Divergent role of heme oxygenase inhibition in the pathogenesis of sepsis

The reduction of neutrophil migration to an infectious focus is associated with a high mortality in severe sepsis. Previously, we showed that heme oxygenase (HO) products downregulate neutrophil recruitment in a noninfectious inflammatory model. The present study was designed to determine the role of HO in sepsis induced by cecal ligation and puncture (CLP) model. We demonstrated that pretreatment, but not the combination of pretreatment plus posttreatment with zinc protoporphyrin IX (ZnPP IX), an HO inhibitor, prevented the reduction of CXCR2 on circulating neutrophils and the failure of intraperitoneal neutrophil migration to the site of infection. Consequently, bacterial dissemination, systemic inflammatory response, and organ injury were prevented. In addition, pretreatment with the HO inhibitor avoided hypotension and consequently increased survival. Moreover, in mice subjected to severe CLP, the pretreatment, but not the combination of pretreatment plus posttreatment with ZnPP IX, prevented the increase of plasmatic free heme observed in nontreated severe CLP. The administration of exogenous hemin to mice subjected to moderate sepsis consistently increased the mortality rate. Furthermore, hemin resulted in a reduction of neutrophil migration both in vivo and in vitro. Altogether, our results demonstrated that pretreatment with the HO inhibitor prevents the pathological findings in severe CLP. However, the combination of pretreatment plus posttreatment with ZnPP IX enhances sepsis severity because of an increase in circulating levels of heme, which is deleterious to the host tissues and also inhibits neutrophil migration.     

N-acetylcysteine as a potentially useful medication to prevent conversion to schizophrenia in at-risk individuals

Schizophrenia is a chronic and often severe psychotic disorder. Its causes include imbalances in mediators involved in neuroplasticity, apoptosis, cell resilience and dendritic arborization. Among these mediators, oxidative species are particularly relevant for the pathophysiology of the disease, and this is the rationale for experimental use of antioxidant medications, such as N-acetylcysteine (NAC). Onset of schizophrenia is usually preceded by a period of subtle and unspecific symptoms, the prodrome, in which preventive interventions could delay or even stop the progression to full-blown psychosis. In this article, we propose that NAC could be a useful medication to prevent evolution of schizophrenia in individuals at risk for psychosis.     

Erysothrine, an alkaloid extracted from flowers of Erythrina mulungu Mart. ex Benth: evaluating its anticonvulsant and anxiolytic potential

In this study, we isolated the alkaloid erysothrine from the hydroalcoholic extract of flowers from E. mulungu and screened for its anticonvulsant and anxiolytic actions based on neuroethological and neurochemical experiments. Our results showed that the administration of erysothrine inhibited seizures evoked by bicuculline, PTZ, NMDA and most remarkably, kainic acid. Also, erysothrine induced an increase in the number of entries but not in the time spent in the open arms of the EPM. However, we did not notice any alterations in the light-dark choice or in the open-field tests. In preliminary neurochemistry tests, we also showed that erysothrine (0.001-10 μg/mL) did not alter the GABA or glutamate synaptossomal uptake and binding. Altogether, our results describe an alkaloid with anticonvulsant activity and mild anxiolytic activity that might be considered well tolerated as it does not alter the general behavior of the animals in the used doses.     

Immune hemolytic anemia caused by sensitivity to a metabolite of etodolac, a nonsteroidal anti-inflammatory drug

BACKGROUND: Immune hemolytic anemia can be caused by sensitivity to many different drugs. In some instances, the sensitizing compound can be identified by in vitro testing, but results are often negative. One reason for this is that a drug metabolite formed in vivo can be the sensitizing agent, but the responsible metabolites have rarely been identified at a chemical level. This report describes a patient who developed severe, Coombs-positive hemolytic anemia on two occasions after taking the nonsteroidal anti-inflammatory drug etodolac. Studies were performed to characterize etodolac metabolites to which this patient was sensitive. CASE REPORT: Serum was tested for antibody in the presence and absence of drug using conventional methods and urine from individuals taking etodolac as a source of drug metabolites. Urinary metabolites of etodolac were identified by high-pressure liquid chromatography analysis. Glucuronide conjugates of etodolac and the 6-OH metabolite of etodolac were synthesized in a rat liver microsomal system to obtain reference standards. RESULTS: The patient's serum gave only trace (+/-) reactions with normal RBCs in the presence of etodolac but reacted strongly (4+) in the presence of urine from an individual taking this drug. The active urinary metabolites were identified as etodolac glucuronide and 6-OH etodolac glucuronide. CONCLUSION: This patient appears to have experienced acute, severe immune hemolytic anemia on two occasions because of sensitivity to the glucuronides of etodolac and 6-OH etodolac. In patients suspected of having drug-induced immune hemolytic anemia, RBC-reactive antibodies can sometimes be detected by using urine from an individual taking the implicated medication as the source of drug metabolites in in vitro reactions. For patients who present with acute immune hemolysis, a careful history of drug exposure should be taken, and, where indicated, confirmatory testing should be performed to identify the sensitizing drug and prevent inadvertent reinduction of hemolysis at a later time.     

γδ T cells affect IL-4 production and B-cell tolerance

γδ T cells can influence specific antibody responses. Here, we report that mice deficient in individual γδ T-cell subsets have altered levels of serum antibodies, including all major subclasses, sometimes regardless of the presence of αβ T cells. One strain with a partial γδ deficiency that increases IgE antibodies also displayed increases in IL-4–producing T cells (both residual γδ T cells and αβ T cells) and in systemic IL-4 levels. Its B cells expressed IL-4–regulated inhibitory receptors (CD5, CD22, and CD32) at diminished levels, whereas IL-4–inducible IL-4 receptor α and MHCII were increased. They also showed signs of activation and spontaneously formed germinal centers. These mice displayed IgE-dependent features found in hyper-IgE syndrome and developed antichromatin, antinuclear, and anticytoplasmic autoantibodies. In contrast, mice deficient in all γδ T cells had nearly unchanged Ig levels and did not develop autoantibodies. Removing IL-4 abrogated the increases in IgE, antichromatin antibodies, and autoantibodies in the partially γδ-deficient mice. Our data suggest that γδ T cells, controlled by their own cross-talk, affect IL-4 production, B-cell activation, and B-cell tolerance.The role of γδ T cells within the vertebrate immune system is not yet fully understood, but it has become clear that they exert a strong influence on the immune responses. These cells represent a system of specialized subsets with different developmental kinetics, tissue distributions, and functional roles (1). Moreover, at least some of the subsets appear to balance each other’s influence on the immune system (2). Like αβ T cells and B cells, γδ T cells express antigen receptors encoded by rearranging genes (3, 4), which enable adaptive responses to antigenic challenge. Following such stimulation in the course of diseases, γδ T-cell populations can undergo large changes in size and subset composition (5). The γδ T-cell populations also change during ontogeny and due to interindividual genetic differences (6, 7). Conceivably, such changes might alter γδ T-cell balance and, with it, γδ T-cell influence on other immune cells.In mice and humans, it was found that functional attributes of γδ T cells segregate with expressed γδ T-cell receptors (TCRs) (8, 9), although functional differentiation has also been observed within or across TCR-defined subsets and correlated with other markers, such as CD27 and CD8 (10, 11). The murine TCR-γ locus contains seven Vγ genes, six of which are functional and expressed on the cell surface (3, 12). In the normal mouse spleen, the largest γδ T-cell population expresses Vγ1, followed by Vγ4^pos cells and smaller populations expressing Vγ2 and Vγ7 (13). Vγ5^pos and Vγ6^pos cells are not present in substantial numbers. In earlier studies relying on cell transfer and targeted inactivation with antibodies, we and others (8, 10, 14, 15) found that splenic Vγ1^pos and Vγ4^pos cells exert opposite influences on host responses to infection, allergic sensitization, and malignancy. The data suggested that these two γδ T-cell subsets balance each other in their influence on the immune responses (2).In the current study, we further tested this idea by examining antibody levels and B cells in nonimmunized mice genetically deficient either in individual γδ T-cell subsets or in all γδ T cells. The focus on antibodies derives from our earlier observation that mutant mice selectively deficient in Vγ4 and Vγ6 (B6.TCR-Vγ4^−/−/6^−/−) produce substantially more IgE antibody than WT controls or mice deficient in all γδ T cells (B6.TCR-δ^−/−) (10). Here, we report that deficiency in individual γδ T-cell subsets (16, 17) can change antibody production and B-cell activation in nonimmunized mice to a degree that jeopardizes self-tolerance. However, the effect cannot simply be ascribed to an altered γδ T-cell balance. Instead, it correlates with functional changes that occur within the remaining γδ T cells themselves, when they are no longer restrained by normal γδ cross-talk. Our data show that this cross-talk controls the amount of IL-4 produced by a subset of γδ T cells and other T cells, resulting in downstream effects on antibodies, B cells, and self-tolerance.