TY - JOUR
T1 - Involvement of oxidative stress in NF-κB activation in endothelial cells treated by photodynamic therapy
AU - Volanti, Cédric
AU - Matroule, Jean-Yves
AU - Piette, Jacques
PY - 2002/1/1
Y1 - 2002/1/1
N2 - In human endothelial cells ECV 304 and HMEC-1 photosensitized by pyropheophorbide-a methylester (PPME) in sublethal conditions transcription factor Nuclear Factor kappa B (NF-κB) activation takes place for several hours. Activated NF-κB was functional because it stimulated the transcriptional activation of either a transfected reporter gene or the endogenous gene encoding interleukin (IL)-8. Concomitant with NF-κB activation, inhibitor of NF-κBα (IKBα) was degraded during photosensitization and IKBβ, p100, p105 and IKBε were slightly modified. Reactive oxygen species (ROS) were shown to be crucial intermediates in the activation because antioxidants strongly decreased NF-κB activation. Using both a fluorescent probe and isotope substitution, it was shown that ROS, and especially singlet oxygen (1O2), were important in the activation process. Because NF-κB activation in the presence of ROS was suspected to proceed through a pathway independent of the IκB kinases (IKK), we demonstrated that the IKK were indeed not activated by photosensitization but required an intact tyrosine residue at position 42 on IKBα, suggesting the involvement of a tyrosine kinase in the activation process. This was further reinforced by the demonstration that herbimycin A, a tyrosine kinase inhibitor, prevented NF-κB activation by photosensitization but not by TNFα, a cytokine known to activate NF-κB through an IKK-dependent mechanism.
AB - In human endothelial cells ECV 304 and HMEC-1 photosensitized by pyropheophorbide-a methylester (PPME) in sublethal conditions transcription factor Nuclear Factor kappa B (NF-κB) activation takes place for several hours. Activated NF-κB was functional because it stimulated the transcriptional activation of either a transfected reporter gene or the endogenous gene encoding interleukin (IL)-8. Concomitant with NF-κB activation, inhibitor of NF-κBα (IKBα) was degraded during photosensitization and IKBβ, p100, p105 and IKBε were slightly modified. Reactive oxygen species (ROS) were shown to be crucial intermediates in the activation because antioxidants strongly decreased NF-κB activation. Using both a fluorescent probe and isotope substitution, it was shown that ROS, and especially singlet oxygen (1O2), were important in the activation process. Because NF-κB activation in the presence of ROS was suspected to proceed through a pathway independent of the IκB kinases (IKK), we demonstrated that the IKK were indeed not activated by photosensitization but required an intact tyrosine residue at position 42 on IKBα, suggesting the involvement of a tyrosine kinase in the activation process. This was further reinforced by the demonstration that herbimycin A, a tyrosine kinase inhibitor, prevented NF-κB activation by photosensitization but not by TNFα, a cytokine known to activate NF-κB through an IKK-dependent mechanism.
UR - http://www.scopus.com/inward/record.url?scp=0036363622&partnerID=8YFLogxK
U2 - 10.1562/0031-8655(2002)075<0036:IOOSIN>2.0.CO;2
DO - 10.1562/0031-8655(2002)075<0036:IOOSIN>2.0.CO;2
M3 - Article
C2 - 11837326
AN - SCOPUS:0036363622
SN - 0031-8655
VL - 75
SP - 36
EP - 45
JO - Photochemistry and Photobiology
JF - Photochemistry and Photobiology
IS - 1
ER -