Effects of steroid hormones and cyclosporine A on taurine-transporter activity in the RAW264.7 cell line

Understanding taurine CNS activity using alternative zebrafish models

Taurine is a highly abundant "amino acid" in the brain. Despite the potential neuroactive role of taurine in vertebrates has long been recognized, the underlying molecular mechanisms related to its pleiotropic effects in the brain remain poorly understood. Due to the genetic tractability, rich behavioral repertoire, neurochemical conservation, and small size, the zebrafish (Danio rerio) has emerged as a powerful candidate for neuropsychopharmacology investigation and in vivo drug screening. Here, we summarize the main physiological roles of taurine in mammals, including neuromodulation, osmoregulation, membrane stabilization, and antioxidant action. In this context, we also highlight how zebrafish models of brain disorders may present interesting approaches to assess molecular mechanisms underlying positive effects of taurine in the brain. Finally, we outline recent advances in zebrafish drug screening that significantly improve neuropsychiatric translational researches and small molecule screens.

Ionomycin restores taurine transporter activity in cyclosporin-A treated macrophages

Taurine is accumulated at high concentrations in various tissues. The taurine transporter (TAUT) is responsible for the transportation of taurine in the cell. The transporter is affected by various stimuli to maintain cell volume. Macrophage cell volume varies in its activated states. In our experiment, it was found that the murine macrophage cell line, RAW264.7, expressed TAUT protein in its membrane. Its transporting activities could be blocked by beta-amino acid such as beta-alanine, but not by alpha-amino acids in this cell line, when assessed in RAW264.7 cells under the influence of immunosuppressive reagents, the activity of the TAUT was decreased by treatment with rapamycin (RM) or cyclosporin A (CSA). However, when ionomycin (IM) was added to this system, TAUT activity was recovered only in CSA-treated cells, in a concentration-dependent manner, in order to inhibit voltage gated Ca2+ channels, calmidazolium was added to the RAW264.7 cell line. Treatment of the cells with calmidazolium completely blocked TAUT. Furthermore, addition of IM to this system resulted in recovery the activity of TAUT again. When we added phorbol myristyl acetate (PMA) to the cell line, secretion of nitric oxide (NO) was increased 4-fold and the TAUT activity was decreased 5-fold. However, the addition of N-nitro L-arginine methyl ester (L-NAME), an inducible NO synthase (iNOS) inhibitor, to the PMA-treated cells induced recovery of TAUT activity. These results showed that the activity of TAUT was sensitive to both the intracellular concentrations of Ca2+ and NO.

Spinal taurine levels are increased 7 and 30 days following methylprednisolone treatment of spinal cord injury in rats

The amino acid taurine serves many functions in the nervous system serving as inhibitory neurotransmitter/neuromodulator, neurotrophin, antioxidant, and osmolyte. Taurine levels are increased following brain injury and glucocorticoid administration. Thus, the purpose of this study was to examine spinal taurine concentrations following spinal cord injury (SCI) and methylprednisolone (MP) treatment of SCI. A total of 44 adult male Sprague-Dawley rats were divided into control and lesion groups. Control rats received a T6 vertebral laminectomy while lesioned rats received a laminectomy followed by complete spinal transection. Half of the animals in each group received MP intravenously following sham-operation or SCI. Rats survived for 7 or 30 days and concentrations of taurine in spinal gray and white matter, in spinal segments both near and distant from the injury epicenter, were resolved by HPLC analysis. Taurine levels were increased 7 and 30 days following transection in spinal segments immediately adjacent to the lesion and were further elevated by MP treatment. No increases were seen in far rostral/caudal segments, and MP treatment alone had no effect on spinal taurine levels. These findings demonstrate that spinal injury results in increased taurine concentrations in spinal segments undergoing the greatest degree of cellular reactivity and tissue reorganization and that MP therapy potentiates these increases. These findings are significant in that they further characterize the effects of acute MP therapy in spinal tissue. Since taurine is thought to be involved in neuroprotection and/or regeneration following injury, the potentiation of taurine levels by MP treatment may relate to its therapeutic properties.