Effect and regulatory mechanisms of three traditional Chinese medicines on HaCaT cells irradiated by UVB

Aim To investigate the production and removal of cyclobutane pyrimidine dimers (CPDs) after UVB irradiation and the effect of baikal skullcap root, szechwan lovge rhizome and epigallocatechingallate (EGCG) on the irradiation damage in HaCaT cells, and finally, to clarify the probable regulatory mechanisms.Methods HaCaT cells were cultured in RMPI-1640 medium with 10% fetal bovine serum. The time and dosage of UVB irradiation were conducted according to the experimental design. Tested medicines were added into the medium before or after UVB irradiation. The production and removal of CPDs were examined by immunohistochemical method; the p53 and PCNA mRNA expressions were examined by RT-PCR; the p53 and PCNA protein expressions were examined by Western blot. Results The damage of HaCaT cells was proportional with the dosage of UVB irradiation. CPDs appeared in HaCaT cells and immediately after irradiation reached the peak in 0.5 h and they were removed rapidly during the first 4 h and slowly thereafter. The production of CPDs was decreased when HaCaT cells were preincubated with baikal skullcap root solution before UVB irradiation and the removal of CPDs was accelerated when HaCaT cells were coincubated with szechwan lovge rhizome and EGCG solution after UVB irradiation(P0.05); UVB irradiation could induce mRNA and protein expressions of p53 and PCNA in cultured HaCaT cells and mRNA and protein levels of p53 and PCNA were decreased after tested medicine intervention in UVB irradiated group. Conclusions The photodamage of HaCaT cells induced by UVB irradiation was dose dependent, which induced the production of CPDs. DNA lesions could be repaired by cell itself; three traditional Chinese medicines could decrease the level of CPDs; inhibiting expressions of mRNA and proteins of p53 and PCNA may be part of mechanisms related to these photoprotecting effects of UVB irradiation.