNA expression of TNF-α, IL-6 and extensive proliferation of inflammatory and reticuloendothelial cells; however, anti-HMGB1 treatment did not decrease gut mucosal permeability as compared to the sham IgG therapy at either 24 or 48 hrs. Conclusion HMGB1 neutralization is associated with bacterial translocation during APAP hepatotoxicity.BioMed Central open acces

Ringer's lactate improves liver recovery in a murine model of acetaminophen toxicity

<p>Abstract</p> <p>Background</p> <p>Acetaminophen (APAP) overdose induces massive hepatocyte necrosis. Liver regeneration is a vital process for survival after a toxic insult. Since hepatocytes are mostly in a quiescent state (G₀), the regeneration process requires the priming of hepatocytes by cytokines such as TNF-α and IL-6. Ringer's lactate solution (RLS) has been shown to increase serum TNF-α and IL-6 in patients and experimental animals; in addition, RLS also provides lactate, which can be used as an alternative metabolic fuel to meet the higher energy demand by liver regeneration. Therefore, we tested whether RLS therapy improves liver recovery after APAP overdose.</p> <p>Methods</p> <p>C57BL/6 male mice were intraperitoneally injected with a single dose of APAP (300 mg/kg dissolved in 1 mL sterile saline). Following 2 hrs of APAP challenge, the mice were given 1 mL RLS or Saline treatment every 12 hours for a total of 72 hours.</p> <p>Results</p> <p>72 hrs after APAP challenge, compared to saline-treated group, RLS treatment significantly lowered serum transaminases (ALT/AST) and improved liver recovery seen in histopathology. This beneficial effect was associated with increased hepatic tissue TNF-α concentration, enhanced hepatic NF-κB DNA binding and increased expression of cell cycle protein cyclin D1, three important factors in liver regeneration.</p> <p>Conclusion</p> <p>RLS improves liver recovery from APAP hepatotoxicity.</p

Crystal Structure of an Engineered LRRTM2 Synaptic Adhesion Molecule and a Model for Neurexin Binding

Synaptic adhesion molecules are key components in development of the brain, and in the formation of neuronal circuits, as they are central in the assembly and maturation of chemical synapses. Several families of neuronal adhesion molecules have been identified such as the neuronal cell adhesion molecules, neurexins and neuroligins, and in particular recently several leucine-rich repeat proteins, e.g., Netrin G-ligands, SLITRKs, and LRRTMs. The LRRTMs form a family of four proteins. They have been implicated in excitatory glutamatergic synapse function and were specifically characterized as ligands for neurexins in excitatory synapse formation and maintenance. In addition, LRRTM3 and LRRTM4 have been found to be ligands for heparan sulfate proteoglycans, including glypican. We report here the crystal structure of a thermostabilized mouse LRRTM2, with a <i>T</i>_m 30 °C higher than that of the wild-type protein. We localized the neurexin binding site to the concave surface based on protein engineering, sequence conservation, and prior information about the interaction of the ligand with neurexins, which allowed us to propose a tentative model for the LRRTM–neurexin interaction complex. We also determined affinities of the thermostabilized LRRTM2 and wild-type LRRTM1 and LRRTM2 for neurexin-β1 with and without Ca²⁺. Cell culture studies and binding experiments show that the engineered protein is functional and capable of forming synapselike contacts. The structural and functional data presented here provide the first structure of an LRRTM protein and allow us to propose a model for the molecular mechanism of LRRTM function in the synaptic adhesion