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NO-donating aspirin induces phase II enzymes in vitro and in vivo
Jianjun Gao1, Khosrow Kashfi, Xiaoping Liu
1Division of Cancer Prevention, Department of Medicine, SUNY at Stony Brook, NY 11794, USA.
Abstract:
Modulation of drug metabolizing enzymes, leading to facilitated elimination of carcinogens represents a successful strategy for cancer chemoprevention. Nitric oxide-donating aspirin (NO-ASA) is a promising agent for the prevention of colon and other cancers. We studied the effect of NO-ASA on drug metabolizing enzymes in HT-29 human colon adenocarcinoma and Hepa 1c1c7 mouse liver adenocarcinoma cells and in Min mice treated with NO-ASA for 3 weeks. In these cell lines, NO-ASA induced the activity and expression of NAD(P)H:quinone oxireductase (NQO) and glutathione S-transferase (GST). Compared with untreated Min mice, NO-ASA increased in the liver the activity (nmol/min/mg; mean+/-SEM for all) of NQO (85+/-6 versus 128+/-11, P<0.05) and GST (2560+/-233 versus 4254+/-608, P<0.005) and also in the intestine but not in the kidney; the expression of NQO1 and GST P1-1 was also increased. NO-ASA had only a marginal effect on P450 1A1 and P450 2E1, two phase I enzymes. The release of NO from NO-ASA, determined with a selective microelectrode was paralleled by the induction of NQO1 and abrogated by NO scavengers; an exogenous NO donor also induced the expression of NQO1. NO-ASA induced concentration-dependently the translocation of Nrf2 into the nucleus as documented by immunofluorescence and immunoblotting; this paralleled the induction of NQO1 and GST P1-1. Thus NO-ASA induces phase II enzymes, at least in part, through the action of NO that it releases and by modulating the Keap1-Nrf2 pathway; this effect may be part of its mechanism of action against colon and other cancers.
Insights
Nitric oxide-donating aspirin (NO-ASA) boosts cancer-fighting enzymes like NAD(P)H:quinone oxireductase (NQO) and glutathione S-transferase (GST). This NO-ASA effect, driven by nitric oxide, may help prevent colon cancer.
Area of Science:
- Biochemistry
- Pharmacology
- Cancer Research
Background:
- Cancer chemoprevention can be achieved by modulating drug metabolizing enzymes to enhance carcinogen elimination.
- Nitric oxide-donating aspirin (NO-ASA) is a potential agent for preventing colon and other cancers.
Purpose of the Study:
- To investigate the effects of NO-ASA on drug metabolizing enzymes in human colon and mouse liver cancer cells, as well as in Min mice.
- To elucidate the role of nitric oxide (NO) and the Nrf2 pathway in NO-ASA's chemopreventive mechanism.
Main Methods:
- Treatment of HT-29 colon adenocarcinoma and Hepa 1c1c7 liver adenocarcinoma cell lines with NO-ASA.
- Administration of NO-ASA to Min mice for three weeks.
- Assays for enzyme activity (NQO, GST), enzyme expression (NQO1, GST P1-1), P450 activity, NO release, and Nrf2 translocation.
Main Results:
- NO-ASA significantly induced the activity and expression of NAD(P)H:quinone oxireductase (NQO) and glutathione S-transferase (GST) in both cell lines and in the liver and intestine of Min mice.
- The induction of NQO1 and GST P1-1 by NO-ASA was dependent on nitric oxide release and involved the activation of the Keap1-Nrf2 pathway, evidenced by Nrf2 nuclear translocation.
- NO-ASA had minimal impact on Phase I enzymes like P450 1A1 and P450 2E1.
Conclusions:
- NO-ASA effectively induces Phase II drug metabolizing enzymes, NQO and GST, in colon and liver cancer models.
- The chemopreventive effects of NO-ASA are, at least partly, mediated by nitric oxide release and subsequent modulation of the Keap1-Nrf2 pathway.
- These findings support NO-ASA's potential as a chemopreventive agent for colon and other cancers.
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