Male NMRI or BALB/c mice developed severe liver injury as assessed by transaminase release within 8 h when an intravenous dose > 1.5 mg/kg concanavalin A (Con A) was given. Histopathologically, only the liver was affected. Electron micrographs revealed leukocyte sticking to endothelial cells and bleb formation of hepatocytes. The hepatotoxicity of the lectin correlated neither with its agglutination activity nor with its sugar specificity. Administration of 0.5 mg/kg dexamethasone or 50 mg/kg cyclosporine A or 50 mg/kg FK 506 (Fujimycin) resulted in protection of the animals whereas indomethacin pretreatment failed to protect. Con A hepatitis was accompanied by the release of IL-2 into the serum of the animals. Mice with severe combined immunodeficiency syndrome lacking B as well as T lymphocytes were resistant against Con A. Athymic nude mice with immature T lymphocytes were also resistant. Pretreatment of mice with an antibody against T lymphocytes fully protected against Con A as did monoclonal anti-mouse CD4. Monoclonal anti-mouse CD8 failed to protect. Pretreatment of mice with silica particles, i.e., deletion of macrophages, prevented the induction of hepatitis. These findings provide evidence that Con A-induced liver injury depends on the activation of T lymphocytes by macrophages in the presence of Con A. The model might allow the study of the pathophysiology of immunologically mediated hepatic disorders such as autoimmune chronic active hepatitis. (J. Clin. Invest. 1992. 90:196-203.)

The crystal structure of bovine erythrocyte glutathione peroxidase has been refined by a combined procedure of restrained crystallographic refinement and energy minimization at 0.20 nm resolution. The final R value at this resolution is 0.178. The r.m.s. deviation of main-chain atoms of the two independently refined monomers is 0.019 nm. The structure at 0.28 nm resolution, which has been determined by multiple isomorphous replacement, served as a starting model.The refined model allowed a detailed survey of the hydrogen-bonding pattern and of the subunit contact areas in the molecule. The model contains 165 solvent molecules per dimer, all taken as water molecules. The mobility of the structure was derived from the individual atomic temperature factors. The complete tetramer, including the active sites, seems to be rather rigid, except for narrow loops near to the N-terminal ends and some p turns exposed to solvent.The active centres of glutathione peroxidase are found in flat depressions on the molecular surface. The catalytically active selenocysteine residues could be located at the N-terminal ends of a helices forming /YG$ substructures together with two adjacent parallel p strands. In the vicinity of the reactive group some aromatic amino acid side-chains could be localized. Especially Trp-148, which could be hydrogen bonded to SeCys-35, may play a functional role during catalysis.The results ofsubstrate and inhibitor binding studies in solution and in the crystalline state could be interpreted by an apparent half-site reactivity of glutathione peroxidase. The enzyme seems to react in the sense of negative cooperativity with dimers being the functional units.Based on difference Fourier analyses of appropriate derivatives a reasonable model of glutathione binding is presented. Among the residues which could be of functional importance are Arg-40, Gln-130 and Arg-167, presumably forming salt bridges and a hydrogen bond to the glutathione molecule.In conclusion, a general picture of a minimal reaction mechanism, which is in good agreement with functional and structural data, is proposed. The main reaction of the catalytic cycle presumably shuttles between the selenolate and the selenenic acid state of SeCys-35.

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Artificial mechanical ventilation represents a major cause of iatrogenic lung damage in intensive care. It is largely unknown which mediators, if any, contribute to the onset of such complications. We investigated whether stress caused by artificial mechanical ventilation leads to induction, synthesis, and release of cytokines or eicosanoids from lung tissue. We used the isolated perfused and ventilated mouse lung where frequent perfusate sampling allows determination of mediator release into the perfusate. Hyperventilation was executed with either negative (NPV) or positive pressure ventilation (PPV) at a transpulmonary pressure that was increased 2.5-fold above normal. Both modes of hyperventilation resulted in an approximately 1.75-fold increased expression of tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) mRNA, but not of cyclooxygenase-2 mRNA. After switching to hyperventilation, prostacyclin release into the perfusate increased almost instantaneously from 19 +/- 17 pg/min to 230 +/- 160 pg/min (PPV) or 115 +/- 87 pg/min (NPV). The enhancement in TNFalpha and IL-6 production developed more slowly. In control lungs after 150 min of perfusion and ventilation, TNFalpha and IL-6 production was 23 +/- 20 pg/min and 330 +/- 210 pg/min, respectively. In lungs hyperventilated for 150 min, TNFalpha and IL-6 production were increased to 287 +/- 180 pg/min and more than 1,000 pg/min, respectively. We conclude that artificial ventilation might cause pulmonary and systemic adverse reactions by inducing the release of mediators into the circulation.