Anti-inflammatory Activity And Regulation On Inflammatiory Signal Transduction Pathway Of Florfenicol

It has been shown that some antibacterials modulate the inflammatory responses by directly affecting host cell function in addition to exerting their antibacterial activity. In particular, drugs that target protein synthesis or DNA replication processes in bacteria have been suspected of causing this effect. Florfenicol is a new type broad-spectrum antibacterial that is used in the veterinary clinic. It has been widely used to treat a broad array of infectious diseases, such as for the treatments of bovine and porcine respiratory tract infections, actinobacillus pleuropneumonia in pigs, endometritis and mastitisand in female livestocks. However, florfenicol is widely used only as antibacterial in veterinary clinic. In order to fully educe clinical value and expand applied scope of florfenicol, we built in vitro inflammatory model by LPS-stimulated murine RAW 264.7 macrophages, and further explored anti-inflammatory molecular mechanism of florfenicol by inflammatory signal transduction pathway. Meanwhile, we studied the effects of florfenicol on LPS-induced murine toxicemia and ALI.First, we investigated the effect of different concentrations of florfenicol on cytokine TNF-α, IL-1β, IL-6 and IL-10, inflammatory mediator NO and PGE2 secretions in LPS-stimulated murine RAW 264.7 macrophages. The result showed that florfenicol inhibited TNF-α, IL-6 and IL-1βsecretion and increased IL-10 level in a dose-dependent manner, but had no significant effect on IL-1βand IL-10. Florfenicol also inhibited NO and PGE2 synthesis, iNOS and COX-2 mRNA and protein expressions in a dose-dependent manner. These indicated florfenicol may educe anti-inflammatory effect through regulating the secretion of cytokines and inflammatory mediators in inflammatory process.The mechanism by which LPS induces the production of cytokines and inflammatory mediators has been intensively investigated. There are several well-characterised signalling pathways involved. Among these, the mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) pathways may play an essential role. NF-κB is one of the most ubiquitous transcription factors and regulates the genes involved in cellular proliferation, inflammatory responses, and cell adhesion. The other major extracellular signal transduction pathway stimulated by inflammatory mediators is the MAPK pathway. The MAPKs are a family that includes ERK, p38 and JNK. They participate in LPS-induced intracellular signaling transmission and cytobiological response. Therefore, NF-κB and MAPKs are known as important targets for anti-inflammatory molecular mechanism. In order to study anti-infalmmatory molecular mechanism, we further investigated the effect of florfenicol on NF-κB and MAPKs signal transduction pathways in LPS-stimulated murine RAW264.7 macrophages. The result showed that florfenicol inhibited NF-κB activity, p38 and ERK1/2 protein phosphorylation in a dose-dependent manner. It suggested that florfenicol inhibited cytokine TNF-α, IL-6, NO and PGE2 secretion by regulating both NF-κB and p38, ERK1/2 MAPKs pathways.To provide objective evaluation index on clinical therapeutic of florfenicol, we further studied in vivo ant-inflammatory of florfenicol. We investigated the effect of different concentrations of florfenicol on preventive and therapeutic effect in LPS-induced toxicemia mice, and the effect on cytokine TNF-α,IL-1β,IL-6 and IL-10 production in murine serum. The result showed that florfenicol significantly improved murine survival rate and decreased TNF-αand IL-6, increased IL-10 level in serum, but had little effect on IL-1β. It suggested that florfenicol improved murine survival rate through regulating the level of cytokines.LPS-toxicemia will further cause systemic inflammatory response syndrome (SIRS) and most common and severe ALI, and lungs are involved in and first attacted organ by LPS because of its physiological characteristic. Therefore, we also studied the protection of florfenicol on murine ALI by building LPS-induced ALI model. The result showed that flrofenicol inhibited W/D ratio of lung, protein concentration and cellular scores of BALF; florfenicol significantly inhibited TNF-α, IL-1βand IL-6 level of BALF in LPS-induced ALI mice; lung histopathology also showed that florfenicol had certain protection on inflammatory infiltration of ALI.We first time demonstrate that florfenicol has anti-inflammatory effect through regulating NF-κB, p38 and ERK1/2 MAPKs signal pathway in addition to exerting its antibacterial activity, it will provide foundation for reasonable application of florfenicol in clinic and improve clinical value, and it may be of importance as a therapeutics in treatment of excessive inflammatory reaction, SIRS and MODS in macrophages.