IL6 and cystitis: In human bladder epithelial cells treated with IL1β, which is abundant in the bladder of rat model of cystitis and is known to induce IL6 and COX2 [12, 13], COX2 and IL6 expression were significantly increased (Fig 3D and 3E; each p < 0.001); however, pretreatment with RA for 1 h significantly suppressed the IL1β-induced increase in COX2 and IL6 expression (Fig 3D and 3E; p = 0.005 and p = 0.001, respectively).