CLDN5 and inflammatory bowel disease: While results for claudin-5 corroborate the previously assessed role of pioglitazone on TNFα-activated BBB, the lack of effect on permeability seemingly contradicts such results, but even if plasma from the patients being more severely affected by IBD was used, permeability increases were not higher than 10%, an effect likely not pronounced enough for pioglitazone actions to be detected.