Immunomodulatory tetracyclines are well‐characterized drugs with a pharmacological potential beyond their antibiotic properties. Specifically, minocycline and doxycycline have shown beneficial effects in experimental colitis, although pro‐inflammatory actions have also been described in macrophages. Therefore, we aimed to characterize the mechanism behind their effect in acute intestinal inflammation.

A comparative pharmacological study was initially used to elucidate the most relevant actions of immunomodulatory tetracyclines: doxycycline, minocycline and tigecycline; other antibiotic or immunomodulatory drugs were assessed in bone marrow‐derived macrophages and in dextran sodium sulfate (DSS)‐induced mouse colitis, where different barrier markers, inflammatory mediators, microRNAs, TLRs, and the gut microbiota composition were evaluated. The sequential immune events that mediate the intestinal anti‐inflammatory effect of minocycline in DSS‐colitis were then characterized.

Novel immunomodulatory activity of tetracyclines was identifed; they potentiated the innate immune response and enhanced resolution of inflammation. This is also the first report describing the intestinal anti‐inflammatory effect of tigecycline. A minor therapeutic benefit seems to derive from their antibiotic properties. Conversely, immunomodulatory tetracyclines potentiated macrophage cytokine release in vitro, and while improving mucosal recovery in colitic mice, they up‐regulated Ccl2, miR‐142, miR‐375 and Tlr4. In particular, minocycline initially enhanced IL‐1β, IL‐6, IL‐22, GM‐CSF and IL‐4 colonic production and monocyte recruitment to the intestine, subsequently increasing Ly6C⁻MHCII⁺ macrophages, Tregs and type 2 intestinal immune responses.

Immunomodulatory tetracyclines potentiate protective immune pathways leading to mucosal healing and resolution, representing a promising drug reposition strategy for the treatment of intestinal inflammation.