NO-donating aspirin inhibits both the expression and catalytic activity of inducible nitric oxide synthase in HT-29 human colon cancer cells.
Nitric oxide-releasing aspirin (NO-ASA) is emerging as a potentially important chemopreventive agent against colon cancer. We examined in HT-29 human colon adenocarcinoma cells the effect of NO-ASA on the inducible form of nitric oxide synthase (NOS2), an enzyme implicated in colon carcinogenesis. NO-ASA inhibited in a time- and concentration-dependent manner the expression of NOS2 up to 70% compared to control (IC50 for this effect = 46 microM). NO-ASA also decreased the corresponding steady-state mRNA levels and this reduction preceded the reduction of protein levels by at least 6 h. NO-ASA also reduced the enzymatic activity of NOS2, as determined by a direct enzyme assay (maximal reduction = 80%) and by determining the accumulation of NO in the culture medium (IC50 for this effect = 36 microM). These effects of NO-ASA on NOS2 were paralleled by inhibition in cell growth (IC50 = 8.5 microM). These findings indicate that NO-ASA profoundly inhibits both the expression and enzymatic activity of NOS2 and suggest that these effects may represent an important mechanism for the colon cancer chemopreventive effect of NO-ASA.
Spiegel
Adam
A
Division of Cancer Prevention, SUNY at Stony Brook, Stony Brook, NY 11794-5200, USA.
Hundley
Thomas R
TR
Chen
Jie
J
Gao
Jianjun
J
Ouyang
Nengtai
N
Liu
Xiaoping
X
Go
Mae F
MF
Tsioulias
George J
GJ
Kashfi
Khosrow
K
Rigas
Basil
B
D000230:Adenocarcinoma / Q000201:enzymology* / Q000473:pathology; D001241:Aspirin / Q000494:pharmacology*; D001483:Base Sequence; D002384:Catalysis; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology; D017931:DNA Primers; D019073:HT29 Cells; D006801:Humans; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000235:genetics
D017931:DNA Primers; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D001241:Aspirin