Long-QT-Syndrom als Differenzialdiagnose einer Grand-Mal-Epilepsie

A 24-year-old female with a history of epileptic seizures was admitted after prolonged cardiac resuscitation. The clinical course together with additional examinations led to the diagnosis of severe hypoxic cerebral damage, with poor prognosis for neurological outcome. In her initial ECG, as in the ECGs of several family members, QT prolongation was diagnosed. Meticulous history taking and ensuing genetic analysis led to the diagnosis of familial long QT syndrome (LQTS) with a mutation in the LQT-2 gene (HERG). In retrospect, the previous seizure episodes have to be considered cardiac syncopes. Two family members had previously died suddenly, and ECG and genetic analysis revealed that a total of eight family members were affected. These relatives were prophylactically treated with beta blockers or supplied with automated implantable cardioverter defibrillating devices. The literature concerning LQTS, diagnosis and prognosis of cerebral hypoxic damage, and differentiation between seizures and cardiac syncopes is discussed.

Improved high-capacity adenoviral vectors for high-level neuron-restricted gene transfer to the CNS

Adenovirus-based (Ad) vectors are used widely for experimental gene transfer to the CNS. Ad transduce many cell types including postmitotic neurons. However, their use for CNS gene transfer is limited due to the host immune response elicited. Furthermore, the extensive distribution of the primary cellular receptor for Ad, the coxsackievirus and adenovirus receptor (CAR), allows adenoviral vectors to infect a broad range of host cells which may be disadvantageous in tissues with various different cell types, like the CNS. The use of tissue-specific promoters allows for neuron-restricted gene expression, even though gene expression driven by these promoters is often very weak. Accordingly, increased transgene expression levels from viral transcription units are needed in order to improve the overall performance of Ad vectors. We designed a high-capacity Ad vector (HC-Ad) that allows for high-level, neuron-restricted transgene expression and shows no obvious signs of immunogenicity or toxicity in the mouse brain.

Regulation of GDNF and its receptor components GFR-alpha1, -alpha2 and Ret during development and in the mature retino-collicular pathway

The development of the retino-tectal projection as part of the central visual pathway is accomplished around postnatal day (P) 10-14 in rodents, and trophic factors are important for topographic refinement of this projection. Emerging data indicate that GDNF may influence synaptic plasticity of this projection. To date, maturation-dependent kinetics of GDNF release and expression and biological function of single GDNF receptors along the retino-collicular pathway are ill-defined. Here, we examined mRNA and protein expression of GDNF and its multicomponent receptor complex in the retina and superior colliculus (SC) during postnatal development of the rat visual system, and after optic nerve (ON) injury by RT-PCR, immunoblotting and immunofluorescence. Stable mRNA transcription of GDNF and its receptors GFR-alpha1, -alpha2 and Ret was found in retina and SC throughout development into adulthood and after ON transection. Expression of GDNF protein increased during retinal development, declined in adulthood and was further reduced in injured retina. In the SC, GDNF peaked at P0, continuously declined with maturation, and was undetectable in the deafferentiated SC. GFR-alpha1 was abundant in retina and SC throughout, while GFR-alpha2 was not expressed. Since Ret was localized primarily to the vascular compartment, the receptor tyrosine kinase may play a minor role in neuronal GDNF signaling. In summary, we provide evidence for GDNF as survival and guidance factor during development of the retino-tectal projection with differential regulation in early and premature retina and SC. Postlesionally, midbrain targets do not induce GDNF, suggesting that retrograde GDNF is not essential for rescue of adult injured retinal ganglion cells (RGCs).

Identification of the end stage of scrapie using infected neural grafts

Although the formal pathogenesis of spongiform encephalopathies has been described in detail, it is not known whether the infectious agent targets primarily neurons, glial cells, or both. To address this question, we have transplanted transgenic embryonic neural tissue overexpressing PrP(c) into the forebrain of Prnp -knockout mice, and infected it with scrapie prions. After infection, grafts developed severe spongiform encephalopathy. As the infected hosts were not clinically affected, we were able to prolong the experiment and to assess changes in the graft over periods of time, which vastly exceeded the normal life span of scrapie-infected mice. Sequential contrast-enhanced magnetic resonance imaging (MRI) revealed progressive impairment of blood-brain barrier properties in infected grafts. However, loss of astrocytes was not observed. Subtotal neuronal loss occurred during the progression of the disease in the grafts, reactive astrocytes persisted until the terminal stage of disease. We conclude that scrapie encephalopathy primarily leads to neuronal death, while degeneration of astrocytes does not occur. Functional impairment of the blood-brain barrier suggests involvement of astrocytes and endothelial cells in the pathological process.

Differential regulation of Bax, Bcl-2, and Bcl-X proteins in focal cortical ischemia in the rat

Focal ischemia in the parietal cortex of the rat results in massive neuronal death in the infarct zone and penumbra between 12 hours and 6 days after photothrombosis. To examine a possible role of Bcl-2 family proteins in this process of cell death, we investigated their expression by immunoblot assays and immunocytochemistry, and correlated expression patterns with TUNEL as well as morphological signs indicative of apoptosis. In the center of the lesion Bax immunostaining was increased in many degenerating neurons between 4 hours and 3 days after the induction of photothrombosis. At all time points examined, Bcl-2 and Bcl-X protein levels were markedly reduced in injured neurons as compared to the unlesioned side. At the border of the ischemic lesion, two areas were distinguished: 1 - 2 days after induction of photothrombosis, pyknotic cells located immediately adjacent to the lesion core displayed nuclear Bcl-X and Bax immunoreactivity. In contrast, large, morphologically intact neurons located more towards the healthy brain parenchyma displayed an increase in cytoplasmic Bcl-2 and Bcl-X proteins. Double staining for each of the Bcl-2 family proteins and TUNEL revealed that DNA strand breaks and nuclear fragmentation seen in cells located in the lesion core were often associated with increased levels of Bax, but not with elevated Bcl-2 or Bcl-X protein levels, suggesting a role for Bax in the induction of apoptotic death in these cells. The upregulation of Bcl-2 and Bcl-X expression in surviving neurons close to the penumbra might reflect an active survival mechanism that protects these neurons from cell death following a sublethal insult.

Impaired development of the Harderian gland in mutant protein phosphatase 2A transgenic mice

Although Harderian glands are especially large in rodents, many features of this retroocular gland, including its development and function, are not well established. Protein phosphatase 2A (PP2A) is a family of heterotrimeric enzymes expressed in this gland. PP2A substrate specificity is determined by regulatory subunits with leucine 309 of the catalytic subunit playing a crucial role in the recruitment of regulatory subunits into the complex in vitro. Here we expressed an L309A mutant catalytic subunit in Harderian gland of transgenic mice. We found a delayed postnatal development and hypoplasia of the gland, causing enophthalmos. To determine why expression of the L309A mutant caused this phenotype, we determined the PP2A subunit composition. We found an altered subunit composition in the transgenic gland that was accompanied by pronounced changes of proteins regulating cell adhesion. Specifically, cadherin and beta-catenin were dramatically reduced and shifted to the cytosol. Furthermore, we found an inactivating phosphorylation of the cadherin-directed glycogen synthase kinase-3beta. In conclusion, the carboxy-terminal leucine L309 of the PP2A catalytic subunit determines PP2A heterotrimer composition in vivo. Moreover, our data demonstrate that PP2A subunit composition plays a crucial role in regulating cell adhesion and as a consequence in the development of the Harderian gland.

Simvastatin promotes heat shock protein 27 expression and Akt activation in the rat retina and protects axotomized retinal ganglion cells in vivo

Heat shock proteins (Hsps) are stress proteins that mediate protein stabilization in various tissues and protect cells from environmental stress. Novel evidence suggests that overexpression of the small heat shock protein 27 (Hsp27) in neurons protects against neurotoxic stimuli and may act as an inhibitor of neurodegeneration. Overexpression of Hsps has been achieved by different means including pharmacological induction. Here, we show that intravitreal injection of the 3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitor simvastatin induces Hsp27 expression in axotomized retinal ganglion cells (RGCs) and enhances RGC survival 7 and 14 days after optic nerve (ON) axotomy by 90% and 19%, respectively. The flavonoid quercetin inhibited Hsp27 induction and abrogated simvastatin-mediated neuroprotection. Simvastatin increased Akt phosphorylation in vivo, indicating that the PI3K/Akt pathway contributes to central nervous system (CNS) protective effects achieved. We propose the use of statins as a feasible approach to reduce lesion-induced CNS neuronal degeneration in vivo.

Statin-mediated protective effects in the central nervous system: general mechanisms and putative role of stress proteins

PURPOSE

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or "statins", are used as cholesterol-lowering agents worldwide. This review, focused on recent experimental and clinical data, summarizes general mechanisms of statin actions underlying neuroprotective effects in the central nervous system (CNS) and presents evidence for putative mechanisms involving heat shock proteins and the survival-related PI-3K/Akt pathway that may be beneficial for the treatment of neurological disorders.

METHODS

We carried out a medline search on statin actions, with respect to biochemical pathways and signal transduction on the one hand, and clinical studies in neurologic and retinal diseases on the other hand. Novel experimental data obtained in a rat model of axonal CNS injury were also included.

RESULTS

Statins exert multiple effects on endothelial function, cell proliferation, inflammatory response, immunological reactions, platelet function, and lipid oxidation. These "pleiotropic actions" are independent of cholesterol lowering and appear to be beneficial in the context of brain injury. Several mechanisms of statin actions underlying neuroprotective effects may also involve heat shock proteins and the survival-related PI-3K/Akt pathway.

CONCLUSIONS

Available data suggest that statins may be of potential therapeutic use in a variety of diseases of the CNS including ischemic stroke, Alzheimer's disease, multiple sclerosis and some forms of retinal and eye diseases. Before general recommendations can be made and specific therapeutic approaches can be developed, more reliable clinical data and studies are required, and possible side effects must be carefully evaluated.

Erythropoietin promotes regeneration of adult CNS neurons via Jak2/Stat3 and PI3K/AKT pathway activation

The cytokine hormone erythropoietin (EPO) has proved neuroprotective in CNS injury, and clinical trials for ischemic stroke are ongoing. The capability of EPO to restore postmitotic CNS architecture and function by fibre regeneration has not been examined. Here, we compared in vitro outgrowth capacity of adult retinal ganglion cells (RGCs) following optic nerve (ON) lesion in the presence and absence of EPO. Immediate EPO conditioning in vivo, or delayed EPO treatment of cultures with 10--10,000 IU rhEPO significantly increased numbers (2.66-fold) and length (8.31-fold) of newly generated neurites, without evoking rheological complications. EPO induced Stat3 phosphorylation in RGCs, and inhibition of Jak2/Stat3 abolished EPO-induced growth. EPO-facilitated neuritogenesis was paralleled by upregulation of Bcl-X(L), a Bcl-2 homologue capable of promoting RGC regeneration. The PI3K/Akt pathway was also involved in antiapoptotic and regeneration-enhancing EPO actions. In conclusion, EPO treatment may offer a unique dual-function strategy for neuroprotection and regeneration.

Initial DWI and ADC imaging may predict outcome in acute disseminated encephalomyelitis: report of two cases of brain stem encephalitis

Two young patients with acute disseminated encephalomyelitis (ADEM) of the brain stem are described. In spite of similar lesion sites in the brain stem, reaching from the upper medulla to the mesencephalon, the outcomes of the patients were very different: one made a full clinical recovery within three weeks while the other remained in a locked-in state more than a year after the disease episode. Both patients also differed in magnetic resonance imaging (MRI) findings on admission. The patient who remained in a locked-in state had pathological diffusion weighted imaging (DWI) scans and decreased apparent diffusion coefficient maps initially, with severe tissue destruction on follow up computed tomography, while the patient who recovered fully showed initially increased apparent diffusion coefficient values and almost complete resolution of MRI changes on follow up. Thus a comparison of these two cases may indicate differences in the underlying pathology in ADEM (vasogenic v cytotoxic oedema) that may be crucial for estimating tissue damage and clinical outcome.

[Procalcitonin as a marker for severe sepsis in an immunosuppressed patient]

A 22 year old female was admitted to the emergency department with high fever up to 41,5 degrees C, tachycardia, and arterial hypotension. Clinically, she presented with bilateral pulmonary coarse crackles. Diagnosis on admission was pneumonia with septic shock. Intriguingly, procalcitonin (PCT) was increased early, reaching up to 435 ng/mL, while C-reactive protein levels were only moderately increased, with several days delay. The sepsis was originated from a multi-resistant pseudomonas aeruginosa pneumonia. Remarkably, the course of PCT levels reflected the severity of septic shock in that it paralleled noradrenaline demand. Ten months previously, the patient had been diagnosed with acute disseminated brainstem encephalitis (ADEM), and had received two cycles of intravenous cyclophosphamide. Our case illustrates that PCT is an early marker for sepsis and it indicates that PCT may also be a valuable marker for the severity of sepsis in immunosuppressed patients.

Increased protein expression from adenoviral shuttle plasmids and vectors by insertion of a small chimeric intron sequence

Adenoviruses are widely used as gene transfer vehicles because they can be produced at high titers, they have a large transgene capacity, and can transduce both dividing and non-dividing cells. One disadvantage of adenoviral vectors is the narrow therapeutic window due to a dose-dependent humoral as well as a T-cell dependent host immune response directed against the transduced cells, that leads to a reduction of transgene expression with time. By increasing the levels of protein expression from transcription units, vector titres may be decreased without a significant loss of transgene expression. Introns are required for efficient expression of many protein coding genes. In addition, splicing signals are required for some genes in order to be translated. Therefore, a chimeric intron sequence was introduced at the 3' end of the transgenes to study its effect on protein expression from adenoviral vector constructs. Transfection of 293 cells with the adenoviral shuttle plasmids pMH4-EGFP-Int, pMH4-E314.7-Int, pMH4-BclX(L)-Int and pMH4-Luc-Int lead to a 1.8-20-fold increase in protein expression as compared to constructs lacking an intron. Injection of Ad-CMV-Luc-Int into the brain of C57Bl/6 mice results in an approximately three-fold increase of luciferase activity as compared to Ad-CMV-Luc. In conclusion, insertion of an intron sequence leads to a significant increase in transgene expression both in vitro and in vivo, thus allowing for reduction of the adenoviral vector dose used.

A novel primary culture technique for adult retina allows for evaluation of CNS axon regeneration in rodents

Unraveling the causes of regeneration failure in the adult injured CNS has remained a challenge in neurobiology. The notion that CNS neurons lose their regenerative potential during development has been challenged by the identification of several promoters of axon growth. Novel methods are required that allow to study and quantify interactions of molecular determinants, and to envisage future treatment applications. Here we report a novel, highly reproducible method for monitoring axonal regeneration of mature retinal ganglion cells (RGCs) in vitro. In contrast to earlier explantation methods, primary cultures derived from adult rodent retina are kept viable without growth factor supplements. Further, since intraretinal RGC axons remain unmyelinated, regeneration can be followed independently of non-permissive white matter compounds. Applying tracing techniques prior to retinal explantation, cell survival can be correlated to outgrowth activity on the single cell level. Following intervention with pharmacological, growth factor, or gene transfer treatments, retinal explants, and partially RGC neurites, can be processed for protein and gene expression analysis. This novel procedure will prove useful to get insight into complex cell survival and regeneration promoting cascades, and will complement in vivo strategies such as transgenic and knock out mouse models.

A patient with Marfan's syndrome and neurofibromatosis type 1 with polyneuropathy

Both Marfan's syndrome and neurofibromatosis type 1 are hereditary, autosomal dominant conditions. Here, we report the rare case of a patient fulfilling the clinical criteria for both diseases. In the absence of a family history of either of the two conditions, two independent de novo mutations are the most likely cause.

Excess Bcl-XL increases the intrinsic growth potential of adult CNS neurons in vitro

The regenerative potential of adult mammalian CNS neurons is limited. Recent data suggest that inactivation of major growth inhibitors may not suffice to induce robust regeneration from mature neurons unless the intrinsic growth state is modulated. To investigate a possible role of Bcl-XL for axon regeneration in the adult mammalian CNS, Bcl-XL was adenovirally overexpressed in severed rat RGCs. Bcl-XL overexpression in mature axotomized RGCs in vivo increased both numbers [3.10-fold (+/-0.20)] and cumulative length [6.72-fold (+/-0.47)] of neurites regenerated from retinal explants, and this effect was further pronounced in the central retina where specific and dense axoplasmatic transduction occurs. Similarly, delayed Bcl-XL gene transfer to explanted retinae 12-13 days after lesion increased the numbers and length of emanating neurites by a factor of 5.22 (+/-0.41) and 8.29 (+/-0.69), respectively. In vivo, intraretinal sprouting of unmyelinated RGC axons into the nerve fiber layer was increased. However, fiber ingrowth into the optic nerve remained sparse, likely due to myelin inhibitors and scar components. Therefore, Bcl-XL overexpression may enhance, but may not be sufficient to, restitute functional regeneration in the adult CNS. As assessed by cell quantification analysis, Bcl-XL overexpression rescued a higher proportion of RGCs in vivo than in vitro. Therefore, Bcl-XL is capable to induce both neuronal survival and axon regeneration, but these two processes appear to be differentially modified by distinct pathways in vivo.