The Role of PI3K/AKT/HIF-1α Pathway in the Effect of Nano-TiO₂ on Lactate Production in TM4 Cells

Titanium dioxide nanoparticles (nano-TiO₂) can cause a reduction in sperm counts, and lactate production in Sertoli cells plays a key role in spermatogenesis. The aim of this study was to evaluate the effect of nano-TiO₂ on lactate production in mouse Sertoli cell line (TM4 cells) and to investigate whether the effect is mediated through the PI3K/AKT/HIF-1α pathway. After TM4 cells were treated with different concentrations of nano-TiO₂ for 48 h, cell viability, contents of glucose and lactate, and the expression levels of GLUT3 and key enzymes (HK1, HK2, PFKM, ENO1, LDH) during lactate production were detected. PI3K/AKT/HIF-1α pathway proteins were measured. In addition, PI3K agonist (IGF-1) was added to explore whether nano-TiO₂ regulates HIF-1α through PI3K/AKT pathway, thereby affecting the production of lactate in TM4 cells. The results showed that nano-TiO₂ significantly inhibited TM4 cell viability, increased glucose content, decreased lactate content, and downregulated the expression levels of GLUT3 and key enzymes during lactate production. Meanwhile, nano-TiO₂ decreased the expression of PI3K/AKT pathway phosphorylated proteins and HIF-1α, and IGF attenuated this effect of nano-TiO₂. Collectively, nano-TiO₂ downregulated the expression level of proteins and enzymes related to lactate production in TM4 cells by inhibiting PI3K/AKT/HIF-1α pathway, resulting in the decrease of lactate production in TM4 cells.