N-methyl-N-nitrosourea-induced apoptosis of photoreceptor cells in Sprague-Dawley rats via nuclear factor-kappaB.
BACKGROUND
Previous studies have showed that photooxidative stress can lead to down-modulation of nuclear factor-kappa B (NF-kappaB) activity causing apoptosis of cultured photoreceptor cells. This study aimed at investigating whether NF-kappaB was involved in photoreceptor cells apoptosis induced by N-methyl-N-nitrosourea (MNU) in rats.


METHODS
A single intraperitoneal injection of 60 mg/kg MNU was given to 50-day-old female rats. At different intervals after MNU treatment, the animals were sacrificed. Retinal damage was examined by a light microscope. The apoptotic index of the photoreceptor cells was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). NF-kappaB was analysed by Western blot and Transcriptin Factor Assay Kits.


RESULTS
The pyknosis of the photoreceptor nuclei and the disorientation of the outer segment of the photoreceptor layer was seen after MNU treatment for 24 hours. The outer nuclear layer and photoreceptor layer were almost completely lost at 7 days. Photoreceptor cells apoptosis reached the peaked value at 24 hours. In apoptotic cascade, the protein levels of NF-kappaB p65 were only detected after MNU treatment for 12 and 24 hours in the nucleus. Conversely, the amounts of IkappaBalpha were markedly increased in the cytoplasm as well as in the nucleus. The activity of NF-kappaB p65 in the nucleus was down-modulated in the end.


CONCLUSIONS
MNU-induced photoreceptor cell destruction was attributed to the apoptotic process by down-regulating the activation of NF-kappaB p65.
Yang
Jin-nan
JN
Department of Pharmacy, Xinxiang Medical College of Henan Province, Xinxiang 453003, China.
Luo
Lin
L
Lin
Shao-chun
SC
Chen
Jin-mao
JM
Li
Dai
D
Hu
Shi-xing
SX
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002467:Cell Nucleus / Q000378:metabolism; D005260:Female; D020672:I-kappa B Proteins / Q000032:analysis / Q000502:physiology; D008770:Methylnitrosourea / Q000633:toxicity*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000032:analysis / Q000502:physiology*; D010786:Photoreceptor Cells / Q000737:chemistry / Q000187:drug effects* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000187:drug effects / Q000473:pathology
D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D000072000:NF-KappaB Inhibitor alpha; D008770:Methylnitrosourea