Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice

Stefan Ambs, Mofolusara O. Ogunfusika, William G. Merriam, William P. Bennett, Timothy R. Billiar, Curtis C. Harris*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

148 Scopus citations


High concentrations of nitric oxide (NO) cause DNA damage and apoptosis in many cell types. Thus, regulation of NO synthase (NOS) activity is essential for minimizing effects of cytotoxic and genotoxic nitrogen oxide species. We have shown previously that NO-induced p53 protein accumulation down-regulates basal and cytokine-modulated inducible NOS (NOS2) expression in human cells in vitro. To further characterize the feedback loop between NOS2 and p53, we have investigated NO production, i.e., urinary nitrate plus nitrite excretion, and NOS2 expression in homozygous p53 knockout (KO) mice. We report here that untreated p53 KO mice excreted 70% more nitrite plus nitrate than mice with wild-type (wt) p53. NOS2 protein expression was constitutively detected in the spleen of untreated p53 KO mice, whereas it was undetectable in the spleen of wt p53 controls. Upon treatment with heat-inactivated Corynebacterium parvum, urinary nitrite plus nitrate excretion of p53 KO mice exceeded that of wt controls by approximately 200%. C. parvum treatment also induced p53 accumulation in the liver. Splenectomy reduced the NO output of C. parvum-treated p53 KO mice but not of wt p53 controls. Although NO production and NOS2 protein expression were increased similarly in KO and wt p53 mice 10 days after injection of C. parvum, NOS2 expression returned to baseline levels only in wt p53 controls while remaining up-regulated in p53 KO mice. These genetic and functional data indicate that p53 is an important transrepressor of NOS2 expression in vivo and attenuates excessive NO production in a regulatory negative feedback loop.

Original languageEnglish
Pages (from-to)8823-8828
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number15
StatePublished - 21 Jul 1998
Externally publishedYes


Dive into the research topics of 'Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice'. Together they form a unique fingerprint.

Cite this