Taurine and Glutamic Acid (Research)

·       Leon, R., et al.  Protective function of taurine in glutamate-induced apoptosis in cultured neurons.  J Neurosci Res.  2008.

Department of Biomedical Science, Florida Atlantic University, Boca Raton, Florida.

Previously, the authors showed that taurine protects neurons against glutamate-induced excitotoxicity by inhibiting the glutamate-induced increase of [Ca(2+)](i).  In this study, they report that taurine prevents glutamate-induced chromosomal condensation, indicating that taurine inhibits glutamate-induced apoptosis.  They found that Bcl-2 was down-regulated while Bax was up-regulated by glutamate treatment, and these changes were prevented in the presence of taurine.  The authors have also shown that taurine inhibits glutamate-induced activation of calpain.  Furthermore, calpastatin, a specific calpain inhibitor, also prevented glutamate-induced cell death.  Here the authors propose the mechanisms underlying glutamate-induced apoptosis and taurine's inhibition of glutamate-induced apoptosis to be as follows:  glutamate stimulation induces [Ca(2+)](i) elevation, which in turn activates calpain; activation of calpain leads to a reduction of Bcl-2:Bax ratios; with decreased Bcl-2:Bax ratios Bax homodimers form, Bax homodimerization, and translocation to the mitochondria result in the release of cytochrome c; released cytochrome c in turn activates a downstream caspase cascade leading to apoptosis.  The antiapoptotic function of taurine is due to its inhibition of glutamate-induced membrane depolarization.