miR-4478 Promotes Ferroptosis of Nucleus Pulposus Cells through Targeting SLC7A11 to Induce IVDD.

Nucleus pulposus cells (NPC) are important for the development of intervertebral disc degeneration (IVDD). miR-4478 can aggravate IVDD, but whether it can aggravate IVDD by regulating ferroptosis in NPC remains unclear. The optimal level of ferroptosis activator RSL3 for eliciting ferroptosis in NPC was screened by Western blot and CCK-8 assay. The targeting relationship between miR-4478 and its potential target solute carrier family 7 member 11 (SLC7A11) was explored based on dual luciferase assay. On this basis, IVDD models were constructed. After over-expression or knockdown of miR-4478 or SLC7A11, CCK-8 and calcein-AM/PI assays were employed to evaluate cell damage. Flow cytometry, Western blot and Prussian blue staining were employed to evaluate oxidation and ferroptosis levels, and histopathological staining was applied to evaluate the intervertebral disc tissue injury degree. The optimal concentration of RSL3 was 1 μM. Under these conditions, miR-4478 or SLC7A11 can be effectively over-expressed or knocked down after transfection. Knockdown of miR-4478 can improve the survival rate of NPC, the level of Fe2+ ions, improve the pathological damage of intervertebral disc structure, reduce iron deposition in tissues, and significantly reduce expression of reactive oxygen species (ROS) and ferroptosis-related protein. The levels of antioxidant enzymes were significantly increased. When miR-4478 was over-expressed, the above phenomenon was reversed. On this basis, after SLC7A11 was over-expressed, the effect of miR-4478 up-regulation was weakened, and NPC ferroptosis was improved. miR-4478 can target SLC7A11 to promote NPC damage, peroxide accumulation and iron metabolism disorders, leading to ferroptosis, thereby inducing IVDD.