Distinct glutaminyl cyclase expression in Edinger–Westphal nucleus, locus coeruleus and nucleus basalis Meynert contributes to pGlu-Aβ pathology in Alzheimer’s disease

Glutaminyl cyclase (QC) was discovered recently as the enzyme catalyzing the pyroglutamate (pGlu or pE) modification of N-terminally truncated Alzheimer’s disease (AD) Aβ peptides in vivo. This modification confers resistance to proteolysis, rapid aggregation and neurotoxicity and can be prevented by QC inhibitors in vitro and in vivo, as shown in transgenic animal models. However, in mouse brain QC is only expressed by a relatively low proportion of neurons in most neocortical and hippocampal subregions. Here, we demonstrate that QC is highly abundant in subcortical brain nuclei severely affected in AD. In particular, QC is expressed by virtually all urocortin-1-positive, but not by cholinergic neurons of the Edinger–Westphal nucleus, by noradrenergic locus coeruleus and by cholinergic nucleus basalis magnocellularis neurons in mouse brain. In human brain, QC is expressed by both, urocortin-1 and cholinergic Edinger–Westphal neurons and by locus coeruleus and nucleus basalis Meynert neurons. In brains from AD patients, these neuronal populations displayed intraneuronal pE-Aβ immunoreactivity and morphological signs of degeneration as well as extracellular pE-Aβ deposits. Adjacent AD brain structures lacking QC expression and brains from control subjects were devoid of such aggregates. This is the first demonstration of QC expression and pE-Aβ formation in subcortical brain regions affected in AD. Our results may explain the high vulnerability of defined subcortical neuronal populations and their central target areas in AD as a consequence of QC expression and pE-Aβ formation.     

Blockade of the mineralocorticoid receptor in healthy men: effects on experimentally induced panic symptoms, stress hormones, and cognition.

Animal studies have shown that blockade of central mineralocorticoid receptors (MR) has anxiolytic effects and impairs several aspects of cognitive function. No study to date assessed the effects of MR blockade on anxiety and cognitive function in humans. In the present study, 16 healthy young men were treated either with placebo or with 300 mg spironolactone, a MR-antagonist, at 1100, 1330, and 1630 hours in a balanced cross-over design with the two study conditions being 1 week apart. At 1500 hours, the panic symptoms provoking compound cholecystokinin-tetrapeptide (CCK-4) was administered i.v. on both occasions and panic symptoms were assessed. We measured plasma ACTH and cortisol between 1300 and 1900 hours and assessed cognitive function between 1800 and 1900 hours. CCK-4 elicited panic symptoms and increased ACTH and cortisol secretion in both conditions. Intensity of panic symptoms after CCK-4 was not different between spironolactone and placebo. Spironolactone significantly impaired selective attention and delayed recall of visuospatial memory, and diminished set shifting/mental flexibility on a trend level. Pretreatment with spironolactone led to higher baseline cortisol levels compared to placebo whereas no differences in stimulated cortisol, baseline ACTH, and stimulated ACTH emerged. Blockade of MR with spironolactone increases baseline cortisol secretion and impairs cognitive function but has no effect on experimentally induced panic symptoms in humans, for the study design and dosage of spironolactone used. The domains of cognitive function that are impaired after blockade of MR in men, that is, selective attention, visuospatial memory, and mental flexibility/set shifting appear to be remarkably similar to those described in animal studies.     

Evaluation of beneficial and adverse effects of glucocorticoids on a newly developed full-thickness skin model.

Glucocorticoids (GCs) are highly effective compounds widely used in the treatment of inflammatory diseases; however, they offer distinct adverse effects such as skin thinning in response to long-term topical treatment. Nevertheless it is difficult to deduce the safety of a newly synthesized compound from its structural formula. Efficient assay systems that measure beneficial and adverse effects are needed. In the present study the applicability of a three-dimensional full-thickness skin model (FTSM) is tested to display GC-induced effects regarding anti-inflammation and atrophy. It is shown that topical application of a commercial GC ointment suppresses the ultraviolet (UV)B induced induction of interleukin (IL)-6 and IL-8. Addition of purified betamethasone-17-valerate, prednicarbate and clobetasol-17-propionate to the culture medium for 14 days caused a reduction in the number of epidermal cell-layers corresponding to the atrophic risk found in vivo. Similarly, repeated topical application of five GC creams induced epidermal thinning. Evidence is given that the inhibitory effect on keratinocyte proliferation contributes to this effect. Furthermore, dermal thinning was monitored by measuring type I collagen synthesis; a decreased collagen synthesis similar to the in vivo situation is shown. The present study demonstrates the versatility of this FTSM in the validation of effectiveness and safety of GCs.     

Two cases of Mycobacterium microti derived tuberculosis in HIV-negative immunocompetent patients

We describe two cases of Mycobacterium microti infection causing pulmonary tuberculosis (TB) in HIV-seronegative immunocompetent patients in Germany. The isolates were identified as M. microti of the llama and vole types, according to spoligotype patterns. Our data demonstrate that M. microti can cause severe pulmonary TB in immunocompetent patients.     

Pathogenetic significance of venous hyperoxaemia in retinopathy of prematurity

Ten underweight newborns with severe retinopathy of prematurity (ROP) and 18 newborns with slight changes in the sense of ROP were compared with 66 healthy infants. The distribution of 13 possibly pathogenetically effective features in these 3 groups of patients was studied by means of variance analysis. The greatest significance resulted for multiple blood transfusions and exchange transfusions. From this it was concluded that the toxic oxygen effect on the immature retina was probably more dependent on the venous PO2 (determined by Hb concentration, O2-affinity, arterial PO2, and blood flow) than on the isolated arterial PO2.     

Induction of apoptosis of CD4+ T cells by immunomodulatory therapy of multiple sclerosis with glatiramer acetate

Glatiramer acetate (GA), a mixture of synthetic polypeptides, has beneficial effects on the clinical course and the MRI-defined disease activity of patients with multiple sclerosis (MS). In MS, evidence has been provided that the apoptosis of disease-relevant T cells is dysregulated. In this study, we investigated the effect of GA on T cell apoptosis, T cell activation, and cytokine profile of lymphocytes derived from 19 relapsing-remitting MS patients during the first year of GA therapy. Analysis of blood samples obtained every 6 weeks showed an increase in apoptotic T helper cells after 30 weeks of therapy. This effect remained until the end of the study and was accompanied by an increase in activated T cells and interleukin-4-producing lymphocytes. Thus, in addition to the established effect of GA on the cytokine network, GA-mediated immunomodulation might involve the apoptotic elimination of T helper cells.     

Optical coherence tomography in contact dermatitis and psoriasis

Optical coherence tomography (OCT) is a new noninvasive imaging technique. In this study, it was used for the investigation of contact dermatitis and psoriasis. In these common inflammatory skin diseases the value of OCT for quantification and monitoring of the changes in comparison with other bioengineering methods was evaluated. Repeated measurements were performed in healthy volunteers after experimental induction of irritant contact dermatitis and in patients with psoriasis. In the OCT images, the thickness of the epidermis and the signal attenuation coefficient in the upper dermis were evaluated. The changes were compared with measurements of transepidermal water loss, hydration, skin colour and surface roughness, and with high-frequency ultrasound measurements. In irritant dermatitis and psoriasis, thickening of the epidermis was detected and could be monitored over time. The light scattering in the upper dermis was lower than in healthy skin. This was interpreted to be due to the inflammation and oedema, leading to a less-dense arrangement of the collagen fibres. The changes in the OCT images did not significantly correlate with the changes shown by the other methods. OCT is an interesting tool for investigation of inflammatory skin diseases. It is a simple method for determination of epidermal thickness and therefore provides, in addition to other methods, information on the severity of the disease and on treatment effects.     

Ceramide induces mitochondrial activation and apoptosis via a Bax-dependent pathway in human carcinoma cells

The intracellular pathways leading to mitochondrial activation and subsequent cell death in the ceramide-mediated stress response have been intensively studied in recent years. Experimental evidence has been provided that ceramide-induced apoptosis is inhibited by overexpression of antiapoptotic proteins of the Bcl-2 family. However, the direct effect of proapoptotic gene products, e.g. Bax, on ceramide-induced death signalling has not yet been studied in detail. In the present work, we show by measurement of mitochondrial permeability transition, cytochrome c release, activation of caspase-3 and DNA fragmentation that ceramide-induced apoptosis is marginal in Bax-negative DU 145 cells. Reconstitution of Bax by generation of DU 145 cells stably expressing this proapoptotic factor, clearly enhanced ceramide-induced apoptosis at all levels of the mitochondrial signalling cascade. Using the broad-range caspase inhibitor zVAD-fmk and zDEVD-fmk, an inhibitor of caspase-3-like activities, we demonstrate that the ceramide-induced mitochondrial activation in Bax-transfected DU 145 cells is caspase-independent. On the other hand, apoptotic events located downstream of the mitochondria, e.g. DNA fragmentation, were shown to be caspase-dependent. This influence of Bax on ceramide-induced apoptosis was confirmed in another cellular system: whereas Bax-positive HCT116 wild type cells were very sensitive towards induction of cell death by C(2)-ceramide, sensitivity of Bax knock-out HCT116 cells was significantly reduced. Thus, we conclude that Bax is a key activator of ceramide-mediated death pathways.