Imatinib mesylate selectively impairs expansion of memory cytotoxic T cells without affecting the control of primary viral infections

Imatinib mesylate (imatinib) is a potent inhibitor of defined tyrosine kinases (TKs) and is effective in the treatment of malignancies characterized by constitutive activation of these TKs such as chronic myeloid leukemia and gastrointestinal stromal tumors. TKs also play an important role in T-cell receptor (TCR) signal transduction. Inhibitory as well as stimulating effects of imatinib on T cells and dendritic cells have been described. Here, we analyzed the effects of imatinib treatment on antiviral immune responses in vivo. Primary cytotoxic T-cell (CTL) responses were not impaired in imatinib-treated mice after infection with lymphocytic choriomeningitis virus (LCMV) or after immunization with a tumor cell line expressing LCMV glycoprotein (LCMV-GP). Similarly, neutralizing antibody responses to vesicular stomatitis virus (VSV) were not affected. In contrast, secondary expansion of LCMV-specific memory CTLs was reduced in vitro and in vivo, resulting in impaired protection against reinfection. In addition, imatinib treatment delayed the onset of diabetes in a CTL-induced diabetes model. In summary, imatinib treatment in vivo selectively inhibits the expansion of antigen-experienced memory CTLs without affecting primary T- or B-cell responses. Therefore, imatinib may be efficacious in the suppression of CTL-mediated immunopathology in autoimmune diseases without the risk of acquiring viral infections.

Norepinephrine infusion with and without alpha-adrenergic blockade by phentolamine increases salivary alpha amylase in healthy men

BACKGROUND: Mental stress reliably induces increases in salivary alpha amylase (sAA), a suggested surrogate marker for sympathetic nervous system (SNS) reactivity. While stress-induced sAA increases correlate with norepinephrine (NE) secretion, a potential mediating role of noradrenergic mechanisms remains unclear. In this study, we investigated for the first time in humans whether a NE-stress-reactivity mimicking NE-infusion with and without alpha-adrenergic blockade by phentolamine would induce changes in sAA. METHODS: In a single-blind placebo-controlled within-subjects design, 21 healthy men (29-66 years) took part in three different experimental trials varying in terms of substance infusion with a 1-min first infusion followed by a 15-min second infusion: saline-infusion (trial-1), NE-infusion (5 μg/min) without alpha-adrenergic blockade (trial-2), and with phentolamine-induced non-selective blockade of alpha1- and alpha2-adrenergic receptors (trial-3). Saliva samples were collected immediately before, during, and several times after substance infusion in addition to blood pressure and heart rate readings. RESULTS: Experimental trials significantly differed in sAA reactivity to substance-infusion (p=.001) with higher sAA reactivity following NE-infusion with (trial-3; p=.001) and without alpha-adrenergic-blockade (trial-2; p=.004) as compared to placebo-infusion (trial-1); sAA infusion reactivity did not differ between trial-2 and trial-3 (p=.29). Effective phentolamine application was verified by blood pressure and heart rate infusion reactivity. Salivary cortisol was not affected by NE, either with or without alpha-adrenergic-blockade. CONCLUSIONS: We found that NE-infusion stimulates sAA secretion, regardless of co-administered non-selective alpha-adrenergic blockade by phentolamine, suggesting that the mechanism underlying stress-induced sAA increases may involve NE.

Effects of catecholamines on hepatic and skeletal muscle mitochondrial respiration after prolonged exposure to faecal peritonitis in pigs

Use of norepinephrine to increase blood pressure in septic animals has been associated with increased efficiency of hepatic mitochondrial respiration. The aim of this study was to evaluate whether the same effect could be reproduced in isolated hepatic mitochondria after prolonged in vivo exposure to faecal peritonitis. Eighteen pigs were randomized to 27 h of faecal peritonitis and to a control condition (n = 9 each group). At the end, hepatic mitochondria were isolated and incubated for one hour with either norepinephrine or placebo, with and without pretreatment with the specific receptor antagonists prazosin and yohimbine. Mitochondrial state 3 and state 4 respiration were measured for respiratory chain complexes I and II, and state 3 for complex IV using high-resolution respirometry, and respiratory control ratios were calculated. Additionally, skeletal muscle mitochondrial respiration was evaluated after incubation with norepinephrine and dobutamine with and without the respective antagonists (atenolol, propranolol and phentolamine for dobutamine). Faecal peritonitis was characterized by decreasing blood pressure and stroke volume, and maintained systemic oxygen consumption. Neither faecal peritonitis nor any of the drugs or drug combinations had measurable effects on hepatic or skeletal muscle mitochondrial respiration. Norepinephrine did not improve the efficiency of complex I- and complex II-dependent isolated hepatic mitochondrial respiration [respiratory control ratio (RCR) complex I: 5.6 ± 5.3 (placebo) vs. 5.4 ± 4.6 (norepinephrine) in controls and 2.7 ± 2.1 (placebo) vs. 2.9 ± 1.5 (norepinephrine) in septic animals; RCR complex II: 3.5 ± 2.0 (placebo) vs. 3.5 ± 1.8 (norepinephrine) in controls; 2.3 ± 1.6 (placebo) vs. 2.2 ± 1.1 (norepinephrine) in septic animals]. Prolonged faecal peritonitis did not affect either hepatic or skeletal muscle mitochondrial respiration. Subsequent incubation of isolated mitochondria with norepinephrine and dobutamine did not significantly influence their respiration.

Insulin resistance in mice lacking neuronal nitric oxide synthase is related to an alpha-adrenergic mechanism

BACKGROUND: nitric oxide (NO) plays an important role in the regulation of cardiovascular and glucose homeostasis. Mice lacking the gene encoding the neuronal isoform of nitric oxide synthase (nNOS) are insulin-resistant, but the underlying mechanism is unknown. nNOS is expressed in skeletal muscle tissue where it may regulate glucose uptake. Alternatively, nNOS driven NO synthesis may facilitate skeletal muscle perfusion and substrate delivery. Finally, nNOS dependent NO in the central nervous system may facilitate glucose disposal by decreasing sympathetic nerve activity. METHODS: in nNOS null and control mice, we studied whole body glucose uptake and skeletal muscle blood flow during hyperinsulinaemic clamp studies in vivo and glucose uptake in skeletal muscle preparations in vitro. We also examined the effects of alpha-adrenergic blockade (phentolamine) on glucose uptake during the clamp studies. RESULTS: as expected, the glucose infusion rate during clamping was roughly 15 percent lower in nNOS null than in control mice (89 (17) vs 101 (12) [-22 to -2]). Insulin stimulation of muscle blood flow in vivo, and intrinsic muscle glucose uptake in vitro, were comparable in the two groups. Phentolamine, which had no effect in the wild-type mice, normalised the insulin sensitivity in the mice lacking the nNOS gene. CONCLUSIONS: insulin resistance in nNOS null mice was not related to defective insulin stimulation of skeletal muscle perfusion and substrate delivery or insulin signaling in the skeletal muscle cell, but to a sympathetic alpha-adrenergic mechanism.

Effects of clinically used antioxidants in experimental pneumococcal meningitis

Reactive oxygen intermediates mediate brain injury in bacterial meningitis. Several antioxidant drugs are clinically available, including N-acetylcysteine (NAC), deferoxamine (DFO), and trylizad-mesylate (TLM). The present study evaluated whether these antioxidants are beneficial in a model of pneumococcal meningitis. Eleven-day-old rats were infected intracisternally with Streptococcus pneumoniae and randomized to intraperitoneal treatment every 8 h with NAC (200 mg/kg), DFO (100 mg/kg), TLM (10 mg/kg), or saline (250 microL). TLM-treated animals showed a significantly reduced mortality compared with controls (P<.03). Meningitis led to extensive cortical injury at 22+/-2.2 h after infection (median, 14. 6% of cortex; range, 0-61.1%). Injury was significantly (P<.01) reduced to 1.1% (range, 0-34.6%) by NAC, to 2.3% (range, 0-19.6%) by DFO, and to 0.2% (range, 0-36.9%) by TLM (the difference was not significant among the 3 groups). None of the drugs reduced hippocampal injury. Thus, several clinically used antioxidants reduced cortical injury in experimental pneumococcal meningitis.

Leukaemia and pregnancy

In summary, the management of women diagnosed with leukaemia in pregnancy needs an interdisciplinary approach, including a careful oncological work-up as well as close monitoring of the pregnancy until delivery and beyond. Patients with acute leukaemias normally must receive anti-leukaemic treatment at full dosage prior to delivery, except for selected women diagnosed very close to term. Treatment should be avoided in the first trimester. The prognosis of pregnant women with acute leukaemia corresponds to that of an age-matched and diagnosis-matched non-pregnant cohort of patients, provided appropriate treatment is given. If given as of the second trimester, the typical chemotherapy regimes used for acute leukaemias imply acceptable acute toxicities to the fetus, with a somewhat increased risk of premature birth or developmental retardation, but no clear evidence of late sequelae in children and adolescents who were exposed to cytostatic agents whilst in utero. In chronic leukaemias and MDS, treatment may often be delayed until after delivery. In CML targeted therapy with imatinib mesylate is safe as of the second trimester, and possibly even before. Obstetric care and monitoring of women with leukaemia are essential throughout the pregnancy to ensure the best possible outcome for mother and child.

Acute Stress Reduces Wound-Induced Activation of Microbicidal Potential of Ex Vivo Isolated Human Monocyte-Derived Macrophages

Background Psychological stress delays wound healing but the precise underlying mechanisms are unclear. Macrophages play an important role in wound healing, in particular by killing microbes. We hypothesized that (a) acute psychological stress reduces wound-induced activation of microbicidal potential of human monocyte-derived macrophages (HMDM), and (b) that these reductions are modulated by stress hormone release. Methods Fourty-one healthy men (mean age 35±13 years) were randomly assigned to either a stress or stress-control group. While the stress group underwent a standardized short-term psychological stress task after catheter-induced wound infliction, stress-controls did not. Catheter insertion was controlled. Assessing the microbicidal potential, we investigated PMA-activated superoxide anion production by HMDM immediately before and 1, 10 and 60 min after stress/rest. Moreover, plasma norepinephrine and epinephrine and salivary cortisol were repeatedly measured. In subsequent in vitro studies, whole blood was incubated with norepinephrine in the presence or absence of phentolamine (norepinephrine blocker) before assessing HMDM microbicidal potential. Results Compared with stress-controls, HMDM of the stressed subjects displayed decreased superoxide anion-responses after stress (p’s <.05). Higher plasma norepinephrine levels statistically mediated lower amounts of superoxide anion-responses (indirect effect 95% CI: 4.14–44.72). Norepinephrine-treated HMDM showed reduced superoxide anion-production (p<.001). This effect was blocked by prior incubation with phentolamine. Conclusions Our results suggest that acute psychological stress reduces wound-induced activation of microbicidal potential of HMDM and that this reduction is mediated by norepinephrine. This might have implications for stress-induced impairment in wound healing.

Extracellular Iron is a Modulator of the Differentiation of Osteoclast Lineage Cells.

Osteoclasts originate from the hematopoietic stem cell and share a differentiation pathway with the cells of the monocyte/macrophage lineages. Development and activation of osteoclasts, and as a consequence regulation of bone resorption, depend on two growth factors: macrophage colony-stimulating factor and receptor activator of NF-κB ligand. Furthermore, cell development and activity are modulated by a microenvironment composed of cytokines and growth factors and of the extracellular matrix. Membrane transporters are a means for cells to interact with their environment. Within this study, the expression of proteins regulating cellular iron homeostasis in osteoclast-like cells grown from bone marrow-derived progenitors was compared to the expression of this set of proteins by monocyte/macrophage lineage cells. In differentiating osteoclasts, levels of transcripts encoding transferrin receptor 1 and divalent metal transporter 1 (Slc11A2) were increased, while levels of transcripts encoding ferroportin (Slc40A1) and natural resistance-associated macrophage protein 1 (Slc11A1) were decreased. Supplementation of the culture media with exogenous iron led to an increase in the proliferation of osteoclast progenitor cells and to the expression of a macrophage-like phenotype, while the development of osteoclasts was reduced. Upon transfer of mature OC onto a CaP substrate, iron depletion of the medium with the Fe(3+)-chelator Deferoxamine Mesylate decreased CaP dissolution by ~30 %, which could be restored by addition of exogenous iron. During the 24 h of the assay, no effects were observed on total TRAP activity. The data demonstrate transcriptional regulation of the components of cellular iron transporters during OC development and suggests that iron homeostasis may contribute to fine-tuning of the RANKL-induced OC development.