Degeneration and regeneration of the nervous system

Potent and specific inhibition of mammalian histone deacetylase both in vivo and in vitro by trichostatin A.

Knowing the rate of addition of new granule cells to the adult dentate gyrus is critical to understanding the function of adult neurogenesis. Despite the large number of studies of neurogenesis in the adult dentate gyrus, basic questions about the magnitude of this phenomenon have never been addressed. The S-phase marker bromodeoxyuridine (BrdU) has been extensively used in recent studies of adult neurogenesis, but it has been carefully tested only in the embryonic brain. Here, we show that a high dose of BrdU (300 mg/kg) is a specific, quantitative, and nontoxic marker of dividing cells in the adult rat dentate gyrus, whereas lower doses label only a fraction of the S-phase cells. By using this high dose of BrdU along with a second S-phase marker, [(3)H]thymidine, we found that young adult rats have 9,400 dividing cells proliferating with a cell cycle time of 25 hours, which would generate 9,000 new cells each day, or more than 250,000 per month. Within 5-12 days of BrdU injection, a substantial pool of immature granule neurons, 50% of all BrdU-labeled cells in the dentate gyrus, could be identified with neuron-specific antibodies TuJ1 and TUC-4. This number of new granule neurons generated each month is 6% of the total size of the granule cell population and 30-60% of the size of the afferent and efferent populations (West et al. [1991] Anat Rec 231:482-497; Mulders et al. [1997] J Comp Neurol 385:83-94). The large number of the adult-generated granule cells supports the idea that these new neurons play an important role in hippocampal function.

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Adult neurogenesis produces a large pool of new granule cells in the dentate gyrus.

This article reviews the effects of the short-chain fatty acid butyrate on histone deacetylase (HDAC) activity. Sodium butyrate has multiple effects on cultured mammalian cells that include inhibition of proliferation, induction of differentiation and induction or repression of gene expression. The observation that butyrate treatment of cells results in histone hyperacetylation initiated a flurry of activity that led to the discovery that butyrate inhibits HDAC activity. Butyrate has been an essential agent for determining the role of histone acetylation in chromatin structure and function. Interestingly, inhibition of HDAC activity affects the expression of only 2% of mammalian genes. Promoters of butyrate-responsive genes have butyrate response elements, and the action of butyrate is often mediated through Sp1/Sp3 binding sites (e.g., p21(Waf1/Cip1)). We demonstrated that Sp1 and Sp3 recruit HDAC1 and HDAC2, with the latter being phosphorylated by protein kinase CK2. A model is proposed in which inhibition of Sp1/Sp3-associated HDAC activity leads to histone hyperacetylation and transcriptional activation of the p21(Waf1/Cip1) gene; p21(Waf1/Cip1) inhibits cyclin-dependent kinase 2 activity and thereby arrests cell cycling. Pending the cell background, the nonproliferating cells may enter differentiation or apoptotic pathways. The potential of butyrate and HDAC inhibitors in the prevention and treatment of cancer is presented.

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Inhibition of Histone Deacetylase Activity by Butyrate

Diminished amounts of manganese-containing superoxide dismutase have been found in all the tumors examined to date. Lowered amounts of the copper-zinc-containing superoxide dismutase have been found in many, but not all, tumors. At the same time, tumors have been shown to produce superoxide radicals. It is shown how diminished enzyme activities along with radical production may lead to many of the observed properties of cancer cells. The apparent exploitation of the differences between normal and cancer cell superoxide dismutase activity in the treatment of cancer is discussed.

/pdf/role-of-superoxide-dismutase-in-cancer-a-review-5c4fusvkkr.pdf

Role of Superoxide dismutase in cancer: a review.

The mechanism of mammalian neural differentiation is still obscure; but the availability of mouse neuroblastoma cells in vitro provides an opportunity to study some possible inducers of differentiation and this may help to elucidate the events involved at the molecular level. We have reported1 that X-irradiation of mouse neuroblastoma cells in vitro induces the formation of axons. The differentiated cells seem to undergo maturation: the soma and nucleus increase in size and the cytoplasm becomes granular. Here we report that N6O2 dibutyryl adenosine 3′:5′-cyclic monophosphate (dibutyryl cyclic AMP) induces axon formation in mouse neuroblastoma cells in vitro.

Morphologic differentiation of mouse neuroblastoma cells induced in vitro by dibutyryl adenosine 3':5'-cyclic monophosphate.

Summary

1 An elevation of the intracellular level of cyclic AMP in neuroblastoma cells by prostaglandin E1 by an inhibitor of cyclic AMP phosphodiesterase, or by analogues of cyclic AMP irreversibly induces many differentiated functions which are characteristic of mature neurones These include formation of long neurites, increase in size of soma and nucleus associated with a rise in total RNA and protein contents, increase in activities of specific neural enzymes, loss of malignancy, increase in sensitivity of adenylate cyclase to catecholamines and blockade of cells in G1-stage of the cell cycle



2 Other agents, including serum-free medium, X-irradiation, 6-thioguanine, cytosine arabinoside, methotrexate, 5-bromodeoxyuridine, nerve growth factor, glial extract and hypertonic medium can induce some of the differentiated functions which are induced by high intracellular cyclic AMP



3 Morphological differentiation and differentiated biochemical functions can each be expressed in the absence of the other



4 Many of the responses of normal embryonic nerve cells to cyclic AMP are similar to those of neuroblastoma cells



5 A working hypothesis for the malignancy of nerve cells has been proposed This states that an abnormal regulation of cyclic AMP phosphodiesterase activity which allows the expression of high amounts of this enzyme in neuroblastoma cells, may be one of the early lesions during a malignant transformation of nerve cells



6 A new experimental therapeutic model for the treatment of neuroblastoma is proposed This involves the administration of sodium butyrate followed by the injection of l-dihydroxyphenylalanine (l-dopa) and prostaglandin E1 in the presence of cyclic AMP phosphodiesterase inhibitor



7 Recent studies have elucidated the control mechanisms of some differentiated functions in neuroblastoma cells Cyclic AMP may become an important biological tool to probe the regulation and expression of many other differentiated functions in these cells In addition to neuroblastoma cells, other neuronal culture systems are now available for investigating the problems of differentiation and maturation in nerve cells

Differentiation of neuroblastoma cells in culture.

Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine 3′,5′-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the treatment of neuroblastoma cells in culture causes cell death and “differentiation”; however, it is either innocuous or produces reversible morphological and biochemical alterations in other cell types.

Effect of sodium butyrate on mammalian cells in culture: a review.

PROSTAGLANDIN is known to affect concentrations of cyclic AMP in some cells1. Dibutyryl cyclic AMP induces irreversible differentiation of mouse neuroblastoma cells in vitro2, which raises the question of whether prostaglandin would mimic this effect. I report here that prostaglandins (PG)E1 and PGE2 induce irreversible morphological differentiation of mouse neuroblastoma cells in culture as shown by axon formation, whereas PGF2α does not.

Morphological Differentiation induced by Prostaglandin in Mouse Neuroblastoma Cells in Culture

Mouse neuroblastoma cells in culture have been used as a model for the study of the mechanism by which activities of tyrosine hydroxylase (EC 1.14.3.a) are regulated in sympathetic tissue. The activity of tyrosine hydroxylase in cultured cells drops to barely detectable activities after 1 week and remains low for months in culture in the uncloned cell line of neuroblastoma. Activity in an adrenergic clone isolated from the uncloned line has about 20% of the activity of the fresh grated tumor cell. N6, O2′-dibutyryl adenosine 3′:5′-cyclic monophosphate causes a concentration and time-dependent increase in enzyme activity in both the cloned and uncloned cell lines. Enzyme activity is elevated by other stable analogs of adenosine 3′:5′-cyclic monophosphate, notably the N6-monobutyryl, 8-aminomethyl, and 8-methylthio derivatives of the cyclic nucleotide; by the inhibitor of cyclic nucleotide phosphodiesterase, papaverine; and by sodium butyrate. Changes in cell morphology and tyrosine hydroxylase activity are shown not to be necessarily related.

Regulation of Tyrosine Hydroxylase Activity in Cultured Mouse Neuroblastoma Cells: Elevation Induced by Analogs of Adenosine 3′:5′-Cyclic Monophosphate

Kedar N. Prasad

Papers

Morphologic differentiation of mouse neuroblastoma cells induced in vitro by dibutyryl adenosine 3':5'-cyclic monophosphate.

Differentiation of neuroblastoma cells in culture.

Effect of sodium butyrate on mammalian cells in culture: a review.

Morphological Differentiation induced by Prostaglandin in Mouse Neuroblastoma Cells in Culture

Regulation of Tyrosine Hydroxylase Activity in Cultured Mouse Neuroblastoma Cells: Elevation Induced by Analogs of Adenosine 3′:5′-Cyclic Monophosphate