Mechanisms of tissue injury in multiple sclerosis: opportunities for neuroprotective therapy

Development of neuroprotective therapies for multiple sclerosis is dependent on defining the precise mechanisms whereby immune effector cells and molecules are able to induce relatively selective injury of oligodendrocytes (OLs) and their myelin membranes. The selectivity of this injury could be conferred either by the properties of the effectors or the targets. The former would involve antigen specific recognition by either antibody or T cell receptor of the adaptive immune system. OLs are also susceptible to non antigen restricted injury mediated by components of the innate immune system including macrophages/microglia and NK cells. Target related selectivity could reflect the expression of death inducing surface receptors (such as Fas or TNFR-1) required for interaction with effector mediators and subsequent intracellular signaling pathways, including the caspase cascade. Development of therapeutic delivery systems, which would reach the site of disease activity within the CNS, will permit the administration of inhibitors either of the cell death pathway or of effector target interaction and opens new avenues to neuroprotection approach.

Caspase 8 expression and signaling in Fas injury-resistant human fetal astrocytes

Fas (APO-1/CD95) is a cell surface receptor initially identified in lymphoid cells, but more recently detected in the central nervous system under pathological, usually inflammatory, conditions. In most Fas expressing cells, triggering of Fas by its ligand or by antagonistic antibodies leads to apoptosis. Human fetal astrocytes (HFA) constitutively express Fas yet are resistant to cell death following Fas ligation. In the current study, using dissociated cultures of human fetal central nervous system-derived cells, we attempted to identify a basis for HFA resistance to Fas-mediated injury. We compared the components of the Fas signaling pathway of HFA to those of two human cell lines susceptible to Fas-mediated injury, U251 glioma and Jurkat T-cells. We found that HFA did not express caspase 8 (FLICE), the caspase primarily activated on Fas signaling. Although we could induce caspase 8 in HFA with the inflammatory cytokines IFNgamma and TNFalpha, HFA remained resistant to Fas-mediated injury. Addition of inflammatory cytokines to the extracellular milieu also increased FLIP mRNA (FLICE inhibitory protein). Furthermore, upon triggering of cytokine-treated cells with FasL, we observed upregulation of the cleavage product of FLIP (p43-FLIP) previously shown to associate with the DISC and to block caspase 8 recruitment, thereby inhibiting Fas-mediated death. Our findings indicate that caspase 8 and its regulators play a central role in determining the response to Fas ligation of HFA and support a role for Fas signaling in the developing central nervous system other than related to cytotoxicity.

Kinin B1 receptor expression and function on human brain endothelial cells

The kinin B1 receptor is an inducible receptor expressed in response to inflammatory mediators. We sought to determine whether kinin B1 receptor can be expressed on human brain endothelial cells (HBECs) in vitro and whether signaling via this receptor can regulate permeability and chemokine production properties of these cells. Multiplex RT-PCR amplification and western blot techniques were used to evaluate B1 receptor expression by HBECs. Although B1 receptor mRNA and protein could not be detected on resting HBECs, interferon-gamma induced a dose- and time-dependent up-regulation of B1 receptor mRNA and protein on HBECs. Stimulation of interferon-gamma-treated HBECs with the selective B1 agonist R-838 (Sar [D-Phe8] des Arg9-BK) induced a dose- and time-dependent increase in the production of inositol 3,4,5 tri-phosphate and nitric oxide. Permeability of the HBECs monolayer, as measured by BSA diffusion, was significantly increased by application of the B1 agonist. This biological effect of R-838 could be prevented by R-715, a B1 receptor antagonist and by L-NAME, a nitric oxide synthase blocker. R-838 also inhibited interleukin-8 release from HBECs. We demonstrate that B1 receptors can be up regulated on the surface of HBECs by molecules released during inflammatory response and that signaling via this receptor can regulate BBB permeability and chemokine production in vitro.

Differential effects of dystrophin and utrophin gene transfer in immunocompetent muscular dystrophy (mdx) mice

Duchenne muscular dystrophy (DMD) is a fatal disease caused by defects in the gene encoding dystrophin. Dystrophin is a cytoskeletal protein, which together with its associated protein complex, helps to protect the sarcolemma from mechanical stresses associated with muscle contraction. Gene therapy efforts aimed at supplying a normal dystrophin gene to DMD muscles could be hampered by host immune system recognition of dystrophin as a "foreign" protein. In contrast, a closely related protein called utrophin is not foreign to DMD patients and is able to compensate for dystrophin deficiency when overexpressed throughout development in transgenic mice. However, the issue of which of the two candidate molecules is superior for DMD therapy has remained an open question. In this study, dystrophin and utrophin gene transfer effects on dystrophic muscle function were directly compared in the murine (mdx) model of DMD using E1/E3-deleted adenovirus vectors containing either a dystrophin (AdV-Dys) or a utrophin (AdV-Utr) transgene. In immunologically immature neonatal animals, AdV-Dys and AdV-Utr improved tibialis anterior muscle histopathology, force-generating capacity, and the ability to resist injury caused by high-stress contractions to an equivalent degree. By contrast, only AdV-Utr was able to achieve significant improvement in force generation and the ability to resist stress-induced injury in the soleus muscle of immunocompetent mature mdx animals. In addition, in mature mdx mice, there was significantly greater transgene persistence and reduced inflammation with utrophin compared to dystrophin gene transfer. We conclude that dystrophin and utrophin are largely equivalent in their intrinsic abilities to prevent the development of muscle necrosis and weakness when expressed in neonatal mdx animals with an immature immune system. However, because immunity against dystrophin places an important limitation on the efficacy of dystrophin gene replacement in an immunocompetent mature host, the use of utrophin as an alternative to dystrophin gene transfer in this setting appears to offer a significant therapeutic advantage.

Expression of p27kip1 and p53 in medulloblastoma: relationship with cell proliferation and survival

p27kip1 and p21cip1 are cyclin-dependent kinase (cdk) inhibitors which along with p53 play critical roles in the control of cell cycle progression. Accumulation of p27kip1 in post-mitotic neurons is a major event of neurogenesis. We hypothesized that a dysregulation of the expression of p53 and these cdk inhibitors underlies cellular proliferation in medulloblastomas, and tested this hypothesis by investigating p27kip1, p21cip1, Bcl2 and p53 immunoreactivity in 14 medulloblastoma tumors. We noted an inverse relationship between p27kip1 expression and cellular proliferation (MIB1). Focal islands of neuroblastic or glial differentiation expressed high levels of p27kip1, while the undifferentiated, highly-proliferative population of tumor cells showed no detectable p27kip1 expression, thus suggesting a role for p27kip1 in cell cycle control in medulloblastoma. In addition, there was no detectable p21cip1 expression in any of the medulloblastomas studied. The low level of apoptosis displayed by these tumors was not associated with the expression of Bcl-2. A significant relationship was found between detection of p53 protein and poor survival. Since, p21cip1 and p27kip1 are often co-expressed with other INK4 family of cdk inhibitors during the induction of cellular differentiation and are synergistic in their effect, a deregulation of their coordinate expression may underlie the lack of complete differentiation in medulloblastoma.

Modulation of Starling forces and muscle fiber maturity permits adenovirus-mediated gene transfer to adult dystrophic (mdx) mice by the intravascular route

Duchenne muscular dystrophy (DMD) and other inherited myopathies lead to progressive destruction of most skeletal muscles in the body, including those responsible for maintaining respiration. DMD is a fatal disorder caused by defects in the dystrophin gene. Recombinant adenovirus vectors (AdV) are considered a promising means for therapeutic delivery of a functional dystrophin gene to DMD muscles. If AdV-mediated dystrophin gene replacement in DMD is to be successful, development of a systemic delivery method for targeting the large number of diseased muscles will be required. In this study we investigated two major factors preventing efficient AdV-mediated gene transfer to skeletal muscles of adult animals after intravascular AdV administration: (1) an inability of AdV particles to breach the endothelial barrier and enter into contact with myofibers, and (2) a relatively nonpermissive myofiber population for AdV infection due at least in part to insufficient levels of the coxsackie/adenovirus attachment receptor (CAR). On the basis of established principles governing the transendothelial flux of macromolecules, we further hypothesized that an alteration in Starling forces (increased hydrostatic and decreased osmotic pressures) within the intravascular compartment would facilitate AdV transendothelial flux via convective transport. In addition, experimental muscle regeneration was employed to increase the prevalence of immature myofibers in which CAR expression is upregulated. Here we report that by employing the above-described strategy, high-level heterologous reporter gene expression was achievable in hindlimb muscles of normal rats as well as dystrophic (mdx) mice (genetic homolog of DMD) after a single intraarterial injection of AdV. Microsphere studies confirmed enhanced transport into muscle of fluorescent tracer particles in the size range of AdV, and there was a high concordance between CAR upregulation and myofiber transduction after intraarterial AdV delivery. Furthermore, in mdx mice examined 10 days after intraarterial AdV delivery, the aforementioned procedures had no adverse effects on the force-generating capacity of targeted muscles. These findings have implications for eventual AdV-mediated gene therapy of generalized skeletal muscle diseases such as DMD using a systemic intraarterial delivery approach.

Immunolocalization of NAIP in the human brain and spinal cord

The neuronal apoptosis inhibitory protein (NAIP) is known to have anti-apoptotic functions, and its gene is often mutated in severe cases of spinal muscular atrophy (SMA), a disease characterized by motor neuron degeneration. In this study, we examined the distribution of the endogenous NAIP protein in normal human spinal cord and brain tissue by using a polyclonal antibody against NAIP. Immunohistochemical staining demonstrated that NAIP is strongly expressed in anterior horn and motor cortex neurons of normal brains, and it is not altered in the remaining motor neurons of patients with amyotrophic lateral sclerosis (ALS). NAIP is also located in human fetal neurons and in adult choroid plexus cells. These results suggest that the anti apoptotic molecule NAIP may be important in motor neurons, but it specifically does not appear to be altered in ALS.

Myophosphorylase gene transfer in McArdle's disease myoblasts in vitro

McArdle's disease is due to a genetic deficiency of glycogen phosphorylase and results in a lack of glucose mobilization from glycogen during anaerobic exercise. A genetic defect in Merino sheep produces a similar picture. We constructed a first-generation adenoviral recombinant containing the full-length human phosphorylase cDNA under the control of the Rous sarcoma virus promoter. Primary myoblast cultures from phosphorylase-deficient human and sheep muscle were efficiently transduced with this vector, resulting in restoration of the phosphorylase activity. A similar correction of the genetic defect in muscles of McArdle's patients in vivo appears feasible, preferably with the use of an adeno-associated viral vector.

Molecular therapy for glioblastoma

Glioblastoma (GB), the relatively frequent and most malignant form of primary brain tumor, is fatal within 1 to 2 years of onset of symptoms, despite conventional therapy. Molecular therapy promises to be an effective and possibly curative treatment. Several molecular strategies have been tested, either in animal models or clinical trials. These include: prodrug activating systems, introduction of tumor suppressor or cell-cycle-related genes, inhibition of growth factors and/or their receptors, inhibition of neovascularization, immunomodulatory maneuvers, oncolytic viruses and inhibition of matrix metalloproteinases. Of special interest for the development of optimal molecular therapy of GB, is the choice of the most efficient and least toxic gene vectors (adenovirus, retrovirus, herpes simplex virus), the route of administration of the therapeutic agent (intratumoral with or without debulking and intracarotid), avoidance of collateral damage to the perineoplastic neuropil and adequate preclinical studies. The ultimate molecular therapy will probably involve the application of multiple simultaneous (combinatorial) therapeutic modalities. The safety and efficiency of these in humans can only be judged by properly controlled therapeutic trials.

p53 induction by tumor necrosis factor-alpha and involvement of p53 in cell death of human oligodendrocytes

Oligodendrocytes (OLs) and their myelin membranes are the primary targets in the autoimmune disease multiple sclerosis (MS). The inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) has been implicated as a mediator of OL cell injury. TNF-alpha is detectable within MS lesions and induces apoptosis of mature human OLs in vitro. One possible mechanism by which TNF-alpha mediates cell death is through the activation of c-jun N-terminal kinase (JNK). We have previously shown that treatment of human OLs with TNF-alpha leads to activation of JNK. Here we provide evidence that p53, a regulator of the cell cycle and apoptosis, is a mediator of TNF-alpha-induced apoptosis of OLs. Although p53 was undetectable by western blot analysis in adult human OLs, its levels increased within 24 h after TNF-alpha treatment (100 ng/ml). The induced p53 was immunolocalized to the nucleus prior to the appearance of significant numbers of apoptotic cells. Overexpression of p53 by adenovirus-mediated gene transfer into human OLs in vitro resulted in marked apoptosis as revealed by in situ cleavage of DNA (TUNEL positive), decreased mitochondrial function, and release of lactate dehydrogenase into the culture medium. These in vitro studies demonstrate that increased p53 levels are associated with apoptosis of human OLs. The findings further implicate p53 as a target for the JNK pathway activated during TNF-alpha-mediated cell death of human adult OLs.

Hypoxia-induced loss of synaptic transmission is exacerbated in hippocampal slices of transgenic mice expressing C-terminal fragments of Alzheimer amyloid precursor protein

To investigate the possible involvement of beta-amyloid (A beta) in disrupting neuronal function during ischemia, we examined whether overexpression of C-terminal fragments of beta-amyloid precursor protein (beta-APP) in transgenic (Tg) mice is capable of altering the capacity of hippocampus slices to recover synaptic transmission after transient hypoxic episodes. Recovery of synaptic transmission was monitored in area CA1 of perfused hippocampal slices prepared from both control and Tg mice. The results obtained indicate that hippocampal slices prepared from Tg mice exhibited a much lower level of recovery in synaptic transmission following reoxygenation. This reduction in the capacity of Tg slices to recover from hypoxia-induced impairment of synaptic transmission in the hippocampus does not appear to be related to pre-existing alterations in either functional or biochemical properties of glutamate receptors in Tg mice. The present results provide the first experimental evidence that overexpression of the C-terminal fragment of APP exacerbates functional damage of hippocampal neurons after hypoxic episodes.

Adenovirus-mediated utrophin gene transfer mitigates the dystrophic phenotype of mdx mouse muscles

Utrophin is a close homolog of dystrophin, the protein whose mutations cause Duchenne muscular dystrophy (DMD). Utrophin is present at low levels in normal and dystrophic muscle, whereas dystrophin is largely absent in DMD. In such cases, the replacement of dystrophin using a utrophin gene transfer strategy could be more advantageous because utrophin would not be a neoantigen. To establish if adenovirus (AV)-mediated utrophin gene transfer is a possible option for the treatment of DMD, an AV vector expressing a shortened version of utrophin (AdCMV-Utr) was constructed. The effect of utrophin overexpression was investigated following intramuscular injection of this AV into mdx mice, the mouse model of DMD. When the tibialis anterior (TA) muscles of 3- to 5-day-old animals were injected with 5 microl of AdCMV-Utr (7.0 x 10(11) virus/ml), an average of 32% of fibers were transduced and the transduction level remained stable for at least 60 days. The presence of utrophin restored the normal histochemical pattern of the dystrophin-associated protein complex at the cell surface and resulted in a reduction in the number of centrally nucleated fibers. The transduced fibers were largely impermeable to the tracer dye Evans blue, suggesting that utrophin protects the surface membrane from breakage. In vitro measurements of the force decline in response to high-stress eccentric contractions demonstrated that the muscles overexpressing utrophin were more resistant to mechanical stress-induced injury. Taken together, these data indicate that AV-mediated utrophin gene transfer can correct various aspects of the dystrophic phenotype. However, a progressive reduction in the number of transduced fibers was observed when the TA muscles of 30- to 45-day-old mice were injected with 25 microl of AdCMV-Utr. This reduction coincides with a humoral response to the AV and transgene, which consists of a hybrid mouse-human cDNA.

Vesicular stomatitis virus G pseudotyped retrovector mediates effective in vivo suicide gene delivery in experimental brain cancer

Direct in vivo tumor-targeting with "suicide" viral vectors is limited by either inefficient gene transfer (i.e., retroviral vectors) or indiscriminate transfer of a conditionally toxic gene to surrounding nonmalignant tissue (i.e., adenoviral vectors). Retrovectors pseudotyped with the vesicular stomatitis virus G protein (VSVG) may serve as a remedy to this conundrum. These retroviral particles differ from standard murine retroviruses by their very broad tropism and the capacity to be concentrated by ultracentrifugation without loss of activity. We propose that a VSVG-typed retrovector can be used for efficient and tumor-specific herpes simplex virus thymidine kinase (TK) gene delivery in vivo. To test this hypothesis, we developed a bicistronic retroviral vector that expresses TK and green fluorescence protein (pTKiGFP). The 293GPG packaging cell line was used to generate vTKiGFP retroparticles. In cytotoxicity assays, vTKiGFP-transduced human glioma cell lines were sensitized to the cytotoxic effects of gangciclovir (GCV) 10,000-fold. Subsequently, virus was concentrated by ultracentrifugation to a titer of 2.3 x 10(10) cfu/ml. We tested the antitumor activity of vTKiGFP retroparticles in a rat C6 glioma model of brain cancer. Concentrated retrovector stock (9 microl volume) was injected stereotactically in preestablished intracerebral tumor. Subsequently, rats were treated with GCV for 10 days. Control rats (no GCV) had a mean survival of 38 days (range, 20-52 days). Sections performed on postmortem brain tissue revealed large tumors with evidence of high efficiency retrovector transfer and expression (as assessed by GFP fluorescence). Fluorescence was restricted to malignant tissue. In the experimental group (GCV treated), 8 of 12 remain alive and well >120 days after glioma implantation. In conclusion, vTKiGFP is very efficient at transducing human glioma cell lines in vitro and leads to significant GCV sensitization. Recombinant retroviral particles can be concentrated to titers that allow in vivo intratumoral delivery of large viral doses. The therapeutic efficiency of this reagent has been demonstrated in a preclinical model of brain cancer.

Expression of the primary coxsackie and adenovirus receptor is downregulated during skeletal muscle maturation and limits the efficacy of adenovirus-mediated gene delivery to muscle cells

Skeletal muscle fibers are infected efficiently by adenoviral vectors only in neonatal animals. This lack of tropism for mature skeletal muscle may be partly due to inefficient binding of adenoviral particles to the cell surface. We evaluated in developing mouse muscle the expression levels of two high-affinity receptors for adenovirus, MHC class I and the coxsackie and adenovirus receptor (CAR). The moderate levels of MHC class I transcripts that were detected in quadriceps, gastrocnemius, and heart muscle did not vary between postnatal day 3 and day 60 adult tissue. A low level of CAR expression was detected on postnatal day 3 in quadriceps and gastrocnemius muscles, but CAR expression was barely detectable in adult skeletal muscle even by reverse transcriptase-polymerase chain reaction. In contrast, CAR transcripts were moderately abundant at all stages of heart muscle development. Ectopic expression of CAR in C2C12 mouse myoblast cells increased their transducibility by adenovirus at all multiplicities of infection (MOIs) tested as measured by lacZ reporter gene activity following AVCMVlacZ infection, with an 80-fold difference between CAR-expressing cells and control C2C12 cells at an MOI of 50. Primary myoblasts ectopically expressing CAR were injected into muscles of syngeneic hosts; following incorporation of the exogenous myoblasts into host myofibers, an increased transducibility of adult muscle fibers by AVCMVlacZ was observed in the host. Expression of the lacZ reporter gene in host myofibers coincided with CAR immunoreactivity. Furthermore, sarcolemmal CAR expression was markedly increased in regenerating muscle fibers of the dystrophic mdx mouse, fibers that are susceptible to adenovirus transduction. These analyses show that CAR expression by skeletal muscle correlates with its susceptibility to adenovirus transduction, and that forced CAR expression in mature myofibers dramatically increases their susceptibility to adenovirus transduction.

Intracerebral adenovirus-mediated p53 tumor suppressor gene therapy for experimental human glioma

Malignant gliomas of astrocytic origin are good candidates for gene therapy because they have proven incurable with conventional treatments. Although mutation or inactivation of the p53 tumor suppressor gene occurs at early stages in gliomas and is associated with tumor progression, many tumors including high-grade glioblastoma multiforme carry a functionally intact p53 gene. To evaluate the effectiveness of p53-based therapy in glioma cells that contain endogenous wild-type p53, a clinically relevant model of malignant human glioma was established in athymic nu/nu mice. Intracerebral, rapidly growing tumors were produced by stereotactic injection of the human U87 MG glioma cell line that had been genetically modified for tracking purposes to express the Escherichia coli lacZ gene encoding beta-galactosidase. Overexpression of the p53 gene by adenovirus-mediated delivery into the tumor mass resulted in rapid cell death with the eradication of beta-galactosidase-expressing glioma cells through apoptosis. In long-term experiments, the survival of mice treated with the p53 adenoviral recombinant was significantly longer than that of mice that had received control adenoviral recombinant. During the observation period of 1 year, a complete cure was achieved in 27% of animals after a single injection of p53 adenoviral recombinant, and 38% of the animals were tumor free in the group receiving multiple injections of p53 adenoviral recombinant into a larger tumor mass. These experiments demonstrate that overexpression of p53 in gliomas, even in the presence of endogenous functional wildtype p53, leads to efficient elimination of tumor cells. These results point to the potential therapeutic usefulness of this approach for all astrocytic brain tumors.

Combinatorial blockade of calcineurin and CD28 signaling facilitates primary and secondary therapeutic gene transfer by adenovirus vectors in dystrophic (mdx) mouse muscles

Recombinant adenovirus vectors (AdV) have been considered a potential vehicle for performing gene therapy in patients suffering from Duchenne muscular dystrophy but are limited by a cellular and humoral immune response that prevents long-term transgene expression as well as effective transduction after AdV readministration. Conventional immunosuppressive agents such as cyclosporine and FK506, which act by interfering with CD3-T-cell receptor-mediated signaling via calcineurin, are only partially effective in reversing these phenomena and may also produce substantial organ toxicity. We hypothesized that activation of redundant T-cell activation pathways could limit the effectiveness of these drugs at clinically tolerable doses. Therefore, we have tested the ability of immunomodulatory immunoglobulins (Ig) with different modes of action to facilitate AdV-mediated gene transfer to adult dystrophic (mdx) mice. When used in isolation, immunomodulatory Ig (anti-intercellular adhesion molecule-1, anti-leukocyte function-associated antigen-1, anti-CD2, and CTLA4Ig) were only mildly effective in mitigating cellular and/or humoral immunity against adenovirus capsid proteins and the therapeutic transgene product, dystrophin. However, the combination of FK506 plus CTLA4Ig abrogated the immune response against adenovirus proteins and dystrophin to a degree not achievable with the use of either agent alone. At 30 days after AdV injection, >90% of myofibers could be found to express dystrophin with little or no evidence of a cellular immune response against transduced fibers. In addition, the humoral immune response was markedly suppressed, and this was associated with increased transduction efficiency following vector readministration. These data suggest that by facilitating both primary and secondary transduction after AdV administration, combined targeting of CD3-T-cell receptor-mediated signaling via calcineurin and the B7:CD28 costimulatory pathway could greatly increase the potential utility of AdV-mediated gene transfer as a therapeutic modality for genetic diseases such as Duchenne muscular dystrophy that will require long-term transgene expression and repeated vector delivery.

Interferons impair early transgene expression by adenovirus-mediated gene transfer in muscle cells

Recombinant adenovirus (AVR) promises to be an efficient vector in gene therapy for neuromuscular diseases, but in preclinical experiments the expression of therapeutic genes is shorter lived in immunocompetent animals than in immunocompromised hosts. Interferons (IFN), which are known to have a role both in early antiviral activity and in late cytotoxic immunoreaction against the virus or transduced cells, may influence the efficiency of gene transfer. In this study we investigated the role of IFNs in determining the efficiency of gene transfer by AVR. AVRs expressing beta-galactosidase (beta-gal) from either a cytomegalovirus (CMV) or a troponin-I promoter were used. Muscle cells were infected by AVR after exposure to various IFNs. The alphaIFN treatment significantly reduced (up to fivefold) the CMV promoter-driven gene expression in muscle cells in vitro and in immature muscles in vivo, while the least effective inhibitor was betaIFN. The decrease in gene expression by IFNs was more pronounced with the CMV-driven transgene than troponin-I promoter-driven one and was due to a decrease in transcript level. Intrinsic IFNs that are triggered by AVR administration can decrease the efficiency of gene transfer in muscle cells. Therefore the use of muscle specific promoters in AVR and/or IFN inhibitory agents will likely improve the prospects of effective gene therapy by AVR.

Differential role for protein kinase C-mediated signaling in the proliferation of medulloblastoma cell lines

Recent studies have implicated protein kinase C (PKC)-mediated signaling in the proliferation of gliomas. In this study, we have investigated the role of PKC mediated signaling in the proliferation of medulloblastoma cell lines DAOY, D283-Med and D341-Med. By Western blot analyses, conventional PKC (cPKC) alpha was detectable in DAOY only, while atypical PKC (aPKC) zeta was present in all three cell lines. cPKC beta1, beta11, gamma novel PKC (nPKC) delta, and epsilon were not detectable in any of the cell lines. Antisense oligonucleotides to PKC alpha , Calphostin C (a specific PKC inhibitor) and prolonged treatment with phorbol 12-myristate 13-acetate (PMA) with down regulation of cPKCalpha caused a decrease in proliferation in DAOY and no effect on D283-Med. Furthermore, PMA treatment was also associated with upregulation of p21cip1 in DAOY. Since cPKCalpha is the only PMA responsive isoform in DAOY, this observation implicates the cPKCalpha isoform in the proliferation of DAOY but not in D283-Med. A comparison of DAOY and D283-Med showed a higher proliferation index in DAOY. In contrast, multiprobe riboquant ribonuclease protection assay revealed higher levels of p27kip1 and p21cip1 mRNA in D283-Med. These transcripts were barely detectable in untreated DAOY. These observations indicate possible significant molecular heterogeneity among medulloblastomas with implications for differing biology among medulloblastoma cell lines and tumors.

High-level dystrophin expression after adenovirus-mediated dystrophin minigene transfer to skeletal muscle of dystrophic dogs: prolongation of expression with immunosuppression

Replication-deficient adenovirus vectors (AdV) have been successfully used to transfer a truncated human dystrophin cDNA to skeletal muscle of dystrophin-deficient mdx mice. A dystrophin-deficient golden retriever dog model (GRMD) has been identified, which, unlike the mouse model, leads to a clinicopathological phenotype similar to that of Duchenne muscular dystrophy (DMD). We show for the first time that high-level dystrophin expression in skeletal muscle of GRMD dogs can be achieved by AdV-mediated gene transfer. However, a humoral and cellular immune response of the host against antigens of viral and transgene origin (similar to that occurring in mdx mice after AdV-mediated dystrophin gene transfer) leads to a decline of dystrophin expression over a 2-month period. Immunosuppression by cyclosporin significantly prolonged transgene expression. The GRMD model may help to solve the open questions pertaining to dystrophin gene transfer such as systemic delivery and improvement of muscle function before human trials for gene replacement therapy in DMD may be considered.

Adenovirus-mediated dystrophin minigene transfer improves muscle strength in adult dystrophic (MDX) mice

Duchenne muscular dystrophy (DMD) and murine X-linked muscular dystrophy (mdx) are both due to absence of the subsarcolemmal protein dystrophin. Recombinant adenovirus vectors (AdV) are considered a promising means for delivering a functional dystrophin gene to muscle. However, the usefulness of AdV for this purpose is limited by vector toxicity as well as immune-mediated elimination of infected fibers. In addition, studies to date of AdV-mediated dystrophin gene transfer have either failed to examine effects on muscle strength or been performed in immunologically immature neonatal animals with little baseline abnormality of force-generating capacity. In the present study, AdV-mediated dystrophin gene transfer was performed in adult mdx mice with pre-existent dystrophic pathology and muscle weakness. The main findings are as follows: (1) acute myofiber toxicity and gene transfer efficiency are both AdV dose-dependent, such that the therapeutic margin of safety is fairly narrow; (2) immunosuppressive therapy (FK506) prevents immune-mediated elimination of dystrophin-positive fibers but not the dose-dependent toxic effects; (3) at the optimal vector dosage and with effective immunosuppression, AdV-mediated dystrophin minigene transfer is capable of alleviating the loss of force-generating capacity as well as histopathological evidence of disease progression normally seen in adult mdx muscles over a 2-month period. These findings have important implications for the eventual application of AdV-mediated dystrophin gene transfer in DMD patients.

Progressive myoclonus epilepsy in young adults with neuropathologic features of Alzheimer's disease

Progressive myoclonus epilepsy (PME) may develop in adult life. We present two patients with PME appearing around the age of 30 years in whom the disorder represented a manifestation of Alzheimer's disease. This diagnosis must be considered in addition to possible Kufs' disease or myoclonic epilepsy with ragged red fibers (MERRF) when PME develops in young adults.

Alzheimer's disease: current knowledge, management and research

Alzheimer's disease is a common neurological condition, appearing as early as age 40 but increasing dramatically in incidence over age 85. Different genetic factors are at play, modified by events over a lifetime. Clinical diagnosis is possible through careful history taking with a reliable informant and a minimum number of laboratory tests. A relatively predictable natural history can be observed, with progression through stages of cognitive loss, functional impairment and behavioural disinhibition or apathy. New medications such as donepezil offer hope for improving or stabilizing symptoms. Such treatment can be administered by primary care physicians with experience in the diagnosis and management of Alzheimer's disease. Disease stabilization, or even prevention, may be possible in the future.

Gene therapy research for Duchenne and Becker muscular dystrophies

Gene therapy is a promising option for the definitive treatment of Duchenne and Becker muscular dystrophies. Presently, gene therapy for Duchenne and Becker muscular dystrophies is still in the preclinical stage with dystrophin-deficient animals (the mdx mouse and a golden retriever dog strain) serving as convenient models. The thrust of research during the past 18 months has focused on two approaches: adenovirus-mediated dystrophin gene transfer and upregulation of a natural dystrophin analogue, utrophin. In the area of adenovirus-mediated gene transfer, substantial progress has been made in characterizing and mitigating the deleterious immune responses to the vector and transgene proteins. Furthermore, new adenovirus vectors have been created with reduced immunogenicity and increased insert gene capacity, which enhance the longevity of the transgene expression. Additional efforts are underway to develop safe and efficient routes of administration of the adenovirus vector carrying the dystrophin expression cassette. The prospects of utrophin upregulation as an attractive strategy for treatment of Duchenne and Becker muscular dystrophies was greatly enhanced by the demonstration of a substantial mitigation of the dystrophic phenotype of the transgenic mdx mouse overexpressing utrophin.

Study of adenovirus-mediated dystrophin minigene transfer to skeletal muscle by combined microscopic display of adenoviral DNA and dystrophin

In situ DNA hybridization of an E4 adenoviral sequence amplified by in situ polymerase chain reaction (PCR) was used to mark adenovirus-containing myonuclei in muscles of immunocompetent and immunosuppressed mdx mice following intramuscular injection of adenoviral recombinants. The adenoviral recombinants contained a 6.3-kb dystrophin cDNA (minigene) driven by a cytomegalovirus (CMV) promoter/enhancer and thus, immunostaining for dystrophin of the same sections permitted correlation of adenoviral recombinant-containing myonuclei with dystrophin positivity of the same muscle fiber segments. As early as 2 hr post-injection of adenoviral recombinant, an appreciable number of adenoviral recombinant-positive (AVR+) myonuclei, and some partial dystrophin positive (pdys+) fibers were observed. Some fully dystrophin-positive (dys+) muscle fibers were present as early as 6 hr. The maximum number of fibers containing AVR+ myonuclei (observed by 72 hr) was maintained until 60 days in immunosuppressed, but not in immunocompetent, animals. In immunocompetent animals, the maximum number of dys+ fibers was observed at 10 days. The vast majority of these fibers contained AVR+ myonuclei; however, by 60 days, dys+ fibers disappeared with some AVR+ myonuclei persisting. Our studies suggest that widespread delayed inactivation of the dystrophin expression cassette is probably unlikely. Thus, optimization of immunosuppression could assure successful long-term dystrophin gene transfer for gene therapy.