Abstract: Human immortalized keratinocytes (HaCaT) were used as materials and effects of ultraviolet A (UVA), tanshinone ⅡA (TS ⅡA), and combination of UVA and TS ⅡA on cell viability and mitogen-activated protein kinase (MAPK) signaling protein phosphorylation were studied using CCK8 and Western blot respectively. The results showed that UVA at 10 J/cm² lowered cell viability to about 70% of that of control, while 20 J/cm² dose led to further reduction to about 55%. Low concentration TSⅡA had no impact on cell viability, and high concentration TSⅡA (85 μmol/L) could decrease cell viability to 75%. When combined together, UVA and TS ⅡA significantly exhibited together inhibitory effect on cell viability compared to their individual effects. UVA irradiation elevated the phosphorylation level of p38 and JNK in MAPK cascade, but had no effect on phosphorylation of Erk. TS ⅡA could promote phosphorylation of p38 and JNK induced by low dose UVA (2 J/cm²). The above results indicate that UVA induces HaCaT apoptosis by promoting phosphorylation of p38 and JNK, and in turn, TS ⅡA further promotes its phosphorylation and accelerated HaCaT apoptosis

Key words: apoptosis, HaCaT, mitogen-activated protein kinase (MAPK), tanshinone ⅡA (TS ⅡA), ultraviolet A (UVA)