Preservative-free tafluprost in the treatment of open-angle glaucoma or ocular hypertension in India: a phase III clinical trial.

AIM: The aim of this study was to evaluate the efficacy and safety of preservative-free (PF) tafluprost compared with PF timolol in Indian subjects with open-angle glaucoma (OAG) or ocular hypertension. METHODS: This was a randomised, multicentre, double-masked, phase III trial. Subjects aged 18-80 years, following washout of current medication, with intraocular pressure (IOP) ≥ 24 and ≤ 36 mmHg in at least one eye were randomised in a 1:1 ratio to 0.0015% PF tafluprost or 0.5% PF timolol for 4 weeks. IOP was measured at 08:00, 10:00 and 16:00 hours at baseline and at weeks 2 and 4. The primary efficacy end-point was the mean diurnal IOP change from baseline at week 4, and PF tafluprost was considered non-inferior to PF timolol if the upper bound of the 95% confidence interval (CI) for between-treatment differences was ≤ 1.5 mmHg. The secondary end-point was the proportion of subjects with ≥ 25% reduction in IOP from baseline at week 4. RESULTS: In total, 190 subjects were randomised, 95 each, to PF tafluprost and PF timolol treatment. PF tafluprost was non-inferior to PF timolol with respect to diurnal IOP changes from baseline over 4 weeks. The mean PF tafluprost-PF timolol difference in the diurnal IOP change was -1.7 (95% CI -2.6 to -0.7), suggestive of superiority for PF tafluprost. The secondary end-point was achieved in a higher proportion of PF tafluprost group subjects. Both PF tafluprost and PF timolol were well-tolerated with similar incidences of adverse events. CONCLUSIONS: PF tafluprost was safe and efficacious in reducing IOP in Indian subjects.

NMDA but not non-NMDA excitotoxicity is mediated by Poly(ADP-ribose) polymerase.

Poly(ADP-ribose) polymerase (PARP-1), a nuclear enzyme that facilitates DNA repair, may be instrumental in acute neuronal cell death in a variety of insults including, cerebral ischemia, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism, and CNS trauma. Excitotoxicity is thought to underlie these and other toxic models of neuronal death. Different glutamate agonists may trigger different downstream pathways toward neurotoxicity. We examine the role of PARP-1 in NMDA- and non-NMDA-mediated excitotoxicity. NMDA and non-NMDA agonists were stereotactically delivered into the striatum of mice lacking PARP-1 and control mice in acute (48 hr) and chronic (3 week) toxicity paradigms. Mice lacking PARP-1 are highly resistant to the excitoxicity induced by NMDA but are as equally susceptible to AMPA excitotoxicity as wild-type mice. Restoring PARP-1 protein in mice lacking PARP-1 by viral transfection restored susceptibility to NMDA, supporting the requirement of PARP-1 in NMDA neurotoxicity. Furthermore, Western blot analyses demonstrate that PARP-1 is activated after NMDA delivery but not after AMPA administration. Consistent with the theory that nitric oxide (NO) and peroxynitrite are prominent in NMDA-induced neurotoxicity, PARP-1 was not activated in mice lacking the gene for neuronal NO synthase after NMDA administration. These results suggest a selective role of PARP-1 in glutamate excitoxicity, and strategies of inhibiting PARP-1 in NMDA-mediated neurotoxicity may offer substantial acute and chronic neuroprotection.

Dynamic regulation of neuronal NO synthase transcription by calcium influx through a CREB family transcription factor-dependent mechanism.

Neuronal nitric oxide (NO) synthase (nNOS) is dynamically regulated in response to a variety of physiologic and pathologic stimuli. Although the dynamic regulation of nNOS is well established, the molecular mechanisms by which such diverse stimuli regulate nNOS expression have not yet been identified. We describe experiments demonstrating that Ca(2+) entry through voltage-sensitive Ca(2+) channels regulates nNOS expression through alternate promoter usage in cortical neurons and that nNOS exon 2 contains the regulatory sequences that respond to Ca(2+). Deletion and mutational analysis of the nNOS exon 2 promoter reveals two critical cAMP/Ca(2+) response elements (CREs) that are immediately upstream of the transcription start site. CREB binds to the CREs within the nNOS gene. Mutation of the nNOS CREs as well as blockade of CREB function results in a dramatic loss of nNOS transcription. These findings suggest that nNOS is a Ca(2+)-regulated gene through the interactions of CREB on the CREs within the nNOS exon 2 promoter and that these interactions are likely to be centrally involved in the regulation of nNOS in response to neuronal injury and activity-dependent plasticity.

Nuclear targeting of mutant Huntingtin increases toxicity.

Huntington's disease is a neurodegenerative disorder resulting from expansion of the polyglutamine region in huntingtin. Although huntingtin is normally cytoplasmic, in affected brain regions proteolytic fragments of mutant huntingtin containing the polyglutamine repeat form intranuclear inclusions. Here, we examine the contribution of nuclear localization to toxicity by transiently transfecting neuro-2a cells with an N-terminal huntingtin fragment similar in size to that believed to be present in patients. The huntingtin fragment, HD-N63, was targeted either to the cytoplasm with a nuclear export signal (NES) or to the nucleus with a nuclear localization signal (NLS). The NES decreased the number of cells with aggregates in the nucleus while an NLS had the opposite effect. By cotransfecting HD-N63 with GFP as a marker, we observed direct cell loss with constructs containing expanded polyglutamine repeats. Compared to unmodified HD-N63-75Q, adding an NES reduced cell loss by 57% while an NLS increased cell loss by 111%. These results indicate that nuclear localization of mutant huntingtin fragments plays an important role in cell toxicity.

Truncated N-terminal fragments of huntingtin with expanded glutamine repeats form nuclear and cytoplasmic aggregates in cell culture.

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expanding CAG repeat coding for polyglutamine in the huntingtin protein. Recent data have suggested the possibility that an N-terminal fragment of huntingtin may aggregate in neurons of patients with HD, both in the cytoplasm, forming dystrophic neurites, and in the nucleus, forming intranuclear neuronal inclusion bodies. An animal model of HD using the short N-terminal fragment of huntingtin has also been found to have intranuclear inclusions and this same fragment can aggregate in vitro . We have now developed a cell culture model demonstrating that N-terminal fragments of huntingtin with expanded glutamine repeats aggregate both in the cytoplasm and in the nucleus. Neuroblastoma cells transiently transfected with full-length huntingtin constructs with either a normal or expanded repeat had diffuse cytoplasmic localization of the protein. In contrast, cells transfected with truncated N-terminal fragments showed aggregation only if the glutamine repeat was expanded. The aggregates were often ubiquitinated. The shorter truncated product appeared to form more aggregates in the nucleus. Cells transfected with the expanded repeat construct but not the normal repeat construct showed enhanced toxicity to the apoptosis-inducing agent staurosporine. These data indicate that N-terminal truncated fragments of huntingtin with expanded glutamine repeats can aggregate in cells in culture and that this aggregation can be toxic to cells. This model will be useful for future experiments to test mechanisms of aggregation and toxicity and potentially for testing experimental therapeutic interventions.

Rat muscle branched-chain ketoacid dehydrogenase activity and mRNAs increase with extracellular acidemia.

The rate-limiting enzyme in branched-chain amino acid catabolism is branched-chain ketoacid dehydrogenase (BCKAD). In rats fed NH4Cl to induce acidemia, we find increased basal BCKAD activity as well as maximal activity in skeletal muscle. Concurrently, there is a > 10-fold increase in mRNAs of BCKAD subunits in skeletal muscle plus an increase in cardiac muscle but not in liver or kidney. There was no increase in mRNA for malate dehydrogenase or for cytosolic glyceraldehyde-3-phosphate dehydrogenase. Evaluation of the translation capacity of BCKAD mRNAs in muscle of acidemic rats yielded more immunoreactive BCKAD whether the proteins were synthesized from muscle RNA using rabbit reticulocyte lysate or directly using postmitochondrial homogenates. Although the RNA from muscle of acidemic rats yielded twice as much BCKAD protein, we found no net increase in mitochondrial BCKAD protein in muscle by Western blotting. Because there is increased proteolysis in muscle of rats with acidemia, the increase in mRNA might be a mechanism to augment BCKAD synthesis and activity in muscle.

Thiamin-responsive maple syrup urine disease in a patient antigenically missing dihydrolipoamide acyltransferase.

Maple syrup urine disease results from inherited defects in human nuclear genes for branched chain alpha-ketoacid dehydrogenase, a mitochondrial multienzyme complex. Thiamin pyrophosphate is necessary for complex activity and a thiamin-responsive form of maple syrup urine disease is known. Here we demonstrate the use of [1-13C]leucine oxidation to [13C]O2 quantified in breath samples as a means of assessing whole body leucine oxidation. Analysis of cultured cells from this patient shows the antigenic lack of the E2 subunit, yet she gained branched chain alpha-ketoacid dehydrogenase activity in response to diet supplementation with pharmacologic doses of thiamin. These cultured cells were used to seek a molecular basis for the observed thiamin response. Despite normal thiamin transport in these cells, medium supplementation of up to 1000 thiamin/liter failed to increase complex activity or cause the antigenic appearance of the missing protein. This lack of response in cultured cells suggests that the observed whole body response to thiamin must be a tissue-specific effect in liver, muscle, or kidney. In addition, allele-specific detection of paternal and maternal mutations was used to genotype family members in this pedigree.

Structure of the gene encoding dihydrolipoyl transacylase (E2) component of human branched chain alpha-keto acid dehydrogenase complex and characterization of an E2 pseudogene.

We have determined the structural organization of the dihydrolipoyl transacylase (E2) gene of the human branched chain alpha-keto acid dehydrogenase complex. The single copy E2 gene spans approximately 68 kilobases of genomic DNA. The complete coding region consisting of the 5'- and 3'-untranslated regions, the mitochondrial targeting sequence (61 amino acids), and the mature E2 sequence (421 amino acids) are encoded by 11 exons ranging from 62 to 2239 base pairs. All the donor and acceptor splice sites conform to the gt-ag rule. Sequence analysis of the promoter-regulatory region showed the presence of a "CAAT box"-like sequence 537 bases upstream of the transcription initiation site. The "TATA box"-like sequence is absent. Also located in this region are sequences resembling glucocorticoid-responsive and cAMP-responsive elements, fat-specific elements, and Sp1- and AP-2-binding sites. Several sets of direct and inverted repeats are also present. Promoter assays using human hepatoma cells (Hep-G2) and Swiss mouse preadipocytes (3T3-L1) showed that a 4.1-kilobase PstI fragment upstream of the transcription start site confers high expression of the luciferase reporter gene. Moreover, an intronless E2 pseudogene was isolated. It corresponds to the complete mitochondrial presequence and the lipoyl-bearing domain that are encoded by exons I through IV of the functional E2 gene. However, the E2 pseudogene contains multiple base changes, deletions, and insertions, and is flanked by short direct repeats. The data indicate that the E2 pseudogene is a retroposon.

The complete cDNA sequence for dihydrolipoyl transacylase (E2) of human branched-chain alpha-keto acid dehydrogenase complex.

We have determined the complete nucleotide sequence for the cDNA encoding human dihydrolipoyl transacylase (E2) using the rapid amplification of cDNA ends (RACE) procedure. The full-length E2 cDNA is 3535 nucleotides in length. The coding region spans 1446 bp and the 3'-noncoding region spans 2074 bp. The latter contains three Alu repetitive sequences and two transcription termination sites.

Branched chain acyltransferase absence due to an Alu-based genomic deletion allele and an exon skipping allele in a compound heterozygote proband expressing maple syrup urine disease.

Branched chain alpha-ketoacid dehydrogenase assembles around a core of the acyltransferase components on the matrix side of the mitochondrial inner membrane. Autosomal recessive mutations in humans are known to decrease the function of this complex resulting in the clinical phenotype of maple syrup urine disease. Within this wide group of mutations are a subset which result in the antigenic absence of the acyltransferase protein of the complex. Here we describe two mutations in a compound heterozygote proband which result in this acyltransferase-negative phenotype. The mutant allele inherited from the father lacks 15-20 kilobases of genomic DNA resulting from a recombinational event between an intronic Alu sequence and coding sequence in the terminal exon. The mother's mutant allele contains a single base substitution in the -1 position of the 5' splice junction following exon 8. This G1002----A transition results in exon skipping producing two different mRNAs. The first lacks only exon 8 while the second lacks exons 8-10. All mRNAs for the acyltransferase found in cells from the proband have the potential to produce proteins ranging in size from 251-395 amino acids, the largest being 26 amino acids short of a full-length acyltransferase. The potential of these transcripts to produce protein is of interest since the patient is clinically responsive to pharmacologic treatment with thiamin, showing a higher tolerance to protein in the diet. The mechanism for this thiamin response remains to be explained.

Molecular genetic basis of maple syrup urine disease in a family with two defective alleles for branched chain acyltransferase and localization of the gene to human chromosome 1.

Maple syrup urine disease in humans results from inherited defects in branched chain alpha-ketoacid dehydrogenase, a mitochondrial multienzyme complex. A variety of genetic changes may produce this phenotype by affecting the function of any of the three complex-specific subunits. The varied clinical expression observed in patients may be partially explained by the defects in the involved subunit. Here we report localization of the gene for the branched chain acyltransferase component of the complex to human chromosome 1 and describe a proband who is a compound heterozygote at this locus. One allele, inherited from the father, produces transcripts with 124 nucleotides deleted from the coding region. The deletion is not found in the branched chain acyltransferase gene, implying that the deleted transcripts arise by an error in transcript processing. Cells from the patient's mother contain 50% of the normal amount of mRNA for the subunit, and the proband has inherited this nonexpressing allele from her. As a result, the proband produces no acyltransferase protein and therefore has greatly impaired complex activity. A phenotypically normal sibling is shown to be genetically similar to the mother having inherited the mother's nonexpressing allele and the father's normal allele.

Reversion of the maple syrup urine disease phenotype of impaired branched chain alpha-ketoacid dehydrogenase complex activity in fibroblasts from an affected child.

Branched chain alpha-ketoacid dehydrogenase is a heteroprotein complex of mitochondria and commits the branched chain alpha-ketoacids to their catabolic fate. Inherited nuclear mutations in humans decrease the activity of this complex and result in maple syrup urine disease. Here we demonstrate the restoration of branched chain alpha-ketoacid dehydrogenase activity to fibroblasts from a child with this disorder by transfection with a cDNA for the prebranched chain acyltransferase. Prior to transfection these fibroblasts contained the prebranched chain acyltransferase gene but failed to transcribe the gene and thus lacked the protein. Regulation of the restored complex by phosphorylation mechanisms resembles that of wild-type cells. These results describe a human cell modeling system for testing engineered proteins and support the possibility of gene replacement therapy for this human disorder.

Construction and nucleotide sequence of a cDNA encoding the full-length preprotein for human branched chain acyltransferase.

A cDNA (1.6 kilobases) for branched chain acyltransferase (E2b) isolated from a human liver library encoded only the amino-terminal half of the protein (Hummel, K. B., Litwer, S., Bradford, A. P., Aitken, A., Danner, D. J., and Yeaman, S. J. (1988) J. Biol. Chem. 263, 6165-6168). Here we report the isolation of other cDNAs which encode the carboxyl-terminal half of E2b and the construction of a cDNA which encodes the entire pre-E2b. cDNA from the original clone encoding the leader sequence, lipoate binding domain, and E3 binding domain was ligated to the cDNA from a clone which by restriction maps contained an additional 3' sequence. Both cDNAs used in the construct made a fusion protein in their original phage isolate recognized by antibodies to E2b. The nucleotide sequence of the constructed cDNA was determined, and the 1431 base pairs in the open reading frame encoded a protein of 477 amino acids. In vitro transcription and translation of this cDNA produced a 57-kDa protein recognized by E2b-specific antibodies. Mouse liver mitochondria imported and processed the 57-kDa protein to a 52-kDa antigenic protein which co-migrated with E2b isolated from tissue. Comparing the protein structure of this human pre-E2b protein with that for other acyltransferase proteins showed a similarity in structure throughout all the proteins suggesting evolutionary conservation. Branched chain acyltransferase from Pseudomonas putida showed the most similarity to human E2b.