Biomedical subjects

Jean Strahlendorf

Publications and source records attributed to Jean Strahlendorf.

4 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↗

PubMed2005

Non-lethal active caspase-3 expression in Bergmann glia of postnatal rat cerebellum.

Caspase-3, an apoptotic executor, has been shown in recent years to mediate non-lethal events like cellular proliferation and differentiation, primarily in studies related to non-neural tissue. In central nervous system development, the role of active caspase-3 is still unclear. We provide the first evidence for a potential new role of active (cleaved) caspase-3 in promoting differentiation of Bergmann glia. This study was predicated on the hypothesis that active caspase-3 is important for the differentiation of glia. We addressed the hypothesis through the following specific aims: (1) to establish the expression of active caspase-3 in glia; (2) to determine the developmental phenotype of the active caspase-3-expressing glia; and (3) to confirm that active caspase-3 expression is not mediating an apoptotic event. Through a temporal investigation from postnatal day 8 to 21, we observed that Bergmann glia express active caspase-3 without compromising their survival. Potential apoptotic fate of active caspase-3-positive Bergmann glia were ruled out based on immunohistochemical exclusion of phosphatidylserine exposure (Annexin V), DNA fragmentation (TUNEL), and DNA compaction (TOPRO-3). More than 90% of the active caspase-3-positive cells lacked colabeling for one of the apoptotic markers. Correlative studies using a proliferation marker Ki67 and a differentiation marker brain lipid-binding protein suggest that the expression of active caspase-3 was mostly associated with differentiating rather than proliferating Bergmann glia at all ages. Thus, this study supports the hypothesis that active caspase-3 may be regulating both differentiation of Bergmann glia by allowing the cells to exit the cell cycle and their morphogenesis.

Age Factors↗

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↗

PubMed2003

AMPA-induced dark cell degeneration of cerebellar Purkinje neurons involves activation of caspases and apparent mitochondrial dysfunction.

Cerebellar Purkinje neurons (PNs) are selectively vulnerable to AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepriopionic acid)-induced delayed neurotoxicity known as dark cell degeneration (DCD) that is expressed as cytoplasmic and nuclear condensation, neuron shrinkage, and failure of physiology. The present study was initiated to determine whether AMPA-receptor-induced DCD in PNs is associated with Bax translocation to the mitochondria, cytochrome C release from the mitochondria, changes in mitochondrial potential, and activation of representative initiator and executor caspases that include caspase-9, caspase-3, and caspase-7. AMPA consistently and rapidly hyperpolarized mitochondria as reflected by an increase in MitoTracker Red CMS Ros fluorescence. Increases in Bax immunoreactivity were quantitatively and temporally variable and Bax failed to localize to mitochondria. Additionally, we observed a marked increase in immunoreactivity of cytochrome C although its release from mitochondria was not apparent. Mitochondrial membrane hyperpolarization and increases in cytochrome C immunoreactivity preceded caspase activation. Immunohistochemical analyses revealed the active form of caspases-3 and -9 were markedly and significantly increased in PNs following 30 microM AMPA, and caspase-9 activation preceded caspase-3. Increases in active caspase-7 immunoreactivity were less frequently encountered in PNs. Thus DCD shares some characteristics of apoptotic programmed cell death, but lacks typical mitochondrial pathophysiology associated with classic apoptosis. These findings suggest that AMPA-induced DCD is a form of active PCD that lies on a spectrum between classical apoptosis and passive necrosis.

Animals↗