Sporadic inclusion body myositis - a myodegenerative disease or an inflammatory myopathy.

Sporadic inclusion body myositis (sIBM) is an insidious late-onset progressive myopathy that typically affects patients over the age of 50. Clinically, patients develop a characteristic pattern of weakness that affects the forearm flexors and knee extensors. Muscle biopsy, often utilized in the diagnosis, demonstrates a chronic myopathy with mixed pathologies harbouring intramyofiber protein inclusions and endomysial inflammation. The co-existence of these pathologic features (that is, inflammation and protein aggregation) has divided the field of sIBM research into two opposing (albeit slowly unifying) camps regarding disease pathogenesis. The present review explores the recent evidence supporting these distinct pathogenic mechanisms. Future therapies that are designed to target both aspects of sIBM pathologies will likely be necessary to treat sIBM.

Valosin containing protein associated fronto-temporal lobar degeneration: clinical presentation, pathologic features and pathogenesis.

Inclusion body myopathy (IBM) associated with paget's disease of the bone (PDB) and fronto-temporal dementia (FTD) or IBMPFD, is a rare multisystem degenerative disorder due to mutations in valosin containing protein (VCP). VCP is a ubiquitously expressed protein that facilitates the degradation of proteins via the ubiquitin proteasome and autophagy pathways. Affected brain and muscle tissue in IBMPFD have ubiquitinated and TAR DNA binding protein-43 (TDP-43) inclusions. In skeletal muscle, this pathology is consistent with IBM. While in the CNS, IBMPFD is a frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) subtype. Recent studies suggest that IBMPFD mutations in VCP disrupt its function in protein degradation. This review will explore the clinical phenotype and pathology of IBMPFD with an emphasis on central nervous system degeneration. In addition, we will discuss the current understanding regarding VCP's function in terminally differentiated tissue and how disease associated mutations result in both myo- and neurodegeneration.

TDP-43 accumulation in inclusion body myopathy muscle suggests a common pathogenic mechanism with frontotemporal dementia.

TAR DNA binding protein-43 (TDP-43) is found in ubiquitinated inclusions (UBIs) in some frontotemporal dementias (FTD-U). One form of FTD-U, due to mutations in the valosin containing protein (VCP) gene, occurs with an inclusion body myopathy (IBMPFD). Since IBMPFD brain has TDP-43 in UBIs, we looked for TDP-43 inclusions in IBMPFD muscle. In normal muscle, TDP-43 is present in nuclei. In IBMPFD muscle, TDP-43 is additionally present as large inclusions within UBIs in muscle cytoplasm. TDP-43 inclusions were also found in 78% of sporadic inclusion body myositis (sIBM) muscles. In IBMPFD and sIBM muscle, TDP-43 migrated with an additional band on immunoblot similar to that reported in FTD-U brains. This study adds sIBM and hereditary inclusion body myopathies to the growing list of TDP-43 positive inclusion diseases.

Novel VCP mutations in inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia.

Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD, OMIM 167320) has recently been attributed to eight missense mutations in valosin-containing protein (VCP). We report novel VCP mutations N387H and L198W in six individuals from two families who presented with proximal muscle weakness at a mean age of diagnosis of 40 years, most losing the ability to walk within a few years of onset. Electromyographic studies in four individuals were suggestive of 'myopathic' changes, and neuropathic pattern was identified in one individual in family 1. Muscle biopsy in four individuals showed myopathic changes characterized by variable fiber size, two individuals showing rimmed vacuoles and IBM-type cytoplasmic inclusions in muscle fibers, and electron microscopy in one individual revealing abundant intranuclear inclusions. Frontotemporal dementia associated with characteristic behavioral changes including short-term memory loss, language difficulty, and antisocial behavior was observed in three individuals at a mean age of 47 years. Detailed brain pathology in one individual showed cortical degenerative changes, most severe in the temporal lobe and hippocampus. Abundant ubiquitin-positive tau-, alpha-synuclein-, polyglutamine repeat-negative neuronal intranuclear inclusions and only rare intracytoplasmic VCP positive inclusions were seen. These new mutations may cause structural changes in VCP and provide some insight into the functional effects of pathogenic mutations.

Adenoviral gene transfer of nitric oxide synthase increases cerebral blood flow in rats.

OBJECTIVE: Depletion of nitric oxide may play a role in the development of vasospasm after aneurysmal subarachnoid hemorrhage. Replenishment of nitric oxide might be a useful treatment for vasospasm. Using rats, we performed intracisternal injections of replication-defective adenovirus containing the endothelial nitric oxide synthase (eNOS) gene and determined the localization of and effect on cerebral blood flow of transgene expression. METHODS: Rats underwent baseline measurement of cortical cerebral blood flow using laser Doppler flowmetry. Replication-defective adenovirus containing the Escherichia coli LacZ gene (Ad327beta-Gal, n = 2/time point) or the bovine eNOS gene (AdCD8-NOS, n = 4/time point) or physiological saline solution was injected into the cisterna magna. Cerebral blood flow was measured 1, 2, 4, 7, or 14 days later, and the animals were killed. Expression of beta-galactosidase activity from the LacZ gene was examined by histochemical staining and that of eNOS was examined by polymerase chain reaction assays of messenger ribonucleic acid. Brains were histopathologically examined for inflammation. RESULTS: Beta-galactosidase activity was observed throughout the leptomeninges and in some cells in the adventitia of small subarachnoid blood vessels in the Ad327beta-Gal-injected rats. Messenger ribonucleic acid for eNOS was detected in the leptomeninges and brainstem 1 and 2 days after injection of AdCD8-NOS. Rats injected with Ad327beta-Gal or physiological saline solution exhibited decreased cerebral blood flow beginning 2 days after virus injection and lasting up to 14 days after injection. Rats injected with AdCD8-NOS developed significant transient increases in cerebral blood flow 2 days after virus injection, followed by slight decreases in blood flow. There was inflammation in the subarachnoid space of all animals; the inflammation was qualitatively worse in animals injected with Ad327beta-Gal, compared with rats injected with AdCD8-NOS or saline solution. CONCLUSION: Intracisternal injection of replication-defective adenovirus containing the eNOS gene can transiently increase cerebral blood flow.

Effect of adenovirus-mediated nitric oxide synthase gene transfer on vasospasm after experimental subarachnoid hemorrhage.

OBJECTIVE: Evidence indicates that vasospasm after subarachnoid hemorrhage (SAH) is caused in part by a decrease in the vasodilator nitric oxide (NO), which is produced mainly in endothelial cells. This study tested whether intracisternal injection of adenovirus-expressing endothelial NO synthase (eNOS) would decrease vasospasm in dogs. METHODS: In 12 dogs, baseline cerebral angiography was performed, and then SAH was produced by two injections of blood into the cisterna magna. The dogs were randomized (n = 6/group) to intracisternal injection of adenovirus-expressing lacZ (Ad327beta-Gal) or eNOS (AdCD8-NOS), administered immediately after the first blood injection. Angiography was repeated on Day 7, and then L-arginine (50 mg) was administered intracisternally, and angiography was repeated. Cerebrospinal fluid aspirated from the cisterna magna on Days 2 and 7 was analyzed for levels of NO metabolites. The dogs were killed, and their basilar arteries were removed and studied pharmacologically. Four control dogs underwent angiography on Day 0, followed by virus injection (n = 2/group). Angiography was repeated on Day 7, and the control dogs were killed. Transgene expression was detected in tissue removed on Day 7 by histochemical staining for lacZ, by polymerase chain reaction for messenger ribonucleic acid for eNOS, and by measurement of NO metabolites in cerebrospinal fluid. RESULTS: Angiography showed significant vasospasm in each group (Ad327beta-Gal, -54 +/- 7% reduction in basilar artery diameter; AdCD8-NOS, -53 +/- 7%), with no significant difference between groups. Injection of L-arginine caused an insignificant increase in arterial diameter in each group. In dogs without SAH, Ad327beta-Gal caused a reduction in basilar artery diameter (-13 +/- 10%, P = 0.42; paired t test), whereas injection of AdCD8-NOS caused an increase in diameter (14 +/- 16%, P = 0.77; paired t test). Histological examination and beta-galactosidase staining of dogs given injections of Ad327beta-Gal showed staining in inflammatory cells in the subarachnoid space, in the adventitia of the cerebral vessels, and in the liver and lungs. Messenger ribonucleic acid for eNOS was detected in the leptomeninges of dogs given injections of AdCD8-NOS. Under isometric tension, basilar arteries from each group demonstrated similar relaxation to L-arginine, but arteries exposed to eNOS demonstrated significantly greater relaxation to L-arginine plus tetrahydrobiopterin than arteries exposed to lacZ. Cerebrospinal fluid levels of NO and its metabolites were significantly higher in dogs treated with AdCD8-NOS than those treated with Ad327beta-Gal 2 days after SAH. CONCLUSION: These results demonstrate that adenovirus vectors can be used to transfer genes to cells in the subarachnoid space of dogs. Enough NO can be produced in the absence of SAH to dilate the basilar artery. After SAH, however, NO plus a cofactor can dilate arteries in vitro, but not enough NO is generated in the subarachnoid space to prevent vasospasm, perhaps owing to the scavenging of NO by hemoglobin.

The role of beta-catenin stability in mutant PS1-associated apoptosis.

Most early onset cases of familial Alzheimer's disease (FAD) are caused by mutations in presenilin-1 (PS1) and presenilin-2 (PS2). These mutations lead to increased beta-amyloid formation and induce apoptosis when expressed in vitro. Recently, PS1 has been reported to associate with beta-catenin, an armadillo repeat protein. PS1 may regulate the function of beta-catenin, and mutant PS1 may disrupt this regulation. In the present study, we confirm that PS1-WT, as well as mutant PS1, associates with beta-catenin, and that mutant PS1 expression decreases the stability and/or enhances the degradation of beta-catenin. Most importantly, we correlate beta-catenin's destabilization with mutant PS1-associated apoptosis by administering drugs that alter the stability of beta-catenin. The application of LiCl and a proteasome inhibitor, N-acetyl-leu-leu-norleucinal (ALLN), increased the stability of cytosolic beta-catenin in mutant PS1-expressing cells leading to rescue of these cells from apoptosis. These studies suggest that beta-catenin is a key mediator of mutant PS1-associated apoptosis and FAD pathogenesis.

Creutzfeldt-Jakob disease, new variant creutzfeldt-jakob disease, and bovine spongiform encephalopathy.

Creutzfeldt-Jakob disease (CJD) is a subacute spongiform encephalopathy (SSE) that is manifested by a variety of neurologic signs that usually include dementia, myoclonus, and an abnormal electroencephalogram (EEG). In 1996, a new variant of CJD (nvCJD) with a somewhat distinctive clinical presentation and neuropathology was reported in adolescents and young adults, a cohort of patients not normally affected with CJD. The appearance of nvCJD coincided temporally and geographically with the emergence of an SSE in cattle known as bovine spongiform encephalopathy (BSE), or mad cow disease. This article discusses the clinical syndrome, pathology, and pathogenesis of classical CJD, nvCJD, and other human SSEs, as well as the link between BSE and nvCJD.

Alternative translation initiation of Theiler's murine encephalomyelitis virus.

DA strain and other members of the TO subgroup of Theiler's murine encephalomyelitis virus (TMEV) produce a chronic demyelinating disease in which the virus persists but has a restricted expression. We previously reported that TO subgroup strains, in addition to synthesizing the picornaviral polyprotein, use an alternative initiation codon just downstream from the polyprotein's AUG to translate an 18-kDa protein called L* that is out of frame with the polyprotein (H. H. Chen et al., Nat. Med. 1:927-931, 1995; W. P. Kong and R. P. Roos, J. Virol. 65:3395-3399, 1991). L* is critically important for virus persistence and the induction of the demyelinating disease (Chen et al., 1995; G. D. Ghadge et al. J. Virol. 72:8605-8612, 1998). We have proposed that variations in the amount of translation initiation from the L* AUG versus the polyprotein AUG may occur in different cell types and therefore affect the degree of expression of viral capsid proteins. We now demonstrate that ribosomal translation initiation at the polyprotein's initiation codon affects initiation at the L* AUG, suggesting that ribosomes land at the polyprotein's initiation codon before scanning downstream and initiating at the L* AUG. We also find that the viral 5' untranslated region affects utilization of the L* AUG. Surprisingly, mutant DA cDNAs were found to be infectious despite the presence of mutations of the polyprotein initiation codon or placement of a stop codon upstream of the L* AUG in the polyprotein's reading frame. Sequencing studies showed that these viruses had a second site mutation, converting the reading frame of L* into the polyprotein's reading frame; the results suggest that translation of the polyprotein during infection of these mutant viruses can be initiated at the L* AUG. These data are important in our understanding of translation initiation of TMEV and other RNAs that contain an internal ribosome entry site.

Processing of wild-type and mutant familial Alzheimer's disease-associated presenilin-1 in cultured neurons.

Mutations of presenilin (PS)-1, an endoplasmic reticulum/Golgi transmembrane protein, have been associated with early-onset familial Alzheimer's disease (FAD). In mammalian brain, PS1 exists primarily as its processed fragments; however, the role of this cleavage event in PS1 function remains unclear. Although some investigators have shown that mutant PS1 processing is unaltered (with the exception of PS1-deltaE9, which lacks the cleavage site) in stably transfected cells and PS1-FAD transgenic mice, other investigators have reported altered FAD mutant PS1 and PS2 protein processing in transiently transfected cells and human FAD patients. The present study uses recombinant replication-defective adenoviral vectors to transiently express wild-type (WT) or mutant PS1 in various cells, including primary cultured hippocampal neurons. We show that in contrast to PS1-WT, overexpression of mutant PS1 results in an increased ratio of mutant holoprotein to endoproteolytic products that is dependent on cell type and differentiation state. In addition, mutant PS1 overexpression leads to an increase in caspase-type protease derived fragments above that seen with PS1-WT overexpression. Furthermore, overexpression of at least one mutant significantly alters the processing of coexpressed PS1-WT, suggesting that mutant PS1 may affect PS1-WT function. These findings suggest that a defect in PS1 holoprotein stability may be a general defect seen in cells expressing mutant PS1, especially neuronal cells, and may play a critical role in the pathogenesis of FAD.

Mutant presenilin-1 induces apoptosis and downregulates Akt/PKB.

Most early onset cases of familial Alzheimer's disease (AD) are caused by mutations in presenilin-1 (PS1) and presenilin-2 (PS2). These mutations lead to increased beta-amyloid formation and may induce apoptosis in some model systems. Using primary cultured hippocampal neurons (HNs) and rat pheochromocytoma (PC12) cells transiently transfected with replication-defective recombinant adenoviral vectors expressing wild-type or mutant PS1, we demonstrate that mutant PS1s induce apoptosis, downregulate the survival factor Akt/PKB, and affect several Akt/PKB downstream targets, including glycogen synthase kinase-3beta and beta-catenin. Expression of a constitutively active Akt/PKB rescues HNs from mutant PS1-induced neuronal cell death, suggesting a potential therapeutic target for AD. Downregulation of Akt/PKB may be a mechanism by which mutant PS1 induces apoptosis and may play a role in the pathogenesis of familial AD.