Biomedical subjects

Janet Dertien

Publications and source records attributed to Janet Dertien.

3 recordsLinked to original sources

PubMed2006

Bergmann glia utilize active caspase-3 for differentiation.

Recently, functions associated with caspase have been modified from their well-established role in apoptosis. Although caspases are still regarded as mediators of apoptosis, some of the pro-apoptotic caspases, namely caspase-8, -14 and -3 also regulate differentiation in certain cell types, namely myelomonocytic cells, osteoblasts, skeletal muscle cells, keratinocytes, and T lymphocytes. In the central nervous system, non-apoptotic active caspase-3 expression has been located in proliferating and differentiating neuronal cells of the ventricular zone and external granular layer of the developing cerebellar cortex. We previously demonstrated that active caspase-3 expression was not limited to neuronal cells but also was located in the Bergmann glia of the postnatal cerebellum. In that study, active caspase-3 immunolabeling did not markedly colocalize with Ki67, a proliferation marker, but was present in differentiating Bergmann glia that expressed brain lipid binding protein (BLBP) and thus, by its localization, suggested a role in the differentiation of Bergmann glia. The current study addresses the function of caspase-3 in Bergmann glia development by utilizing a Bergmann glial culture preparation. Inhibition of caspase-3 activity by the peptide inhibitor, DMQD-FMK, increased the number of proliferating precursor glial cells and decreased the number of differentiating Bergmann glia, without significantly altering the non-glial active caspase-3 negative population. The transformation in the developmental state of Bergmann glia occurring after suppression of caspase-3 activity strongly suggests an involvement of this enzyme in promoting differentiation of Bergmann glia.

Animals↗

PubMed2004

Active caspase-3 expression during postnatal development of rat cerebellum is not systematically or consistently associated with apoptosis.

Development is a dynamic process that includes an intricate balance between an increase in cell mass and an elimination of excess or defective cells. Although caspases have been intimately linked to apoptotic events, there are a few reports suggesting that these cysteine proteases can influence the differentiation and proliferation of cells. Specifically, the active form of caspase-3, which has been classified as an executor of apoptosis, recently has been implicated in a nonapoptotic role in the regulation of the cell cycle, cell proliferation, and cell differentiation. This study investigated the nonapoptotic function and phenotypic expression of active caspase-3-positive cells in the external granule cell layer (EGL) of the postnatal rat cerebellum by using biochemical and immunohistochemical analyses, respectively. Evidence that negates an apoptotic function for the caspase-3-positive EGL cells includes a failure to exhibit chromatin condensation (assessed with TOPRO), phosphatidyl serine externalization (Annexin V labeling), or DNA fragmentation (TUNEL labeling). Proliferative (Ki67-positive) and differentiated (TUJ1-positive) cells within the EGL exhibited a cytosolic expression of caspase-3, whereas terminally differentiated granule cells (NeuN-positive) in the internal granular layer and the migrating granule cells did not express active caspase-3. Thus, this study supports a nonapoptotic role for active caspase-3 in cells residing in the EGL and suggests a possible involvement in EGL proliferation and differentiation.

Aging↗

PubMed2002

Ethanol-induced modulation of inducible nitric-oxide synthase activity in human A172 astrocytoma cells.

BACKGROUND: Glial cells are critical in the functioning of the central nervous system (CNS), including responsiveness to injury and immunocompetence. The immune and inflammatory response involves the inducible form of nitric-oxide synthase (iNOS), and subsequent nitric oxide (NO) production. Previously, we have demonstrated that ethanol inhibits cytokine-induced iNOS expression and activity in rat glial cells. Evidence of ethanol-induced effects on iNOS in human glial cells is nonexistent. Herein, the conditions necessary for significant iNOS induction in human A172 astrocytoma cells have been characterized, and subsequently, the effects of ethanol on iNOS expression have been investigated. METHODS: A172 cells were analyzed immunohistochemically for the astrocyte markers, glial fibrillary acidic protein (GFAP) and S-100beta. The ability of A172 cells to express iNOS was assessed by stimulating cells with interferon-gamma (IFNgamma), tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), bacterial lipopolysaccharide (LPS), L-arginine, and tetrahydrobiopterin (BH4) in various combinations. Following stimulation, iNOS induction was monitored via measurement of nitrite production and in vitro iNOS enzyme activity. Time-course (6-24 hr) studies assessed the effects of ethanol (50-200 mM) on iNOS induction. RESULTS: Immunohistochemistry analysis confirmed that A172 cells were phenotypically, astrocytic. Induction of nitrite production by a cytomix [IFNgamma (100 ng/ml) + TNFalpha (30 ng/ml) + IL-1beta (5 ng/ml)] was differentially enhanced by exposure to supplemental factors including LPS, L-arginine, and BH4. Nitrite production was greatest over the initial 24 hr of stimulation with iNOS enzyme activity peaking at 12 hr. Acute (6-24 hr) exposure of activated cells to 50 mM ethanol enhanced iNOS activity recovered from the cytosol, whereas 200 mM ethanol decreased it. Ethanol had no direct effect on the catalytic activity of the enzyme. CONCLUSIONS: The present study is the first published report of ethanol-induced modulation of iNOS expression in human glial cells. The data suggest that ethanol is influencing iNOS enzyme levels most profoundly. Altered astrocyte function may be a point of ethanol-induced perturbation in CNS immune function. These findings should lend insight into the role of ethanol on human CNS immunity and brain injury.

Astrocytoma↗