Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous degenerative eye disease. Mutations at Arg135 of rhodopsin are associated with a severe form of autosomal dominant RP. This report presents evidence that Arg135 mutant rhodopsins (e.g., R135L, R135G, and R135W) are hyperphosphorylated and bind with high affinity to visual arrestin. Mutant rhodopsin recruits the cytosolic arrestin to the plasma membrane, and the rhodopsin-arrestin complex is internalized into the endocytic pathway. Furthermore, the rhodopsin-arrestin complexes alter the morphology of endosomal compartments and severely damage receptor-mediated endocytic functions. The biochemical and cellular defects of Arg135 mutant rhodopsins are distinct from those previously described for class I and class II RP mutations, and, hence, we propose that they be named class III. Impaired endocytic activity may underlie the pathogenesis of RP caused by class III rhodopsin mutations.
Jen-Zen Chuang, Carrie Vega, Wenjin Jun, Ching-Hwa Sung
Thrombolysis is widely used to intervene in acute ischemic stroke, but reestablishment of circulation may paradoxically initiate a reperfusion injury. Here we describe studies with mice lacking protein kinase Cδ (PKCδ) showing that absence of this enzyme markedly reduces reperfusion injury following transient ischemia. This was associated with reduced infiltration of peripheral blood neutrophils into infarcted tissue and with impaired neutrophil adhesion, migration, respiratory burst, and degranulation in vitro. Total body irradiation followed by transplantation with bone marrow from PKCδ-null mice donors reduced infarct size and improved neurological outcome in WT mice, whereas marrow transplantation from WT donors increased infarction and worsened neurological scores in PKCδ-null mice. These results indicate an important role for neutrophil PKCδ in reperfusion injury and strongly suggest that PKCδ inhibitors could prove useful in the treatment of stroke.
Wen-Hai Chou, Doo-Sup Choi, Hong Zhang, Dezhi Mu, Tom McMahon, Viktor N. Kharazia, Clifford A. Lowell, Donna M. Ferriero, Robert O. Messing
Bone marrow stromal cells (MSCs) have the capability under specific conditions of differentiating into various cell types such as osteocytes, chondrocytes, and adipocytes. Here we demonstrate a highly efficient and specific induction of cells with neuronal characteristics, without glial differentiation, from both rat and human MSCs using gene transfection with Notch intracellular domain (NICD) and subsequent treatment with bFGF, forskolin, and ciliary neurotrophic factor. MSCs expressed markers related to neural stem cells after transfection with NICD, and subsequent trophic factor administration induced neuronal cells. Some of them showed voltage-gated fast sodium and delayed rectifier potassium currents and action potentials compatible with characteristics of functional neurons. Further treatment of the induced neuronal cells with glial cell line–derived neurotrophic factor (GDNF) increased the proportion of tyrosine hydroxylase–positive and dopamine-producing cells. Transplantation of these GDNF-treated cells showed improvement in apomorphine-induced rotational behavior and adjusting step and paw-reaching tests following intrastriatal implantation in a 6-hydroxy dopamine rat model of Parkinson disease. This study shows that a population of neuronal cells can be specifically generated from MSCs and that induced cells may allow for a neuroreconstructive approach.
Mari Dezawa, Hiroshi Kanno, Mikio Hoshino, Hirotomi Cho, Naoya Matsumoto, Yutaka Itokazu, Nobuyoshi Tajima, Hitoshi Yamada, Hajime Sawada, Hiroto Ishikawa, Toshirou Mimura, Masaaki Kitada, Yoshihisa Suzuki, Chizuka Ide
Uracil-DNA glycosylase (UNG) is involved in base excision repair of aberrant uracil residues in nuclear and mitochondrial DNA. Ung knockout mice generated by gene targeting are viable, fertile, and phenotypically normal and have regular mutation rates. However, when exposed to a nitric oxide donor, Ung–/– fibroblasts show an increase in the uracil/cytosine ratio in the genome and augmented cell death. After combined oxygen-glucose deprivation, Ung–/– primary cortical neurons have increased vulnerability to cell death, which is associated with early mitochondrial dysfunction. In vivo, UNG expression and activity are low in brains of naive WT mice but increase significantly after reversible middle cerebral artery occlusion and reperfusion. Moreover, major increases in infarct size are observed in Ung–/– mice compared with littermate control mice. In conclusion, our results provide compelling evidence that UNG is of major importance for tissue repair after brain ischemia.
Matthias Endres, Detlev Biniszkiewicz, Robert W. Sobol, Christoph Harms, Michael Ahmadi, Andreas Lipski, Juri Katchanov, Philipp Mergenthaler, Ulrich Dirnagl, Samuel H. Wilson, Andreas Meisel, Rudolf Jaenisch
Cortical spreading depression (CSD) is a propagating wave of neuronal and glial depolarization and has been implicated in disorders of neurovascular regulation such as stroke, head trauma, and migraine. In this study, we found that CSD alters blood-brain barrier (BBB) permeability by activating brain MMPs. Beginning at 3–6 hours, MMP-9 levels increased within cortex ipsilateral to the CSD, reaching a maximum at 24 hours and persisting for at least 48 hours. Gelatinolytic activity was detected earliest within the matrix of cortical blood vessels and later within neurons and pia arachnoid (≥3 hours), particularly within piriform cortex; this activity was suppressed by injection of the metalloprotease inhibitor GM6001 or in vitro by the addition of a zinc chelator (1,10-phenanthroline). At 3–24 hours, immunoreactive laminin, endothelial barrier antigen, and zona occludens-1 diminished in the ipsilateral cortex, suggesting that CSD altered proteins critical to the integrity of the BBB. At 3 hours after CSD, plasma protein leakage and brain edema developed contemporaneously. Albumin leakage was suppressed by the administration of GM6001. Protein leakage was not detected in MMP-9–null mice, implicating the MMP-9 isoform in barrier disruption. We conclude that intense neuronal and glial depolarization initiates a cascade that disrupts the BBB via an MMP-9–dependent mechanism.
Yasemin Gursoy-Ozdemir, Jianhua Qiu, Norihiro Matsuoka, Hayrunnisa Bolay, Daniela Bermpohl, Hongwei Jin, Xiaoying Wang, Gary A. Rosenberg, Eng H. Lo, Michael A. Moskowitz
Alzheimer disease (AD) is characterized by excessive deposition of amyloid β-peptides (Aβ peptides) in the brain. In the nonamyloidogenic pathway, the amyloid precursor protein (APP) is cleaved by the α-secretase within the Aβ peptide sequence. Proteinases of the ADAM family (adisintegrin and metalloproteinase) are the main candidates as physiologically relevant α-secretases, but early lethality of knockout animals prevented a detailed analysis in neuronal cells. To overcome this restriction, we have generated transgenic mice that overexpress either ADAM10 or a catalytically inactive ADAM10 mutant. In this report we show that a moderate neuronal overexpression of ADAM10 in mice transgenic for human APP[V717I] increased the secretion of the neurotrophic soluble α-secretase–released N-terminal APP domain (APPsα), reduced the formation of Aβ peptides, and prevented their deposition in plaques. Functionally, impaired long-term potentiation and cognitive deficits were alleviated. Expression of mutant catalytically inactive ADAM10 led to an enhancement of the number and size of amyloid plaques in the brains of double-transgenic mice. The results provide the first in vivo evidence for a proteinase of the ADAM family as an α-secretase of APP, reveal activation of ADAM10 as a promising therapeutic target, and support the hypothesis that a decrease in α-secretase activity contributes to the development of AD.
Rolf Postina, Anja Schroeder, Ilse Dewachter, Juergen Bohl, Ulrich Schmitt, Elzbieta Kojro, Claudia Prinzen, Kristina Endres, Christoph Hiemke, Manfred Blessing, Pascaline Flamez, Antoine Dequenne, Emile Godaux, Fred van Leuven, Falk Fahrenholz
Recently, pathological prion protein PrPSc, the putative key constituent of infectious agents causing transmissible spongiform encephalopathies (TSEs), was found in muscles of rodents experimentally infected with scrapie and in patients with Creutzfeldt-Jakob disease (CJD). For the assessment of risk scenarios originating from these findings (e.g., alimentary transmission of pathogens associated with bovine spongiform encephalopathy [BSE] and chronic wasting disease [CWD] via tainted beef and game or iatrogenic dissemination of CJD agent through contaminated surgical instruments) more detailed information about the time course of PrPSc accumulation in muscles at preclinical and clinical stages of incubation is needed. Here we show that PrPSc in muscles of hamsters fed with scrapie can be detected prior to the onset of clinical symptoms, but that the bulk of PrPSc was deposited late in clinical disease. Additionally, regarding the question of how muscles become invaded, we report on the intramuscular location of PrPSc and substantial indications for centrifugal spread of infection from spinal motor neurons to myofibers. Our findings in a well-established animal model for TSEs contribute to a better assessment of the risks for public health emanating from “Prions in skeletal muscle” and provide new insights into the pathophysiological spread of TSE agents through the body.
Achim Thomzig, Walter Schulz-Schaeffer, Christine Kratzel, Jessica Mai, Michael Beekes
Control of cancer, neuropathic, and postoperative pain is frequently inadequate or compromised by debilitating side effects. Inhibition or removal of certain nociceptive neurons, while retaining all other sensory modalities and motor function, would represent a new therapeutic approach to control severe pain. The enriched expression of transient receptor potential cation channel, subfamily V, member 1 (TRPV1; also known as the vanilloid receptor, VR1) in nociceptive neurons of the dorsal root and trigeminal ganglia allowed us to test this concept. Administration of the potent TRPV1 agonist resiniferatoxin (RTX) to neuronal perikarya induces calcium cytotoxicity by opening the TRPV1 ion channel and selectively ablates nociceptive neurons. This treatment blocks experimental inflammatory hyperalgesia and neurogenic inflammation in rats and naturally occurring cancer and debilitating arthritic pain in dogs. Sensations of touch, proprioception, and high-threshold mechanosensitive nociception, as well as locomotor function, remained intact in both species. In separate experiments directed at postoperative pain control, subcutaneous administration of RTX transiently disrupted nociceptive nerve endings, yielding reversible analgesia. In human dorsal root ganglion cultures, RTX induced a prolonged increase in intracellular calcium in vanilloid-sensitive neurons, while leaving other, adjacent neurons unaffected. The results suggest that nociceptive neuronal or nerve terminal deletion will be effective and broadly applicable as strategies for pain management.
Laszlo Karai, Dorothy C. Brown, Andrew J. Mannes, Stephen T. Connelly, Jacob Brown, Michael Gandal, Ofer M. Wellisch, John K. Neubert, Zoltan Olah, Michael J. Iadarola
Eleven studies now report significant associations between schizophrenia and certain haplotypes of single-nucleotide polymorphisms in the gene encoding dysbindin-1 at 6p22.3. Dysbindin-1 is best known as dystrobrevin-binding protein 1 (DTNBP1) and may thus be associated with the dystrophin glycoprotein complex found at certain postsynaptic sites in the brain. Contrary to expectations, however, we found that when compared to matched, nonpsychiatric controls, 73–93% of cases in two schizophrenia populations displayed presynaptic dysbindin-1 reductions averaging 18–42% (P = 0.027–0.0001) at hippocampal formation sites lacking neuronal dystrobrevin (i.e., β-dystrobrevin). The reductions, which were not observed in the anterior cingulate of the same schizophrenia cases, occurred specifically in terminal fields of intrinsic, glutamatergic afferents of the subiculum, the hippocampus proper, and especially the inner molecular layer of the dentate gyrus (DGiml). An inversely correlated increase in vesicular glutamate transporter-1 (VGluT-1) occurred in DGiml of the same schizophrenia cases. Those changes occurred without evidence of axon terminal loss or neuroleptic effects on dysbindin-1 or VGluT-1. Our findings indicate that presynaptic dysbindin-1 reductions independent of the dystrophin glycoprotein complex are frequent in schizophrenia and are related to glutamatergic alterations in intrinsic hippocampal formation connections. Such changes may contribute to the cognitive deficits common in schizophrenia.
Konrad Talbot, Wess L. Eidem, Caroline L. Tinsley, Matthew A. Benson, Edward W. Thompson, Rachel J. Smith, Chang-Gyu Hahn, Steven J. Siegel, John Q. Trojanowski, Raquel E. Gur, Derek J. Blake, Steven E. Arnold
Neural stem/progenitor cell (NSPC) migration toward sites of damaged central nervous system (CNS) tissue may represent an adaptive response for the purpose of limiting and/or repairing damage. Little is known of the mechanisms responsible for this migratory response. We constructed a cDNA library of injured mouse forebrain using subtractive suppression hybridization (SSH) to identify genes that were selectively upregulated in the injured hemisphere. We demonstrate that stem cell factor (SCF) mRNA and protein are highly induced in neurons within the zone of injured brain. Additionally, the SCF receptor c-kit is expressed on NSPCs in vitro and in vivo. Finally, we demonstrate that recombinant SCF induces potent NSPC migration in vitro and in vivo through the activation of c-kit on NSPCs. These data suggest that the SCF/c-kit pathway is involved in the migration of NSPCs to sites of brain injury and that SCF may prove useful for inducing progenitor cell recruitment to specific areas of the CNS for cell-based therapeutic strategies.
Lixin Sun, Jeongwu Lee, Howard A. Fine