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The Differential Role of Nitric Oxide Synthases in Ultraviolet Light B‐induced Apoptosis
Author(s) -
liu wei,
Wu Shiyong
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.890.5
Subject(s) - hacat , apoptosis , nitric oxide , nitric oxide synthase , chemistry , enos , poly adp ribose polymerase , microbiology and biotechnology , biochemistry , enzyme , biology , in vitro , polymerase , organic chemistry
Ultraviolet light (UV) activates nitric oxide synthase(s) (NOSs), which produces nitric oxide (NO). However the involvement of each NOS in UV‐induced signaling is not clear. The role of NO in UV‐induced apoptosis remains controversial. In this study, we analyzed expression and activation of NOSs in UVB‐irradiated keratinocytes HaCaT. We also determined the roles of NOSs in UV‐induced apoptosis. Our data showed that the expression of nNOS was increased and then decreased at 12 h and 24 h post‐UV respectively. While eNOS expression was not changed by UV, a decreased amount of coupled eNOS with an increased amount of uncoupled eNOS was observed within half‐hour of UV‐treatment. There was no increased level of iNOS was detected after UV‐irradiation. These results suggested that UV‐induced NO elevation is mainly regulated by cNOS. To determine the role of each cNOS and NO in UV‐induced apoptosis, we analyzed the extent of effect of a broad NOS inhibitor N‐nitro‐L‐arginine methyl ester (L‐NAME) on apoptotic death of HaCaT upon UV‐irradiation. Our data showed that NO was increased almost immediately and peaked at 18 h after UV‐irradiation. A pulse inhibition of NOS in the early phase (0‐0.5 h) partially inhibits UV‐induced apoptosis. However, a prolonged inhibition of NOS (0‐18 h) promotes apoptosis after UV‐treatment. In addition, the caspase 3 activity, but not amount, was changed in the treated cells and was correlated with the PARP cleavage and apoptosis of the HaCaT cells. Base on the results, we propose that in the early stage of UV‐irradiation, eNOS is uncoupled and produces O 2‐ and promotes apoptosis. In the late stage of UV‐irradiation, the expression of nNOS is increased and the elevated [NO] produced by nNOS inhibits caspase‐3 activity and apoptosis of the irradiated cells.