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Nitric oxide-induced cellular stress and p53 activation in chronic inflammation
Lorne J Hofseth1, Shin'ichi Saito, S Perwez Hussain
1Laboratories of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Free radical-induced cellular stress contributes to cancer during chronic inflammation. Here, we investigated mechanisms of p53 activation by the free radical, NO. NO from donor drugs induced both ataxia-telangiectasia mutated (ATM)- and ataxia-telangiectasia mutated and Rad3-related-dependent p53 posttranslational modifications, leading to an increase in p53 transcriptional targets and a G(2)M cell cycle checkpoint. Such modifications were also identified in cells cocultured with NO-releasing macrophages. In noncancerous colon tissues from patients with ulcerative colitis (a cancer-prone chronic inflammatory disease), inducible NO synthase protein levels were positively correlated with p53 serine 15 phosphorylation levels. Immunostaining of HDM-2 and p21(WAF1) was consistent with transcriptionally active p53. Our study highlights a pivotal role of NO in the induction of cellular stress and the activation of a p53 response pathway during chronic inflammation.
Insights
Nitric oxide (NO) activates the p53 pathway, inducing cellular stress and a G2M cell cycle checkpoint, particularly during chronic inflammation. This NO-driven p53 activation is observed in ulcerative colitis tissues, linking inflammation to cancer risk.
Area of Science:
- Cellular biology
- Molecular oncology
- Inflammation research
Background:
- Chronic inflammation is linked to cancer development.
- Free radicals, such as nitric oxide (NO), play a role in cellular stress.
- The p53 tumor suppressor protein is crucial in cancer prevention.
Purpose of the Study:
- To investigate the mechanisms by which NO activates p53.
- To explore the role of NO-induced p53 activation in chronic inflammation and cancer.
- To examine the correlation between NO and p53 activity in human ulcerative colitis tissues.
Main Methods:
- Utilized NO donor drugs to induce NO in cell cultures.
- Assessed p53 posttranslational modifications dependent on ATM and ATR kinases.
- Analyzed p53 transcriptional targets and cell cycle progression (G2M checkpoint).
- Co-cultured cells with NO-releasing macrophages.
- Examined noncancerous colon tissues from ulcerative colitis patients for inducible NO synthase (iNOS) and phosphorylated p53 (Ser15).
- Performed immunostaining for HDM-2 and p21(WAF1).
Main Results:
- NO induced ATM- and ATR-dependent p53 modifications, increasing p53 targets and a G2M checkpoint.
- Similar p53 modifications were observed in cells co-cultured with NO-releasing macrophages.
- In ulcerative colitis tissues, iNOS levels positively correlated with p53 serine 15 phosphorylation.
- HDM-2 and p21(WAF1) staining indicated transcriptionally active p53.
Conclusions:
- NO is a significant inducer of cellular stress.
- NO activates a p53 response pathway through posttranslational modifications.
- This NO-mediated p53 activation is relevant in the context of chronic inflammation and associated cancer risk, as seen in ulcerative colitis.