Taurine protects R28 cells from hypoxia/re-oxygenation-induced damage via regulation of mitochondrial energy metabolism

Oxidative-induced damage and hypoxia/re-oxygenation (H/R) injury are common causes of irreversible visual impairment. The goals of this study were to explore the effects of taurine on R28 cells under the two damage models and the underlying mechanisms. Low doses of taurine supplementation promoted cell viability, mitochondrial membrane potential (MMP), SOD levels, ATP contents and attenuated cytotoxicity and intracellular ROS generation of the R28 cells under the two kinds of damage. The expression level of GTPBP3, a mitochondrial-tRNA (mt-tRNA) modification enzyme that catalyzes the taurine involved modification, was decreased under the two damage and taurine could reverse the reduction. After knocking down GTPBP3, the R28 cells become vulnerable to damage. The viability, cytotoxicity, MMP and intracellular ROS level of knockdown cells changed more obviously under the H/R injury than those of control cell. We also found that knockdown of GTPBP3 significantly decreased mitochondrial energy metabolism by measuring the oxidative respiration rate by the Seahorse XFe24 extracellular flux analyzer. The protection of low doses of taurine disappeared on knockdown R28 cells, indicating that GTPBP3 is crucial in the protection mechanisms of taurine. However, the impacts of the reduction of GTPBP3 level can be reversed by relatively high doses of taurine, implying the protection effects of taurine were dose-dependent, and there were more complicated mechanisms remain to be explored. This study explored a new mechanism of the neuroprotective effects of taurine, which depend on the GTPBP3-mediated taurine modification of mt-tRNAs and the promotion of mitochondrial energy metabolism.