Tofacitinib downregulates JAK1 and JAK3 on human intestinal monocytes and macrophages without affecting dendritic...

Ulcerative colitis (UC) is an inflammatory disorder of the gastrointestinal tract. Although Tofacitinib, which inhibits the JAK1 and JAK3 signalling pathway, is approved to treat patients with UC, its specific mechanism of action remain elusive. Given the central role that conventional dendritic cells (cDC) elicit in gut homeostasis, we hypothesised that Tofacitinib acts modulating cDC function in UC.

Human biopsies were obtained from colon of controls, and patients with UC (active and quiescent). Lamina propria mononuclear cells (LPMC) were ex-vivo cultured in the presence/absence of Tofacitinib. The specific effect elicited over human intestinal cDC, monocytes and macrophages was assessed by flow cytometry. cDC were also enriched following Tofacitinib conditioning in order to assess its effect over naïve T-cells.

Several human intestinal cDC, monocyte and macrophage subsets can be found in the human colon, with these cells being more similar between controls and patients with qUC referred to patients with aUC. Following ex-vivo culture, Tofacitinib downregulated JAK1 expression on intestinal monocytes from patients with both active and quiescent UC. As for macrophages, JAK1 was decreased on patients with active UC while JAK was downregulated on macrophages from patients with quiescent disease. Tofacitinib did not modulate the phenotype or function of human intestinal cDC.

Tofacitinib does not modulate the phenotype and function of human intestinal cDC in UC. On the contrary, it displays a differential capacity to modulate intestinal monocyte and macrophage phenotype. Future studies should address whether it also translates into a differential function of these cells.