L-carnitine protects neurons from 1-methyl-4-phenylpyridinium-induced neuronal apoptosis in rat forebrain culture.

1-Methyl-4-phenylpyridinium ion (MPP+), an inhibitor of mitochondrial complex I, has been widely used as a neurotoxin because it elicits a severe Parkinson's disease-like syndrome with an elevation of intracellular reactive oxygen species (ROS) and apoptosis. L-carnitine plays an integral role in attenuating the brain injury associated with mitochondrial neurodegenerative disorders. The present study investigates the effects of L-carnitine against the toxicity of MPP+ in rat forebrain primary cultures. Cells in culture were treated for 24 h with 100, 250, 500 and 1000 microM MPP+ alone or co-incubated with L-carnitine. MPP+ produced a dose-related increase in DNA fragmentation as measured by cell death ELISA (enzyme-linked immunosorbent assay), an increase in the number of TUNEL (terminal dUTP nick-end labeling)-positive cells and a reduction in the mitochondrial metabolism of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). No significant effect was observed with the release of lactate dehydrogenase (LDH), indicating that cell death presumably occurred via apoptotic mechanisms. Co-incubation of MPP+ with L-carnitine significantly reduced MPP+-induced apoptosis. Western blot analyses showed that neurotoxic concentrations of MPP+ decreased the ratio of BCL-X(L) to Bax and decreased the protein levels of polysialic acid neural cell adhesion molecules (PSA-NCAM), a neuron specific marker. L-carnitine blocked these effects of MPP+ suggesting its potential therapeutic utility in degenerative disorders such as Parkinson's disease, Alzheimer's disease, ornithine transcarbamylase deficiency and other mitochondrial diseases.

Selective alterations of transcription factors in MPP+-induced neurotoxicity in PC12 cells.

MPP(+) (1-methyl-4-phenylpyridinium; the active metabolite of the neurotoxin MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine)) depletes dopamine (DA) content and elicits cell death in PC12 cells. However, the mechanism of MPP(+)-induced neurotoxicity is still unclear. In this study, the dose response and time-course of MPP(+)-induced DA depletion and decreased cell viability were determined in nerve growth factor (NGF)-differentiated PC12 cells. The alteration of transcription factors (TFs) induced by MPP(+) from a selected dose level and time point was then evaluated using protein/DNA-binding arrays. K-means clustering analysis identified four patterns of protein/DNA-binding changes. Three of the 28 TFs identified in PC12 cells increased by 100% (p53, PRE, Smad SBE) and 2 decreased by 50% (HSE, RXR(DR1)) of control with MPP(+) treatment. In addition, three TFs decreased within the range of 33-50% (TFIID, E2F1, CREB) and two TFs increased within the range of 50-100% (PAX-5, Stat4). An electrophoretic mobility shift assay (EMSA) was used to confirm the changes of p53 and HSE. The observed changes in TFs correlated with the alterations of DA and cell viability. The data indicates that selective transcription factors are involved in MPP(+)-induced neurotoxicity and it provides mechanistic information that may be applicable to animal studies with MPTP and clinical studies of Parkinson's disease.

Polymorphisms in the human DNA ligase I gene (LIG1) including a complex GT repeat.

Sequencing of a human DNA ligase I cDNA clone derived from HeLa cells revealed two unreported differences with the published sequence: a single base change and a three-base deletion. Both differences are in exon 6, and were analyzed by amplifying a segment containing exon 5, intron 6, and exon 6. The first finding was that intron 6 is approximately 2.6 kb in size, not the 1 kb reported in the literature. By sequence analysis of amplified segments, the single-base difference in exon 6 was shown to be polymorphic, with HeLa cells heterozygous for the A/C difference. Analysis of 60 unrelated individuals found a frequency of 0.5 for each allele. Primer extension reactions across the exon 5/exon 6 boundary were performed on cDNA obtained from HeLa cells and human thymus. The results show that the three-base deletion is due to a variation in splicing. For both HeLa and thymus, two-thirds of the transcripts are like the published cDNA sequence and one-third have the three-base deletion. Finally, sequencing of part of intron 6 revealed the presence of a complex GT repeat consisting of a 48-50 nucleotide polypurine tract followed by a variable number of GT residues. This entire unit of polypurine tract plus GTs is repeated three times. Detection of the repeated sequences required the development of specialized cloning and PCR conditions. Analysis of a pedigree showed that this complex repeat is polymorphic.

Simultaneous quantitation of arecoline, acetylcholine, and choline in tissue using gas chromatography/electron impact mass spectrometry.

A capillary gas chromatography/mass spectrometry (GC/MS) assay for the simultaneous quantitation of arecoline (ARE), acetylcholine (ACh), and choline (Ch) in biological tissue has been developed. The method utilizes hexadeuterated ARE and nonadeuterated ACh and Ch as internal standards. The compounds were ion-pair extracted from tissue using sodium tetraphenylboron in 3-heptanone. GC/MS analysis was achieved using capillary GC and electron impact mass spectrometry. Quantitation was accomplished using selected ion monitoring at m/z 140 and 146 for non-deuterated and deuterated arecoline respectively, and m/z 58 and 64 for non-deuterated and deuterated ACh and Ch respectively. The method easily detected 25 pmol of all three compounds taken through the assay, and was linear through 50 nmol.

Deletion of hydrophobic domains of viral glycoproteins increases the level of their production in Escherichia coli.

Overexpression of glycoprotein-encoding genes in Escherichia coli sometimes results in toxicity to the host and low protein yields. One possible explanation for this phenomenon is the presence of hydrophobic amino acid (aa) domains approx. 15-20 aa in length in the overproduced protein. As an initial test of this hypothesis, regions of hydrophobicity located within the envelope glycoproteins of HIV-1 and HTLV-1 were identified by computer analysis, and subsequently deleted by site-directed mutagenesis. The parent and modified envelope genes were expressed in bacteria using both lambda pL and T7 inducible expression systems. Removal of the hydrophobic domains reduced the apparent toxicity and significantly increased the accumulation of recombinant protein from undetectable levels to approx. 10-15% of total cellular protein.