Effect Of Cathelicidin LL-37on Nuclear Factor-κB In Human Keratinocyte Under Ultraviolet B Irradiation

Background: Ultraviolet (UV) radiation is one of the most significant environmentalfactors affecting human skin. UV radiation, in particular the middle wavelength (UVB,290-320nm), can lead to a series of molecular events occurring including activation ofnuclear factor-κB (NF-κB) and the expression of cathelicidin LL-37in human skin. Ithas been reported LL-37can significantly inhibit LPS-induced translocation of theNF-kB in human monocytic cells(THP-1)by Mookherjee et al. It is unclear whetherLL-37could have an impact on UVB-induced translocation of the NF-kB in humankeratinocytes.Objective: To investigate the effect of cathelicidin LL-37on the expression andtranscriptional activity of NF-κB in human keratinocytes under UVB irradiation;provide some implications for UVB radiation on the skin immune system and a newtheoretical basis for dermatologists using equipments of UVB to diagnose and treatphotodermatoses and other skin diseases.Methods: Cultured immortalized human keratinocyte cell line(HaCaT cells)andnormal human keratinocyte(NHK)were co-cultured with different concentrations ofLL-37(the final concentrations:0,0.5,2,5,10,20ug/mL) for four hours after120mJ/cm~2UVB irradiation. The expression and transcriptional activity of NF-κB weredetected by western blotting and electrophoretic motility shift assay (EMSA),respectively. Results:(1) The secretions of NF-κB p65from UVB radiation groups were statisticallysignificant compare with the control groups with a value of P<0.001in HaCaT cellsand NHK. Compare with UVB radiation groups, the secretions of NF-κB p65wereremarkably reduced in the presence of LL-37in a dose-dependent manner(the UVBradiation group in the presence of0.5μg/mL LL-37in HaCaT cells with a value ofP<0.05, other groups with a value of P<0.001).(2) The transcriptional activity ofNF-κB from UVB radiation groups were statistically significant compare with thecontrol groups (UVB radiation group in HaCaT cells with a value of P<0.05, UVBradiation group in NHK with a value of P<0.001). Compare with UVB radiation groups,the transcriptional activity of NF-κB were reduced in the presence of LL-37in adose-dependent manner. In HaCaT cells, the UVB radiation groups in the presence of2,5,10μg/mL LL-37with a value of P<0.05, the20μg/mL LL-37group with a value ofP<0.001, the0.5μg/mL LL-37group without statistically significant difference; inNHK, the UVB radiation groups in the presence of10μg/mL LL-37with a value ofP<0.05, the20μg/mL LL-37group with a value of P<0.001, the other groups withoutstatistically significant difference.Conclusions: The expression and transcriptional activity of NF-κB in HaCaT cells andNHK could be activated by UVB irradiation and this effect could be inhibitedsignificantly by LL-37in a dose-dependent manner.