Induced arginine transport via cationic amino acid transporter‐1 is necessary for human T‐cell proliferation

Availability of the semiessential amino acid arginine is fundamental for the efficient function of human T lymphocytes. Tumor‐associated arginine deprivation, mainly induced by myeloid‐derived suppressor cells, is a central mechanism of tumor immune escape from T‐cell‐mediated antitumor immune responses. We thus assumed that transmembranous transport of arginine must be crucial for T‐cell function and studied which transporters are responsible for arginine influx into primary human T lymphocytes. Here, we show that activation via CD3 and CD28 induces arginine transport into primary human T cells. Both naïve and memory CD4⁺ T cells as well as CD8⁺ T cells specifically upregulated the human cationic amino acid transporter‐1 (hCAT‐1), with an enhanced and persistent expression under arginine starvation. When hCAT‐1 induction was suppressed via siRNA transfection, arginine uptake, and cellular proliferation were impaired. In summary, our results demonstrate that hCAT‐1 is a key component of efficient T‐cell activation and a novel potential target structure to modulate adaptive immune responses in tumor immunity or inflammation.     

Thrombotische Mikroangiopathie (TMA): neue Aspekte

This article describes new aspects and insights into the epidemiology, pathogenesis and typical morphology of kidney involvement in thrombotic microangiopathy (TMA). TMA comprises a spectrum of microvascular thrombosis syndromes associated with multiple pathogenic factors, e.g. typical and atypical hemolytic uremic syndrome (HUS), thrombotic thrombopenic purpura (TTP), malignant hypertension, drugs and systemic autoimmune diseases and antibody mediated rejection. Particular emphasis is placed on new pathophysiological insights into the development of TMA in the various settings. In addition, new options in the therapeutic management of TMA in atypical HUS are discussed. The pathogenesis of TMA in atypical HUS primarily involves inherited or acquired deficiencies and disorders of the complement system. With eculizumab a promising new therapeutic option has recently been discovered. In HUS/TTP the kidneys show characteristic vascular changes due to endothelial damage so that the TMA should be clinically and morphologically differentiated from other diseases. Recent genetic and molecular studies shed more light on the pathogenesis of TMA in atypical HUS, e.g. disorders of various aspects of the complement system and in TTP, e.g. VWF regulation by ADAMTS 13, which are also helpful in the differential diagnosis.     

Breath biomarkers for lung cancer detection and assessment of smoking related effects — confounding variables,influence of normalization and statistical algorithms

BackgroundUp to now, none of the breath biomarkers or marker sets proposed for cancer recognition has reached clinical relevance. Possible reasons are the lack of standardized methods of sampling, analysis and data processing and effects of environmental contaminants.MethodsConcentration profiles of endogenous and exogenous breath markers were determined in exhaled breath of 31 lung cancer patients, 31 smokers and 31 healthy controls by means of SPME-GC-MS. Different correcting and normalization algorithms and a principal component analysis were applied to the data.ResultsDifferences of exhalation profiles in cancer and non-cancer patients did not persist if physiology and confounding variables were taken into account. Smoking history, inspired substance concentrations, age and gender were recognized as the most important confounding variables. Normalization onto PCO₂ or BSA or correction for inspired concentrations only partially solved the problem. In contrast, previous smoking behaviour could be recognized unequivocally.ConclusionExhaled substance concentrations may depend on a variety of parameters other than the disease under investigation. Normalization and correcting parameters have to be chosen with care as compensating effects may be different from one substance to the other. Only well-founded biomarker identification, normalization and data processing will provide clinically relevant information from breath analysis.     

Effects of morphine on oedema and tissue concentration of nerve growth factor in experimental inflammation of the rat paw

Injection of carrageenan (1 mg) into the rat hind paw caused a time-dependent increase in paw volume that was maximal 3 h after injection. At this time, the concentration of nerve growth factor (NGF) in the skin of the inflamed paw was more than twofold higher than in the contralateral, non-inflamed paw. Treatment of rats with indomethacin reduced inflammatory oedema by 57%, morphine treatment attenuated oedema by 62%. While indomethacin had no statistically significant effect on the concentration of NGF in the skin of inflamed paws, morphine attenuated the NGF response by 24.2% in a naloxone reversible manner. These data suggest that drug-induced inhibition of inflammatory oedema is not predictive of its effect on an inflammation-induced rise in tissue NGF. Furthermore, our results confirm and extend previous observations suggesting an anti-inflammatory activity of morphine.     

Physiologic-pharmacologic interpretation of the constants in the Hill equation for neuromuscular block: a hypothesis

Neuromuscular block (NMB) is simulated in pharmacodynamic models using the concentration of a muscle relaxant (MR) in the effect compartment and two constants, and IC50. No physiologic or pharmacologic interpretation is offered for either constant. We desired to explore whether the constants are properties of the muscle or the MR and to simulate NMB when the MR binds to two sites at a single receptor. Based on steady state conditions, we defined receptor occupancy using the equilibrium dissociation constants. Two concepts are introduced: threshold occupancy and occupancy at half-maximal NMB, Occ_NMB50. Threshold occupancy is defined as receptor occupancy at the motor end plate of a muscle fiber when the fiber fails to contract and Occ_NMB50 as the median threshold occupancy. NMB may be simulated as a function of either the concentration of the muscle relaxant or receptor occupancy. We suggest: (1) The distribution of threshold occupancies is an intrinsic property of a muscle and is characterized by two constants (_O and Occ_NMB50); (2) _O is numerically equal to the slope of the NMB vs. concentration curves and is independent of the equilibrium dissociation constants. IC50 is codetermined by Occ_NMB50 and by the equilibrium dissociation constants. (3) Binding of a muscle relaxant to the second binding site influences only the estimate of IC50 but not .     

ATP release in human kidney cortex and its mitogenic effects in visceral glomerular epithelial cells

BACKGROUND: In chronic renal failure the sympathetic nervous system is activated. Sympathetic cotransmitters released within the kidney may contribute to the progression of renal disease through receptor-mediated proliferative mechanisms. METHODS: In human renal cortex electrical stimulation induced adenosine 5'-triphosphate (ATP; luciferin-luciferase-assay) and norepinephrine (HPLC) release was measured. ATP release also was induced by alpha1- and alpha2-adrenergic agonists. [3H]-thymidine uptake was tested in human visceral glomerular epithelial cells (vGEC) and mitogen-activated protein kinase (MAPK42/44) activation in vGEC and kidney cortex. The involved P2-receptors were characterized pharmacologically and by RT-PCR. RESULTS: Sympathetic nerve stimulation and alpha-adrenergic agonists induced release of ATP from human kidney cortex. Seventy-five percent of the ATP released originated from non-neuronal sources, mainly through activation of alpha2-adrenergic receptors. ATP (1 to 100 micromol/L) and related nucleotides (1 to 100 micromol/L) increased [3H]-thymidine uptake. The adenine nucleotides ATP, ATPgammaS, ADP and ADPbetaS were about equally potent. UTP, UDP and alpha,beta-methylene ATP had no effect. ATP, ADPbetaS but not alpha,beta-methylene ATP activated MAPK42/44. ATP induced MAPK42/44 activation, and [3H]-thymidine uptake was abolished in the presence of the MAPK inhibitor PD 98059 (100 micromol/L). mRNA for P2X4,5,6,7 and P2Y1,2,4,6,11 were detected in human vGEC by RT-PCR. CONCLUSIONS: In human renal cortex, adrenergic stimulation releases ATP from neuronal and non-neuronal sources. ATP has mitogenic effects in vGEC and therefore the potential to contribute to progression in chronic renal disease. The pattern of purinoceptor agonist effects on DNA synthesis together with the mRNA expression suggests a major contribution of a P2Y1-like receptor.     

Intraperitoneal protein injection in the axolotl: the amphibian kidney as a novel model to study tubulointerstitial activation

BACKGROUND: A substantial body of experimental evidence suggests that protein loading causes activation of proximal tubular epithelial cells with consecutive interstitial fibrosis. These studies have mostly been performed using mammalian in vivo models of glomerular damage or tissue cultures of mammalian tubulointerstitial cells. The kidney of the axolotl contains not only closed nephrons, but also nephrons with ciliated peritoneal funnels called nephrostomes that have access to the peritoneal fluid. Injection of protein into the peritoneal cavity fails to expose closed nephrons to a protein load, but causes selective uptake and transient storage of proteins in tubular epithelial cells of nephrons with nephrostomes. The purpose of the present study was to determine whether (a) the axolotl kidney can be used as a model to assess protein uptake by tubular cells in vivo in the absence of glomerular damage, and (b) this is accompanied by any evidence of tubular epithelial cell activation and interstitial fibrosis. METHODS: Male and female axolotl (80 to 120 g of weight) were given a daily intraperitoneal injection of 1.5 mL endotoxin-free calf serum or saline as control. Kidneys were harvested after 4 or 10 days using perfusion fixation for light microscopy (fibrous tissue stain) and saline perfusion for immunohistochemistry (fibronectin, TGF-beta and collagen I). RESULTS: The findings document selective storage of protein and lipids, progressive with time, in proximal tubular epithelial cells of nephrons draining the coelomic cavity. In addition, progressive focal accumulation of fibrous tissue was noted around protein-storing tubules. Immunohistochemical staining demonstrated the presence of fibronectin and TGF-beta in the tubular epithelial cells and interstitial cells. CONCLUSION: The axolotl kidney provides a novel in vivo model to study tubulointerstitial activation and induction of interstitial fibrosis by protein loading. The findings are independent of alterations of glomerular function that may have potential confounding effects on peritubular hemodynamics, pO2, cell traffic, etc.     

The prediction of defibrillation outcome using a new combination of mean frequency and amplitude in porcine models of cardiac arrest

We estimated the predictive power with respect to defibrillation outcome of ventricular fibrillation (VF) mean frequency (FREQ), mean peak-to-trough amplitude (AMPL), and their combination. We examined VF electrocardiogram signals of 64 pigs from 4 different cardiac arrest models with different durations of untreated VF, different durations of cardiopulmonary resuscitation, and use of different drugs (epinephrine, vasopressin, N-nitro-L-arginine methyl ester, or saline placebo). The frequency domain was restricted to the range from 4.33 to 30 Hz. In the 10-s epoch between 20 and 10 s before the first defibrillation shock, FREQ and AMPL were estimated. We introduced the survival index (SI; 0.68 Hz(-1). FREQ + 12.69 mV(-1). AMPL) by use of multiple logistic regression. Kruskal-Wallis nonparametric one-way analysis was used to analyze the different porcine models for significant difference. The variables FREQ, AMPL, and SI were compared with defibrillation outcome by means of univariate logistic regression and receiver operating characteristic curves. SI increased predictive power compared with AMPL or FREQ alone, resulting in 89% sensitivity and 86% specificity. The probabilities of predicting defibrillation outcome for FREQ, AMPL, and SI were 0.85, 0.89 and 0.90, respectively. FREQ, AMPL, and SI values were not sensitive in regard to the four different cardiac arrest models but were significantly different for vasopressin and epinephrine animals. IMPLICATIONS: We present a retrospective data analysis to evaluate the predictive power of different ventricular fibrillation electrocardiogram variables in pigs with respect to defibrillation outcome. We showed that our combination of variables leads to an improved forecast, which may help to reduce harmful unsuccessful defibrillation attempts.     

Acute antimanic efficacy and safety of oxcarbazepine in an open trial with an on-off-on design

Rationale and Objectives:  Carbamazepine has shown reasonable antimanic properties, but its use has been limited because of enzyme-inducing effects. The keto-derivative oxcarbazepine (OXC) is very similar to carbamazepine, however, the metabolic pathway is different. OXC is not metabolized to the 10, 11–epoxide, which seems to be responsible for several undesirable side-effects of carbamazepine and furthermore OXC has less enzyme-inducing properties.
Methods:  In this non-random open label study, patients were treated with OXC for 14 days, crossed over to no OXC for 7 days, and then crossed back over to OXC for the remaining 14 days. OXC was titrated to a final dose in a range of 900–2100 mg due to individual response. Treatment success was defined as a reduction of the original Young Mania Rating Scale (YMRS) score of more than 50% at the end of study period.
Results:  Four of the 12 included patients (33%) met defined response criteria at the end of study period. Fifty percentage of the patients had to be prematurely excluded from the trial. The mean YMRS scores of the on-periods were obviously different from the off-period. Forty-two percentage of the patients experienced side-effects leading to premature discontinuation in two of 12 patients.
Conclusion:  Antimanic activity of OXC was demonstrated in this pilot study only for patients with mild or moderate manic symptoms. Further studies are encouraged to clarify OXC's role as mood-stabilizer and assess whether it has a profile similar to that of carbamazepine.     

Adding low-dose antidepressants to interferon alpha treatment for chronic hepatitis C improved psychiatric tolerability in a patient with schizoaffective psychosis

Treatment of chronic hepatitis C with interferon alpha (IFN-alpha) is relatively contraindicated in patients with psychiatric disorders because of possible severe psychiatric side effects. We report on a case of a female patient with a chronic schizoaffective psychosis, who was treated for 3 months with 3 x 3 mio IE IFN-alpha s.c./week because of a chronic hepatitis C (genotype 1b). Psychosis was stable with flupentixol monotherapy. After 2 months, she developed a severe depressive syndrome which lead to suicidal ideation. Until this time, she was without any antidepressive medication. Depressive symptoms disappeared after interferon therapy was stopped. Under prophylactic treatment with low-dose trimipramine (50 mg) or nefazodone (200 mg/day) therapy with IFN-alpha 3 x 3 mio IE/week was re-established after several months and again 2 years later adding ribavirin 1200 mg/day, a virustaticum. In contrast to the symptoms during monotherapy with IFN-alpha, during the time of both combination treatments, no psychiatric side effects occurred. While for ribavirin antidepressant effects are not known, we suppose that antidepressants may prevent changes in serotonergic or noradrenergic neurotransmission caused by IFN-alpha.