RhEPO Upregulates the PPARγ Pathway in Long-term Cultured Primary Nerve Cells via PI3K/Akt to Delay Cell Senescence.

Abstract

Previous studies have confirmed that both recombinant human erythropoietin (rhEPO) and peroxisome proliferator-activated receptors γ (PPARγ) activator pioglitazone can protect senescent nerve cells, and their mechanisms involve enhancing cell antioxidant capacity and reducing cell apoptosis. However, whether the PPARγ pathway is involved in the rhEPO anti-aging process in neuronal cells is still unclear. In this study, to explore the relationship between rhEPO and the PPARγ pathway at the cellular level, primary nerve cells cultured for 22days were used to simulate the natural aging process of nerve cells. Starting on the 11th day of culture, rhEPO, LY294002, and GW9662 were added for treatment. Immunochemical methods and SA-β-gal staining were used to observe the changes in cellular antioxidant capacity and the fraction of senescent cells. The results showed that PPARγ blockade retarded the effect of rhEPO on the cellular antioxidant capacity and altered the fraction of senescent cells. It was confirmed that PPARγ was involved in rhEPO's anti-aging process in neuronal cells. Real-time fluorescent quantitative RT-PCR, Western blotting, and immunofluorescence staining were used to observe the changes in PPARγ pathway-related factors in nerve cells after rhEPO treatment. The results showed that rhEPO significantly upregulated the expression of PPARγ coactivator-1α (PGC-1α), PPARγ, and nuclear PPARγ in cells but did not affect the level of phosphorylated PPARγ protein, confirming that rhEPO has the ability to upregulate the PPARγ pathway. PI3K/Akt and PPARγ pathway blockade experiments were used to explore the relationships among rhEPO, PI3K/Akt, and PPARγ. The results showed that after PPARγ blockade, rhEPO had no significant effect on the PI3K/Akt pathway-related factor p-Akt, while after PI3K/Akt blockade, rhEPO's effects on PPARγ-related factors (PGC-1α, PPARγ, and nuclear PPARγ) were significantly decreased. It is suggested that rhEPO delays the PI3K/Akt pathway in the process of neuronal senescence, which is located upstream of PPARγ regulation. In conclusion, this study confirmed that rhEPO can upregulate the expression of PGC-1α and PPARγ in cells and the level of PPARγ protein in the nucleus to enhance the antioxidant capacity of cells and delay the senescence of nerve cells through the PI3K/Akt pathway. These findings will provide ideas for finding new targets for neuroprotection research and will also provide a theoretical basis and experimental evidence for rhEPO anti-aging research in neural cells.