PT  - JOURNAL ARTICLE
AU  - Kodela, Ravinder
AU  - Chattopadhyay, Mitali
AU  - Goswami, Satindra
AU  - Gan, Zong Yuan
AU  - Rao, Praveen P. N.
AU  - Nia, Kamran V.
AU  - Velázquez-Martínez, Carlos A.
AU  - Kashfi, Khosrow
TI  - Positional Isomers of Aspirin Are Equally Potent in Inhibiting Colon Cancer Cell Growth: Differences in Mode of Cyclooxygenase Inhibition
AID  - 10.1124/jpet.112.201970
DP  - 2013 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 85--94
VI  - 345
IP  - 1
4099  - http://jpet.aspetjournals.org/content/345/1/85.short
4100  - http://jpet.aspetjournals.org/content/345/1/85.full
SO  - J Pharmacol Exp Ther2013 Apr 01; 345
AB  - We compared the differential effects of positional isomers of acetylsalicylic acid (o-ASA, m-ASA, and p-ASA) on cyclooxygenase (COX) inhibition, gastric prostaglandin E2 (PGE2), malondialdehyde, tumor necrosis factor-alpha (TNF-α) levels, superoxide dismutase (SOD) activity, human adenocarcinoma colon cancer cell growth inhibition, cell proliferation, apoptosis, and cell-cycle progression. We also evaluated the gastric toxicity exerted by ASA isomers. All ASA isomers inhibit COX enzymes, but only the o-ASA exerted an irreversible inhibitory profile. We did not observe a significant difference between ASA isomers in their ability to decrease the in vivo synthesis of PGE2 and SOD activity. Furthermore, all isomers increased the levels of gastric and TNF-α when administered orally at equimolar doses. We observed a dose-dependent cell growth inhibitory effect; the order of potency was p-ASA > m-ASA ≈ o-ASA. There was a dose-dependent decrease in cell proliferation and an increase in apoptosis, with a concomitant Go/G1 arrest. The ulcerogenic profile of the three ASA isomers showed a significant difference between o-ASA (aspirin) and its two positional isomers when administered orally at equimolar doses (1 mmol/kg); the ulcer index (UI) for o-ASA indicated extensive mucosal injury (UI = 38), whereas m-ASA and p-ASA produced a significantly decreased toxic response (UI = 12 and 8, respectively) under the same experimental conditions. These results suggest that the three positional isomers of ASA exert practically the same biologic profile in vitro and in vivo but showed different safety profiles. The mechanism of gastric ulcer formation exerted by aspirin and its two isomers warrants a more detailed and thorough investigation.