Sessions

Chronic gastrointestinal diseases in dogs are multifactorial. Oxidative stress, imbalance of the intestinal microbiota and aberrant, sustained activation of the immune system play a decisive role in their pathogenesis. As a consequence of these processes damage to the mucosal barrier promotes the translocation of bacterial components and bacteria. E. coli is a Gram-negative bacterium that forms a part of the normal canine gut microbiota, however under pathological conditions it can play a pathogenic role and in severe cases it can cause sepsis. Flavonoids are polyphenolic compounds with extensive biological activity. Owing to their outstanding antioxidant and immunomodulatory properties they are able to reduce the formation of reactive oxygen species (ROS) and inhibit the activation of NF-κB and MAPK signaling pathways. Consequently, the presence of flavonoids reduces the release of tumor necrosis factor-alpha (TNF-α), intracellular ROS production and mitigates the clinical manifestations of chronic inflammation.

In our study we modeled the systemic immune system with canine primary peripheral blood mononuclear cell (PBMC) cultures and induced inflammatory conditions in the cell cultures using canine-derived E. coli strains. We examined the effects of three different bacterial strains under various treatments and incubation times, then selected the treatment type that caused significant oxidative stress and inflammation. This was the E. coli strain 863, whose growth was inhibited with enrofloxacin and incubated for 24 hours. In the established inflammatory model we examined the anti-inflammatory and immunomodulatory effects of the flavonoids quercetin, luteolin, and grape seed proanthocyanidins at two concentrations (25 and 50 μg/ml). Measurements included the determination of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values of the flavonoids in the E. coli strains, as well as intracellular ROS and TNF-α levels.

Based on our results the antibacterial activity of flavonoids was limited, however they significantly reduced intracellular ROS production and TNF-α release compared to the bacteria-treated controls. These results support the conclusion that the biological effects of flavonoids, particularly their antioxidant and anti-inflammatory activities may provide potential adjuvant therapeutic value in the management of chronic gastrointestinal diseases in dogs, especially by modulating oxidative stress and inflammation induced by bacterial translocation. Further studies are required to confirm their systemic effects in vivo.