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Biomedical subjects

John F Engelhardt

Publications and source records attributed to John F Engelhardt.

At least 55 records · Page 3Linked to original sources
PubMed2003

Developmental capacity of ferret embryos by nuclear transfer using G0/G1-phase fetal fibroblasts.

With the ultimate goal of establishing experimental protocols necessary for cloning ferrets, the present study has established parameters for the reconstruction of ferret embryos by nuclear transfer (NT) using G0/G1-phase donor fetal fibroblasts. Cumulus-oocyte complexes were harvested from superovulated ferrets and cultured in maturation medium for 24 h. Matured oocytes were then enucleated and injected with the fibroblast nuclei derived from 14-16-h serum-starved cells. Reconstructed embryos were then activated by a combination of electric pulses and chemical stimulations. Subsequently, the reconstructed and activated embryos were either cultured in vitro or transferred to pseudopregnant ferrets to evaluate their developmental capacity in vitro and in vivo. Our results demonstrated that 56.3% of reconstructed embryos (n = 187) cleaved, while 26.0% and 17.6% developed to morula and blastocyst phases in vitro, respectively. The blastocysts derived from NT embryos demonstrated normal morphology by differentially staining as compared to normal blastocysts developed in vivo following fertilization. In vivo developmental studies at 21 days posttransplantation demonstrated 8.8% of reconstructed embryos (n = 91) implanted into the uterine lining of recipients, while 3.3% formed fetuses. However, reconstructed embryos (n = 387) failed to develop to term (42 days). These results demonstrate donor nuclei of G0/G1-phase fetal fibroblast cells can be reprogrammed to support the development of reconstructed ferret embryos in vitro and in vivo; however, a significant third-trimester block occurs preventing full-term development.

Animals↗
PubMed2003

Efficiency of chimeraplast gene targeting by direct nuclear injection using a GFP recovery assay.

Traditional RNA-DNA chimeric oligonucleotides (chimeraplasts), composed of a continuous stretch of RNA and DNA residues in a duplex conformation, have been shown to correct single-base mutations in episomal and genomic DNA both in vitro and in vivo. In the current study, we have compared the efficiency of single-base pair correction between a traditionally designed chimeraplast (covalently linked duplex) and hybrid chimeraplasts (noncovalent duplexes formed from stretches of RNA and DNA nucleotides synthesized individually and hybridized in vitro). Six hybrid chimeraplasts of identical length were constructed with various lengths of target homology and strand location of the desired nucleotide change. These constructs were evaluated for their ability to correct a point mutation in the gene encoding recombinant enhanced green fluorescent protein (eGFP) that rendered the protein nonfluorescent. A plasmid encoding this mutant eGFP gene and a chimeraplast were co-introduced directly into the nuclei of primary fibroblasts by microinjection. As shown by the recovery of eGFP fluorescence, three of the six hybrid chimeraplasts demonstrated the ability to mediate gene correction (0.4-2.4%). Covalent joining of RNA and DNA strands in chimeraplasts was not necessary for correction of DNA mutations. However, the strand placement of the desired nucleotide change and the length of nonhomologous sequences flanking target nucleotides played a crucial role in the efficiency of chimeraplast-mediated gene correction. Despite the ability of certain chimeraplast designs to correct point mutations in episomal plasmids, targeted correction of integrated copies of the mutant eGFP transgene was unsuccessful in primary fibroblasts. These results demonstrate that, although chimeraplasts are fairly effective at targeting episomal DNA in primary cells, further optimization is required to increase the efficiency for targeting integrated genes.

Base Sequence↗
PubMed2003

Genetic redox preconditioning differentially modulates AP-1 and NF kappa B responses following cardiac ischemia/reperfusion injury and protects against necrosis and apoptosis.

Reactive oxygen species have been established as key mediators of cardiac injury following ischemia/reperfusion (I/R). We hypothesized that superoxide formation at different subcellular locations following cardiac I/R injury may differentially regulate cellular responses that determine pathophysiologic outcomes. Recombinant adenoviruses expressing Cu/ZnSOD or MnSOD were utilized to modulate superoxide levels in the cytoplasmic or mitochondrial compartments, respectively, prior to coronary artery I/R injury in the rat heart. Ectopic expression of both MnSOD and Cu/ZnSOD afforded protection from I/R injury, as evidenced by a significant reduction in serum creatine kinase levels, infarct size, malondialdehyde levels, and apoptotic cell death in comparison to controls. MnSOD and Cu/ZnSOD expression also significantly altered the kinetics of NF kappa B and AP-1 activation following I/R injury, characterized by a delayed induction of NF kappa B and abrogated AP-1 response. Western blot analysis of Bcl-2, Bcl-xL, Bad, Caspase 3, PDK1, and phospho-Akt also revealed SOD-mediated changes in gene expression consistent with protection and decreased apoptosis. These findings support the notion that both mitochondrial and cytoplasmic-derived SOD induce changes in AP-1 and NF kappa B activity, creating an antiapoptotic microenvironment within cardiomyocytes that affords protection following I/R injury.

Adenoviridae↗
PubMed2003

Second-strand genome conversion of adeno-associated virus type 2 (AAV-2) and AAV-5 is not rate limiting following apical infection of polarized human airway epithelia.

Recombinant adeno-associated virus type 5 (rAAV-5) is known to efficiently transduce airway epithelia via apical infection. In contrast, rAAV-2 has been shown to be inherently ineffective at transducing airway epithelia from the apical surface. However, tripeptide proteasome inhibitors (such as LLnL) can dramatically enhance rAAV-2 transduction from the apical surface of human polarized airway epithelia by modulating the intracellular trafficking and processing of the virus. To further investigate potential differences between rAAV-2 and rAAV-5 that might explain their altered ability to transduce airway epithelia from the apical membrane, we examined the functional involvement of the ubiquitin/proteasome pathway and rate-limiting aspects of second-strand synthesis for these two rAAV serotypes. To this end, we conducted studies to compare the extent to which LLnL alters transduction efficiencies with both rAAV-2 and rAAV-2/5 by using luciferase and enhanced green fluorescent protein (EGFP) reporter vectors. Our results demonstrate that the coadministration of LLnL at the time of viral infection significantly enhanced transduction of both rAAV-2/5 and rAAV-2 from the apical surface of airway epithelia. Although rAAV-2/5 was slightly more effective at transducing epithelia from the apical membrane, rAAV-2 transduction was superior to that of rAAV-2/5 in the presence of proteasome inhibitors. Interestingly, the basolateral membrane entry pathways for both serotypes were not significantly affected by the addition of LLnL, which suggests that apical and basolateral infectious pathways possess distinctive intracellular processing pathways for both rAAV-2 and rAAV-5. Studies comparing the transduction of short self-complementary (scAAV) to full-length conventional AAV EGFP vectors suggested that second-strand synthesis of rAAV genomes was not rate limiting for either serotype or altered by proteasome inhibitors following apical infection of polarized airway epithelia. These findings suggest that both rAAV-2 and rAAV-5 share similar intracellular viral processing barriers that involve the ubiquitin/proteasome system, but do not appear to involve second-strand synthesis.

Bronchi↗
PubMed2003

Consequences of DNA-dependent protein kinase catalytic subunit deficiency on recombinant adeno-associated virus genome circularization and heterodimerization in muscle tissue.

Circular concatemerization of the recombinant adeno-associated virus (rAAV) genome has been suggested as the predominant process facilitating long-term rAAV transduction in muscle. A recent study (S. Song, P. J. Laipis, K. I. Berns, and T. R. Flotte, Proc. Natl. Acad. Sci. USA 98:4084-4088, 2001) with SCID mice, which are defective in the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), has suggested that DNA-PKcs regulates the removal of free rAAV vector ends in muscle tissue. In the present study, we have sought to evaluate whether a lack of DNA-PKcs activity reduces circularization of rAAV genomes in SCID muscle and whether such a reduction alters the directivity of heterodimerization. Consistent with the previous report, linear rAAV genomes and free vector ends were detected only in DNA-PKcs-deficient muscle by Southern blotting. Appreciable amounts of circular rAAV genomes were detected in both DNA-PKcs-deficient and wild-type muscle samples by Southern blotting and bacterial trapping experiments. The existence of double-D inverted terminal repeat circular intermediates in SCID and wild-type muscles was also supported by their sensitivity to T7 endonuclease I digestion. However, DNA-PKcs-deficient muscle did demonstrate a approximately 50% reduction in the abundance of rescued circular genomes, despite equivalent levels of single rAAV transduction seen in wild-type animals. Dual trans-splicing lacZ vectors were used to functionally evaluate directional head-to-tail intermolecular viral genome concatamerization in vivo. Although AAV genomes are processed differently in SCID and wild-type muscles, a comparable level of trans-splicing-mediated beta-galactosidase expression was observed in both strains, suggesting that both circular and linear AAV concatemers may have contributed to the trans-splicing-mediated transgene expression. In summary, we have shown that SCID skeletal muscle retains a fairly high capacity to form circular genomes, despite a significant increase in linear vector genomes. Furthermore, the alteration in equilibrium between circular and linear concatemer genomes caused by the lack of DNA-PKcs activity does not appear to significantly affect the efficiency of dual-vector gene expression from head-to-tail linear and/or circular heterodimers.

Animals↗
PubMed2003

Bile acid regulation of C/EBPbeta, CREB, and c-Jun function, via the extracellular signal-regulated kinase and c-Jun NH2-terminal kinase pathways, modulates the apoptotic response of hepatocytes.

Previously, we have demonstrated that deoxycholic acid (DCA)-induced signaling of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in primary hepatocytes is a protective response. In the present study, we examined the roles of the ERK and c-Jun NH(2)-terminal kinase (JNK) pathways, and downstream transcription factors, in the survival response of hepatocytes. DCA caused activation of the ERK1/2 and JNK1/2 pathways. Inhibition of either DCA-induced ERK1/2 or DCA-induced JNK1/2 signaling enhanced the apoptotic response of hepatocytes. Further analyses demonstrated that DCA-induced JNK2 signaling was cytoprotective whereas DCA-induced JNK1 signaling was cytotoxic. DCA-induced ERK1/2 activation was responsible for increased DNA binding of C/EBPbeta, CREB, and c-Jun/AP-1. Inhibition of C/EBPbeta, CREB, and c-Jun function promoted apoptosis following DCA treatment, and the level of apoptosis was further increased in the case of CREB and c-Jun, but not C/EBPbeta, by inhibition of MEK1/2. The combined loss of CREB and c-Jun function or of C/EBPbeta and c-Jun function enhanced DCA-induced apoptosis above the levels resulting from the loss of either factor individually; however, these effects were less than additive. Loss of c-Jun or CREB function correlated with increased expression of FAS death receptor and PUMA and decreased expression of c-FLIP-(L) and c-FLIP-(S), proteins previously implicated in the modulation of the cellular apoptotic response. Collectively, these data demonstrate that multiple DCA-induced signaling pathways and transcription factors control hepatocyte survival.

Amino Acid Sequence↗
PubMed2002

Temporal pattern of NFkappaB activation influences apoptotic cell fate in a stimuli-dependent fashion.

The transcription factor NFkappaB is a critical immediate early response gene involved in modulating cellular responses and apoptosis following diverse environmental injuries. The activation of NFkappaB is widely accepted to play an anti-apoptotic role in cellular responses to injury. Hence, enhancing NFkappaB activation in the setting of injury has been proposed as one potential therapeutic approach to environmental injuries. To this end, we constructed a recombinant adenoviral vector (Ad.IkappaBalphaAS) expressing antisense IkappaBalpha mRNA that is capable of augmenting NFkappaB activation prior to and following four types of cellular injury [TNF-alpha, UV, hypoxia/reoxygenation (H/R) or pervanadate treatment]. Biochemical and functional analyses of NFkappaB activation pathways for these injuries demonstrated two categories involving either serine (S32/36) phosphorylation (TNF-alpha, UV) or tyrosine (Y42) phosphorylation (H/R or PV) of IkappaBalpha. We hypothesized that activation of NFkappaB prior to injury using antisense IkappaBalpha mRNA would reduce apoptosis. As anticipated, recombinant adenoviral IkappaBalpha phosphorylation mutants (Ad.IkappaBalphaS32/36A or Ad.IkappaBalphaY42F) preferentially reduced NFkappaB activation and enhanced apoptosis following injuries associated with either serine or tyrosine phosphorylation of IkappaBalpha, respectively. These studies demonstrate for the first time that an IkappaBalphaY42F mutant can effectively modulate NFkappaB-mediated apoptosis in an injury-context-dependent manner. Interestingly, constitutive activation of NFkappaB following Ad.IkappaBalphaAS infection reduced apoptosis only following injuries associated with IkappaBalpha Y42, but not S32/36, phosphorylation. These findings demonstrate that the temporal regulation of NFkappaB and the apoptotic consequences of this activation are differentially influenced by the pathway mediating NFkappaB activation. They also provide new insight into the therapeutic potential and limitations of modulating NFkappaB for environmental injuries such as ischemia/reperfusion and pro-inflammatory diseases.

Apoptosis↗
PubMed2002

First-generation adenovirus vectors shorten survival time in a murine model of sepsis.

Adverse immunological reactions to adenoviral vectors have significantly impacted the utility of this virus for treating genetic and environmentally induced diseases. In this study, we evaluate the effect of adenoviral vectors on an animal model of sepsis. Systemic delivery of first-generation adenoviral vectors to septic mice (cecal ligation and puncture) resulted in a shortened survival time. This effect was not observed with second-generation or inactivated first-generation vectors. The accelerated death was accompanied by a number of important changes in the disease. These changes included increased liver cell apoptosis (including Kupffer cells) and a marked increase in liver bacterial load. In the lung, the combination induced an increase in bacterial load, as well as greater lung injury. In the serum, the combination was associated with decreased TNF-alpha levels and an increase in bacterial load. Finally, a profound degree of lymphocyte apoptosis was observed in these animals. These observations suggest that prior exposure to first-generation adenovirus gene therapy vectors may worsen the outcome of some forms of sepsis.

Adenoviridae↗
PubMed2002

Tyrosine phosphorylation of I kappa B alpha activates NF kappa B through a redox-regulated and c-Src-dependent mechanism following hypoxia/reoxygenation.

NF kappa B is a critical transcription factor involved in modulating cellular responses to environmental injuries. Tyrosine 42 phosphorylation of I kappa B alpha has been shown to mediate NF kappa B activation following hypoxia/reoxygenation (H/R) or pervanadate treatment. This pathway differs from the canonical proinflammatory pathways, which mediate NF kappa B activation through serine phosphorylation of I kappa B alpha by the IKK complex. In the present study, we investigated the involvement of c-Src in the redox activation of NFkappaB following H/R or pervanadate treatment. Our results demonstrate that pervanadate or H/R treatment leads to tyrosine phosphorylation of I kappa B alpha and NF kappa B transcriptional activation independent of the IKK pathway. In contrast, inhibition of c-Src by pp2 treatment or in c-Src (-/-) knockout cell lines, demonstrated a significant reduction in I kappa B alpha tyrosine phosphorylation and NF kappa B activation following pervanadate or H/R treatment. Overexpression of glutathione peroxidase-1 or catalase, but not Mn-SOD or Cu,Zn-SOD, significantly reduced both NF kappa B activation and tyrosine phosphorylation of I kappa B alpha. In vitro kinase assays further demonstrated that immunoprecipitated c-Src has the capacity to directly phosphorylate GST-I kappa B alpha and that this I kappa B alpha kinase activity is significantly reduced by Gpx-1 overexpression. These results suggest that c-Src-dependent tyrosine phosphorylation of I kappa B alpha and subsequent activation of NF kappa B is controlled by intracellular H(2)O(2) and defines an important redox-regulated pathway for NF kappa B activation following H/R injury that is independent of the IKK complex.

Hypoxia↗
PubMed2002

Wnt-3A/beta-catenin signaling induces transcription from the LEF-1 promoter.

Members of the Wnt family of secreted molecules have been established as key factors in determining cell fate and morphogenic signaling. It has long been recognized that Wnt induces morphogenic signaling through the Tcf/LEF-1 cascade by regulating free intracellular levels of beta-catenin, a co-factor for Tcf/LEF-1 transcription factors. In the present study, we have demonstrated that Wnt-3A can also directly induce transcription from the LEF-1 promoter. This induction was dependent on glycogen synthase kinase 3beta inactivation, a rise in free intracellular beta-catenin, and a short 110-bp Wnt-responsive element (WRE) in the LEF-1 promoter. Linear and internal deletion of this WRE led to a dramatic increase in constitutive LEF-1 promoter activity and loss of Wnt-3A responsiveness. In isolation, the 110-bp WRE conferred context-independent Wnt-3A or beta-catenin(S37A) responsiveness to a heterologous SV40 promoter. Studies expressing dominant active and negative forms of LEF-1, beta-catenin, GSK-3beta, and beta-catenin/LEF-1 fusions suggest that Wnt-3A activates the LEF-1 promoter through a beta-catenin-dependent and LEF-1-independent process. Wnt-3A expression also induced multiple changes in the binding of factors to the WRE and suggests that regulatory mechanisms may involve modulation of a multiprotein complex. In summary, these results provide evidence for transcriptional regulation of the LEF-1 promoter by Wnt and enhance the mechanistic understanding of Wnt/beta-catenin signaling in the regulation of LEF-1-dependent developmental processes.

Base Sequence↗
PubMed2002

Current status of gene therapy for inherited lung diseases.

Gene therapy as a treatment modality for pulmonary disorders has attracted significant interest over the past decade. Since the initiation of the first clinical trials for cystic fibrosis lung disease using recombinant adenovirus in the early 1990s, the field has encountered numerous obstacles including vector inflammation, inefficient delivery, and vector production. Despite these obstacles, enthusiasm for lung gene therapy remains high. In part, this enthusiasm is fueled through the diligence of numerous researchers whose studies continue to reveal great potential of new gene transfer vectors that demonstrate increased tropism for airway epithelia. Several newly identified serotypes of adeno-associated virus have demonstrated substantial promise in animal models and will likely surface soon in clinical trials. Furthermore, an increased understanding of vector biology has also led to the development of new technologies to enhance the efficiency and selectivity of gene delivery to the lung. Although the promise of gene therapy to the lung has yet to be realized, the recent concentrated efforts in the field that focus on the basic virology of vector development will undoubtedly reap great rewards over the next decade in treating lung diseases.

Animals↗
PubMed2002

v-Ha-ras mitogenic signaling through superoxide and derived reactive oxygen species.

The ras proto-oncogene is frequently mutated in human tumors and functions to constitutively stimulate signal transduction cascades, resulting in unchecked proliferation and malignant transformation. In certain cells, superoxide functions as a signal-transduction messenger, mediating the downstream effects of ras and rac. We demonstrated previously that v-Ha-ras-transfected rat kidney epithelial cells (RECs) overproduced superoxide anion and that this superoxide production was mediated by ras. In the present study, we further demonstrated that v-Ha-ras overexpression transformed immortal nonmalignant RECs into malignant cancer cells; v-Ha-ras-transfected cells formed clones in soft agar, had high plating efficiency, and formed tumors in nude mice. Our data suggest that superoxide radical plays a role in ras-induced transformation; modulation of intracellular superoxide level by overexpression of manganese-containing superoxide dismutase or copper- and zinc-containing superoxide dismutase inhibited ras-induced transformation, as evidenced by in vitro studies of plating efficiency and by in vivo studies of tumor formation in nude mice. Overexpression of catalase (CAT) alone was found to have little effect on tumor cell growth, but overexpression of glutathione peroxidase 1 (GPx1) completely suppressed tumor cell growth in nude mice. This finding suggests that peroxides removed by GPx1, but not by CAT, are also involved in ras-induced transformation.

Animals↗
PubMed2002

Partial correction of endogenous DeltaF508 CFTR in human cystic fibrosis airway epithelia by spliceosome-mediated RNA trans-splicing.

Spliceosome-mediated RNA trans-splicing (SMaRT) was investigated as a means for functionally correcting endogenous DeltaF508 cystic fibrosis transmembrane conductance regulator (CFTR) transcripts using in vitro human cystic fibrosis (CF) polarized airway epithelia and in vivo human CF bronchial xenografts. Recombinant adenovirus (Ad.CFTR-PTM) encoding a pre-therapeutic molecule (PTM) targeted to CFTR intron 9 corrected transepithelial cyclic AMP (cAMP)-sensitive short-circuit current (Isc) in DeltaF508 homozygous epithelia to a level 16% of that observed in normal human bronchial epithelia. Molecular analyses using RT-PCR and western blotting confirmed SMaRT-mediated partial correction of endogenous DeltaF508 messenger RNA (mRNA) transcripts and protein. In an in vivo model of DeltaF508 CF airway epithelia, human CF bronchial xenografts infected with Ad.CFTR-PTM also demonstrated partial correction of CFTR-mediated Cl- permeability at a level 22% of that seen in non-CF xenografts. These results provide functional evidence for SMaRT-mediated repair of mutant endogenous CFTR mRNA in intact polarized CF airway epithelial models.

Adenoviridae↗
PubMed2002

Modular flexibility of dystrophin: implications for gene therapy of Duchenne muscular dystrophy.

Attempts to develop gene therapy for Duchenne muscular dystrophy (DMD) have been complicated by the enormous size of the dystrophin gene. We have performed a detailed functional analysis of dystrophin structural domains and show that multiple regions of the protein can be deleted in various combinations to generate highly functional mini- and micro-dystrophins. Studies in transgenic mdx mice, a model for DMD, reveal that a wide variety of functional characteristics of dystrophy are prevented by some of these truncated dystrophins. Muscles expressing the smallest dystrophins are fully protected against damage caused by muscle activity and are not morphologically different from normal muscle. Moreover, injection of adeno-associated viruses carrying micro-dystrophins into dystrophic muscles of immunocompetent mdx mice results in a striking reversal of histopathological features of this disease. These results demonstrate that the dystrophic pathology can be both prevented and reversed by gene therapy using micro-dystrophins.

Analysis of Variance↗