Biomedical subjects

Karen Bulloch

Publications and source records attributed to Karen Bulloch.

4 recordsLinked to original sources

PubMed2007

Microglia derived from aging mice exhibit an altered inflammatory profile.

Microglia play a critical role in neurodegenerative diseases and in the brain aging process. Yet, little is known about the functional dynamics of microglia during aging. Thus, using young and aging transgenic mice expressing enhanced-green fluorescent protein (EGFP) under the promoter of the c-fms gene for macrophage-colony stimulating factor receptor, we evaluated in vivo-induced inflammatory responses of EGFP-expressing microglia sorted by flow cytometry. Aging microglia were characterized by the presence of lipofuscin granules, decreased processes complexity, altered granularity, and increased mRNA expression of both pro-inflammatory (TNFalpha, IL-1beta, IL-6) and anti-inflammatory (IL-10, TGFbeta1) cytokines. Following lipopolysaccharide (LPS) challenge (1 mg/kg, 3 h), aging microglia exhibit increased basal expression of TNFalpha, IL-1beta, IL-6, and IL-10. Yet, the fold-over-basal LPS response remained constant across age, implying that the inflammatory machinery in aging microglia is functional and adjusted to the basal state. Gender differences were not overall observed across the treatments (age, LPS). The low but sustained production of pro-inflammatory cytokines by aging microglia may have a profound impact in the brain aging process.

Aging↗

PubMed2005

Dehydroepiandrosterone (DHEA) metabolism in the brain: identification by liquid chromatography/mass spectrometry of the delta-4-isomer of DHEA and related steroids formed from androstenedione by mouse BV2 microglia.

Studies to elucidate the role of dehydroepiandrosterone (DHEA) metabolism in neuroprotection have compared its relative 7-hydroxylation against estrogen formation by way of 4-androstenedione (AD) in various rodent brain cell lines. In all cases, the 7alpha- and 7beta-hydroxy epimers of DHEA were found to be the dominant products with one notable exception. BV2 mouse microglia were virtually unable to hydroxylate DHEA at C-7 and converted AD to a major unknown metabolite not observed with mouse BHc hippocampal cells. In this paper, we describe the identification of this compound based on its physical properties and analysis by TLC and HPLC. Its identity as 3beta-hydroxy-4-androstene-17-one, the Delta(4)-isomer of DHEA, was confirmed by mass spectrometry (LC/MS), as well as by reverse isotope dilution analysis involving co-crystallization with the synthetic steroid. Possible mechanisms for the formation of this isomer of DHEA by BV2 microglia are proposed, together with that of other C-19 steroids detected which include testosterone (T), 5alpha-dihydrotestosterone and 5alpha-androstanedione.

Adjuvants, Immunologic↗

PubMed2005

Metabolism of dehydroepiandrosterone by rodent brain cell lines: relationship between 7-hydroxylation and aromatization.

The rate of aromatization of 4-androstenedione (AD) and 7-hydroxylation of dehydroepiandrosterone (DHEA) by different neuronal cell lines from fetal rat and mouse brain was compared to that of embryonic rat hippocampal cells in primary culture. The (3)H-labeled steroids were incubated with the cells and the metabolites extracted and separated by thin layer chromatography (TLC), as well as analyzed by high-performance liquid chromatography (HPLC) for further identification. All cell types produced estrone (E(1)) and estradiol (E(2)) from [(3)H]AD but the rate of aromatization was lowest with the rat hippocampal cells in primary culture. With [(3)H]DHEA, BHc.2 mouse hippocampal cells and E(t)C.1 neurons behaved like the mixed cells from rat hippocampus, forming 7-hydroxy DHEA as the almost exclusive product. In contrast, mouse brain BV2 microglia were virtually unable to hydroxylate DHEA at C-7 and yielded estrogen and more testosterone (T) than other cell types tested. These experiments highlight the pivotal role of 3beta-hydroxysteroid dehydrogenase/ketoisomerase in the control of AD formation for its subsequent aromatization to estrogen. It raises the possibility that differences in metabolism of DHEA by certain brain cells could account for differences in their immunomodulatory and neuroprotective functions. Some could exert their effects by converting DHEA to its 7-hydroxylated form while others, like BV2 microglia, by converting DHEA primarily to other C-19 steroids and to estrogen by way of AD.

17-Hydroxysteroid Dehydrogenases↗

PubMed2003

Type II glucocorticoid receptor immunoreactivity in the mossy cells of the rat and the mouse hippocampus.

Hippocampal principal neurons, granule and pyramidal cells, are known to express type II glucocorticoid receptors (GR) and it is believed that glucocorticoids (GC) mediate at least some of their effects through GR. Under conditions of severe stress and trauma, these principal cells are vulnerable to damage and this mechanism may be exacerbated by GR. The mossy cell, an excitatory dentate gyrus neuron, is also damaged following trauma, with over 50% reported loss in rats after kainate-induced seizures. However, it has not been determined if GC play any role in protecting or exacerbating damage to this important hippocampal cell type. In the present study, we have undertaken an evaluation of the presence of GR in mossy cells of the rat and mouse utilizing an immunocytochemical double-labeling technique. To identify mossy cells in the rat, we utilized an antibody to the glutamate receptor subunit 2/3 (GluR2/3). In addition to GluR2/3 antibodies, in the mouse, an antibody to the calcium-binding protein, calretinin (CR), to identify mossy cells was also employed. Our results show that GR immunoreactivity (IR) was colocalized with GluR2/3-IR in approximately 90% of the rat and the mouse mossy cells. In addition, GR-IR was identified in the CR-IR mossy cells in the mouse hippocampus, whereas the CR-IR interneurons of rat and mouse were negative for GR-IR. The presence of GR on mossy cells may indicate the ability of GC to mediate cellular activity of these cells.

Animals↗