The mechanism of taurine protection against endoplasmic reticulum stress in an animal stroke model of cerebral artery occlusion and stroke-related conditions in primary neuronal cell culture.

Taurine is an inhibitory neurotransmitter and is one of the most abundant amino acids present in the mammalian nervous system. Taurine has been shown to provide protection against neurological diseases, such as Huntington's disease, Alzheimer's disease, and stroke. Ischemic stroke is one of the leading causes of death and disability in the world. It is generally believed that ischemia-induced brain injury is largely due to excessive release of glutamate resulting in excitotoxicity and cell death. Despite extensive research, there are still no effective interventions for stroke. Recently, we have shown that taurine can provide effective protection against endoplasmic reticulum (ER) stress induced by excitotoxicity or oxidative stress in PC12 cell line or primary neuronal cell cultures. In this study, we employed hypoxia/reoxygenation conditions for primary cortical neuronal cell cultures as an in vitro model of stroke as well as the in vivo model of rat focal middle cerebral artery occlusion (MCAO). Our data showed that when primary neuronal cultures were first subjected to hypoxic conditions (0.3%, 24 h) followed by reoxygenation (21%, 24-48 h), the cell viability was greatly reduced. In the animal model of stroke (MCAO), we found that 2 h ischemia followed by 4 days reperfusion resulted in an infarct of 47.42 ± 9.86% in sections 6 mm from the frontal pole. Using taurine greatly increased cell viability in primary neuronal cell culture and decreased the infarct area of sections at 6 mm to 26.76 ± 6.91% in the MCAO model. Furthermore, levels of the ER stress protein markers GRP78, caspase-12, CHOP, and p-IRE-1 which were markedly increased in both the in vitro and in vivo models significantly declined after taurine administration, suggesting that taurine may exert neuroprotection functions in both models. Moreover, taurine could downregulate the ratio of cleaved ATF6 and full-length ATF6 in both models. In the animal model of stroke, taurine induced an upregulation of the Bcl-2/Bax ratio and downregulation of caspase-3 protein activity indicating that it attenuates apoptosis in the core of the ischemic infarct. Our results show not only taurine elicits neuroprotection through the activation of the ATF6 and the IRE1 pathways, but also it can reduce apoptosis in these models.

In vitro differentiation of GABAergic cells from bone marrow stromal cells using potassium chloride as inducer.

Bone marrow stromal cells (BMSCs) are multipotent and can be induced to differentiate into different lineages including osteogenic, chondrogenic, myogenic and neuronal phenotypes. BMSCs were reported to be a suitable option for regenerative medical research. In this study, BMSCs were induced into GABAergic phenotypes using beta-mercaptoethanol (betaME) and retinoic acid (RA) as preinducers followed by potassium chloride as inducer, and were evaluated by fibronectin and Oct-4. The percentages of cells immunoreactive for nestin, neurofilaments (NF 68, NF 160, and NF 200), GABA and GABA synthesizing and packaging enzymes (GAD1, GAD2, VGAT) were used for evaluating GABAergic differentiation. RT-PCR was used for confirming the expression of these enzymes. The differentiated cells were loaded and unloaded with FM1-43 in order to assess the functionality of the cells. At the preinduction stage, the cells downregulated fibronectin and Oct-4, and expressed neuronal markers. At the induction stage, the preinduced cells transdifferentiated into GABAergic cells, as confirmed by immunohistochemistry and RT-PCR. The GABAergic cells were stained and destained with FM1-43. Therefore, the two-stage induction protocol resulted in transdifferentiation of BMSCs into GABAergic cells with synaptic release upon stimulation.