Cell Volume Regulation in Taurine Deficient Cultured Astrocytes

Morán, Julio; Maar, Thomas E.; Pasantes‐Morales, Herminia

doi:10.1007/978-1-4899-1471-2_37

Cited by 19 publications

(12 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Taurine is widely regarded as an important osmoregulatory molecule in the brain and in other tissues because it is one of the most abundant organic osmolytes and effectively permeates a putative VRAC-like pathway [23], [22], [28], [43], [70]. Consistent with its osmoregulatory role, taurine release in cultured astrocytes, hippocampal slices, and in vivo microdialysis experiments has been found to be potently upregulated under hypoosmotic conditions (reductions in [NaCl] e ), but is insensitive to isoosmotic changes in [NaCl] e [23], [41], [66].…”

Section: Discussionmentioning

confidence: 99%

Two Distinct Modes of Hypoosmotic Medium-Induced Release of Excitatory Amino Acids and Taurine in the Rat Brain In Vivo

et al. 2008

View full text Add to dashboard Cite

A variety of physiological and pathological factors induce cellular swelling in the brain. Changes in cell volume activate several types of ion channels, which mediate the release of inorganic and organic osmolytes and allow for compensatory cell volume decrease. Volume-regulated anion channels (VRAC) are thought to be responsible for the release of some of organic osmolytes, including the excitatory neurotransmitters glutamate and aspartate. In the present study, we compared the in vivo properties of the swelling-activated release of glutamate, aspartate, and another major brain osmolyte taurine. Cell swelling was induced by perfusion of hypoosmotic (low [NaCl]) medium via a microdialysis probe placed in the rat cortex. The hypoosmotic medium produced several-fold increases in the extracellular levels of glutamate, aspartate and taurine. However, the release of the excitatory amino acids differed from the release of taurine in several respects including: (i) kinetic properties, (ii) sensitivity to isoosmotic changes in [NaCl], and (iii) sensitivity to hydrogen peroxide, which is known to modulate VRAC. Consistent with the involvement of VRAC, hypoosmotic medium-induced release of the excitatory amino acids was inhibited by the anion channel blocker DNDS, but not by the glutamate transporter inhibitor TBOA or Cd2+, which inhibits exocytosis. In order to elucidate the mechanisms contributing to taurine release, we studied its release properties in cultured astrocytes and cortical synaptosomes. Similarities between the results obtained in vivo and in synaptosomes suggest that the swelling-activated release of taurine in vivo may be of neuronal origin. Taken together, our findings indicate that different transport mechanisms and/or distinct cellular sources mediate hypoosmotic medium-induced release of the excitatory amino acids and taurine in vivo.

show abstract

Section: Discussionmentioning

confidence: 99%

Two Distinct Modes of Hypoosmotic Medium-Induced Release of Excitatory Amino Acids and Taurine in the Rat Brain In Vivo

et al. 2008

View full text Add to dashboard Cite

show abstract

“…As expected, the blockade of GlyRs led to a depolarization mediated by the suppression of a resting chloride conductance, and the E REV for this effect was equal to that of IPSPs and negative to the threshold for AP generation. Moreover, selective depletion of tissue taurine by prolonged incubation in the presence of the taurine transport inhibitor GES (Morán et al, 1994) abolished the strychninemediated excitation and caused a significant increase in the basal firing rate of hypotonic SON neurons when compared with nondepleted preparations (Fig. 2).…”

Section: Taurine Mediates a Hyperpolarizing Glyr Tone In Son Neuronsmentioning

confidence: 90%

Taurine Release by Astrocytes Modulates Osmosensitive Glycine Receptor Tone and Excitability in the Adult Supraoptic Nucleus

2012

View full text Add to dashboard Cite

Cells can release the free amino acid taurine through volume-regulated anion channels (VRACs), and it has been hypothesized that taurine released from glial cells is capable of inhibiting action potential (AP) firing by activating neuronal glycine receptors (GlyRs) (Hussy et al., 1997). Although an inhibitory GlyR tone is widely observed in the brain, it remains unknown whether this specifically reflects gliotransmission because most neurons also express VRACs and other endogenous molecules can activate GlyRs. We found that VRACs are absent in neurons of the rat supraoptic nucleus (SON), suggesting that glial cells are the exclusive source of taurine in this nucleus. Application of strychnine to rat hypothalamic explants caused a depolarization of SON neurons associated with a decrease of chloride conductance and could excite these cells in the absence of fast synaptic transmission. This inhibitory GlyR tone was eliminated by pharmacological blockade of VRACs, by cellular taurine depletion, by metabolic inactivation of glia with fluorocitrate, and after retraction of astrocytic processes that intercalate neuronal somata and dendrites. Finally, GlyR tone varied inversely with extracellular fluid tonicity to mediate the osmotic control of AP firing by SON neurons. These findings establish taurine as a physiological gliotransmitter and show that gliotransmission is a spatially constrained process that can be modulated by the morphological rearrangement of astrocytes.

show abstract

“…Many organic anions like taurine are released through the VSOACs, in order to achieve a reduction in intracellular osmolytes. Taurine-deficient astrocytes have a higher volume than normal astrocytes (Moran et al, 1994); thus, the role of anions other than chloride should not be underestimated. Astrocytes appear to swell readily if their environment is disturbed (Kimelberg, 1995); therefore, such a regulatory volume decrease should play a large role under normal physiological conditions.…”

Section: Volume Controlmentioning

confidence: 99%

Chloride/anion channels in glial cell membranes

Walz

2002

Glia

View full text Add to dashboard Cite

At least seven different chloride/anion currents have now been identified in astrocytes, oligodendrocytes/Schwann cells, and microglia. Only for two of these currents is the corresponding gene known. One of these genes is not encoding for a chloride channel, but for a class of mitochondria-like pores also found in cell membranes. Astrocytes and oligodendrocytes differ in their resting properties: astrocytes accumulate chloride but do not have a significant permeability. Oligodendrocytes have a close to passive distribution and a significant permeability. Under certain circumstances, astrocytes can express a resting chloride conductance. Reactive and neoplastic astrocytes as well as astrocytes with an altered shape exhibit a resting conductance. The function of these channels certainly involves volume regulation. Other possible functions are potassium homeostasis, migration, proliferation (in microglia), and involvement in spreading depression waves. Of greatest interest are two phenomena discovered in situ: The ClC-2 channel is only found in astrocytic endfeet near blood capillaries adjacent to neuronal GABA A receptors. In the supraoptic nucleus of the hypothalamus, there is an osmosensitive astrocytic taurine release. This released taurine interacts with glycine receptors in neighboring neurons, causing inhibition. It is assumed that with the future availability of more in situ, rather than in vitro, studies, an increased number of such complex interactions between glial cells, neurons, and blood vessels will be discovered.

show abstract

Cell Volume Regulation in Taurine Deficient Cultured Astrocytes

Cited by 19 publications

References 17 publications

Two Distinct Modes of Hypoosmotic Medium-Induced Release of Excitatory Amino Acids and Taurine in the Rat Brain In Vivo

Two Distinct Modes of Hypoosmotic Medium-Induced Release of Excitatory Amino Acids and Taurine in the Rat Brain In Vivo

Taurine Release by Astrocytes Modulates Osmosensitive Glycine Receptor Tone and Excitability in the Adult Supraoptic Nucleus

Chloride/anion channels in glial cell membranes

Contact Info

Product

Resources

About