Short- and long-term effects of T-cell modulating agents in experimental autoimmunity

Sensitivity of the sea snail Gibbula umbilicalis to mercury exposure--linking endpoints from different biological organization levels

Mercury contamination is a common phenomenon in the marine environment and for this reason it is important to develop cost-effective and relevant tools to assess its toxic effects on a number of different species. To evaluate the possible effects of Hg in the sea snail Gibbula umbilicalis, animals were exposed to increasing concentrations of the contaminant in the ionic form for 96 h. After this exposure period, mortality, feeding and flipping behavior, the activity of the biomarkers glutathione S-transferase, superoxide dismutase, catalase, lactate dehydrogenase and cholinesterase, the levels of lipid peroxidation and cellular energy allocation were measured. After 96 h of exposure to the highest Hg concentration (≈LC20), there was a significant inhibition of the cholinesterase activity as well as impairment in the flipping behavior and post-exposure feeding of the snails. Cholinesterase inhibition was correlated with the impairment of behavioral responses also caused by exposure to Hg. These endpoints, including the novel flipping test, revealed sensitivity to Hg and might be used as relevant early warning indicators of prospective effects at higher biological organization levels, making these parameters potential tools for environmental risk assessment. The proposed test species showed sensitivity to Hg and proved to be a suitable and resourceful species to be used in ecotoxicological testing to assess effects of other contaminants in marine ecosystems.

The spectrum of thrombotic thrombocytopenic purpura: a clinicopathologic demonstration of tacrolimus-induced thrombotic thrombocytopenic purpura in a lung transplant patient

Immunosuppressive drugs used post-transplantation are among the most common causes of thrombotic thrombocytopenic purpura (TTP). Diagnosis is often confounded not only by its myriad presentations, but also because these manifestations may be explained by the comorbidities or complications of transplantation. A 61-year-old female who had a single lung transplant for severe chronic obstructive pulmonary disease maintained on corticosteroids, tacrolimus and mycophenolate mofetil, was admitted for fever, headache with confusion and lethargy. She was mildly anemic and thrombocytopenic. Peripheral smear showed rare fragmented red cells. Muddy brown casts were present on urinalysis. She was diagnosed with TTP. Tacrolimus was discontinued and the mental status of the patient, anemia and thrombocytopenia improved significantly.

Selective effect of mercury on Th2-type cytokine production in humans

Mercury induces autoimmune disease and increases IL-4 production and IgE levels in certain rodent strains. The object of this study was to determine if mercury was capable of inducing Th2 cytokine production in human leucocytes. Human peripheral blood mononuclear cells (PBMC) were incubated with PMA/ionomycin or Con A in the presence or absence of methyl mercury (CH(3)Hg) or mercuric chloride (HgCl(2)). IL-4 and gamma-IFN were measured by ELISA.

RESULTS

IL-4 production significantly increased at low concentrations of CH(3)Hg (0.5 uM, p < 0.01), while gamma-IFN production was suppressed starting at CH(3)Hg 2 uM (p = 0.004). Inorganic mercury (HgCl(2)) increased IL-4 only at concentrations 10-20 times higher than CH(3)Hg. These findings suggest a mechanism by which mercury could trigger or potentiate TH2 cytokine production in humans.

Mechanisms of cholinesterase inhibition by inorganic mercury

The poorly known mechanism of inhibition of cholinesterases by inorganic mercury (HgCl2) has been studied with a view to using these enzymes as biomarkers or as biological components of biosensors to survey polluted areas. The inhibition of a variety of cholinesterases by HgCl2 was investigated by kinetic studies, X-ray crystallography, and dynamic light scattering. Our results show that when a free sensitive sulfhydryl group is present in the enzyme, as in Torpedo californica acetylcholinesterase, inhibition is irreversible and follows pseudo-first-order kinetics that are completed within 1 h in the micromolar range. When the free sulfhydryl group is not sensitive to mercury (Drosophila melanogaster acetylcholinesterase and human butyrylcholinesterase) or is otherwise absent (Electrophorus electricus acetylcholinesterase), then inhibition occurs in the millimolar range. Inhibition follows a slow binding model, with successive binding of two mercury ions to the enzyme surface. Binding of mercury ions has several consequences: reversible inhibition, enzyme denaturation, and protein aggregation, protecting the enzyme from denaturation. Mercury-induced inactivation of cholinesterases is thus a rather complex process. Our results indicate that among the various cholinesterases that we have studied, only Torpedo californica acetylcholinesterase is suitable for mercury detection using biosensors, and that a careful study of cholinesterase inhibition in a species is a prerequisite before using it as a biomarker to survey mercury in the environment.

FK506 Controls CD40L-Induced Systemic Autoimmunity in Mice

Autoimmunity results from loss of mechanisms controlling self-reactivity. Autoimmune disorders play an increasingly important role and CD40-CD40 ligand (CD40L) interaction on immunocompentent cells is able to break established immunotolerance. To study the effects of the calcineurin-inhibitor FK506 on CD40L-induced systemic autoimmunity, CD40L transgenic (tg) mice, which spontaneously develop a mixed connective tissue-like disease, were treated with FK506 after onset of overt autoimmunity. Interestingly, FK506-treated CD40L tg mice showed significantly reduced autoimmune dermatitis scores and markedly decreased numbers of lesional infiltrating leukocytes. This finding was associated with diminished lymphadenopathy induced by FK506 treatment. Furthermore, FK506 suppressed the development of cytotoxic/autoreactive CD8(+) T cells as evidenced by the reduced expression of T cell activation markers in treated CD40L tg mice. Importantly, FK506 induced a significant reduction in autoantibody titers in the serum of CD40L tg animals. As CD40L tg mice develop nephritis leading to loss of renal function proteinuria was determined after FK506 injections. Notably, FK506 treatment re-established renal function as indicated by significantly reduced uric protein concentrations of treated CD40L tg mice. Together, these findings show the beneficial therapeutic effects of FK506 for the treatment of CD40L-induced autoimmunity. Additionally, these results demonstrate that FK506 is able to suppress ongoing severe autoimmune responses.