Ultraviolet B light-induced nitric oxide/peroxynitrite imbalance in keratinocytes--implications for apoptosis and necrosis.
Elevation of nitric oxide (NO*) can either promote or inhibit ultraviolet B light (UVB)-induced apoptosis. In this study, we determined real-time concentration of NO* and peroxynitrite (ONOO(-)) and their role in regulation of membrane integrity and apoptosis. Nanosensors (diameter 300-500 nm) were used for direct in situ simultaneous measurements of NO* and ONOO(-) generated by UVB in cultured keratinocytes and mice epidermis. An exposure of keratinocytes to UVB immediately generated ONOO(-) at maximal concentration of 190 nm followed by NO(*) release with a maximal concentration of 91 nm. The kinetics of UVB-induced NO*/ONOO(-) was in contrast to cNOS agonist stimulated NO*/ONOO(-) from keratinocytes. After stimulating cNOS by calcium ionophore (CaI), NO* release from keratinocytes was followed by ONOO(-) production. The [NO*] to [ONOO(-)] ratio generated by UVB decreased below 0.5 indicating a serious imbalance between cytoprotective NO* and cytotoxic ONOO(-)-a main component of nitroxidative stress. The NO*/ONOO(-) imbalance increased membrane damage and cell apoptosis was partially reversed in the presence of free radical scavenger. The results suggest that UVB-induced and cNOS-produced NO* is rapidly scavenged by photolytically and enzymatically generated superoxide (O(2) (-)) to produce high levels of ONOO(-), which enhances oxidative injury and apoptosis of the irradiated cells.
Wu
Shiyong
S
Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA. wus1@ohio.edu
Wang
Lei
L
Jacoby
Adam M
AM
Jasinski
Krystian
K
Kubant
Ruslan
R
Malinski
Tadeusz
T
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D002462:Cell Membrane / Q000528:radiation effects; D004817:Epidermis / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D051379:Mice; D009336:Necrosis; D009569:Nitric Oxide / Q000378:metabolism* / Q000528:radiation effects; D030421:Peroxynitrous Acid / Q000378:metabolism* / Q000528:radiation effects; D013481:Superoxides; D014466:Ultraviolet Rays / Q000009:adverse effects*
D013481:Superoxides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide