Biomedical subjects

Bert C Lynn

Publications and source records attributed to Bert C Lynn.

26 records · Page 2Linked to original sources

PubMed2005

Proteomic analysis of specific brain proteins in aged SAMP8 mice treated with alpha-lipoic acid: implications for aging and age-related neurodegenerative disorders.

Free radical-mediated damage to neuronal membrane components has been implicated in the etiology of Alzheimer's disease (AD) and aging. The senescence accelerated prone mouse strain 8 (SAMP8) exhibits age-related deterioration in memory and learning along with increased oxidative markers. Therefore, SAMP8 is a suitable model to study brain aging and, since aging is the major risk factor for AD and SAMP8 exhibits many of the biochemical findings of AD, perhaps as a model for and the early phase of AD. Our previous studies reported higher oxidative stress markers in brains of 12-month-old SAMP8 mice when compared to that of 4-month-old SAMP8 mice. Further, we have previously shown that injecting the mice with alpha-lipoic acid (LA) reversed brain lipid peroxidation, protein oxidation, as well as the learning and memory impairments in SAMP8 mice. Recently, we reported the use of proteomics to identify proteins that are expressed differently and/or modified oxidatively in aged SAMP8 brains. In order to understand how LA reverses the learning and memory deficits of aged SAMP8 mice, in the current study, we used proteomics to compare the expression levels and specific carbonyl levels of proteins in brains from 12-month-old SAMP8 mice treated or not treated with LA. We found that the expressions of the three brain proteins (neurofilament triplet L protein, alpha-enolase, and ubiquitous mitochondrial creatine kinase) were increased significantly and that the specific carbonyl levels of the three brain proteins (lactate dehydrogenase B, dihydropyrimidinase-like protein 2, and alpha-enolase) were significantly decreased in the aged SAMP8 mice treated with LA. These findings suggest that the improved learning and memory observed in LA-injected SAMP8 mice may be related to the restoration of the normal condition of specific proteins in aged SAMP8 mouse brain. Moreover, our current study implicates neurofilament triplet L protein, alpha-enolase, ubiquitous mitochondrial creatine kinase, lactate dehydrogenase B, and dihydropyrimidinase-like protein 2 in process associated with learning and memory of SAMP8 mice.

Aging↗

PubMed2004

Degradation of camptothecin-20(S)-glycinate ester prodrug under physiological conditions.

We have compared the strikingly different decomposition pathways for camptothecin-20(S)-acetate -acetate and camptothecin-20(S)-glycinate in phosphate buffered saline, human plasma and blood. The aliphatic ester analog camptothecin-20(S)-acetate demonstrated excellent stability in the above fluids for many hours with minimal hydrolysis, while the camptothecin-20(S)-glycinate analog (differing solely by the presence of an amino group) underwent rapid and essentially complete decomposition. Reversed-phase high performance liquid chromatography (RP-HPLC) with electrospray ionization-mass spectral (ESI-MS) detection was then used to correlate structural information for camptothecin-20(S)-glycinate decomposition products. ESI-MS detection indicated the ring-opened carboxylate form of camptothecin and the ring-opened degradation product co-elute near the solvent front, while the latest eluting decomposition product was the closed-ring lactone form of camptothecin. A novel decomposition product with intermediate retention time displayed an identical mass-to-charge ratio as camptothecin-20(S)-glycinate ester but a strikingly different fragmentation pattern. The LC-ESI-MS evidence of a novel camptothecin prodrug degradation pathway is provided in this report.

Antineoplastic Agents, Phytogenic↗

PubMed2004

Identification of nucleophosmin as an NF-kappaB co-activator for the induction of the human SOD2 gene.

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme essential for the survival of life. We have reported that NF-kappaB is essential but not sufficient for the synergistic induction of MnSOD by phorbol 12-myristate 13-acetate and cytokines. To further identify transcription factors and co-activators that participate in the induction of MnSOD, we used NF-kappaB affinity chromatography to isolate potential NF-kappaB interacting proteins. Proteins eluted from the NF-kappaB affinity column were subjected to proteomic analysis and verified by Western analysis. Nucleophosmin (NPM), a nucleolar phosphoprotein, is the most abundant single protein identified. Co-immunoprecipitation studies suggest a physical interaction between NPM and NF-kappaB proteins. To verify the role of NPM on MnSOD gene transcription, cells were transfected with constructs expressing NPM in sense or antisense orientation as well as interference RNA. The results indicate that an increase NPM expression leads to increased MnSOD gene transcription in a dose-dependent manner. Consistent with this, expression of small interfering RNA for NPM leads to inhibition of MnSOD gene transcription but does not have any effect on the expression of interleukin-8, suggesting that the effect of NPM is selective. These results identify NPM as a partner of the NF-kappaB transcription complex in the induction of MnSOD by phorbol 12-myristate 13-acetate and cytokines.

Blotting, Northern↗

PubMed2004

Factors that affect ion trap data-dependent MS/MS in proteomics.

Quadrupole ion trap scanning parameters for performing bottom-up proteomics in a data-dependent fashion were evaluated on a Finnigan LCQ Deca mass spectrometer. Evaluation of parameters such as the number of averaged full scans, the number of averaged MS/MS scans, and ion injection times were necessary for acquiring high quality MS/MS spectra that yield favorable b and y ion coverage and high correlation to proteins using database searching algorithms. In this study, we demonstrated how the duty cycle of the mass spectrometer affects the number of peptides that can be successfully identified by SEQUEST using a model system of tryptic BSA peptides to mimic a typical complex mixture associated with bottom-up proteomics. The number of averaged scans and the duration of ion accumulation in the trap had a significant effect on the quality of acquired MS/MS spectra. For example, by increasing the ion injection time from 500 ms to 600 ms, peptide HLVDEPQNLIK improved from being improperly identified to being correctly identified with a SEQUEST cross-correlation score of 3.60. As a result of these experiments, we have devised the following set of ion trap parameters for performing bottom-up proteomics analysis in our laboratory: Three averaged full scans, five averaged MS/MS scans, and a maximum ion injection time of 600 ms.

Amino Acid Sequence↗

PubMed2004

Proteomic analysis of brain proteins in the gracile axonal dystrophy (gad) mouse, a syndrome that emanates from dysfunctional ubiquitin carboxyl-terminal hydrolase L-1, reveals oxidation of key proteins.

Ubiquitin carboxyl-terminal hydrolase L-1 (UCH L-1) is a crucial enzyme for proteasomal protein degradation that generates free monomeric ubiquitin. Our previous proteomic study identified UCH L-1 as one specific target of protein oxidation in Alzheimer's disease (AD) brain, establishing a link between the effect of oxidative stress on protein and the proteasomal dysfunction in AD. However, it is unclear how protein oxidation affects function, owing to the different responses of proteins to oxidation. Analysis of systems in which the oxidized protein displays lowered or null activity might be an excellent model for investigating the effect of the protein of interest in cellular metabolism and evaluating how the cell responds to the stress caused by oxidation of a specific protein. The gracile axonal dystrophy (gad) mouse is an autosomal recessive spontaneous mutant with a deletion on chromosome 5 within the gene encoding UCH L-1. The mouse displays axonal degeneration of the gracile tract. The aim of this proteomic study on gad mouse brain, with dysfunctional UCH L-1, was to determine differences in brain protein oxidation levels between control and gad samples. The results showed increased protein oxidation in thioredoxin peroxidase (peroxiredoxin), phosphoglycerate mutase, Rab GDP dissociation inhibitor alpha/ATP synthase and neurofilament-L in the gad mouse brain. These findings are discussed with reference to the effect of specific protein oxidation on potential mechanisms of neurodegeneration that pertain to the gad mouse.

Animals↗

PubMed2003

An animal model of age-related macular degeneration in senescent Ccl-2- or Ccr-2-deficient mice.

The study and treatment of age-related macular degeneration (AMD), a leading cause of blindness, has been hampered by a lack of animal models. Here we report that mice deficient either in monocyte chemoattractant protein-1 (Ccl-2; also known as MCP-1) or its cognate C-C chemokine receptor-2 (Ccr-2) develop cardinal features of AMD, including accumulation of lipofuscin in and drusen beneath the retinal pigmented epithelium (RPE), photoreceptor atrophy and choroidal neovascularization (CNV). Complement and IgG deposition in RPE and choroid accompanies senescence in this model, as in human AMD. RPE or choroidal endothelial production of Ccl-2 induced by complement C5a and IgG may mediate choroidal macrophage infiltration into aged wild-type choroids. Wild-type choroidal macrophages degrade C5 and IgG in eye sections of Ccl2(-/-) or Ccr2(-/-) mice. Impaired macrophage recruitment may allow accumulation of C5a and IgG, which induces vascular endothelial growth factor (VEGF) production by RPE, possibly mediating development of CNV. These models implicate macrophage dysfunction in AMD pathogenesis and may be useful as a platform for validating therapies.

Aging↗

PubMed2002

A versatile prodrug approach for liposomal core-loading of water-insoluble camptothecin anticancer drugs.

We describe a versatile prodrug strategy for loading the liposomal lumen with water-insoluble camptothecins. The procedure involves conversion of an active camptothecin analogue to a 20-OR omega-aminoalkanoanic ester prodrug in which R = CO[CH(2)](n)()NH(2) and n = 1-3. The basic amino group of the prodrug serves three roles. First, at pH ranges of 3-5, the amine enhances aqueous solubility. Second, it enhances responsiveness to a transmembrane ammonium sulfate gradient across the liposomal bilayer, thereby facilitating active loading of the agent into the liposomal aqueous core. Third, at a physiological pH of 7 or above (the pH to be encountered following drug release at the tumor site), the nucleophilicity of the amine manifests itself and cyclization to the C-21 carbonyl carbon occurs. This cyclization triggers a rapid and convenient nonenzymatic decomposition process that releases active camptothecin. Accordingly, this novel liposomal approach offers a potential system for tumor-targeting prodrugs of many water-insoluble camptothecins, including the highly lipophilic and clinically attractive analogues SN-38, 9-nitrocamptothecin and DB-67. The rate of formation of the active agent at the tumor site can be controlled through the selection of n (the length of the alkyl spacer group).

Antineoplastic Agents, Phytogenic↗

PubMedDate not supplied

Proteomic analysis of human ventricular cerebrospinal fluid from neurologically normal, elderly subjects using two-dimensional LC-MS/MS.

A two-dimensional liquid chromatography separation scheme coupled to tandem mass spectrometry (2-D LC-MS/MS) was utilized to profile the proteome of human CSF. Ventricular CSF samples acquired post-mortem from 10 cognitively normal elderly subjects (mean +/- SEM Braak stage = 1.7 +/- 0.2) were analyzed to determine their protein composition. Raw CSF samples were subjected to an immunobased processing method to remove highly abundant albumin and immunoglobulin (Ig), allowing better detection of lower-abundance proteins. Samples were subjected to trypsin proteolysis followed by C18 solid-phase extraction. Tryptic CSF peptides were separated using a 2-D LC column, in which both strong cation exchange (SCX) and C18 phases were packed into a single capillary. MS/MS spectra of CSF peptides were searched against a human sub-database of the NBCI nonredundant database using the SEQUEST algorithm. Search results were further filtered using DTAselect, and individual samples were compared to one another using Contrast. Using this method, we were able to unambiguously identify 249 CSF proteins from 10 subjects. Of these proteins, 38% were unique to individual subjects, whereas only 6% were common to all 10 subjects. These results suggest considerable subject-to-subject variability in the CSF proteome.

Aged↗