UVB radiation-mediated expression of inducible nitric oxide synthase activity and the augmenting role of co-induced TNF-alpha in human skin endothelial cells.
Nitric oxide (NO) plays a pivotal role in ultraviolet radiation-induced inflammation in human skin. We had earlier reported on the inducible nitric oxide synthase (iNOS) inducing activity of UVA radiation. We now demonstrate that UVB-exposure induces expression of the iNOS in vessel endothelia of normal human skin and in cultured human dermal endothelial cells (HUDEC), although by a molecular mechanism different from UVA-mediated induction. With HUDEC, UVB induces iNOS expression and leads to significant enzyme activities, although at app. 5-fold lower levels than can be achieved with proinflammatory cytokines. In contrast to our earlier observation with UVA, cytokine-challenge combined with simultaneous UVB-exposure had no additive effects on iNOS expression nor activity. Interestingly, a time-delay between UVB-irradiation and cytokine-challenge enhances endothelial iNOS enzyme activity 2.5-fold over cytokines activation only. This time-dependent effect strongly correlates with UVB-induced endothelial TNF-alpha expression. In HUDEC addition of TNF-alpha results in enhanced expression of the inducible arginine transporter system CAT-2 essential for substrate supply and thus iNOS activity. In summary, UVB induces iNOS mRNA and enzyme activity in HUDEC. Moreover, UVB augments CAT-2 expression through a TNF-alpha- dependent mechanism which essentially contributes to increased iNOS activity.
Research Group Immunobiology, Heinrich-Heine-University of Dusseldorf, Dusseldorf, Germany. suschek@uni-duesseldorf.de
Christoph Viktor
CV
Suschek
Csaba
C
Mahotka
Oliver
O
Schnorr
Victoria
V
Kolb-Bachofen
D001120:Arginine / Q000378:metabolism; D027202:Cationic Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D020405:Dermis / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009924:Organ Culture Techniques; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*; D014466:Ultraviolet Rays
D027202:Cationic Amino Acid Transporter 2; D007375:Interleukin-1; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D001120:Arginine; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II