Neuroprotective Functions Through Inhibition of ER Stress by Taurine or Taurine Combination Treatments in a Rat Stroke Model.

Taurine, as a free amino acid, is found at high levels in many tissues including brain, heart and skeletal muscle and is known to demonstrate neuroprotective effects in a range of disease conditions including stroke and neurodegenerative disease. Using in vitro culture systems we have demonstrated that taurine can elicit protection against endoplasmic reticulum stress (ER stress) from glutamate excitotoxicity or from excessive reactive oxygen species in PC12 cells or rat neuronal cultures. In our current investigation we hypothesized that taurine treatment after stroke in the rat middle cerebral artery occlusion (MCAO) model would render protection against ER stress processes as reflected in decreased levels of expression of ER stress pathway components. We demonstrated that taurine elicited high level protection and inhibited both ATF-6 and IRE-1 ER stress pathway components. As ischemic stroke has a complex pathology it is likely that certain combination treatment approaches targeting multiple disease mechanisms may have excellent potential for efficacy. We have previously employed the partial NMDA antagonist DETC-MeSO to render protection against in vivo ischemic stroke using a rat cerebral ischemia model. Here we tested administration of subcutaneous administration of 0.56 mg/kg DETC-MeSO or 40 mg/kg of taurine separately or as combined treatment after a 120 min cerebral ischemia in the rat MCAO model. Neither drug alone demonstrated protection at the low doses employed. Remarkably however the combination of low dose DETC-MeSO plus low dose taurine conferred a diminished infarct size and an enhanced Neuroscore (reflecting decreased neurological deficit). Analysis of ER stress markers pPERK, peIF-2-alpha and cleaved ATF-6 all showed decreased expression demonstrating that all 3 ER stress pathways were inhibited concurrent with a synergistic protective effect by the post-stroke administration of this DETC-MeSO-taurine combination treatment.

Analysis of Neuroprotection by Taurine and Taurine Combinations in Primary Neuronal Cultures and in Neuronal Cell Lines Exposed to Glutamate Excitotoxicity and to Hypoxia/Re-oxygenation.

Ischemic stroke is one of the greatest contributors to death and long term disability in developed countries. Ischemia induced brain injury arises due to excessive release of glutamate and involves cell death due to apoptosis and endoplasmic reticulum (ER) stress responses. Despite major research efforts there are currently no effective treatments for stroke. Taurine, a free amino acid found in high concentrations in many invertebrate and vertebrate systems can provide protection against a range of neurological disorders. Here we demonstrate that taurine can combat ER stress responses induced by glutamate or by hypoxia/re-oxygenation in neuronal cell lines and primary neuronal cultures. Taurine decreased expression of ER stress markers GRP78, CHOP, Bim and caspase 12 in primary neuronal cultures exposed to hypoxia/re-oxygenation. In analyzing individual ER stress pathways we demonstrated that taurine treatment can result in reduced levels of cleaved ATF6 and decreased p-IRE1 levels. We hypothesized that because of the complex nature of stroke a combination therapy approach may be optimal. For this reason we proceeded to test combination therapies using taurine plus low dose administration of an additional drug: either granulocyte colony stimulating factor (G-CSF) or sulindac a non-steroidal anti-inflammatory drug with potent protective functions through signaling via ischemic preconditioning pathways. When primary neurons were pretreated with 25 mM taurine and 25 ng/mL G-CSF for I hour and then exposed to high levels of glutamate, the taurine/G-CSF combination increased the protective effect against glutamate toxicity to 88% cell survival compared to 75% cell survival from an individual treatment with taurine or G-CSF alone. Pre-exposure of PC12 cells to 5 mM taurine or 25 µM sulindac did not protect the cells from hypoxia/re-oxygenation stress whereas at these concentrations the combination of taurine plus sulindac provided significant protection. In summary we have demonstrated the protective effect of taurine in primary neuronal cultures against hypoxia with re-oxygenation through inhibition of ATF6 or p-IRE-1 pathway but not the PERK pathway of ER stress. Furthermore the combinations of taurine plus an additional drug (either G-CSF or sulindac) can show enhanced potency for protecting PC 12 cells from glutamate toxicity or hypoxia/re-oxygenation through inhibition of ER stress responses.

Static Magnetic Field Stimulation Enhances Oligodendrocyte Differentiation and Secretion of Neurotrophic Factors.

The cellular-level effects of low/high frequency oscillating magnetic field on excitable cells such as neurons are well established. In contrast, the effects of a homogeneous, static magnetic field (SMF) on Central Nervous System (CNS) glial cells are less investigated. Here, we have developed an in vitro SMF stimulation set-up to investigate the genomic effects of SMF exposure on oligodendrocyte differentiation and neurotrophic factors secretion. Human oligodendrocytes precursor cells (OPCs) were stimulated with moderate intensity SMF (0.3 T) for a period of two weeks (two hours/day). The differential gene expression of cell activity marker (c-fos), early OPC (Olig1, Olig2. Sox10), and mature oligodendrocyte markers (CNP, MBP) were quantified. The enhanced myelination capacity of the SMF stimulated oligodendrocytes was validated in a dorsal root ganglion microfluidics chamber platform. Additionally, the effects of SMF on the gene expression and secretion of neurotrophic factors- BDNF and NT3 was quantified. We also report that SMF stimulation increases the intracellular calcium influx in OPCs as well as the gene expression of L-type channel subunits-CaV1.2 and CaV1.3. Our findings emphasize the ability of glial cells such as OPCs to positively respond to moderate intensity SMF stimulation by exhibiting enhanced differentiation, functionality as well as neurotrophic factor release.

A review of induced pluripotent stem cell, direct conversion by trans-differentiation, direct reprogramming and oligodendrocyte differentiation.

Rapid progress in the field of stem cell therapy and cellular reprogramming provides convincing evidence of its feasibility in treating a wide range of pathologies through autologous cell replacement therapy. This review article describes in detail on three widely used approaches of somatic cell reprogramming: induced pluripotent stem cells, direct conversion and direct reprogramming, in the context of demyelination in the CNS. The potential limitations of each reprogramming technique are reviewed along with their distinct molecular approach to reprogramming. This is followed by an analysis on the scopes and challenges of its translational applications in deriving oligodendrocyte progenitor cells and oligodendrocytes for cell replacement treatment of demyelinating conditions in the CNS.

Protective mechanism of sulindac in an animal model of ischemic stroke.

BACKGROUND AND PURPOSE: The present study analyzed whether administration of sulindac, a non-steroidal anti-inflammatory drug (NSAID) would prevent, attenuate or repair ischemia induced brain injury and reverse functional impairment in a focal ischemia model of stroke. METHODS: Male Sprague-Dawley rats (weight 250-300 g) were subjected to middle cerebral artery occlusion (MCAO). Sulindac was given 2 days before and 24 h after ischemia at 0.2 mg/day with daily injections until sacrifice on day 3 or day 11. Infarct size was measured by TTC staining and western immunoblot was employed. RESULTS: TTC analysis of brain slices indicated a decrease in infarct size in sulindac treated animals. Western blot results indicated that sulindac induced expression of Hsp 27, a marker of cell stress, in the ischemic penumbra and core on days 3 and 11. Hsp 27 is important as a protective molecular chaperone. Increases were also found in the protective molecules Akt and Bcl-2 in the ischemic penumbra and core following sulindac administration. CONCLUSION: Our data indicate that administration of sulindac results in decreased infarct size and that there is a central role for the molecular chaperone Hsp 27, the pro-survival kinase Akt and the anti-apoptotic component Bcl-2 in mediating these protective effects.

Taurine exerts robust protection against hypoxia and oxygen/glucose deprivation in human neuroblastoma cell culture.

Stroke is one of the leading causes of mortality and disability worldwide. There is no effective treatment for stroke despite extensive research. Taurine is a free amino acid which is present at high concentrations in a range of organs including the brain, heart, and retina in mammalian systems. It had been shown that taurine can significantly increase cell survival under stroke conditions using both in vivo and in vitro models. Recently, we have found that several agents including granulocyte colony-stimulating factor (G-CSF), a stem cell enhancer and facilitator;S-methyl-N-diethylthiolcarbamate sulfoxide (DETC-MeSO), an NMDA receptor partial antagonist; sulindac, a potent antioxidant; and taurine, a neuroprotectant and calcium regulator, are effective in protecting against stroke-induced neuronal injury when used alone or in combination in both animal and tissue/cell culture models. In this chapter, we demonstrate that taurine can protect human neuroblastoma cells measured by ATP assay under conditions of hypoxia or oxygen/glucose deprivation (OGD). In addition, we found that taurine exerts its protective function by suppressing the OGD-induced upregulation of endoplasmic reticulum (ER) stress markers and proapoptotic proteins. A model depicting the mode of action of taurine in protecting neuroblastoma cells under OGD conditions is presented.