【Objective】 To explore the optimum concentration of SP600125 to inhibit JNK signaling pathway induced by UVA in human dermal fibroblasts

and lay the foundation for studying the role of this pathway in photoaging. 【Methods】 Human dermal fibroblasts were derived from the circumcised foreskin of children

and subjected to primary culture. CCK-8 assay combined with fluorescence microscope was firstly performed to evaluate the cellular viability and observe cellular morphology to determine the non-toxic doses of UVA and SP600125 for the next experiment. Then

Western-blot was applied to detect the time-course of phospho-c-Jun after UVA irradiation. Finally

Western-blot was carried out to study whether the chosen concentration of SP600125 inhibited UVA-induced phospho-c-Jun. 【Results】 Treatments with ≤10 J/cm2 UVA irradiation or ≤2 μmol/L SP600125 could keep cellular viability more than 90%. However

the combined treatment with ≤800 nmol/L SP600125 and UVA could maintain irradiated-cell viability more than 90%. 1 μmol/L SP600125 significantly decreased irradiated-cell viability to 67.1%

and some cells were observed shrinking

broken and dead. Moreover

2 μmol/L SP600125 reduced cellular viability to 7.6%

and most cells were found deformed

broken and dead. Compared with 0 h group

the expression of phospho-c-Jun was found to be remarkably increased at both 0.75 h and 1.5 h

and resumed from 3 h after UVA irradiation. UVA-induced expression of P-c-Jun was found to be dose-dependently inhibited by 200-800 nmol/L SP600125 at 1.5 h after irradiation. 【Conclusion】   200-800 nmol/L SP600125 much lower than that commonly used could inhibit JNK signaling pathway activated by UVA in human dermal fibroblasts. JNK signaling pathway may play an antiapoptotic role in UVA-irradiated human dermal fibroblasts.