Salicylic acid (Synonyms: 2-Hydroxybenzoic Acid, NSC 180)

Salicylic acid inhibits cyclo-oxygenase-2 (COX-2) activity independently of transcription factor (NF-κB) activation.

Salicylic acid is an effective inhibitor of COX-2 activity at concentrations far below those required to inhibit NF-κB (20 mg/mL) activation. Salicylic acid inhibits prostaglandin E2 release when add together with interleukin 1β for 24 hr with an IC50 value of 5 μg/mL, an effect that is independent of NF-κB activation or COX-2 transcription or translation. Salicylic acid acutely (30 min) also causes a concentration-dependent inhibition of COX-2 activity measured in the presence of 0, 1, or 10 μM exogenous arachidonic acid. In contrast, when exogenous arachidonic acid is increased to 30 μM, Salicylic acid is a very weak inhibitor of COX-2 activity with an IC50 of >100 μg/mL. When added together with IL-1β for 24 hr, Salicylic acid causes a concentration-dependent inhibition of PGE2 release with an apparent IC50 value of approximately 5 μg/mL. The ability of Salicylic acid to directly inhibit COX-2 activity in A549 cells is tested after a 30-min exposure period, followed by the addition of different concentrations of exogenous arachidonic acid (1, 10, and 30 μM). Salicylic acid causes a concentration-dependent inhibition of COX-2 activity in the absence of added arachidonic acid or in the presence of 1 or 10 μM exogenous substrate with an apparent IC50 value of approximately 5 μg/mL. However, when the same experiments are performed using 30 μM arachidonic acid, Salicylic acid is an ineffective inhibitor of COX-2 activity, with an apparent IC50 value of more than 100 μg/mL, and achieves a maximal inhibition of less than 50%[1].

In C57Bl/6 DIO mice, Salicylic acid decreases both fasting and postprandial plasma glucose levels. Furthermore, there is a trend to reduce plasma triglyceride levels after Salicylic acid treatment in C57Bl/6 DIO mice (P=0.059). Salicylic acid significantly reduces 11β-HSD1 mRNA in omental adipose tissue in C57Bl/6 DIO mice, with a similar trend in mesenteric adipose (P=0.057). In mesenteric adipose of C57Bl/6 DIO mice, Salicylic acid also reduces 11β-HSD1 enzyme activity[2].

References:
[1]. Mitchell JA, et al. Sodium salicylate inhibits cyclo-oxygenase-2 activity independently of transcription factor (nuclear factor kappaB) activation: role of arachidonic acid. Mol Pharmacol. 1997 Jun;51(6):907-12.
[2]. Nixon M, et al. Salicylate downregulates 11β-HSD1 expression in adipose tissue in obese mice and in humans, mediating insulin sensitization. Diabetes. 2012 Apr;61(4):790-6.