In vitro activity: Mesalamine inhibits the enzyme 3-hydroxysteroid dehydrogenase, involved in the reversible conversion between DHP and THP, and therefore may affect the local actions of DHP and THP in the brain. Mesalamine, an anti-inflammatory aminosalicylate, dose-dependently inhibits IL-1-stimulated NF-kappaB-dependent transcription without preventing IkappaB degradation or nuclear translocation and DNA binding of the transcriptionally active NF-kappaB proteins, RelA, c-Rel, or RelB. Mesalamine is found to inhibit IL-1-stimulated RelA phosphorylation. Mesalamine increases cell adhesion which is measured by cell adhesion assay and transcellular-resistance measurement. Mesalamine treatment restores membranous expression of adhesion molecules E-cadherin and β-catenin. Mesalamine or sulfasalazine (2 mM), but not sulfapyridine, significantly reduces the expression of the TC22 transcript and significantly reduces the expression of TC22 protein in a dose-dependent and reversible manner.

Kinase Assay: 5-Aminosalicylic acid (Mesalamine) acts as a specific PPARγ agonist and also inhibits p21-activated kinase 1 (PAK1) and NF-κB.

Cell Assay: Cytostatic effects are measured by MTT assay. HT-29 colon carcinoma cells are detached with a 0.25% trypsin solution for 5 min. Subsequently, the cells are seeded onto 96-well plates (1×106 cells/well), supplemented with 10% FCS and allowed to attach for 24 h before the addition of test compounds (5-Aminosalicylic acid 10, 50, 100, 500, and 1000 μM; Nimesulide; and their combination). Test compounds are diluted in serum-free culture medium. Then the cells are incubated in a medium or at different concentrations of drugs for 48 h, 20 μL of MTT solution (5 g/L) in PBS is added. Four hours later, the medium in each well is removed, and 120 μL of 0.04 mM muriatic isopropanol is added, slightly concussed for 10 min. Dye uptake is measured at 490 nm with an ELISA reader. Five wells are used for each concentration or as a control group. On the other hand, the cells are seeded onto 96-well plates (1×106 cells/well) and allowed to attach for 24 h, then treated with test compounds (5-Aminosalicylic acid, Nimesulide, and their combination). The final concentration is 100 μM. The same medium is added into the control group and dye uptake is then measured. Five wells are used for each test compound or control group.