We performed Mann Whitney U tests to detect differences of continuous variables

imulates Endothelin B Receptor via a MSK1 Pathway Fig 6. Effects of treatment with UVB and/or PBE on phosphorylation of MAPKs. The phosphorylation levels of p38, JNK and ERK1/2 in NHMs at 15 min after treatment with or without 60 mJ/cm2 UVB and/or 30 g/ml PBE. Expression levels were detected by specific antibodies to non-phospho and phospho MAPKs. Error bars 181223-80-3 represent S.D. from triplicate experiments. P<0.05 and P<0.01 against NHMs UVB-irradiated in the absence of PBE, respectively. doi:10.1371/journal.pone.0128678.g006 that PBE has a potential to inhibit pigmentation by preventing the autoxidation of melanin. Since PBE can behave as an antioxidant and a scavenger for ROS generated by UVB irradiation, its possible inhibitory effect on the increased expression of EDNRB could be accounted for by the depletion of generated ROS if treated pre-irradiation. However, our observation that post-irradiation treatment with PBE can also abrogate the increased EDNRB expression strongly suggests that PBE abrogates the up-regulation of EDNRB expression via an unknown novel signaling mechanism in a ROS depletion-independent manner because the ROS lifetime is very short , not sufficient to deplete the generated ROS when treated immediately after UVB radiation. UVB exposure of human keratinocytes was reported to activate NFB signaling by stimulating IKK kinase which phosphorylates IkB, causing NFBp65 to transduce toward translocation into the nucleus during the signaling pathway downstream of the preceding p38 or JNK activation. In contrast, UVB exposure of human melanocytes induces little or no activation of the NFB pathway compared to the distinct activation of their upstream pathways such as p38 and JNK. In melanocytes and melanoma, UVB has been shown to induce phosphorylation of the p38 and JNK/stress-activated protein kinase pathways, whereas NFkB remains at a constantly high expression level. The activation of p38 or JNK following UVB radiation is 10 / 17 UVB Stimulates Endothelin B Receptor via a MSK1 Pathway Fig 7. Effects of treatment with UVB and/or PBE PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19696752 on the phosphorylation of MSK1. The phosphorylation level of MSK1 at Ser376 residue and Thr581 residue at 15 min after treatment with or without 60 mJ/cm2 UVB and/or 30 g/ml PBE. Expression levels were detected by specific antibodies to nonphospho and phospho MSK1. Error bars represent S.D. from triplicate experiments. P<0.05 against NHMs UVB-irradiated in the absence of PBE. doi:10.1371/journal.pone.0128678.g007 mediated by initial stress-activated protein kinases, which are activated by ROS via redox-interfering mechanisms involved in protein kinases as well as their conjugated protein phosphatases. Owing to these mechanisms, many antioxidants can suppress UVB-induced cellular events by scavenging generated ROS when treated pre-irradiation. This evidence indicates that the hitherto reported inhibitory effects of antioxidants on the UVB-induced activation of IKKinase leading to the diminished nuclear translocation PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19697345 of NFB may occur via the abolishing effect on the activation of p38 or JNK due to the preceding ROS depletion by pretreatment with antioxidants. Therefore, it is of considerable importance to determine the signaling mechanism by which the post-irradiation treatment with PBE can abrogate the increased EDNRB expression. Fig 8. Effect of H89 on the gene expression of MITF and EDNRB in NHMs exposed to UVB. The indicated concentration of H89 was added into the medium immediately after UVB