Taurine is a free sulfur amino acid that is not

Taurine is a free sulfur amino eletriptan manufacturer that is not incorporated in proteins. It is synthesized from methionine and cysteine by the rate-limiting enzyme cysteinesulfinic acid decarboxylase (CSD) that is found in the liver, the kidney and the brain, where it is localized in glial cells (Ripps & Shen, 2012). In the liver, CSD activity is increased by protein-rich diet (Bella et al., 1999) whereas in the brain, glutamate increases CSD activity (Wu et al., 1998). Taurine is also found in high concentrations in numerous diets such as meat and seafood (Huxtable, 1992) and crosses the blood brain barrier using a specific beta amino acid transporter TAUT (TAUrine Transporter (Benrabh et al., 1995)). Taurine is 3–4 times more abundant in the developing than in the mature brain (Miller et al., 2000) and its concentration decreases with aging (Banay-Schwartz et al., 1989), suggesting that taurine plays a role during brain development. Consistent with this, dietary taurine deficiency during gestation leads to impaired development of the cerebellum and the visual cortex of newborn cats (Sturman et al., 1985). Intriguingly, taurine also seems to play a role in the adult and aging brain: Chronic administration of taurine in aged mice (El Idrissi, 2008; Neuwirth et al., 2013) or in a mouse model of Alzheimer\'s disease (Kim et al., 2014) increases hippocampus-dependent learning and retention and reduces anxiety and depression (Chen et al., 2004). The mechanisms by which taurine increases learning performances are unclear, but recent work showed that taurine increases the proliferation of adult neural stem/progenitor cells from the subventricular zone in vitro (Ramos-Mandujano et al., 2014; Hernandez-Benitez et al., 2012), suggesting that the effect of taurine may be mediated by an increase in adult neurogenesis. However, these studies did not address whether taurine increased net hippocampal neurogenesis in vivo. Here, we directly assessed the effect of taurine on the age-related decline of adult hippocampal neurogenesis. To this aim, we tested the effect of taurine injections on 10-month-old mice, an age at which adult neurogenesis has reached its minimal activity (Kuhn et al., 1996; Gil-Mohapel et al., 2013). Using the incorporation of the proliferation marker 5-bromo-2-deoxyuridine (BrdU), combined with the genetic and immunohistochemical identification of adult hippocampal stem cells, intermediate progenitors, newborn mature and immature neurons, we examined the effect of taurine on several steps of the formation of new neurons in the aging hippocampus.
Methods
Results
Discussion In the present study, we tested the effect of chronic administration of taurine on hippocampal neurogenesis in aging mice. We found that taurine increased cell proliferation in the DG. More specifically, RGL stem cells showed enhanced proliferation that resulted in an increase in the number of RGL stem cells, Tbr2+ intermediate progenitors and DCX+ immature neurons. Moreover, taurine increased the survival of new neurons, resulting in a net increase in adult neurogenesis. Taurine also a reduced microglia number, morphological parameters associated with activation, MHC-II expression and increased stem/progenitor cell proliferation in vitro. Together, these results indicate that, in the aging brain, taurine increases the production of new neurons by stimulating several steps of adult neurogenesis and plays a role in microglia function. Taurine is known to be involved in variety of cellular processes, including calcium homeostasis (El Idrissi, 2008; Wu et al., 2005; Foos & Wu, 2002), protection from glutamate excitotoxicity and apoptosis (Foos & Wu, 2002; Leon et al., 2009), inflammation (Kim & Cha, 2014), oxidative stress (Menzie et al., 2013), and epilepsy (El Idrissi et al., 2003), all of which contribute to the regulation of adult neurogenesis. However, since there is currently no known taurine receptor, its role as an osmolyte is believed to participate to these processes. Our results suggest that taurine can regulate adult neurogenesis both through an indirect effect on microglia and a direct effect on stem/progenitor cells.