Biomedical subjects

Lewis M Brown

Publications and source records attributed to Lewis M Brown.

4 recordsLinked to original sources

PubMed2026

Dysregulated adult hippocampal neurogenesis in major depressive disorder.

Major depressive disorder (MDD) is associated with reduced hippocampal volume, altered connectivity and negative memory bias, suggesting disrupted hippocampal plasticity. Dysregulated adult hippocampal neurogenesis is a potential contributor, but its relevance in humans and role in MDD remain unclear. Here we investigated the molecular basis of hippocampal dysfunction in nonmedicated individuals with MDD by integrating analyses of neurogenic trajectories, cell-type- and subfield-specific gene expression, chromatin accessibility and protein expression. We identify a neurogenic lineage in the adult human hippocampal subgranular zone and provide evidence for a stalled neurogenic process in MDD, associated with transcriptional regulation, stress-related reprogramming and interferon signaling across developmental stages. Excitatory and inhibitory neurons show dysregulation of transcription factor networks affecting cell states. Cellular stress, excitatory-inhibitory imbalance, impaired synaptic plasticity, reduced metabolic capacity and immune activation, underlie impaired neurogenesis and reduced hippocampus circuit plasticity. Findings indicate genetic and epigenetic regulation of gene expression in MDD, and overlapping pathogenetic mechanisms with autoimmune, neurodevelopmental and neurodegenerative diseases. This work provides a new understanding of the pathogenesis of hippocampus-dependent cognitive symptoms in MDD and suggests potential therapeutic targets.

Journal Article↗

PubMed2007

Expression of the calcium-binding protein S100A4 is markedly up-regulated by osmotic stress and is involved in the renal osmoadaptive response.

Proteomic analysis of Inner Medullary Collecting Duct (IMCD3) cells adapted to increasing levels of tonicity (300, 600, and 900 mosmol/kg H(2)O) by two-dimensional difference gel electrophoresis and mass spectrometry revealed several proteins as yet unknown to be up-regulated in response to hypertonic stress. Of these proteins, one of the most robustly up-regulated (22-fold) was S100A4. The identity of the protein was verified by high pressure liquid chromatography-mass spectrometry. Western blot analysis confirmed increased expression with increased tonicity, both acute and chronic. S100A4 protein expression was further confirmed by immunocytochemical analysis. Cells grown in isotonic conditions showed complete absence of immunostaining, whereas chronically adapted IMCD3 cells had uniform cytoplasmic localization. The protein is also regulated in vivo as in mouse kidney tissues S100A4 expression was many -fold greater in the papilla as compared with the cortex and increased further in the papilla upon 36 h of thirsting. Increased expression of S100A4 was also observed in the medulla and papilla, but not the cortex of a human kidney. Data from Affymetrix gene chip analysis and quantitative PCR also revealed increased S100A4 message in IMCD3 cells adapted to hypertonicity. The initial expression of message increased at 8-10 h following exposure to acute sublethal hypertonic stress (550 mosmol/kg H(2)O). Protein and message half-life in IMCD3 cells were 85.5 and 6.8 h, respectively. Increasing medium tonicity with NaCl, sucrose, mannitol, and choline chloride stimulated S100A4 expression, whereas urea did not. Silencing of S100A4 expression using a stable siRNA vector (pSM2; Open Biosystems) resulted in a 48-h delay in adaptation of IMCD3 cells under sublethal osmotic stress, suggesting S100A4 is involved in the osmoadaptive response. In summary, we describe the heretofore unrecognized up-regulation of a small calcium-binding protein, both in vitro and in vivo, whose absence profoundly delays osmoadaptation and slows cellular growth under hypertonic conditions.

Adaptation, Physiological↗

PubMed2006

Quantitative and qualitative differences in protein expression between papillary thyroid carcinoma and normal thyroid tissue.

In order to better understand basic mechanisms of tumor development and identify potential new biomarkers, we have performed difference gel electrophoresis (DIGE) and peptide mass fingerprinting on pooled protein extracts from patients with papillary thyroid carcinoma (PTC) compared with matched normal thyroid tissue. Image analysis of DIGE gels comparing PTC and matched normal thyroid tissue protein indicated that 25% of the protein spots were differentially expressed at a 2.5-fold cutoff and 35% at two-fold. Comparison between two different pools of protein from normal thyroid tissues revealed differential protein expression of only 4% at 2.5-fold and 6% at two-fold cutoff. One hundred ninety-two protein spots were identified by MALDI-TOFMS, representing 90 distinct proteins. Excluding albumin, globins and thyroglobulin, imaging software determined 31 proteins to be differentially expressed at the two-fold (or greater) level. Individual gel comparisons (PTC vs. matched normal) from five patients established that 15/31 (48%) of these proteins exhibited statistically significant differential expression. Previously identified molecular markers in this group of proteins include cathepsin B, cytokeratin 19, and galectin-3. Novel differentially expressed proteins include S100A6, moesin, HSP70 (BiP), peroxiredoxin 2, protein phosphatase 2, selenium binding protein 1, vitamin D binding protein, and proteins involved in mitochondrial function. The use of two-dimensional gel electrophoresis (2DGE) revealed a significantly altered protein mass and/or pI in 10%-15% of proteins, suggesting alternatively spliced forms and other posttranslational modification of proteins revealed by this approach. We confirmed S100A6 as a potentially useful biomarker using immunohistochemical analysis (85% sensitivity and 69% specificity for distinguishing benign from malignant thyroid neoplasms). In summary, proteomic analysis of PTC using DIGE and mass spectrometry has confirmed several known biomarkers, uncovered novel potential biomarkers, and provided insights into global pathophysiologic changes in PTC. Many of the differences observed would not have been detected by genomic or other proteomic approaches.

Amino Acid Sequence↗

PubMed2005

Estrogen regulation of the rat anterior pituitary gland proteome.

Estrogen is known to affect the regulation of all six of the established anterior pituitary gland (AP) hormones, but little is known of the specifics of its regulation of the AP hormones, their isoforms, and nonhormonal AP proteins. We used difference gel electrophoresis in conjunction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and peptide mass fingerprinting to quantify the effects of estrogen on the AP-soluble protein fraction in rats. Two-month-old rats were ovariectomized and used at 6 months of age. They were injected subcutaneously with sesame oil vehicle or 50 mug estradiol valerate in vehicle and studied 48 hrs later, approximately 3 hrs before the time of the anticipated onset of the estrogen-induced surges of gonadotropins in blood. The APs were pooled, and the soluble protein fraction was examined in replicate analyses. After DeCyder software analysis, we identified 26 protein spots that had a 1.5-fold or greater average increase in the experimental group relative to the controls. Nineteen showed a 1.5-fold or greater decrease. Estrogen increased levels of the more acidic isoforms of growth hormone and prolactin and of proteins involved in protein synthesis, folding, and secretion (e.g., eukaryotic translation elongation factor 2, ERp57, ERp29, Hsc70-ps1, calreticulin, coatomer delta subunit, and secretogranin II) and of some metabolic enzymes (e.g., arginosuccinate synthetase, enolase 1, creatine kinase B, phosphoglycerate mutase, malate dehydrogenase, pyruvate kinase, and aldolase A). The majority of the downregulated proteins were involved in RNA or DNA interactions (e.g., five heterogeneous nuclear ribonucleoproteins, DEAD-box proteins 17 and 48, ssDNA binding protein PUR-alpha, PTB-associated splicing factor, and Pigpen protein), but isovaleryl coenzyme A dehydrogenase, mitochondrial aldehyde dehydrogenase, stathmin 1, vinculin, radixin, and secretogranin III were also reduced. Our results indicate that estrogen acts in vivo within 48 hrs to modulate levels of a significant number of AP proteins.

Animals↗