Inhibition of the cleaved half of tRNA^Gly enhances palmitic acid-induced apoptosis in human trophoblasts

Palmitic acid (PA) induces apoptosis in the human trophoblast cell line HTR8/SVneo. However, the molecular mechanism underlying this effect remains unclear. Although small noncoding RNAs are involved in trophoblast growth and invasion during early pregnancy, the functional roles of tRNA-derived species are currently unknown. Therefore, the purpose of this study was to examine the involvement of tRNA-derived species in PA-induced apoptosis in human trophoblasts. In this study, we investigate the expression and function of tRNA-derived stress-induced RNAs (tiRNAs) in HTR8/SVneo. We determined the expression of tiRNAs in HTR8/SVneo cells in response to PA. Then, we transfected inhibitor of target tiRNA in HTR8/SVneo with or without PA to examine the tRNA-derived species-regulated intracellular signal transduction by detecting calcium homeostasis, mitochondrial membrane potential, and signaling proteins. We found that the expression of tRNA^Gly-derived tiRNAs decreased in PA-treated human trophoblasts. Moreover, inhibition of tiRNA^GlyCCC/GCC enhanced the PA-induced apoptosis along with the induction of DNA fragmentation and mitochondrial depolarization. Inhibition of tiRNA^GlyCCC/GCC enhanced the expression of endoplasmic reticulum stress-related proteins and increased Ca²⁺ levels in the cytoplasm and mitochondria. Moreover, the levels of cytochrome c released from the mitochondria were synergistically affected by tiRNA^GlyCCC/GCC inhibitor and PA. Furthermore, artificial regulation of ANG inhibited the expression of tiRNA^GlyCCC/GCC and similar effects were observed upon the inhibition of tiRNA^GlyCCC/GCC in human trophoblasts. These results suggest that tiRNA^GlyCCC/GCC might be the molecule via which PA induces its effects in human trophoblasts.