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P H Plotz

Publications and source records attributed to P H Plotz.

At least 19 recordsLinked to original sources
PubMed2001

Conditional tissue-specific expression of the acid alpha-glucosidase (GAA) gene in the GAA knockout mice: implications for therapy.

Both enzyme replacement and gene therapy of lysosomal storage disorders rely on the receptor-mediated uptake of lysosomal enzymes secreted by cells, and for each lysosomal disorder it is necessary to select the correct cell type for recombinant enzyme production or for targeting gene therapy. For example, for the therapy of Pompe disease, a severe metabolic myopathy and cardiomyopathy caused by deficiency of acid alpha-glucosidase (GAA), skeletal muscle seems an obvious choice as a depot organ for local therapy and for the delivery of the recombinant enzyme into the systemic circulation. Using knockout mice with this disease and transgenes containing cDNA for the human enzyme under muscle or liver specific promoters controlled by tetracycline, we have demonstrated that the liver provided enzyme far more efficiently. The achievement of therapeutic levels with skeletal muscle transduction required the entire muscle mass to produce high levels of enzyme of which little found its way to the plasma, whereas liver, comprising <5% of body weight, secreted 100-fold more enzyme, all of which was in the active 110 kDa precursor form. Furthermore, using tetracycline regulation, we somatically induced human GAA in the knockout mice, and demonstrated that the skeletal and cardiac muscle pathology was completely reversible if the treatment was begun early.

Animals↗
PubMed2001

Intercellular transfer of the virally derived precursor form of acid alpha-glucosidase corrects the enzyme deficiency in inherited cardioskeletal myopathy Pompe disease.

Pompe disease is a lethal cardioskeletal myopathy in infants and results from genetic deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). Genetic replacement of the cDNA for human GAA (hGAA) is one potential therapeutic approach. Three months after a single intramuscular injection of 10(8) plaque-forming units (PFU) of E1-deleted adenovirus encoding human GAA (Ad-hGAA), the activity in whole muscle lysates of immunodeficient mice is increased to 20 times the native level. Direct transduction of a target muscle, however, may not correct all deficient cells. Therefore, the amount of enzyme that can be transferred to deficient cells from virally transduced cells was studied. Fibroblasts from an affected patient were transduced with AdhGAA, washed, and plated on transwell culture dishes to serve as donors of recombinant enzyme. Deficient fibroblasts were plated as acceptor cells, and were separated from the donor monolayer by a 22-microm pore size filter. Enzymatic and Western analyses demonstrate secretion of the 110-kDa precursor form of hGAA from the donor cells into the culture medium. This recombinant, 110-kDa species reaches the acceptor cells, where it can be taken up by mannose 6-phosphate receptor-mediated endocytosis. It then trafficks to lysosomes, where Western analysis shows proteolytic processing to the 76- and 70-kDa lysosomal forms of the enzyme. Patient fibroblasts receiving recombinant hGAA by this transfer mechanism reach levels of enzyme activity that are comparable to normal human fibroblasts. Skeletal muscle cell cultures from an affected patient were also transduced with Ad-hGAA. Recombinant hGAA is identified in a lysosomal location in these muscle cells by immunocytochemistry, and enzyme activity is transferred to deficient skeletal muscle cells grown in coculture. Transfer of the precursor protein between muscle cells again occurs via mannose 6-phosphate receptors, as evidenced by competitive inhibition with 5 mM mannose 6-phosphate. In vivo studies in GAA-knockout mice demonstrate that hepatic transduction with adenovirus encoding either murine or human GAA can provide a depot of recombinant enzyme that is available to heart and skeletal muscle through this mechanism. Taken together, these data show that the mannose 6-phosphate receptor pathway provides a useful strategy for cell-to-cell distribution of virally derived recombinant GAA.

Adenoviridae↗
PubMed2001

The DNA mismatch repair enzyme PMS1 is a myositis-specific autoantigen.

OBJECTIVE: The specificity of the autoantibody response in different autoimmune diseases makes autoantibodies useful for diagnostic purposes. It also focuses attention on tissue- and event-specific circumstances that may select unique molecules for an autoimmune response in specific diseases. Defining additional phenotype-specific autoantibodies may identify such circumstances. This study was undertaken to investigate the disease specificity of PMS1, an autoantigen previously identified in some sera from patients with myositis. METHODS: We used immunoprecipitation analysis to determine the frequency of autoantibodies to PMS1 in sera from patients with myositis, systemic lupus erythematosus, or scleroderma and from healthy controls. Additional antigens recognized by PMS1-positive sera were further characterized in terms of their susceptibility to cleavage by apoptotic proteases. RESULTS: PMS1, a DNA mismatch repair enzyme, was identified as a myositis-specific autoantigen. Autoantibodies to PMS1 were found in 4 of 53 patients with autoimmune myositis (7.5%), but in no sera from 94 patients with other systemic autoimmune diseases (P = 0.016). Additional mismatch repair enzymes (PMS2, MLH1) were targeted, apparently independently. Sera recognizing PMS1 also recognized several other proteins involved in DNA repair and remodeling, including poly(ADP-ribose) polymerase, DNA-dependent protein kinase, and Mi-2. All of these autoantigens were efficiently cleaved by granzyme B, generating unique fragments not observed during other forms of cell death. CONCLUSION: PMS1 autoantibodies are myositis specific. The striking correlation between an immune response to a group of granzyme B substrates (functioning in DNA repair and remodeling) and the myositis phenotype strongly implies that tissue- and event-specific biochemical events play a role in selecting these molecules for an autoimmune response. Understanding the role of granzyme B cleavage in this response is an important priority.

Adult↗
PubMed2001

Identification and characterization of a tissue-specific silencer element in the first intron of the human acid maltase gene.

Deficiency of acid maltase (acid alpha-glucosidase), a lysosomal enzyme that degrades glycogen, results in glycogenosis type II, an autosomal recessive disease whose manifestations and severity largely depend on the level of residual enzyme activity. Previous studies have established that there are transcriptional control elements in the first intron; in particular a silencer responsive to Hes-1 and YY1 has been identified in the human hepatoma line, HepG2. This region functions as an enhancer in human fibroblasts. Here we have localized a silencer active in fibroblasts to a nearby 25-bp element in intron 1. This element repressed thymidine kinase promoter activity by about 50% in both orientations in human fibroblasts. This silencer, as with the previous one, is tissue specific since constructs containing this region are inactive in HepG2 cells. Electrophoretic mobility shift assay revealed three proteins specifically binding to the element in fibroblasts, and site-directed mutagenesis analysis indicated that all the three proteins binding to the element contribute to the silencer function. The data may be helpful for designing therapy to increase the level of enzyme, particularly when, as in most adults with the disease, there is reduced production of structurally normal enzyme.

Chloramphenicol O-Acetyltransferase↗
PubMed2000

Transcriptional regulation of the human acid alpha-glucosidase gene. Identification of a repressor element and its transcription factors Hes-1 and YY1.

Acid alpha-glucosidase, the product of a housekeeping gene, is a lysosomal enzyme that degrades glycogen. A deficiency of this enzyme is responsible for a recessively inherited myopathy and cardiomyopathy, glycogenesis type II. We have previously demonstrated that the human acid alpha-glucosidase gene expression is regulated by a silencer within intron 1, which is located in the 5'-untranslated region. In this study, we have used deletion analysis, electrophoretic mobility shift assay, and footprint analysis to further localize the silencer to a 25-base pair element. The repressive effect on the TK promoter was about 50% in both orientations in expression plasmid, and two transcriptional factors were identified with antibodies binding specifically to the element. Mutagenesis and functional analyses of the element demonstrated that the mammalian homologue 1 of Drosophila hairy and Enhancer of split (Hes-1) binding to an E box (CACGCG) and global transcription factor-YY1 binding to its core site function as a transcriptional repressor. Furthermore, the overexpression of Hes-1 significantly enhanced the repressive effect of the silencer element. The data should be helpful in understanding the expression and regulation of the human acid alpha-glucosidase gene as well as other lysosomal enzyme genes.

Base Sequence↗
PubMed1999

Novel mutations in African American patients with glycogen storage disease Type II. Mutations in brief no. 209. Online.

The infantile form of GSD II (an inherited deficiency of the lysosomal enzyme, acid alpha-glucosidase, Pompe disease) is a severe and invariably fatal disease characterized by a rapidly progressive generalized hypotonia, hepatomegaly, and cardiomegaly. We have recently demonstrated that African American patients share a common nonsense R854X mutation in exon 18 (Becker et al., 1998). Two other mutations, D645E and M519V, have been identified in individual African American patients (Hermans et al., 1993a; Huie et al., 1994a). We describe here three novel mutations in this population group: a missense W481R in exon 10, a deletion of a T1441 in exon 10, and a splicing defect at the 5' donor site of intron 8 (IVS g+la) . The splicing defect is shared by two unrelated patients and it is linked to intragenic polymorphic sites identical to those found in patients bearing the common R854X mutation.

Amino Acid Substitution↗
PubMed1999

Costimulatory markers in muscle of patients with idiopathic inflammatory myopathies and in cultured muscle cells.

In an attempt to understand the mechanisms of cell injury in the inflammatory myopathies, we analyzed the expression of costimulatory molecules, CTLA4, CD28, CD86, CD40, and CD154 as well as HLA class I, HLA class II, and ICAM-I in normal muscle and in muscle biopsies from patients with polymyositis (PM) or dermatomyositis (DM). By immunohistochemical staining, DM and PM biopsies showed the presence of CTLA4, CD28, CD86, and CD40 on inflammatory cells. More strikingly, however, low levels of CTLA4 and CD28 were observed on muscle cells. The expression of CTLA4 and CD28 on nonlymphoid cells has not been previously reported. These unexpected findings were confirmed in cultured normal human myoblasts: various proinflammatory cytokines induced the expression of CTLA4 and CD28 on normal human muscle cells. The sequences of the cDNAs were found to be identical to the sequences for these molecules in T cells. The data suggest a novel complexity in the network of cellular interactions between the infiltrated immune cells and the muscle cells in which the normal relationship between infiltrating inflammatory cells and target tissue is under a previously unrecognized set of controls.

Abatacept↗
PubMed1999

A pilot study: use of fludarabine for refractory dermatomyositis and polymyositis, and examination of endpoint measures.

OBJECTIVE: To study the effects of the adenine analog, fludarabine, on patients with refractory dermatomyositis and polymyositis, and to assess variables used in following myositis patients during medical intervention. METHODS: Patients whose myositis was not controlled by prednisone and at least one other immunosuppressive medication were entered into a pilot study during which they received 6 monthly cycles of intravenous fludarabine. Patients were assessed at baseline, every other month, and at month 7 for primary outcome measures of strength and function. Other measurements including peripheral blood cell subsets, muscle enzymes, and various assessments of disease activity were followed monthly during the fludarabine infusion period and for up to 6 months post therapy. RESULTS: Of 16 patients who entered the study, 4 patients were classified as improved, and 7 patients were classified as unchanged. Five patients who withdrew before month 7 were classified as treatment failures. Fludarabine caused a significant and prolonged lymphopenia without an increase in infectious complications over that seen with other immunosuppressive agents used for myositis. A sudden death of one patient at the end of the study was not thought to be drug related. Variables followed during the study emphasized the distinction between patient functional improvement and disease remission. CONCLUSION: A subset of patients with refractory myositis may benefit from fludarabine therapy and controlled trials are indicated. Refinement and validation of variables useful for following myositis patients await larger studies.

Adult↗
PubMed1998

Treatment of refractory myositis: a randomized crossover study of two new cytotoxic regimens.

OBJECTIVE: To assess the clinical usefulness of 2 novel therapies for treatment-resistant myositis. METHODS: Thirty patients with refractory myositis, of whom 25 had an inadequate or no response to previous cytotoxic therapy, were randomized to begin either a combination of weekly oral methotrexate and daily azathioprine (MTX/AZA) or intravenous methotrexate with leucovorin rescue (I.V. MTX) every 2 weeks for 6 months. Crossover to the alternate therapy occurred according to defined rules; evaluations of muscle strength and functional abilities were performed at the beginning, and after 3 and 6 months, of each treatment. RESULTS: Of the 15 patients initially randomized to oral MTX/AZA, 8 improved with oral therapy and 1 improved with I.V. MTX during the crossover period. Of the 15 patients initially randomized to I.V. MTX therapy, 3 improved with the I.V. therapy and 4 with the oral combination during the crossover period. Although the study lacked the power to directly compare both treatments, intention-to-treat analysis showed a trend in favor of those patients who first received oral combination therapy (P = 0.025). There were 0.09 adverse events per patient-month with oral combination therapy and 0.16 per patient-month with I.V. therapy (P = 0.09). CONCLUSION: Combination oral MTX/AZA may benefit patients with treatment-resistant myositis, including those who previously had inadequate responses to either MTX or AZA alone. I.V. MTX with leucovorin rescue may also benefit some patients with refractory myositis.

Administration, Oral↗
PubMed1998

Familial autoimmunity in pedigrees of idiopathic inflammatory myopathy patients suggests common genetic risk factors for many autoimmune diseases.

OBJECTIVE: To test the hypothesis that many autoimmune diseases share common genetic risk factors and to define the frequency and distribution of autoimmune diseases in relatives of patients with very rare disorders, the idiopathic inflammatory myopathies (IIM). METHODS: We evaluated, in a prospective case-control study, consecutive patients with IIM who were referred to our center and ascertained without regard to family history or known risk factors for autoimmunity, and all available family members. We used a standardized assessment to determine the presence and type of autoimmune disease in each subject. A matched comparison group of control subjects without autoimmune disease who were referred to our center and their families were similarly assessed. RESULTS: Autoimmune diseases were significantly increased in prevalence (21.9%) in the 151 first-degree relatives of the 21 IIM probands compared with the prevalence (4.9%) in the 143 relatives of the 21 control probands (odds ratio [OR] by regression analysis 7.9, 95% confidence interval [95% CI] 2.9-21.9, P < 0.001). Women had more autoimmune disease than men (OR by regression analysis 4.6, 95% CI 2.3-9.0) and the odds ratio for autoimmune disease increased 0.02 per year of age. These disorders tended to follow the frequency distribution of autoimmune diseases in the general population. Genetic modeling studies showed that a non-Mendelian polygenic inheritance pattern for autoimmune disease was most consistent with these data. CONCLUSION: Autoimmune diseases are significantly increased in frequency in first-degree relatives of IIM patients, affect more women than men, increase with age, and are distributed in a pattern similar to that in the general population. Many autoimmune disorders share genes that together act as polygenic risk factors for autoimmunity.

Adolescent↗
PubMed1997

Retroviral transfer of acid alpha-glucosidase cDNA to enzyme-deficient myoblasts results in phenotypic spread of the genotypic correction by both secretion and fusion.

Myoblasts have properties that make them suitable vehicles for gene replacement therapy, and lysosomal storage diseases are attractive targets for such therapy. Type II Glycogen Storage Disease, a deficiency of acid alpha-glucosidase (GAA), results in the abnormal accumulation of glycogen in skeletal and cardiac muscle lysosomes. The varied manifestations of the enzyme deficiency in affected patient are ultimately lethal. We used a retroviral vector carrying the cDNA encoding for GAA to replace the enzyme in deficient myoblasts and fibroblasts and analyzed the properties of the transduced cells. The transferred gene was efficiently expressed, and the de novo-synthesized enzyme reached lysosomes where it digested glycogen. In enzyme-deficient myoblasts after transduction, enzyme activity rose to more than 30-fold higher than in normal myoblasts and increased about five-fold more when the cells were allowed to differentiate into myotubes. The transduced cells secreted GAA that was endocytosed via the mannose-6-phosphate receptor into lysosomes of deficient cells and digested glycogen. Moreover, the transduced myoblasts were able to fuse with and provide enzyme for GAA-deficient fusion partners. Thus, the gene-corrected cells, which appear otherwise normal, may ultimately provide phenotypic correction to neighboring GAA-deficient cells by fusion and to distant cells by secretion and uptake mechanisms.

Cell Fusion↗
PubMed1997

Glycogenosis type II: a juvenile-specific mutation with an unusual splicing pattern and a shared mutation in African Americans.

The recessively inherited deficiency of acid alpha-glucosidase (GAA) called Glycogenosis Type II is expressed as three different phenotypes: infantile, juvenile, and adult. At the molecular level, infantile and adult forms of the disease have been extensively studied, but little is known regarding the genetic defects associated with the juvenile form. We describe a novel mutation that defines the intermediate juvenile phenotype in a compound heterozygous patient. A transversion of t to g in intron 6 at position -22 creates a cryptic acceptor site and results in unusual splicing abnormality: insertion of 21 nucleotides of the intronic sequence into mRNA and removal of exon 6 without disruption of the reading frame. The second mutation, Arg854Stop in exon 18, had been previously identified in another African-American patient (Hermans et al., 1993a). Family study indicates that a silent allele harboring the Arg854Stop mutation in our patient is inherited from the patient's father, who is also African-American, thus suggesting a common mutation in this population.

Base Sequence↗
PubMed1997

The predominance of beta (CC) chemokine transcripts in idiopathic inflammatory muscle diseases.

Cytokines and chemokines that upregulate major histocompatibility complex class I antigens, recruit lymphocytes, and enhance T-cell-mediated myotoxicity may be important in the pathogenesis of dermatomyositis and polymyositis. We searched for cytokine and chemokine transcripts in inflammatory muscle specimens from 14 newly diagnosed or treated patients. Control specimens from six patients without inflammatory muscle disease were analyzed for transcripts of interleukins-1 beta, -2, -4, -6, -10, and -15, and interferon-gamma, tumor necrosis factor-alpha, transforming growth factor-beta 1, macrophage inflammatory proteins-1 alpha and -1 beta (MIP-1 alpha, MIP-1 beta), and the chemokine "regulated on activation, normally T expressed and secreted" (RANTES). Surprisingly, the proinflammatory and lymphocyte cytokines were detected only sporadically in myositis muscle specimens, and their presence did not correlate with disease activity or treatment status of the patient. In contrast, MIP-1 alpha and MIP-1 beta were detected in 13 and 6 myositis biopsies, respectively, and RANTES, another beta (CC) chemokine, was detected in eight myositis biopsies. This study and other reports of low levels of acute-phase cytokines in myositis patients suggest that the proinflammatory cytokines do not play a major role in ongoing muscle damage. The CC chemokines studied here, in particular MIP-1 alpha, might contribute to ongoing muscle inflammation, and the pathogenesis of inflammation in myositis may follow a previously unrecognized pathway.

Cells, Cultured↗