Abstract:

Objective To investigate the effects of UVA irradiation on the expression of inducible nitric oxide synthase （iNOS） and level of nitric oxide （NO） in HaCaT cells. Methods HaCaT cells were cultured, irradiated with different doses （1, 5, 10 J/cm2） of UVA. After another 24-, 48-, 72-hour culture, the mRNA and protein expressions of iNOS and level of NO were measured by RT-PCR, Western blot and Griess reagent kit, respectively. Results After the irradiation with 1, 5 or 10 J/cm2 of UVA, the mRNA expression of iNOS was observed in HaCaT cells at 24 h, reached a peak at 48 h, then decreased at 72 h; significant differences were found between the three time points （all P < 0.05）. No expression of iNOS protein was detected in HaCaT cells at any time point after irradiation with UVA of 1 J/cm2; meanwhile, with UVA irradiation of 5 and 10 J/cm2, the protein expression of iNOS increased at 24 h, peaked at 48 h, but was undetected at 72 h. In HaCaT cells irradiated with UVA of 1, 5 or 10 J/cm2, the level of NO showed an increase at 24 h, a marked increase at 48 h, and a stable increase at 72 h, and significant differences were noticed between irradiated cells and control cells at three time points （all P < 0.05）. In unirradiated HaCaT cells, no expression of iNOS mRNA or protein was observed with a low level of NO. Conclusions The changes in iNOS expression and NO level in HaCaT cells are related to the duration and dose of UVA irradiation.