Immunomodulatory tetracyclines shape the intestinal inflammatory response inducing mucosal healing and resolution.

BACKGROUND AND PURPOSE: 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. EXPERIMENTAL APPROACH: 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. KEY RESULTS: 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-1ß, 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. CONCLUSIONS AND IMPLICATIONS: Immunomodulatory tetracyclines potentiate protective immune pathways leading to mucosal healing and resolution, representing a promising drug reposition strategy for the treatment of intestinal inflammation.

Immunomodulatory tetracyclines ameliorate DNBS-colitis: Impact on microRNA expression and microbiota composition.

OBJECTIVE: The use of immunomodulatory antibiotics to simultaneously target different factors involved in intestinal inflammatory conditions is an interesting but understudied pharmacological strategy. A great therapeutic potential has been obtained with minocycline and doxycycline in experimental colitis. Therefore, understanding the contribution of the different activities of immunomodulatory tetracyclines is crucial for the improvement and translation of their use into clinic. DESIGN: A comparative pharmacological study including tetracyclines and other antibiotic or immunomodulatory drugs was performed in 2,4-dinitrobenzene sulfonic acid (DNBS)-induced colitis in mice. The correlation between the therapeutic efficacy of each drug and changes in the gut microbiota composition, markers of barrier integrity, inflammatory mediators, microRNAs and TLRs was analysed to identify the main mechanisms of action. RESULTS: Tetracyclines counteracted most of the markers found altered in DNBS-colitis, which differed from effects of corticosteroid treatment. Of note, administration of tetracyclines led to increased mucosal protection, associated with up-regulated expression of CCL2, miR-142 and miR-375. All drugs with antibiotic activity ameliorated the progression of inflammation and reduced neutrophil-related genes, such as miR-223, despite their effects were not associated with restored intestinal dysbiosis. However, reduced bacterial richness was correlated with increased expression of TLR2 and TLR9 in antibiotic-treated groups and TLR6 was also up-regulated by the immunomodulatory tetracyclines with higher efficacy (doxycycline, minocycline and tigecycline). CONCLUSION: The anti-inflammatory effect of tetracyclines involves specific modifications in TLR and microRNA expression leading to an improved microbial-derived signalling and mucosal protection. These results support the potential of immunomodulatory tetracyclines to prevent inflammation-associated tissue damage in acute intestinal inflammation.

Effect of aqueous and particulate silk fibroin in a rat model of experimental colitis.

Silk fibroin (SF) has anti-inflammatory properties and promotes wound healing. Moreover, SF particles act as carriers of active drugs against intestinal inflammation due to their capacity to deliver the compound to the damaged colonic tissue. The present work assesses the effect of SF in the trinitrobenzenesulfonic acid model of rat colitis that resembles human intestinal inflammation. SF (8mg/kg) was administered in aqueous solution orally and in two particulate formats by intrarectal route, following two technologies: spray drying to make microparticles and desolvation in organic solvent to produce nanoparticles. SF treatments ameliorated the colonic damage, reduced neutrophil infiltration and improved the compromised oxidative status of the colon. They also reduced the gene expression of pro-inflammatory cytokines like IL-1ß and the anti-inflammatory cytokine IL-10. Moreover, they improved the intestinal wall integrity by increasing the gene expression of some of its markers (villin, trefoil factor-3 and mucins), thus accelerating the healing. The immunomodulatory properties of SF particles were also tested in vitro in macrophages: they activated the immune response in basal conditions without increasing it after a pro-inflammatory insult. In conclusion, SF particles could be useful as carriers to deliver active drugs to the damaged intestinal colon with additional anti-inflammatory and healing properties.

Intestinal anti-inflammatory activity of calcium pyruvate in the TNBS model of rat colitis: Comparison with ethyl pyruvate.

Pyruvate is a key intermediate of the carbohydrate metabolism with endogenous scavenger properties. However, it cannot be used in clinics due to its instability. Ethyl pyruvate (EP) has shown better stability as well as an antioxidant and anti-inflammatory activity. Calcium pyruvate monohydrate (CPM) is another stable pyruvate derivative that could also provide the benefits from calcium, fundamental for bone health. Considering everything, we propose CPM as a therapeutic strategy to treat diseases with an immune component in which there is also a significant dysregulation of the skeletal homeostasis. This could be applicable to inflammatory bowel disease, which is characterized by over-production of pro-inflammatory mediators, including cytokines and reactive oxygen and nitrogen metabolites that induces intestinal mucosal damage and chronic inflammation, and extra-intestinal symptoms like osteopenia and osteoporosis. The effects of CPM and EP (20, 40 and 100mg/kg) were evaluated on the trinitrobenzenesulfonic acid (TNBS) model of colitis in rats, after a 7-day oral treatment, with main focus on colonic histology and inflammatory mediators. Both pyruvates showed intestinal anti-inflammatory effects in the TNBS-induced colitis. They were evident both histologically, with a recovery of the mucosal cytoarchitecture and a reduction of the neutrophil infiltration, and through the profile of inflammatory mediators (IL-1, IL-6, IL-17, IL-23, iNOS). However, CPM appeared to be more effective than ethyl pyruvate. In conclusion, CPM exerts intestinal anti-inflammatory effect on the TNBS-induced colitis in rats, although further experiments are needed to explore its beneficial effects on bone health and osteoporosis.