Discordant Effects of Janus Kinase Inhibition Ex Vivo on Inflammatory Responses in Colonic Compared to Ileal Mucosa

Background and Aims: Janus kinase [JAK] inhibitors are used for treating inflammatory bowel diseases [IBD]. We aimed to identify the molecular effects of JAK inhibition in human intestinal mucosa, considering IBD location and phenotype. Methods: Colonic and ileal explants from patients with ulcerative colitis [UC], Crohn’s disease [CD], and non-IBD controls [NC] were assessed for levels of phosphorylated signal transducers and activators of transcription [p-STAT] and expression of inflammatory genes in response to an ex vivo JAK inhibitor [tofacitinib]. Cytokine production by lamina propria lymphocytes in response to tofacitinib was assessed. Human intestinal organoids were used to investigate the effects of JAK inhibitors on inducible nitric oxide synthase [iNOS] expression. Results: Explants were collected from 68 patients [UC = 20, CD = 20, NC = 28]. p-STAT1/3/5 inhibition rates varied, being higher in colonic compared to ileal explants. p-STAT1/3 inhibition rates negatively correlated with levels of C-reactive protein [CRP]. While significant alterations in 120 of 255 inflammatory genes were observed in colonic explants, only 30 were observed in ileal NC explants. In colonic explants from UC, significant alterations were observed in five genes, including NOS2. JAK inhibition significantly decreased Th1/Th2/Th17-related cytokine production from lamina propria lymphocytes. Various JAK inhibitors reduced the interferon-γ-induced increase in iNOS expression in organoids. Conclusions: A site-specific anti-inflammatory effect of JAK inhibition by tofacitinib was noted, whereby the colon was more robustly affected than the ileum. The ex vivo response to tofacitinib is individual. JAK inhibition may attenuate inflammation by decreasing iNOS expression. Ex vivo mucosal platforms may be a valuable resource for studying personalized drug effects in patients with IBD.