Akt/mTOR Activation Confers Protections Against Uvb-induced Apoptosis In HaCaT Cells

Background:KC apoptosis is closely related to many skin diseases such as psoriasis, lichen planus, eczema, vitiligo, skin aging and skin cancer. KC apoptosis is vulnerable to environmental factors in which Ultraviolet B (UVB) radiation is particularly important. UVB radiation cause skin sunburn easily, and chronic long-term radiation can cause skin photoaging and even skin cancer occurrence. In the process, KC abnormal apoptosis is an important pathophysiology basis. Recent studies have showed that UVB could activate KC anti-apoptotic signaling molecule phosphatidylinositol 3-kinase (PI3K) and Akt in vivo and in vitro. Insulin-like growth factor-1 receptor (IGF-1R) activation confers protections against UVB-induced apoptosis, and IGF-1R deletion can enhance UVB-induced KC apoptosis. This confirmed that UVB could activate IGF-1R and promote KC survival. The above means that anti-apoptosis was along with KC apoptosis induced by UVB radiation, but the exact mechanism remains unclear.Objective:Through UVB irradiation HaCaT in vitro, testing expression level of p-EGFR, p-Akt, S6, p-S6K, p-4EBP1 in the Akt/mTOR pathway, and detecting the effect of the signal transduction pathway on HaCaT apoptosis, provide a new theoretical basis, clarify the molecular mechanism of vitiligo, skin aging and skin cancer, provide the prevention and treatment of these diseases. Methods:Western blotting to test expression level of Akt/mTOR signaling pathway molecule, immune fluorescent Hoechst 33342 staining to detect cell apoptosis. Results:1.UVB could activate Akt/mTOR pathway in HaCaT cells, in a dose-dependent manner(5mJ/cm2 ~30mJ/cm2), and in a time-dependent manner(5min~30min). 2.EGFR inhibitor PD153035 pretreatment significantly inhibited UVB-induced expression of p-EGFR(1068), also significantly inhibited UVB-induced expression of p-Akt(Ser473,T308), p-S6(S235/236). 3.PI3K inhibitor LY 294002 pretreatment significantly inhibited UVB-induced expression of p-Akt(Ser473), also inhibited UVB-induced expression of p-4EBP1(S65), p-S6(S235/236), p-S6K(S235/236). 4. Rapamycin pretreatment did not change UVB-induced expression of p-AKT(Ser473) (P>0.05), but significantly inhibited UVB-induced expression of p-4EBP1(S65), p-S6(S235/236), p-S6K(S235/236). 5. PI3K inhibitor LY 294002 and mTOR inhibitor rapamycin could enhance UVB-induced apoptosis of HaCaT cells.Conclusions:Akt/mTOR activation confers protections against UVB-induced apoptosis in HaCaT cells.